Bacteria

Question 1

Campylobacter jejuni

Answer 1

C: Curved, gram(-) rod, microaerophile, grows at 42 C, oxidase(+), fastidious, zoonotic reservoir (poultry)

V: Adhesins attach to stomach, LPS induces inflammation, enterotoxin in some strains

P: Transmitted by ingestion of fecally-contaminated water or sick pets; attaches to lower small intestine, invasion induces inflammation, disease starts one or more days after ingestion

C: Cramps, diarrhea, fever;
Can lead to arthritis and Guillain-Barre syndrome

P/T: Good hygiene, no vaccine;
Fluid replacement in mild cases; Antimicrobials can reduce duration and severity

Question 2

Chlamydia trachomatis

Answer 2

C: Obligate intracellular, have LPS and membrane proteins but no PG layer; energy parasites

V: Intracellular so hard for immune system to reach; EB prevents fusion of endosomes with lysosomes

P: LPS antigen; initially grow in epithelium and inflammatory cells invade tissue, can have chronic inflammation, have tissue damage from host immune response

C: Males: urethral discharge, dysuria, epididymitis
Females: dysuria, cervicovaginal discharge, PID - can lead to infertility and ectopic pregnancy
LGV - ulcer, lymph nodes enlarge, can rupture, can have recto vaginal fistula, rectal damage

P/T:Often co-transmitted with gonorrhea; must use abxs that penetrate the eukaryotic cell
- macrolides (azithromyCin) or doxycycline

Question 3

Treponema pallidum

Answer 3

C:Spirochete, outer membrane lacks LPS but is otherwise G(-), microaerobes

V: Glycosaminoglycans that mimic host and evade host immunity

P: Penetrates skin/mucosa, causes lesion (chancre) and other skin lesions; tertiary disease causes gumma; can have CNS involvement in secondary or tertiary disease - tabes dorsalis; can involve cardiovascular system; can become latent and return later in life

C: Chancre on genitalia/mucosa; lesions on hands and feet; CNS involvement; gummas

P/T:Penicillin for primary or secondary, early latent; late latent and tertiary are hard to treat

Question 4

Rickettsia rickettsii

Answer 4

C:Atypical, G(-) but too small to stain, obligate intracellular; reservoir in ticks

V: Directs actin reorganization; phospholipases, proteases, and membrane peroxidation cause host cell damage; are energy parasites

P: Transmitted by Dermacentor ticks; philopodia, incubation period up to 12 days; have fever, malaise, severe headache, myalgia, vomiting, rash develops, can rupture endothelial cells of capillaries - causes the rash

C: rocky mountAin spotted fever. Fever, malaise, severe headache, GI symptoms, conjunctivitis, mental confusion, meningitis, respiratory difficulties, renal dysfunction, rash - spotted, mostly on extremities including palms

P/T:Doxycycline is effective during early stages of disease

Question 5

Borrelia burgdorferi

Answer 5

C:Spirochetes, structure similar to G(-), have endoflagella for motility; reservoir in rodents, deer, has sterols in cell membrane

V: Osps (surface proteins) for tropism, associated with plasmids; adhesins for tissue attachment

P: Ixodes tick vector (three stages in life cycle) - feed off infected reservoir; spirochetes attach to proteoglycan receptor in cells at site of bite, then spread from there. Needs to be attached for 48 hrs to transmit

C: Lyme disease - rash, fever, malaise → cranial neuropathy, meningitis, cardiac dysfunction → oligoarthritis, chronic derm syndromes

P/T:Prevent by avoiding ticks, finding them early; treat with doxycycline, amoxicillin, ceftriaxone

Question 6

Bacillus anthracis

Answer 6

C: G(+) rod, forms spores, non-hemolytic; medusa’s head/comet’s tail colonies on blood agar - box car appearance; reservoirs in sheep, cattle, goats

V: Capsule (PGA) - antiphagocytic; Edema toxin interferes with cell function- increase cAMP; Lethal toxin interferes with signal transduction- cleaves kinase

P: Infection occurs cutaneously or by inhalation; spores germinate then multiply and produce toxin, cause severe inflammation of lymph nodes; No person to person transmission

C: Cutaneous - pruritic papule at site, black eschar, usually painless, have enlarged lymph nodes at the region of infx; GI - N/V, fever, hematemesis;
Inhalational - flu-like illness, pleural effusion, mediastinal widening, hemorrhagic meningitis

P/T:Cutaneous - doxycycline or ciprofloxacin;
GI/Inhalational - doxy or cipro and 1-2 additional antibiotics;
PEP - 3 doses of vaccine and antibiotics;
Vaccine available

Question 7

Francisella tularensis

Answer 7

C: G(-) coccobacillus, facultative intracellular pathogen; reservoir in animals

V: Hemolytic agents; ATP binding cassette; pili to bind to host cells

P: Tick vector or can be aerosolized; disseminates from bite and invades other organs; no person to person transmission

C: Tularemia - Abrupt onset of fever, chills, headache, malaise, anorexia, fatigue; can progress to a number of syndromes; high death rate if untreated

P/T:Streptomycin or gentamicin; doxycycline, cipro, or chloramphenicol; no vaccine

Question 8

Yersinia pestis

Answer 8

C: G(-) bacillus, has bipolar staining, looks like safety pin; reservoir in rodents

V: Plasminogen activator (protease, coagulase) - coags flea gut so they feed all the time; Yersinia outer protein virulon (Yops) - type III secretion system; LPS

P: Flea regurgitates bacteria into human; disseminates from bite, can enter bloodstream or go to lymph nodes

C: Bubonic - fever, chills, weakness, headache, adenopathy
Pneumonic - fever, cough, difficulty breathing, bloody sputum, 50% mortality
Septicemic - blood stream infx, escapes lymph node

P/T:Streptomycin or gentamicin; doxy or cipro (alternative);
No vaccine

Question 9

Clostridium botulinum

Answer 9

C: G(+) bacillus, forms spores, anaerobic, found in soil throughout the world, can be foodborne

V: Exotoxin that blocks the release of acetylcholine, muscles can’t contract; spores are heat resistant

P: Not contagious; can be inhalational or ingestion; targets nerve synapse blocking release of Ach, blocking neuromuscular signal transmission

C: Bilateral symmetric descending acute paralysis (flaccid), cranial nerve dysfunction, fever, tachycardia, mental status change

P/T:Supportive care, anti-toxin from CDC; vaccine for special use

Question 10

Haemophilus influenza

Answer 10

C: G(-) pleomorphic coccobacilli; fastidious; grows on chocolate agar but not blood agar; both encapsulated and nonencapsulated

V: Polysaccharide capsules for evasion - Hib most important capsular strain;
Endotoxin (LOS) - adhesin, pili, inflammatory; IgA protease; obtain iron from heme/transferrin

P: Transmission through respiratory droplets; in the absence of protective antibody, the virus colonizes, infects, and disseminates

C: Pediatric - otitis media, sinusitis, epiglottitis, pneumonia, meningitis, bacteremia;
Adult - otitis media, sinusitis, meningitis rare, LRT infections (bronchitis, pneumonia)

P/T:Cephalosporins and B-lactams + B-lactamase inhibitors; therapy depends on site of infection (oral v. IV); Hib vaccine available

Question 11

Mycoplasma pneumoniae

Answer 11

C: No cell wall, has sterols in membrane, slow and difficult to grow, very small

V: Adhesions for attachment to cells; CARDS toxin causes epithelial damage; produces peroxide; induces inflammatory response

P: Transmission through respiratory droplets; colonizes epithelium but does not enter alveoli, aspiration into LRT causes bronchopneumonia

C: URT/LRT infections - fever, sore throat, malaise, cough; can have erythema multiforme (rash), hemolytic anemia, thrombotic thrombocytopenic purpura

P/T:Tetracyclines and macrolides are static; fluoroquinolones are cidal; abx may not be that helpful

Question 12

E. coli

Answer 12

C: G(-) rod, facultative anaerobe

V: Type 1 pili attach to mannose receptors (all species)

T: Sanitary and hygienic practices; use of antibiotics for symptomatic disease; abxs contraindicated in EHEC (seems to make it worse) - blood transfusion and kidney dialysis

Question 13

ETEC

Entero- toxigenic

Answer 13

C: G(-) rod, facultative anaerobe

V: Colonize intestine with unique pili (CFAI, II, III), toxins STa (heat stable) or LT (heat labile)

P: Colonize and multiply in small intestine, produce STa or LT, which increase intestinal fluid secretion

C: Watery diarrhea, food poisoning

Non-invasive

T: Sanitary and hygienic practices; use of antibiotics for symptomatic disease; abxs contraindicated in EHEC (seems to make it worse) - blood transfusion and kidney dialysis

Question 14

EPEC

Entero- pathogenic

Answer 14

C:
G(-) rod, facultative anaerobe

V: Pilus binds to lesions, TTSS, endotoxin

P: Form attaching and effacing lesions where effectors are injected into enterocytes causing watery diarrhea

C: Infant diarrhea in developing countries

Poorly invasive

T: Sanitary and hygienic practices; use of antibiotics for symptomatic disease; abxs contraindicated in EHEC (seems to make it worse) - blood transfusion and kidney dialysis

Question 15

EAEC

Entero- aggregative

Answer 15

C: G(-) rod, facultative anaerobe

V: EAST for aggregation; hemolysin, endotoxin

P: Adhere to enterocytes, increase mucous production trapping the bacteria in biofilm, cause watery discharge and inflammation

C: Chronic diarrhea in HIV+ pts, infant diarrhea, acute traveler’s diarrhea; may include mild fever

Not invasive

T: Sanitary and hygienic practices; use of antibiotics for symptomatic disease; abxs contraindicated in EHEC (seems to make it worse) - blood transfusion and kidney dialysis

Question 16

EIEC

Enteroinvasive

Answer 16

C: G(-) rod, facultative anaerobe

V: Common pili and afimbrial adhesions; TTSS, endotoxin

P nvade enterocytes, lyse endocytic vesicles and escape into cytoplasm, multiply and cause destruction

C: Watery diarrhea, sometimes with blood and fecal leukocytes

Very invasive

T: Sanitary and hygienic practices; use of antibiotics for symptomatic disease; abxs contraindicated in EHEC (seems to make it worse) - blood transfusion and kidney dialysis

Question 17

EHEC

Entero- hemorrhagic

Answer 17

C: G(-) rod, facultative anaerobe

V: Shiga toxin (Stx), adhesin molecules

P: Transmitted by ingestion or contact with animals; close adherence to intimin, produce Stx, causing colonic damage, absorbed by circulation and damages kidney

C: Hemorrhagic colitis - bloody stool with little or no fever; kidney failure in children (hemolytic uremic syndrome (HUS))

Poorly invasive

T: Sanitary and hygienic practices; use of antibiotics for symptomatic disease; abxs contraindicated in EHEC (seems to make it worse) - blood transfusion and kidney dialysis

Question 18

Helicobacter pylori

Answer 18

C: G(-) curved rod, motile, microaerophilic, grows better at 37C, urease(+)

V: Produces urease to raise local pH in stomach; uses flagella to move into mucus layer where pH is higher; VacA damages stomach cells; LPS causes inflammation

P: Initial mild GI disease (N/V), then develop mild inflammation that may persist (chronic gastritis); ~1% of colonized people develop duodenal or gastric ulcers; can also develop gastric lymphoma or gastric cancer

C: N/V, chronic gastritis, ulcers, gastric cancer

P/T:Antimicrobial (clarithromycin and bismuth salts) and acid blocker (omeprazole)

Question 19

Clostridium difficile

Answer 19

C: G(+) rod, forms spores, produces toxin, anaerobic

V: Toxin A - disrupts actin cytoskeleton, causes inflammation and leakiness; Toxin B - same as toxin A; Binary toxin - adds ADP-ribose onto actin

P: Exposure → colonization → abx change gut flora → C. diff infx, toxin production → diarrhea
Toxin A interferes with actin and makes cells leaky; Toxin B similar to A, also cytopathic effects; Binary toxin also similar

C: Can be asymptomatic, diarrhea, toxic megacolon

Detect fecal leukocytes

P/T:Metronidazole or oral vanco; surgery for toxic megacolon

Question 20

VRE

Answer 20

C: G(+) coccus (occurs singly or in pairs or chains); facultative anaerobes

P: Colonize skin, can invade bloodstream or cause UTI

P/T:Linezolid and daptomycins

Question 21

MRSA

Answer 21

C: G(+) coccus in clusters; coagulase(+)

P: Colonize skin, then can infect through lines, prostheses, etc.

C: Bloodstream infection, wound infections, line infections

P/T:Ceftaroline, Vanco, Linezolid, TMP/SMX, Clinda

Question 22

Klebsiella

Answer 22

C: G(-) bacillus; aerobic or anaerobic; normal inhabitant of GI tract

V: Mucoid and resists phagocytosis; can be MDR, ESBL

P: Colonizes skin then enters the body via a number of mechanisms

C: Bloodstream infection, pneumonia, UTI

P/T:ESBL treated with carbapenems, fluoroquinolones, aminoglycosides

Question 23

Acinobacter baumannii

Answer 23

C: G(-) rod, aerobic

V: Resistant to desiccation, readily acquires abx resistance genes; often MDR; endotoxin

P: Colonizes skin then can infect the body when opportunity strikes

C: Ventilator-associated pneumonia

P/T:Often inherently MDR, difficult to treat

Question 24

Shigella spp.

Answer 24

C: G(-) rod, facultative anaerobe, oxidase(-), lactose(-), do not make H2S, non-motile

V: LPS, Ipa proteins (invasion), Mxi-Spa proteins (translocon), IcsA - polymerizes actin for movement, IcsB - helps shed double membrane after spread to next cell, shiga toxin

P: Ingestion, then Ipa and Mxi -Spa proteins made, forms TTSS needle, Ipa proteins cause membrane ruffling, endocytosis of rod by M cells; kill macrophages associated with M cells; replication; in cytoplasm IcsA moves it around and into next cell, IcsB helps it escape endosome; shiga toxin causes dysentery

C: Mild diarrhea, fever, dysentery, death can occur from fluid/electrolyte imbalance; inflammation causes presence of fecal leukocytes

P/T:Hygiene for prevention; abx reduce severity and duration of disease; balance fluids/electrolytes

Question 25

Neisseria meningitidis

Answer 25

C: G(-) diplococci, oxidase(+), non-motile, selected for on Thayer- Martin media, reservoir is exclusively human

V: Capsule - avoidance of immune response; 
Pili - attachment, antigenic variation; 
LOS - inflammatory;
IgA protease - inhibits opsonization;
Complement binding proteins	

P: Colonizes the nasopharynx, then when change in immune fxn or normal flora, it becomes infectious, invades epithelium and vascular space, rapidly multiplies, disseminates to brain, skin, joints, bones

C: High fever, hypotension, headache, stiff neck, rash (petechiae or purpura)

Can progress quickly to death

P/T:High-dose PCN or cephalosporins

Vaccination available for A,C,Y, and W135 strains, no vaccine for B serotype

Question 26

Streptococcus pyogenes

Answer 26

C: G(+) cocci in pairs or chains, non-motile, catalase(-), called Group A strep or Beta-hemolytic strep, sensitive to Bacitracin; reservoir is humans

V: M protein - adhesion and immune evasion;
Lipoteichoic acid - adhesion;
Hyaluronic acid capsule - inhibits phagocytosis, molecular mimicry;
C5a peptidase - blocks complement;
Toxins - hemolysin, streptokinase, hyaluronidase, erythrogenic toxin

P: Spread by fomites or direct contact; colonizes pharynx and can then infect; can spread and cause pyogenic infection (causes nec fasc); toxogenic infection - toxins secreted cause damage - scarlet fever, TSS;
Non-suppurative immunologic sequelae - rheumatic fever, post-streptococcal glomerulonephritis (PSGN)

C: Sore throat (strep throat), can cause nec fasc - infection along fascial planes;
rheumatic fever - arthritis, carditis;
PSGN - hematuria, edema, hypertension;
Scarlet fever - diffuse sandpaper rash, hypotension;
TSS - hypotension, end-organ failure, erythroderma

P/T:Penicillin and other B-lactams (some emergence of macrolide resistance)

No vaccine

Question 27

streptcoccus pneumoniae

Answer 27

C: G(+) cocci, alpha- hemolytic, catalase(-), facultatively anaerobic, have distinctive lancet shape, occurs singly or in pairs, thick capsule, human is only reservoir, carried more frequently by the young

V: Neuraminidase - adherence;
IgA protease - cleaves Ab to evade host immunity;
LTA - promotes inflammation;
Capsule - evasion;
Pneumolysin - damage, inflammation, spread

P: Transmitted by respiratory droplets or contact; first colonize, move to lower airway, enter bloodstream from pharynx or lung, cause local infection of respiratory tree and can become systemic; in lungs it destroys ciliated cells and compromises the mucociliary elevator

C: Respiratory - otitis media, sinusitis, conjunctivitis, pneumonia
Disseminated - bacteremia, meningitis, peritonitis, septic arthritis, osteomyelitis

P/T:B-lactams, but some resistance issues

Vaccine available (made from polysaccharide capsule conjugated with carrier protein)

Question 28

Staphylococcus aureus

Answer 28

C: G(+) cocci in clusters, beta-hemolytic, catalase(+), coagulase(+), golden on chocolate agar, has capsule, reservoir in humans

V: Protein A, clumping factors, collagen binding protein, fibronectin binding protein for adherence; capsule to evade phagocytosis; LTA for inflammation; resistance molecules (mecA in MRSA)

P: Transmitted by contact or fomites; has many methods of infection

Resistance is a major concern - MRSA (USA300 strain is community acquired)

C: Skin - impetigo, folliculitis, furuncles, cellulitis, fasciitis;
Toxic shock syndrome - fever, diffuse rash, hypotension, multiorgan system dysfunction;
Device infxs - indwelling central lines, urinary catheters, surgical wound
Disseminated - septicemia, endocarditis

P/T:Based on resistance characteristics;
MRSA resistant to penicillins, cephalosporins;

See increased use of vancomycin, linezolid, daptomycin;
Prevention

Question 29

Neisseria gonorrhoeae

Answer 29

C: G(-) diplococci, oxidase(+), human reservoir

V: Pili - attachment, widely variable;
Opa proteins - adherence, phase/ antigenic variation;
LOS - variation

P: Sexually transmitted or in utero; attaches to columnar epithelial cells, penetrates into submucosal tissue; pili are highly variable (antigenic and phase), so there can be no immunity to reinfx

C: Males - acute urethritis, purulent urethral discharge, dysuria;
Females - cervicitis, urethritis, PID progression

P/T:Ceftriaxone

No vaccine due to antigenic and phase variation

Question 30

LIsteria monocytogenes

Answer 30

C: G(+) rod, facultative anaerobe, catalase(+), oxidase(-), incomplete beta-hemolysis, small, intracellular, optimal growth at 30-37C but can grow at 4C, human reservoir

V: Listeriolysin O - breaks open phagosomes so the bacteria can enter the cytoplasm; actA - forms actin tail and propels the bacteria around

P: Can be foodborne or passed from mother to fetus (crosses placenta), causes neonatal meningitis; multiplies in liver, then gets into bloodstream and can lead to septicemia or meningitis

C: Pregnancy transmitted - fever during pregnancy, can cause stillbirth, abortion, premature labor, neonatal meningitis

Foodborne - fever, GI symptoms

P/T: Ampicillin, TMP/SMX

Prevention by examining meat, avoiding certain foods when pregnant

Question 31

Legionella pneumophila

Answer 31

C: G(-) rod or coccobacillus, facultative intracellular, aerobic, fastidious, single flagellum; natural habitat in bodies of water, lives in amoeba and protozoa, biofilms

V: Chlorine-tolerant; inhibition of phago- lysosome fusion, makes it look like ER by recruiting ER vesicles; Type IV secretion system to prevent fusion

P: No human-human transmission; aerosolized in cooling systems, water systems, causes respiratory tract symptoms, sometimes GI symptoms

C: Legionnaires’ disease - pneumonia;
Pontiac fever - acute febrile illness without pneumonia, less dangerous
Other - cough, fever, diarrhea in some cases

P/T: Macrolides, quinolones, tetracyclines

Question 32

Pseudomonas aeruginosa

Answer 32

C: G(-) rod, aerobic, motile, oxidase(+), makes blue-green pigments, highly abx resistant, extracellular, opportunistic, ubiquitous in the environment

V: Exotoxin A - necrosis;
Proteases, elastase for tissue damage; leucocidin to kill WBCs; phospholipase C - hemolysin; endotoxin - shock; capsule - biofilm formation, antiphagocytic; Pili - adhesion

P: Usually can’t penetrate the epithelium, invades wounds, surgical incisions, burns; extracellular pathogen that produces toxin/other virulence factors to cause disease

C: In healthy people WBCs can usually resist disease; Opportunistic; Septicemic infections, can cause shock, often has high mortality rates

Prevention via hygiene, good wound care

P/T: Piperacillin, Cefepime, Ceftazidime, Imipenem, Meropenem, Doripenem, Aztreonam, Aminoglycosides, Ciprofloxacin, Levofloxacin, Polymyxins

Question 33

Mycobacterium tuberculosis

Answer 33

C: Acid-fast bacilli, slow growing, has waxy and lipid rich cell wall, only a little PG

Immune response - IFN-g, TNF-a, IL-12, IL-6 - important to activate macrophages

V: Mycolic acid, lipids, lipoarabinomannan, cytolysin, adhesin/invasin genes, secretion systems (ESX loci); prevention of phago- lysosome fusion; inhibits acidification of phagosome; resistant to ROSs; down- regulates MHC II presentation

P: Transmitted through aerosolization, infects alveolar macrophages, causes inflammatory signals in infected cells, have hematogenous spread of bacteria to other organs, formation of necrotic granuloma with recruitment of monocytes and lymphocytes; leads to latent infection, can later reactivate

C: Pulmonary - following inhalation, have lung destruction, hemoptysis, wasting;
Extrapulmonary - spread to other organs after pulmonary infection;
Miliary - spreads through lungs or throughout body, often in immunocompromised;
Commonly cough, fever, difficulty breathing

P/T: Rifampin (6 mo)
Isoniazid (6 mo)
Pyrazinamide (2)
Ethambutol (2)

Multidrug resistant and extremely drug resistant strains becoming more common

BCG vaccine (results mixed)

Question 34

Mycobacterium leprae

Answer 34

C: Acid-fast bacilli, armadillo is reservoir, replicates best at lower temps (32-34C)

V: Mycolic acid, lipids in cell wall, capsule

Little else is known about pathogenesis/ virulence factors because cannot be cultivated in lab

P: Respiratory transmission from nasal secretions; infects macrophages and Schwann cells, causes damage in peripheral nerves;

Lepromatous - causes Th2 T cell response

Tuberculoid - causes Th1 T cell response

C: Lepromatous - high bacterial load, few T cells, foamy macrophages, skin nodules, nerve enlargement and impairment, involvement of nasal mucosa;
Tuberculoid - low bacterial load, many T cells, granulomas, few flat lesions, hypopigmented, nerve impairment

P/T: Diagnosis by skin biopsy

Rifampin, Dapsone
(1.5-2 years!)

Nerve damage cannot be reversed

Question 35

Mycobacterium avium-intracellulare

Answer 35

C: Acid fast bacilli

P: Common opportunistic pathogen in AIDS patients

C: Chronic pulmonary disease

P/T: Difficult to treat

Question 36

Mycobacterium marinum

Answer 36

C: Acid fast bacilli, marine organism

P: Grows at low temps

C: Causes lesion on hands

P/T: Difficult to treat

Question 37

Mycobacterium ulcerans

Answer 37

C: Acid fast bacilli

V: Toxin

P: Necrotizes skin

C: Buruli ulcer

P/T: Difficult to treat

Question 38

Bacteroides like spp.

Answer 38

C: G(-) rods, anaerobic, normal flora of vagina, colon, mouth

V: Capsule - antiphagocytic, LPS, some strains make enterotoxin, proteases

P: Cause endogenou infxs, breech epithelium via surgery, wounds, ruptures, need low tissue redox for growth; not contagious infections

C: B. fragilis - peritonitis and abscess;
Prevotella bivia - PID
P. melaninogenica - respiratory tract infxs;
Bacteremia

P/T: Surgical drainage of abscesses, abx for anaerobes, like Metronidazole

Question 39

Clostridium perfringens/septicum (histotoxic)

Answer 39

C: G(+) rods, spore- forming, anaerobic

V: Alpha toxin - phospholipase C that disrupts mammalian plasma membranes

P: Causes endogenous and exogenous infxs; result of spores getting into wound, needs low tissue redox

C: Gas gangrene, anaerobic cellulitis, simple wound infx, bacteremia, food poisoning

P/T: Removal of affected tissue, abx; prevention w/ good wound care

Question 40

Clostridium tetani

Answer 40

C: G(+) rods, spore- forming, anaerobic

V: Tetanus neurotoxin (tetanospasmin) - inhibits release of inhibitory neurotransmitters (GABA, glycine)

P: Implantation of spores into wound or during childbirth; if tissue redox low, spores germinate and make toxin, toxin travels along nerves into CNS

C: Uncontrolled muscle contraction, lockjaw

P/T: Antitoxin, assisted ventilation, prevention with toxoid vaccine

Question 41

corynebacterium diphtheriae

Answer 41

C: G(+) club-shaped rod, form palisades or “Chinese letter” formations, grows on tellurite salts; reservoir in humans

V: Adhesins for colonization, Diphtheria toxin - inhibits host cell protein synthesis by making EF-2 nonfxnal, cells die; expression of diphtheria toxin occurs only in low iron environments

P: Transmitted by aerosol droplets; colonizes nasopharynx or skin, produces toxin, localized necrosis develops, forms pseudomembrane in throat, can enlarge and block respiration; bacteria is non-invasive but toxin can disseminate to kidneys, heart, CNS

C: Malaise, sore throat, enlarged cervical lymph nodes

Enlargement of pseudomembrane can block the airway and lead to suffocation, especially in children

P/T: Antitoxin essential, can use abx to kill bacteria (penicillin)

Vaccine available (part of DPT)

Question 42

Vibrio chloerae

Answer 42

C: G(-) comma-shaped rods, highly motile, oxidase(+), facultative anaerobes, halotolerant, grow on TCBS agar (contains bile salts); native to estuary waters

V: Cholera toxin - increases cAMP in intestinal cells, causing massive fluid and electrolyte loss; Toxin-coregulated pilus - essential adhesin for colonization of intestinal epithelium

P: Transmitted via ingestion of contaminated food/ water; survives acidity of stomach due to biofilm; colonize intestinal mucosa, virulence factor expression is turned on, produces cholera toxin, cAMP levels increase, massive fluid/electrolyte loss

C: Diarrhea - pale yellow, with flecks of white mucous material - “rice water stool”; can produce ~1 L/hour;
Death from dehydration, shock, cardiac problems

O1 and O139 serotypes associated with epidemic/ pandemic spread

P/T: Treat with restoration of fluids/electrolytes; IV fluids in severe cases;
Prevention with good hygiene, water treatment; vaccines in testing, not licenced in US

Question 43

Salmonella nontyphoid

Answer 43

C: G(-) rods, lactose(-), motile, produce H2S, facultative anaerobes;
Zoonotic reservoir (food animals, pets)	

V: PhoP/PhoQ-survival inside of phagocytes; TTSS, Inv/Spa for entry; PagC for anti- microbial resistance

P: Ingestion, invasion via membrane ruffling, released into lamina propria, inflammatory response

C: Fever, cramps, diarrhea (bloody); spreads past lamina propria in compromised pts, causes septicemia, osteomyelitis

P/T: Treat symptoms, antimicrobial therapy for septic pts

Question 44

salmonella typhi

Answer 44

C: G(-) rods, lactose(-), motile, produce H2S, facultative anaerobes;

Human reservoir only

V: Vi antigen - capsular polysaccharide

Same other antigens as above

P: Fecal-oral route transmission; same as for nontyphoid Salmonella, but disseminates from intestines, moves to reticuloendothelial tissue, enter blood and bile, can trigger septic shock/high fever, can perforate bowel

C: More mild GI symptoms initially, but followed by septic shock, fever, diarrhea, granuloma/ abscess formation in intestines leading to peritonitis; abdominal rose spots

P/T: Removal of gall- stones to prevent carrier state; treat septic pts with antimicrobials

Question 45

Bordetella pertussis

Answer 45

C: G(-) coccobacillus, aerobe, nutritionally fastidious

V: Pertussis toxin - increases cAMP and disrupts signaling; hemagglutinin and pili to adhere; adenylate cyclase toxin also increases cAMP; tracheal cytotoxin kills ciliated cells; heat-labile toxin - local damage

P: Highly communicable; respiratory transmission; impair mucociliary elevator and cough is easily triggered; virulence gene expression regulated by two component system (Bvg system)

C: Whooping cough; tracheitis and bronchitis; can have neurologic consequences (convulsions)

P/T: DTaP vaccine - now acellular for less side effects, but maybe not as effective as whole cell vaccine