Molecular characterization of methicillin-resistant Staphylococcus aureus isolates from a hospital in Ghana

Background: Methicillin-resistant  Staphylococcus aureus (MRSA) are a major cause of hospital- and community-acquired infection. They can colonize humans and cause a wide range of infections including pneumonia, endocarditis and bacteraemia. We investigated the molecular mechanism of resistance and virulence of MRSA isolates from a teaching hospital in Ghana.Methodology: A total of 91 S. aureus isolates constituted the initial bacterial sample. Identification of S. aureus was confirmed by the VITEK 2 system. The cefoxitin screen test was used to detect MRSA and antibiotic susceptibility was determined using the VITEK 2 system. The resistance (mecA, blaZ, aac-aph, ermC, and tetK) and virulence (lukS/F-PV, hla, hld and eta) genes were amplified by polymerase chain reaction (PCR) and positive samples subjected to DNA sequencing. Pulsed field gel electrophoresis (PFGE) was used to ascertain the relatedness of the isolates.Results: Fifty-eight of 91 (63.7%) isolates were putatively methicillin resistant by the phenotypic cefoxitin screen test and oxacillin MICs. However, 43 (47%) of the isolates were genotypically confirmed as MRSA based on PCR detection of the mecA gene. Furthermore, 37.9% of isolates displayed resistance to tetracycline, 19% to trimethoprim-sulphamethoxazole, 15.5% to clindamycin, 12.1% to gentamicin, 13.8% to ciprofloxacin and erythromycin, 6.9% to moxifloxacin and 7.0% to rifampicin. None of the isolates was positive for inducible clindamycin resistance. The prevalence of resistance (mecA, blaZ, aac(6’)-aph(2’’), tetK, and ermC) and virulence (hla and lukS/F-PV) genes respectively were 74%, 33%, 22%, 19%, 3%, 5% and 3%, with isolates organized in two highly related clades.Conclusion: Results indicate a fairly high occurrence of MRSA, which can complicate the effective therapy of S. aureus infections, necessitating surveillance and stringent infection control programmes to forestall its spread.Keywords: MRSA, mecA, blaZ, hla, lukS/F-P

Detection of mutations in the gyrA of clinical Salmonella spp.

The high prevalence of resistance to nalidixic acid and reduced susceptibility to ciprofloxacin of Salmonella spp. obtained from stool samples of neonates presenting with acute diarrhea in 2001 at the King Edward VIII hospital in Durban, South Africa, prompted this study to determine if there were any mutations in the QRDR of these isolates and to search for the qnrA gene. All isolates with nalidixic acid MICs > 48 μg/ml had the single mutation D87N, or D87G in the QRDR of the gyrA gene, and only 2 strains had an additional mutation; S83L and S83F respectively. The mutation S83T was present in only one isolate with the nalidixic acid MIC of 10 μg/ml whilst the 6 other strains with nalidixic acid MICs < 10 μg/ml had no changes in the QRDR of the gyrA gene. The qnrA gene was not found. These findings indicate that there are mutations in the gyrA of Salmonella isolates which could contribute to resistance to nalidixic acid with reduced susceptibility to ciprofloxacin and there is the co-expression of quinolone and extended-spectrum ß-lactam resistance among Salmonella spp

Efficacy of phenotypic, PCR and MALDI -ToF identification methods for Campylobacter spp.

This study compared phenotypic and genotypic identification methods of Campylobacter spp. against the polymerase chain reaction (PCR) in terms of sensitivity, specificity, positive-predictive value and negative-predictive value. Thermophilic Campylobacter isolates were identified using conventional biochemical tests, specifically hippurate hydrolysis, matrix assisted laser desorption ionization- time of flight (MALDI-ToF) mass spectrometry and PCR with primers unique to C. jejuni and C. coli. MALDI-ToF was shown to be superior to biochemical tests for identification of C. coli but equivalent to biochemical tests for C. jejuni.The National Research Foundation Thuthuka: Researchers in Training Programme Ref. TTK2007040500009http://www.smltsa.org.zaam2017Physiolog

Resistome of a carbapenemase-producing novel ST232 Klebsiella michiganensis isolate from urban hospital effluent in South Africa

Objectives: Klebsiella michiganensis is an emerging pathogen implicated in nosocomial infections. Here we report on the resistome, virulome and mobilome of a carbapenemase-producing K. michiganensis isolate from urban hospital effluent in Pietermaritzburg, KwaZulu-Natal, South Africa. Klebsiella sp. isolate KP124 was originally isolated from the final effluent of an urban tertiary hospital in Pietermaritzburg, KwaZulu-Natal. Methods: Following phenotypic characterisation and antibiotic susceptibility testing, the genome of carbapenemase-producing isolate KP124 was sequenced using an Illumina MiSeq platform, de novo assembled and analysed using established bioinformatics tools. Results: The draft genome of strain KP124 was 6 544 586 bp in length, comprising 203 contigs >200 bp. Following confirmation of isolate KP124 as K. michiganensis using reference genomes, the blaOXA-181 carbapenemase gene as well as 11 additional genes encoding resistance against β-lactams, aminoglycosides, fluoroquinolones and sulfonamides were detected. Virulence factors enabling iron acquisition and cell adherence, capsule locus type and plasmid replicon types were identified. Conclusion: This study represents the first report of an OXA-181 carbapenemase-producing K. michiganensis isolate from hospital effluent in South Africa. The presence of such a strain in the environment owing to the absence of hospital effluent treatment presents a potential risk to informal communities that may use contaminated surface water domestically

In vitro potentiation of carbapenems with tannic acid against carbapenemase‐producing enterobacteriaceae : exploring natural products as potential carbapenemase inhibitors

AIMS : We hypothesized and confirmed that tannic acid (TA) reverses carbapenem resistance by inhibiting carbapenemases in class A and B carbapenemase‐producing Enterobacteriaceae. METHODS AND RESULTS: Minimum inhibitory concentrations of carbapenems in the presence and absence of TA and other efflux pump inhibitors, TA‐carbapenemases inhibition assays and computational studies showed that TA had the greatest effect on metallo‐β‐lactamases (MBLs) followed by class A serine‐β‐lactamases (SBLs). TA completely reversed the MICs of MBL producers from between 32 and ≥512 mg l−1 to susceptible values (512 mg l−1 to <4 to 16 mg l−1. Tolerable cytotoxic effect was observed for the concentrations tested (8–1024 mg l−1). TA inhibited enzymes with a marked difference of ≈50% inhibition (IC50) for NDM‐1 (270 μmol l−1) and KPC‐2 (15 μmol l−1). CONCLUSION : TA inhibited both MBLs and SBLs by targeting their hydrophobic sites. Moreover, TA had a stronger binding affinity for MBLs than SBLs as the MBLs, specifically VIM‐1 (−43·7220 ± 0·4513 kcal mol−1) and NDM‐1(−44·2329 ± 0·3806 kcal mol−1), interact with a larger number of their catalytic active‐site residues than that of OXA‐48 (−22·5275 ± 0·1300 kcal mol−1) and KPC‐2 (−22·1164 ± 0·0111 kcal mol−1). SIGNIFICANCE AND IMPACT OF THE STUDY : Tannic acid or its analogues could be developed into carbapenemase‐inhibiting adjuvants to restore carbapenem activity in CRE infections, save many lives and reduce healthcare associated costs.College of Health Sciences, University of Kwa‐Zulu Natal, Durban, South Africa and the South African National Research Foundation (NRF).http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1365-26722020-02-01hj2019Medical Microbiolog