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Microbio Gram Neg > Anaerobic Infections > Flashcards

Anaerobic Infections Flashcards

1
Q

Common aerobic microenvironments

A

Tonsils, gingiva, throat, skin, colon, vagina

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2
Q

Aerotolerant

A

Survive in O2 but do not grow

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3
Q

GNR Anaerobes (5)

A
  • Bacteroides fragilis
  • Other Bacteroides spp live in mouth and GU tracts. Less virulent than fragilis.
  • Fusobacterium necrophorum
  • Prevotella spp
  • Porphyromonas spp
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4
Q

Gram Positive Anaerobes (4)

A
  • Peptostreptococcus
  • Clostridia spp (spore-forming rods)
  • Actinomyces spp (non-spore forming rods)
  • Propionibacterium (non-spore forming rods)
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5
Q

What is most common cause of anaerobic infections?

A

Bacteroides fragilis

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6
Q 
Bacteroides fragilis
Morphology
Known for?
Location of normal microbiota
Hallmark
Resistance
A 
GNR
Most common cause of anaerobic infections.  
Normal microbiota of GI tract.  
Hallmark is abscess formation.  
Resistance due to beta-lactamases.
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7
Q

Fusobacterium necrophorum
Morphology
Location
Virulence factor

A

Long thin rods (fusiform). Gram Neg.
Normal mouth / gingival flora.
May be found in lung and GI as well.
Secrete active endotoxin.

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8
Q

Peptostreptococcus
Morphology
Known for?
Location

A

Gram Positive coccus.
2nd most common cause of anaerobic infections after B fragilis.
Found in mouth, lung, GI, and GU.

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9
Q

Common anaerobes in oral cavity (6)

A

Bacteroides (non-fragilis), Fusobacterium, Prevotella, Peptostreptococcus, Actinomyces, and Porphyromonas

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10
Q

Ludwig’s Angina

A

Deep soft tissue infection w/in the submandibular / sublingual space. May cause respiratory compromise by elevating floor of mouth and forcing tongue back into the airway.

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11
Q

Lemierre’s Syndrome

A

Caused by Fusobacterium necrophorum.
Soft tissue infection of the lateral pharyngeal space w/ suppurative thrombophlebitis of the jugular vein → septic pulmonary emboli and bacteremia.

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12
Q

Pyogenic brain abscess caused by?

Hematogenous brain abscess caused by?

A

Pyogenic - usually mixture of aerobes and anaerobes.

Hematogenous - usually NOT anaerobes. Often Staph aureus or pneumococcus.

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13
Q

Anaerobes causing lung infections (4)

A

Prevotella, Fusobacterium, Peptostreptococci, Bacteroides

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14
Q

What causes most pneumonias?

A

Aspiration

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15
Q 
Lung abscess
Speed of progression
Constitutional sxs
Hallmark
Tx
A

Slow / subacute.
Constitutional sxs include weight loss, anorexia, and night sweats
Hallmark is thick, fetid sputum
Tx w/ weeks / months of AB’s

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16
Q 
Pleural fluid characteristics of empyema
pH
Glucose
LDH
Tx
A
  • Low pH, under 7.2, b/c bacteria produce acid
  • Low glucose, under 60 b/c bacteria eat it
  • High LDH, over 60
  • Tx – Drainage (chest tube) + antibiotics. Possibly decortication (remove pleura)
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17
Q

Anaerobes that cause intraabdominal infections (5)

How does normal microbiota usually prevent intraabdominal infections?

A

B fragilis, Prevotella, Fusobacterium, Peptostreptococcus, and Clostridia
Normally take up space and release enzymes to prevent infection. Also produce vitamin K and bile.

18
Q

Primary peritonitis

A

Infection of ascitic fluid seen in end-stage liver disease. Most often due to aerobic bacteremia that seeds the ascites

19
Q

Secondary peritonitis
Cause
Sxs
Tx

A

Usually caused by anaerobes following a breach in the GI mucosa.
Sxs include severe abdominal pain / rebound. Life-threatening.
Tx w/ surgery and AB’s.

20
Q

Liver abscess
Mechanism
Tx

A

Most common visceral abscess. Infection may spread from GI tract through biliary tract or through portal venous system. Tx w/ drainage of AB’s.

21
Q

Female GU anaerobes (4)

A

Prevotella, Peptostreptococcus, B fragilis, Clostridia

22
Q

Endometritis caused by which bug?

May follow what?

A

C perfringens

May follow incomplete abortions

23
Q

Tuboovarian abscess / PID
Caused by?
Complications?

A

Usually mixed infection

May cause scarring / infertility

24
Q

Vaginosis

Cause and sxs

A

Decline in acid-producing Lactobacilli (normal microbiota) and increase in anaerobes → vaginal discharge

25
Q

Anaerobes causing SSTI’s (3)
Examples
Complication

A

Bacteroides, peptostreptococci, and Clostridia
•Diabetic foot infections, pressure ulcers (often on sacrum), necrotizing fasciitis (ex includes Fournier’s gangrene), bites
• Contiguous osteomyelitis – spreads from soft tissue infections, especially diabetic foot infections or pressure ulcers.

26
Q

What is most common anaerobe causing bacteremia?

A

Bacteroides fragilis

27
Q

Clostridia spp
Where do they live?
Morphology

A

Ubiquitous, found in soil, decaying vegetation, and GI tract.
Large Gram Pos Rods that produce spores.

28
Q 
C perfringens
How common?
Appearance
Virulence factors
Diseases (3)
A

Most common Clostridial isolate
Characteristic “boxcar” appearance
Toxins: lethicinase (alpha toxin) and hemolysin (phi toxin)
Food poisoning, enteritis necroticans (small bowel necrotizing infection), and gas gangrene.

29
Q

What foods does C perfringens cause food poisoning in?
Mechanism
Sxs

A

Found in meats, poultry, and gravy
Multiplies during cooling. Toxin is NOT preformed.
Sxs start 8-16 hours after eating, including cramps and diarrhea (vomiting is rare).

30
Q

What causes gas gangrene?
Sxs (5)
Tx

A

Caused by C perfringens. Usually trauma-mediated.
Sxs - Severe pain out of proportion to visual appearance, gas production in soft tissues (crepitus / subcutaneous emphysema), magenta / bronze color, hemorrhagic bullae, and dirty dishwater drainage
Tx - debridement and AB’s (penicillin + clindamycin to stop toxin production)

31
Q 
C tetani
Spore morphology
Environment
Toxin and mechanism
Sxs
Complications
Diagnosis
Tx
Vaccine schedule
A

Spore, looks like a tennis racket.
Found in soil and GI tracts.
•Tetanospasmin (Tetanus Toxin) – exotoxin made at wound site. Enters nervous system via presynaptic terminals of lower motor neurons. Carried retrograde to CNS, inhibiting NT release from inhibitory cells → depol of motor neurons / sustained muscle contraction.
•Descending pattern – trismus (lockjaw), neck stiffness, swallowing problems, abdominal rigidity, generalized. Spasms may be triggered by sensory stimuli.
•Complications include airway obstruction, laryngospasms, fractures, autonomic hyperactivity, pulmonary embolism, and aspiration pneumonia. Toxin increases body temp, sweating, BP, and pulse.
•Diagnosis is clinical
•Tx – supportive (ventilation), muscle relaxants (benzos), HTIG (human tetanus immunoglobulin [passive]), metronidazole, and wound debridement. AB’s not great b/c sxs are toxin-mediated.
•Childhood vaccine (DTaP), booster during adolescence (Tdap) and every 10 years during adulthood

32
Q 
C botulinum
Environment
Spore characteristics
Mechanism / sxs
Causes (4)
Clinical features
Diagnosis
Tx
A
  • Found in soil / water worldwide.
  • Subterminal spore. Heat stable.
  • Neurotoxin prevents release of Ach → muscle weakness (flaccid paralysis) and autonomic dysfunction.
  • Causes
  • Foodborne (15%) – ingest PREFORMED toxin, acting w/in 36 hrs. Found in home-canned foods, fruits, fish products
  • Infant (65%) – ingest spores, found in honey, soil. Normal GI microbiota not established yet so infection is easier.
  • Wound (20%)
  • Inhalational – toxin, bioterrorism
  • Clinical features
  • Acute, bilateral cranial nerve dysfunction → Blurred vision, diplopia, dysphagia, facial and tongue weakness, drooping eyelids, slurred speech
  • Descending motor weakness
  • Afebrile
  • Diagnosis is clinical – stool, serum, and food
  • Tx – supportive (ventilation), trivalent antitoxin (A, B, E), wound debridement, AB’s (penicillin for wounds), human botulinum immune globulin for infants.
33
Q

What is most common cause of nosocomial diarrhea and unexplained leukocytosis in hospitalized pxs?

A

C difficile

34
Q

How can C diff b/c disinfected?

A

Bleach or UV light. NOT alcohol. Need to wash hands w/ soap and water.

35
Q 
C difficile
Virulence factors
Population
Diagnosis and problems w/ tests
What if culture is positive?
Tx
A

Spores infect colon. Exotoxin A and B cause mucosal damage –> diarrhea.
More common in elderly
•Diagnose w/ toxins in stool (using enzyme immunoassay, EIA), PCR, and endoscopy
• Toxins break down quickly so it is important for stool sample to be fresh.
• PCR may cause many false positives.
•Name comes from being difficult to culture. Even when culture does grow, it doesn’t mean it’s a toxin-forming strain (most aren’t).
•Tx – stop all unnecessary AB’s, do NOT use antiperistaltics. Use oral metronidazole for mild cases and oral vancomycin for moderate / severe cases. For life threatening cases, use oral / rectal vanco, IV metronidazole, IVIG, and possibly colectomy.

36
Q

Why do some pxs have recurrent C diff?

A

Lack IgG to toxins.

37
Q

Which AB’s are generally considered “A+” for anaerobic infections? (5)

A

Metronidazole, carbapenems, beta-lactamase inhibitor combos, tigecyclin, moxifloxacin

38
Q

What does crepitus feel like?

What is this an indication of?

A

Skin feels bubbly / spongy/ like rice krispies.

Indicates anaerobic infection, often Clostridium perfringens for gas gangrene.

39
Q

What type of infection usually causes peritonitis?

A

Mostly mixed infections of aerobes and anaerobes.

40
Q

AB’s for hospital acquired pneumonia

A

FQ or beta lactam (ceftriaxone) + macrolide

41
Q

What AB is used for anaerobic oral infections?

A

Clindamycin

42
Q

What are the 2 most common GNR’s and GPC’s to cause Anaerobic pneumonia?
What do you use to treat?

A

GNR’s: Prevotella and Fusobacterium
GPC’s: Peptostreptococcus and oral strep viridans.
Tx w/ clindamycin or ampicillin / sulbactam

Microbio Gram Neg (10 decks)

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