03a: Infectious Flashcards
Anaerobes are characterized by their ability to grow only in an atmosphere containing (X)% oxygen.
X = under 10
Anaerobes are isolated in (X)% of all clinical infections.
X = 5-10
Anaerobic bacteria are a component of the normal flora of:
- Skin
- Mouth
- GI tract
- F genital tract
List Gram-negative anaerobes commonly identified in clinical practice.
- Fusobacterium
- Bacteriodes group (B. fragilis, Prevotella, etc)
- Veillonella
List Gram-positive anaerobes commonly identified in clinical practice. Star the cocci.
- Peptostreptococcus*
- Clostridia
- Proprionobacterium
- Actinomyces
T/F: Frequently, anaerobes are a component of polymicrobial (mixed) infections.
True
T/F: Anaerobic infections commonly associated with gas in tissue and positive routine culture.
False in that it’s usually negative on routine culture
Which type of bacteria associated with post-bite infections and (X) granules?
Anaerobes
X = sulfur
T/F: most anaerobes will die once in contact with oxygen.
False - most are aerotolerant (not strict anaerobes)
Obligate aerobes require (X)% oxygen to grow.
X = 15-21
Which locations on normal person have highest anaerobes:aerobe ratio?
- Gingival surface
- Colon
Ratio is 1000:1
Anaerobic infections generally arise from (X). List some exceptions.
X = endogenous flora
- Food poisoning from C. perfringens
- C. tetani infections
Many anaerobic bacteria have (slow/fast) growth rates, making β-lactam antibiotics (more/less) effective.
Slow; less
T/F: Anaerobes seldom involved in acute/chronic sinusitis and otitis media.
False - seldom in acute, but frequent in chronic
T/F: Anaerobes seldom involved in meningitis.
True
List some GI infections in which anaerobes seldom play a role.
- Acute cholecystitis
- Spontaneous peritonitis
- Cystitis
T/F: Your diabetic patient has a foot ulcer that is now infected. The culprit is likely anaerobic.
True
Between your patient with UTI/pyelonephritis and another with appendicitis, which is likely infected with anaerobe?
Appendicitis
What are key things to keep in mind when collecting and processing anaerobic bacteria?
- Aspirate using needle and syringe
- Expulsion of air and sealing of syringe
- Prompt processing (under 2-3h)
How could a swab be used to collect sample for anaerobe culture?
Place swab in Stuarts Transport Medium during 1-2h transport
T/F: Room T is more conducive for anaerobe survival than refrigeration.
True
While waiting for gram stain, which findings in bacterial specimen leads to suspicion of anaerobes?
- Foul odor
- Gas
- Necrotic tissue
- “Sulfur” granules
Above diaphragm treatment for anaerobes typically involves:
Beta-lactam/beta-lactamase inhibitor combos
Below diaphragm treatment for anaerobes typically involves:
Metronidazole
Which antibiotics have proven active against both “arms” (above and below diaphragm) of anaerobic infections?
New beta-lactams (ex: piperacillin/tozobactam) and tigecycline
Most common reasons for failure of therapy in anaerobic infections:
- Undrained pus
2. Insufficient duration of antibiotics
Gut anaerobes (commensals) are important in (X) metabolism.
X = CHO, vitamin K, bile acids, and some drugs
What are the most common anaerobes involved in infectious states (immuno-competent host).
- Peptostreptococcus
- Prevotella
- Bacteriodes
- Fusobacterium
(X) species are the most
commonly isolated microorganisms in intra-abdominal infections.
X = E. coli (aerobic) and Bacteriodes (anaerobic)
Two major causes of visceral pain in GI.
- Distension (stool, fluid, gas)
2. Obstruction
T/F: GI viscera are relatively insensible to most stimuli, so pain is fairly indicative of tissue damage.
False - despite being relatively insensible, pain in GI viscera will occur even in absence of tissue damage
(X) is a GI disorder characterized by chronic abdominal pain and altered bowel habits in the absence of any organic cause.
X = IBS (irritable bowel syndrome)
Patients with IBS have changes in (X), which is what causes their Sx.
X = neurologic processing of bowel sensation and motor function
List the three characteristics of IBS pathophysiology.
- Altered GI motility (increased reactivity to meals, stress, distention, CCK)
- Altered visceral sensation (hypersensitivity)
- CNS-Enteric NS dysregulation
IBS patients have an (absent/exaggerated) gastrocolic response, so (X) immediately causes (Y).
Exaggerated;
X = gastric distention after meals
Y = fecal urgency and diarrhea
(X) is the primary NT of the GI tract, released from (Y).
X = serotonin (5-HT) Y = ECC (enterochromaffin cells)
95% of serotonin in body found in GI tract!
Serotonin role in GI tract.
Initiates peristaltic, secretory, vasodilatory, vagal, and nociceptive reflexes
T/F: Serotonin regulates nausea/vomiting in CNS.
True
Which NT receptors in GI tract are implicated in pathophysiology of IBS? Therapeutic agents target these receptors for (activation/inactivation).
Serotonin (5-HT3 and 5-HT4)
Inactivation (antagonizing)
Rome IV Criteria is for diagnosing (X).
X = IBS
Rome IV Critera: 3 months of (X) at least (1/3/5) days per week and associated with 2 or more of following:
X = abdominal pain (recurrent)
1 day/week
- Defacation
- Change in stool frequency
- Change in stool appearance/form
IBS Subtypes:
- IBS with constipation
- IBS with diarrhea
- Mixed IBS
- Unsubtyped IBS (doesn’t meet criteria for other subtypes)
Patient meets criteria for IBS diagnosis and reports that over 50% of her stools are watery and she never has hard/lumpy stools. Which subtype would you place her in?
IBS with diarrhea (over 25% are loose/watery and under 25% are hard)
Patient meets criteria for IBS diagnosis and reports that he never has normal stools - they’re always either hard/lumpy or watery. He reports the ratio is about 1:1. Which subtype would you place him in?
Mixed IBS (over 25% are loose and over 25% are hard)
Most recent estimates yield IBS rates around (X)% with F:M ratio of (Y).
X = 10 Y = 3:1
First IBS presentation typically occurs around ages (X) and prevalence decrease after age (Y).
X = 30-50 Y = 60
T/F: A diagnosis of IBS is life-long.
True - chronic disease, though symptoms wax and wane
Diagnosis of IBS made when which 3 criteria are met?
- Rome criteria fulfilled
- No “alarm symptoms”
- Negative screening studies
Patient may meet Rome criteria for IBS, but presence of “alarm symptom” such as (X) would prompt additional workup.
X = weight loss, blood in stool, nocturnal Sx, abnormal PE, FHx of colon cancer
Patient presents with IBS-like symptoms, but he has cousin with Crohn’s. Which screening test(s) could you do to rule out IBD?
ESR and CRP
Patient presents with IBS-like symptoms. You run a TTG serology to screen/exclude (X) etiology.
X = Celiac
T/F: Workup for diagnosing IBS includes screening for infectious pathogens.
True - stool for ova/parasites
List the three symptom groups of IBS.
- Abdominal pain/bloating
- Diarrhea
- Constipation
Abdominal pain/bloating Rx for IBS includes which agents?
- Anticholinergic
2. 5-HT3 R antagonism (SSRIs commonly used instead)
T/F: Opioids are commonly prescribed to relieve abdominal pain/bloating in IBS.
False - prescribed for diarrheal symptoms
List two opioids used in IBS when (X) is the predominant symptom.
X = diarrhea
- Loperamide
- Diphenoxylate
Aside from opioids, (X) drug has been shown to improve (Y) symptom in IBS. What’s the likely mechanism?
X = rifaximin (antibiotic) Y = diarrhea
Likely alters gut flora composition
First line therapy for severe IBS constipation is (X), which is effective in (minority/majority) of cases.
X = fiber supplementation
Minority
What could you try next if fiber supplementation, for treating (X) symptom of IBS, fails? What’s the mechanism behind this?
X = constipation
Surfactants (docusate Na) - impair small intestinal water absorption
Your patient with IBS-constipation is relieved to find that OTC senna (a stimulant laxative) has significantly helped her symptoms. What advice do you give her?
Stimulant laxatives not recommended for chronic use - you can prescribe osmotic laxatives and other effective therapies
Most effective therapies for severe IBD constipation:
- Osmotic laxatives (Mg salts, lactulose, sorbitol)
- Miralax (polyethylene glycol)
- Bowel retraining
Prostaglandin analogues are being used to treat (X) symptom of IBS.
X = constipation
A new drug, (X), is used for (diarrhea/constipation) IBD and mimics which bacterial toxin?
X = linaclotide
Constipation
ETEC (diarrhea-induction via cGMP production and increased fluid/electrolyte secretion)
IBS patient with (X) symptoms is candidate for tricyclic antidepressant therapy.
X = diarrhea, nausea, abdominal pain
