Characterization of Clinical MRSA Isolates from Northern Spain and Assessment of Their Susceptibility to Phage-Derived Antimicrobials

Marina Salas,Andrea Álvarez,Laura García,Beatriz Iglesias,Diana Gutiérrez,Pilar García,Ana Rodríguez,Lucía Fernández,Maciej Wernecki,Elisabeth Prieto

doi:10.3390/antibiotics9080447

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) is a prevalent nosocomial pathogen, causing a wide range of diseases. The increased frequency of MRSA isolates in hospitals and the emergence of vancomycin resistance have sparked the search for new control strategies. This study aimed to characterize sixty-seven MRSA isolates collected from both infected patients and asymptomatic carriers in a Spanish hospital. RAPD-PCR allowed the identification of six genetic patterns. We also investigated the presence of genes involved in producing adhesins, toxins and the capsule; the biofilm; and antimicrobial resistance. A notable percentage of the isolates carried virulence genes and showed medium-high ability to form biofilms. Next, we assessed the strains’ susceptibility to two phages (phiIPLA-C1C and phiIPLA-RODI) and one endolysin (LysRODI). All strains were resistant to phiIPLA-C1C, and most (70.2%) were susceptible to phiIPLA-RODI. Regarding LysRODI, all strains displayed susceptibility, although to varying degrees. There was a correlation between endolysin susceptibility and the random amplification of polymorphic DNA (RAPD) profile or the presence of some virulence genes (fnbA, eta, etb, PVL and czr), but that was not observed with biofilm-forming ability, strain origin or phage sensitivity. Taken together, these findings can help to explain the factors influencing endolysin effectiveness, which will contribute to the development of efficient therapies targeting MRSA infections.

Highlights

The pathogenicity of Staphylococcus aureus relies on its capacity to synthetize an important number of toxins and virulence factors, together with its ability to form biofilms [1]
S. aureus chromosome consists of mobile genetic elements (MGEs), such as pathogenicity islands, bacteriophages, chromosomal cassettes, transposons and plasmids, all of which can be acquired by horizontal transfer between strains
Most of the variables analyzed and endolysin susceptibility were independent according to the result of the Infections caused by multidrug-resistant methicillin-resistant S. aureus (MRSA) strains are becoming more and more frequent in hospitals all over the world

Summary

Introduction

The pathogenicity of Staphylococcus aureus relies on its capacity to synthetize an important number of toxins and virulence factors, together with its ability to form biofilms [1]. There is an upward trend in the selection and spread of antibiotic resistance determinants amongst S. aureus strains. All these characteristics allow this bacterium to successfully evade host defenses and conventional. Antibiotics 2020, 9, 447 antibiotic treatment strategies [2] It is worth highlighting the adaptability of this pathogen, which might, to some extent, be due to its genome plasticity. The fact that S. aureus can adapt to multiple environments has likely contributed to the appearance of community-associated (CA-MRSA) and livestock-associated (LA-MRSA) strains, which have evolved independently from HA-MRSA strains

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