Methicillin-Resistant Staphylococcus aureus: Molecular Characterization, Evolution, and Epidemiology

Abstract

SUMMARY, a major human pathogen, has a collection of virulence factors and the ability to acquire resistance to most antibiotics. This ability is further augmented by constant emergence of new clones, making a "superbug." Clinical use of methicillin has led to the appearance of methicillin-resistant (MRSA). The past few decades have witnessed the existence of new MRSA clones. Unlike traditional MRSA residing in hospitals, the new clones can invade community settings and infect people without predisposing risk factors. This evolution continues with the buildup of the MRSA reservoir in companion and food animals. This review focuses on imparting a better understanding of MRSA evolution and its molecular characterization and epidemiology. We first describe the origin of MRSA, with emphasis on the diverse nature of staphylococcal cassette chromosome (SCC). and its new homologues (, , and), SCC types (13 SCC types have been discovered to date), and their classification criteria are discussed. The review then describes various typing methods applied to study the molecular epidemiology and evolutionary nature of MRSA. Starting with the historical methods and continuing to the advanced whole-genome approaches, typing of collections of MRSA has shed light on the origin, spread, and evolutionary pathways of MRSA clones.

Fast and accurate bacterial species identification in biological samples using LC-MS/MS mass spectrometry and machine learning

“…Indeed, broad spectrum antimicrobials are commonly prescribed to patients before obtaining the results of the clinical microbiological analysis, a practice that might not be sufficient to control the infection, especially when one considers the risk posed by antibiotic-resistant species and their transmission in the hospital environment or the community (62). For instance, Staphylococcus aureus has developed resistances to many antimicrobial drugs including last resort antibiotics and expresses an arsenal of virulence factors (63)(64)(65). Or, in agriculture, the systematic use of antibiotics in farming leads to the selection of resistant bacteria that have been found in commercial food products (66).…”

Constructing and deconstructing the bacterial cell wall

“…S. aureus is a bacterial pathogen of humans and livestock. It is encountered as a β‐lactam‐susceptible strain (referred to customarily as methicillin‐susceptible S. aureus , MSSA) and as β‐lactam‐resistant strains (MRSA, encountered as a variety of strains) . Here, methicillin refers to a specific second‐generation penicillin that was developed decades ago as especially active against MSSA, as a result of its stability to the hydrolytic deactivation of its β‐lactam substructure (in contrast to first‐generation penicillins) as catalyzed by a plasmid‐encoded β‐lactamase (BlaZ).…”

“…It is encountered as a β-lactam-susceptible strain (referred to customarily as methicillin-susceptible S. aureus, MSSA) and as β-lactam-resistant strains (MRSA, encountered as a variety of strains). [121][122][123][124][125][126][127][128] Here, methicillin refers to a specific second-generation penicillin that was developed decades ago as especially active against MSSA, as a result of its stability to the hydrolytic deactivation of its β-lactam substructure (in contrast to first-generation penicillins) as catalyzed by a plasmid-encoded β-lactamase (BlaZ). The acquisition of the gene for the BlaZ β-lactamase was selected by S. aureus in response to the clinical use of first-generation penicillins, which were in turn efficiently deactivated by the enzyme.…”

<i>vicK</i> Gene as Potential Identification Marker for <i>Staphylococcus aureus</i>

“…The organism is a common microflora of human epithelia exhibiting permanent nasal colonization between 30% -40% of the human population [1]. Symptomatic S. aureus infections may occur fol-lococcus aureus (HA-MRSA) [5] [6]. HA-MRSA infections are usually difficult to treat due to their resistance to multiple antibiotics, contributing to a significant mortality and morbidity [7].…”