Virulence factors associated with Coagulase Negative Staphylococci isolated from human infections

Abstract

Infections caused by commensal organisms by changing to infectious life style generate much challenge to the current treatment strategies. Coagulase Negative Staphylococci (CoNS) are one of them, with their coexisting biofilm forming and multiple antibiotic resistance properties form important agents of nosocomial infection. To evaluate species distribution, biofilm formation, and antibiogram, CoNS isolates from various clinical samples were isolated. The presence of biofilm and associated genes icaAB, aap, atlE, embp, bhp, and fbe in CoNS was screened by PCR. The biofilm chemical composition and its correlation with the genotypes were also analysed. Staphylococcus epidermidis (59%) was found to be the most prevalent CoNS species. Most of the CoNS isolates harboring biofilm gene showed carbohydrate-protein-eDNA biofilm, whereas carbohydrate-protein biofilms were also observed. High percentage of multiple drug resistance, and biofilm gene frequency among these CoNS isolates point towards the need of periodic surveillance as CoNS are recently identified to cause difficult to treat infections.

Keywords: Biofilm; Biofilm heterogeneity; Coagulase Negative Staphylococci; Methicillin-resistant CoNS; ica ADBC; ica independent genes.

Fig. 1

Antibiotic sensitivity profile of clinical samples. Where, R, IR, and S indicate number of resistant, intermediate resistant, and sensitive CoNS isolates

Fig. 2

PCR amplification of icaAB at 564 bp. M marker, C negative control. Lanes 1–7 indicate S3, S7, S9, M5, M8, M9, and M10, respectively

Fig. 3

PCR amplification of fbe gene at 495 bp. M marker, C control. a Lanes 1 and 2 show isolate no: S3 and S8, b Lanes 1–6 indicate M3, M6, M9, M10, M12, and M14

Fig. 4

PCR for detection of bhp gene at 1583 bp. M marker, C control. Lane 1 indicates bhp positive sample M9

Fig. 5

PCR amplification of embp genes at 455 bp. M marker, C control. a Lanes no 1–8 show isolates S1, S2, S3, S4, S5, S6, S7 and S8, b Lanes 1–7 indicate isolates no: M3, M5, M9, M10, M12, M13, and M15, respectively

Fig. 6

PCR result of aap gene at 466 bp. M marker, C control. Lanes 1–13 indicate samples no: S8, M1, M2, M3, M6, M7, M8, M10, M11, M12, M13, M14, and M15, respectively

Fig. 7

PCR results of amplification of atlE gene at 682 bp. M marker, C control. Lanes no 1–8 indicate isolates S3, S7, S8, M3, M6, M9, M10, and M12, respectively

Fig. 8

HR-TEM analysis of biofilm formation of a S. epidermidis and b S. haemolyticus