Other Gram Positives Flashcards
Family of Clostridium bacteria are all _(3 characteristics)
All form spores • All obligate anaerobes • All form toxins
Clostridium tetani
Classic scenario & symptoms:
what does it do and how?
Classic scenario: barefoot on rusty/dirty nail or splinter
Classic symptoms • Lockjaw (trismus) • Risus sardonicus (forced grin due to spastic facial muscles)
Tetanus toxin produced (tetanospasmin) • Travels to spinal cord • Blocks glycine and GABA release by inhibitory neurons
“Renshaw cells:” inhibitory spinal cord interneurons
Clostridium tetani Treatment & Treatment
Treatment for tetanus
Wound debridement • Metronidazole • Tetanus immune globulin (binds circulating toxin) • Benzos or neuromuscular blockers until toxin wears off
Tetanus toxoid used for vaccination
Clostridium botulinum
spores are:
toxin does what?
Heat-resistant spores
Botulinum toxin • Works at neuromuscular junctions • Prevents Ach release (no muscle contraction) • Result: Floppy muscles (flaccid paralysis)
gene for toxin carried by bacteriophages
3 types of Botulism
symptoms:
Food (toxin ingestion; usually adults)
Undercooked food • Canned food: anaerobic environment promotes growth • Watch for multiple sick adults after a meal
Infant (spores) • Ingestion of spores → growth in infant intestine • Watch for contaminated honey!
Wound (bacterial growth) • Infection with C. botulinum
Symptoms: 3 D’s • Diplopia, dysphagia, dysphonia
Botulism Treatment & diagnosis
Diagnosis: • Often clinical • Spores and toxins sometimes detected in stool
Treatment: • Antitoxin blocks circulating toxin • Cannot block toxin already in nerves • Supportive care → toxin washout
Clostridium perfringens
causes:
toxin:
Infects dirty wounds (gas gangrene) & causes food poisoning (undercooked meats) • Spores ingested → produce toxin • Late onset (8-22hrs) watery diarrhea • Contrast with S. aureus/B. cereus (preformed toxin) which also produce watery diarrhea but much quicker onset
Alpha toxin
Destroys muscle tissue and causes hemolysis • Phospholipase that acts on lecithin (lecithinase) • Degrades phospholipids in cell membranes
Clostridium difficile
what does it do and when?
Ubiquitous spores in nature including soil
Ingestion not harmful with normal GI flora because Colonic flora prevent overgrowth of C. diff
Causes antibiotic-associated colitis.pseudomembranous colitis • Antibiotics alter normal gut flora • Favorable environment for C. diff growth
Clostridium difficile toxin?
Not invasive: disease via toxins
Two toxins
Toxin A: Enterotoxin → watery diarrhea •
(more potent)**Toxin B: Cytotoxin → Cell necrosis/fibrin deposition • Both bind to GI cells and are internalized • Destroy cytoskeleton of GI cells → pseudomembrane
Clostridium difficile colitis presentation and treatment:
Massive watery diarrhea • On endoscopy (rarely done): • Pseudomembrane formation (white-yellow plaques) • Mucosal ulcerations, fibrin, inflammatory cells •
Diagnosis • Stool detection of toxin A and B
Treatment for Clostridium difficile colitis
Metronidazole • ORAL Vancomycin •(normally not given orally due to poor absorption but in this case thats what you want, need it to hangout for awhile to kill c diff)
Other therapy for severe, recurrent disease • Surgery • Stool transplant
Corynebacterium diphtheria unique toxin feature:
Diphtheria Exotoxin
Not part of bacterial genome • Carried by β-prophage • “Lysogenic” phage → incorporates DNA into bacteria
mechanism of action: Inactivates elongation factor (EF-2) • EF-2 necessary for protein synthesis (translation) via ADP ribosylation
Corynebacterium Features
has been referred to as:
special media:
diagnosis:
“Chinese character”
Special culture media required
Loeffler’s [Metachromatic (blue/red) granules] or Tinsdale (Tellurite plate) [Black colonies]
Elek test for** **toxin detection** **(for diagnosis) • Antitoxin-impregnated filter paper under agar
Bacterial toxin precipitates and can be visualized
Diphtheria: signs/symptoms:
Absorption/dissemination of toxin can cause:
Sore throat, fever, lymphadenopathy
Gray-white membrane in pharynx
Absorption/dissemination of toxin can cause:
Myocarditis (heart failure, arrhythmias, heart block)
CNS disease (neuropathies)
Renal disease (renal failure)
Diphtheria treatment:
Treatment (acute infection):
Penicillin • Diphtheria antitoxin (passive immunization) • Diphtheria toxoid (active immunization)
note: rare due to toxoid vaccination
Listeria
Found in:
Facultative __ organism
whats unique about it:
Found in soil
Facultative intracellular organism
“Tumbling motility” • Move from cell to cell to avoid extracellular response • Polymerizes actin in cells to move (“actin rockets”)
what does Listeria do (3 things)/who does it affect?
Gastroenteritis
Diarrhea, nausea, vomiting • Usually self limited • often from contaminated food • Undercooked meat, unwashed vegetables • Unpasteurized cheese/milk
Meningitis
Elderly or newborns
Infection in pregnancy
Bacteremia in 3rd trimester • Flu-like illness (fever, chills) • Often resolves without treatment • Rarely can cause fetal demise or newborn infection
likes to Multiply in cells with poor cell-mediated immunity • Neonates, HIV, organ transplant
what is Granulomatosis Infantiseptica?
Listeria!
Severe in utero infection from Listeria • Disseminated abscesses and/or granulomas • Multiple organs: liver, spleen, lungs, kidneys, brain • Skin lesions (papules, ulcers) • Most babies stillborn or die soon after birth • Placenta shows distinctive inflammation • Chorioamnionitis • Villitis • Abscess formation
Only bacteria with a polypeptide capsule?
Bacillus Anthracis
Most are polysaccharide • B. Anthracis capsule contains D-glutamate • Limits/prevents phagocytosis
Bacillus Anthracis important features:
polypeptide capsule
Found in soil • Infects cattle, sheep, horses (and humans) • Farm workers at risk
Spores can be used as bioterrorism weapon
Produces two toxins: • Edema toxin • Lethal toxin
Anthrax Toxins
Edema toxin (contains edema factor) • Mimics adenylate cyclase • Increases cAMP → fluid secretion
Lethal toxin (contains lethal factor) • Protease • Inhibits cell signaling • Causes apoptosis
Anthrax Cutaneous disease
how does it happen, what is distinct about it and treatment?
Spores enter skin through cuts/abrasions →Vegetate → bacteria grows → Painless black ulcers forms** • Can progress to bacteremia and death • **Edema surrounds black ulcer from edema factor
Treatment: Ciprofloxacin, Doxycycline, Clindamycin
Anthrax Pulmonary disease
aka
how does it happen?
symptoms?
treatment?
classic CXR finding:
“Woolsorters’ disease”
Inhalation of spores • Flu symptoms that rapidly progress
Pulmonary hemorrhage, mediastinitis, shock, death
Treatment: Multi-drug regimen, antitoxin
Classic CXR finding: widened mediastinum
Bacillus Cereus: food to think about:
causes food poisoning from enterotoxins • Classically in undercooked/reheated rice • Heat-resistant spores may survive cooking • Cooked rice at room temperature allow bacteria to multiply • “Reheated rice syndrome”
2 types of illness caused by Bacillus Cereus:
Emetic type
Direct ingestion of toxin: Cereulide
Abdominal cramps, nausea, and vomiting (rarely diarrhea) • 1 to 5 hours after ingestion • Classically occurs in rice dishes
Diarrheal type
Abdominal cramps and diarrhea (not vomiting) • 8 to 16 hours after ingestion • Caused by at several enterotoxins • Toxins are heat labile • Cooking food reduces risk of illness • Often from meats, vegetables, and sauces
Actinomyces
where is it found?
what does it cause?
face thing to know:
treatment:
Normal oral flora • Also found in female genital tract
Anaerobe • Clusters into long filaments resembling fungi
Causes head/neck abscesses • In women, can cause IUD infections
Classically preceded by dental work/orofacial trauma • Facial mass present on exam • Often yellow center (yellow “sulfur” granules) • Often draining puss
Treatment: Penicillin +/- drainage
Nocardia boring little things to know about it:
they are important because:
treatment:
Branching, filamentous (like Actinomyces) • Acid fast • Produces urease (can be used to identify bacteria) • Obligate aerobe (loves lungs!) • Found in soil
boring but important to know because it causes pneumonia(usually immunocompromised) and skin infections(immunocompetent) without any classic/unique signs so the giveaway will be in bugs description
treatment: TMP-SMX
