Analysis of phenotypic and genotypic methods for determining the biofilm-forming abilities of CoNS isolates: Association with hemolysin production and the bacterial insertion sequence elements IS256/257

Abstract

Biofilm-forming Coagulase-negative staphylococci (CoNS) has been considered the etiological agent in various infections. The purpose of this study was to determine the biofilm-producing ability and to explore the virulence factors associated with biofilm formation in these isolates. Ninety-one isolates of CoNS were characterized and subjected to biofilm detection by the microtiter plate (MTP) and Congo red agar (CRA). The presence of biofilm-associated genes, insertion sequence elements IS256 and IS 257, and genes responsible for producing hemolytic toxins in CoNS isolates were screened using the PCR method. Out of the 91 clinical isolates of CoNS, 49 (53.8), 37 (40.7%), and 5 (5.5%) isolates were identified as S. epidermidis, S. haemolyticus, and S. saprophyticus, respectively. The prevalence of biofilm-associated genes icaA, icaB, icaC, icaD, atlE and bhp in CoNS was: 27.5%, 16.5%, 21%, 24.2%, 52% and 1% respectively. The incidence of hemolysin-encoding genes was as follows; hla (88%), hla_yiD (63%), hlb (47.3%), and hld (56%). Furthermore, the occurrence of IS256/IS257 and the capability to form a biofilm. In conclusion, high rates of hemolysin-producing CoNS isolates were detected in both biofilm-forming and resistant strains. Thus, the co-existence of hemolysin and biofilm-associated genes play an important role in emerging violent CoNS bacteria. The prevalence of hemolysin-producing CoNS isolates also suggests the presence of other virulence factors. However, we believe that the explanation for ica operon being more associated with the hemolysin production in this study could be the current investigation's geographical location. Due to the hemolysin production and biofilm formation correlation, it is necessary to study epidemiology and identify these factors.