Biofilm formation frequency and drugs resistance of Staphylococcus aureus isolated from clinical samples

The prevalence of Extensively Drug-Resistant (XDR), Multidrug-Resistant (MDR) and Pan-drug-Resistant (PDR) phenotypes amongst S. aureus strains have become one of the greatest challenges. This study aimed to determine the association of XDR, MDR, PDR phenotypes, and biofilm formation ability in S. aureus isolates which collected from patients attending to Al-Kafeel Hospital and Al-Hussein General Teaching Hospital in Karbala province, Iraq. During the months of April to June 2020, clinical samples of urine, burns, and tonsil swabs were taken from all hospitalized patients. Conventional biochemical techniques were used to identify S. aureus strains, and the Kirby-Bauer disc diffusion method was used to determine antibiotic susceptibility. Tissue culture plate method (TCP), tube method (TM), and Congo red agar method (CRA) were used to assess the ability of biofilm formation. S. aureus was found in 31 of the isolates. Tonsil specimens were the source of the majority of S. aureus isolates 44.44 %, followed by urine specimens 30 %, and burn specimens 12.5%. The highest resistance was observed to penicillin G 96.77%, and the lowest resistance was observed to glycopeptides category (vancomycin) 3.23%. Out of the 31 isolates, 35.48%, and 51.61% were XDR and, MDR respectively. Among the isolates, no PDR phenotype was found. A high percentage of biofilm formation (67.7%) was observed in TCP method, which detected 9(29.03%) isolates as strong, followed by TM (51.6%), which showed 7(22.6%) strong biofilm producers, but CRA yielded lower percentage 12(38.7%) isolates. Also the high percentage of biofilm formation was observed in isolates of burns 100%. Antibiotic resistance was shown to be greatest and lowest against penicillin G and vancomycin, respectively. Therefore, penicillin G should not be used in the empirical therapy of S. aureus infections. Also, extensively drug-resistant (XDR) was significantly higher in most biofilm producing isolates.