Micro-Anaerobic Bacterial Infections Flashcards
What is the difference between anaerobe, facultative anaerobe, microaerophilic and aerotolerant?
Anaerobe- cannot grow at 10% CO2
Facultative- grows aerobically and anaerobically
Microaerophilic - grows poorly aerobically, grows well anaerobically
Aerotolerant- grows at 2-8% oxygen
What enzyme is produced by certain anaerobic organisms that allows them to be aerotolerant?
superoxide dismutase
What area of the body has the highest colony count of anaerobic bacteria?
Colon has 1000:1 anaerobes to aerobes
What 5 things can change the enteric flora?
- antibiotics
- antacids
- pregnancy
- age
- loss of teeth
What are the 6 main benefits of indiginous normal flora of the skin and mucousal surfaces?
- colonization resistance- interferes with the growth of pathogenic bacteria [bacteriocins, interferes w/nutrients, interferes with adhesion]
- vitamin K production [bacteriodes fragilis]
- metabolize bile acids and sterols
- modify drugs [sulfasalazine, digoxin]
- metabolize lipids, proteins, urea, carbs
- mucousal immunity
Why do stool and anaerobic abscesses smell bad?
Anaerobes produce SCFA and methylmercaptan that impede phagocytic killling by neutrophils
What 4 host factors allow anaerobic infection to occur?
- break in anatomic barriers to normal flora
- host immune mechanisms [LESS important]
- decreased redox potential of tissue
- specific clinical presdispositions
What anaerobic infections are you more likely to see with diabetes?
Osteomyelitis, cholescystitis
Which anaerobes are likely to be involved with the following cancers:
- colon
- uterus
- lung
- leukemia
- Clostridium perfringens bacteremia, C. septicum
- Clostridium and/or bacteriodes
- mixed aerobe/anaerobe oral flora aspirate
- clostridium perfringens, septicum, tertium[cecitis], capnocytophaga
What anaerobic infection is associated with acatalsemia, Down syndrome and AIDS?
necrotizing gingivitis
What 3 bacterial factors play a role in anaerobic infection?
- size of inoculum
- synergy with aerobic/facultative anaerobes
- virulence factors
What are the adherence virulence factors of anaerobes?
Pili/fimbrae
adhesin
capsule
What are the enzyme/toxins produced by anaerobes?
- superoxide dismutase
2. exotoxins [esp. clostridium alpha toxin -phospholipaseC which hydrolyzes cell membranes]
What surface structure on B. fragillis allows it to inhibit opsonophagocytosis and induce abscess formation?
Capsule
What is the function of SCFA produced by anaerobic bacteria?
Inhibits phagocytic killing by neutrophils
What six anaerobes are most commonly involved in invasive clinical infection?
- bacteriodes fragilis
- prevotella, porphyromonas [pigmented, fluoresce]
- fusobacterium nucleatum
- peptostreptococcus
- clostridium perfringens, ramosum, septicum
- Actinomyces
What are the 3 presentations of anaerobic infection in the CNS?
What are the 2 ways the anaerobes get to the CNS?
What is treatment?
- brain abscesses
- epidural abscesses
- subdural empyemas [abscess in preformed cavity]
They are often multiple and polymicrobial.
How did the infections get there?
- contiguous spread from chronic otitis, mastoiditis, sinusitis
- hematogenous spread from lung abscess with R-L shunt
May be curable WITHOUT surgical drainage
What is the presentation of Lemmiere’s syndrome?
What bacteria causes it?
peritonsillar abscess caused by fusobaterium necrophorum which infects the lateral pharyngeal space with septic jugular vein thrombosis.
Metastatic abscesses go to the lungs and other organs.
What is Ludwig’s angina?
What bacteria causes it?
What is the presentation?
submandibular space infection caused by mixed aerobes/anaerobes.
Presents with: swelling of the floor of mouth and neck, drooling, trismus, dyspnea.
What is Vincent’s angina?
“trench mouth” which is necrotizing gingivitis caused by Fusobacterium and anaerobic spirochetes
What is the most common cause of pleuropulmonary infection by anaerobes?
What are the 3 ways these pleuropulmonary infections present?
What are the 3 most common organisms?
Most common cause is aspiration of oral/gastric contents especially with severe peridontal disease resulting in:
1. aspiration pneumonia
2. lung abscess
3. pleural empyema
[usually affects posterior segments of the lung]
The 3 most common organisms are:
- prevotella
- fusobacterium
- peptostreptococcus
What aerobic organisms can accompany prevotella, fusobacterium and peptostreptococcus in pleuropulmonary infections?
Which aerobes are common in the hospital setting?
Viridians strep
Hospital setting:
- gram neg aerobes
- staphylococci
What organisms cause intraabdominal infections like appendicitis, diverticulitis, ischemic bowel, liver abscesses, pylephlebitis [septal portal vein thrombosis] secondary peritonitis and biliary tract infections?
Polymicrobial including coliforms and anaerobes
Which 5 anaerobic bacteria are associated with female genital tract infections?
Prevotella Peptostreptococcus porphyromonas Clostridium Bacteriodes
What 2 anaerobic bacteria are associated with IUDs?
- actinomycosis
2. eubaterium nodatum
A patient presents with necrotizing fasciitis and gas in the tissue. What organism is most likely responsible?
clostridium
What organisms are responsible for Fournier’s gangrene?
Fournier’s gangrene is mixed anaerobic/aerobic necrotizing cellulitis of the scrotum.
Anaerobes= prevotella, porphyromonas, peptostreptococcus, bateriodes, fusobacterium Aerobes= GABHS, other strep, staph, G- aerobes, facultative rods
What organisms are associated with a human bite?
- Oral anaerobes [fusobacterium] PLUS
2. eikenella corrodens [facultative]
What bacteria is associated with animal bites?
Pasteurella multocida [facultative]
Bacteremia of anaerobes is infrequent and often polymicrobial. If it is gram negative anaerobe bacteremia [ex. bacteriodes] what is there a high likelihood of?
Underlying abdominal or female pelvic pathology
What does C. septicum bacteremia suggest?
colon cancer or leukemic cecitis
A patient presents with C. perfringens and C. novyi bacteremia and soft tissue inflammation. How did this person most likely get it?
IVDU [skin popping]
What are signs that help diagnose anaerobic infection?
- clinical situations where infections are at skin or mucousa
- foul odor [due to SCFA production]
- gas or black discoloration
- gangrene, necrosis, abscess
- polymicrobial on gram stain
- sterile pus [doesn’t grow on routine culture]
- classic toxin features of histotoxic clostridia
Do not submit __________ for anaerobic culture because they will be positive, but misleading.
What are 3 ways you can collect appropriate samples for anaerobes?
Do not submit mucousal samples. Instead:
- fine needle aspirate of pus
- bronchial secretion collection with a protected brush
- tissue biopsies
Submit to lab immediately in an anaerobic transport medium
What 3 procedures will the lab do on anaerobic samples?
- direct microscopy
- inoculate selective and nonselective media
- growth takes 4-72 hours except some clostridium
What are the ONLY 3 situations where you would run antibiotic susceptibility tests on anaerobes?
- isolate was from a normally sterile site [blood, CSF]
- known virulent organisms
- infection requires prolonged therapy with the correct drugs [endocarditis, osteomyelitis, brain abscess]
What drug do you NOT use to treat anaerobic infections?
Fluoroquinolones [ciprofloxacin, ofloxacin, levofloxacin]
What drug was previously recommended for anaerobic infections “above the diaphragm” but is no longer used due to high resistance?
Penicillin
- increasing resistance due to b-lactamases
- prevotella, porphyromonas, bacteriodes, fusobacterium
