Evaluation of Conventional PCR for Detection of Toxigenic Corynebacterium diphtheriae Strains in Malaysia

@#Diphtheria is an infectious but vaccine preventable disease caused by Corynebacterium diphtheriae and humans are the only reservoir. While toxigenic strains most frequently cause pharyngeal diphtheria, non-toxigenic strains commonly cause cutaneous infections. In 2016, there was a sudden increase in cases of C. diphtheriae reported in Malaysia. The toxigenic strains are currently determined using Elek’s test and are carried out only in the reference laboratory. With the sudden increase in diphtheria cases in Malaysia, it is important for local laboratories in state hospitals to be able to perform a rapid, reliable diagnostic test for the detection of the exotoxin. In this study, we aimed to evaluate the application of conventional PCR method to detect toxigenic strains of C. diphtheriae compared to the Elek’s test. Forty-eight C. diphtheriae strains were subjected to PCR detection of toxin gene A and B subunits, and also Elek’s test. The A and B subunits of the toxin gene were detected in all C. diphtheriae strains except for one strain which was isolated from a foot ulcer. Elek’s test was also positive for all the PCR positive strains. This study showed 100% corelation between the results of PCR and Elek’s test assay. The conventional PCR can be used at the state laboratories for rapid detection of toxin genes in toxigenic C. diphtheriae cultures, thus early treatment can be given to the patients while waiting for Elek’s test results.

Seroprevalance of brucellosis among suspected cases in Malaysia

Brucellosis is a zoonotic disease which can be transmitted by direct or indirect contact with infected animal or their products. It is an important public health problem but little is known on brucellosis in the Malaysian population. The aim of this study was to determine the presence of Brucella antibodies using commercial Brucella IgG and IgM ELISA kits (Vircell, SL, Barcelona Spain). A total of 184 sera from suspected patients were received from 16 hospitals in Malaysia over the years 2004 to 2009. Only 10 serum samples (5.4%) were positive for Brucella antibodies in which 5 showed the presence of both IgM and IgG. Most of the positive patients were occupationally involved with animals. This study suggests the seroprevalance of brucellosis among individuals who have contact with infected animals in Malaysia is low.

Enteropathogenic Escherichia coli in raw and cooked food.

A total of 402 Escherichia coli isolates were obtained from a variety of food samples and screened for enteropathogenic E. coli (EPEC). Screening was carried out using 15 specific monovalent antisera from Murex Diagnostic Limited. A total of 19 E. coli isolates were serotyped as EPEC. The EPEC strains were shown to belong to 8 serotypes. Eight out of 19 EPEC strains belonged to serotype 018C:K77 (B21). Seventeen out of 19 of the EPEC strains were isolated from cooked food. The presence of E. coli in cooked food is an indicator of fecal contamination and a sign of unhygienic food handling. The presence of EPEC in food could be a potential source of food-borne outbreak. Hygiene training for every food-handler is a necessity.

Indirect hemagglutination antibodies against Burkholderia pseudomallei in normal blood donors and suspected cases of melioidosis in Malaysia.

Interpretation of the indirect hemagglutination test (IHA) for melioidosis in endemic areas is difficult because of the presence of antibodies in apparently healthy individuals. Fifty-three out of 200 healthy blood donors in Malaysia showed positive antibody titers (> or = 1 : 40) against Burkholderia pseudomallei. Seven percent had an IHA titer of 1 : 40, 11% had an IHA titer of 1 : 80 while 8.5% had a titer > or = 1 : 160. Out of 258 sera sent for melioidosis serology, 7% of the patients had an IHA titer of 1 : 40, 9% had an IHA titer of 1 : 80 while 20% had an IHA titer of > or = 1 : 160. If a titer of > or = 1 : 80 is taken as cut off point for positivity, 29% of the patients had positive melioidosis serology. Increasing the positivity threshold may jeopardize the sensitivity of the test. A more specific and sensitive test is needed.