Organism needed to know for final

Bordetella pertussis

Whooping cough (pertussis). Droplet transmission; adhesins attach it to ciliated respiratory epithelium. Pertussis exotoxin enhances inflammation and tracheal cytotoxin disables the mucociliary escalator, so mucus can't be cleared → violent coughing fits. Stages: catarrhal → paroxysmal → convalescent. DTaP/Tdap targets the toxin.

Candida albicans

Candidiasis (thrush, vaginal/cutaneous, systemic). Opportunistic normal microbiota; overgrows with antibiotic use, immunosuppression, diabetes or pregnancy. Grows on skin and mucous membranes of mouth and GU tract, forms biofilms; systemic form is life-threatening.

Clostridium botulinum

Botulism — an intoxication from canned/preserved food. Gram +, endospore-forming obligate anaerobe. Preformed A-B exotoxin prevents acetylcholine release at the neuromuscular junction → progressive flaccid paralysis; death from respiratory/cardiac failure. Infants susceptible because they lack competitive normal flora.

Clostridioides difficile

C. difficile colitis / antibiotic-associated diarrhea. Normal colon flora that overgrows after long-term antibiotic use or immunosuppression; releases membrane-disrupting exotoxins → mild diarrhea through severe colon inflammation and perforation. Major nosocomial infection (endospores); treated with narrow-spectrum antibiotics, rehydration, fecal transplant.

Clostridium perfringens

Gas gangrene. Gram +, endospore-forming obligate anaerobe from soil and normal GI flora. Enters wounds with interrupted blood supply (anaerobic conditions); toxins cause necrosis, and fermentation of nutrients releases gas that creates more anaerobic space. Treated by surgical removal/amputation, hyperbaric oxygen, antibiotics.

Clostridium tetani

Tetanus (lockjaw). Spores enter via puncture wounds — rusty objects, injection drug use, trivial injuries. Tetanospasmin exotoxin acts on the nervous system to prevent muscle relaxation, so opposing muscles contract together → spasms starting at the jaw, potentially reaching respiratory muscles. NOT communicable. TIg; DTaP with 10-year boosters.

Cryptococcus neoformans

Cryptococcosis — lung infection and cryptococcal meningitis. Yeast inhaled from dried pigeon droppings / urban soil. Gelatinous polysaccharide capsule allows evasion of phagocytosis, so it survives, multiplies and disseminates to the CNS. Serious in the immunosuppressed (AIDS); ~30% mortality; antifungals.

Cutibacterium acnes

Acne. Anaerobic normal skin flora in hair follicles; metabolizes the fats in sebum, and the free fatty acids released initiate an inflammatory response → papules and pustules. Non-communicable. Antibiotics, benzoyl peroxide, phototherapy.

Echinococcus granulosus

Hydatid disease (cystic echinococcosis). Dog tapeworm; humans become accidental intermediate hosts by ingesting eggs from dog feces. Larvae form slow-growing hydatid cysts in liver or lungs; damage is from cyst pressure on the organ, and rupture can trigger a severe allergic reaction.

Escherichia coli

E. coli gastroenteritis (traveller's diarrhea; EHEC hemorrhagic colitis); also UTIs. Harmless colon microbiota; 6 strains are pathogenic because they produce toxins. Fecal contamination of food/water. EPEC = moderately invasive, toxin, self-limiting watery diarrhea. EHEC (STEC) = NOT invasive, Shiga-like toxin → bloody diarrhea; O157:H7 can cause hemolytic uremic syndrome.

Giardia lamblia

Giardiasis. Flagellated protozoan; cysts ingested in contaminated water (camping outbreaks; cysts resist chlorine). Trophozoites attach to the intestinal wall rather than invading, blocking absorption → prolonged diarrhea for weeks with malaise, nausea, flatulence, cramps, weight loss.

Haemophilus influenzae

Meningitis (children <4) and pneumonia. Gram −; normal throat flora spread by contact with respiratory secretions. Polysaccharide capsule blocks phagocytosis, allowing invasion from nasopharynx into blood and CNS, or lung infection with high fever, chest pain, fluid. ~6% mortality; Hib vaccine (1988).

Helicobacter pylori

Peptic (gastric and duodenal) ulcers; associated with gastric cancer. Gram − spirillum that survives stomach acid by secreting urease, converting urea into basic ammonia to neutralize its environment; chronic inflammation of the mucosa follows → ulcers. Treated with antibiotics; a Koch's postulate exception (found in healthy people too).

Mycobacterium tuberculosis

Tuberculosis — chronic lung infection. Airborne droplet transmission; slow-growing; waxy mycolic acid cell wall lets it survive inside the macrophage phagolysosome. Infected macrophages are walled off into granulomas (Ghon's complex) that may rupture and spread; viable bacteria persist latently. Long-term combined antibiotics; typical secondary infection in AIDS.

Mycoplasma pneumoniae

Atypical or "walking" pneumonia. Spread by respiratory secretions. Has NO cell wall, so β-lactams are useless and it is slow-growing and hard to detect; attaches to and damages respiratory epithelium → least severe pneumonia with low-grade fever and cough. Self-limiting; no vaccine.

Naegleria fowleri

Primary amebic meningoencephalitis (PAM). Free-living ameba in warm fresh water; enters through the NOSE while swimming or diving, travels along the olfactory nerve through the cribriform plate into the brain and destroys brain tissue. Almost always fatal within days; not acquired by drinking water.

Neisseria gonorrhoeae

Gonorrhea. Gram − diplococcus; fimbriae attach it to and it invades epithelial cells of urethra, cervix and sometimes rectum → inflammation and pus. Males: painful urination, urethritis, discharge. Females: often less symptomatic (cervix only) → PID and infertility. Can spread to joints, heart, eyes, brain. Rising antibiotic resistance; no adaptive immunity built.

Neisseria meningitidis

Meningococcal meningitis. Gram − diplococcus carried in the throat, spread by respiratory secretions. Capsule and pili resist phagocytosis so it reaches blood and CNS; endotoxin causes a petechial rash that does not fade, plus fever and shock. Children <2 and college-age students; up to 80% mortality without drugs; vaccine covers 4 of 5 serotypes.

Pseudomonas aeruginosa

Opportunistic infections — burns and wounds, UTIs, otitis externa, chronic lung infection in cystic fibrosis. Gram − aerobe surviving on minimal nutrients in moist environments and hospital equipment. Forms biofilms (sticky EPS) that anchor it and shield it from antimicrobials and phagocytes; intrinsically resistant to many antibiotics and disinfectants.

Salmonella enterica

Salmonellosis (gastroenteritis); S. Typhi causes typhoid fever. Gram − rod; an INFECTION not an intoxication, so onset is delayed and fever is present. Transmitted from animals, feces-contaminated food, or poorly handled food (eggs, chicken). Penetrates intestinal mucosa — less invasive than Shigella — and endotoxin release drives fever; resolves in days with oral rehydration.

Shigella spp.

Shigellosis / bacillary dysentery. Gram − rod that uses invasins to infect intestinal cells and spread cell to cell; Shiga toxin worsens it → colon tissue damage, abscesses, dysentery (up to 20 bowel movements/day), possible kidney failure. Transmitted by fecal contamination person to person only — no animal transmission. Resolves with antibiotics.

Staphylococcus aureus

Boils, impetigo, toxic shock syndrome, staph food poisoning. Opportunistic normal flora spread by human-to-human contact. Coagulase blocks phagocytosis and complement; leukocidin kills phagocytes; superantigens (TSST-1) cause a cytokine storm → septic shock; neutralizes skin defensins; MRSA resistance. Food poisoning is an intoxication — heat-stable toxin survives 30 min boiling, onset 1–6 h.

Streptococcus pneumoniae

Pneumococcal pneumonia; also meningitis and otitis media. Gram +; spread by contact with respiratory secretions. Encapsulated with pili — the capsule resists phagocytosis and is the main virulence factor. High fever, chest pain, fluid in lungs; meningitis mortality ~30% in children and ~80% in elderly. Pneumococcal conjugate vaccine.

Streptococcus pyogenes

Group A Strep — strep throat, scarlet fever, impetigo, necrotizing fasciitis, bone inflammation. Non-enzymatic virulence: M protein prevents phagocytosis and complement activation; hyaluronic acid capsule disguises it. Enzymatic: streptolysins lyse RBCs (beta-hemolytic), streptokinases dissolve blood clots, hyaluronidase dissolves connective tissue so it spreads through tissue.

Treponema pallidum

Syphilis. Spirochete, sexually transmitted; replicates only inside a host so it is difficult to culture. Produces NO toxins — damage comes from increased inflammation. Primary: small hard painless chancre that ulcerates and sheds contagious fluid. Secondary: widespread, very contagious rash. Latent: symptoms subside, normally non-infectious. Tertiary (25% untreated): gummas damaging skin, aorta, nervous system.

Vibrio cholerae

Cholera. Gram − curved rod, alkaliphile; waterborne via untreated or poorly treated sewage. NON-invasive: colonizes the small intestine and secretes cholera toxin (A-B exotoxin) which locks adenylate cyclase on → cAMP rises → uncontrolled chloride and water secretion → "rice-water" stools and severe dehydration. Treated with oral rehydration.

Wuchereria bancrofti

Lymphatic filariasis, late stage elephantiasis. Nematode; larvae spread to humans by mosquito bites. Adult worms block lymphatic circulation, so lymph accumulates in tissue → grotesque swelling of the legs and other body parts and thickened skin. Early anti-helminthic medication; prevention is sanitation and mosquito control.