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
-diplopia
-ptosis
-expressionless facies
-regurgitation
-dysphagia
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?
-gingivitis
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
-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
-enterococcus
-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?
CT
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
A 56-year-old diabetic woman presented with fever, confusion and RUQ pain. A CT examination of the abdomen was done, showing air around her gallbladder. She most likely has:
A. Amebic liver abscess
B. Ruptured diverticular abscess
C. Emphysematous cholecystitis
D. Colonic perforation
C. Emphysematous cholecystitis
What bug do you suspect in an infection that doesnt respect tissue pains?
Actinomyces
This moderately obese 45-year-old woman presented with RUQ colicky pain, mild jaundice and fever to 104oF. ERCP shows an obstructing stone in the CBD (green arrow). Management includes:
A. Broad spectrum IV antibiotics.
B. Broad spectrum IV antibiotics + immediate decompression of the CBD.
C. Broad spectrum IV antibiotics until afebrile, then decompression of CBD.
D. Oral clindamycin + ciprofloxacin, then bring her back in 3 days to repeat ERCP.
B. Broad spectrum IV antibiotics + immediate decompression of the CBD.
The IDSA Guidelines for Empiric Treatment of Patients with Neutropenic Fever recommend several agents for initial therapy, including: a carbapenem or piperacillin/tazobactam or cefepime or ceftazadime. Knowing what you do about the concept of colonization resistance, which agent(s) would be your rational first choice in a virgin neutropenic leukemic patient with T=102oF?
A. Cefepime
B. Meropenem (a carbapenem)
C. Ceftazidime
D. Piperacillin/tazobactam
E. Either a or c
A. Cefepime
This 72-year-old woman has been in the hospital for 3 weeks with an episode of pneumonia, complicated by delirium and acute kidney injury. She is recovering, but develops fever, T = 101oF, crampy abdominal pain, and 4-6 watery, foul smelling stools/day. Which of the following should you do?
A. Send stool for Salmonella & Shigella cultures.
B. Place her in contact isolation.
C. Send stool for ova & parasite examination.
D. Send stool for C. difficile toxin PCR.
E. Both b & d.
E. Both b & d.
A 68-year-old farmer who does not like doctors, stuck a pitchfork in his foot while moving cow manure. Eight days later, he presented to the ER with trismus and painful back spasms. He has no fever. Which of the following is true about his therapy?
A. He does not need to receive active tetanus immunization, as exposure to the toxin will suffice for immunity.
B. Provision of tetanus immune globulin will reverse signs of disease within hours.
C. He should be given metoprolol (a B-blocker) alone for control of autonomic dysfunction.
D. Diazepam (a benzodiazepine) should be provided to assist in control of spasms.
D. Diazepam (a benzodiazepine) should be provided to assist in control of spasms.
*administration of tetanus ig will not reverse signs of disease, as toxin is already bound
A 32-year-old man who abuses drugs comes to the ER complaining of “double vision” and difficulty swallowing. On exam, he has no fever, his pupils are dilated and he cannot fully open his eyes. He has multiple skin ulcers. Appropriate approach to management includes:
A. Anaerobic culture of biopsies of the skin lesions.
B. Collect a blood specimen for toxin assay.
C. Provide heptavalent anti-toxin.
D. Collect stool for toxin assay.
E. a, b & c
E. a, b & c
Botulinum causes _______ muscle paralysis.
flaccid
Is botulinum ascending or descending paralysis?
descending
"floppy baby"
Infant botulism
How is wound botulism, aquired from punctures, different from normal adult botulism?
-absence of prodromal GI symptoms
-longer incubation period
-more likely to have fever
Botulinum toxin prevents vesicular reelase of ______.
acetylcholine
How is the pathogenesis of adult botulinum different from child botulism?
-adult disease caused by disease already produced in food
-infant the spores colonize and produce toxin in the GI tract
What is the exotoxin of Clostridium tetani?
tetanospasmin
Tetanospasmin prevents the vesicular release of ______ and _______.
GABA
Glycine
"Risus sardonicus"
-Clostridium tetani
=grotesque grinning expression from lockjaw and facial muscle spasms
What is used in the tetanus vaccine?
-tetanus toxoid
*amount of toxin causing disease is actually too low to induce immunity
Clostridium septicum is associated with underlying systemic __________/
malignancy
What organism causes gaseous gangrene?
Clostridium perfringens
"pseudomembranous enterocolitis?
C. difficile
What is the classic antibiotic that leads to C. diff infection?
Clindamycin
How do we treat C. diff (without poop transplant)?
-Metronidazole for mild cases
-Oral vancomycin for severe disease or recurrence
Why do we give oral vancomycin for C. diff?
-it is not absorbed well in the GI tract, so all of it will reach the organism
Which of C. diff's toxins is responsible for the pseudomembrane formation?
Toxin B
"sulfur granules"
Actinomyces
What is the microbiology of actinomyces?
-Gm (+)
-branching, filamentous rods
-sulfur granules
What bug "does not respect tissue planes"?
Actinomyces
What disease is caused by Gardnerella vaginalis?
Bacterial vaginosis
"fishy odor" vaginal discharge
Gardnerella vaginalis
"clue cells"
Gardnerella vaginalis