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Infectious Disease > Other gram positives > Flashcards

Other gram positives Flashcards

1
Q

Clostridium all share these features

A
  • All Gpos rods
  • all form spores
  • all are obligate anaerobes
  • All form toxins
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2
Q

Species of Clostridium to know

A
  • C. tetani (tetanus)
  • C. botulinum (botulism)
  • C. perfringens (wound infections, food poisoning)
  • C. difficile (diarrhea after antibiotic use)
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3
Q

C. tetani features

A
  • spores found in soil
  • enter the body from a penetrating injury (nail/splinter)
  • spores germinate into bacteria
  • produce tetanus toxin (tetanospasmin)
  • Travels to spinal cord
  • Blocks glycine and GABA release from Renshaw cells (inhibitory spinal cord interneurons)
  • symptoms
    • Spasms
    • Muscle contractions
    • Rigidity
    • Lockjaw (trismus)
    • Risus sardonicus (forced grin due to spastic facial muscles)
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4
Q

Tetanus Tx

A
  • Wound debridement
  • Metronidazole
  • Tetanus immune-globulin (binds circulating toxin)
  • Benzos or neuromuscular blockers until the toxin wears off
  • Tetanus toxoid is used for vaccination
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5
Q

C. botulinum features

A
  • Ubiquitous organism
  • Vegetables, fruits, seafood, soil
  • Creates heat-resistant spores (up to 100oC)
  • produces Botulinum toxin
    • works at neuromuscular junctions and prevents ACh release resulting in floppy paralysis
    • there are many different variants of the toxin and some are carried by bacteriophages
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6
Q

Botulism types

A
  • Food (toxin ingestion; usually adults)
  • Infant (spores)
  • Wound (Bacterial growth)
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7
Q

Preformed toxin ingestion Botulism

A
  • usually adults
  • undercooked food
  • canned food: anaerobic environment promotes growth
  • watch for multiple sick adults after a meal
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8
Q

Infant Botulism

A
  • ingestion of spores -> growth in infant intestine
  • Watch for contaminated honey
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9
Q

Wound Botulism

A

C. botulinum bacterial growth in a wound

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10
Q

Botulism features

A
  • symptoms appear 12-48 hours post-ingestion
    • Diplopia
    • Dysphagia
    • Dysphonia
  • Dx
    • often clinical
    • spores and toxin are sometimes detected in stool
  • Tx:
    • Antitoxin blocks circulating toxin
    • cannot block the toxin already in nerves
    • supportive care until toxin washout
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11
Q

C. perfringens features

A
  • Widespread in nature, especially in soil
  • Infects dirty wounds & causes food poisoning
  • Causes Gas Gangrene (Clostridial myonecrosis)
    • traumatic wound with vascular compromise
    • Favorable environment for anaerobic growth
  • Produces Alpha toxin
    • destroys muscle tissue and causes hemolysis
    • Phopholipase that acts on lecithin (lecithinase)
    • Degrades phospholipids in cell membranes
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12
Q

What is Alpha toxin

A

a toxin produced by Clostridium perfringens that is a phopholipase that acts on lecithin (is a lecithinase) and degrades phospholipids in cell membranes

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13
Q

Gas gangrene

A
  • caused by C. perfringens
  • Alpha toxin
  • severe pain at injury site within 24 hours
  • skin tense and tender
  • systemic symptoms
    • fever
    • hypotension
    • shock
  • Dx
    • gas at injury site on imaging
    • crepitus
  • Tx
    • surgical debridement
    • Broad spectrum antibiotics
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14
Q

C. perfringens food poisoning

A
  • usually undercooked meats
  • spores ingested so delay of (8-22 hours) before watery diarrhea
  • Contrast with S. aureus/B cereus (preformed toxins) so symptoms happen much more quickly (3-6 hours)
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15
Q

Features of C. difficile

A
  • Ubiquitous spores in nature including the soil
  • ingestion not harmful with normal GI flora
    • colonic flora prevent overgrowth of C. diff
  • Causes antibiotic-associated coolitis
    • antibiotics alter the normal gut flora resulting in a favorable environment for C. diff growth
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16
Q

Pseudomembranous colitis

A
  • Caused by opportunistic pathogen C. difficile
  • antibiotics disrupt normal gut flora allowing C. difficile to grow
  • Not invasive infection but is due to two toxins that bind to enterocytes and internalize them
    • Toxin A: Enterrotoxin -> watery diarrhea
    • Toxin B (10x more potent than toxin A): Cytotoxin -> cell necrosis/fibrin deposition
  • Toxins destroy the cytoskeleton of GI cells -> pseudomembrane
  • Massive watery diarrhea
  • endoscopy: pseudomembrane (white-yellow plaque), mucosal ulcerations, fibrin, inflammatory cells
  • Dx: Stool detection of Toxin A and B
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17
Q

Pseudomembranous colitis AKA

A

C. diff colitis

18
Q

Treatment of Pseudomembranous colitis

A
  • Metronidazole
  • ORAL vancomycin
  • other therapy for severe disease
    • Surgery
    • Stool transplant
19
Q

Corynebacterium diphtheria

A
  • Gpos non-motile non-spore forming curved rod with chinese character distribution
  • Causes diptheria
  • Produces Exotoxin
    • diptheria exotoxin is not from part of the bacterial genome but is carried by a bacteriophage (lysogenic phage -> incorporates DNA to the bacteria)
    • inactivates elongation factor 2 (EF-2) by adding ADP-ribosyl
    • EF-2 is necessary for protein synthesis (translation)
  • Unique lab diagnostic techniques
20
Q

Corynebacterium diphtheria culture media

A
  • Loeffler’s or Tinsdale (Tellurite plate)
  • black colonies on Tinsdale media
  • Metachromatic (blue/red) granules on Loeffler’s media
21
Q

Corynebacterium diphtheria diagnostic test

A
  • Elek test for toxin detection
  • antitoxin-impregnanted filter paper under agar
  • bacterial toxin precipitates and can be visualized
22
Q

Diphtheria

A
  • caused by Corynebacterium diphtheria
  • 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)
  • Incidence is rare in the modern era due to vaccination with toxoid
23
Q

Diphtheria Treatment

A
  • Penicillin
  • Diphtheria antitoxin (passive immunization)
  • Diphtheria toxoid (active immunization)
24
Q

Listeria features

A
  • 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”)
  • tends to infect poor cell-mediated immunity
    • neonates
    • HIV
    • organ transplant
  • In adults, often from contaminated food
    • Undercooked meat, unwashed vegetables
    • unpasteurized cheese/milk
    • Likes cold temperatures
  • neonates transplacental or transvaginal
25
Q

Listeria illnesses

A
  • Gastroenteritis
    • NVD
    • usually self-limited
  • Meningitis
    • elderly or newborns
  • Infection in pregnancy
    • bacteremia in 3rd trimester
    • flu-like illness (fever, chills)
    • often resolves without treatment
    • Rarely causes fatal demise or newborn infection
26
Q

Granulomatosis infantiseptica

A
  • 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 inflammation
    • Chorioamnionitis
    • Villitis
    • Abscess formation
27
Q

Bacillus group bacteria

A
  • Bacillus anthracis
  • Bacillus cereus
28
Q

Bacillus anthracis features

A
  • only bacteria with polypeptide capsule
    • most are polysaccharide
    • contains D-glutamate
    • Limits/prevents phagocytosis
  • Found in soil
  • Infects cattle, sheep, horses and humans
    • farm workers are at risk
  • spores can be used in bioterrorism
  • produces 2 toxins
    • Edema toxin
    • Lethal toxin
29
Q

Bacillus anthracis toxins

A
  • Edema toxin
    • Activates adenylate cyclase
    • increases cAMP-> fluid secretion
  • Lethal toxin
    • Protease
    • inhibits cell signaling
    • Causes apoptosis
30
Q

Anthrax cutaneous disease

A
  • spores eter skin through cuts/abrasions
  • vegetate -> bacteria grows
  • painless black ulcers forms
  • can progress to bacteremia and death
  • Edema surrounds black ulcer from edema factor
  • Tx
    • Ciprofloxacin
    • Doxycycline
    • Clindamycin
31
Q

Anthrax pulmonary disease

A
  • Pulmonary disease
    • “woolsorter’s disease”
    • Inhalation of spores
    • Flu like symptoms that rapidly progress
    • pulmonary hemorrhage, mediastinitis, shock, death
  • Tx
    • Multidrug regimen, antitoxin
  • Imaging
    • Wide mediastinum (aortic dissection causes this also but would have different symptoms)
32
Q

Bacillus cereus features

A
  • Food poisoning from enterotoxins
  • classically from undercooked or reheated rice
    • bacteria frequently present in undercooked rice
    • heat-resistant spores may survive cooking
    • cooked rice at room temperature may allow to multiply
    • “reheated rice syndrome”
33
Q

Types of B. cereus food poisoning

A
  • Emetic type
    • direct ingestion of toxin: Cereulide
    • abdominal cramps, NV (rarely diarrhea)
    • 1-5 hours post-ingestion
    • classically occurs in rice dishes
  • Diarrheal type
    • Abdominal cramps and diarrhea (not vomiting)
    • 8 to 16 hours after ingestion
    • caused by eating several enterotoxins
    • Toxins are heat labile
    • cooking food reduces risk of illness
    • often from meats, vegetables and sauces
34
Q

Actinomyces features

A
  • 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 preceeded by dental work/orofacial trauma
    • facial mass present on exam
    • often yellow center (yellow “sulfur” granules)
    • often draining pus
  • Treatment:
    • Penicillin +/- drainage
35
Q

Bacteria to know that resemble fungi

A
  • Nocardia
  • Actinomyces
36
Q

Nocardia features

A
  • Branching filamentous (like actinomyces)
  • acid-fast
  • produces urease (can be used to identify bacteria)
  • Obligate aerobe (loves lungs)
  • found in soil
37
Q

Nocardia illnesses

A
  • Pneumonia
  • Skin infection
  • brain abscesses
  • Bacteremia
38
Q

Nocardia pneumonia

A
  • immunocompromised pts
  • inhalation of bacteria
  • radiological findings
    • nodules
    • masses
    • infiltrates
    • lobar consolidation
    • pleural effusions
  • Tx
    • TMP-SMX
39
Q

Nocardia Skin infection

A
  • Immunocompetent pts
  • often invades during gardening or farming
  • manifestations
    • ulcers
    • cellulitis
    • nodules
    • abscesses
  • Treatment
    • TMP-SMX
40
Q

Nocardia drug of choice

A

TMP-SMX

Infectious Disease (82 decks)

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