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Flashcards in Gram (-) Rods Deck (60):

Inflammatory diarrhea (blood and pus), oxidase +, gull's wings, low infectious dose, grows at 42C, transmitted from poultry

Campylobacter jejuni


Most common cause of bacterial gastroenteritis (direct infection of GI) in U.S.

Campylobacter jejuni (more frequent than salmonella and shigella combined)


Potential complications of C. jejuni infection?

- most often self-limiting (tx is supportive)
- Guillain Barre syndrome - accounts for 1/3 of GBS in U.S., cross reactivity with neural tissues
- Reactive arthritis


Oxidase +, UREASE +, microaerophilic, grows at 37C, causes chronic gastritis and duodenal ulcers

Helicobacter pylori


Type I carcinogen, causes gastric adenocarcinoma, MALT-oma, or B cell lymphoma

Helicobacter pylori


Associated with consumption of undercooked or raw seafood

Vibrio parahaemolyticus or vulnificus

- V. vulnificus also associated with a rapidly spreading cellulitis


Noninflammatory diarrhea, oxidase +, shooting star motility, growth on alkaline TCBS, high infectious dose, human reservoir with fecal oral spread, associated with natural disasters and standing water

Vibrio cholerae


Describe how cholera toxin works

- activates adenylate cyclase (Gs)
- increases cAMP
- efflux of Cl and H20


Ricewater stool with tremendous fluid loss, must replace fluids and treatment with doxycycline or ciprofloxacin shortens disease course

Vibrio cholerae


Gastroenteritis, non-lactose fermenter, motile H2S producer

Salmonella (think salmon swim upstream/are motile)

- compare with Shigella, which is a non lactose fermenter but nonmotile, non H2S producer!


What are common features of all members of Enterobacteriaceae?

- facultative anaerobes
- ferment glucose
- Oxidase (-)
- catalase +
- reduce nitrates to nitrites


You grow a MacConkey agar plate and see pink colonies. What does this mean and what could these be?

- MacConkey agar differentiates lactose fermentation
- pink = fermenters, colorless = nonfermenters
- Lactose fermenters are Escherichia, Klebsiella, Enterobacter, and Citrobacter


Oxidase (-), lactose fermenter, virulence associated with P pili, most common cause of UTI

Escherichia coli


Oxidase (-), lactose fermenter, K1 serotype (aka capsule), contamination during birth, second most common cause of neonatal meningitis

Escherichia coli


Mechanism that E. coli can cause septicemia

LPS lipid A endotoxin


Mechanism that ETEC causes diarrhea

- LT toxin stimulates adenylate cyclase, increases cAMP, and causes efflux of Cl and H20 (like cholera)
- attachment is also an important factor, because otherwise the massive amounts of diarrhea would just flush the bacteria out


Second most common cause of infantile diarrhea

EPEC (p = pathogenic or pediatric)
- important adherence to M cells to cause effacement of brush border


Only cause of inflammatory diarrhea in the Escherichia genus

EIEC - invades large bowel similar to shigella


Diarrhea that is bloody but non-inflammatory, toxin works by interfering with 60S ribosomal subunit and decreasing protein synthesis, does not ferment sorbitol (differs from others in genus this way), can progress to HUS

EHEC O157:H7


Enterobacteriaceae, lactose fermenter, oxidase (-), non foul smelling sputum in an alcoholic with pneumonia

Klebsiella pneumoniae

- non foul smelling differentiates from anaerobic aspiration pneumonia, which also occurs in alcoholics and will smell
- Extras: sputum is described as currant jelly and Klebsiella has a capsule


Enterobacteriaceae (facultative anaerobe), non lactose fermenter, nonmotile, non H2S producer, extremely low infectious dose (1-10), diarrhea that starts watery and progresses to bloody


S. sonnei is most common in U.S.
S. dysenteriae is most common in developing countries and produces the most severe disease


Describe the different mechanisms of pathogenesis seen with Shigella

1) Endotoxin - inflammation
2) Invasion of M cells - actin jet trails to move laterally, avoid immune system and produce shallow ulcers
3) Shiga toxin - inhibits protein synthesis by clipping 60S ribosomal subunit (similar to EHEC)


Enterobacteriaceae (facultative anaerobe), non lactose fermenter, non H2S producer, associated with drinking unpasteurized milk in cold climates, causes different presentations based on age

Yersinia enterocolitica

- exhibits cold growth, motile at 25C
- very young: febrile diarrhea
- older kids/young adults: pseudoappendicitis
- adults: enterocolitis with reactive arthritis


Enterobacteriaceae (facultative anaerobe), non lactose fermenter, non H2S producer, coagulase positive, U.S. Southwest

Yersinia pestis


What are the two disease presentations caused by Yersinia pestis?

A) Bubonic plague - flea bite, rapidly increasing fever, regional buboes, conjunctivitis, DIC
B) Pneumonic plague - inhalation of organisms, septic pulmonary emboli, highly contagious and has potential as biowarfare agent


Pathogenesis includes coagulase, endotoxin, exotoxin, F-1 envelope antigen, and Type III secretion system. Appears as a bipolar rod or safety pin on staining. Vaccine available to high risk populations.

Yersinia pestis


Enterobacteriaceae (facultative anaerobe), non lactose fermenter, highly motile with swarming motility, UREASE +, causes UTIs and kidney stones (staghorn calculi)

Proteus mirabilis/vulgaris


Enterobacteriaceae, non lactose fermenter, motile, more than 2400 serotypes based on O antigen


- high infectious doses needed, as organism is acid sensitive
- Typhi species only in humans; non typhi species transmitted in chicken products and reptiles


Patient presents with fever, abdominal pain, rose spots, fluctuating diarrhea and constipation, and positive Widal test. What bug is this, what disease does it cause, and where does it hide chronically?

Salmonella enterica subsp. typhi
- Causes typhoid fever
- Lies in gall bladder of carriers

- Widal test: agglutination of Abs to O, Vi, H antigens in patient's serum


How does Salmonella typhi resist being killed by macrophages?

- decreases the fusion of lysosomes with phagosomes
- defensins provide protection
- Vi capsular antigen survives complement-mediated killing


How does Salmonella enteritidis/typhimurium cause diarrhea?

- invades mucosa, causing inflammation and increase of cAMP


Osteomyelitis in a patient with sickle cell disease

- Salmonella, more specifically choleraesuis, paratyphi, dublin, or typhi


Aerobic, facultative intracellular zoonosis, Dermacentor tick vector, reservoir in rabbits, ulceroglandular or pneumonic disease treated with streptomycin

Francisella tularensis


Aerobic, facultative intracellular zoonosis, no vector, usually due to ingesting unpasteurized dairy products or direct contact with animal. Disease is characterized by undulating fevers and profuse sweating. Name the potential pathogens and associated livestock.


B. abortus - cattle
B. melitensis - goats
B. suis - pigs


Facultative anaerobe with capsule, resides in human nasopharynx and is common cause of meningitis, epiglottitis, or otitis media in unvaccinated children

Haemophilus influenzae

vaccine is against type b capsule and induces a T-cell dependent response - will need boosters


What are the main virulence factors of Haemophilus influenzae? What are the requirements to grow?

VFs: A) polysaccharide capsule (use latex particle agglutination to detect)
B) IgA protease

Growth Reqs: chocolate agar, because missing X and V factors to lyse blood (can satellite grow around S. aureus)


Facultative anaerobe, transmitted via sexual contact, presents with soft, painful chancre

Haemophilis ducreyi (chancroid)


Female presents with thin gray vaginal discharge. She recently was on a course of antibiotics. Vaginal pH is 5 and the whiff test is positive.

Bacterial vaginosis, due to overgrowth of Gardnerella vaginalis (facultative anaerobe)

- reduction of lactobacillus allows vaginal pH to increase >4.5 and normal flora of G. vaginalis flourishes


Facultative anaerobe, causes vaginal discharge, positive whiff test, not sexually transmitted, clue cells present on smear

Gardnerella vaginalis


Facultative anaerobe, associated with rapidly spreading cellulitis and lymphadenitis following a cat bite, prophylaxis and treatment with amoxicillin/clavulanate

Pasturella multocida


Associated with cat scratch fever in immunocompetant and bacillary angiomatosis in immunosuppressed

Bartonella henselae


Guy on the street takes bath salts, then takes a bite out of innocent bystander. Innocent bystander comes to see you after developing a cellulitis. You culture the wound and the next morning the agar is corroded and smells like bleach.

Eikenella corrodens


Cellulitis associated with dog bite wounds and an overwhelming sepsis if obtained in the absence of a spleen

Capnocytophaga canimorsus


Fastidious rods that are part of normal flora and are the most common cause of G(-) endocarditis in non-IV drug users, difficult to diagnose, treat with cephalosporins or fluoroquinolones

HACEK Group Infection:
Haemophilus aphrophilus
Actinobacillus actinomycetemcomitans
Cardiobacterium hominis
Eikenella corrodens
Kingella kingae


Anaerobic, normal colon flora, VFs include a modified LPS with reduced activity and an antiphagocytic capsule, associated with abdominal trauma or surgery, causes septicemia, peritonitis, or abscess formation

Bacteroides fragilis


Prophylactic antibiotic regimen for anyone undergoing GI surgery

Metronidazole, clindamycin, or cefoxitin

Bacteroides fragilis has a wide range of antibiotic resistance, so prophylactic treatment is necessary


Aerobic, oxidase positive, catalase positive, ubiquitous in water, with slime layer capsule, blue-green pyocyanin, sweet odor, non-lactose fermenting, causes GI distress in healthy people or cellulitis in burn patients

Pseudomonas aeruginosa


What are the virulence factors of Pseudomonas aeruginosa?

Endotoxin, exotoxin for eEF-2 that inhibits protein synthesis (like diptheria toxin), capsule slime layer


Aerobic, gram stains poorly, aerosol transmission, requires cysteine and iron to grow, facultative intracellular, associated with elderly smoker/drinker that is immunosuppressed, atypical pneumonia

Legionella pneumophila


What are the two diseases Legionella pneumophila can present as?

1) Legionairre's - atypical pneumonia, mental confusion, diarrhea, can be severe and fatal
2) Pontiac Fever - much milder pneumonia with full recovery


Strict aerobe, reservoir is vaccinated humans, transmitted by respiratory droplets, damages respiratory epithelium via adenylate cyclase toxin, tracheal cytotoxin, endotoxin, and its namesake toxin which also increases adenylate cyclase

Bordetella pertussis, the causative agent of whooping cough

Pertussis toxin ribosylates Gi, which promotes lymphocytosis, induces hypoglycemia, blocks immune effector cells, and increases sensitivity to histamine


During which stage of pertussis infection is bacterial culture most likely to grow?

Catarrhal Stage, when symptoms are reminiscent of the common cold and nonspecific to whooping cough

Ability to culture bacteria declines as disease progresses

Culture on Regan-Lowe media


Spirochete with axial filaments, obligate pathogen (cannot culture), transmitted sexually or across the placenta, three distinct stages plus a latent period, visualized by darkfield microscopy, screen with VDRL and confirm with FTA-ABS

Treponema pallidum


Baby of IV drug user - 8th nerve damage, notched (Hutchinson) teeth, tabes dorsalis, rhinitis with infectious secretions

Congenital syphilis


Name the stages of syphilis and their hallmark symptoms

1) Primary: nontender chancre that heals spontaneously
2) Secondary: diffuse maculopapular rash that is infectious, patchy alopecia, condylomata lata
3) Latency
4) Tertiary: gummas, aortitis, CNS inflammation


What is the treatment for syphilis and what is a potential reaction to treatment?

Treatment - benzathine penicillin (long acting)

Reaction - Jarish-Herxheimer, may occur in successful treatment of any spirochete as bacteria is lysed and LPS released. Fever, hypotension, rigors.


Spirochete, microaerophilic, difficult to culture, reservoir in mice or deer, vector in Ixodes tick, spreads via bloodstream to involve heart, joint, and CNS

Borrelia burgdorferi


Describe the stages of lyme disease

Stage 1: flu-like symptoms, erythema migrans
Stage 2: Worsening flu-like symptoms
Stage 3: Bell palsy, arrhythmias, myocarditis, arthritis (due to immune complexes), extreme fatigue


Spirochete, tight terminal hooks, aerobe, seen on darkfield microscopy, zoonosis, causes an influenza like disease that can rapidly progress to involve liver and kidney if not treated

Leptospira interrogans, causing Leptospirosis due to contact with animal urine in water


What is Weil disease?

Icteric leptospirosis with renal failure and myocarditis