Estimation the Expression of Glucose-Dependent Biofilm-Encoding icaA and icaD Genes in Methicillin Resistant Staphylococcus aureus Isolates

Abstract

Staphylococcus aureus is known globally for causing different illnesses, ranging from mild to life-threatening infections such as septicaemia. S. aureus can develop a complicated structure of extracellular polymeric biofilm that shelters the cells against hostile conditions, where drugs are becoming increasingly partially or fully inactive against S. aureus as these agents fail to penetrate properly biofilm matrix surrounding the bacterial cells properly. Different clinical specimens were collected from different hospitals in Baghdad, Iraq. Identification of S. aureus was accomplished by using conventional biochemical reactions then confirmed by detection of Sa442 gene specific to S. aureus by PCR technique. Vitek 2 compact system was employed to identify antimicrobial susceptibility pattern of 39 isolates against 14 antibiotics. The ability of S. aureus isolates to form biofilms was assessed using the microtiter plate technique. Furthermore, the presence of icaA and icaD genes was examined in all isolates using PCR. Moreover, the biofilm thickness as well as the expression of icaA and icaD genes was measured at different concentrations of glucose (0, 0.5, 1, 1.5 and 2%) for selected MRSA and MSSA isolates. All isolates identified as S. aureus by PCR exhibited the presence of the Sa422 gene. The highest resistant percentage was identified against Benzylpenicillin (100%) followed by oxacillin and Clindamycin (82% and 62 % respectively). All isolates were capable of producing biofilm layers with 15% being strong biofilm producers and all of the isolates harboured both of icaA and icaD genes. The biofilm increased with increasing glucose concentration while the expression of icaA and icaD genes was downregulated. It was concluded that there is a pressing need for enhanced surveillance, improved antibiotic stewardship, and the development of novel anti-biofilm strategies to combat the rising threat of multidrug-resistant S. aureus in healthcare settings.