Molecular Characterization of Staphylococcus aureus Isolates Associated with Nasal Colonization and Environmental Contamination in Academic Dental Clinics

Proteomic and metabolomic profiling of methicillin resistant versus methicillin sensitive Staphylococcus aureus using a simultaneous extraction protocol

Background

Understanding the biology of methicillin resistant Staphylococcus aureus (MRSA) is crucial to unlocking insights for new targets in our fight against this antimicrobial resistant priority pathogen. Although proteomics and metabolomic profiling offer the potential to elucidating such biological markers, reports of methodological approaches for carrying this out in S. aureus isolates remain limited. We describe the use of a dual-functionality methanol extraction method for the concurrent extraction of protein and metabolites from S. aureus and report on the comparative analysis of the proteomic and metabolomic profiles of MRSA versus methicillin sensitive S. aureus (MSSA).

Methods

Bacterial reference strains MRSA ATCC43300 and MSSA ATCC25923 were used. The conventional urea methodology was used for protein extraction and a methanol based method was used for concurrent proteins and metabolites extraction. Proteomic and metabolomic profiling was carried out using TimsTOF mass spectrometry. Data processing was carried out using the MaxQuant version 2.1.4.0.

Results

This study represents the first report on the utilization of the methanol extraction method for concurrent protein and metabolite extraction in Gram positive bacteria. Our findings demonstrate good performance of the method for the dual extraction of proteins and metabolites from S. aureus with demonstration of reproducibility. Comparison of MRSA and MSSA strains revealed 407 proteins with significantly different expression levels. Enrichment analysis of those proteins revealed distinct pathways involved in fatty acid degradation, metabolism and beta-lactam resistance. Penicillin-binding protein PBP2a, the key determinant of MRSA resistance, exhibited distinct expression patterns in MRSA isolates. Metabolomic analysis identified 146 metabolites with only one exclusive to the MRSA. The enriched pathways identified were related to arginine metabolism and biosynthesis.

Conclusion

Our findings demonstrate the effectiveness of the methanol-based dual-extraction method, providing simultaneous insights into the proteomic and metabolomic landscapes of S. aureus strains. These findings demonstrate the utility of proteomic and metabolomic profiling for elucidating the biological basis of antimicrobial resistance.

Glycyrrhizic Acid Nanoparticles Subside the Activity of Methicillin-Resistant Staphylococcus aureus by Suppressing PBP2a

Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA) are classified as high-risk infections that can lead to death, particularly among older individuals. Nowadays, plant nanoparticles such as glycyrrhizic acid are recognized as efficient bactericides against a wide range of bacterial strains. Recently, scientists have shown interest in plant extract nanoparticles, derived from natural sources, which can be synthesized into nanomaterials. Interestingly, glycyrrhizic acid is rich in antioxidants as well as antibacterial agents, and it exhibits no adverse effects on normal cells. In this study, glycyrrhizic acid nanoparticles (GA-NPs) were synthesized using the hydrothermal method and characterized through physicochemical techniques such as UV-visible spectrometry, DLS, zeta potential, and TEM. The antimicrobial activity of GA-NPs was investigated through various methods, including MIC assays, anti-biofilm activity assays, ATPase activity assays, and kill-time assays. The expression levels of mecA, mecR1, blaR1, and blaZ genes were measured by quantitative RT-qPCR. Additionally, the presence of the penicillin-binding protein 2a (PBP2a) protein of S. aureus and MRSA was evaluated by a Western blot assay. The results emphasized the fabrication of GA nanoparticles in spherical shapes with a diameter in the range of 40-50 nm. The data show that GA nanoparticles exhibit great bactericidal effectiveness against S. aureus and MRSA. The treatment with GA-NPs remarkably reduces the expression levels of the mecA, mecR1, blaR1, and blaZ genes. PBP2a expression in MRSA was significantly reduced after treatment with GA-NPs. Overall, this study demonstrates that glycyrrhizic acid nanoparticles have potent antibacterial activity, particularly against MRSA. This research elucidates the inhibition mechanism of glycyrrhizic acid, which involves the suppressing of PBP2a expression. This work emphasizes the importance of utilizing plant nanoparticles as effective antimicrobial agents against a broad spectrum of bacteria.

Characterisation of PVL-Positive Staphylococcus argenteus from the United Arab Emirates

Staphylococcus argenteus is a recently described staphylococcal species that is related to Staphylococcus aureus but lacks the staphyloxanthin operon. It is able to acquire both resistance markers such as the SCCmec elements and mobile genetic elements carrying virulence-associated genes from S. aureus. This includes those encoding the Panton-Valentine leukocidin (PVL), which is associated mainly with severe and/or recurrent staphylococcal skin and soft tissue infections. Here, we describe the genome sequences of two PVL-positive, mecA-negative S. argenteus sequence type (ST) 2250 isolates from the United Arab Emirates in detail. The isolates were found in a dental clinic in the United Arab Emirates (UAE). Both were sequenced using Oxford Nanopore Technology (ONT). This demonstrated the presence of temperate bacteriophages in the staphylococcal genomes, including a PVL prophage. It was essentially identical to the published sequence of phiSa2wa_st78 (GenBank NC_055048), a PVL phage from an Australian S. aureus clonal complex (CC) 88 isolate. Besides the PVL prophage, one isolate carried another prophage and the second isolate carried two additional prophages, whereby the region between these two prophages was inverted. This "flipped" region comprised about 1,083,000 bp, or more than a third of the strain's genome, and it included the PVL prophage. Prophages were induced by Mitomycin C treatment and subjected to transmission electron microscopy (TEM). This yielded, in accordance to the sequencing results, one or, respectively, two distinct populations of icosahedral phages. It also showed prolate phages which presumptively might be identified as the PVL phage. This observation highlights the significance bacteriophages have as agents of horizontal gene transfer as well as the need for monitoring emerging staphylococcal strains, especially in cosmopolitan settings such as the UAE.

Methicillin resistant Staphylococcus aureus in the United Arab Emirates: a 12-year retrospective analysis of evolving trends

Introduction

Methicillin resistant Staphylococcus aureus (MRSA) is a major contributor to the global burden of antimicrobial resistance (AMR). As MRSA continues to evolve, the need for continued surveillance to evaluate trends remains crucial. This study was carried out to assess MRSA trends in the United Arab Emirates (UAE) based on analysis of data from the national AMR surveillance program.

Methods

We carried out a 12-year (2010-2021) retrospective analysis of MRSA demographic and microbiological data collected as part of the UAE national AMR surveillance program. Participating centers from across the country routinely submit AMR surveillance data collected by trained personnel to the National AMR Surveillance Committee, where data is analyzed using a unified WHONET platform. Data on non-duplicate isolates associated with clinical infections were obtained and included in the analysis.

Results

A total of 29,414 non-duplicate MRSA isolates associated with clinical infections were reported between 2010 and 2021 (2010: n = 259; 2021: n = 4,996). MRSA represented 26.4% of all S. aureus (n = 111,623) isolates identified during the study period. In 2010, among the S. aureus isolates with reported oxacillin testing, 21.9% (n/N = 259/1,181) were identified as MRSA and this showed an increase to 33.5% (n/N = 4,996/14,925) in 2021. Although there was variation in the distribution of MRSA across the seven emirates of the country, most had an upward trend. Patient demographics reflected a male preponderance, with most being adults and from the outpatient setting. Isolates were mostly from skin and soft tissue infection specimens (72.5%; n/N = 21,335/29,414). Among the inpatients (N = 8,282), a total of 3,313 MRSA isolates were from specimens obtained ≤ 48 h after admission indicative of community acquired infection. Increasing resistance trends were observed for most antibiotics including ciprofloxacin, levofloxacin, moxifloxacin, erythromycin, gentamicin, trimethoprim-sulfamethoxazole, and quinupristin/dalfopristin. Low levels of resistance (0.0-0.8%) were sustained for linezolid except for 2015, 2016, and 2017 with 2.5, 2.6, and 2.9%, respectively. No confirmed vancomycin resistance was reported.

Conclusion

The increasing trend of MRSA isolates associated with clinical infections in the hospital and community settings is a concern. Continued monitoring including incorporation of genomic surveillance and infection control measures are recommended to stem the dissemination.

Anti-Bacterial Adhesion on Abiotic and Biotic Surfaces of the Exopolysaccharide from the Marine Bacillus licheniformis B3-15

The eradication of bacterial biofilm represents a crucial strategy to prevent a clinical problem associated with microbial persistent infection. In this study we evaluated the ability of the exopolysaccharide (EPS) B3-15, produced by the marine Bacillus licheniformis B3-15, to prevent the adhesion and biofilm formation of Pseudomonas aeruginosa ATCC 27853 and Staphylococcus aureus ATCC 29213 on polystyrene and polyvinyl chloride surfaces. The EPS was added at different times (0, 2, 4 and 8 h), corresponding to the initial, reversible and irreversible attachment, and after the biofilm development (24 or 48 h). The EPS (300 µg/mL) impaired the initial phase, preventing bacterial adhesion even when added after 2 h of incubation, but had no effects on mature biofilms. Without exerting any antibiotic activity, the antibiofilm mechanisms of the EPS were related to the modification of the (i) abiotic surface properties, (ii) cell-surface charges and hydrophobicity, and iii) cell-to-cell aggregation. The addition of EPS downregulated the expression of genes (lecA and pslA of P. aeruginosa and clfA of S. aureus) involved in the bacterial adhesion. Moreover, the EPS reduced the adhesion of P. aeruginosa (five logs-scale) and S. aureus (one log) on human nasal epithelial cells. The EPS could represent a promising tool for the prevention of biofilm-related infections.

Genetic Characteristics of Methicillin-Resistant Staphylococcus argenteus Isolates Collected in the Dutch National MRSA Surveillance from 2008 to 2021

Staphylococcus argenteus is a recently described member of the Staphylococcus aureus complex (SAC) and is associated with human disease. The frequency and intensity of infections caused by S. argenteus are similar to those of Staphylococcus aureus. S. argenteus can harbor antibiotic resistance genes and a variety of virulence factors analogous to methicillin-resistant S. aureus (MRSA). The aim of our study was to analyze a collection of isolates in the Dutch national MRSA surveillance from January 2008 until March 2021 that were nontypeable by multilocus variable-number tandem-repeat analysis (MLVA). Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-ToF MS) was used for identifying the S. argenteus isolates, and whole-genome sequencing and SeqSphere were used to generate an in-house whole-genome multilocus sequence typing (wgMLST) scheme for typing the isolates. Furthermore, the presence of antibiotic resistance genes, replicons, and virulence genes was determined. Of 52,467 isolates submitted as MRSA from January 2008 until March 2021, 64 isolates (0.12%) were nontypeable with MLVA, and 54 of them were identified with mass spectrometry (MALDI-ToF MS) as S. argenteus. It appeared in retrospect that the first methicillin-resistant S. argenteus (MRSArg) was already submitted in 2008. An in-house-developed S. argenteus wgMLST scheme revealed that S. argenteus isolates clustered in 5 genomic groups which were characterized by distinct MLST types, resistomes, plasmid replicon families, and virulence factors. All but one isolate carried the staphylococcal chromosomal cassette mec (SCCmec) type IV harboring the methicillin resistance gene mecA and represent MRSArg. Most of the isolates with SCCmec subtype IVc(2B) had a trimethoprim resistance gene, dfrG, and harbored a blaZ-carrying plasmid, and most MRSArg isolates have the immune-modulating genes scn and sak. Nine of the 47 isolates carried enterotoxin-encoding genes seg, sei, sem, seo, and seu, which might be able to cause food poisoning. In some persons there was long-term persistence of MRSArg, and there were several genetically related MRSArg isolates in people living in close proximity, suggesting direct human-human transmission. IMPORTANCE We show that MRSArg has been circulating in the Netherlands since at least 2008. Although MRSArg is distinct from MRSA, it has a comparable population structure and carries similar resistance and virulence genes. The Dutch national MRSA surveillance has been expanded to include other methicillin-resistant members of the S. aureus complex, such as S. argenteus and Staphylococcus schweitzeri.

Diversity of clonal complex 22 methicillin-resistant Staphylococcus aureus isolates in Kuwait hospitals

CC22-MRSA is a major MRSA lineage that is widely reported globally. To characterize CC22-MRSA for trends in antibiotic resistance and emergence of variants, a total of 636 CC22 isolates identified by DNA microarray in 2016 (n = 195), 2017 (n = 227) and 2018 (n = 214) were investigated further using staphylococcal protein A (spa) typing and multilocus sequence typing. The isolates belonged to 109 spa types dominated by t223 (n = 160), t032 (n = 60), t852 (n = 59), t005 (n = 56) and t309 (n = 30) and 10 sequence types (STs) dominated by ST22 (85.5%). Genotypes CC22-MRSA-IV [tst1⁺]; CC22-MRSA-IV UK-EMRSA-15/Barnim EMRSA variants, CC22-MRSA-IV [PVL⁺], CC22-MRSA-IV [tst1⁺/PVL⁺] and CC22-MRSA-IV + V constituted >50% of the isolates. An increase from 2016 to 2018 were shown in isolates belonging to spa types t223 (43 to 62), t032 (18 to 27) and t309 (10 to 15) and genotypes CC22-MRSA-IV [tst1⁺] (89 to 102), CC22-MRSA-IV + V (12 to 30) and CC22-MRSA-IV [tst1⁺/PVL⁺] (12 to 22). Ninety-nine CC22-MRSA isolates were multi-resistant to three or more antibiotic classes with 76.7% of them belonging to CC22-MRSA-IV [PVL⁺] and CC22-MRSA-IV [tst1⁺/PVL⁺]. The study revealed an ongoing domination of the CC22-MRSA-[tst1⁺] genotype and the emergence of new clones bearing SCCmec IV + V and multiply resistant variants.

Description of Staphylococcal Strains from Straw-Coloured Fruit Bat (Eidolon helvum) and Diamond Firetail (Stagonopleura guttata) and a Review of their Phylogenetic Relationships to Other Staphylococci

The phylogenetic tree of the Staphylococcus aureus complex consists of several distinct clades and the majority of human and veterinary S. aureus isolates form one large clade. In addition, two divergent clades have recently been described as separate species. One was named Staphylococcus argenteus, due to the lack of the “golden” pigment staphyloxanthin. The second one is S. schweitzeri, found in humans and animals from Central and West Africa. In late 2021, two additional species, S. roterodami and S. singaporensis, have been described from clinical samples from Southeast Asia. In the present study, isolates and their genome sequences from wild Straw-coloured fruit bats (Eidolon helvum) and a Diamond firetail (Stagonopleura guttata, an estrildid finch) kept in a German aviary are described. The isolates possessed staphyloxanthin genes and were closer related to S. argenteus and S. schweitzeri than to S. aureus. Phylogenetic analysis revealed that they were nearly identical to both, S. roterodami and S. singaporensis. We propose considering the study isolates, the recently described S. roterodami and S. singaporensis as well as some Chinese strains with MLST profiles stored in the PubMLST database as different clonal complexes within one new species. According to the principle of priority we propose it should be named S. roterodami. This species is more widespread than previously believed, being observed in West Africa, Southeast Asia and Southern China. It has a zoonotic connection to bats and has been shown to be capable of causing skin and soft tissue infections in humans. It is positive for staphyloxanthin, and it could be mis-identified as S. aureus (or S. argenteus) using routine procedures. However, it can be identified based on distinct MLST alleles, and “S. aureus” sequence types ST2470, ST3135, ST3952, ST3960, ST3961, ST3963, ST3965, ST3980, ST4014, ST4075, ST4076, ST4185, ST4326, ST4569, ST6105, ST6106, ST6107, ST6108, ST6109, ST6999 and ST7342 belong to this species.

First Report of a Methicillin-Resistant, High-Level Mupirocin-Resistant Staphylococcus argenteus

We describe the identification of a methicillin-resistant, high-level mupirocin-resistant Staphylococcus argenteus. The isolate (1801221) was characterized as t6675-ST2250-SCCmecIVc, and whole-genome sequencing revealed that the isolate possessed two plasmids. One plasmid (34,870 bp), designated p1_1801221 with rep23, harboured the mupirocin resistance (mupA) gene. The second plasmid (20,644 bp), assigned as p2_1801221 with rep5a and rep16, carried the resistance determinants for penicillin (blaZ) and cadmium (cadD). Phylogenetic analysis revealed that the isolate clustered with the European ST2250 lineage. The overall high similarity of both plasmids in S. argenteus with published DNA sequences of Staphylococcus aureus plasmids strongly suggests an interspecies transfer. The pathogenic potential, community and nosocomial spread, and acquisition of antibiotic resistance gene determinants, including the mupA gene by S. argenteus, highlight its clinical significance and the need for its correct identification.

Microbiological Contamination of the Office Environment in Dental and Medical Practice

The microbiological contamination of the environment in independent healthcare facilities such as dental and general practitioner offices was poorly studied. The aims of this study were to describe qualitatively and quantitatively the bacterial and fungal contamination in these healthcare facilities and to analyze the antibiotic resistance of bacterial pathogens identified. Microbiological samples were taken from the surfaces of waiting, consulting, and sterilization rooms and from the air of waiting room of ten dental and general practitioner offices. Six surface samples were collected in each sampled room using agar contact plates and swabs. Indoor air samples were collected in waiting rooms using a single-stage impactor. Bacteria and fungi were cultured, then counted and identified. Antibiograms were performed to test the antibiotic susceptibility of bacterial pathogens. On the surfaces, median concentrations of bacteria and fungi were 126 (range: 0–1280) and 26 (range: 0–188) CFU/100 cm², respectively. In indoor air, those concentrations were 403 (range: 118–732) and 327 (range: 32–806) CFU/m³, respectively. The main micro-organisms identified were Gram-positive cocci and filamentous fungi, including six ubiquitous genera: Micrococcus, Staphylococcus, Cladosporium, Penicillium, Aspergillus, and Alternaria. Some antibiotic-resistant bacteria were identified in general practitioner offices (penicillin- and erythromycin-resistant Staphylococcus aureus), but none in dental offices. The dental and general practitioner offices present a poor microbiological contamination with rare pathogenic micro-organisms.

Lateral Flow Immunoassay for the Detection of Panton-Valentine Leukocidin in Staphylococcus aureus From Skin and Soft Tissue Infections in the United Arab Emirates

Introduction

Panton Valentine leukocidin (PVL) is a virulence factor which is associated with methicillin sensitive and resistant Staphylococcus aureus (MSSA/MRSA) causing skin and soft tissue infections (SSTI). This study aimed to evaluate a novel lateral flow immunoassay (LFI) for PVL detection in S. aureus cultures and to describe their genotypic characterization.

Methods

The study was carried out from January-August 2020 in Dubai, United Arab Emirates. S. aureus isolates associated with SSTI were tested for PVL detection using LFI. DNA microarray-based assays were used for molecular characterization including detection of pvl genes.

Results

One-hundred thirty-five patients with a clinical diagnosis of SSTIs were recruited. Sixty-six patients received antibiotics, mostly beta lactams (n=36) and topical fusidic acid (n=15). One-hundred twenty-nine isolates (MRSA: n=43; MSSA: n=86) were tested by LFI and DNA microarrays. All 76 (58.9%) isolates which were unambiguously negative for the PVL in LFI were negative for pvl genes using the DNA microarray. All the LFI PVL positive isolates (n=53) had pvl genes detected. This translates into 100% each for sensitivity, specificity, positive and negative predictive values for the LFI. The LFI typically takes about 15 min inclusive of a 10 min incubation period. Predominant S. aureus clonal complexes (CC) were CC30 (n=18), CC22 (n=13), CC5 (n=12), CC1 (n=11), CC152 (n=8), CC15 (n=7); CC97 (n=7); CC8 and CC20 (n=6 each). Among MRSA, the proportion of pvl-positives (35/43; 81%) was higher than among MSSA (n/N=18/86; 21%). The fusidic acid resistance gene fusC was detected in 14 MRSA (33%) compared to 8 MSSA (9%). A co-carriage of fusC and pvl genes was present in 7 MRSA and in one MSSA.

Conclusion

LFI shows excellent diagnostic accuracy indices for rapid identification of PVL in MSSA/MRSA in a setting with high prevalence of pvl^+ve strains. The high occurrence of pvl and fusC genes in MRSA strains causing SSTI is of concern and needs constant surveillance.

First Report of CC5-MRSA-IV-SCCfus "Maltese Clone" in Bat Guano

Methicillin-resistant Staphylococcus aureus (MRSA) is a widespread pathogen that could cause different illnesses in both human and animals. Presence of MRSA in animals raises concerns of their capacity to act as reservoirs, particularly in wild animals. This study aimed to characterize the resistance and virulence patterns of S. aureus strains isolated from bat guano in Algeria. From March to May 2016, 98 bat guano samples from Aokas’s cave (Bejaia, Algeria) were collected. Swabs were taken for microbiological studies. Isolates were identified by Vitek^® MS system, and antibiotic susceptibility was determined by disk diffusion method. The clonal origin, virulence and antibiotic resistance profiles of S. aureus isolates were characterized by whole genome sequencing. Eleven S. aureus strains were obtained from the 98 guano samples. Seven isolates were sensitive to all antibiotics tested and four (36.3%) were resistant to penicillin G, cefoxitin and fusidic acid. The four MRSA isolates were assigned to the sequence type ST149 and related to spa type t010. These isolates harbored a SCCmecIV element and the fusidic acid resistance element Q6GD50 (fusC). They carried different virulence genes including several enterotoxins (sea, egc enterotoxin locus, sec, sel), and the toxic shock syndrome toxin (tst). Our results highlight that bat guano may constitute an important reservoir of MRSA strains.

Staphylococcus argenteus transmission among healthy Royal Marines: A molecular epidemiology case-study

Objectives During a prospective study of S. aureus carriage in Royal Marines recruits, six S. argenteus strains were identified in four recruits. As S. argenteus sepsis leads to mortality similar to S. aureus, we determined the potential for within same troop transmission, to evaluate future outbreak risk. Methods We used whole-genome sequencing to characterise S. argenteus and investigate phylogenetic relationships between isolates. Results S. argenteus strains (t5078, ST2250) were detected in 4/40 recruits in the same troop (training cohort) in weeks 1, 6 or 15 of training. No mec, tsst or LukPV genes were detected. We identified differences of 1-17 core SNPs between S. argenteus from different recruits. In two recruits, two S. argenteus strains were isolated; these could be distinguished by 2 and 15 core SNPs. Conclusions The identification of S. argenteus within a single troop from the total recruit population suggests a common source for transmission, though high number of SNPs were identified, both within-host and within-cluster. The high number of SNPs between some isolates may indicate a common source of diverse isolates or a high level of S. argenteus mutation in carriage. S. argenteus is newly recognized species; and understanding of the frequency of genetic changes during transmission and transition from asymptomatic carriage to disease is required.

The global prevalence of fusidic acid resistance in clinical isolates of Staphylococcus aureus: a systematic review and meta-analysis

BACKGROUND AND AIM

Staphylococcus aureus (S. aureus) is one of the most common pathogens causing nosocomial and community-acquired infections with high morbidity and mortality rates. Fusidic acid has been increasingly used for the treatment of infections due to methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA). The present study aimed to determine the precise prevalence of fusidic acid resistant MRSA (FRMRSA), fusidic acid resistant MSSA (FRMSSA), and total fusidic acid resistant S. aureus (FRSA) on a global scale.

METHODS

Several international databases including Medline, Embase, and the Web of Sciences were searched (2000-2020) to discern studies addressing the prevalence of FRSA, FRMRSA, and FRMSSA. STATA (version14) software was used to interpret the data.

RESULTS

Of the 1446 records identified from the databases, 215 studies fulfilled the eligibility criteria for the detection of FRSA (208 studies), FRMRSA (143 studies), and FRMSSA (71 studies). The analyses manifested that the global prevalence of FRSA, FRMRSA, and FRMSSA was 0.5%, 2.6% and 6.7%, respectively.

CONCLUSION

This meta-analysis describes an increasing incidence of FRSA, FRMSSA, and FRMRSA. These results indicate the need for prudent prescription of fusidic acid to stop or diminish the incidence of fusidic acid resistance as well as the development of strategies for monitoring the efficacy of fusidic acid use.

Low prevalence of multi-resistant bacteria in undergraduate dental students; an observational case-control multi-centre study in Europe

Objective: This study assessed the prevalence of MRSA, ESBL and VRE in students from four dental schools in Europe.

Methods: The hand, tongue and nostrils of the students who treated patients (study group) and who did not treat patients (control group) were sampled. After incubation in TSB and subculturing in the presence of 4 µg/ml oxacillin, positive cultures were identified for Staphylococcus aureus by Mannitol salt agar and agglutination tests. The presence of MRSA was confirmed by specific PCR on the species and on the SSCmec genes. ESBL and VRE were isolated using specific CHROMagar and confirmed using antibiotic sensitivity tests.

Results: Of the 879 students who participated in this study (454 students which treated patients, 425 controls) a total of 50 students (5.7%) tested positive for a multi-drug resistant bacterium (MDRB); 13 (1.5%) students tested positive for MRSA, 26 (3.0%) for ESBL and 12 (1.4%) for VRE. No statistically significant differences were found between the students who treated patients compared to the control group for any of the MDRB and study centres, excluding MRSA carriage in the Italian student population. The use of antibiotics the year before sampling, was positively associated with the presence of an MDRB (OR 2.0; 95% Confidence Interval 1.10–3.68; p = 0.02).

Conclusion: The risk for MDRB carriage and sequential transmission of MDRB for dental health care students and their patients were acceptably low.

Distribution of Virulence Factors and Resistance Determinants in Three Genotypes of Staphylococcus argenteus Clinical Isolates in Japan

Staphylococcus argenteus, a novel staphylococcal species independent of S. aureus, causes a wide spectrum of infectious diseases. As detection of this species from humans and animals has been increasingly reported worldwide, its growing virulence and drug resistance via external genetic determinants has become concerning. In this study, the prevalence and genetic characteristics of virulence factors and drug resistance determinants were investigated for 82 S. argenteus clinical isolates in Hokkaido, Japan, for a one-year period starting in August 2019. These S. argenteus isolates corresponded to 0.66% of the total number of S. aureus isolates collected in the same period. The most prevalent genotype was sequence type (ST) 2250 and staphylocoagulase (coa) genotype XId (45.1%, n = 37), followed by ST1223-coa XV (30.5%, n = 25) and ST2198-coa XIV (24.4%, n = 20). Panton-Valentine leukocidin genes (lukS-PV-lukF-PV) were identified in a single ST2250 isolate. Only ST1223 isolates had the enterotoxin gene cluster (egc-2), seb, and selw (detection rate; 100%, 60%, and 84%, respectively), while sec, sey, sel26-sel27, tst-1 were only detected in ST2250 isolates (detection rate; 10.8%, 100%, 67.6%, and 10.8%, respectively). ST2198 isolates harbored selx at a significantly higher rate (60%) than isolates of other STs. Although most of S. argenteus isolates were susceptible to antimicrobials examined, ST2198 showed higher resistance rates to penicillin, macrolides, and aminoglycosides than other STs, and it harbored various resistance genes such as blaZ, erm(C), msr(A), lnuA, and aac(6′)-Ie-aph(2″)-Ia. Only one ST2250 isolate possessed SCCmec-IVc, showing resistance to oxacillin. blaZ was the most prevalent determinant of resistance in the three STs and belonged to two plasmid groups and a chromosomal group, suggesting its diverse origin. lnu(A) in ST2198 isolates was assigned to a major cluster with various staphylococcal species. The present study indicates that the prevalence of virulence factors and drug resistance profile/determinants differ depending on the lineage (ST) of S. argenteus.

Control of Methicillin-Resistant Staphylococcus aureus Strains Associated With a Hospital Outbreak Involving Contamination From Anesthesia Equipment Using UV-C

Methicillin-resistant Staphylococcus aureus (MRSA) is considered an opportunistic pathogen in humans and is mainly associated with healthcare-associated infections (HCAIs). This bacterium colonizes the skin and mucous membranes of healthy people and causes frequent hospital outbreaks. The aim of this study was to perform molecular typing of the staphylococcal cassette chromosome mec (SCCmec) and agr loci as wells as to establish the pulsotypes and clonal complexes (CCs) for MRSA and methicillin-sensitive S. aureus (MSSA) outbreaks associated with the operating room (OR) at a pediatric hospital. Twenty-five clinical strains of S. aureus (19 MRSA and 6 MSSA strains) were recovered from the outbreak (patients, anesthesia equipment, and nasopharyngeal exudates from external service anesthesia technicians). These clinical S. aureus strains were mainly resistant to benzylpenicillin (100%) and erythromycin (84%) and were susceptible to vancomycin and nitrofurantoin. The SCCmec type II was amplified in 84% of the S. aureus strains, and the most frequent type of the agr locus was agrII, which was amplified in 72% of the strains; however, the agrI and agrIII genes were mainly detected in MSSA strains. A pulsed-field gel electrophoresis (PFGE) analysis grouped the 25 strains into 16 pulsotypes (P), the most frequent of which was P1, including 10 MRSA strains related to the anesthesia equipment, external service anesthesia technicians, and hospitalized patients. Multilocus sequence typing (MLST) identified 15 sequence types (STs) distributed in nine CCs. The most prevalent ST was ST1011, belonging to CC5, which was associated with the SCCmec type II and agrII type. We postulate that the external service anesthesia technicians were MRSA carriers and that these strains were indirectly transmitted from the contaminated anesthesia equipment that was inappropriately disinfected. Finally, the MRSA outbreak was controlled when the anesthesia equipment disinfection was improved and hand hygiene was reinforced.

Genotyping of methicillin resistant Staphylococcus aureus from the United Arab Emirates

Reports from Arabian Gulf countries have demonstrated emergence of novel methicillin resistant Staphylococcus aureus (MRSA) strains. To address the lack of data from the United Arab Emirates (UAE), genetic characterisation of MRSA identified between December 2017 and August 2019 was conducted using DNA microarray-based assays. The 625 MRSA isolates studied were grouped into 23 clonal complexes (CCs) and assigned to 103 strains. CC5, CC6, CC22 and CC30 represented 54.2% (n/N = 339/625) of isolates with other common CCs being CC1, CC8, CC772, CC361, CC80, CC88. Emergence of CC398 MRSA, CC5-MRSA-IV Sri Lanka Clone and ST5/ST225-MRSA-II, Rhine-Hesse EMRSA/New York-Japan Clone in our setting was detected. Variants of pandemic CC8-MRSA-[IVa + ACME I] (PVL+) USA300 were detected and majority of CC772 strains were CC772-MRSA-V (PVL+), “Bengal- Bay Clone”. Novel MRSA strains identified include CC5-MRSA-V (edinA+), CC5-MRSA-[VT + fusC], CC5-MRSA-IVa (tst1+), CC5-MRSA-[V/VT + cas + fusC + ccrA/B-1], CC8-MRSA-V/VT, CC22-MRSA-[IV + fusC + ccrAA/(C)], CC45-MRSA-[IV + fusC + tir], CC80-MRSA-IVa, CC121-MRSA-V/VT, CC152-MRSA-[V + fusC] (PVL+). Although several strains harboured SCC-borne fusidic acid resistance (fusC) (n = 181), erythromycin/clindamycin resistance (ermC) (n = 132) and gentamicin resistance (aacA-aphD) (n = 179) genes, none harboured vancomycin resistance genes while mupirocin resistance gene mupR (n = 2) and cfr gene (n = 1) were rare. An extensive MRSA repertoire including CCs previously unreported in the region and novel strains which probably arose locally suggest an evolving MRSA landscape.