Gram (-) Rods Flashcards
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
Shigella
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
Salmonella
- 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?
- NO TOXIN!
- 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.
Brucella
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
