Exam 2 SG PDF

Exam 2 SG Gram-Negative Cocci (Neisseria) I. Gram-Negative Cocci (Neisseria) 2 species of Neisseria N. Meningitis causes meningitis and/or meningococcemia In the U.S., leading cause of death from infection in childre...

Exam 2 SG Gram-Negative Cocci (Neisseria) I. Gram-Negative Cocci (Neisseria) 2 species of Neisseria N. Meningitis causes meningitis and/or meningococcemia In the U.S., leading cause of death from infection in children N. Gonorrhoeae causes gonorrhea and neonatal conjunctivitis, pelvic in ammatory disease Both Species: Gram negative, so they have an outer membrane, thin peptidoglycan wall, and periplasmic space Possess the enzyme cytochrome C, oxidase-positive inlay diagnostic test (anerobic respiration) N. Meningitis has polysaccharide capsule and lipopolysaccharide (LPS) in the outer membrane but N. Gonorrhea have lipooligosaccharide (LOS, lacking or shorter O antigen than LPS); but LOS still is an endotoxin that can be involved in shock A. N. meningitidis (meningococcus) 1. Virulence Factors a) Polysaccharide capsule (1) Antiphagocytic virulence factor (2) Antigenic: > 13 serotypes (a) Serotype A dominates worldwide (b) Serotype B accounts for most disease in U.S. (c) Antibody = resistance (some people are carriers, not symptomatic); but only to one antigenic group (so could be infected by another serotype) b) Endotoxin: shock, fever of meningococcemia c) IgA protease suppresses immune defense 2. Pathogenesis a) Humans are only natural host b) Transmitted by respiratory droplets, favored by close contact c) Infects nasopharynx, moves to circulation; from there to meninges or joints. Bacteremia can seed many organs d) Some people become carriers: 5% generally, but up to 35% in close quarters (barracks, dorms); thus epidemics occur in those situations (army, students) e) Group A most likely to cause epidemics f) Bacterial meningitis is caused mostly (80%) by: (1) S. Pneumoniae (in adults) (2) N. Meningitidis (higher among young people, and in Africa & Latin America) Page 1 fl  Exam 2 SG Gram-Negative Cocci (Neisseria) 3. Clinical Findings a) Meningococcemia and meningitis b) Waterhouse-Friderichsen syndrome Is the most severe form: high fever, shock, purpura, intravascular coagulation, thrombocytopenia, adrenal insu ciency c) Symptoms of meningitis: fever, headache, sti neck (clinically), photophobia, increased PMNs in spinal uid. Can become life-threatening very rapidly ( cells/L in drinking water is considered unacceptable Drug Resistance Many gram negative enteric rods are highly antibiotic resistant Frequent conjugation among them (including interspecies); passes on multi-drug resistance cassettes on R plasmids Pathogens INSIDE the Enteric Tract A. Shigella Causes enterocolitis (shigellosis, or “bacillary dysentery” when caused by Shigella) With Campylobacter and Salmonella, most common Gram negative GI pathogens Grouped (A, B, C, or D) based on O-antigen (slide agglutination test) 1. Pathology and Transmission 1. Very low infectious dose (ID50): < 100 cells will cause disease 2. Disease in humans only (no animal reservoir) 3. No prolonged “carrier state” in humans (contrast Salmonella) 4. Transmission is fecal-oral 1. Acquired from “ ngers, ied, food, feces” (typical in day care and mental health centers) 5. Pathogenesis is primarily by invasion of the gut wall 1. Shiga toxin is an endotoxin produced by some strains (phage-transduced); toxin is similar to that produced by EHEC (enterohemorrhagic E. Coli) 2. Clinical Findings 1. Incubates 1-4 days; then fever, cramps, bloody diarrhea 2. Mild form: S. sonnei (75% of Shigella in U.S.) 3. Severe form: S. Dysenteriae 4. More severe in young children and elderly Page 4 fl fi fl  Exam 2 SG Gram-Negative Rods (Enteric) 3. Prevention and Treatment 1. Prevent with good hygiene (food workers), chlorinated water, good sewerage control 2. Treat with uid, electrolytes; if severe Cipro or Bactrim (but resistance requires testing rst) B. Campylobacter Morphology: along with Helicobacter and Vibrio, are curved rods Are microaerophiles and capnophiles C. Jejuni causes enterocolitis, especially in children; signi cant causes of diarrhea/ dysentery in U.S. (with shigella and salmonella, most common gram negative GI pathogens) C. Jejuni is common precursor to Guillain-Barre Syndrome, an autoimmune disease caused by cross-reaction of antibodies to the bacterium. Ascending paralysis of peripheral nerves Guillain-Barre Syndrome: the most common cause of acute neuromuscular paralysis C. intestinalis causes bacteremia (rare; neonates and elderly) 1. Pathology and Transmission a) Transmission is fecal-oral from domestic animals (cattle, chicken, dogs) (1) Typically food (meat, milk) and water contaminated by animal feces and undercooked (2) Children acquire from puppies b) Pathogenesis is by in ammation/invasion of the gut (colitis) 2. Clinical Findings a) Causes a “food infection,” not “food poisoning” b) Colitis: watery diarrhea, then bloody stools; fever, severe abdominal pain c) Bacteremia: fever, malaise 3. Prevention and Treatment a) Prevent with good hygiene, chlorinated water, good sewerage control b) Treatment: (1) Colitis: cipro, erythromycin (2) Bacteremia: an aminoglycoside Page 5 fi fl fl fi  Exam 2 SG Gram-Negative Rods (Enteric) C. Helicobacter H. Pylori is a pathogen of the stomach, causing gastritis and peptic ulcers Risk factors for gastric carcinoma and MALT lymphomas (mucosa-associated lymphoid tissue) Morphology: along with Campylobacter and Vibrio, are curved rods Similar to Campylobacter, but are urease-positive (critical VF) 1. Pathogenesis a) Attaches to mucus-producing cells of gastric mucosa, induced in ammation b) Produces urease: cleaves urea, makes ammonia — which (1) Neutralizes stomach acid (allows bacterium to survive) (2) Damages mucosa, causing gastritis and ulcer c) MALT lymphomas: in ammation randomly stimulates B cell proliferation (B cell lymphoma) 2. Epidemiology a) Uncertain, probably ingested or transmitted person to person (familial clustering) 3. Clinical Findings a) Recurrent pain in upper abdomen b) Bleeding into GI tract; no bacteremia 4. Lab Diagnosis a) Can be seen by Gram stain of gastric biopsy b) Urease positive on plating; in urea breath test, ingested radio labeled urea is cleaved by urease, patient exhales radioactive CO2 c) Bacterial antigens in stool, antibodies in serum 5. Treatment a) No vaccine, combination of 2 antibiotics (b/c of resistance) + acid reducer b) Recognition of bacterial involvement in ulcers is historically recent D. Vibrio V. Cholerae is the cause of cholera (and the primary Vibrio pathogen) Morphology: along with Helicobacter and Campylobacter, are curved rods 1. Classi cation and Epidemics a) Grouped by O-antigen: O1 and (in 1992) O139 are epidemic strains; other sporadic or non-pathogenic b) 3 O1 serotypes: Ogawa (primary one), Inaba, Hikojima c) 2 biotypes of each serotypes: “classical” cholerae and “El Tor.” Biotype de ned biochemically (1) The El Tor biotype has a much higher carrier-to-case ration than the classical type (harder to control spread) 2. Transmission a) V. Cholerae is transmitted by fecal contamination of water and food b) The animal reservoir is marine shell sh (transmitted if eaten undercooked) c) Control is hindered by asymptomatic carriers Page 6 fi fl fi fl fi  Exam 2 SG Gram-Negative Rods (Enteric) 3. Pathogenesis and Clinical Findings a) V. Cholerae has a high ID50 b/c it is sensitive to stomach acid (antacids predispose) b) Must rst adhere to cells of SI and colonize (limiting step) c) Secretes enterotoxin called choleragen or cholera toxin; presence of toxin is su cient to cause symptoms (1) Thus, V. Cholerae is toxigenic; presence of bacterium is not directly required for disease (2) Toxin has 2 subunits: “B” binds to receptors; “A” is ADP-ribosylase that stimulates adenylate cyclase, causes loss of water and ions from cells of the but (3) Carried on “CTX” phage d) “Rice Water” diarrhea is the classic symptom; no abdominal pain or bleeding (1) Rapid loss of uids and electrolytes (up to 1 liter/hour) (2) Treated, resolves in 7 days; untreated, leads to cardiac and renal failure (40% mortality) (3) No lab diagnosis during epidemic; carriers can be analyzed by special lab tests 4. Treatment a) Prompt oral or IV solution of water, electrolytes, and glucose 5. Prevention a) Maintaining clean water and food (and cooking shell sh); spread controlled by identifying carriers. Vaccines exists but are not very e ective 6. 2 other species: both are Marin organisms a) V. parahaemolyticus (1) Acquired from raw or undercooked seafood; prevalent in Japan, uncommon in U.S. (2) Self-limiting disease: diarrhea, vomiting, cramps, fevers b) V. Vulni cus (1) Causes cellulitis (seafood handlers) (2) Can cause fatal septicemia in immunocompromised patients who eat raw shell sh, or in people with chronic liver disease (e.g. cirrhosis) (3) Treat with doxycycline Page 7 ffi fi fi fi fl fi ff Exam 2 SG Gram-Negative Rods (Enteric) Pathogens INSIDE & OUTSIDE the Enteric Tract E. Salmonella Inside the enteric tract, causes enterocolitis With Campylobacter and Shigella, most common Gram negative GI pathogens Outside the enteric tract, causes typhoid fever (one of several “enteric fevers”) and septicemia with “metastatic” (spreading but focal) infection 1. Antigens and Classi cation a) O antigens: 9 groups (A to I), cell wall b) H antigens: Phase 1 & 2, alterante in expression c) Vi antigen: the capsular antigen, antiphagocytic virulence factor used to serotype S. typhi d) Note also: Salmonella does not ferment lactose — used to distinguish from E. coli 2. Naming Convention a) Practically: serotype/species and clinical category (typhoidal, non-typhoidal) are most important 3. Clinical Category a) Typhoidal (typhoid/enteric fevers): S. typhi and paratyhpi. Humans and higher primates only. Transmitted from carrier by excretion (fecal-oral) b) Non-typhoidal: animals and humans. Transmitted from feces, animals (reptiles, dogs), poultry, eggs, undercooked meat, milk, melons (2012 cantaloupe incident) (1) Enterocolitis: S. enteriditis and typhimurium (2) Septicemia/metastatic infections: S. choleraesuis 4. Pathogenesis a) Enterocolitis (1) Caused by invasion of intestinal wall (but contained by immune response, so no bacteremia); results in diarrhea, in ammation (2) Like cholera, bugs are acid-sensitive with high ID50 b) Typhoid/Enteric Fevers (1) Begins in SI, hence “enteric;” but few GI symptoms (2) Speeds inside the phagocytes of the MALT (Peyer’s patches) and other organs (3) Ability to live inside phagosomes mediated by one form of the the Type III secretion system, another VF (4) Likes the gall bladder; excreted in bile (thus in feces) by asymptomatic carriers (5) Symptoms of disease: fever from bacteremia c) Septicemia, Metastatic Infections (1) Small proportion (5-10%) of infections (2) Happens in children with enterocolitis, patients with chronic disease (sick cell, cancer) (3) Bacteremia seeds organs: osteomyelitis, pneumonia, meningitis (4) Other damaged tissues subject to abscesses Page 8 fi fl  Exam 2 SG Gram-Negative Rods (Enteric) 5. Clinical Findings & Treatment a) Enterocolitis (1) 12-48 hours incubation, then nausea, vomiting, abdominal pain, diarrhea +/- blood (2) Self limiting: antibiotics not helpful except in neonates, chronically ill. give uids, electrolytes. (3) HIV patients have more and worse infections (4) S. Typhimurium most common cause b) Typhoid/Enteric Fevers (1) Slow onset with fever, constipation, possibly a limited diarrhea (2) High fever, delirium, tender abdomen, enlarged spleen come with bacteremia (3) Rose spots (rarely) (4) Leukopenia, anemia (5) Resolves in 3 weeks, but can lead to intestinal hemorrhaging, perforation; 3% becomes carriers (6) Ceftriaxone and Cipro; carriers get Cipro, ampicillin (7) S. Typhi and S. Parathyphi A, B, and C c) Septicemia, Metastatic Infections (1) Fever + symptoms associated with the local infection. S. Choleraesuis 6. Lab Diagnosis a) DO NOT ferement lactose (vs. E. Coli) b) Enterocolitis: isolate from stool c) Enteric/typhoid form blood and possibly bone marrow 7. Prevention a) Good hygiene (food workers) b) Cooking, pasteurization c) Manage sewerage, chlorinate water d) Vaccines against S. Typhi are 50-80% e ective, recommended for travelers to high-risk areas or in relevant occupations Page 9 fl ff Exam 2 SG Gram-Negative Rods (Enteric) F. Escherichia (E. Coli) Inside the enteric tract: causes travelers (ETEC) or infants diarrhea (EPEC) or dysentery (EIEC, EHEC) ETEC: enterotoxigenic E. coli EPEC: enteropathogenic E. Coli EIEC: enteroinvasive E. Coli EHEC: enterohemorrhagic E. Coli Outside the enteric tract: causes urinary tract infections, and neonatal meningitis and sepsis E. Coli: Is a straight, gram-negative rod Ferments lactose (unlike Salmonella and Shigella) Is a facultative anaerobe (the most abundant one in the colon and feces) Comes in > 1000 serotypes based on combination of O, H, and K antigens Resides in both humans and animals 1. Sources of Infection Infection Source Traveler’s Diarrhea Food, water contaminated w/ human feces Dysentery Undercooked meat Urinary Tract Infection Colon Neonatal Meningits/Sepsis Birth canal 2. Pathogenesis and Clinical a) Pathogenic factors (1) Pili, capsule, endotoxin (LPS) (2) 3 possible Enterotoxins: (a) LT and ST both cause water and electrolyte loss (increases cAMP and gGMP) (b) Shiga toxin (Stx) blocks protein synthesis, kills cells, inhibits uid uptake. If Shiga enters the bloodstream, hemolytic-uremic syndrome (HUS) can result. Hemolytic anemia, thrombocytopenia, renal failure b) Systemic (sepsis and neonatal meningitis) (1) Vaginal E. Coli cause bacteremia and meningitis in newborn (along with Group B Strep) (2) The antiphagocytic capsule facilitates systemic disease; the K1 serotype is involved in neonatal meningitis (3) Endotoxin causes fever, hypotension, intravascular coagulation (4) E. Coli also causes hospital-acquired sepsis in adults Page 10 fl  Exam 2 SG Gram-Negative Rods (Enteric) c) Urinary Tract (1) E. Coli most frequent cause of community-acquired UTIs, mostly in women. Contamination of urogenital tract from colon causes urethritis; may ascend to cause cystitis (bladder), pyelonephritis (kidney), and possibly bacteremia. Motility ( agella) contributes (2) Hospital-acquired UTIs associated with catheters; men=women (3) Uropathic strains have pili with adhesions that are speci c for urinary epithelium; certain O serogroups carry them (4) Cystitis causes frequent/painful urination; pyelonephritis: fever, chills, ank pain 3. Lab Diagnosis a) Begins with lactose fermentation and EMB plating 4. Prevention a) Mostly a matter of avoiding sources and cooking meat (EHEC); antibiotic prophylaxis may be useful against traveler’s diarrhea (doxycycline, Cipro, or Bactrim) 5. Treatment a) Diarrhea: avoid antibiotics in children with EHEC (can lead to HUS); rehydrate b) UTI: oral bactrim, ampicillin c) Sepsis: parenteral (outside of the GI tract) antibiotic (cephalosporin) d) Neonatal meningitis: combination of ampicillin and cefotaxime Pathogens OUTSIDE the Enteric Tract G. Proteus-Providencia-Morganella Group 1. Species a) Proteus mirabilis and proteus vulgaris b) Providencia (formerly proteus) rettgeri c) Morganella (formerly proteus) morganii d) All cause CA and HA urinary tract infections. May also cause pneumonia, wound infections, septicemia. Found in colon, soil, and water 2. Identi cation and Pathogenesis a) Swarming motility on plates. Motility contributes to infection b) Produce phenylalanine deaminase c) Produce urease, which generates ammonia from urea and raises pH of urethra (thus is a virulence factor). Alkaline pH also causes formation of urethral stones (struvite), which cause blockages, damages, and a reservoir for recurrent infections d) O antigens are similar to antigens of some Rickettsiae; antibodies cross-react 3. Prevention and Treatment a) Remove catheters as soon as possible, keeping the urine at a low pH b) Antibiotics: choice depends on sensitivity. Aminoglycoside, Bactrim, Ampicillin, Cephalosporin, resistant to multiple antibiotics Page 11 fl fi fl fi Exam 2 SG Gram-Negative Rods (Enteric) H. Klebsiella-Enterobacter-Serratia Group 1. Species a) Klebsiella pneumonia b) Enterobacter cloacae c) Serrate marcescens d) All cause urinary tract infections and pneumonia. K. Pneumonia also causes community-acquired respiratory infections e) Reside in: colon primarily; also soil, water f) K. pneumonia: hugh polysaccharide capsule —> mucoid colonies g) S. marcescens: red pigmentation 2. Pathogenesis and Epidemiology a) Enterobacter and Serratia: catheter (urinary, IV); respiratory intubation b) Serratia: contaminated water in respiratory devices; endocarditis in IV drug users c) Klebsiella: can be primary pathogen, but tends to infect those predisposed by age or disease (1) Klebsiella pneumonia produces a characteristics thick, bloody sputum, can progress to necrosis and abscesses d) Baacteremia can occur, cause meningitis or hepatitis 3. Prevention and Treatment a) Remove catheters; keep respiratory devices clean b) Antibiotics: choice depends on sensitivity (b/c antibiotic resistance, empirically a gentamicin and a cephalosporin). Combination (imipenem and gentamicin for Enterobacter) often required 4. Lab Diagnosis a) Begins with lactose fermentation (lactose fermenters), MacConkey’s or EMB plating (colored) I. Bacteroids & Prevotella 1. Species — all are endogenous a) B. fragilis: predominant bacteria in the colon. Often in vagina also b) B. Corrodens: oral c) P. Melaninogenica: oral (black colonies on blood agar) d) All are obligate anaerobes. B. Fragilis is the most common cause of serious anaerobic infections 2. Pathogenesis and Clinical Findings a) Endogenous macrobiotia that infect via mucosal breaks: surgery, trauma, chronic disease b) Anaerobic conditions allow growth: necrosis, reduced blood supply; often occur as mixed infections with facultative anaerobes like E. Coli c) Secreted enzymes damage tissue Page 12 Exam 2 SG Gram-Negative Rods (Enteric) d) B. fragilis (1) Intra-abdominal, usually below diaphragm: peritonitis, localized abscesses (pelvis, lung); also bacteremia (2) Capsule is important VF: host immune response contributes to abscess formation (3) Endotoxin is less active than others (variant Lipid A mission one of the fatty acids) e) Prevotella (1) Usually above diaphragm. Abscesses of mouth, pharynx, brain, lung 3. Prevention a) Perioperative cephalosporin 4. Treatment a) Surgical drainage of abscesses b) Combination of antibiotics to treat facultative anaerobes as well c) B. Fragilis is highly antibiotic resistant ( beta lactamase, etc., the predominant organisms in the human colon) d) Metronidazole preferred J. Pseudomonas 1. Species a) Mostly P. Aeruginosa b) Minor species also classi ed as Burkholderia c) Found in soil, water, on moist skin, sometimes colonic d) Causes variety of disease associated with weakened immunity and low neutrophil counts; major nosocomial pathogen (1) UTI (indwelling catheters) (2) Pneumonia in cystic brosis patients and those on ventilators (3) Cellulitis and wound infections in burn patients (4) Skin lesions including: malignant otitis external in diabetics; necrotic ecthyma gangrenosum; hot tub folliculitis (5) Osteochondritis in foot punctures (6) Corneal infections in contact lens users (7) GI tract infections in children & cancer patients; CNS infections (8) Sepsis is 50% lethal; systemic infections result (CNS, endocarditis, bone & joint) Page 13 fi fi  Exam 2 SG Gram-Negative Rods (Enteric) e) Properties (1) Obligate aerobes (thus oxidase positive and non-fermenters of glucose, except P. Aeruginosa) (2) Grow in plain water with very little nutrition. Easily contaminates water supplies, ventilators, IV uids, anesthesia equipment (3) Resistant to antiseptics, disinfectants, detergents, & antibiotics (4) Synthesizes two pigments: (a) Blue pyocyanin (damage the cilia) (b) Yellow-green pyoverdin ( uoresces under the UV) (c) Both useful in lab and detection of infection (5) Respiratory strains have prominent glycocalyx, mucoid colonies f) Pathogenesis (1) Endotoxin (sepsis) (2) Endotoxin A (necrosis): interferes with EF2 (protein synthesis), like diphteria toxin (3) Enzymes facilitate invasion of bloodstream (likes to invade blood vessel walls) (4) Type III secretion system “injects” exotoxins directly into cells (like salmonella); some strains only g) Lab Diagnosis (1) Non-fermentation of glucose, lactose (2) Oxidase positive (3) Pigmentation (4) Fruity aroma h) Prevention (1) Special care of patients with reduced immunity (2) Keep neutrophil counts up (removing indwelling catheters promptly, special care of burned skin) i) Treatment (dual and empirical choice of antibiotics) (1) Organism is highly antibiotic resistant; must treat sensitivity (2) Antipseudomonal penicillin + aminoglycoside (3) Polymyxin E (4) Cipro oxacin for UTIs Page 14 fl fl fl Exam 2 SG Gram-Negative Rods (Non-Enteric) III. Gram-Negative Rods (Non-Enteric) All: gram negative with LPS, aerobic or facultative Respiratory: Haemophilus Bordetella Legionella Animal Source: Zoonotic (mainly cause disease in animals, humans accidental hosts)* Brucella Francisella Pasteurella Primary pathology in humans Yersinia Bartonella *Zoonotic may be more broadly de nes as any disease transferrable between animals and humans A. Haemophilus in uenza 1. Properties a) “Coccobacillus:” short rods, easy to mistake for cocci. Facultative aerobe b) May have or lack an antigenic polysaccharide capsule (1) Encapsulated from cause worse, invasive disease (bacteremia, meningitis); esp. Type b (2) Encapsulated forms cannot be serotyped, but still cause disease, esp pneumonia c) Pathogenesis due to capsule, endotoxin; no exotoxins made d) Makes IgA protease 2. Disease a) Upper respiratory: otitis media, sinusitis; also conjunctivitis b) Pneumonia c) Meningitis in children: now rare in U.S. b/c of vaccine d) Epiglottis (rare but dangerous) e) Sepsis, septic arthritis f) Infect humans only; normal URT microbe; respiratory droplet transmission g) Infects children, 6 months — 6 years old; peak at 6-12 months, during transition from maternal to child’s antibodies 3. Clinical a) Sinusitis, otitis media: (1) Pain, redness with balding eardrum (2) #2 cause after S. Pneumonia b) Splenectomized patients susceptible to sepsis c) Epiglottis: swollen, red epiglottis can obstruct airway Page 15 fl fi  Exam 2 SG Gram-Negative Rods (Non-Enteric) 4. Diagnosis a) Gram stain cultures from normally sterile site; immunology I.D. of capsular antigens by latex agglutination test, uorescent-antibody staining, swelling by quelling reaction 5. Treatment a) Meningitis: prompt antibiotic by ceftriaxone. Untreated is 95% lethal. Survivors may sustain neurological damage, especially deafness b) URTs: amoxicillin-clavulanate or Bactrim 6. Prevention a) Conjugated vaccine (capsular Ag) is very e ective in children b) Given at 2-15 months; “Hib” vaccine c) Rifampin for people in contact with infected patients B. Bordetella Pertussis (whooping cough) 1. Transmission & Epidemiology a) Infects humans only; respiratory droplet transmission; extremely contagious b) Infects mostly children, but can occur in adults. Adults with reduced immunity are reservoir for children 2. Properties a) Coccobacillus, encapsulated b) Aerobic c) Attaches to (pili) and kills ciliated airway cells; interferes with ow of mucus 3. Pathogenesis a) Pertussis toxin causes a rise in cAMP in airway epithelial cells (1) Results is inhibition of chemotaxis of lymphocytes to lymphoid tissue; thus increase in circulating lymphocytes (lymphocytosis) b) Adenylate cyclase is secreted; inhibits phagocytes c) Tracheal cytotoxin, along with endotoxin, kills epithelial cells 4. 3 Stages of Pertussis: Catarrhal, Paroxysmal, and Convalescent 1-2 weeks 2-4 weeks Several weeks Catarrhal Paroxysmal Convalescent Malaise, fever, Worst cough, Cough improves cough, contagious leukocytosis Secondary complications possible a) Patients experience multiple paroxysms of coughs, followed by an inhalation of breath that sounds like a “whoop.” Infants need supportive care (oxygen therapy, suction of mucus) b) Azithromycin reduces the duration and severity of illness. Rapid diagnosis (PCR and direct uorescent antibody staining of the nasopharyngeal specimens) should be used if available 5. Vaccines a) DTaP contains 5 B. Pertussis antigens, rather than killed cells b) Given at 2 months; boosters at 12-15 months and 5 years. Boosters (Tdap) also recommended for teens and adults Page 16 fl fl ff fl Exam 2 SG Gram-Negative Rods (Non-Enteric) C. Legionella Pneumophila 1. Properties & Transmission a) Intracellular parasites: live in amoebas in nature; in macrophages during infections b) Anerobic. The main VF is lipopolysaccharide (endotoxin) c) Lives where water collect, and in soil; becomes airborne in the wind (or ventilation system). Tolerate chlorine d) Acquired by inhalation of aerosols; not transmitted person to person (humans are dead-end hosts) e) Alveolar macrophages consume for defense; Legionella multiplies within them 2. Disease (2 types) a) Legionnaire’s disease: an “atypical” pneumonia (insidious onset, scant sputum, X-ray abnormalities greater than expected based on signs (1) Immunocompromised patients are susceptible (cell mediated immunity is important) (2) Typical patients are older male, smoker, alcohol consumer. Risk factors include diabetes, kidney disease (3) Bacteremia can occur, damaging brain and kidneys (4) Diagnosis (a) Urinary antigen test + culture of organisms (5) Treatment (a) Azithromycin or erythromycin b) Pontiac Fever: in uenza-like illness in healthy individuals. Spontaneous recovery D. Brucella (Brucellosis = undulant fever) 1. Properties a) Coccobacillus that lacks a capsule. aerobic; LPS is main VF b) Intracellular in macrophages: thus localize to reticuloendothelial system (lymph nodes, liver, spleen, bone marrow = connective tissue macrophages) 2. Transmission a) Unpasteurized dairy products, especially form Mexico, Mediterranean b) Direct contact with infected animal tissue c) Portal of Entry: (1) Wounds in skin, mucous membranes (2) GI tract (3) Inhalation: considered weaponizable. Low ID50 3. Clinical a) 1-3 weeks incubation b) Fever, malaise, chills, fatigue, anorexia c) Foul-smelling sweat is a classical sign d) Undulating fever: enlarged lymph nodes, liver, spleen; possible osteomyelitis; < 2% fatal, due to endocarditis e) Occupational risk: slaughterhouses, meat packer, veterinarians, lab worker, hunters, ranchers Page 17 fl Exam 2 SG Gram-Negative Rods (Non-Enteric) 4. Lab Diagnosis a) Culture organisms; slide agglutination, ELISA, PCR 5. Prevention a) Pasteurize milk, immunize animals 6. Treatment a) Doxycycline + rifampin, prolonged E. Francisella Tularensis (Tularemia “rabbit fever”) 1. Properties a) Small rod, 2 biotypes (A & B, A dominates U.S.) b) Facultative anaerobes c) Intracellular in macrophages: thus localizes to reticuloendothelial system 2. Transmission & Pathogenesis a) Infects many wild animal species (esp. rabbits, deer, rodents), wide distribution b) Most common chain: ticks → rabbits → humans (dead end host) c) Ticks, lice, mites, biting ies can all be vectors d) Also skin contact while dressing animals, or inhaled (happens easily in labs) e) Extremely low ID50, (10 organisms); weaponizable f) Occupation hazard: veterinarians, hunters, livestock workers, meat handlers 3. Clinical (form depends on strain, portal of entry, immunity) a) Most commonly: ulcerations at site of entry, swollen lymph nodes b) Cause necrotic lesions when the bacteria is introduced into esh (reminiscent of gangrenous infection) c) Flulike symptoms: pneumonic, CNS, GI pathologies possible; can kill d) Risk low in the U.S. (200 cases in 2013, mostly rural AR, MO, OK) 4. Lab Diagnosis a) Cultures not usually done, slide agglutination, uorescent microscopy 5. Prevention & Treatment a) Avoid ticks, animal contact; liver bacterial vaccine (1 of only 2 approved) for outdoorsmen b) Doxycycline, streptomycin or gentamicin, plus tetracycline Page 18 fl fl fl  Exam 2 SG Gram-Negative Rods (Non-Enteric) F. Pasteurella Multocida 1. Properties a) Short coccobacillus, bipolar staining 2. Transmission & Pathogenesis a) Most common chain: cat or dog bites, or scratches. Licking of damaged skin; kissing animals b) Capsule and endotoxin are VF’s 3. Clinical & Diagnosis a) Most commonly: rapidly spreading cellulites associated with animal bite b) Abscesses, osteomyelitis, necrotizing soft tissue infection are possible c) Meningitis can occur in infants, elderly d) Pneumonia can occur with underlying lung disease e) Diagnose by culturing from wound; must identify in polymicrobial culture 4. Treatment a) Penicillin G. Wound cleaning, debridement, surgical draining G. Bartonella Henselae (Cat-Scratch Disease CSD) 1. Properties a) Small rod, intracellular parasite 2. Transmission & Pathogenesis a) Part of oral ora in cate. Transmitted by scratches or bites; possible also by cat eas 3. Clinical & Diagnosis a) CSD is the most common zoonotic disease in the U.S. b) Lymphadenopathy in immunocompetent host; resoles w/o treatment. Rare systemic infection c) Immunocompromised/AIDS: lesions on skin (bacillary angiomatosis) or liver 4. Prevention a) Treat cats for eas 5. Treatment a) Competent: none, azithromycin if severe LA b) Compromised: doxycycline + rifampin for BA Page 19 fl fl fl  Exam 2 SG Gram-Negative Rods (Non-Enteric) H. Yersinia Pestis (Plague) 1. Properties a) Small rod, bipolar staining, intracellular b) Extremely low ID50 (1-10 organisms); potential bioweapon 2. Virulence Factors a) Capsular antigen (F-1) blocks phagocytosis b) Endotoxin c) Exotoxin d) V and W antigens (allow intracellular growth) e) Yops (Yersinia outer proteins): block in ammatory response 3. Pathogenesis & Epidemiology a) Transmitted among rodents by eas; humans bitten by infected eas are accidental hosts (1) Sylvatic cycle: wild rodents (esp. prairie dogs in the U.S.) (2) Urban cycle: rats in the city (not currently found in the U.S.) b) Pathology inside the ea encourages dissemination: (1) Forms bio lm in upper GI tract of ea, prevents nourishment (2) Starving “blocked ea” bites more hosts, regurgitates bacteria c) Respiratory droplet transmission can occur form patients with pneumonic plague 4. Clinical Findings a) Bubonic plague: cells accumulate in the bloodstream and localize in the lymph nodes, which swell, display hemorrhagic necrosis, called buboes (festering soars of lymph nodes typically in the upper thigh). Blood pressure drops; untreated fatality 60%. Leads to bacteremia, septic shock (endotoxin-mediated), pneumonia, and/or plague meningitis b) Septicemic plague: describes symptoms from bacteremia, including abscesses, intravascular coagulation, and cutaneous hemorrhaging. In 14th century Europe it was known as the black death. Untreated nearly 100% fatal c) Pneumonic plague is acquired by bacteremic lesions in the lungs, or by inhalation of respiratory droplets, and is highly contagious. Untreated nearly 100% fatal 5. Lab Diagnosis a) Staining of blood or pus from buboes; aerosolization threat 6. Prevention a) Control of rats in cities b) Avoiding eas, dead animals in wild c) Killed vaccine (bubonic/septicemic only) d) Prophylactic doxycycline if contact required with patients 7. Treatment a) Rapid treatment with streptomycin or doxycycline, 72 hours quarantined b) Noti able disease Page 20 fi fl fi fl fl fl fl fl fl Exam 2 SG Mycobacteria, Actinomycetes, Mycoplasma IV. Mycobacteria, Actinomycetes, Mycoplasma A. Mycobacterium Tuberculosis 1. Mycobacteria do NOT take up Gram stain; high lipid content in cell wall (mycolic acids, very long chain fatty acids) prevents it. They can be stained instead with red carbolfuchsin, which will not wash out their walls upon treatment with acid-alcohol (thus they are called “acid-fast”) 2. Major mycobacterial diseases are tuberculosis (TB) and leprosy (Hansen’s disease). “Atypical Mycobacteria” cause TB-like respiratory disease 3. Properties a) Obligate aerobe (causing disease in highly oxygenated tissues likes the lung, kidney) b) Intracellular in macrophages; thus mainly resides in the reticuloendothelial system c) Cord factor is a cell wall lipid that is an essential virulence factor. It prevents fusion of phagosomes containing M. Tuberculosis with lysosomes in the macrophage, allowing the bacterium to survive inside the macrophages d) NO exo- or endotoxins (pathology is due to interaction with immune response) e) Drug resistance is due to mutations in chromosomal genes, NOT to plasmids (worldwide problem) f) Slow-growing (generation time 15-20 hours, disease develop in 6-8 weeks), requires complex nutrients: so di cult to culture, & requires long treatment g) Resistant to dehydration (survives in dried sputum and important in its transmission by aerosol) and to alkali and disinfectants 4. Transmission & Epidemiology a) Respiratory droplet transmission, mostly from individuals with active disease, but some from latent cases (5-10% of infected people develop primary active TB within 3 months; 90% have latent TB) b) Humans are reservoir (1) Another species, M. Bovis, causes TB in cows, and can cause gastrointestinal TB in humans who drink unpasteurized milk from infected cows (mostly happens outside U.S.) c) M. Bovis (live, attenuated) constitutes the BCG (bacillus Calmette-Guerin) vaccine against active TB 5. Tubercle Formation and Dissemination a) Initial site of infection is the lung (upon primary infection with M. Tuberculosis, the main immune response is based one cellular immunity) b) Infection of macrophages. Preventing from fusing with the lysosome, intracellular replication, cell-mediated response Page 21 ffi  Exam 2 SG Mycobacteria, Actinomycetes, Mycoplasma c) Tubercle formation (1) macrophages, lymphocytes surround a “caseous” (cheesy) center (2) Dead macrophages release bacilli in center; mac’s fuse (3) Disease may become dormant d) Mature tubercle ( brous tissue forms around granuloma; center enlarges) e) Tubercle rupture allows dissemination of bacteria 6. Progression a) Primary lesion usually occur in lower lobes of lung b) Reactivation lesions occur in the other organs (primarily in weak or immunocompromised patients) c) Dissemination occurs by 2 mechanisms (1) Tubercle breaks, empties to bronchus: (a) Seed lungs, GI tract, meninges; contagious (2) Bacteremia if infection not contained, infect and from tubercles in many organs (“miliary” TB) 7. Clinical Findings a) Commonly: fever, fatigue, night sweats, weight loss b) Pulmonary: cough, coughing up blood c) Scrofula: swollen, non-tender cervical lymph nodes d) Erythema nodosum: tender nodules on shins e) Disseminated: miliary (multiple lesions); meningitis; osteomyelitis f) GI: pain, diarrhea; oropharyngeal g) Renal: dysuria, hematuria, ank pain h) AIDS patients: high rate of reactivation; 50% fatal if untreated. Leading cause of death in co-infected in patients 8. Lab Diagnosis a) Acid-fast staining of specimens; if positive, do PCR to con rm b) Culturing (weeks) + biochemical testing c) For latent infections: (1) PPD (puri ed protein derivative) skin test (disadvantages: patient must return in 48 hours; interpretation) (2) Interferon gamma release test. (ELISA): more IFNy produced if exposed d) Rapid tests for drug resistance: (1) PCR detects mutations in genes that cause resistance (the catalase gene and the RNA polymerase gene) (2) Luciferase test: re ects amount of ATP made; drug-sensitive bugs make less 9. Tuberculin Skin Test (Mantoux Test) a) Become positive 4-6 weeks after injection b) Puri ed protein derivative (PPD) containing bacterial antigens is injected intradermally (1) If the patient was previously exposed to the bacterium, a delayed (Type IV) hypersensitive response will cause an induration (a thick, red weal) to from in 48 hours (2) The size of the induration is measured to determine whether the response is considered positive or not Page 22 fi fi fi fl fl fi  Exam 2 SG Mycobacteria, Actinomycetes, Mycoplasma 10. Prevention a) Prompt identi cation and treatment of patients with active TB b) Respiratory protection for medical personnel c) PPD screening of susceptible individuals, plus treatment of latent infections d) BCG vaccine: does not prevent infection; does reduce active disease. Use in U.S. is limited; is used in countries with high incidence. Can cause disease if recipient immunocompromised. New vaccines are under development e) Pasteurizing milk prevents M. Bovis 11. Treatment a) Treatment are long (6-9 months or more) b/c organisms is intracellular, slow- growing, and produces dormant persister cells that are antibiotic resistant; and because of poor penetration to granulomas b) Long treatment → noncompliance → drug resistance. Can address with DOT (directly observed therapy) c) Regimens generally involve rifampin, isoniazid (INH), pyrazinamide, ethambutol (RIPE) or streptomycin d) Multidrug resistant TB (MDR strains, usually resistant to INH + rifampin): multiple other Ab’s (4 or 5) may be used e) Extensively drug resistant (XDR) strains have emerged in Africa (MDR + uoroquinolone + another) in HIV-infected patients B. Atypical Mycobacteria “Atypical” b/c they di er from M. Tuberculosis. Also called “MOTTS” (mycobacteria other than tuberculosis) Widespread in environment (soil and water) M. Kansasii causes TB-like lung disease Antigenic cross-reactivity with M. Tuberculosis (so may cause positive PPD). Midwest, Texas Standard TB antibiotics for treatment M. Marine causes “swimming pool (or sh tank) granuloma.” Ulcerating lesions at abrasion points in swimmers Found in fresh and salt water Tetracycline treatment 1. M. Avium-intracellulare is a complex 2 species (also called avium complex, or MAC) a) Causes TB-like pulmonary disease in AIDs patients with low CD4 counts (most common type of atypical mycobacterial disease in AIDS patients) b) Widespread in soil and water c) Highly antibiotic resistant: requires combinations of up to 6-drugs 2. “Rapidly” growing mycobacteria a) M. Fortuitum-cheloni complex causes skin, soft tissue infections at puncture wounds (tattoo in: the immunocompromised & patients with prosthetic hip joints and indwelling catheters) b) Saprophytes (feed on dead things), found in soil and water. Ab-resistant. c) M. Abscessus cause chronic lung infections and others. Environmentally; Ab-resistant Page 23 fl fi ff fi  Exam 2 SG Mycobacteria, Actinomycetes, Mycoplasma C. Mycobacterium Leprae (Leprosy — Hansen’s Disease) 1. Properties a) Has not be cultured (obligate pathogen) can be grown in animals b) Humans are natural hosts c) Can be transmitted from armadillos to humans, but armadillos are not an important reservoir worldwide d) Low optimal temperature (30ºC) limits it to body surface e) Long doubling time (14 days) requires long therapy usually several years 2. Transmission & Epidemiology a) Prolonged contact with lepromatous patients is most important mode; shed in nasal secretions, skin lesions, so may acquire from respiratory droplets b) Patients no longer infectious after a few weeks’ treatment. Most people are naturally resistant. c) Leprosy occurs worldwide in tropic (India, Brazil, Africa); in the U.S. mostly among immigrants (100-300 new cases/year) 3. Pathogenesis a) Intracellular in skin histiocytes, endothelial cells, Schwann cells b) Relevant immune response is cell-mediated (CD4, Th1) c) Nerve damage is either from bacteria themselves or immune response 4. Clinical Findings a) Incubate for years; gradual onset b) Tuberculoid: single hypo-pigmented lesion with loss of feeling (anesthesia), typically nose, ears, or testicles c) Lepromatous: (1) Nodular skin lesion (2) “Leonine” facial appearance (3) Response to therapy induces erythema nodosumm leprosum d) Manifestation may range between tuberculoid and lepromatous e) Eyes and vision may be a ected f) Dis gurement due to: (1) Skin anesthesia → burns, trauma → infections (2) Bone resorptions, a ects nose and extremities (3) Thickening and folding of skin due to bacterial in ltration 5. Lab Diagnosis a) Tuberculoid: granulomas. Lepromatous: acid-fast stain of shed bacteria, PCR; syphillis tests may be falsely (+) 6. Prevention a) Isolation of patients; dapsone prophylaxis for exposed children. BCG vaccine confers some resistance 7. Treatment a) Dapsone + rifampin +/- clofazimine; signi cant resistance to dapsone itself > 2 years Page 24 fi ff ff fi fi  Exam 2 SG Mycobacteria, Actinomycetes, Mycoplasma D. Actinomycetes Filamentous, like fungi Gram positive , some also weakly acid-fast 1. Actinomyces israeli a) Normal oral microbiota, invades after trauma, or poor dental hygiene b) Yellow “sulfur” granules (mass of laments) in draining pus c) 50% in face and neck; remainder in chest or abdomen d) Prolonged IUD (intrauterine device) retention can cause pelvic actinomycosis 2. Nocardia asteroides a) Primarily in soil, inhaled or in wounds b) Can infect immunocompromised lungs, cause abscesses & pneumonia, then disseminate E. Mycoplasmas Among the smallest bacteria known Lack a cell wall. Antibiotics that target walls are not e ective; shape of can can change. Does NOT gram stain Cell membrane contains cholesterol sti ens it, as in eukaryotes) Cause problems in laboratory tissue couture of eukaryotic cells 1. M. Pneumoniae (Atypical Pneumonia) Pathogenic only in humans Transmitted by respiratory droplets Adhesions for ciliated bronchial epithelium; exotoxin similar to pertussis Causes in ammation, necrosis; inhibit ciliary motion Causes 10-20% of CA pneumonia, especially among young adults in close quarters (“atypical = signs, symptoms unlike pneumococcal), more frequent in fall and winter Autoantibodies against red blood cells, brain, lung, liver form during infection a) Clinical Findings (1) M. Pneumonia is the most common cause of atypical pneumonia (a) Symptoms are those of a “bad cold” with fever, headache, malaise, long- lasting cough (b) Possible complications: encephalitis, anemia, renal problems, rash (c) < half those infected actually get pneumonia (2) Also causes sore throat, otitis media, bronchitis (all more frequent than pneumonia) b) Lab Diagnosis (serological tests) (1) Speci c antibodies detected by complement xation (2) PCR tests (3) Many patients produce cross-reactive antibodies that cause agglutination of red blood cells at 4ºC (called “cold agglutinins”). Can also cause agglutination of RBCs in vivo in low temperatures c) Treatment (1) Usually resolves untreated (2) Antibiotics can shorten course: macrolides, tetracycline (3) Doxycycline, Azithromycin, Levo oxacin Page 25 fi fl fi fl ff fi ff Exam 2 SG Mycobacteria, Actinomycetes, Mycoplasma 2. Genital Mycoplasmas (Found in Urogenital Tract) a) M. Hominis causes postpartum fever, pelvic in ammatory disease b) Ureaplasma Urealyticum causes non-gonococcal urethritis. In women causes endometritis, and is associated with premature labor and delivery c) M. Genitalium is sexually-transmitted; causes non-gonococcal urethritis in men. In women causes cervical in ammation, pelvic in ammatory disease. Diagnosed by PCR Page 26 fl fl fl Exam 2 SG Mycobacteria, Actinomycetes, Mycoplasma V. Spirochetes, Chlamydia, and Rickettsia A. Page 27