Study of gonococcal and chlamydial urethritis: Old culprits with a new story

Abstract

Introduction: Neisseria gonorrhoeae and Chlamydia trachomatis are the primary pathogens causing urethritis. A cross-sectional study was carried out in the Department of Microbiology in conjunction with the Department of Dermatology and STD of our hospital. The aim of the study was to detect N. gonorrhoeae and C. trachomatis among men with urethritis and to determine the anti-microbial susceptibility of the N. gonorrhoeae isolates.

Material and methods: All cases were subjected to direct Gram's smear examination and culture of urethral discharge (N. gonorrhoeae), real-time polymerase chain reaction and direct fluorescent antibody test (C. trachomatis). All N. gonorrhoeae isolates were subjected to anti-microbial susceptibility testing and were tested for ß-lactamase production by chromogenic cephalosporin test.

Statistical analysis used: Data were expressed as percentages. Fisher's exact test was used to evaluate statistical significance in the case of unpaired categorical data. Agreement between the methods was assessed by using kappa statistics.

Results: Gonococcal infection was detected in 58.1% cases, and C. trachomatis was detected in 14% cases. However, both were detected in 12% cases. The sensitivity, specificity, positive predictive value, and negative predictive value of direct Gram's smear examination and culture of urethral discharge were found to be 100% when compared to culture for N. gonorrhoeae. Direct fluorescent antibody (DFA) test proved to be a valuable test aiding in the diagnosis of chlamydial urethritis with a majority of positive cases showing 20-30 elementary bodies. We detected our first gonococcal isolate with decreased susceptibility to third-generation cephalosporins, ceftriaxone, cefixime, and cefpodoxime (MIC for ceftriaxone = 0.19 mg/ml).

Conclusions: Optimal management of urethritis and strategies to prevent its transmission depend on accurate detection of infected persons. Our study demonstrates the utility and limitations of different laboratory tests including anti-microbial sensitivity testing for N. gonorrhoeae and C. trachomatis.

Keywords: Anti-microbial sensitivity testing; Chlamydia trachomatis; Neisseria gonorrhoeae; direct fluorescent antibody test; modified Thayer Martin medium; real-time PCR.

Figure 1

Etiology of urethritis among study subjects

Figure 2

(a) Direct Gram-stained smear of urethral discharge showing intra-cellular Gram-negative diplococci within polymorphonuclear leucocytes; (b) growth of N. gonorrhoeae on MTM; (c) MicroTrak^® Chlamydia trachomatis Direct Specimen-Positive Test slide showing apple-green fluorescent elementary bodies in a background of brick-red columnar/cuboidal epithelial cells

Figure 3

Anti-microbial susceptibility profile of the gonococcal isolates