Phenotypic and Genotypic Study of Staphylococcus Haemolyticus and Staphylococcus Warneri Clinically Isolated from the Bloodstream

Abstract

Background: The Staphylococcus haemolyticus and Staphylococcus warneri are coagulase-negative staphylococci (CoNS) as part of human skin’s natural flora. In recent years, CoNS has increased its visibility as opportunistic pathogens acquired in hospital patients. This study aims to isolate S. haemolyticus and S. warneri strains from patients with bloodstream infections and to analyze the antimicrobial profile of these bacteria by molecular detection of the mecA gene. Materials and Methods: Four hundred and twenty-three clinical blood samples were collected from patients admitted to general three hospitals in Hilla city, Iraq, during the period from September 2021 to July 2022. Blood samples were inoculated immediately into blood bottles containing 70 ml of Brain-Heart Infusion Broth. All isolates were identified by morphology, biochemical tests, and VITEK 2 automated system (bioMerieux, France). The Congo red agar plate test was used to detect biofilm production. The mecA gene was detected by conventional polymerase chain reaction. Results: S. haemolyticus (nine isolates) and S. warneri (six isolates) were detected out of 423 clinical blood samples. Molecular detection of the mecA gene was detected in all 15 isolates. As well 11 (73.3%) isolates were β-lactam resistant and biofilm production. The results of oxacillin-resistance minimum inhibitory concentration (MIC) (≥4 mg/ml) showed that 11 (73.3%) of the 15 isolates were oxacillin and methicillin-resistant CoNS (MR-CoNS). Susceptibility to various isolates (MICs µg/ml) using VITEK 2 system showed erythromycin (≥8 µg/ml), rifampin (≥4 µg/ml), clindamycin (≥4 µg/ml), and trimethoprim-sulfamethoxazole (≥4 µg/ml) resistance were (80%), (13.3%), (20%), and (53.3%), respectively. All isolates were (100%) sensitive to linezolid (≥8 µg/ml) and teicoplanin (≥32 µg/ml). Conclusions: The S. haemolyticus and S. warneri are serious infections associated with bacteremia and septicemia infections. Linezolid, teicoplanin, and rifampin are the drug of choice for the treatment of infections caused by MR-CoNS isolates. A high rate of the mecA gene and biofilm production is present in these bacteria.

Keywords

• antibiotics resistance
• bacteremia
• biofilm
• staphylococcus haemolyticus
• staphylococcus warneri