# A Comprehensive Phenotypic Characterization of Biofilm-Producing Coagulase-Negative Staphylococci: Elucidating the Complexities of Antimicrobial Resistance and Susceptibility

## TL;DR

This study examines biofilm-producing coagulase-negative staphylococci and their resistance to antibiotics, showing limited treatment options and the need for alternatives like linezolid.

## Contribution

The study provides a detailed phenotypic analysis of biofilm-producing CoNS and their antimicrobial resistance patterns in clinical settings.

## Key findings

- Staphylococcus haemolyticus was the most common CoNS species isolated, with high biofilm production.
- Most isolates showed multidrug resistance but high susceptibility to linezolid.
- Over 75% of CoNS isolates were from blood samples, indicating a significant role in bloodstream infections.

## Abstract

Background

Coagulase-negative staphylococci (CoNS) have emerged as significant pathogens in nosocomial infections, particularly in bloodstream infections and individuals linked to embedded therapeutic devices. CoNS predominantly affects immunocompromised or debilitated patients. Additionally, individuals with medical indwelling devices, such as a catheter for the urinary tract, valves for the cardiovascular system, pacemakers, and prosthetic joints, should receive medical attention. As a result of the organism's evolving resistance to multiple antibiotics, managing CoNS infections is becoming increasingly challenging. The formation of biofilms is a key factor contributing to the pathogenicity and antimicrobial resistance of CoNS, complicating treatment efforts and the resolution of infections.

Aim

The aim of this study is to identify CoNS species, examine their biofilm production, and evaluate their resistance to antibiotics.

Materials and methods

A cross-sectional study was conducted on patients admitted to the Microbiology Department at Krishna Hospital, Karad. Clinical samples included the following: blood, pus, urine, sputum, endotracheal tube aspirate, high vaginal swab, and central venous catheter.

Results

The occurrence of coagulase-negative Staphylococcus across the range of clinical samples consisted of blood (61 isolates, 75.3%), pus (seven isolates, 8.6%), urine (six isolates, 7.4%), sputum (three isolates, 3.7%), endotracheal tubes (two isolates, 2.5%), and high vaginal swab and central venous catheter (one isolate (1.2%) each). The most often isolated species was Staphylococcus haemolyticus (35 isolates, 43.2%) followed by Staphylococcus epidermidis (22 isolates, 27.2%) and Staphylococcus hominis (12 isolates, 14.8%). We assessed the production of biofilms using Congo red agar, with 62 isolates (76.5%) demonstrating biofilm formation. Among these, S. haemolyticus was the predominant species exhibiting biofilm production, with 29 isolates (46.8%) testing positive. This was followed by S. epidermidis with 19 isolates (30.7%) and S. hominis with nine isolates (14.5%).

Conclusion

The results of antibiotic susceptibility tests revealed multidrug resistance, with most isolates showing a high level of susceptibility to linezolid (84%) and complete resistance to penicillin. These findings highlight the clinical implications of limited treatment options and the need for alternative therapies, such as linezolid, in managing infections caused by coagulase-negative staphylococci.