RESUMEN
Among resistant nosocomial and community pathogens, MRSA has become the most serious pathogen, causing life threatening infections worldwide. In S.aureus, quick and exact recognition of methicillin (cefoxitin) resistance has become essential. The benchmark for MRSA identification among S.aureus is the detection of the mecA gene that causes the expression of protein (PBP2a) culpable for classic ß-lactam resistance. However, the utter reliance on amplification of mecA gene as a hallmark in confirmation of methicillin (cefoxitin) resistant S. aureus is the matter of distrust by some investigators. The current investigation designed to analyse the prevalence of mecA gene among phenotypically positive MRSA isolates using molecular method and to correlate its prevalence to conventional techniques. Furthermore, antimicrobial sensitivity of mecA positive staphylococci was determined by Kirby Baeuer method. For this purpose, 201 clinical staphylococcal specimens were recovered from various diagnostic laboratories in Karachi City, Pakistan. Phenotypic existence of methicillin resistance in S. aureus was observed to be 51.7%. In contrast, when organisms were subjected for amplification of mecA gene by PCR, mecA positive isolates were 36/104 (35%) MRSA isolates. Current work raise question towards the usefulness of molecular identification of mecA gene in confirmation of methicillin resistance without correlating with conventional methods. Therefore, it is essential to consider the other possible resistance mechanisms for ß-lactams that may interact with mecA gene in the development of methicillin resistance mechanism in Staphylococcus.
Asunto(s)
Proteínas Bacterianas/aislamiento & purificación , Infecciones Comunitarias Adquiridas/epidemiología , Pruebas Genéticas/métodos , Genotipo , Staphylococcus aureus Resistente a Meticilina/aislamiento & purificación , Proteínas de Unión a las Penicilinas/aislamiento & purificación , Infecciones Estafilocócicas/epidemiología , Proteínas Bacterianas/genética , Infecciones Comunitarias Adquiridas/diagnóstico , Infecciones Comunitarias Adquiridas/genética , Humanos , Staphylococcus aureus Resistente a Meticilina/genética , Pakistán/epidemiología , Proteínas de Unión a las Penicilinas/genética , Prevalencia , Infecciones Estafilocócicas/diagnóstico , Infecciones Estafilocócicas/genéticaRESUMEN
This assessment aims to determine the prevalence of methicillin resistance and multidrug resistance (MDR) among the clinical isolates of Staphylococcus aureus and antimicrobial susceptibility profile of methicillin resistant Staphylococcus aureus (MRSA) to the frequently prescribed antibiotics in Karachi. Isolates of MRSA, recovered from various clinical samples were included in this prospective, cross-sectional study from Jan 2015 to June 2017. Agar diffusion method was employed according to the protocols of Clinical Laboratory Standards Institute. Out of total 346 S. aureus strains, the frequency rate of MRSA was 52% (n = 180). MRSA infection was found higher among the age group 21-30 years i.e. 30% (n=54), followed by 20% (n=36) in 31-40 years. Frequency of MRSA percentage in male and female was and 70% and 30% respectively. MRSA was more frequently observed in blood 20% (n=36). MRSA showed high resistance (100%) to Oxacillin and Cefoxitin while 25% Vancomycin resistant S. aureus (VRSA) isolates and 25% Teicoplanin resistance were also reported. MRSA exhibited 16% resistance to Minocycline. It was concluded that MRSA pose a challenging threat to public health in Karachi. In addition, MDR should be periodically checked to avoid treatment failure.