Untreated wastewater is a risk factor for the spread of antibiotic resistance in the environment. However, little is known about the contribution of untreated wastewater to the burden of antibiotic resistance in the Nigerian environment. In this study, a total of 143 ceftazidime-/cefpodoxime-resistant bacteria isolated from untreated wastewater and untreated wastewater-contaminated surface and groundwater in Nigeria were screened for extended-spectrum β-lactamase (ESBL) genes, integrons and integron gene cassettes by PCR. The genetic environment of bla was mapped by PCR and potentially conjugative plasmids were detected among the isolates by degenerate primer MOB typing (DPMT). ESBL production was confirmed in 114 (79.7%) isolates and ESBL genes (bla, bla and bla) were detected in 85 (74.6%) ESBL-producing isolates. bla was associated with ISEcp1 and with orf477 in 12 isolates and with ISEcp1, IS26 and orf477 in six others. To the best of our knowledge, this is the first report of bla in hand-dug wells and borehole serving as sources of drinking water and a first report of the genetic environment of bla in environmental bacteria from Nigeria. The results of this study confirm untreated wastewater as an important medium for the spread of ESBL-producing bacteria within the Nigerian environment. Hence, the widespread practice of discharging untreated wastewater into the aquatic ecosystem in Nigeria is a serious risk to public health.
Emergence of bla CTX-M-15, qnrB1 and aac(69)-Ib-cr resistance genes in Pantoea agglomerans and Enterobacter cloacae from Nigeria (sub-Saharan Africa)Resistance of Enterobacter species to extended-spectrum cephalosporins is known to be mediated by hyperproduction of chromosomal AmpC b-lactamases. However, the additional expression of plasmid-encoded extended-spectrum b-lactamases (ESBLs) has become more prevalent worldwide in recent years (Ko et al., 2008). In Nigeria, ESBL production in Enterobacter species has been associated with TEM-and SHV-type ESBLs (Aibinu et al., 2003;Kasap et al., 2010). Other b-lactamase resistance determinants, conferring resistance to extendedspectrum cephalosporins, such as bla VEB , bla OXA and bla CMY , have recently been reported in Nigerian Providencia species strains (Aibinu et al., 2011). In addition, the worldwide spread of CTX-M-15 (Cantó n & Coque, 2006) has reached Nigeria, having being identified in Klebsiella species and Escherichia coli (Soge et al., 2006;Olowe et al., 2010). There is no documented report yet on ESBL production mediated by bla or the association of the spread of PMQR determinants in Enterobacter species from Nigeria. This study reports the phenotypic and genotypic characteristics of ten clinical isolates of Enterobacter species and one isolate of Pantoea agglomerans with respect to the occurrence of bla CTX-M and other resistance genes. The Enterobacter species, which consisted of Enterobacter asburiae (n51), Enterobacter aerogenes (n51) and Enterobacter cloacae (n58), and the Pantoea agglomerans isolate represented 9.5 % of all members of the Enterobacteriaceae isolated within a period of 6 months from October 2008 to March 2009 at Lagos University Teaching Hospital (LUTH), a tertiary hospital, in Nigeria. Enterobacter agglomerans was previously renamed Pantoea agglomerans to reflect its genetic distance from the genus Enterobacter (Sanders & Sanders, 1997).Bacterial species identification was performed using the VITEK 2 system (VITEK2 GN-card; bioMérieux). Antimicrobial susceptibility testing was determined according to the guidelines of the Clinical and Laboratory Standards Institute (CLSI, 2010) by the broth microdilution method and VITEK2 AST-N13 card. The quality control strain used was E. coli ATCC 25922 (Oxoid). Etest strips containing cefotaxime in combination with clavulanic acid, and the double disc synergy tests (ESBL/AmpC ID D68C; Mast Group), were used for phenotypic detection and differentiation of both ESBL and AmpC production. Broth mate conjugation assays were performed as described by Pfeifer et al. Phenotypic analysis of the 11 isolates in this study revealed that two of the isolates (Enterobacter cloacae 213K and P. agglomerans 69K) were ESBL-producers. The ESBL gene bla CTX-M-15 was identified in both isolates. P. agglomerans 69K was isolated from the blood culture of an adult male patient admitted for sepsis and diagnosed HIV type-1-positive on admission. The patient was treated empirically with ceftriaxone and was referred to a...
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