Flashcards in Gram (+) Rods Deck (42):
Spore forming aerobe, zoonosis with no vector, associated with cattle that can lead to a cutaneous disease with edematous eschar
Edema factor and lethal factor released from anthrax toxin cause the eschar
Patient presents with pneumonia. Upon chest xray, there is mediastinal widening. Patient was recently at major sporting event. If not treated within 48 hrs, this disease is almost invariably fatal.
Bacillus anthracis - mediastinal widening due to hemorrhagic lymphadenitis
Inhalational spores have potential for biowarfare agent
Spore forming aerobe, associated with Chinese restaurants, rapid onset vomiting and diarrhea due to preformed emetic toxin
Anaerobic, spore former, produces toxin that blocks release of glycine and GABA in spinal synapses, leaving excitatory neurons unopposed
Associated with dirty puncture wounds and progresses from lockjaw to diffuse rigid paralysis
What is the treatment of tetanus?
TIG (hyperimmune human globulin) to neutralize toxin + antibiotics (metronidazole or penicillin)
Floppy baby syndrome
Anaerobic, spore former, heat labile, produces toxin that blocks the release of ACh at the neuromuscular junction
Why shouldn't you treat botulism with antibiotics?
In adults: there is no active infection! Just ingested preformed toxin
In infants: antibiotics will lyse the bacteria, releasing toxin and causing a potentially fatal toxemia
Thankfully, there is a trivalent antitoxin available
Anaerobic, spore former, non motile, produces an alpha toxin that is a lecithinase which causes massive hemolysis and tissue destruction
Toxin identified by Nagler reaction
Traumatic accident, contamination of wound with soil, tense tissue, fever
Clostridium perfringens - gas gangrene
What is the treatment of gangrene due to Clostridium perfringens?
- delay closure of wound for as long as possible (since C. perfringens is anaerobic)
- clindamycin + penicillin
- hyperbaric chamber
Food poisoning, enterotoxin disrupts ion transport which causes a watery diarrhea that resolves within 24 hrs, associated with reheated meat dishes
Which is more common in the U.S., adult or infant botulism?
Anaerobic, spore former, normal flora of colon, toxins produced that are associated with antibiotic use and pseudomembranous colitis
Which antibiotics put patients at most risk for developing Clostridium difficile infection?
broad spectrum - clindamycin, cephalosporins, amoxicillin, ampicillin
What is the treatment for Clostridium difficile?
Anaerobic, spore-former, stormy fermentation in milk media, shows double zone of hemolysis
Most common cause of meningitis is a renal transplant or cancer patient
Aerobic, non spore former, beta hemolytic, facultative intracellular, tumbling motility, cold growth
What is the manifestation of transplacental transmission of listeria monocytogenes? Neonatal acquisition?
Transplacental: granulomatous infantisepticum (disseminated granulomas with central necrosis) - tell mom to stay away from deli meat and soft cheese!
Neonatal: septicemia and meningitis
Aerobic, non spore former, club-shaped, toxin produced that inhibits protein synthesis by interfering with elongation, toxoid vaccine, most commonly infects throat (gray pseudomembrane), heart (myocarditis), and nerve (recurrent laryngeal nerve palsy)
Grows gray to black colonies in V or L or "Chinese letter formation" on tellurite medium. Can distinguish toxigenic from non toxigenic strains with Elek test.
Toxin producing strains of corynebacterium are present in an individual due to?
transduction of toxin via a beta-prophage, and toxin is then produced by lysogeny
Anaerobic, branching rods, non-acid fast, normal flora in gingiva or female genital tract, grows in tissues with low oxygenation, colonies resemble molar tooth
Lumpy jaw, draining abscess with sulfur granules
How do brain abscesses due to Actinomyces differ from those due to Nocardia (both branching G+ rods)?
Nocardia: multiple foci
Aerobic, branching rod, partially acid fast, reservoir in soil or dust, causes a cavitary bronchopulmonary disease that looks very similar to TB
Aerobic, branching rod, partially acid fast, causes a cellulitis with a draining abscess and granules after traumatic implantation
What is the preferred treatment for Nocardia infection?
sulfonamides or TMP-SMX
(usually will show up as TB-like symptoms with choices of a bunch of TB drugs + sulfonamides... Pay close attention to description of partially acid fast or branching rods)
Acid fast, obligate aerobe, facultative intracellular, stains fluorescent apple green on Auramine-rhodamine stain, grows in 2-3 weeks on Lowenstein-Jensen medium, produces niacin, heat sensitive catalase
Describe the pathogenesis mechanisms for Mycobacterium tuberculosis
- Sulfatides that inhibit phagosome/lysosome fusion
- Cord factor that inhibits leukocyte migration and disrupts cellular respiration
- Tuberculin that causes a delayed Type IV HSN reaction and induces cell mediated immunity
- no toxins! All damage is done by immune system
Replication in alveolar macrophages (Ghon focus), transportation to regional lymph nodes (Ghon complex), granulomas formed to wall off organisms
Primary pulmonary TB
Reduction of host T cell immunity and erosion of granulomas into airway with potential for dissemination
Reactivational TB (when disseminated, "miliary")
Diagnosis of TB?
- PPD skin test, if positive proceed to CXR
- Microscopy of sputum
- slow growing culture
Cause of pulmonary infection in AIDS patients with CD4 counts < 50
M. avium-intracellulare (diagnosis nonchromogen)
M. kansasii (diagnosis photochromagen)
Cause of lymphadenitis from contaminated water sources that will cause a solitary cervical LN in kids
M. scrofulaceum (diagnosis scotochromogen)
Cause of soft tissue infection in tropical fish enthusiasts
M. marinum (diagnosis photochromagen)
Acid fast rod, obligate intracellular parasite, prefers cooler parts of body, transmitted via nasal discharge, causes a disease that leads to sensory loss
Lepromin test +, few organisms in tissue, causes granuloma formation and subsequent nerve damage, macular lesions
Tuberculoid leprosy - if strong CMI (TH1) is present
Lepromin test -, many organisms in tissue, causes nerve damage due to growth of bacteria in cells, nodular lesions, leonine facies
Lepromatous leprosy - if weak CMI (TH2) is present