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Year : 2014  |  Volume : 32  |  Issue : 2  |  Page : 172--174

Incidence of extended spectrum beta lactamase producing Escherichia coli among patients, healthy individuals and in the environment

EA George, S Sankar, MV Jesudasan, C Sudandiradoss, B Nandagopal 
 Sri Sakthi Amma Institute of Biomedical Research, Sri Narayani Hospital and Research Centre, Sripuram, School of Bio Sciences and Technology, VIT University, Vellore, Tamil Nadu, India

Correspondence Address:
B Nandagopal
Sri Sakthi Amma Institute of Biomedical Research, Sri Narayani Hospital and Research Centre, Sripuram, School of Bio Sciences and Technology, VIT University, Vellore, Tamil Nadu
India

Abstract

We investigated the faecal carriage of extended spectrum β-lactamases (ESBL) producing Escherichia coli in different groups of human subjects and in the environment. A total of 363 E. coli strains were isolated from stool samples of patients (n = 77), healthy subjects (n = 170) and from different environmental samples (n = 116). A total of 124 ESBL producing E. coli strains were isolated in this study. The frequency of ESBL producing E. coli was found to be highest (60.3%) among the strains isolated from patients, followed by healthy individuals (38%) and the environment (10.5%). The environment was observed to have a very low number of ESBL producing E. coli.

How to cite this article:
George E A, Sankar S, Jesudasan M V, Sudandiradoss C, Nandagopal B. Incidence of extended spectrum beta lactamase producing Escherichia coli among patients, healthy individuals and in the environment.Indian J Med Microbiol 2014;32:172-174

How to cite this URL:
George E A, Sankar S, Jesudasan M V, Sudandiradoss C, Nandagopal B. Incidence of extended spectrum beta lactamase producing Escherichia coli among patients, healthy individuals and in the environment. Indian J Med Microbiol [serial online] 2014 [cited 2020 Oct 22 ];32:172-174
Available from: https://www.ijmm.org/text.asp?2014/32/2/172/129810

Full Text

 Introduction



Relentless use of β-lactam antibiotics in the clinical practice has resulted in the appearance of newer β-lactamases such as extended spectrum β-lactamases (ESBLs), are typically plasmid mediated and seen mainly in Escherichia coli and Klebsiella pneumoniae. Among the many ESBL enzymes characterised, temoneira (TEM), sulfhydryl variable (SHV) and CTX-M are the commonly reported ones. [1] CTX-M type ESBL is emerging rapidly in many parts of the globe. The CTX-M enzyme coding plasmids spread and the strains cause outbreaks both in hospitals and in the community. [2],[3] Our study was undertaken to analyse the frequency of faecal carriage of ESBL producing E. coli in patients and among healthy individuals and in the environment.

 Materials and Methods



The study was carried out between July 2011 and September 2012. Faecal samples were collected from patients admitted in wards and high dependency units (HDUs) of our study hospital with a minimum stay of 4 days and on antibiotic treatment. Faecal samples were collected from healthy adults and infants (age 0-2) with no history of major infective illness and no antibiotic usage in the recent past (3 months). Environmental sampling such as sewage water from various sewage drains, swabs from public toilets, market places and slaughter houses and fish shops in Vellore were included. The hospital environment was studied by collecting swab samples from wards, procedure rooms and intensive care units of the study hospital. Samples from the hospital sewage were also included in the study. The faecal samples were processed and identified by standard methods. [4]

All the E. coli isolates were screened for ESBL production using double disk method according to Clinical Laboratory Standard Institute (CLSI) guidelines [5] where the antibiotic disks of ceftazidime and ceftazidime-clavulanic acid and cefotaxime and cefotaxime-clavulanic acid were used. A difference of ≥5 mm in the zone diameter of the antibiotic and antibiotic-inhibitor combination indicated positive for the production of ESBL. E. coli ATCC 25922 and K. pneumoniae ATCC 700603 were used as positive and negative controls respectively for the test.

E. coli strains testing positive for the production of ESBL were analysed for their antibiograms with respect to cephalosporins and other classes of antimicrobials as per CLSI guidelines. Chi-square (χ2 ) test was used, a P ≤ 0.05 was considered to be statistically significant (Epi Info is statistical program available for download online and is distributed by CDC and Prevention, Atlanta).

 Results



A total of 363 samples, faces (n = 247) and environmental (n = 116) were collected. E. coli strains (n = 361) obtained from the different study groups covering humans and environment were analysed for the presence of ESBL production. A total of 124 ESBL producing E. coli were recovered. Of the groups studied, the frequency of ESBL producing E. coli was found to be 60.3% among the patients, 38% among the healthy individuals and 10.5% among the strains from the environment [Table 1].{Table 1}

The incidence of ESBL producing E. coli among the patients was found to be significantly (P < 0.0001) higher than the healthy subjects. Among the healthy individuals, 46.1% strains from adults and 25% strains from infants were ESBL producers (P = 0.001). The overall frequency of occurrence of ESBL producing E. coli was significantly (P < 0.001) higher in the human subjects (43.9%) when compared to that of the environment (10.5%). The difference in the incidence of ESBL producing E. coli isolated from the hospital environment to that of the other environmental samples however was not statistically significant (P = 0.092).

The in-patient sampling included faecal samples mostly from the wards (n = 64) and from the Neurology HDU (n = 13). From the wards, 83 isolates were recovered, of which ESBL E. coli was found to be 60.7%. From the neuro-HDU, 15 isolates were obtained; the frequency of ESBL E. coli was 58.3%. The overall resistant rate among the patient group from the wards and the neuro-HDU was 63%. The number of ESBL positives was 43.8% in non-catheterised patients and 16.6% in catheterised patients. The difference among the patients with and without a history of previous hospitalisation was found to be statistically insignificant (χ2 = 1.89; P = 0.17). The data on catheterization, length of hospital stay and previous hospitalisation was not available for eight patients. Out of the 41 ESBL producing E. coli reported from the patients group, only one strain, isolated from a patient with septic arthritis was resistant to meropenem and imipenem.

The ESBL producing E. coli isolates were resistant to ampicillin and all cephalosporins tested except cefotetan [Figure 1]. The strains recovered from the environment showed very little or no resistance to antimicrobials other than cephalosporins. All the strains showed susceptibility to imipenem, meropenem, tigecycline, amikacin and piperacillin-tazobactam. Only one strain was found to be resistant to imipenem and meropenem. The strains from healthy infants showed more resistance than the strains from the healthy adults.{Figure 1}

 Discussion



In India, there have been several reports on the prevalence of ESBLs in recent years. [6],[7],[8],[9] In our study, of the 363 E. coli isolated from different human and environmental sources, 122 were found to produce ESBL. The usage of antimicrobials is one of the major risk factors for colonisation with ESBL producing Enterobacteriaceae.[10]

The carrier rate was found to be 25% and 48% among the infants and healthy adults respectively. Several findings suggest that the acquisition of ESBL harbouring isolates may be mediated by contaminated food and water. [11],[12] Environment showed a very low rate (10.5%) of ESBL E. coli. A high rate of dissemination of E. coli in the environment, but not the ESBL E. coli indicates a loss of resistance (by losing their plasmids) in the environment. As suggested in a report, [13] for the resistance to succeed, it needs to have a mechanism that imposes fitness burden, along with biologically 'fit' host strain or strains. Therefore, our findings show the environment to be a low risk factor in the acquisition and transmission of ESBL E. coli.

ESBL producing strains revealed complete resistance to ampicillin and all cephalosporins used except cefotetan. The strains isolated from the patients showed an increase in resistance rate to other non-β-lactam classes of antibiotics. This could be due to the load of antibiotic pressure in the hospital. When compared with patients, strains from the healthy individuals showed moderate resistance to other classes of antibiotics whereas those from the environment showed very little or no resistance. Carbapenems still stand as the drug of choice for infections caused by ESBL E. coli. Tigecycline showed complete action against ESBL E. coli followed by amikacin and piperacillin-tazobactam, only cefotetan showed action against ESBL E. coli.

 Conclusion



study shows high rate of faecal carriage of ESBL producing E. coli in patients. The environment was a poor reservoir of ESBL. Our study reinforces the importance of continued surveillance and monitoring of antimicrobial resistance to combat the growing infections caused by ESBL E. coli.

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