A role of methicillinresistant Staphylococcus aureus strains and related molecular genetic features in developing purulent-necrotic forms of the diabetic foot syndrome

Purulent-necrotic  complications in patients with diabetic foot syndrome is one of the main causes resulting in amputation and disability, or even lethal outcome. Our study was aimed at investigating a role played by MRSA and related molecular genetic features, as well as antibiotic resistance in developing purulent-necrotic forms of the diabetic foot syndrome in Krasnoyarsk, in the 2010–2016 period. A microbiota profile related to purulent-necrotic complications, antibiotic susceptibility, as well as the molecular genetic features of methicillin-resistant Staphylococcus aureus were examined in 240 patients with diabetic foot syndrome. A bacteriological method was used to investigate microbiota profile related to purulent complications. Antibiotic sensitivity was analyzed by disc-diffusion method; staphylococcal antibiotic sensitivity was evaluated by screening, PCR, solid medium serial dilution, in accordance with the CLSI and EUCAST international recommendations. Genotyping and examining molecular genetic features were performed by using PCR, M-PCR, and sequencing. The data were analyzed by using WHONET (WHO) software. Significance level was set at p <0.05. It was found that microbiota profile linked to purulent-necrotic forms of the diabetic foot syndrome was presented by various Gram-negative microorganisms including Enterobacteriaceae spp. and non-fermenting bacteria accounting for 34.4% and 19.1%, respectively, as well as Gram-positive microorganisms found in 46.5% cases, including S. aureus (18.4% cases). Moreover, microorganisms were characterized by multiresistance to diverse antimicrobial drugs: percent-age of BLDS- and MBL-producers as well as MRSA comprised 36.4%, 30.3%, and 36.4%, respectively. Further, MRSA ST239/spa3(t037)/agr1/SCCmecIII.1.1.2(IIIA)/coaIV/tst+  clone dominated in patients with purulent-necrotic  forms of diabetic foot syndrome admitted to the right-bank and left-bank hospitals in the city of Krasnoyarsk that was characterized by a high virulence level and multidrug resistance. Next, subdominant MRSA genetic variants were presented by ST8/spa1(t008)/agr1/SCCmecIV.3.1.1/CoaIII and ST12/spanew(t156)/agr1/SCCmecUT/coaIorVII characterized by resistance to 1–2 groups of antimicrobials apart from β-lactams. Importantly, similar MRSA genetic variants earlier isolated in patients with other nosological entities common in this geographic region were also mainly verified in patients with purulent-necrotic forms of diabetic foot syndrome admitted to Krasnoyarsk hospitals. In particular, it was demonstrated that MRSA isolates predominantly belonging to the same genetic variants were detected in patients with purulent-necrotic forms of diabetic foot syndrome hospitalized both at the right-bank and left-bank hospitals of the city of Krasnoyarsk. Thus, long-term hospitalization of patients with purulent-necrotic forms of diabetic foot syndrome as well as subsequent repeated admittance to other hospitals in the city of Krasnoyarsk facilitates inter-hospital bacterial strain transmission