Micro Pracs Semester 1 Flashcards
What is dysentery?
infection of the intestines resulting in severe diarrhoea with the presence of blood and mucus in the faeces.
How do the bacteria Staph aureus, Bacillus cereus, and Clostridium botulinum cause bacteria?
Symptoms are entirely due to the ingestion of toxins rather than the bacteria itself.
What are 2 examples of bacteria which cause GIT disease following ingestion (w/o inflamm)?
What kind of diarrhoea would result and why?
ETEC and Vibrio cholerae
Watery diarrhoea, due to the manufacture of toxins and growth of bacteria on the enterocyte surface
Example of bacteria which cause GIT disease following ingestion (w/ inflamm)?
Salmonella enterica; inflammatory response causes electrolyte and fluid loss into gut lumen.
Suspected agents of bloody diarrhoea?
EHEC, EIEC, Salmonella, Shigella and Campylobacter.
Dysentery (pus) seen in what bacterial GIT infection?
Shigella
(EHEC)
What tests do you consider for community acquired or travellers diarrhoea?
Test or culture for EHEC, Salomella, Campylobacter and Shigella
What tests do you consider for nosocomial (hospital acquired, >2 days after admission) diarrhoea?
- Clostridium difficile* (test for A and B toxins as it is a normal gut flora and its presence doesn’t necessarily indicate causative agent)
- Salmonella, Shigella, Campylobacter, EHEC* (shiga toxin producing E. Coli)
What tests do you consider for peresistent (>14 days) diarrhoea?
EPEC (pathogenic), EAEC
Protozoa: Giardia, Cryptosporidium, Cyclospora, Isospora belli
Screen for inflammation
HIV/AIDs
What pathogological agent causes typhoid fever?
Salmonella typhi
Antimicrobial treatment are appropriate in what Gastroenteritis/diarrhoea cases?
In the majority of cases bed rest and maintenance of fluid and electrolytes are all that is required.
Antibiotic therapy is appropriate for
- cholera
- protozoal infections
- pseudomembranous colitis
- systemic infections
e.g. typhoid fever, severe infections with Shigella and for immunocompromised patients.
What is the pathogenesis of HUS (haemolytic uremix syndrome) caused by EHEC?
EHEC doesn’t invade eneterocytes but stays inside the gut and replicates, producing Shiga toxins.
These toxins are able to cross the intestinal epithelial monolayer and spreas systemically via blood. They bind to Gb3 receptors on endothelial cells, enter the cell and inhibit protein synthesis in the cell (via inhibition of 60s ribosome subunit).
Paltelets beocme activated in an inflammatory response to death of the GI endotheial cells –> microthrombi, platelet consumption (thrombocytopaemia) and fragmentation of RBC’s (anaemia).
Also binds to other organs with the receptor (kidneys, CNS) –> AKI.
What do you test for in a patient with suspected coaelic disease?
- Test for antibodies (IgA) against deaminated gliadin peptides and tissue transglutaminase.
- HLA-DQ2 and HLA-DQ8 typing (useful for those patients with negative serology)
- Small bowel biopsy (the “gold standard”) – patients must be on gluten when the biopsy is taken
What treatment would be administered in a patient with a Giardia infection?
Metronidazole
What are your interpretation of the following viral hepatitis serology results:
HAV Ab (IgG) +
HAV Ab (IgM) +
HBsAg - not detected
HBs Ab- +
anti-HBc/HBc ab (IgG)- not detected
HBc Ab (IgM)- not detected
HCV Ab (IgG)- not detected
Patient has a recent acture viral hepatitis infection (HAV) indicated by the IgM +.
The patient has been vaccinated against HBV indicated by the + HBs Ab and the lack of anti-bodies agaisnt the core antigen (negative for HBc antibodies).
What is the most common pathogen associated with UTI?
E. coli
How much WBC suggests pyuria?
>104 WBC/mL
What quantity of bacteria in the urine is suggestive of infection?
What quantity from a supra-pubic aspirate?
>105 CFU/mL
Any growth from a supra-pubic aspirate is significant.
Antimicrobial treatment/Empiric therapy for community acquired UTI:
one of cephalexin, amoxycillin-clavulanic acid or trimethroprim
What is the difference between pyelonephritis and cystitis?
pyelonephritis- upper UT (especially kidneys)
cystitis- lower UT (bladder)
What is the difference between uncomplicated and complicated UTIs?
Uncomplicated- UTIs in otherwise normal hosts
Complicated- UTIs associated with anatomical abnormalities, metabolic abnormalities (pregnancy, diabetes), immunocompromise or unusual pathogens (e.g. yeasts).
Common bacterial causes of UTIs
E. coli (70-95%)
Staphylococcus saprophyticus (10% sexually active women)
Increasingly common in complicated UTIs: Proteus, Kelbsiella, Enterococci, Pseudomonas.
What are 2 very important factors in lab diagnosis of UTI?
- Specimen is uncomtaminated by normal flora (taken mid-stream and avoiding contact w/ skin)
- Specimen is transported ASAP (to restrict overgrowth and WBC lysis)
Define dysuria?
Painful, frequent urination
How do you work out how many WBC/mL you have using haemocytometer?
Count the number of WBC/square x 16 x 104
=WBC/mL
What are the features of E. Coli that allow it to cause UTI?
Fimbriae and adhesins to epithelial surfaces
What is the type of fimbriae in UPEC which allows it to cause pyelonephritis?
Type P fimbriae
What hormone in pregnancy is likely to contribute to increased UTI development?
Progesterone
What is the action of trimethoprim?
It is an antibiotic which works by inhibits dihydrofolate reductase, which causes the sequential block of folate synthesis in bacterial cells and a bacteriostatic effect.
As such, it is contraindicated for tx in UTIs for in early pregnancy.
To grow MTB you first use ____ to suppress normal flora growth. The medium used to culture MTB is ____ and is incubated for _____ weeks
Alkali
LJ 5 weeks
Would a patient with a MTB UTI be contagious?
No; not unless they are coughing which is how this TB spreads.
Tx of M TB
RIPES; 6 month AB course
R- Rifampicim
I- Isoniazid
P- Pyrazinamide
E- Ethambutol
S- Streptomycin
