Diagnosis of catheter-related infections in newborns and molecular epidemiology of Staphylococcus spp isolated

Abstract

Intravascular catheters are indispensable in modern medical practice, especially in Intensive Care Units (ICU). Although such catheters provide necessary vascular access, their use also puts patients at risk of local and systemic infectious complications. The migration of skin organisms at the site of catheter insertion is the most common route of infection for peripherally inserted catheters in the short term. Bloodstream infection related to catheter (BIRC) has been diagnosed when identical microorganisms are isolated from the culture of the catheter and blood cultures from the same patient. Semiquantitative and quantitative methods have greater specificity in identifying BIRC than traditional culture broth, where inoculum a clinically insignificant organisms can result in a positive catheter culture.It is known that the incidence of neonatal sepsis is inversely proportional to the weight birth and gestational age. The coagulase-negative, major components of normal skin flora, are often retrieved from infected catheters and neonates with sepsis associated with catheters. Antimicrobial resistance in these microorganisms is easily acquired, since the high trasmissibilidade of plasmids among strains in hospitals and excessive use of antimicrobial drugs have been constituted important factors in the transfer of resistance genes and selection of multidrug-resistant samples.The detection of oxacillin resistance in Staphylococcus is important to guide therapy and prevent the patient is unnecessarily treated with vancomycin, an antibiotic that presents therapeutic complications and may lead to selection of resistant strains. Genetic typing of SCCmec presents strong evidence for independent origins of MRSA acquired in hospitals and community-acquired MRSA. Antimicrobial therapy is guided by the results obtained from conventional antimicrobial testing of bacteria in the planktonic phase. However, bacteria associated with biofilm are 100-1000 times less susceptible to antibiotics than the bacteria in the planktonic phase, and active agents against these, but not against biofilms, fail to cure patients with infected prostheses.The increased use of medical devices have considerable impact on staphylococci in modern medicine. The ability to adhere, colonize and infect polymeric surfaces and consequent biofilm formation is considered a major virulence factor of the NCS. The tool of molecular typing more common in developed countries is the technique of PFGE (pulsed-field gel electrophoresis). The pulsed-field gel electrophoresis is a well documented method used for molecular epidemiological analysis related to the bacteria responsible for nosocomial infections, being held as the gold standard typing method for S. aureus. This project aims to study compared the semiquantitative technique and quantitative technique in the diagnosis of bloodstream infections related to catheters in newborns in the NICU of HC the FMB using the technique of PFGE to assess the similarity of the strains, the detection of oxacillin resistance from the search of the mecA gene and SCCmec typing of resistant strains, detection of biofilm production and determination of minimum inhibitory concentration (MIC) of antibiotics in the free cells and biofilms of Staphylococcus spp.