Term
| Giardia can exist in these two forms: |
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Definition
| Cyst and trophozoite, cysts in contaminated drinking water are the infective form |
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Term
| This is the most common presentation of giardiasis in the US |
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Definition
| Asymptomatic infection, 5% of US adults harbor giardia |
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Term
| True or false: Giardia invades the mucosal epithelium of the small bowel, causing bloddy diarrhea |
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Definition
| False, Giardia remains a luminal presence in the GI tract, adhering to the wall of the intestine and causing a secretory diarrhea |
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Term
| In addition to causing secretory diarrhea, what else is common of stools in symptomatic giardiasis? |
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Definition
Fatty stools, giardia destroys the brush border enzymes and microvilli of the small intestine, decreasing fat absorption and leading to fatty smelly stools
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Term
| How many trophozoites form for a giardial cyst? |
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Definition
| 2 binucleated trophozoites with 4 flagella each |
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Term
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Definition
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Term
| In addition to contaminated municipal drinking water, what other contamination can spread giardia? |
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Definition
| Rodents can be a reservoir for the organisma, and their fecal contamination of streams and rivers can spread giardia if the water is consumed |
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Term
| True or false: profound weight loss (10% of bw or greater) can distinguish giardiasis from other causes of acute diarrhea |
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Definition
| True, in both acute and chronic giardiasis marked weight loss occurs along with nausea, bloating, cramping and aforementioned diarrhea |
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Term
| How is giardia diagnosed? |
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Definition
| Look for cysts in the stool, can also do antigen detection from stool specimens |
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Term
| What is the preferred tx for giardiasis? |
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Definition
| Metronidazole, forms cytotoxic compounds within the protozoan that denatures proteins and DNA, leading to cell death |
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Term
| What are two important side effects of metronidazole? |
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Definition
| Disulfaram reaction, with EtOH causes a bad hangover, and a metallic taste in the mouth |
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Term
| What other protozaon enteric infection is metronidazole used to tx? |
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Definition
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Term
| Along with Enterotoxigenic E. coli and rotavirus, this bacteria is one of the leading causes of diarrhea worldwide |
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Definition
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Term
| True or false: Erythromycin is recommended as first-line tx of campylobacter infection |
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Definition
| False, erythromycin is the drug of choice but abx are rarely indicated for this infection, instead hydration and correction of electrolyte imbalances are preferred tx |
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Term
| True or false: the preferred method for campylobacter diagnosis is culture |
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Definition
| True, selective medium 5-10% oxygen with 1-2% CO2 and hydrogen, 42-43 degrees C (thermophilic) |
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Term
| True or false: Campylobacters are oxidase and catalase negative |
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Definition
| False, both are present and their presence must be noted for a confirmatory diagnosis |
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Term
| True or false: campylobacter is a zoonotic, found in wild, domesticated mammals and poultry |
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Definition
| True, transmission is fecal-oral, communicability is limited |
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Term
| Campylobacters use these structures on their membrane to attach to intestinal cells, then secrete toxins to facilitate entry into cells |
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Definition
| Fimbriae, they secrete a labile toxin similar to E. coli though its role in pathogenesis is still unclear |
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Term
| Campylobacters appear this color in a gram stain microscope image |
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Definition
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Term
| True or false: persons taking PPI or consuming dairy are more susceptible to campylobacter infection |
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Definition
| True, campylobacters are susceptible to stomach acidity, so decreasing acidity increases the chance of transmission |
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Term
| True or false: A person who eats contaminated chicken and develops fever and malaise the next day, with bloody diarrhea occuring 3-7 days after, is likely to have campylobacter infection |
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Definition
| True, the incubation period is about 3 days, the fever and malaise are a prodrome |
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Term
| True or false: diarrhea due to campylobacter is usually self limited |
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Definition
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Term
| True or false: Campylobacter is a cause of reactive arthritis |
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Definition
| True, 20% of patients will develop polyarthritis 2-4 weeks after diarrhea ceases |
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Term
| T or F: The frequency of spontaneous mutations (for drug targets or transport mechs) is between 10^-7 and 10^-9 for any bacterial organism. |
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Definition
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Term
| Spontaneous mutations in bacteria are an example of what type of resistance? |
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Definition
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Term
| What three reasons determine the clinical importance of plasmid mediated resistance? |
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Definition
| It is widespread, especially among gram neg. rods. Plasmids mediate resistance to multiple drugs, and they have a high transfer rate and can be transferred inter-species. |
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Term
| These factors may carry multiple antibiotic resistance genes and can replicate independently of the bacterial chromosome and can be transferred to outside species. |
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Definition
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Term
| These resistance modulators are small genes that can be transferred on or within larger pieces of DNA |
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Definition
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Term
| Give 4 mechanisms that mediate bacterial resistance and an example of each |
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Definition
| 1) Inactivating enzymes like B-lactamases in S. aureus, 2) Modified drug target synthesis like a mutation in the 30S ribosomal subunit that prevents aminoglycoside binding, 3) Decreased membrane permeability as in porin protein changes that prevent abx entry and 4) Efflux pumps that exchange protons for foreign molecules like quinolones |
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Term
| Give an example of a drug resistance mechanism for Beta lactams (vanco, penicillin etc.) |
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Definition
| Beta lactamases (most important) PBPs and reduced membrane permeability |
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Term
| Give an example of a drug resistance mechanism for vancomycin specifically |
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Definition
| Mutation of DalaD peptide in cell wall peptidoglycan to DlacD preventing binding |
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Term
| Give an example of a drug resistance mechanism for aminoglycosides |
|
Definition
| Modification of drug by bacterial enzymes, mutation in 30s ribosomal subunit gene, reduced permeability |
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Term
| Give an example of a drug resistance mechanism for tetracyclines |
|
Definition
| Reduced permeability and reduced active transport into bacterial cells |
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Term
| Give an example of a drug resistance mechanism for erythromycin |
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Definition
| Plasmid encoded enzyme methylates 23s ribosomal RNA blocking drug binding |
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Term
| Give an example of a drug resistance mechanism for sulfonamides |
|
Definition
| Plasmid encoded enzymes actively export drug from bacterium |
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Term
| Give an example of a drug resistance mechanism for (fluoro)quinolones |
|
Definition
| Mutation in gene encoding DNA gyrase |
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Term
| Give an example of a drug resistance mechanism for rifampin |
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Definition
| Mutation in gene encoding bacterial RNA polymerase |
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Term
| Give an example of a drug resistance mechanism for INH |
|
Definition
| Loss of bacterial peroxidase (catalase) that activates isoniazid |
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Term
| True or false: an example of synergism, penicillin and gentamicin are often given together as penicillin damages the cell wall to enable more gentamicin to enter the cell. Give another example. |
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Definition
|
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Term
| True or false: gentamicin and penicllin are antagonistic and should never be given together |
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Definition
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Term
| True or false: Like gentamycin, tetracycline is often given with penicillin for synergistic effects |
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Definition
| False, tetracyclines are bacteriostatic and reduce bactericidal killing in pneumococcal infections |
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