Abstract
The occurrence and genetic relatedness of AmpC beta-lactamase producing Enterobacteriaceae isolated from clinical environments, groundwater, beef, human and cattle faeces were investigated. One hundred seventy-seven (177) samples were collected and cultured on MacConkey agar. A total of 203 non-repetitive isolates were characterised using genus/species-specific PCRs and the identified isolates were subjected to antibiotic susceptibility testing. The production of AmpC beta-lactamases was evaluated using cefoxitin disc, confirmed by the D96C detection test and their encoding genes detected by PCR. The D64C extended-spectrum beta-lactamases (ESBL) test was also performed to appraise ESBLs/AmpC co-production. The genetic fingerprints of AmpC beta-lactamase producers were determined by ERIC-PCR. A total of 116 isolates were identified as E. coli (n = 65), Shigella spp. (n = 36) and Klebsiella pneumoniae (n = 15). Ciprofloxacin resistance (44.4–55.4%) was the most frequent and resistance against the Cephem antibiotics ranged from 15–43.1% for E. coli, 25–36.1% for Shigella spp., and 20–40% for K. pneumoniae. On the other hand, these bacteria strains were most sensitive to Amikacin (0%), Meropenem (2.8%) and Piperacillin-Tazobactam (6.7%) respectively. Nineteen (16.4%) isolates comprising 16 E. coli and 3 Shigella spp. were confirmed as AmpC beta-lactamase producers. However, only E. coli isolates possessed the corresponding resistance determinants: blaACC (73.7%, n = 14), blaCIT (26%, n = 5), blaDHA (11%, n = 2) and blaFOX (16%, n = 3). Thirty-four (27.3%) Enterobacteriaceae strains were confirmed as ESBL producers and a large proportion (79.4%, n = 27) harboured the blaTEM gene, however, only two were ESBLs/AmpC co-producers. Genetic fingerprinting of the AmpC beta-lactamase-producing E. coli isolates revealed low similarity between isolates. In conclusion, the findings indicate the presence of AmpC beta-lactamase-producing Enterobacteriaceae from cattle, beef products and hospital environments that commonly harbour the associated resistance determinants especially the blaACC gene, nonetheless, there is limited possible cross-contamination between these environments.
Highlights
The family Enterobacteriaceae consists of bacterial species frequently isolated from clinical specimens and most often incriminated in a variety of infections [1, 2]
PCR identification of 203 presumptive Enterobacteriaceae isolates resulted to a higher detection frequency for E. coli (32.0% n = 65), followed by Shigella species (26.1%, n = 36) and Klebsiella pneumoniae 15 (17.7%)
The increased public health threat posed by multidrug-resistant extended-spectrum beta-lactamases (ESBL) and AmpC beta-lactamase-producing strains especially among pathogenic Enterobacteriaceae is a cause for concern
Summary
The family Enterobacteriaceae consists of bacterial species frequently isolated from clinical specimens and most often incriminated in a variety of infections [1, 2]. Four Shigella spp., S. flexneri; S. dysenteriae; S. boydii and S. sonnie have been described and are thought to have evolved from ancestral non-pathogenic E. coli by the acquisition of a large virulence plasmid [6], that encodes many virulence factors on its ipa-mxi-spa region of which the invasion plasmid antigen (antigens (IpaA, IpaB, IpaC and IpaD proteins) is one of the most essential. These proteins are important for bacterial invasion of epithelial cells as well as immune cell escape [7]. K. pneumoniae on the other hand occurs as an opportunistic pathogen especially in persons with weakened immune systems and cause soft tissue (e.g. cellulitis and necrotizing fasciitis), to life-threatening infections such as pneumonia, septicemia, meningitis, and endophthalmitis as well as are implicated in a significant number of cases of hospital-acquired urinary tract infections [9]
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