Phenotypic and Genotypic Characterization of Methicillin and Vancomycin-Resistant Staphylococcus aureus isolates From Patients attending Wad Medani Medical Centers

Abstract

Methicillin resistant Staphylococcus aureus (MRSA) is an increasing problem worldwide while in Sudan we still lacking the preliminary data for this pathogen. The objectives of the present study were to provide evidences about the occurrence of MRSA among Sudanese patients as well as to characterize and amplify different genes responsible for this phenomenon. Three hundred and fifty five patients suffering from different clinical diseases (n= 355) were included in this study during the period from October 2010 to May 2011. The distribution of the enrolled patients was as follows: general surgery at Wad Medani Teaching Hospital 129/355(36.3%), Gynaecology and Obstetrics Teaching Hospital 107/355 (30.1%), Institute of Nuclear Medicine, Moleculour Biology and Oncology 48/355 (13.5%), Orthopaedic Surgery Hospital 8/355 (2.3%), Dr. Ahmed Abdella Hamadein Hospital for Dermal Diseases 23/355 (6.5%), Gezira Hospital for Renal Diseases and Surgery, National Centre of Paediatrics Surgery 7/355 (2%), Tahily Speciality Hospital 7/355 (2%), Alyaa Speciality Hospital 8/355 (2.3%), and Wad Medani Police Hospital 10/355 (2.8%). All clinical samples were cultured on blood agar and MacConkey agar. Different biochemical tests, Gram's stain and amplification of arcC gene were used to identify the causative pathogens. The results confirmed the existence of Staphylococcus aureus in seventy two (72);(20.3%) of the enrolled patients among which thirty three (33); (45.8%) methicillin resistant Staphylococcus aureus were identified when using modified Kirby Bauer method. The distribution of MRSA among enrolled patients at the hospitals and medical centers were as follows: general surgery at Wad Medani Teaching Hospital 19/72 (26.4%), Gynaecology and Obstetrics Teaching Hospital 5/72 (7%), Orthopaedic Surgery Hospital 1/72 (1.4%), Dr. Ahmed Abdella Hamadein Hospital for Dermal Diseases 2/72 (2.8%) and Institute of Nuclear Medicine, Moleculour Biology and Oncology 6/72 (8.3%). While other medical centers included in the study were appeared free from MRSA. Confirmation of the results of methicillin disk diffusion Kirby Bauer method was conducted by amplifying mecA gene. Furthermore all MRSA isolates were tested against other empirical antibiotics, the results were as follows: 14/33 (42.40%) were resistant to co-trimoxazole, 15/33 (45.50%) were resistant to cephalexin, 22 /33 (66.70%) were resist to tetracycline, 20 /33 (60.60%) were resistant to cefotaxime, 6/33 (18.20%) were resistant to ciprofloxacin and erythromycin, 12 /33 (36.40%) were resistant to pefloxacin and ofloxacin, 33/33 (100%) were resistant to cloxacillin, 7/33 (21.20%) were resistant to clindamycin, 3 /33 (9.10%) were resistant to gentamycin, 30/33 (90.90%) were resistant to ceftriaxone, and 9/33 (27.30%) were resistant to cefuroxime . All MRSA isolates were examined against vancomycin antibiotic using modified Kirby Bauer disk diffusion method. The results obtained excluded the existent of VRSA among all MRSA isolates. More confirmation was adopted by amplifying Van A, Van B genes. The study concluded that MRSA still consider as a great in medical field. Also it confirmed the sensitivity of molecular method in the diagnosis of MRSA as well as VRSA among infected patients. Thus, it can substitute the long conventional methods