Virulence factors in clinical and commensal isolates of Enterococcus species.

BACKGROUND: Enterococci have emerged as important nosocomial pathogens and have been found to possess many virulence factors, some of which are considered very important in the pathogenesis of diseases caused by them. The following study was carried out to evaluate some of the virulence determinants elaborated by strains of enterococci in our setup and to ascertain if these strains differ considerably from commensal strains of enterococci in the expression of these virulence determinants. MATERIALS AND METHODS: One hundred and fifty-seven isolates of Enterococcus species from clinical specimens were evaluated for the presence of virulence determinants like hemolysin production, gelatinase production and biofilm formation by phenotypic tests. The presence of enterococcal surface protein (esp) gene in the isolates was detected using polymerase chain reaction (PCR). Thirty strains of Enterococcus isolated from fecal samples of patients admitted to the hospital were also tested for the presence of these virulence factors. Strains of Enterococcus from clinical specimens and those present as commensals were compared with respect to the elaboration of virulence factors using Fisher's exact test. RESULTS: The association between biofilm formation and presence of the "esp" gene was not found to be statistically significant. Among the virulence determinants studied, gelatinase production and the "esp" gene were found to be significantly more common in clinical isolates than commensal strains of Enterococcus species. CONCLUSION: Among the virulence factors, gelatinase and the "esp" gene were more common in clinical isolates than commensal strains. The association between biofilm formation and the presence of "esp" gene was not found to be statistically significant.

Outcome of ventilator-associated pneumonia: Impact of antibiotic therapy and other factors.

BACKGROUND: Ventilator-associated pneumonia (VAP) is the most frequent infection in patients intubated for longer than 48 hours. There is a great interest in determining the factors influencing the outcome of VAP, as it may help in reducing the associated morbidity and mortality. This study aimed to determine the impact of appropriate antibiotic therapy based on endotracheal aspirate cultures on the outcome of VAP. We have also studied the other factors that may influence the outcome of VAP. METHOD: A cohort study was conducted in the intensive care units of a tertiary care hospital in South India over a period of 15 months. The outcome of VAP was assessed by prolongation of the duration of mechanical ventilation and/or death of the patient. RESULTS: The duration of mechanical ventilation was significantly prolonged in patients with VAP (16.61 ± 8.2 d vs. 8.21 ± 5.9 d, P < 0.0001). VAP patients receiving partially or totally inappropriate therapy (defined as lack of coverage of one or all the significant VAP pathogens) were at significantly high risk for death (Relative risk, 2.00; 95% confidence interval, 1.14 to 3.52; P 0.0008). A delay of > 2 days in administering the first dose of appropriate antibiotic therapy significantly prolonged the duration of ventilation (P < 0.0001). Infection by multi-drug resistant pathogens, polymicrobial infection and time of onset of VAP did not have significant impact on the outcome of VAP. CONCLUSION: Early administration of appropriate antibiotic therapy, based on the antibiogram of the VAP pathogens identified by quantitative culture of endotracheal aspirate, could lead to an improved outcome of patients with ventilator-associated pneumonia.

Role of bone biopsy specimen culture in the management of diabetic foot osteomyelitis.

INTRODUCTION: There has been increasing evidence in favor of conservative management of diabetic foot osteomyelitis which requires targeted antibiotic therapy to the causative pathogen. But the method of reliable microbiological isolation is controversial. AIMS AND OBJECTIVES: To study the concordance of superficial swab culture with bone biopsy specimen culture in patients with diabetic foot osteomyelitis. MATERIALS AND METHODS: A prospective study was conducted from July 2008 to July 2010. All consecutive patients with suspected diabetic foot osteomyelitis were included in the study. Superficial swab and Percutaneous bone biopsy specimens were obtained for culture. The culture results in these two groups were compared for concordance. RESULTS: A total of 144 patients were included in the study. 134 cases of bone biopsy specimen and 140 cases of superficial swab showed positive culture results. Mean number of isolate per sample was similar. Staphylococcus aureus was the commonest organism grown in both cultures. The bone pathogen was identified in the corresponding swab culture in only 55 cases (38.2%). Staphylococcus aureus had the highest concordance percentage of 46.5% which was not statistically significant. CONCLUSION: Superficial swab culture may not be accurate in identifying all the organisms causing diabetic foot osteomyelitis. Bone biopsy specimen taken simultaneously would increase the accuracy of detecting the bacterial isolate.

Wound infections secondary to snakebite.

BACKGROUND: The study was performed to identify the important bacterial pathogens responsible for wound infections secondary to snakebite and to determine their antimicrobial susceptibility. METHODOLOGY: All cases of wound infection secondary to snakebite were included in this retrospective study. Infected tissues were surgically debrided and inoculated on blood agar and MacConkey agar for aerobic bacterial culture, followed by antimicrobial susceptibility testing of the isolates by Kirby-Bauer disk diffusion method. RESULTS: Staphylococcus aureus (32%) was the most common isolate followed by Escherichia coli (15%); monomicrobial infections were more frequent than polymicrobial infections. The majority of the isolates were antibiotic sensitive. Ciprofloxacin, an oral drug covering both Gram-positive and Gram-negative isolates, was the most frequently prescribed antibiotic. The patients responded well to the treatment. CONCLUSION: The results of this study will be helpful in deciding the empirical antibiotic therapy in cases of wound infection secondary to snakebite in regions of Southeast Asia.