Multiple-Antibiotic Resistance and Presence of CTX-M Genes among Enterobacteriaceae Isolates from Different Sources in Iwo, Osun State, Nigeria

Aims: Assessment of the antibiotic resistance pattern and detection of genes responsible for the β-lactam resistance in enterobacteria isolated from different sources was carried out in the course of the study.

Place and Duration of Study: Samples from different sources in Iwo, Osun State, Nigeria including Abattoir and Cow ranch. The study was done August 2015 to May 2016.

Methodology: Isolation was done on nutrient agar, xylose lysine deoxycholate (XLD) and identified using standard procedures. Antibiotic multidisc containing the following ceftazidime (30 µg), cefruroxime (30 µg), gentamicin (10 µg), ciprofloxacin (5 µg), ofloxacin (5 µg), augmentin (30 µg), nitrofurantoin (300 µg), and ampicillin ( ) were used to study the resistance patterns of the bacteria. Polymerase chain reaction (PCR) method was carried out to screen for CTX-M gene in beta-lactam resistant isolates and statistical analyses were carried out using the analysis of variance test (ANOVA) and the PAST (paleontology statistics) software analytical package where applicable.

Results: Fifty-two (52) entrobacteria consisting of nine genera (9) were isolated and identified, Serratia (13), Enterobacter (11), Klebsiella (6), E. coli (5), Proteus (5), Salmonella (3), Shigella (3), Citrobacter (3), and Yersinia (3). The highest resistance observed by the isolates was to ampicillin (80.7%) followed by augmentin (40%) and 33% resistance of the isolates to cefuroxime, while all the isolates were sensitive to ceftazidime, gentamicin, ofloxacin, ciprofloxacin and nitrofurantoin. Nineteen of the isolates were resistant to three or more of the tested antibiotics i.e. multiple resistance while five of the multidrug resistant isolates show the presence of CTX-M β-lactam resistance gene which seems to be responsible for their resistance to the β-lactam antibiotic tested.

Conclusion: There are a number of organisms in the environment that have developed multiple resistances to several antibiotics and in view of this thwart treatment; of major concern are the Enterobacteriaceae family in which new resistance characteristics have been discovered leading to increasing resistance to standard available drug therapies.