Detection of the agr System and Resistance to Antimicrobials in Biofilm-Producing S. epidermidis.

Valéria Cataneli Pereira,Adilson De Oliveira,Letícia Calixto Romero,Danilo Flávio Moraes Riboli,Luiza Pinheiro-Hubinger,Maria De Lourdes Ribeiro De Souza Da Cunha,Katheryne Benini Martins

doi:10.3390/molecules25235715

Abstract

The ability of Staphylococcus epidermidis to produce virulence factors, such as biofilm, added to its increased resistance to antimicrobials can cause infections that are difficult to treat. Many staphylococcal virulence factors are under the control of the accessory gene regulator (agr). The objective of this study was to establish the agr locus and susceptibility of biofilm-producing S. epidermidis specimens to antimicrobial agents, through PCR reactions, reverse transcription polymerase chain reaction (RT-PCR), and the determination of minimum inhibitory concentration (MIC), and to analyze the clonal profile of 300 strains isolated from blood culture specimens from inpatients at a University Hospital in Brazil, over a 20-year period by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) techniques. The ica operon expression was shown in 83.6% strains, bhp gene in 11.5%, and aap gene in 32.8%. Oxacillin resistance was detected in 90.1%, while 4.9% showed tigecycline resistance, and intermediate resistance to quinupristin/dalfopristin was identified in 0.4%. Clonal profile determination showed 11 clusters, with the ST2 type determined as the major cluster. The S. epidermidis biofilm producer demonstrated a predominance of agr I locus, oxacillin resistance, and SCCmec III as well as the potential dissemination of pathogenic clones in hospital settings over long periods.

Highlights

Coagulase-negative Staphylococci (CoNS) are members of the genus Staphylococcus and major colonizers of the human microbiota
The objective of this study was to determine the agr and antimicrobial susceptibility of S. epidermidis isolated from blood culture capable of producing biofilm and to analyze the clonal profile of blood culture isolates from patients hospitalized over a period of 20 years
We investigated the genes related to biofilm formation in the 300 isolates and the presence of ica operon genes and/or bhp and aap genes was detected in 163 (53.3%)

Summary

Introduction

Coagulase-negative Staphylococci (CoNS) are members of the genus Staphylococcus and major colonizers of the human microbiota. Staphylococcus epidermidis is the most commonly isolated microorganism in clinical materials and being opportunistic, it can cause serious infections, mainly in immunosuppressed patients and those who use prosthetics [1]. The ability to produce virulence factors, such as biofilm, and increased resistance to antimicrobials may make it difficult to treat infections caused by these microorganisms [2]. Biofilm, considered the main virulence factor of CoNS, is defined as a complex interaction of microorganisms incorporated into an extracellular matrix of polysaccharide, proteins, and nucleic acid [3], which confers protection to the involved microorganisms and prevent them from the host’s immune system action during infection [4]. In the constitution of the biofilm of Staphylococcus spp., some genes are involved in the coding of the most important substances and proteins: the ica operon, which carries the icaA, icaC, icaD, and icaB genes, the accumulation-associated protein (Aap), and the biofilm-associated protein homologue (Bhp) [3]

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