1. 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.

2. Mycoplasma 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

3. 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.

4. 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

5. 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

6. 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.

7. 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 ( µm) and inert
Spore-like: dormant and resistant
Infectious: form that moves between cells
Reticulate body: µm, metabolically active, reproduce inside host cells

8. 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.

9. 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.

10. Spirochetes 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.

11. 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

12. Gram negative curved rods
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

13. 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.