Department of Clinical Chemistry

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    Detection of Mupirocin Resistant Gene and its Association with Some Virulence Factors among Staphylococcus aureus Isolates, Khartoum State
    (University of Khartoum, ) Marouf, Luai Osman Ibrahim ; Naser Eldin Bilal
    Background: Pathogenicity of Staphylococcus aureus is due to the toxins, invasiveness and antibiotic resistance. Methicillin resistant Staphylococcus aureus (MRSA) was a major cause of nosocomial and community acquired infections in most countries. Therefore the main objective of this study was to detect the methicillin and mupirocin resistant genes (mecA and mupA) and its association with some virulence factors (Panton-Valentine leukocidin PVL and clumping factor A Clfa) genes among Staphylococcus aureus isolates in Khartoum State. Methods: This cross sectional descriptive analytical study was conducted at the Department of Microbiology, Faculty of Medical Laboratory Sciences, University of Khartoum during the period from 2014 to 2016. Three hundred and nine isolates of Staphylococcus aureus from various clinical specimens obtained from Khartoum Teaching Hospitals (Khartoum, Omdurman and Khartoum North). Identification of the isolates was based on cultural characteristics and reactions in standard biochemical tests. All the isolates were tested for the following antibiotics: oxacillin (1 μg), mupirocin (5 μg), mupirocin (200 μg), vancomycin (30 μg), linezolid (30 μg), penicillin (10 μg), ciprofloxacin (10 μg), gentamicin (10 μg) and chloramphenicol (30 μg) using disk diffusion technique as shown in the Clinical Laboratory Standards Institute (CLSI) guidelines. All isolated strains were tested for the presence of methicillin, mupirocin resistance and virulence factors encoding genes using PCR with specific primers for detection of mecA, mupA, PVL and Clfa genes. Data were analyzed using SPSS (Statistical Package for Social Sciences) software version 20. Proportion was compared using McNemer test and the significance was determined at the ≤ 0.05%. Results: Out of 309 isolates, the highest percentage of resistance 92.9% (n= 287) was found in penicillin, followed by oxacillin 57.9% (n = 179), gentamicin 17.2% (n= 53), ciprofloxacin 16.2% (n= 50), low level mupirocin 9.7% (n= 30), linezolid 7.4% (n= 23), chloramphenicol 2.9% (n= 9), vancomycin 1.6% (n= 5). High level mupirocin was the most effective antibiotic tested, with low resistance rate 1.4% (n= 4). Of the 30 isolates which showed low level mupirocin resistant 83% (n= 25) were also oxacillin resistant. All high level mupirocin resistant isolates 100% (n= 4) were oxacillin resistant. All isolates showed high susceptibility rate to high level mupirocin, chloramphenicol and vancomycin. The presence of mecA gene was confirmed in 177 (98.9%) of oxacillin resistant isolates. In addition, the presence of mupA was confirmed in all low and high level mupirocin resistant isolates 30 (100%). The PVL gene was detected in 187 (60.5%) isolates. The highest frequency of PVL gene in the isolates which were resistant to penicillin 55.66% (n= 172) and oxacillin 34.3% (n= 106) (P> 0.05). The Clfa gene was detected in 180 (58.25%) isolates. The highest frequency of Clfa gene in the isolates which were resistant to penicillin 54.05% (n= 167) and oxacillin 35.28% (n= 109) (P> 0.05). Conclusion: The prevalence of MRSA infections in Khartoum State Teaching Hospitals has become wide spread. Mupirocin resistance in Staphylococcus aureus isolates is still low. Vancomycin and linezolid are the best drugs for treatment of oxacillin and mupirocin resistant Staphylococcus aureus infections as shown in vitro testing. Furthermore, penicillin showed the highest percentage of resistance among MRSA and MSSA strains. The result of this study showed that there was no association between mupirocin resistant gene (mupA) and the virulence factors (PVL,Clfa).