Miscellaneous bacterial pathogens Bacteria without cell walls Bacteria

Miscellaneous bacterial pathogens • Bacteria without cell walls • Bacteria that require host cells • Spiral and curved bacteria • Some of these are related to Gram positives and some are Gram negative, but all stain pink in a Gram stain. • Most are difficult or impossible to grow in the lab. 1

Mycoplasma 2 • Mycoplasmas have unusual properties – Very small, pleomorphic (cocci to filaments) – Have no cell walls, but have sterols in their membranes – Require numerous growth factors to grow • Species of interest: M. pneumoniae, – M. pneumo attaches to epithelial cells, kills them – Buildup of mucus, other infections – Fever, malaise, sore throat, etc. walking pneumonia – No cell wall! Can’t treat with penicillins

Mycoplasma-2 • Ureaplasma urealyticum – Sexually transmitted, cause of urethritis – Similar to M. pneumoniae, but urease + – Other Mycoplasmas also cause NGU • Non-gonococcal urethritis, infections caused by something other than N. gonorrhoeae. http: //www. ai. mit. edu/people/tk/ce/mycoplasma-s. gif 3

Rickettsiae • Gram negative, very small, obligate parasites – Leaky membranes? • Most diseases spread by vectors • Rickettsiae infect endothelial cells lining blood vessels, avoid digestion in lysozome – Have LPS, generate fever – Damage to capillaries produces spots, rashes – Damage to vessels deprives organs of oxygen 4

Rickettsial diseases • R. rickettsii: Rocky mountain spotted fever – Spread by tick bite; rodents are the reservoir – Most common through southeast, mid-south • R. prowazekii: epidemic typhus – Humans primary host; vector is the louse – Disease spread in crowded, unhygienic conditions • R. typhi: murine/endemic typhus – present in rodent population, vector is the flea 5

Rickettsiae-2 • Ehrlichia chaffeensis- cause of 2 types of ehrlichiosis. – Similar to other rickettsial diseases, seldom rash – Spread by lone star tick and dog tick – Infects leukocytes rather than endothelial cells – “emerging disease”, first identified by case at Fort Chaffee, Arkansas. 6

Chlamydia • Very small, obligate intracellular parasites – Cell and outer membrane, but no peptidoglycan • Spread directly rather than by vectors • Two stage life cycle – Elementary body: tiny (0. 2 -0. 4 µm) and inert • Spore-like: dormant and resistant • Infectious: form that moves between cells – Reticulate body: 0. 6 -1. 5 µm, metabolically active, reproduce inside host cells 7

Chlamydial diseases • C. trachomatis: infects cells of mucous membranes, conjunctiva. Mostly eye & STD – Infection kills cells, stimulates inflammation which also causes cell destruction • Trachoma- leading cause of non-traumatic blindness. Caused by certain strains. – Infection of conjunctiva causes scarring, turning in on eyelashes which scratch cornea. – Scarred cornea, with ingrown blood vessels, obscure vision. – STD strains can also infect eyes, self-inoculation. 8

Sexually transmitted Chlamydial disease • Non-gonococcal urethritis, about 50% of cases • Chlamydia infections are the most common STD, but even more are infected and asymptomatic • Lymphogranuloma venereum – Lymph nodes in genital region (inguinal) become enlarged (buboes), may even rupture. – Blocked lymph ducts lead to genital elephantiasis, other damage in genital region. – 85% of women asymptomatic; others can develop PID; scarring of uterine tubes can lead to sterility, ectopic pregnancy. • Eye infections of newborns prevented with antibiotic drops. 9

Spirochetes 10 • Spirochetes: teeny weeny squiggly things – Have internal flagella in bundles called axial filaments; corkscrew through liquid • Treponema pallidum: cause of syphilis, STD – 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.

Spirochetes-2 • 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 • Leptospira interrogans: cause of leptospirosis – From contact with animal fluids, esp. urine. – Infects liver and kidneys, from kidney enters urine – Note: tidy cycle of spread and infection 11

Gram negative curved rods 12 • Vibrio: comma shaped – Like enteric but oxidase positive; 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

Other curved rods • Campylobacter jejuni: number one cause of bacterial gastroenteritis; zoonotic – More common than Salmonella and Shigella combined for food borne disease. • Helicobacter pylori: cause of ulcers – Correlated with stomach cancer. – Produces urease enzyme • Released ammonia neutralizes stomach acid, irritates stomach lining. • Basis for radioactive urease test. 13