Screening for Panton-Valentine Leukocidin Toxin Genes in Multi-Drug Resistant Methicillin-Resistant <i>Staphylococcus aureus</i>Nasal Isolates from Healthy School Children in Mariental, Namibia

Panton-Valentine leukocidin (PVL) is one of the toxins responsible for increased virulence of Staphylococcus aureus. In school settings where children are in close contact with each other, S. aureus strains, including those that may produce PVL, can be transmitted and spread in the community. Twenty-two multi-drug resistant MRSA nasal isolates from children enrolled in five schools in the town of Mariental and the multi-drug resistant American Type Culture Collection MRSA reference strain S. aureus ATCC 33591 (PVL-negative control) were used for molecular assays. Plasmid deoxyribonucleic acid (DNA) of isolates was amplified by polymerase chain reaction (PCR) and amplified PCR products were electrophoresed on a 2.5% (w/v) agarose gel containing 12 μl 0.5 μg/ml ethidium bromide and 1× TAE (Tris-acetate-EDTA) buffer at 90 volts for 50 minutes. The developed gel was viewed for the PVL-associated lukS and lukF genes that amplified at 151 bp and 406 bp, respectively. Our results indicated that seven nasal isolates had PVL toxin gene(s). From the seven isolates, three were tested positive for both lukS and lukFgenes, one tested positive for only lukS, and three tested positive for only lukF. Two of the isolates harbouring both lukS and lukF genes shared the same antibiotic resistance pattern and one of them could also produce enterotoxin A. One of the isolates with only lukF gene could produce enterotoxins B and C. These toxin-producing isolates can be expected to be more virulent than non-producers. Children should be educated on the importance of regular handwashing with soap and water to prevent the spread of potentially virulent staphylococci amongst them and the wider community. This work warrants a larger study to be carried out to investigate PVL toxin and its associated infections in Staphylococcus from school children in Namibia.

Antibiotic Resistance Trends of Nasal Staphylococcal Isolates from Namibian School Children

Nasal colonization with Staphylococcus strains puts children at risk of developing difficult-to-treat staphylococcal infections. Antibiotic resistance data is limited in Namibia. Our study thus aimed to provide resistance trends for nasal staphylococci isolated from school children in the Mariental District. This is the first report on antibiotic resistance trends of staphylococci from Namibian school children. By Kirby-Bauer disk diffusion assay, 352 Staphylococcus aureus and 81 coagulase-negative staphylococci (CoNS) isolates from Namibian school children aged 6 - 14 years underwent susceptibility testing against seven antibiotics. Ninety-six percent S. aureus and 66.7% CoNS were resistant to ampicillin. Ampicillin resistance was significantly higher in S. aureus than in CoNS (P S. aureus. Ciprofloxacin was also the most effective drug against CoNS. Cefoxitin/methicillin resistance was seen in 14.5% S. aureus isolates and 8.6% of CoNS. Thirty-one antibiotic resistance patterns were observed, most frequently ampicillin (A), ampicillin-erythromycin (AP-E), and ampicillin-tetracycline (AP-T). Altogether 12.5% isolates (50 S. aureus and four CoNS) were multi-drug resistant. From the methicillin-resistant S. aureus (MRSA) isolates, 43.1% were multi-drug resistant. Methicillin-resistant CoNS were not multi-drug resistant, with the most common resistance pattern being ampicillin-rifampicin-cefoxitin (AP-RP-FOX). In conclusion, multi-drug resistance in our study was relatively low. However, some of the MRSA isolates were multi-drug resistant, which is of concern. Learners should be educated on the importance of handwashing and appropriate use of antibiotics to prevent spread of antibiotic-resistant bacteria within the community. Ciprofloxacin and gentamicin may effectively be used to treat staphylococcal infections in this study population.