Emerging Resistance Mechanisms in Gram-Positive Bacteria Isolated From Septicemia Cases in ICUs: A Focus on Genotypic Insights

Background Bloodstream infections (BSIs) are associated with high morbidity and mortality, especially in intensive care unit (ICU) settings. The most common Gram-positive pathogens, methicillin-resistant Staphylococcus aureus (MRSA) and coagulase-negative Staphylococci (CoNS), are likely to cause BSIs. The phenotypic and genotypic characteristics of multidrug-resistant (MDR) Staphylococcal species isolated from patients admitted to the ICU with septicemia were evaluated for better treatment outcomes. Materials and methods A cross-sectional study was conducted at Sree Balaji Medical College and Hospital over two years (July 2022 to June 2024). Blood samples in blood culture bottles received in the laboratory from ICU patients with suspected sepsis were included in this study. The BacT/ALERT® 3D system (bioMérieux, France) was used to assess the bacterial growth. The VITEK® 2 system (bioMérieux, France) and conventional methods were used to identify Gram-positive isolates. Antibiotic susceptibility was determined by the Kirby-Bauer disc diffusion method, and polymerase chain reaction (PCR) was used to detect genes like mecA, icaA, and icaD genes. Results Out of 274 blood samples, eight (2.9%) were contaminants, and 121 (44.2%) were culture-positive as true pathogens. Eighty-seven (71.9%) Gram-positive isolates were identified from the positive blood cultures, of which CoNS was predominant (51, 58.6%), followed by Staphylococcus aureus (25, 28.7%). Methicillin resistance was observed in 10 (13.1%) Staphylococcus aureus and 14 (18.4%) CoNS isolates. PCR detected the mecA gene in 20 (83.3%) methicillin-resistant isolates and biofilm-related genes icaD in 64 (84.2%) and icaA in 58 (76.3%). Vancomycin and teicoplanin showed high effectiveness. Conclusions This study has emphasized the importance of molecular screening for the mecA, icaA, and icaD genes in framing antibiotic regimens. The findings emphasize the efficacy of vancomycin, teicoplanin, and linezolid in combating MDR Staphylococcus infections in ICUs of hospitals and demonstrate the importance of antibiotic stewardship.