Higher Isolation of NDM-1 Producing Acinetobacter baumannii from the Sewage of the Hospitals in Beijing

Chuanfu Zhang,Yun Shi,Xuelin Liu,Zhenjun Li,Rongzhang Hao,Jiajun Cui,Lihua Qi,Ligui Wang,Hongbin Song,John D Klena,Daizhi An,Yong Wang,Pan Wang,Liuyu Huang,Peng Li,Xiaofeng Hu,Shaofu Qiu,Raymond Schuch

doi:10.1371/journal.pone.0064857

Abstract

Multidrug resistant microbes present in the environment are a potential public health risk. In this study, we investigate the presence of New Delhi metallo-β-lactamase 1 (NDM-1) producing bacteria in the 99 water samples in Beijing City, including river water, treated drinking water, raw water samples from the pools and sewage from 4 comprehensive hospitals. For the bla NDM-1 positive isolate, antimicrobial susceptibility testing was further analyzed, and Pulsed Field Gel Electrophoresis (PFGE) was performed to determine the genetic relationship among the NDM-1 producing isolates from sewage and human, as well as the clinical strains without NDM-1. The results indicate that there was a higher isolation of NDM-1 producing Acinetobacter baumannii from the sewage of the hospitals, while no NDM-1 producing isolates were recovered from samples obtained from the river, drinking, or fishpond water. Surprisingly, these isolates were markedly different from the clinical isolates in drug resistance and pulsed field gel electrophoresis profiles, suggesting different evolutionary relationships. Our results showed that the hospital sewage may be one of the diffusion reservoirs of NDM-1 producing bacteria.

Highlights

The increasing threat of antibiotic resistance in microbes affecting humans has been recognized as a challenge for treatment of clinical infection
Ten isolates containing the blaNDM-1 gene were identified in sewage prior to disinfect from the general hospitals; this included an effluent sample from a hospital after disinfecting by chlorination before discharge and community life sewage (Table 2)
Previous studies indicated that most clinical New Delhi metallo-b-lactamase 1 (NDM-1) producing bacteria were resistant to all antibiotics except colistin and tigecycline [1,3]

Summary

Introduction

The increasing threat of antibiotic resistance in microbes affecting humans has been recognized as a challenge for treatment of clinical infection. The emergence and spread of pathogenic bacteria with broad spectrum antibiotic resistance pose real threats to the public health systems of any country. In 2009, a new metallo-b-lactamase gene (blaNDM-1), encoding the metallo-blactamase protein New Delhi metallo-b-lactamase 1 (NDM-1) with high carbapenemase activity and which can destroy carbapenemtype antibiotics, was first identified from a Swedish patient of Indian origin [1]. Strains of multiple speciesof blaNDM-1 carrying bacteria, including Shigella boydii and Vibrio cholerae, have been identified worldwide [2,3,4]. The genes encoding NDM-1 are known to be carried on a plasmid, and it is suspected horizontal gene transfer (HGT) promotes the exchange of resistance among Gram-negative organisms

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