Microbiological Examination for Urinary Tract Infection (UTI) and Sexually Transmitted Infection (STI)
|← Block C4 - Adolescence and Adulthood|
|Office:||4th floor, Radiopoetro.|
|Lab:||4th floor, Radiopoetro.|
|Pre-test:||10 questions, true-false.|
- Most UTI are caused by aerobic Gram negative bacteria, usually from the Enterobacteriaceae family, such as E.Coli which causes 80% of UTI.
- Other bacteria that cause UTI are Klebsiella sp., Proteus sp., Enterobacter sp., Pseudomonas sp., and Staphylococcus sp.
- Diabetes mellitus, bladder catheterization, and immunosuppressive drugs increase risk of UTI.
- UTI when ≥10⁵ colony forming units (CFU) per ml. This means, over 200 colonies.
- CFU/ml = (number of colonies per plate) x (dilution factor reciprocal) x 1/(aliquot)
- Clean-catch/midstream: a sample of urine as clean as possible without using a catheter. The external genital area is cleaned with soap. The patient urinates a little bit into the toilet and then stops. This first bit of urine is to rinse out the inside of the urethra before collection of the sample. Then, the patient positions the collection container into place and then urinates into it.
- Diagnosis of UTI must be based on bacteriologic examination and cannot be determined by just the turbidity, odor, specific gravity, or pH.
- Urethritis means urethral inflammation. It can be caused by infectious and noninfectious conditions.
- Symptoms of urethritis: mucopurulent or purulent material, dysuria, and urethral pruritis. Urethritis may be asymptomatic too.
- Urethritis is often caused by N. gonorrhoeae and C. trachomatis. (These two also cause STI).
- Neisseria is a genus with two main pathogens: N. meningitidis and N. gonorrhoeae.
- N. meningitidis has low prevalence but high mortality.
- N. gonorrhoeae is a Gram-negative coccus, 0.6 to 1.0 µm in diameter, with fimbrae. It is found (intracellularly) in pmn cells (neutrophils) in gonorrhea pustular exudate.
- To diagnose gonorrhea:
- Evaluation of presenting symptoms and sexual history.
- Gram stain of urethral exudates.
- Culturing of N. gonorrhoeae.
- Gonorrhea is a major cause of urethritis in men and cervicitis in women (which can result in PID, infertility, and ectopic pregnancy).
- Gonorrhea is usually acquired sexually and involves mucous membranes of the urethra, and thus results in lots of pus (i.e. Pyogenic).
- N. gonorrhoeae metabolizes glucose aerobically, using the Entner-Doudoroff and pentose phosphate pathways. As a result, acetic acid and some lactic acid is produced. This reduces the pH of the medium.
- To differentiate the different species of Neisseria, their carbohydrate (glucose, maltose, lactose, sucrose, and fructose) fermentation patterns are used. (See table below).
|Neisseriae bacteria||Growth on MTM medium||Glucose||Maltose||Lactose||Sucrose or Fructose||DNAse|
As is usual for Microbiology, this was a true-false based test with 10 questions. The following questions come from more than one session and that is why there are more than ten questions listed.
- N. Gonorrhoeae is diplococci and stains red. False. It does not stain red.
- Pseudomonas is the primary cause of UTI. False.
- A transport medium may be used to send samples to a microbiology lab.
- A catheter bag may be used for urine sample. False. The urine in a bag may already be old. The sample needs to be fresh.
- Nasseria can grow on blood agar. False. Blood agar only allows Gram-positive bacteria to grow.
- Nasseria can grow on McConkey agar. True.
- Females are usually asymptomatic when infected with gonorrhea.
- (Calculation for streak method)
- (Calculation for pour method)
- A great majority of UTI produce symptoms.
- A suprapubic sample of urine is 10 CFU, it is clearly not infection.
- Enterobacteriase is responsible for UTI. True.
- Anarobic bacteria is responsible for UTI.
- Diabetes mellitus is a risk for UTI. True.
- N. gonorrhea is more dangerous than N. meningitidis. False. N. Meningitidis is more fatal even though the prevalence is low.
The final Microbiology exam for block 2.4 for batch 2011 consisted of 25 questions and written in Ruang Kuliah with one to four questions per slide (on the projector) with a mix of short-answer, multiple-choice, and true-false. The total time allocated for the exam was 20 minutes. Questions focused on the ability to histologically identify N. gonorrhoeae and E. coli, know at least three species in Enterobacteriaceae, prevalence and mortality rate of N. meningitidis and N. gonorrhoeae, knowing that a yellow tube means positive and a red tube means negative, the primary site of infection for N. gonorrhoeae in males and females, identifying and calculating using both pour plate and streak method, identifying the loop and its purpose in the streak method, three drugs for the treatment for N. gonorrhoeae, knowing clean-catch/midstream, knowing that MacConkey is suited for N. gonorrhoeae, and calculations for both the pour method and the streak method (memorize the interpretation table).