Determination of etiologic agents of catheter related bloodstream infection and investigation of biofilm formation by phenotypic and genotypic methods

Biofilm, which allows microorganisms to attach to the surfaces and proliferate, is of great importance especially in foreign body infections. In our study, the distribution of microorganisms causing KİKDE, phenotypic biofilm formation properties and presence of biofilm related genes were investigated. Between September 1 2018 and January 31 2019, catheter tip samples and blood samples drawn from a catheter hub or a peripheral vein sent to our laboratory for culture were routinely processed. Culture results and clinical information of the patients were evaluated and the cases of CRBSI were determined. The number of the CRBSI attacks is 89. A total of 93 microorganisms causing CRBSI were isolated. Of these, 62,36% of the pathogens were gram positive bacteria. The most common etyologic agents were S. epidermidis (21,51%), S. aureus (17,20%) and Candida albicans (13,98%). Microtitre plate method was used for evaluation of phenotypic biofilm formation ability. Biofilm production was observed in 90% (18/20) of S. epidermidis isolates, 87,5% (7/8) of S. hominis isolates, all of S. haemolyticus isolates (8/8); and 91,4% (32/35) of all CNS. Biofilm formation rate in S. aureus isolates was 75%. All of the gram negative bacteria tested (A. baumannii and P. aeruginosa) were biofilm positive. The incidence of strong biofilm was significantly higher in gram negative bacteria (60,0%) than gram positive bacteria (19,6%) (p= 0.033). The frequency of icaA, icaD, icaB, icaC genes was 51%, 31%, 43%, 17% in CNS and; 100%, 94%, 56% 94% in S. aureus isolates. Bap, ompA, epsA, bfms and blaPER-1 genes were detected in 100%, 100%, 60%, 100% and 80% of Acinetobacter baumannii isolates, respectively. No statistically significant relationship was found between biofilm formation and the presence of genes investigated (p>0,05). All staphylococci were susceptible to vancomycin. Methicillin resistance was detected in 94,29% (33/35) of CNS and 37,50% (6/16) of S. aureus isolates. All Acinetobacter baumannii isolates (5/5) and 40% (2/5) of P. aeruginosa isolates were resistant to carbapenem. All K. pneumoniae (3/3) and E. coli (3/3) isolates were susceptible to carbapenem. Biofilm was detected in 90,9% (30/33) of MRCNS. Two CNS sensitive to methicillin produced weak biofilm. Biofilm formation rate of MRSAs (83,3%; 5/6) is higher than MSSAs (70,0%; 7/10). However, there was no statistically significant difference between biofilm production and methicillin resistance (p> 0.05). There was no statistically significant relationship between the presence of biofilm production and carbapenem resistance, too (p> 0.05). As the biofilm production level increased, the rate of MDR increased. However, no statistically significant difference was found between the presence of biofilm production and MDR (p= 0.153). It is noteworthy that all seven biofilm negative isolates resulted in discharge, while the mortality rate increased with increasing biofilm production levels (10,3%, 11,1% and 37,5%, respectively, for weak, medium and strong biofim forming). Strong biofilm formation was seen in more than half (60,0%) of the patients who died but only 19,6% of the patients who were discharged and the difference was statistically significant (p= 0.015). However, there was no statistically significant relationship between the presence of biofilm production and mortality (p = 0.587). Future studies on biofilm will also be useful in understanding the biofilm formation and finding solutions to biofilm infections. Key Words: Catheter - related bloodstream infection, biofilm, microtiter plate method, biofilm gene, Real-time PCR.