Microbiology: Gram-Negative Bacteria (BIOL2700) PDF

1 Microbiology: The Bad Bugs Part II: The Gram Negatives BIOL2700 Version 03 2 Microbiology Gram Negatives Gram - Spiral Cocci Rod Treponema Borrelia Leptospira Neisseria Curve Straight Other +O2 Pseudomonas. +/-O2 Enteric Many! Vibrio Campylobacter Helicobacter -O2 Bacteroides Resp. Bordetella Haem...

1 Microbiology: The Bad Bugs Part II: The Gram Negatives BIOL2700 Version 03 2 Microbiology Gram Negatives Gram - Spiral Cocci Rod Treponema Borrelia Leptospira Neisseria Curve Straight Other +O2 Pseudomonas. +/-O2 Enteric Many! Vibrio Campylobacter Helicobacter -O2 Bacteroides Resp. Bordetella Haemophilus Legionella Zoonoses Yersinia Pasteurella Brucella Francisella Streptobacillus GU H. Ducreyi 3 Microbiology Gram Negatives: G- Rods and Cocci Endotoxin: Lipid A, the superantigen Part of LPS of the Gram negative outer membrane Causes an over-stimulation of macrophages with production of various cytokines Fever, vasodilation, inflammation, shock, and disseminated intravascular coagulation While Gram negative pathogens can have other virulence factors (capsules, fimbriae, exotoxins), all have endotoxin and are thus dangerous. Over-stimulates macrophages via production of various cytokines Part of phospholipid portion of OM Lipid A Results in not only fever & inflammation, but shock & even DIC Microbiology Gram Negatives: Neisseria: G- Cocci Very few G- cocci; these are pathogenic ones N. meningitidis and N. gonorrhoeae. Delicate and fastidious; coffee bean shaped in pairs pyogenic N. meningitidis: well known cause of bacterial meningitis – Capsule protects cells during phagocytosis – Present as normal microbiota in 40% of population – Transmitted by droplets, close contact – Infection of meninges, sore throat, high fever, headache, stiff neck, vomiting, convulsions; rapid course. – Epidemiology: people living in close contact; military recruits currently vaccinated; also many college students. N. gonorrhoeae: cause of gonorrhea, STI – Virulence factors: capsule, fimbriae, survival in neutrophils – Males: painful purluent discharge from urethra – Females: often asymptomatic; otherwise, urethritis, PID, infections anywhere sexual contact occurs, arthritis. – Eye infection of newborns – No long term immunity! 4 Microbiology Gram Negatives: Enterobacteriaceae: G- Rods Facultatively anaerobic; found in soil, water, and GI tracts some strictly pathogens, others opportunists Generally divided into: Coliforms (ferment lactose) Non-coliforms Virulence factors Endotoxin, capsules, fimbriae, exotoxins, others. Enteric bacteria identified by biochemical tests Selective/differential media, etc. Strains identified by serological techniques Use of antibodies to identify particular antigenic molecules on cell surfaces O antigen: repeating sugar group on LPS H antigen: flagellar protein K antigen: capsule antigen around cell. Example: E. coli O157:H7 describes particular serotype which happens to also produce a dangerous exotoxin (Shiga toxin-inhibits protein synthesis). 5 Microbiology Gram Negatives: Hey, I thought E. coli was a “good guy”? Most strains common to GI tract, not harmful there…however, it is: One of the most common causes of diarrhea The most common cause of urinary tract infections Many strains possess plasmids that code for additional virulence factors (Ie, Shiga toxin) which cause disease E. coli O157:H7: common in cows, deer, swine. In humans will cause hemolytic uremia syndrome, destroys bowel, damages kidneys. 6 Microbiology Gram Negatives: Opportunistic Enterics (G- “Straight” Rods) Klebsiella pneumoniae: various opportunistic infections including wound infections, pneumonia – Capsule is major virulence factor Proteus sp: changes shape and flagella between liquid and solid media; common cause of urinary tract infections – Produces urease Enterobacter aerogenes – Coliform; GI tract and environmental – Wound infections Found normally in the mouth, skin, and intestines, Fecal contamination a problem, especially in hospital patients. Some resistance to ABX Found in soil, feces. Can be treated with ABX 7 Microbiology Gram Negatives: Pathogenic Enterics (G- “Straight” Rods) Salmonella sp: species so closely related that they are really all S. enterica. But medically, species epithets still used: S. typhi and others. Divided serologically. – Present on eggs, poultry, on animals such as reptiles – Large dose results in food poisoning; diarrhea, fever, etc. – Cells phagocytized by intestinal lining cells, kill cells causing symptoms, may pass through into blood. – S. typhi: typhoid fever. Spread through body Gall bladder as reservoir; Typhoid Mary Importance of clean water and sewage treatment. Mary died after 26 years in quarantine, from pneumonia Reservoir is humans. ABX useful. Surgery to remove gall bladder. Vaccine developed. Mary Mallon (wearing glasses) photographed with bacteriologist Emma Sherman on North Brother Island in 1931 or 1932, over 15 years after she had been quarantined there permanently. 8 Microbiology Gram Negatives: Pathogenic Enterics (G- “Straight” Rods) Shigella sp: especially S. sonnei (most common) and S. dysenteriae (most serious); cause shigellosis. – Food, flies, fingers, feces, fomites: very small infectious dose, personal hygiene important in prevention. – Infection of intestinal lining damaged, cells pass directly from cell to cell; cramps, diarrhea, bloody stools. – S. dysenteriae produces shiga toxin which inhibits protein synthesis, increases damage. – Most serious problem with diarrheal diseases in general is dehydration. 9 Microbiology Gram Negatives: Pathogenic Enterics (G- “Straight” Rods) Yersinia sp: Y. pestis is cause of plague, other species cause food-borne infections Plague: 3 cycles: sylvan, urban, and human – endemic in sylvan cycle; mixing of woodland and urban rodents brings urban cycle, fleas jump from dying rats to humans. – Infection leads to large swollen lymph nodes: buboes Bubonic plague, with high fever. Septicemic plague: with DIC, bruising (The “black death”) – Raises mortality from75% to near 100% Pneumonic: coughed out and spread human to human ~100% mortality 10 Zoonotic “Ring around the rosie” Microbiology Gram Negatives: Pasteurellaceae: Small G- Rods Fastidious P. multocida – Common in animals; significant disease present in commercial and domestic poultry flocks, people get it via bites, scratches – Inflammation, swollen nodes near site if infection 11 Zoonotic Microbiology Gram Negatives: G- pleomorphic, filamentous rod: Streptobacillus Streptobacillus moniliformis is the usual cause of rat-bite fever. Incidence is highest in urban areas with poor sanitation. Also, occupational contact with rodents such as pet shop employees or laboratory workers or through pet ownership. The disease typically presents with chills and fever accompanied by headache, vomiting, and muscle pain. A rash and arthritis develop 2–4 days after the initial onset. Can also cause pneumonitis, endocarditis or meningitis. Often misdiagnosed and classified as a fever of unknown origin (FUO). If untreated, death will occur in approximately 10% of cases. 12 Zoonotic ABX effective. Also, Haverhill Fever where the rats get into the food. Microbiology Gram Negatives: G- Coccobacilli: (“Very Short” )Rods 13 Zoonotic Brucella sp: different species for each animal – Infection from contact with livestock, fluids, incl dairy – Undulant fever: fever that goes up and down A zoonosis transmitted by ingesting contaminated food (such as unpasteurized milk products), direct contact with an infected animal, or inhalation of aerosols. Foul-smelling perspiration is considered a classical sign. Up to 60% of cases have joint complications. First, the bacterium does not bear classic virulence factors, such as capsules, secreted proteases, exotoxins, endotoxins, pili and/or fimbriae or virulence plasmids, and its lipopolysaccharide pathogenicity is not typical. Second, it exhibits a tendency to invade and persist in the human host through inhibition of programmed cell death. Microbiology Gram Negatives: G- Coccobacilli: (“Very Short” )Rods Bordetella sp: B. pertussis, cause of whooping cough – Infects trachea, several toxins. – Disease in stages: incubation, catarrhal, paroxysmal Coughing and inhalation: whoop – DPT (but also new acellular vaccine) 14 Zoonotic Bordatella also has capsule, fimbria. Pertussis toxin affects cell signaling, and turns off phagocytes. Also in primates. ABX effective. Microbiology Gram Negatives: G- Coccobacilli: Haemophilus H. influenzae and H. ducreyi – H. influenzae: mostly respiratory infections, otitis, meningitis, and epiglottitis in very young. – Capsule is major virulence factor; Hib vaccine protects – H. ducreyi: STI, chancroid; visible and painful in men. 15 H flu lives in the nose & throat. Microbiology Gram Negatives: Pseudomonas: G- Aerobic Rod Very common in environment, soil P.aeruginosa the most dangerous; opportunist – Endotoxin, exotoxins, fimbriae, enzymes, capsule – Capable of causing disease anywhere in body – Two major problems: burn patients and cystic fibrosis Cause of swimmer’s ear (can also be fungal), hot tub infections, etc. – Resistant to most disinfectants and antibiotics 16 Microbiology Gram Negatives: Other G- Rods-Francisella 17 Francisella tularensis, cause of tularemia – Also called rabbit fever, tick fever, deerfly fever, etc. – Most cases in SE USA – Survives phagocytosis, lives intracellularly – Present in many animals, transferred to humans by vector, ingestion, direct contact, inhalation – Chills, fever, malaise, swollen nodes Microbiology Gram Negatives: Other G- Pleomorphic Rods-Legionella Legionella pneumophila and several others Fastidious in culture, requires special media Very common in aquatic environments: ponds, cooling towers, hot-water heaters, showers. Grows normally in amoebae, so also grows in phagocytes Most dangerous as opportunistic pneumonia, inhalation Mild form of disease: “Pontiac fever” Also have flagella & pili 18 Microbiology Gram Negatives: Anaerobic G- Rods Bacteroides sp Many different anaerobic bacteria live in parts of body, esp. GI tract (>99% anaerobes) but also in mouth, genito-urinary tract. Trauma to these areas leads to polymicrobic inections. In GI tract, a common bacterium is Bacteroides Opportunist, causes abscesses in GI, reproductive, wound infections 19 Microbiology Gram Negatives: G- Spirochetes: Leptospira Produces Hemolysins Leptospira sp transmitted by both wild and domestic animals. Most common animals that spread the disease are rodents. Transmitted by animal urine or water containing animal urine coming into contact with breaks in the skin, the eyes, mouth, nose or vagina. Leptospirosis is a two-phase disease that begins with flu-like symptoms (fever, chills, myalgias, intense headache). First phase usually resolves (90%) If it progresses to the second phase expect liver damage, renal failure, meningitis, encephalitis 20 Microbiology Gram Negatives: G- Spirochetes: Spirochaetes Spirochetes: little “corkscrew-like” things – Have internal flagella in bundles called axial filaments; twist through liquid media Treponema pallidum: cause of syphilis (an STI), other forms are nonvenereal like bejel, yaws, etc. – Initial stages: chancre, hard, painless genital ulcer following long incubation – Ulcer disappears, spirochete spreads, causes systemic disease (rash, fever, etc) – Either goes away, comes back, or tertiary syphilis in which gummas form; serious stage. gumma is a soft, non-cancerous growth resulting from the tertiary stage of syphilis. It is a form of granuloma. 21 Unknown virulence 22 Microbiology Gram Negatives: G- Spirochetes: Borrelia Borrelia burgdorferi: cause of Lyme disease – Reservoir in rodents, deer; spread by deer tick – Slow developing; fever, usually bulls-eye rash; arthritis and heart or CNS involvement. Borrelia recurrentis: cause of relapsing fever – Human reservoir, spread by lice or ticks – Causes fever which comes and goes – Microbe switches antigens, makes comeback, then immune system catches up again. No LPS. Antigen switch. Secretes proteins that inhibit proper function of blood vessels, platelets, and cartilage. Microbiology Gram Negatives: G- Curved Rods: Vibrio Like enteric; polar flagella Halotolerant to halophilic, grow in estuarine and marine environments V. cholerae: cause of cholera Toxin-mediated severe diarrhea Salt, fluid leave intestinal cells, patient dies of dehydration. Oral rehydration therapy (ORT): water, salts, and glucose, now saving lives. Causes pandemics that spread around the world Lack of adequate sewage treatment 23 Microbiology Gram Negatives: G- Curved Rods: Campylobacter 24 Campylobacter jejuni: number Flagella plus chemotaxis one cause of bacterial gastroenteritis; zoonotic More common than Salmonella and Shigella combined for food borne disease. Most retail chickens are contaminated; improperly cooked chicken and contaminated milk are typical vehicles. Low infectious dose 25 Microbiology Gram Negatives: G- Curved Rods: Helicobacter Helicobacter pylori Cause of ulcers and gastritis 2005 Nobel Prize for Medicine or physiology to Barry Marshall and J Robin Warren Unusual because it can live in stomach Produces urease enzyme Released ammonia neutralizes stomach acid, irritates stomach lining. Basis for radioactive urease test. Correlated with stomach cancer. Flagella and cytotoxin