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

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.

Virological investigation of fatal rabies in a minor bitten by a mongrel in Nigeria

Rabies is a deadly viral disease transmitted through bites of infected animals. Outbreaks continue to escalate in Africa, with fatalities in humans, especially in rural areas, but are rarely reported. About 40% casualties occur among children of < 15 years. A 5-year-old boy on referral from a Primary Health Care Centre to a tertiary hospital presented with anxiety, confusion, agitation, hydrophobia, photo-phobia and aero-phobia, seven weeks after he was bitten by a stray dog in a rural community in Nigeria. The patient did not receive post-exposure prophylaxis and died 48 hours post admission. Confirmatory diagnosis was rabies and the phylogenetic analysis of the partial N-gene sequence of the virus localized it to Africa 2 (genotype 1) Lyssaviruses. There was 95.7-100% and 94.9-99.5% identity between the isolate and other genotype 1 Lyssaviruses and 100% homology with rabies viruses from Mali, Burkina Faso, Senegal and Central African Republic.

Clarifying Indeterminate Results on the Rabies Direct Fluorescent Antibody Test Using Real-Time Reverse Transcriptase Polymerase Chain Reaction

OBJECTIVES

Each year, rabies virus infection results in the death of more than 50 000 persons worldwide. In the United States, the Centers for Disease Control and Prevention (CDC) reported 23 human rabies cases from May 1, 2008, through October 1, 2017. Although rabies testing in the United States is highly reliable, some specimens submitted to rabies laboratories do not have adequate tissues or may be substantially decomposed. In these instances, the specimen may be considered unsatisfactory for testing or produce indeterminate results using the gold standard direct fluorescent antibody test. The objective of this study was to evaluate the number of unsatisfactory samples or samples with indeterminate results that were positive for rabies virus after additional testing using real-time reverse transcriptase polymerase chain reaction (RT-PCR).

METHODS

In 2016, we retested all unsatisfactory specimens or specimens with indeterminate results using real-time RT-PCR. We further typed any sample that was real-time RT-PCR positive to identify the infecting rabies virus variant.

RESULTS

Of 210 retested unsatisfactory specimens or specimens with indeterminate results, 9 (4.3%) were positive for rabies. In each case, the animal was infected with a homologous rabies virus variant.

CONCLUSION

These results confirm the recommendation by CDC and state public health laboratories that indeterminate results should be considered positive and justify the prompt treatment of exposed persons through an animal that is suspected to have rabies.

Comparative assessment of seller's staining test (SST) and direct fluorescent antibody test for rapid and accurate laboratory diagnosis of rabies

BACKGROUND

Rabies causes 55, 000 annual human deaths globally and about 10,000 people are exposed annually in Nigeria. Diagnosis of animal rabies in most African countries has been by direct microscopic examination. In Nigeria, the Seller's stain test (SST) was employed until 2009. Before then, both SST and dFAT were used concurrently until the dFAT became the only standard method.

OBJECTIVE

This study was designed to assess the sensitivity and specificity of the SST in relation to the 'gold standard' dFAT in diagnosis of rabies in Nigeria.

METHODS

A total of 88 animal specimens submitted to the Rabies National Reference Laboratory, Nigeria were routinely tested for rabies by SST and dFAT.

RESULTS

Overall, 65.9% of the specimens were positive for rabies by SST, while 81.8% were positive by dFAT. The sensitivity of SST in relation to the gold standard dFAT was 81.0% (95% CIs; 69.7% - 88.6%), while the specificity was 100% (95% CIs; 76% - 100%).

CONCLUSION

The relatively low sensitivity of the SST observed in this study calls for its replacement with the dFAT for accurate diagnosis of rabies and timely decisions on administration of PEP to prevent untimely deaths of exposed humans.