ORIGINAL PAPER Ciprofloxacin-resistant Escherichia coli in hospital wastewater of Bangladesh and prediction of its mechanism of resistance Farhima Akter • M. Ruhul Amin • Khan Tanjid Osman • M. Nural Anwar • M. Manjurul Karim • M. Anwar Hossain Received: 12 February 2011 / Accepted: 27 August 2011 Ó Springer Science+Business Media B.V. 2011 Abstract Hospital and agriculture wastewater is mostly responsible for causing environmental pollution by spreading un-metabolized antibiotics and resistant bacteria, especially in Bangladesh. Here, we studied the influence of the most frequently prescribed antibiotic, fluoroquinolone (*72%), on the development of antibiotic resistance in Escherichia coli. Out of 300, 24 ciprofloxacin resistant E. coli isolates were selected for the study that showed the MBC 100 higher than expected (600 lg/mL). Here, we profiled plasmid, sequenced gyr genes, screened mutations and analyzed the effect of mutation on drug-protein inter- action through molecular docking approach. We found that (1) out of 10, most of them (n = 7) had large plasmid(s); (2) all ciprofloxacin-resistant isolates had gyrA double mutations (S83L and D87Y); (3) no isolate had qnr gene; and (4) docking of ciprofloxacin with DNA gyrase A subunit suggests that acquisition of double mutation leads to alteration of the ciprofloxacin binding pocket. Keywords Hospital wastewater  Antibiotic resistant bacteria  Ciprofloxacin  DNA gyrase A Introduction There has been growing concern about antimicrobial resistance in the environment and formation of biological resistant biofilm and their ecological effects (Kummerer 2001, 2003), especially in rural Bangladesh and other developing countries (Hossain et al. 1998; Sack et al. 1997; Hoge et al. 1998). The hospital wastewater carries both the resistant bacteria (Larson 2007) and un-metabolized anti- biotic. In Bangladesh, the wastewater pollution is more alarming due to direct disposal of hospital and agricultural wastewater to the environment (Al-Ahmad et al. 1999). Currently, the management of bacterial infections has been increasingly complicated due to the emergence of resistance to most first-line antimicrobial agents, including fluoroquinolones, penicillins and cephalosporins (Karlow- sky et al. 2001; Urban et al. 2003; Obritsch et al. 2004; Paterson et al. 2004). It has also become evident that this antibiotic is extensively used and misused in hospitals, communities, as well as in veterinary medicine (Blondeau and Yaschuk 1996; Acar and Goldstein 1997). However, it has been uncovered recently that there are clear correla- tions between fluoroquinolone resistance in Escherichia coli isolates and hospital location, economic status, and culture site (Boyd 2008). Targets of quinolones are DNA gyrase and topoiso- merase IV that are tetrameric A 2 B 2 enzymes encoded by the gyrA and gyrB, and the parC and parE genes, respec- tively. Resistance to fluoroquinolone usually results from chromosomal mutations (Wang et al. 2004). In Gram negative organisms, mutations in chromosomal gyrA were reported to produce low level of resistance, whereas higher MICs are associated with additional mutations, particularly in parC, but also in gyrB and, less commonly, in parE (Woodford and Ellington 2007). gyrA mutations in the Farhima Akter, M. Ruhul Amin and Khan Tanjid Osman contributed equally. Electronic supplementary material The online version of this article (doi:10.1007/s11274-011-0875-3) contains supplementary material, which is available to authorized users. F. Akter  M. R. Amin  M. M. Karim  M. A. Hossain (&) Department of Microbiology, University of Dhaka, Dhaka 1000, Bangladesh e-mail: anwar5533@yahoo.com K. T. Osman  M. N. Anwar Department of Microbiology, University of Chittagong, Chittagong 4331, Bangladesh 123 World J Microbiol Biotechnol DOI 10.1007/s11274-011-0875-3