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Term 4: Infectious Diseases > Anaerobic Infections > Flashcards

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What is an anerobe?

organisms that requre reduced O2 for growth

i.e. fail to grow on the surface of solid media in 10% CO2 in air


What is the concept of colonization resistance?

concept that anaerobic bacteria occupy ecological niches that would otherwise be filled with potentially pathogenic organisms, by depleting oxygen & other nutrients, as well as producing various enzymes & toxic products.


What are the common characteristic of anaerobic infections?

-Frequently polymicrobial.

-Gas forming & foul smell.

-Failure to grow if not cultured properly under anaerobic conditions:

-do not respond to some usual antibiotics


Why are many anaerobic infections diagnosed late or not at all?

They fail to grow if not cultured properly under anaerobic conditions


What toxins are produced by C. difficile?

-Toxin A:  watery diarrhea

-toxin B:  cytotoxic to colon cells (degrades actin)

-Binary toxin:  increased virulence & resistance


What is the most common cause of marked leukocytosis?

-C. difficile


How is C. difficile diagnosed?

-PCR-based toxin gene testing


What is the most common scenario for botulism?

-Infants ingest spores, usually from honey

-progresses for 1-2 weeks

"floppy baby" syndrome


What are the symptoms of botulism?

-blurred vision



-expressionless facies




What are the important clinical features of botulism?

-No fever

-Symmetrical neurological manifestations

-Patients remain responsive

-Heart rate is normal or slow

-Sensory deficits do not occur


How do we treat botulism?

-botulism antitoxin

-only binds free toxin, current symptoms will not be reversed until later

-Human botulism immunoglobulin (infant botulism)


When does Clostridium tetani infection occur?

-acute injuries (punctures & lacerations)


What are the four clinical forms of disease caused by tetanus?

-localized tetanus

-facial tetanus (risus sardonicus)

-neonatal tetanus

-generalized tetanus


What symptom does generalized tetanus generally begin with?

-trismus (lockjaw)


How do we treat tetanus patients?

-Benzos for symptom relief -

abx: metronidazole or penicillin

-alpha and beta blockers

-passive & active immunization


What does Porphyromonas gingivalis cause?



What are the 3 major aspiration syndromes?

-chemical pneumonitis 2' to gastric acid burns

-bronchial obstruction 2' to particulate matter

-bacterial aspiration syndromes


Is aspiration pneumonia more common in the right or left lung?


-right main stem bronchus comes off at less of an acute angle


What are the Clinical Presentation of Anaerobic Pleuropulmonary Infections?

-Relatively insidious onset;

-Low-grade fever, malaise, weight loss, pleuritic chest pain & cough;

-Poor dental hygiene;

-Large amounts of sputum with foul taste:

*Odor of patient’s breath can be very offensive!


How do we diagnose aspiration pneumonia?

Sputum gram-stain is the diagnostic procedure of choice

*Anaerobic culture of expectorated sputum is unreliable, because of oral contamination.


What is a buzzword for actinomyces?

sulfur granules


What events can result in microorganisms within the peritoneal cavity?

-Organ perforation (ulcers, appendicitis, diverticulitis, etc.);

-Organ trauma (bullet, knife) or iatrogenic causes (“incidental” surgical accidents);

-Intraabdominal ischemia;

-Extension of inflammation or a preexisting infection.


What is 1' or spontaneous bacterial peritonitis?

-infections of the peritoneal cavity without an evident source

-usually caused by a single species of bug


When does spontaneous bacterial peritonitis occur?

-usually in kids with nephrotic syndrome, and adult cirrhotics

Children = S. pneumoniae

Adult = E. coli


What organisms are usually involved in pancreatic abscesses?

-E. coli


-other enterobacteriaceae


How are splenic abscesses different from other abdominal abscesses?

-usually results from bacteremic spread

-associated with endocarditis & hemoglobinopatheis

-Usually S. aureus or S. penumo


What is the test of choice for diagnosis of abdominal infections/abscesses?



A 39-year-old alcoholic man presented to the ER at BTGH with fever & productive cough. As you examine him, you note the particularly foul odor of his breath. The best diagnostic test in this case is:

A. Blood cultures

B. Chest CT scan

C. Sputum gram stain

D. Anaerobic sputum culture E. Acid fast smear

-C. Sputum gram stain

*Anaerobic sputum culture will be contaminated by oral bacteria

*The gram stain should show a mixture of different bacterial morphologies


This patient with chronic hepatitis C infection and ascites presented to the Emergency Room at the MEDVAMC with fever, confusion and abdominal pain. Paracentesis reveals 800 WBCs/UL in the ascitic fluid. The most likely cause of the infection is:

A. Pseudomonas aeruginosa

B. Staphylococcus aureus

C. Escherichia coli

D. Enterococcus faecalis

C. Escherichia coli =Spontaneous bacterial peritonitis


A 72-year-old smoker was diagnosed with squamous cell lung cancer as an outpatient. Bronchoscopy revealed almost total occlusion of the RUL bronchus. Two weeks later, he is admitted with fever, cough & sputum production. His sputum has a foul taste. There is a dense lobar consolidation in the RUL. What is the most likely bacteriology?

A. Pseudomonas aeruginosa/Klebsiella pneumoniae
B. Staphylococcus aureus
C. Legionella pneumophila
D. Prevotella melaninogenica/Peptococcus magnus/Fusobacterium necrophorum

D. Prevotella melaninogenica/Peptococcus magnus/Fusobacterium necrophorum