Association between biofilm formation, structure and antibiotic resistance in Staphylococcus epidermidis isolated from neonatal septicemia in southwest Iran

Abstract

Background: Staphylococcus epidermidis has emerged as the pathogen from neonatal septicemia. Antibiotic resistance and the capability of biofilm formation make these infections much harder to treat. Hence, the aim of this study was to investigate the association between biofilm formation, structure and antibiotic resistance in S. epidermidis isolated from neonatal septicemia. Methods: Overall, 65 S. epidermidis isolates were recovered from blood cultures of neonatal septicemia. Antibiotic resistance pattern and the biofilm production were determined using phenotypic methods. The presence of ica operon, the bhp, the aap genes and SCCmec types were screened using PCR. Results: Most S.epidermidis isolates were resistant to erythromycin, while all isolates were sensitive to linezolid and vancomycin. Fifty-three percent of S.epidermidis isolates were resistant to methicillin. SCCmec types II was found commonly among methicillin-resistant S. epidermidis (MRSE) strains. The biofilm formation was observed in 65% of S.epidermidis isolates and the majority have polysaccharide matrix. icaA and icaD genes were found in 40% and 19% of isolates. Twenty-three isolates (62%) produced dissolvable polysaccharide intercellular adhesion (PIA)-dependent biofilms in SM after growth in TSB with NaCl and 14 (37%) isolates produced dissolvable protein-dependent biofilms in PK after growth in TSB with glucose. Three isolates (62%) produced dissolvable polysaccharide intercellular adhesion. Conclusion: Our data indicate the high rates of antibiotic resistance and the capability of biofilm formation among S. epidermidis isolates. Hence, the transmission of these strains can cause an increased risk of serious nosocomial infections.

Keywords: S. epidermidis; antibiotic resistance; biofilm formation.

Figure 1

Antibiotic resistance rate among all 65 S.epidermidis isolated. Abbreviations: AM, amikacin; GN, gentamicin; FOX, cefoxitin; CIP, ciprofloxacin; E, erythromycin; T, tetracycline; TS, sulfamethoxazole-trimethoprim; ATH, azithromycin; CLA, clarithromycin; LZD, linezolid; RP, rifampin; DXT, doxycycline; MN, minocycline; TN, tobramycin; CD, clindamycin; Lecv, levofloxacin; V, vancomycin.

Figure 2

Comparison of antimicrobial susceptibilities between biofilm and nonbiofilm producing S. epidermidis isolated. Abbreviations: AM, amikacin; GN, gentamicin; FOX, cefoxitin; CIP, ciprofloxacin; E, erythromycin; T, tetracycline; TS, sulfamethoxazole-trimethoprim; ATH, azithromycin; CLA, clarithromycin; LZD, linezolid; RP, rifampin; DXT, doxycycline; MN, minocycline; TN, tobramycin; CD, clindamycin; Lecv, levofloxacin; V, vancomycin; Biofilm pos, biofilm positive; Biofilm neg, biofilm negative.

Figure 3

Distribution of SCC typing in S. epidermidis biofilm producer and nonbiofilm producer. Abbreviations: mecA, methicillin-resistant gene; SCC, staphylococcal cassette chromosome; Biofilm pos, biofilm positive; Biofilm neg, biofilm negative.

Figure 4

Distribution of biofilm formation genes among biofilm producer and nonbiofilm producer S. epidermidis isolated. Abbreviations: ica, intercellular adhesion; aap, accumulation-associated protein; bhp, biofilm associated protein; Biofilm pos, biofilm positive; Biofilm neg, biofilm negative.