Abstract

The ability to adhere and produce biofilms is characteristic of enhanced virulence among isolates of methicillin-resistant Staphylococcus aureus (MRSA). The aim of the study is to find out whether these characteristics are consistently similar among isolates variations of MRSA. The study used 30 various isolates of MRSA belong to 13 spa types and 5 MLST types and determined the aggregation, the adherence, and the production of biofilms and slime for each isolate. The methods used to evaluate these characteristics were a modified Congo red agar assay (MCRA), a microtiter plate assay (MPA), high-magnification light microscopy, scanning electron microscopy (SEM), and PCR. The study found that isolates belonging to similar Spa, SCCmec, and ST types have similar abilities to produce biofilms; however, their ability to produce slime on CRA was found to be different. Moreover, isolates that have different Spa types showed high variation in their ability to produce biofilms. The results of light microscope revealed the isolates that produced strong and weak biofilms and formed similar aggregation on the glass surfaces. SEM results showed that all 30 MRSA isolates that were tested were 100% positive for biofilm formation, although to varying degrees. Further testing using PCR confirmed that 100% of the 30 isolates tested were positive for the presence of the icaADBC, fnbA, eno, ebps, clfA, and clfB genes. The prevalence of fib, cna, fnbB, and bbp in MRSA clones was 90, 93.33, 53.33, and 10%, respectively. This study indicate that differences in biofilm production capacities are caused by the differences in surface protein A (Spa) type and are not due to differences in MLST and SCCmec types.

Highlights

  • Many bacterial pathogens and nosocomial infections are the cause of acute and chronic infections due to their ability to form biofilms [1, 2]

  • This study indicate that differences in biofilm production capacities are caused by the differences in surface protein A (Spa) type and are not due to differences in multilocus sequence typing (MLST) and Staphylococcal cassette chromosome mec (SCCmec) types

  • Even though biofilm-forming properties have been well demonstrated by the members of the Staphylococcus genus such as S. epidermidis and S. aureus, it is less studied in modern methicillin-resistant Staphylococcus aureus (MRSA), which has evolved from several clonal lineages of methicillin-susceptible S. aureus strains via acquisition of a mobile genetic element called Staphylococcal cassette chromosome mec (SCCmec)

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Summary

Introduction

Many bacterial pathogens and nosocomial infections are the cause of acute and chronic infections due to their ability to form biofilms [1, 2]. Even though biofilm-forming properties have been well demonstrated by the members of the Staphylococcus genus such as S. epidermidis and S. aureus, it is less studied in modern methicillin-resistant Staphylococcus aureus (MRSA), which has evolved from several clonal lineages of methicillin-susceptible S. aureus strains via acquisition of a mobile genetic element called Staphylococcal cassette chromosome mec (SCCmec). Many studies have concluded that the formation of the biofilm is caused by adherence at late stages of bacterial growth. In this process, the organisms stick to each other through polysaccharide intercellular adhesion (PIA), which is synthesised by products of the icaADBC operon [4]. This study hypothesised that different S. aureus protein (Spa) gene sequencing, multilocus sequence typing (MLST), and Staphylococcal cassette chromosome mec (SCCmec) typing are among the factors that affect the ability of the bacteria to form biofilms. Differences occurring due to clonal variation would indicate a need for accurate clonal identification for effective biofilm management upon infection

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