Molecular study on metronidazole resistance in Bacteroides fragilis group isolates from a South Indian tertiary care center.

OBJECTIVE: Bacteroides species are an important part of human intestinal microbiota. They can cause infections of significant mortality and morbidity when moved out of their niche in the gut. The cornerstone drug for prophylaxis and therapy, metronidazole, is exhibiting signs of resistance, which are frequently attributed to nitroimidazole (nim) resistance genes. The aim of this study was to use Epsilometer test (E-test) to assess the metronidazole susceptibility and conventional PCR methodology to map the distribution of nim genes in Bacteroides fragilis group (BFG) isolates. METHODS: MALDI-TOF MS was used to identify BFG isolates. Using the E-test methodology, metronidazole minimum inhibitory concentrations (MICs) were determined. The presence of nim genes in these isolates were checked by conventional PCR methodology. Sequencing was done on selected amplicons for determining the nim gene types. RESULTS: Bacteroides fragilis accounted for 55.3% of the total 273 BFG members identified. Of these, 196 (71.8%) were susceptible, 43 (15.8%) intermediate and 34 (12.5%) resistant to metronidazole as determined by the E-test. nim gene was present in 101 (37%) of the total 273 isolates. Out of the 34 phenotypically resistant isolates (MIC ≥32 µg/ml), 29 harboured nim gene (Chi-square test, p < 0.0000001) but nim gene was absent in 5 (14.7%) isolates. Also, nim gene was detected in 72 (30.1%) of the 239 isolates with susceptible and intermediate metronidazole MIC. Sequencing of 20 amplicons gave a nimE gene type. CONCLUSIONS: In view of the rising metronidazole resistance among BFG and its close association with nim genes, there is a need for implementing routine metronidazole susceptibility testing and more researches are needed to find the molecular basis of these nim genes.

Case Report: Bloodstream Infection with Toxigenic Corynebacterium diphtheriae and Gram-Negative Sepsis in a Child with Burns.

Corynebacterium (C.) diphtheriae is the agent for a contagious infection, diphtheria. It may manifest as pharyngitis with pseudomembrane formation and cervical lymphadenopathy, cutaneous infection, or as an asymptomatic carrier. Corynebacterium (C.) diphtheriae is not an invasive organism and it remains in the superficial layers of skin lesions and respiratory mucosa. Systemic complications, such as bacteremia, are rare. We report a case of toxigenic C. diphtheriae detected from blood culture of a 1-year-old male patient with burns, who succumbed to the infection after 8 days of stay in the hospital. Patient did not have specific clinical features suggestive of diphtheria. Initial identification of C. diphtheriae was done based on culture, Albert stain findings, biochemical tests and subsequently toxigenicity testing was done by polymerase chain reaction. Although diphtheria vaccination in infancy is universally recommended since the creation of the Expanded Program on Immunization in the 1970s, there have been reports of toxigenic strains of C. diphtheriae in a considerable number of cases. Rapid and accurate identification of C. diphtheriae infection is crucial to prevent mortality. Continued surveillance for diphtheria is needed to reduce transmission and mortality rates.