Balvinder Mohan

Comparative analysis of virulence determinants, antibiotic susceptibility patterns and serogrouping of atypical enteropathogenic Escherichia coli versus typical enteropathogenic E. coli in India.

The epidemiology of enteropathogenic Escherichia coli (EPEC) and the significance of isolation of atypical EPEC (aEPEC) in childhood diarrhoea have not been well studied in an Indian context. A comparative study was undertaken to investigate virulence determinants, antibiotic susceptibility patterns and serogrouping of typical EPEC (tEPEC) versus aEPEC causing diarrhoea in children. A total of 400 prospective and 500 retrospective E. coli isolates were included. PCR was performed for eae, bfpA, efa, nleB, nleE, cdt, ehxA and paa genes. The Clinical and Laboratory Standards Institutes disc diffusion test was used to determine the antimicrobial susceptibility. Phenotypic screening of extended spectrum β-lactamases (ESBLs), AmpC and Klebsiella pneumoniae carbapenemase (KPC) production, and molecular detection of bla(NDM-1), bla(VIM), bla(CTX-M-15), bla(IMP) and bla(KPC) were performed. aEPEC (57.6 %) were more common as compared with tEPEC (42.3 %). The occurrence of virulence genes was observed to be three times higher in aEPEC as compared with tEPEC, efa1 (14.7 % of aEPEC, 4 % of tEPEC) being the most common. Most of the isolates did not belong to the classical EPEC O-serogroups. The highest resistance was observed against amoxicillin (93.22 %) followed by quinolones (83 %), cephalosporins (37.28 %), cotrimoxazole (35.59 %) and carbapenems (30.5 %). Overall equal numbers of aEPEC (41.17 %) and tEPEC (40 %) were observed to be multidrug-resistant. Fifteen EPEC strains demonstrated presence of ESBLs, five produced AmpC and four each produced metallo-β-lactamases and KPC-type carbapenemases; eight, seven and one isolate(s) each were positive for bla(VIM), bla(CTX-M-15) and bla(NDM-1), respectively. Here, to the best of our knowledge, we report for the first time on carbapenem resistance and the presence of bla(NDM-1) and bla(CTX-M-15) in EPEC isolates from India.

Occurrence of blaNDM-1 & absence of blaKPC genes encoding carbapenem resistance in uropathogens from a tertiary care centre from north India

Background & objectives: Carbapenem resistance mediated by carbapenemases is increasingly being reported worldwide. This study was conducted to know the occurrence of important carbapenem resistance encoding genes in Gram-negative bacilli (GNB) causing complicated urinary tract infection (CUTI), and to look at the genetic diversity of these isolates. Methods: The study was carried out on 166 consecutive carbapenem resistant uropathogens (CRU) isolated from cases with CUTI during 2008 and 2012. Carbapenemase production was characterized phenotypically and polymerase chain reaction was used to detect blaVIM, blaIMP, blaKPC, and blaNDM-1. BOX- PCR was done on 80 randomly selected isolates for molecular typing. Results: The blaVIM gene was present in 34 (43.6%), blaIMP in five (6.4%) and none of the isolates from 2008 had blaNDM-1 or blaKPC genes. Among the isolates from 2012, blaNDM-1 gene was present in 47 (53.4%), blaVIM in 19 (24.4%), blaIMP in one (1.1%) and none had blaKPC. There were nine isolates during the two years which had multiple genes encoding carbapenemases; while 66 did not have any of the genes tested. Of the 80 isolates subjected to BOX-PCR, 58 could be used for analysis and showed, presence of multiple clusters of carbapenem resistant isolates and absence of a single dominant clone. Interpretation & conclusions: The blaNDM-1 gene was absent in our isolates obtained during 2008 but was present amongst Enterobacteriaceae isolated in 2012. The blaKPC gene was also not found. Nine isolates obtained during the two years had multiple genes encoding carbapenemases confirming the previous reports of emergence of GNB containing genes encoding multiple carbapenemases. Typing using BOX-PCR indicated that this emergence was not because of clonal expansion of a single strain, and multiple strains were circulating at a single point of time.

Pyonephrosis due to Chryseobacterium gleum: A first case report

Chryseobacterium spp are widely distributed in nature but data of their isolation from clinical samples is scanty. Here, we report the first case of AmpC producing C. gleum causing pyonephrosis in a patient having bilateral nephrolithiasis on double J (DJ) stent. The present isolate was resistant to vancomycin, erythromycin, clindamycin, carbapenems and ciprofloxacin and susceptible to tetracycline and minocycline. The patient was treated with tetracycline and recovered without the need for removal of the DJ stent. The environmental surveillance carried out to trace the nosocomial origin of the isolate was negative. Since antimicrobial susceptibility of this isolate is different from previous reports, we emphasise that in vitro susceptibility testing should be sought to choose optimal antimicrobial agents for these Nonfermentative Gram-Negative Bacilli (NFGNBs) with different susceptibility patterns.

Serotype profile and molecular characterization of antimicrobial resistance in non-typhoidal Salmonella isolated from gastroenteritis cases over nine years.

Resistance to third-generation cephalosporins in non-typhoidal Salmonella (NTS) is emerging worldwide. We report the occurrence of extended-spectrum beta-lactamase (ESBL) phenotypes in 53.4 % of NTS isolated over a period of nine years from gastroenteritis cases. ESBL and AmpC co-production was observed in 21 % of the isolates. Occurrence of blaCTX-M-15 and blaCMY-2 resistance genes was observed in 11.6 % and 37 % of the isolates respectively. Overall, Salmonella enterica serovar Senftenberg was the predominant serovar carrying blaCTX-M-15 and blaCMY-2 resistance genes. We report for the first time from India, one isolate each of S. enterica serovar Thompson, S. enterica serovar Infantis and S. enterica serovar Newport, carrying the blaCTX-M-15 gene. We also report for the first time from India, a case of gastroenteritis due to S. enterica serovar Thompson.

Elizabethkingia miricola: A rare non-fermenter causing urinary tract infection

Elizabethkingia miricola (E. miricola) is a gram-negative non-fermentative bacterium which is rarely encountered. It is usually misidentified or considered as a contaminant in routine microbiology laboratories due to the limitations in conventional biochemical techniques. However, with the advent of the matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS), the identification of non-fermenters has become easy and this has led to enhanced understanding of the clinical significance of these uncommonly isolated microorganisms. The genus Elizabethkingia has only two species E. meningoseptica and E. miricola. Both of these organisms are known to be multi-drug resistant and therefore, their accurate identification and antimicrobial susceptibility testing are necessary prior to the initiation of appropriate therapy. In the world literature till date, only 3 cases of sepsis caused by E. miricola have been reported. We present the first case of E. miricola association with urinary tract infection.

The 2002 Chandigarh cholera outbreak revisited: utility of MALDI-TOF as a molecular epidemiology tool.

In July 2002, an outbreak of cholera occurred in north India with two separate geographical foci. Pulsed field gel electrophoresis (PFGE) was previously used in typing a representative sample of these isolates. This study evaluates the usefulness of MALDI‐TOF as an epidemiological tool for typing Vibrio cholerae isolates in comparison with PFGE and Amplified fragment length polymorphisms (AFLP). Forty‐six isolates of V. cholerae isolated from stool of patients affected in the July 2002 outbreak were typed using MALDI‐TOF. To validate its utility, clinical and environmental isolates previously characterized by PFGE and AFLP were included for dendrogram analysis. All 46 isolates were correctly identified by MALDI‐TOF to species level. Two distinct clades appeared on dendrogram using MALDI‐TOF corresponding to the two geographical foci of the outbreak. For the study of evolution of organisms from environment, AFLP was superior as it clearly demarcated clinical and environmental isolates. The outbreak was not due to a single clone but due to multiple clones circulating simultaneously, as was seen with PFGE also.

Hospital acquired urinary tract infection by multidrug-resistant Brevundimonas vesicularis

Infections caused by Brevundimonas vesicularis, a nonfermenting Gram-negative bacterium, are very rare. Here, we report the first case of multidrug-resistant hospital acquired urinary tract infection by B. vesicularis. Patient was successfully treated with antimicrobial therapy with piperacillin-tazobactam and amikacin.

Heterophile antibody positive infectious mononucleosis

Objective: The present study has been carried out to analyse the trend of heterophile antibody positive infectious mononucleosis cases.Methods: A total of 1741 cases of clinically suspected infectious mononucleosis from various age groups were investigated during the period January, 1986 to December, 2000 and were analysed for infectious mononucleosis (IM) specific heterophile antibody by Paul-Bunnel-Davidsohn (PBD) test. Forty seven heterophile antibody negative samples were also tested simultaneously for the presence of the IgG antibody to viral capsid antigen (VCA) and Epstein Barr nuclear antigen (EBNA) to detect the exposure to Epstein Barr Virus (EBV) infection.Results : The overall percentage of EBV specific heterophile (Paul-Bunnel) antibody positivity was found to be 11.1 % (194/1741). The average Paul-Bunnel antibody positivity between 1986 to 1990 was 20.5% which declined drastically to 5.7% during 1991-2000. Males comprised of 55.2% of the serologically proven IM cases. Of the 47 heterophile antibody negative cases, 38 (80.9%) and 33 (70.2%) were found to be positive for anti-VCA IgG and anti-EBNA IgG antibodies respectively. Paul Bunnel antibody positivity was found to be higher in > 14 year5 age group patients than those below 14 years.Conclusion : These findings suggest that the EBV infection still continues to be endemic in this part of the country, however, a declining trend in IM cases was observed during the last decade.

Fecal carriage of carbapenem-resistant Enterobacteriaceae and risk factor analysis in hospitalised patients: A single centre study from India

Purpose: Carbapenem-resistant Enterobacteriaceae (CRE) have emerged and disseminated widely causing a variety of infections. In India, the carriage of CRE in hospitalised patients has not been well-studied. Therefore, we conducted the present study to observe gut carriage rate of CRE in patients admitted to our tertiary care hospital. Methods: A total of 232 faecal swabs collected from consecutive stool samples from admitted patients were inoculated on ChromID extended spectrum β-lactamase plates and members of Enterobacteriaceae family were subjected to antibiotic susceptibility as per the Clinical Laboratory Standards Institute guidelines. Polymerase chain reaction for blaVIM, blaKPC, blaIMPand blaNDM-1 genes was performed. CRE was identified if the isolates showed resistance to either imipenem or meropenem or showed the presence of resistant genes. Risk factors of patients with or without CRE colonisation were also analysed. Results: A total of 232 faecal swabs yielded 252 Enterobacteriaceae isolates, of which 49 isolates from 42 patients showed the presence of CRE (occurrence 42/232; 18.1%); 27 isolates from 22 patients carried blaNDM-1, whereas 20 isolates from 17 patients possessed blaVIMgene. No isolate was positive for blaKPCand blaIMPgenes. The CRE was common in both intensive care units (38.4%) and wards (46%) which may reflect the excessive use of broad-spectrum antibiotics in both these settings. The CRE was also found to have a significantly higher antimicrobial resistance as compared to non-CRE isolates. The logistic regression analysis of significance showed the presence of any indwelling device (P = 0.049) and nasogastric tube (P = 0.043) as independent risk factors for acquiring gut colonisation. Conclusions: The study is the first from India to show high CRE carriage in patients admitted to a tertiary care centre and emphasises the need of strict antimicrobial stewardship implementation in hospitals to prevent dissemination of multidrug-resistant CRE.

Biofilm formation capability of enterococcal strains causing urinary tract infection vis-a-vis colonisation and correlation with enterococcal surface protein gene

Background: Data regarding differences in biofilm formation among urinary isolates of enterococci causing nosocomial infection versus asymptomatic colonisation is lacking. Conflicting data are available for the role of enterococcal surface protein (esp) gene in the development of enterococcal biofilms. Materials and Methods: A total of 50 (25 each of asymptomatic bacteriuria and urinary tract infection (UTI) isolates were collected from admitted patients who had nosocomial acquisition of enterococci in urine culture (≥105 cfu/ml). Biofilm assay was done by the quantitative adherence assay. Screening for esp gene was carried out by polymerase chain reaction, and confocal laser scanning microscopy was used to examine biofilms. Results: Out of 25 enterococcal isolates from asymptomatic patients, 9 (36%) isolates were found to be biofilm producers (6 weak [optical densities [OD]595 < 0.2] and three medium [OD595≥0.2 to< 0.5]). Twelve (48%) out of 25 enterococcal isolates from UTI cases, produced biofilms (7 weak, 4 medium, and 1 strong [OD595>0.5]). The esp gene was present in 30 (12 biofilm+, 18 biofilm−) isolates. Seventeen esp positive isolates were from asymptomatic cases whereas 13 were from UTI. However, we found that 100% of medium and strong biofilm producers were esp positive (P < 0.001). On comparing Enterococcus faecalis (n = 10) and E. faecium (n = 40) isolates, 70% of E. faecalis isolates were biofilm producers as compared to only 35% of E. faecium isolates (P > 0.05). The esp positivity was observed more in E. faecium isolates (65%) as compared to 40% in E. faecalis. Vancomycin-sensitive enterococcal and vancomycin-resistant enterococcal isolates and catheter-related and unrelated isolates showed similarity in biofilm production and esp positivity. Conclusion: The esp gene is not compulsorily required to produce biofilm but when present may enhance the biofilm formation. We did not find any correlation between biofilm formation and the ability of the strain to cause symptomatic UTI be associated with catheters or vancomycin resistance.