MMIC Blog 2 - Case 6

[A follow-up on my patient, Ong Fei Fei's investigation]


Laboratory Diagnosis

Since the patient has been previously diagnosed with UTI, the microbe could have move down and infect the vagina as well, hence urethra microbes are considered in this case too, for examples:

E. coli
Proteus mirabilis
S. saprophyticus
Group B streptococci (Alpha & non-hemolytic)
Coagulase-negative Staphylococci (S. aureus)
Klebsiella species
Proteus species
Pseudomonas aeruginosa
Enterobacteraceae

(Follow how UTI microbes are identify in other cases - see debra's and/or elaine's)


As for more vaginal-specific microbes, they are the followings:


Trichomonas Vaginalis

• Wet mount preparation then Direct microscopy



• Motile characteristic



• Greater sensitivity: Fixed stained preparation (Giemsa/Papanicolaou) then Direct Immunofluorescence



• Culture (Diamond’s medium) then incubate at 37oC à microscopy



• Antibody detection techniques: high in false positive and false negative results



• Enzyme immunoassay for detection of T. vaginalis antigen

Candida Albicans

• Gram’s stain then Direct Microscopy



• Sabouraud’s agar then Incubate 24-48 hours. white, butyrous colonies observed if positive
  

Bacterial Vaginosis (anaerobic/non-specific)

• Clue cells (Vaginal epithelial cells with edges darkened by presence of numerous small bacteria adhering to their surface)



• pH (>4.5)



• Amine test: add few drops of KOH and presence of amines gives a fishy smell



• Gram’s stain



• Culture: for Gardnerella vaginalis and Mobiluncus species

1. Gardnerella vaginalis

Aerobic
Gram-variable
Bacillus
Slow growing
Non-motile
Catalase and oxidase negative
Beta-hemolysis on human blood agar but not on sheep blood agar
Selective blood agar: add gentamicin, nalidixic acid and amphotericin B
Hippurate hydrolysis: positive
Starch fermentation: positive
Metronizadole 50ug disc: sensitive
Sulphonamide 1000ug dsc: resistant


2. Mobiluncus species

Anaerobic
Gram-variable
Bacillus
Divided into: M. curtisii and M. mulieris
Fastidious; slow growing
Typically motile, catalase, oxidase, indole negative
Clear, colourless colonies (2mm) after 5 days incubation
Gas-liquid chromatography distinguish species
Commercial kit: detect enzyme activity (praline aminopeptidase and alpha-D-glucosidase)


3. Neisseria Gonorrhoea

Die readily outside human body
Fastidious
Use of rich media supplemented with yeast extract or iso-viatalex and blood (Chocolate agar)
Antibiotic inhibitors: vancomycin, nystatin, colistin, trimethoprim
Direct Microscopy (less sensitive for women – 50%)
Culture
Other technique: Direct immunofluorescence


4. Chlamydia trachomatis

[Direct examination of smear with fluorescein-conjugated monoclonal antibodies(Ab) (use of commercial kits)]

Roll specimen gently on slide
Fix with methanol for 4 min
2 Ab (one directed to the outer membrane – species specific, one specific to the genus lipopolysaccharide)
Subjective/ false positive
Suitable for small sample numbers and rapid screening


[Culture]

Uses McCoy’s cells treated with cyclohexamide
Centrifuged and incubate for 72 hours
Detection by Giemsa stain/iodine/fluorescein-labeled monoclonal Ab
Sensitivity: ~80%


[Enzyme-linked immunoabsorbent assays (ELISA)]

Uses polyclonal and monoclonal antibodies against lipopolysaccharide (Antigen detection)
Sensitivity: ~97%; Specificity: ~92.5% (improves by blocking tests)
False positive due to cross reactivity with other bacteria


[Nucleic acid probes]

DNA hybridization
Highly specific but lack sensitivity


[Serology]

Complement fixation tests are insensitive; difficult to differentiate the serotypes
Micro-immunofluorescence test detect specific IgG/IgM; difficult in sexually active populations



Summary Diagrams






























Other Investigation required


Urinalysis - for screening purpose; inexpensive and easy to perform (previously confirmed UTI)
Urine culture - for accurate diagnosis of infection to determine complications, such as antimicrobial susceptibility of infecting bacteria (previously confirmed UTI)


References

http://www.escriber.com/ > TrendsInUGSH > Features

http://www.cfps.org.sg/ > sfp > 23 > 232> articles > e232136.html

http://cks.library.nhs.uk/ > uti_lower_women > in_depth > goals_and_outcome_measures

http://www.merck.com/ > mmpe > sec17 > ch231 > ch231b.html

http://www.aafp.org/ > afp > 20020415 > 1589.pdf

http://books.mcgraw-hill.com/ medical > firstaidfortheboards > pdf > 0071443363 > 0071443363_282.pdf

http://classes.kumc.edu/ son > nrsg835 > gyninfect.htm



Posted by: Pei Shan, TG02