Abstract
Spread of genetically diverse Staphylococcus aureus characterized with multi-antibiotic resistance and regulated by high level agr functionalities in several communities in southwest Nigeria was investigated and evaluated for infection control. Staphylococcus aureus pathotypes recovered from 256 cases including purulent pus from skin infections, soft tissue aspirates, wounds, otorrhea, eye, throat and endocervical infections were assayed for biofilm and antibiogram. Further genotyped with micro-array, mapped for geospatial distribution and evaluated for clonal diversity and functional accessory gene regulators (agr). Significant Staphylococci infection among the ages (OR:0.021, CI:0.545–1.914) and female gender with prevalence rate of MSSA (53.0%) and MRSA (1.5%) (OR:1.021, CI:0.374–1.785) were observed. More than 52.5% resistance rates to tetracycline and amoxicillin with significant median resistance were observed in all the infection cases (p = 0.001). Resistance rate of 78.8% at MIC50 32μg/ml and MIC90 128μg/ml to amoxicillin-clavulanate, and more than 40% resistance to ceftazidime, ciprofloxacin and tetracycline of MIC90 and MIC50 at 32 μg/ml were observed. Strains with multi-antibiotic resistance index above 0.83, high beta-lactamase and strong biofilm clustered into separate phylo-group. Heterogeneous t442 (wound and pus), t657 (wound), t091 (ear) and t657 (ear and wound) revealed high phylogenetic diversity. Only 4.6% pvl+ MSSA-CC1 agrI, pvl+ MSSA-CC5 (13.6%) and pvl+ MRSA-CC7 agrII (4.6%), expressed enterotoxin, leukocidins, proteases and resistance gene determinants. Livestock clonal types clustered with identified community-associated strains. Clonal dissemination of resistant pvl+ MSSA-CC1 and MRSA-CC5 encoding agr were predominant in several peri-urban communities where adequate geno-surveillance, population-target antimicrobial stewardship, extensive community structured infection control programs are needed to prevent further focal dissemination.
Highlights
Staphylococcal infection remains a major health challenge in several countries, with huge resultant adverse effect ranging to life-threatening diseases such as pneumonia, bacteremia to high mortality cases [1]
We investigated the antibiotic resistance distribution and prevalence of agr groups of phylo-diverse S. aureus strains characterized by various spa repeats and assessed the potential association between different agr group functionalities, clonal diversity and staphylococci infection controls
Beta-lactamase production was assayed with modified starch-acidometric method [16] and Minimum inhibitory concentrations (MICs) for each antibiotic class against the strain was determined using micro-broth dilution assay [17] with 12 panel antibiotics consisting of tetracycline (TE), ceftazidime (CAZ), ciprofloxacin (CIP), gentamycin (GEN), amoxycillin-clavulanic acid (AMC), cefuroxime (CRO), ofloxacin (OFX), sulfamethoxazole (SXT), erythromycin (E), fosfomycin (FOX), vancomycin (VA) and Linezolid (LZD)
Summary
Staphylococcal infection remains a major health challenge in several countries, with huge resultant adverse effect ranging to life-threatening diseases such as pneumonia, bacteremia to high mortality cases [1]. Functional agr groups were reported to enhance persistent staphylococci bacteraemia and soft tissue tropism with low antibiotic susceptibility to penicillin, cephalosporin and vancomycin [7,8]. Similar clonal spread of MRSA (methicillin-resistant Staphylococcus aureus) and MSSA (methicillin-susceptible Staphylococcus aureus) is becoming pandemic in several communities in Africa, mostly Nigeria where animal husbandry, behavioural responses and declined demographic factors enhance continuous dissemination of staphylococcal infection with high degree of antibiotic resistance [9]. The misuse and unregulated prescription of penicillin derivatives in high and uncontrollable proportion for treating several extra-intestinal infections such as abscess, ear infections, subcutaneous tissue inflammation, nasal discharges in children and post-surgical wound culminated in a high rate of resistance and continuous development of methicillin-resistance strains [10,11]
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