Perfil fenotípico, genotípico e fatores de virulência de Staphylococcus aureus isolados de casos clínicos e de portadores assintomáticos em um hospital do interior do Paraná

Abstract

Healthy subjects are colonized by the Staphylococcus aureus since breastfeeding and this microorganism can be found in the nasopharynx, skin and vagina. From these areas this bacteria can be transmitted to susceptible subjects causing them infections. The S. aureus has been associated to hospital and community infections whereas the severity of the disease depends on the expression of virulence factors and the resistance profile towards antimicrobial agents applied in clinical practice. The aim of this study was to assess the phenotypic and genotypic profile and the virulence factor of Staphylococcus aureus samples isolated from symptomatic and asymptomatic carriers. Therefore 147 S. aureus samples stored at the Maringá State University Laboratory were used, where 68 were drawn from infection associated with health care cases and 79 were drawn from asymptomatic carriers. The susceptibility to antimicrobial agents was assessed using the disc diffusion method as recommended by the CLSI, and for the oxacillyn and vancomycin resistance the minimum inhibitory concentration (MIC) determination test was also used. The DNA was extracted with Ctab and the Polymerase Chain Reaction (PCR) technique was applied for the genetic characterization with the RW3A oligonucleotide, identification of the mecA gene, detection of the gene for the production of PVL and detection of the icaA and icaD genes. All S. aureus samples showed a wide range of resistance to the antimicrobial agents often used in clinical practice. The MIC test results showed that from the 68 symptomatic samples, 58 (85%) presented oxacillyn resistance and 55 (95%) of them carried the mecA gene. For the 58 oxacillyn resistant samples identified by the MIC test, 55 (98%) also displayed resistance using the disc diffusion method. Among the 79 asymptomatic carriers samples, seven (9%) were oxacillyn resistant by the MIC test and six (86%) expressed the mecA gene. For the seven oxacillyn resistant samples from asymptomatic carriers, six (86%) also showed resistance by the disc diffusion method. The samples isolated from asymptomatic carriers had 100% resistance for penicillyn and cefoxitin and 0% to linezolid, telithromycin and teicoplamin. The samples isolated from symptomatic cases had 100% resistance for penicillin, cefoxitin and telithromycin and 0% to teicoplamin. All samples were sensitive for vancomycin by both methods applied. The PVL gene was detected in only one (14%) of the seven oxacyllin resistant samples isolated from asymptomatic carriers. The icaA and icaD genes were both detected in only one (14%) of the seven oxacillyn resistant samples isolated from asymptomatic carriers and in 41 (60%) of 68 samples isolated from symptomatic clinical cases. The genetic characterizations of the 79 samples isolated from asymptomatic cariers showed that 15 of them shared a similarity rate of 100% and 23 showed a similarity rate above 80%. From the 68 symptomatic clinical samples, 19 presented a similarity rate of 100% and three shared a similarity rate above 90%, 23 above 84% and 19 shared a similarity rate around 80%.