L7: Anaerobes & Peritonitis Flashcards
What is an example of a strict/obligate aerobe?
Pseudomonas aeruginosa
What is an example of a facultative aerobe?
E. coli
What is a microaerophilic organism? Give an example
grow poorly aerobically but distinctly better under 10% CO2 - e.g. Neisseria meningitidis
What is an example of a strict/obligate anaerobe?
Bacteroides fragilis
Which anaerobe(s) are present on the skin?
Propionibacterium acnes
Which anaerobe(s) are present in the colon?
bacteroides spp.
clostridium spp.
prevotella spp.
peptostreptococcus spp.
Which anaerobe(s) are present in the oral cavity + upper respiratory tract?
fusobacterium
peptostreptococcus spp.
Which anaerobe(s) are present in the female genital tract?
lactobacillus spp.
If someone was bitten by a dog, which anaerobe will most likely be present?
Capnocytophaga canimorsus
What must be collected to make a diagnosis of an anaerobic infection?
- Pus
- Tissue Sample
both for culture
What are host factors that may predispose a patient to anaerobic infections?
- impaired gag reflex + cough reflex
- trauma + tissue ischaemia
- gastrointestinal surgery
- amputation of lower limb in patient with peripheral vascular disease
- antibiotics
Antibiotics alter the composition of the normal colonic flora, predisposing it to the overgrowth of…?
Clostridium difficile
List some of the characteristics of the Clostridium spp.
- gram positive bacilli
- form spores
- produce exotoxin
- most are strict anaerobes
e.g. C. tetani, C. botulinum, C. difficile, C. perfringens
What is the name of the toxin a/w Clostridium Tetani? What is its function/MOA?
Neurotoxin - Tetanospasmin
- blocks transmission at inhibitory synapse resulting in “inhibition of the inhibitory neurons”
- leads to sustained muscle contractions/spasms
Briefly explain the pathogenesis of C. tetani
- skin trauma occurs (e.g. puncture wound, burns…)
- spores inroduced via skin trauma
- spores in wound germinate when there is a localized anaerobic environment
- they will then produce toxin
Which organism was known to contaminate heroin?
Clostridium tetani
What is the clinical presentation/symptoms of C. tetani?
muscle spasms - spontaneously or after minor stimuli
flexion of muscles e.g. arching of back
trismus - “lock jaw”
sardonic appearance
What is another name for trismus?
Lock Jaw
What pathogen is known for causing a sardonic appearance?
C. tetani
What are some complication of a C. tetani infection?
laryngospasm ANS dysfunction (labile BP, arrhythmias, sweating)
What is the treatment/management plan for treating a patient with a C. tetani infection?
- ABCs
- Wound Debridement + Metronidazole
- Tetanus Immunoglobulin
- Manage Spasms
- Avoid Touch, Light or Other Stimuli
Which antibiotic is used when treating C. tetani?
Metronidazole
What is the main prevention strategy for preventing a C. tetani infection?
Vaccination!
Toxoid Vaccine/Inactivated Tetanus Toxin Vaccine
Why might a C. tetani booster immunization be required?
the vaccine may not provide protection after 10 years - so the patient will need a booster
What is the name of the toxin a/w Clostridium Botulinum? What is its function/MOA?
“Botox”
- inhibits the release of ACh at NMJ resulting in weakness/acute flaccid paralysis
How does foodborne botulism occur? (pathogenesis)
from poorly canned foods - foods that were not cooked thoroughly and then put in an anaerobic environment
- spores germinate and toxin is produce
- person ingests contaminated food
- fast onset
What is infant botulism? (pathogenesis)
- ingestion of spores that germinate in the GIT
- toxin then released in the GIT and absorbed
What is the presentation/clinical features of botulism?
- symmetrical descending flaccid paralysis
- bilateral cranial nerve palsies
- double vision
- difficulty swallowing
- muscle weakness
How does infant botulism appear?
- constipation
- muscle weakness
- lethargy
- poor feeding
- “floppy” baby
What tests/investigation can be done to diagnose foodborne botulism?
detection of toxin in stool/vomitus
What test/investigation can be done to diagnose infant botulism?
organism or toxin in stool
What test/investigation can be done to diagnose wound botulism?
culture of organism from wound site
What is the treatment/management for botulism?
- ABCs
- Antitoxin - Botulism Immunoglobulin
- Wound Debridement + Metronidazole (only in wound botulism)
C. difficile infections often occur in which population group?
in people who have had contact with healthcare or have been on antibiotics
Antibiotics are known to knock out both good and bad bacteria in the gut - this can lead to a C. difficile infection. Which antibiotics have been most implicated with C. diff infections?
- Fluoroquinolones
- Beta-Lactam Antibiotics (esp. ampicillin and 3rd generation cephalosporins)
- Clindamycin
What are some 3rd generation cephalosporins?
Cefotaxime, Ceftriaxone
How may a C. diff infection be diagnosed?
PCR of stool for toxin gene (TCDB gene)
What is the treatment/management plan for C. difficile infection?
- Isolation + Contact Precautions
- Review Antibiotics
- Supportive Therapy
- Antibiotics ( Oral Vancomycin OR Fidaxomicin)
Which antibiotic is used to treat botulism?
Metronidazole
Which antibiotics may be used to treat C. difficile infections?
Oral Vancomycin or Fidaxomicin
What is clostridial myonecrosis another name for?
gas gangrene
What toxin causes c. perfringens food poisoning?
C. perfingens enterotoxin
What toxin causes c. perfringens gas gangrene?
Lecithinase toxin
How can gas gangrene be diagnosed? What tests/investigations can be done?
- CT or XRAY (looking for gas in tissues)
- Wound Swab or Blister Fluid for Culture
- Blood Culture
What is the treatment for gas gangrene?
- surgical debridement**
- high dose penicillin/clindamycin
What is a risk factor for SBP?
cirrhosis of the liver (ascites)
What organisms usually cause SBP?
Aerobic Bacteria (E. coli, K. pneumoniae, S. pneumoniae, GAS, enterococci)
What organisms usually cause peritonitis complicating peritoneal dialysis?
Skin Flora - S. aureus, coag neg staph
GI Flora - E. coli, pseudomonas
What are the symptoms/clinical features of peritonitis complicating peritoneal dialysis?
- cloudy dialysis fluid
- white flecks, strands or clumps (fibrin) in the dialysis fluid
What is the treatment of secondary peritonitis?
- Empiric Antibiotics: Co-Amoxiclav/Piperacillin-Tazobactam + Gentamicin
- Source Control: drainage of abscesses, appendicectomy, bowel resection, repair perforated ulcer etc.
