Lecture 04 - The Bacilli PDF

Lecture 4 — The Bacilli Dr. Ed El Sayed NURS 342 RODS Objectives What are the major features and characteristics of Gram negative bacilli? What are some of the clinically relevant examples? What are the major features and characteristics of Gram positive bacilli? What are some of the clinically rele...

Lecture 4 — The Bacilli Dr. Ed El Sayed NURS 342 RODS Objectives What are the major features and characteristics of Gram negative bacilli? What are some of the clinically relevant examples? What are the major features and characteristics of Gram positive bacilli? What are some of the clinically relevant examples? I. Gram negative bacilli Loading… Gram negative bacilli Obligate aerobic Obligate anaerobic Facultative anaerobic Pseudomonas Bordetella Bacteroides Escherichia Salmonella Shigella Klebsiella Vibrio Haemophilus Bacteria that account for the majority of nosocomial infections a. b. Overall contribution of Gram negative bacteria vs. other bacteria Loading… Comparison of the relative proportion of each genus or species isolated from infections by the Gram negative enteric group Common features and virulence factors among Gram negative bacilli agents Motile by flagella — the flagella acts as a major antigen (H) to illicit an immune reaction K antigen — protects against harsh environments O antigen — enables bacteria to resist phagocytosis Ability to release endotoxin upon cell lysis (e.g. lipopolysaccharide LPS) — this is a major cause of sepsis and septic shock Black spheres are LPS molecules that are released as endotoxin upon bacterial cell lysis Pseudomonas aeruginosa Obligate aerobe Inhabitant of many environments (soil, water, vegetation) Isolated from many body parts (mouth, ears) as normal flora Has been found to colonize hospitals (water tanks, sinks) Spread is from patient to patient via contact with fomites or by ingestion of contaminated food and water Causes myriad of diseases (lung, eye, urinary tract infections) — particular concern among burn victims Antibiotic resistance on the rise (DISASTER!) Bordetella pertussis Obligate aerobe Pleomorphic (mainly bacilli, but can exist as cocci) Special virulence factors include pertussis exotoxin, hemagglutinin, and hemolysin — all induce severe inflammation of respiratory tract Causes whopping cough (mainly in children, but anyone can get it) Humans are the sole reservoir Transmission is via aerosolized droplets (cough, sneezing) Majority of cases occur in summertime Vaccine preventable, but cases on the rise Loading… Bacteroides Obligate anaerobe Common inhabitant of human gastrointestinal tract Passed from mom-to-baby as part of the normal flora during vaginal delivery Microbiota imbalance allows Bacteroides to overgrow resulting in gastrointestinal disease Systemic infection associated with bacteremia, endocarditis, meningitis and septic arthritis Animal/human bites can result in skin and soft tissue infection Escherichia coli Facultative anaerobe Most studied Gram negative bacteria in microbiology research Major cause of urinary tract infection (over 90% of UTI cases among women) Enterotoxigenic E. coli (ETEC): Major cause of diarrheal disease (traveller diarrhea) Shiga-toxin producing E. coli (STEC): Affect other organs like kidneys and blood vessels (E. coli O157:H7) resulting in hemolytic uremic syndrome and thrombocytopenia In neonates and immunocompromised adults, E. coli can cause sepsis and meningitis Vibrio cholera Hibalori-shape ? Facultative anaerobe Distinctive “comma-shape” morphology Highly motile with single flagella Found in unclean water sources (sewage) and can survive high salt concentration (halophilic) salt - - - - can survive Infection results in severe watery diarrhea (“rice water diarrhea”) and vomiting ↳ can die If left untreated, loss of fluid results in electrolyte imbalance — neurologic disease and k+ arrhythmeiad death ↑ I only - = No antibiotic Treatment is primarily supportive (fluids and electrolytes) This infection is on the rise due to war O O O A Rice water diarrhea Social injustice in infectious diseases Children of cholera in Yemen Salmonella Facultative anaerobe Huge animal reservoir, causes disease in humans after ingesting contaminated foods (mode of transmission is oral-fecal) Eggs, poultry not cooked properly increases risk of infection The major disease worldwide is enteric colitis and diarrhea (supportive treatment only if patient is not immunocompromised) In African-Americans with sickle-cell disease, Salmonella is the most common cause of osteomyelitis (requires antibiotic therapy) In certain parts of the world, S. typhi is the cause of typhoid fever (requires antibiotic therapy) Shigella Facultative anaerobe Main natural reservoir is human gastrointestinal tract S. dysenteriae releases an exotoxin that causes severe inflammation in the gastrointestinal tract and the result is perfuse watery diarrhea, if left untreated, mucus and blood start to appear in stool (dysenteric fever) Klebseilla Facultative anaerobe While it is classified as an “enteric” bacteria, the main infections are in the lungs (pneumonia) and urinary tract (cystitis); higher risk of infection in alcohol misuse Transmission can also happen in healthcare settings Haemophilus Facultative anaerobe Unique among the Gram negative bacilli group because it is non-motile (no flagella) Pleomorphic (mainly bacilli, but can exist as cocci) Humans are the only known reservoir Two important species: H. influenzae and H. ducreyi H. influenzae causes pneumonia and meningitis H. ducreyi is can be transmitted sexually, causes chancroid Only H. influenzae is vaccine preventable H. ducreyi ulcer Syphilis ulcer How can you tell them apart? II. Gram positive bacilli Gram positive bacilli Non-spore forming Spore forming Bacillus Clostridium Regular stain Listeria Specialized stain Mycobacteria Corynebacteria Nocardia A. Spore forming agents Loading… Bacillus Gram positive aerobic bacilli Spore forming Primary habitat is soil B. cereus and B. anthracis Bacillus cereus Spore forming in the environment — known to resist harsh conditions Grows in food and can survive cooking/heating Releases toxin after ingestion of contaminated foods and causes gastrointestinal disease and diarrhea Common “buzz words” in clinic: “I had fried rice before I got sick!” No vaccine, no specific therapy — supportive care only (fluids, antipyretics) Bacillus anthracis Large size, block shape rods or bacilli - - - Has central spores * location : Central - Virulence factors include capsule formation and release of exotoxins - m k-antigen - Causes anthrax (cutaneous, pulmonary or gastrointestinal) Considered a “biological weapon” centrapre NOT central Terminal B. anthracis with central spores Clostridium Gram positive anaerobic bacilli Spore forming Bacteria is motile by flagella Also found in soil C. perfringes, C. difficile, C. tetani, and C. botulinum Clostridium perfringes Has subterminal spores Common cause of food poisoning (poultry, vegetables) Causes gas gangrene in infected tissues and muscle fibers Virulence factors include DNAse, collagenase and alpha toxins (breakdown cell membranes and cause hemolysis) “Double Zone Hemolysis” is characteristic of C. perfringes C. perferinges with subterminal spores Double Zone Hemolysis Gangrene Clostridioides difficile (C. Diff) at bay in immune healthy Normally present as flora in the colon Suppressed by other bacteria in the gut, but with misuse of antibiotics, C. diff can overgrow and shift the balance of microbiota to cause disease - - Major virulence factor is the release of toxin A and toxin B released/produced & only These toxins alter colon permeability and resultsin watery diarrhea - - when a diff is causing disease These toxins can also cause severe damage to the colon (membranous colitis, and if left untreated the result is malignant toxic megacolon) Treated with-antibiotics, fecal transplantation used in patents with multiple recurrence or antibiotic resistance --- Normal colon Pseudomembranous colitis Toxic megacolon Clostridium tetani Normally present in soil and animal intestines (animals defecate and bacteria stays in soil) - - = Bacteria is pin shaped and spores are always terminal > - - KNOW locatio for all Open wounds allow the passage of these spores into the body - Most significant virulence factor is tetanospasmin — an exotoxin that causes spastic paralysis (antagonizes glycine, an inhibitory neurotransmitter) - I & - - > - US. flacid No control (both) , flacid = movable , spastic = nonmorable t =° bui Symptomatic patients require supportive care treatment, usually in ICU I - bl Vaccine preventable, must be given with every pregnancy - you need intubation C. tetani with terminal spores Clostridium botulinum Bacteria present in soil, canned foods Bacteria is cylindrical in shape and spores are mainly terminal (sometimes subterminal) Improper storage of contaminated foods causes germination of spores and the bacteria releases toxin Can also enter the body directly through contaminated wounds Major virulence factor is botulinum toxin, which causes flaccid paralysis (inhibits release of acetylcholine), results in respiratory failure Treatment of botulism is primarily with anti-toxin (not antibiotics!) C. botulinum with terminal spores C. botulinum is cylindrical Spores mainly terminal C. tetani is pin shaped Spores always terminal B. Non-spore forming agents Listeria monocytogenes Facultative intracellular bacilli that is motile due to flagella Primary reservoir is water and soil Contaminates food (poultry, diary) and can grow even if food is refrigerated Major virulence factor is Listeriolysin — an enzyme that enables listeria to form pores within macrophages and escape Majority of infection causes gastrointestinal symptoms (food borne disease), only supportive care needed in immunocompetent persons Immunocompromised patients and extreme ages are at risk for listeria meningitis, requires intensive antibiotic treatment Corynebacterium diphtheriae Club-shaped Gram positive bacilli that is non-motile Cell wall has a unique peptidoglycan structure that makes Gram stain escape — gives a false impression of Gram negative stain (that is why it is stained with methylene blue or Albert stain to confirm diagnosis) Infection spreads through respiratory droplets (coughing or sneezing), very rarely through contact with infected, open wounds on skin Major virulence factor is diphtheria toxin — kills cells in the respiratory tract, eventually forming “pseudomembrane” that blocks and clogs trachea Most cases are in children, but rare in US due to vaccination (diphtheria, tetanus, and pertussis combo) Mycobacteria Irregular in shape Specialized staining due to MYCOLIC acid cell wall — Acid fast stain Obligate aerobes No flagella — non-motile Grows very slowly in lab Two main species: M. tuberculosis and M. leprae Mycobacteria tuberculosis (TB) Primary transmission is airborne droplets — coughing, sneezing, yelling, singing Major virulence factors are proteins called LAMs and PIMs that allow the bacteria to attach to host cells and resist killing by the immune system, these proteins make active TB easily transmissible and highly infectious Disease divided in to active phase (symptomatic) and latent phase (asymptomatic) — latency can revert to active disease under certain conditions No vaccine, but we have excellent drugs to treat the infection Mycobacteria leprae (Hansen disease) Primary transmission is airborne droplets Casual interactions (handshaking, playing) does not transmit infection Major virulence factors include waxy cell wall to evade immune system, genes that allow the bacteria to survive in nutrient deficient environment, genes that protect against drugs Bacteria can lay dormant (no symptoms for decades!) M. leprae is very difficult to grow in culture In the southern United States, some armadillos are naturally infected with M. leprae Infection causes leprosy — starts in skin and mucous membranes then disseminates to nerves, eyes and lungs Causes severe disfiguration No vaccine, but combination drugs available for treatment (Tx duration is years!) Nocardia ↳ immune compromised pt > - altenomises in comptent Found in environment, mainly soil and water - immode - · Aerobic bacteria that forms branching chains which look like fungal hyphae E - T ↓ Has mycolic acid cell wall - Like TB = - ala SOP-counteract Major virulence factor is superoxide dismutase — an enzyme that inactivates reactive oxygen species which is toxic to bacteria - > ⑫ - - °@ - Primarily infects skin upon contact with contaminated soil or water Infection can also enter through the lung (via inhalation of aerosolized particles containing bacteria) - -- - - Dissemination to blood or other organs (lungs, eyes, brain) possible, especially in immunocompromised patients -- O Another bacteria, actinomyces, causes similar symptoms in immunocompetent persons Nocarida with hyphae “Keep your face always toward the sunshine and shadows will fall behind you.”