A total of 46 individual colonies were isolated from four water sample-cultures, where 10 (21.7%) isolates showed MIC >4 for CIP (data not shown). These bacteria were isolated from water collected from location no. 3 and 4 (figure 1). There were three
and one unknow-nisolate (table II).
strains were encoded with multiple resistant de-terminants including complex of
. Among the resistant determinant,
were not observed in any isolates in environmental water samples from Bangladesh. DNA sequences of
were compared with the associated sequences in GenBank. (Accession numbers AF052254 and AF052258 respectively).
In this study, the isolation of quinolone resistant bacteria from two out of four environmental water samples collected from a lake in Dhaka. Ten quinolone resistant gene encoding strains were isolated, where one strain was not identified by BD Phoenix-100 system and others included three P. putida
, two E. coli
, two K. pneumoniae
, two P. aeruginosa
. The current study is the first evidence for the existence of quinolone resistant P. putida, K. pneumoniae
and P. aeruginosa
in environmental water in Bangladesh. A previous study reported CIP-resistant E. coli
in hospital waste water in Bangladesh26
, and also did not find qnr gene in their E. coli
isolates, similar to the current study result. But they showed co-existence of both gyrA
in isolates and we found only gyrA
resistant gene in our E. coli
isolates. However, taking together it could be concluded that in disseminating E. coli
in Bangladesh water quinolone resistance is mainly determined by mutation of DNA gyrase that exhibit high-level of resistance to quinolone group of drugs. Another recent study showed increased rate of CIP resistance in common clinical isolates like E. coli, P. aeruginosa, K. pneumonia
, etc. in Bangladesh.27
In this study, it was to befound that high-level of resistance determining gene gyrA
in those clinically relevant bacteria in environment indicating important influence of environmental bacteria in harvesting and spreading of resistant genes among clinical isolates.
It is a long running debate in epidemiology field whether environmental organisms significantly influence clinical infection or not. However, with the current expanded understanding it is now clear that dissemination of resistant organisms and/or their resistant determinants from humans to animals and vice versa, often involve environmental pathways including foodstuffs, animal wastes and water sources. Thus, the environment plays an important role in both the emergence and spread of microbial resistance.28
Zurfluh K et al showed drug resistant isolates from river water in Switzerland were comparable with those isolates from clinics, healthy human carriers and food-producing animals.29
It could be applicable in other parts of the world, including Bangladesh. We observed DNA gyrase targeted resistance in 50% of isolates, warned a careful observation of this mutation in clinical isolates. Plasmid-mediated quinolone resistance (PMQR) was ob-served in eight environmental isolates in Bangla-desh. Although PMQR mechanisms confer low level resistance to quinolones,2, 8-16
but they are thought to enable the occurrence of chromosomal mutation in bacteria which then lead to increased resistance levels, as high as up-to 250-fold.2, 12, 14
Unlike target-mediated resistance, which is transmitted vertically from generation to generation, PMQR can be transmitted horizontally (through bacterial conjugation) as well as vertically. Moreover, plasmids that confer quinolone resistance typically carry additional genes that cause resistance to other antimicrobials.9, 11, 12, 14
Quinolone resistant E.coli
(TUM 12598 and TUM 12599) and K. pneumonia
(TUM 13741) are also included as ESBL-producing bacteria according to our previous study.30
Our finding is comparable with the study of Zurfluhet al. where they showed that ESBL producing E. coli
in their collected environmental water samples were carrying resistant determinants against quinolones. Concomitant quinolone and other class of drugs resistant bacteria are not uncommon in clinical setting in Bangladesh, as Rahman M et al. reported 46.3% MDR-Salmonella typhi
were less susceptible to CIP.32
This study provides evidence for the importance of the water-related environment as a reservoir of emerging threat of quinolone resistance and raises worrisome of increasing prevalence of quinolone resistant organisms in clinics in Bangladesh. More attention and investigations in environmental and clinical settings are required to challenge the threat by quinolone resistant bacteria.
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