Abstract
Enteric fever is a systemic disease classified into typhoid and paratyphoid fever. Fluoroquinolones and third generation cephalosporins are usually the drugs of choice in the management of Salmonella infections. Previous reports have indicated common occurrence of multi-drug resistance (MDR) including resistance to β-lactams and fluoroquinolones. However, there is paucity of information on the genetic determinants of resistance to β-lactam and fluoroquinolones from S. enterica in Southeast Nigeria. Salmonella enterica serovars were identified and screened (25 each from unrelated patients from the four hospitals). Resistant isolates were screened for ESBL phenotypically. Genomic and plasmid DNA were extracted by boiling and alkaline lysis, respectively. PCR amplification of blaTEM, blaSHV and blaCTX-M, among the ESBL positive isolates and sequencing of the Quinolone Resistance Determining Regions (QRDR) on fluoroquinolone resistant isolates were determined. Of the 100 isolates, thirty six of the MDR isolates produced ESBL phenotypically, of which 13 were blaCTX-M positive. DNA sequencing revealed single point mutations in gyrA at amino acid positions Asp-87-Gly, Asp-87-Asn and Ser-83-Tyr in 55 (68.8%), and double mutation in parC at positions Asp-87-Gly in 14 (17.5%). Mutations in gyrA, parC genes, and chromosomal blaCTX-M were responsible for the fluoroquinolones and cephalosporins resistance, respectively in some of the Salmonella enterica from Southeast Nigeria. QRDR of the gyrA gene of the isolates sequenced showed reduced susceptibility to some fluoroquinolone. The taxonomic and neighbouring trees of similar species causing infection worldwide were identified, and hence, alleviates the fear of easy spreading of quinolone and cephalosporin resistant isolates. Key words: Quinolone Resistance Determining Regions (QRDR), ESBL, S.enterica, mutation.
Highlights
Enteric fever is a systemic disease classified into typhoid and paratyphoid fever (Elumalai et al, 2014)
It was observed that isolates recovered from a female child of 2 years in the CHOP unit produced the conventional β-lactamase enzyme but was resistant to only 4 (28.6%) antibiotics used in this study, while an isolate recovered in the EPU unit from a female child of 1 year old was resistant to the 4 (28.6%) of the antibiotics used but produced no conventional β-lactamase and harboured no plasmid
Results from University of Nigeria Teaching Hospital (UNTH) Enugu (Table 4) showed that there were no plasmid recovered from the 25 isolates but 20 (80%) of the isolates produced the conventional β-lactamase enzyme
Summary
Enteric fever is a systemic disease classified into typhoid and paratyphoid fever (Elumalai et al, 2014). Typhoid fever being a systemic infection caused by Salmonella enterica serotype Typhi is a highly adapted human specific pathogen which possesses remarkable mechanism for persistence in host as reported by Onyenwe et al (2011). It estimates for approximately 5.4 million cases worldwide per year (Elumalai et al, 2014). As of 2013, the annual mortality rate was reported at 2.8 per 100,000 person in Africa with 2.5 per 100,000 person reported for Nigeria (Health Grove, 2018) These numbers make typhoid fever an infectious disease worth investigating for better treatment plan and management
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