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

Strategies for the Prevention and Containment of Antibiotic Resistance

Antibiotic resistance may emerge by antibiotic selection pressure but is perpetuated by diverse risk factors and maintained within environments as a result of poor infection control. Population-specific drug pharmacokinetics and pharmacodynamics also play a role. The WHO; US; UK and EU have initiated strategies for the containment of resistance; with surveillance and delineation of the cause(s) cited as essential. Surveillance of antibiotic efficacy should be disease-based; establishing sensitivity profiles of common causative organisms to inform the development of or amendment to standard treatment guidelines and essential drugs lists adopted within the national drug policy. The manner of antimicrobial use (overuse; underuse; inadequate dosing) associated with resistance should be established for appropriate intervention in terms of rational drug use; a reduction in use and dosing regimens based on population-specific pharmacokinetics and pharmacodynamics. Risk factors unique to South African communities (poverty; HIV) and hospitals (duration of hospitalisation; location within the hospital; intensive care unit stay; surgery; wounds; previous and current antimicrobial therapy; mechanical ventilation; urinary catherterisation; nasogastric intubation; central venous and peripheral catheters; previous hospitalisation and transfer from another unit or hospital) must be determined and due vigilance exercised in patients exhibiting classical risk factors for the acquisition of or colonisation with resistant pathogens. Hygiene and sanitation (in communities) and infection control (in hospitals) status must be determined and interventions initiated to prevent the spread of resistance. Pharmacokinetics and pharmacodynamics specific to diverse populations must be devised to optimise antimicrobial therapy. South Africa has unique needs in the antimicrobial resistance arena; needs to be addressed in the context of sev ere financial; human resources and technological challenges

Review: Strategies for the Prevention and Containment of Antibiotic Resistance

Antibiotic resistance may emerge by antibiotic selection pressure but is perpetuated by diverse risk factors and maintained within environments as a result of poor infection control. Population-specific drug pharmacokinetics and pharmacodynamics also play a role. The WHO; US; UK and EU have initiated strategies for the containment of resistance; with surveillance and delineation of the cause(s) cited as essential. Surveillance of antibiotic efficacy should be disease-based; establishing sensitivity profiles of common causative organisms to inform the development of or amendment to standard treatment guidelines and essential drugs lists adopted within the national drug policy. The manner of antimicrobial use (overuse; underuse; inadequate dosing) associated with resistance should be established for appropriate intervention in terms of rational drug use; a reduction in use and dosing regimens based on population-specific pharmacokinetics and pharmacodynamics. Risk factors unique to South African communities (poverty; HIV) and hospitals (duration of hospitalisation; location within the hospital; intensive care unit stay; surgery; wounds; previous and current antimicrobial therapy; mechanical ventilation; urinary catherterisation; nasogastric intubation; central venous and peripheral catheters; previous hospitalisation and transfer from another unit or hospital) must be determined and due vigilance exercised in patients exhibiting classical risk factors for the acquisition of or colonisation with resistant pathogens. Hygiene and sanitation (in communities) and infection control (in hospitals) status must be determined and interventions initiated to prevent the spread of resistance. Pharmacokinetics and pharmacodynamics specific to diverse populations must be devised to optimise antimicrobial therapy. South Africa has unique needs in the antimicrobial resistance arena; needs to be addressed in the context of severe financial; human resources and technological challenges