Molecular Typing of ST239-MRSA-III From Diverse Geographic Locations and the Evolution of the SCCmec III Element During Its Intercontinental Spread

Rapid alignment-free bacteria identification via optical scattering with LEDs and YOLOv8

Rapid and accurate bacterial identification is essential for timely treatment of infections like sepsis. While traditional methods are reliable, they lack speed, and advanced molecular techniques often suffer from cost and complexity. The bacterial detection technology based on optical scattering system offers a rapid, label-free alternative but traditionally relies on complex lasers and analysis. Our enhanced approach utilizes RGB light emitting diodes (LEDs) as the light source. Three diffraction images of bacterial colonies from different LED colors are separately captured by a USB camera and combined using an image registration algorithm to enhance image sharpness. Our approach utilizes an object detection model, i.e., YOLOv8, for analysis achieving high-accuracy differentiation between bacterial strains. We demonstrate the effectiveness of this approach, achieving an average accuracy of 97% (mAP50 of 0.97), including accurate discrimination of closely related strains and the significant pathogen Staphylococcus aureus MRSA 1320. Our enhancement offers advantages in affordability, usability, and seamless integration into existing workflows, providing an alternative for rapid bacterial identification.

Sequencing a CC239-MRSA-III with a novel composite SCC mec element from Kuwait

Staphylococcus aureus CC239-MRSA-III is an ancient pandemic strain of hospital-associated, methicillin-resistant S. aureus that spread globally for decades and that still can be found in some parts of the world. In Kuwait, microarray-based surveillance identified from 2019 to 2022 a series of isolates of a hitherto unknown variant of this strain that carried a second set of recombinase genes, ccrA/B-2. To elucidate the structure of its SCCmec element, two isolates were subjected to nanopore sequencing. This revealed, in addition to ccrA/B-2, several SCC-associated genes including speG (spermidine N acetyltransferase) and a gene encoding a large "E-domain containing protein" (dubbed as edcP-SCC). This gene contained three regions consisting of multiple repeating units. In terms of sequence and structure it was similar but not identical to the biofilm-related aap gene from S. epidermidis. A review of published sequences identified edcP-SCC in eighteen genome sequences of S. aureus, S. epidermidis and S. capitis, and frequently it appears in a similar cluster of genes as in the strains sequenced herein. Isolates also carried a prophage with the adhesion factor sasX/sesI and aminoglycoside resistance genes. This is consistent with an affiliation to the "South-East Asian" Clade of CC239. The emergence of edcP-SCC and sasX-positive CC239 strain shows that, against a global trend towards community-associated MRSA, the ancient pandemic CC239 hospital strain still continues to evolve and to cause outbreaks.

The mobilome of Staphylococcus aureus from wild ungulates reveals epidemiological links at the animal-human interface

Staphylococcus aureus thrives at animal-human-environment interfaces. A large-scale work from our group indicated that antimicrobial resistance (AMR) in commensal S. aureus strains from wild ungulates is associated with agricultural land cover and livestock farming, raising the hypothesis that AMR genes in wildlife strains may originate from different hosts, namely via exchange of mobile genetic elements (MGE). In this work, we generate the largest available dataset of S. aureus draft genomes from wild ungulates in Portugal and explore their mobilome, which can determine important traits such as AMR, virulence, and host specificity, to understand MGE exchange. Core genome multi-locus sequence typing based on 98 newly generated draft genomes and 101 publicly available genomes from Portugal demonstrated that the genomic relatedness of S. aureus from wild ungulates assigned to livestock-associated sequence types (ST) is greater compared to wild ungulate isolates assigned to human-associated STs. Screening of host specificity determinants disclosed the unexpected presence in wildlife of the immune evasion cluster encoded in φSa3 prophage, described as a human-specific virulence determinant. Additionally, two plasmids, pAVX and pETB, previously associated with avian species and humans, respectively, and the Tn553 transposon were detected. Both pETB and Tn553 encode penicillin resistance through blaZ. Pangenome analysis of wild ungulate isolates shows a core genome fraction of 2133 genes, with isolates assigned to ST72 and ST3224 being distinguished from the remaining by MGEs, although there is no reported role of these in adaptation to wildlife. AMR related gene clusters found in the shell genome are directly linked to resistance against penicillin, macrolides, fosfomycin, and aminoglycosides, and they represent mobile ARGs. Altogether, our findings support epidemiological interactions of human and non-human hosts at interfaces, with MGE exchange, including AMR determinants, associated with putative indirect movements of S. aureus among human and wildlife hosts that might be bridged by livestock.

Molecular characterization of typing and subtyping of Staphylococcal cassette chromosome SCCmec types I to V in methicillin-resistant Staphylococcus aureus from clinical isolates from COVID-19 patients

Background and Objectives

Methicillin resistance is acquired by the bacterium due to mecA gene which codes for penicillin-binding protein (PBP2a) having low affinity for β-lactam antibiotics. mecA gene is located on a mobile genetic element called staphylococcal cassette chromosome mec (SCCmec). SCCmec genomic island comprises two site-specific recombinase genes namely ccrA and ccrB [cassette chromosome recombinase] accountable for mobility. Currently, SCCmec elements are classified into types I, II, III, IV and V based on the nature of the mec and ccr gene complexes and are further classified into subtypes according to variances in their J region DNA. SSCmec type IV has been found in community-acquired isolates with various genetic backgrounds. The present study was undertaken to categorize the types of SCCmec types and subtypes I, II, III, IVa, b, c, d, and V and PVL genes among clinical MRSA isolates from COVID-19 confirmed cases.

Materials and Methods

Based on the Microbiological and Molecular (mecA gene PCR amplification) confirmation of MRSA isolated from 500 MRSA SCCmec clinical samples, 144 cultures were selected for multiplex analysis. The multiplex PCR method developed by Zhang et al. was adapted with some experimental alterations to determine the specific type of these isolates.

Results

Of the total 500 MRSA, 144 MRSA (60 were CA-MRSA and 84 were HA-MRSA) were selected for characterization of novel multiplex PCR assay for SSCmec Types I to V in MRSA. Molecular characterization of multiplex PCR analysis revealed results compare to the phenotypic results. Of the 60 CA-MRSA; in 56 MRSA strains type IVa was found and significantly defined as CA-MRSA while 4 strains showed mixed gens subtypes. Type II, III, IA, and V were present in overall 84 HA-MRSA. Molecular subtyping was significantly correlated to define molecularly as CA-MRSA and HA-MRSA however 15 (10%) strains showed mixed genes which indicates the alarming finding of changing epidemiology of CA-MRSA and HA-MRSA as well.

Conclusion

We have all witnessed of COVID-19 pandemic, and its mortality was mostly associated with co-morbid conditions and secondary infections of MDR pathogens. Rapid detections of causative agents of these superbugs with their changing epidemiology by investing in typing and subtyping clones are obligatory. We have described an assay designed for targeting SSCmec types and subtypes I, II, III, IVa,V according to the current updated SCCmec typing system. Changing patterns of molecular epidemiology has been observed by this newly described assay.

Whole genome characterization of methicillin resistant Staphylococcus aureus in an Egyptian Tertiary Care Hospital

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is a significant healthcare-associated (HA-MRSA) pathogen due to its increased morbidity and mortality rates. There is a paucity of data regarding MRSA clones circulating in the Middle East in the literature, especially from Egypt. We aimed to identify the pattern of resistance and virulence in the propagating clones using NGS technologies for the whole genome sequence.

METHODS

From an 18-month surveillance program for MRSA-positive patients, 18 MRSA isolates from surgical healthcare associated infections were selected. The Vitek2 system was used to assess antimicrobial susceptibility. The whole genome sequencing was performed using the NovaSeq6000. The reads were mapped to the reference genome (Staphylococcus_aureus_ATCC_BAA_1680), used for variant calling, screened for virulence/resistance genes, and typed using multi-locus sequence typing and spa typing. Correlation between demographic and clinical data and molecular findings were performed.

RESULTS

All the MRSA isolates were highly resistant to tetracycline followed by gentamicin (61%) and highly susceptible to trimethoprim/sulfamethoxazole. Most of the isolates showed a high virulence profile. ST239 was the predominant sequence type (6/18), while t037 was the predominant spa type (7/18). Five isolates shared the same ST239 and spa t037. ST1535, an emerging MRSA strain, was the second most prevalent in our study. One isolate showed a unique pattern of a high abundance of resistance and virulence genes.

CONCLUSION

WGS elucidated the resistance and virulence profiles of MRSA isolated from clinical samples of HAI patients with high-resolution tracking of clones predominant in our healthcare facility.

Clonal Complexes Distribution of Staphylococcus aureus Isolates from Clinical Samples from the Caribbean Islands

The aim of this study was to comprehensively characterise S. aureus from the Caribbean Islands of Trinidad and Tobago, and Jamaica. A total of 101 S. aureus/argenteus isolates were collected in 2020, mainly from patients with skin and soft tissue infections. They were characterised by DNA microarray allowing the detection of ca. 170 target genes and assignment to clonal complexes (CC)s and strains. In addition, the in vitro production of Panton-Valentine leukocidin (PVL) was examined by an experimental lateral flow assay. Two isolates were identified as S. argenteus, CC2596. The remaining S. aureus isolates were assigned to 21 CCs. The PVL rate among methicillin-susceptible S. aureus (MSSA) isolates was high (38/101), and 37 of the 38 genotypically positive isolates also yielded positive lateral flow results. The isolate that did not produce PVL was genome-sequenced, and it was shown to have a frameshift mutation in agrC. The high rate of PVL genes can be attributed to the presence of a known local CC8-MSSA clone in Trinidad and Tobago (n = 12) and to CC152-MSSA (n = 15). In contrast to earlier surveys, the USA300 clone was not found, although one MSSA isolate carried the ACME element, probably being a mecA-deficient derivative of this strain. Ten isolates, all from Trinidad and Tobago, were identified as MRSA. The pandemic ST239-MRSA-III strain was still common (n = 7), but five isolates showed a composite SCCmec element not observed elsewhere. Three isolates were sequenced. That showed a group of genes (among others, speG, crzC, and ccrA/B-4) to be linked to its SCC element, as previously found in some CC5- and CC8-MRSA, as well as in S. epidermidis. The other three MRSA belonged to CC22, CC72, and CC88, indicating epidemiological connections to Africa and the Middle East.

Clonal diversity of Staphylococcus aureus isolates in clinical specimens from selected health facilities in Ethiopia

Staphylococcus aureus is among the top three causative agents of nosocomial infection in Ethiopia. The majority of studies in Ethiopia have focused on the epidemiology of S. aureus in hospital settings, with limited molecular genotyping results. Molecular characterization of S. aureus is essential for identification of strains, and contributes to the control and prevention of S. aureus infection. The aim of the current study was to determine the molecular epidemiology of methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) isolates recovered from clinical specimens in Ethiopia. A total of 161 MSSA and 9 MRSA isolates were characterized using pulsed-field gel electrophoresis (PFGE) and staphylococcal protein A (spa) typing. Based on the PFGE analysis, MSSA isolates were grouped into eight pulso-types groups (from A to I), while MRSA isolates clustered into three (A, B and C) pulso-types with more than 80% similarity. The spa typing analysis showed diversity of S. aureus with 56 distinct spa types. Spa type t355 was most prevalent (56/170, 32.9%), while eleven new spa types were detected including t20038, t20039, and t20042. The identified spa types were clustered into 15 spa-clonal complexes (spa-CCs) using BURP analysis; novel/unknown spa types were further subjected to MLST analysis. The majority of isolates belonged to spa-CC 152 (62/170, 36.4%), followed by spa-CC 121 (19/170, 11.2%), and spa-CC 005 (18 /170, 10.6%). Of the nine MRSA isolates, 2 (22.2%) were spa-CC 239 with staphylococcal cassette chromosome (SCC)mec III. These findings highlight the diversity of S. aureus strains in Ethiopia, as well as the presence of potentially epidemic strains circulating in the country necessitating further characterization of S. aureus for antimicrobial resistance detection and infection prevention purposes.

Characterisation of Methicillin-Resistant Staphylococcus aureus from Alexandria, Egypt

The present study aims to characterise clinical MRSA isolates from a tertiary care centre in Egypt's second-largest city, Alexandria. Thirty isolates collected in 2020 were genotypically characterised by microarray to detect their resistance and virulence genes and assign them to clonal complexes (CC) and strains. Isolates belonged to 11 different CCs and 14 different strains. CC15-MRSA-[V+fus] (n = 6), CC1-MRSA-[V+fus+tir+ccrA/B-1] (PVL+) (n = 5) as well as CC1-MRSA-[V+fus+tir+ccrA/B-1] and CC1153-MRSA-[V+fus] (PVL+) (both with n = 3) were the most common strains. Most isolates (83%) harboured variant or composite SCCmec V or VI elements that included the fusidic acid resistance gene fusC. The SCCmec [V+fus+tir+ccrA/B-1] element of one of the CC1 isolates was sequenced, revealing a presence not only of fusC but also of blaZ, aacA-aphD and other resistance genes. PVL genes were also common (40%). The hospital-acquired MRSA CC239-III strain was only found twice. A comparison to data from a study on strains collected in 2015 (Montelongo et al., 2022) showed an increase in fusC and PVL carriage and a decreasing prevalence of the CC239 strain. These observations indicate a diffusion of community-acquired strains into hospital settings. The beta-lactam use in hospitals and the widespread fusidic acid consumption in the community might pose a selective pressure that favours MRSA strains with composite SCCmec elements comprising mecA and fusC. This is an unsettling trend, but more MRSA typing data from Egypt are required.

In Silico Genome-Scale Analysis of Molecular Mechanisms Contributing to the Development of a Persistent Infection with Methicillin-Resistant Staphylococcus aureus (MRSA) ST239

The increasing frequency of isolation of methicillin-resistant Staphylococcus aureus (MRSA) limits the chances for the effective antibacterial therapy of staphylococcal diseases and results in the development of persistent infection such as bacteremia and osteomyelitis. The aim of this study was to identify features of the MRSA_ST239 0943-1505-2016 (SA943) genome that contribute to the formation of both acute and chronic musculoskeletal infections. The analysis was performed using comparative genomics data of the dominant epidemic S. aureus lineages, namely ST1, ST8, ST30, ST36, and ST239. The SA943 genome encodes proteins that provide resistance to the host's immune system, suppress immunological memory, and form biofilms. The molecular mechanisms of adaptation responsible for the development of persistent infection were as follows: amino acid substitution in PBP2 and PBP2a, providing resistance to ceftaroline; loss of a large part of prophage DNA and restoration of the nucleotide sequence of beta-hemolysin, that greatly facilitates the escape of phagocytosed bacteria from the phagosome and formation of biofilms; dysfunction of the AgrA system due to the presence of psm-mec and several amino acid substitutions in the AgrC; partial deletion of the nucleotide sequence in genomic island vSAβ resulting in the loss of two proteases of Spl-operon; and deletion of SD repeats in the SdrE amino acid sequence.

Genomic analysis of methicillin-resistant Staphylococcus aureus clonal complex 239 isolated from Danish patients with and without an international travel history

Introduction

International travel has been a major determinant for the introduction of pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) into naïve geographic areas. MRSA clonal complex 239 (CC239) is a highly virulent clone that is predominant in Asia. The objective of this study was to determine the geographic origin of MRSA CC239 isolates recovered from Danish cases with or without a history of international travel during 2004-2016.

Materials and methods

Human MRSA isolates with spa types t030 and t037 (n = 60) were obtained from the National Reference Laboratory for Antimicrobial Resistance. For each case, the following data were collected from notification forms: sex, age, isolation year, specimen source (screening swab or clinical sample), infection type, and international travel history. All isolates were whole-genome sequenced, and a comparative genome and phylogenetic analysis was performed.

Results

The majority of isolates originated from skin and soft tissue (SST) infections and screening swabs. In 31 out of 60 cases reported international travel to different parts of the world. Fifty-four isolates belonged to CC239, including sequence type 239 (ST239) (n = 43), ST241 (n = 5), ST4377 (n = 2), ST4378 (n = 1), ST1465 (n = 1), ST343 (n = 1), and ST592 (n = 1). The majority of the CC239 MRSA isolates (40/54) belonged to well-known geographic clades, including the Asian (n = 12), Serbian (n = 11), South American (n = 2), and Turkish (n = 15). Most MRSA ST239 isolates belonging to the highly virulent Asian clade carried sasX and were recovered from individuals who had travelled to Asia, Africa and the Middle East.

Conclusion

Our data reveal multiple introductions of MRSA CC239 into Denmark through international travel, which highlights the importance of continued genomic surveillance of MRSA in persons returning from international travel to areas where MRSA is endemic.

Genetic Diversity among Methicillin-Resistant Staphylococcus aureus in Malaysia (2002-2020)

1.

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is a common organism seen in both healthcare-associated and community-associated infections worldwide and in Malaysia over the past two decades. The aim of this review is to provide a firsthand documentation of all MRSA strains prevalent in the Malaysian population from 2002 to present and briefly describe the changing patterns. 2.

METHODS

Electronic and manual intensive literature searches were conducted between 2002 and 2020, addressing issues directly related to patients and published in the English language were selected. 3.

RESULTS

The literature search retrieved a total of 2217 articles and abstracts of 27 articles. The search yielded a total of 24 articles on genotyping of MRSA in Malaysia. The study found that MRSA strains were mostly genetically related and resulted in the predominant MRSA clones that caused active infections. Thirty-six different sequence types (ST) were recorded. The highest rates of STs detected were ST239 (52.6%), ST1 (47.4%), and ST22 (42.1%). The majority of studies showed that both SCCmec types III and IV were the most common SCCm type in Malaysia, followed by SCCmec type V (57.9%). 4.

CONCLUSIONS

Both Brazilian (ST 239 IIIA) and Hungarian (ST 239-III) MRSA strains were detected in Malaysia. PFGE remains the best method for comparing MRSA strains. However, whole-genome sequencing has a promising chance to replace PFGE in the future.

Comparison of Different Label-Free Raman Spectroscopy Approaches for the Discrimination of Clinical MRSA and MSSA Isolates

Methicillin-resistant Staphylococcus aureus (MRSA) is classified as one of the priority pathogens that threaten human health. Resistance detection with conventional microbiological methods takes several days, forcing physicians to administer empirical antimicrobial treatment that is not always appropriate. A need exists for a rapid, accurate, and cost-effective method that allows targeted antimicrobial therapy in limited time. In this pilot study, we investigate the efficacy of three different label-free Raman spectroscopic approaches to differentiate methicillin-resistant and -susceptible clinical isolates of S. aureus (MSSA). Single-cell analysis using 532 nm excitation was shown to be the most suitable approach since it captures information on the overall biochemical composition of the bacteria, predicting 87.5% of the strains correctly. UV resonance Raman microspectroscopy provided a balanced accuracy of 62.5% and was not sensitive enough in discriminating MRSA from MSSA. Excitation of 785 nm directly on the petri dish provided a balanced accuracy of 87.5%. However, the difference between the strains was derived from the dominant staphyloxanthin bands in the MRSA, a cell component not associated with the presence of methicillin resistance. This is the first step toward the development of label-free Raman spectroscopy for the discrimination of MRSA and MSSA using single-cell analysis with 532 nm excitation. IMPORTANCE Label-free Raman spectra capture the high chemical complexity of bacterial cells. Many different Raman approaches have been developed using different excitation wavelength and cell analysis methods. This study highlights the major importance of selecting the most suitable Raman approach, capable of providing spectral features that can be associated with the cell mechanism under investigation. It is shown that the approach of choice for differentiating MRSA from MSSA should be single-cell analysis with 532 nm excitation since it captures the difference in the overall biochemical composition. These results should be taken into consideration in future studies aiming for the development of label-free Raman spectroscopy as a clinical analytical tool for antimicrobial resistance determination.

Whole-Genome Sequencing of Staphylococcus aureus and Staphylococcus haemolyticus Clinical Isolates from Egypt

Infections caused by antibiotic-resistant Staphylococcus are a global concern. This is true in the Middle East, where increasingly resistant Staphylococcus aureus and Staphylococcus haemolyticus strains have been detected. While extensive surveys have revealed the prevalence of infections caused by antibiotic-resistant staphylococci in Europe, Asia, and North America, the population structure of antibiotic-resistant staphylococci recovered from patients and clinical settings in Egypt remains uncharacterized. We performed whole-genome sequencing of 56 S. aureus and 10 S. haemolyticus isolates from Alexandria Main University Hospital; 46 of the S. aureus genomes and all 10 of the S. haemolyticus genomes carry mecA, which confers methicillin resistance. Supplemented with additional publicly available genomes from the other parts of the Middle East (34 S. aureus and 6 S. haemolyticus), we present the largest genomic study to date of staphylococcal isolates from the Middle East. These genomes include 20 S. aureus multilocus sequence types (MLST), including 3 new ones. They also include 9 S. haemolyticus MLSTs, including 1 new one. Phylogenomic analyses of each species' core genome largely mirrored those of the MLSTs, irrespective of geographical origin. The hospital-acquired spa t037/ST239-SCCmec III/MLST CC8 clone represented the largest clade, comprising 22% of the S. aureus isolates. Like S. aureus genome surveys of other regions, these isolates from the Middle East have an open pangenome, a strong indicator of gene exchange of virulence factors and antibiotic resistance genes with other reservoirs. Our genome analyses will inform antibiotic stewardship and infection control plans in the Middle East. IMPORTANCE Staphylococci are understudied despite their prevalence within the Middle East. Methicillin-resistant Staphylococcus aureus (MRSA) is endemic to hospitals in Egypt, as are other antibiotic-resistant strains of S. aureus and S. haemolyticus. To provide insight into the strains circulating in Egypt, we performed whole-genome sequencing of 56 S. aureus and 10 S. haemolyticus isolates from Alexandria Main University Hospital. Through analysis of these genomes, as well as all available S. aureus and S. haemolyticus genomes from the Middle East (n = 40), we were able to produce a picture of the diversity in this region more complete than those afforded by traditional molecular typing strategies. For example, we identified 4 new MLSTs. Most strains harbored genes associated with multidrug resistance, toxin production, biofilm formation, and immune evasion. These data provide invaluable insight for future antibiotic stewardship and infection control within the Middle East.

Spa diversity and genetic characterization of t127 methicillin-resistant Staphylococcus aureus in a tertiary Greek hospital

Introduction

Methicillin-resistant Staphy lococcus aureus (MRSA) causes severe community and hospital acquired infections. Identification of staphylococcal cassette chromosome mec (SCCmec), multilocus-sequence typing, and sequencing of S. aureus protein A (spa) gene are used for MRSA typing. The aim was to investigate the spa types of MRSA isolates in a tertiary hospital in Greece and analyse the whole genome sequences of two t127 MRSA isolates.

Methods

Totally, 39 MRSA isolates collected from July 2019 to June 2020 in "Georgios Gennimatas" General Hospital of Thessaloniki, Greece, were included in the study. Identification and antimicrobial susceptibility testing were performed using VITEK II automated system, and spa typing was performed. A minimum spanning tree was used to display the spa type frequencies and the genetic distances among them. Two t127-MRSA isolates (IM-MRSA and PD-MRSA) were selected for WGS.

Results

Six isolates (15.4%) were resistant to mupirocin, 18 (46.2%) to fusidic acid, three (7.7%) to vancomycin and two (5.1%) to teicoplanin. Twenty-two different spa types were detected, with t002, t003, and t422 being the most frequent (5/39, 12.8% each), followed by t1994 (4/39, 10.3%). The isolates presented high genetic diversity and, taking into account the time between hospital admission and sampling, intrahospital spread did not occur. Even the two t127 isolates were assigned to different sequence types, ST9-XII-t127 and ST1-IVa-t127. Plasmids and genes conferring antimicrobial resistance and virulence were also identified.

Conclusions

Various spa types were identified and together with the information about the time between hospital admission and sampling supports polyclonal MRSA spread in the hospital excluding a nosocomial infection. WGS provides a more detailed analysis distinguishing even the isolates belonging to the same spa type.

Clonal Diversity and Epidemiological Characteristics of ST239-MRSA Strains

Methicillin-resistant Staphylococcus aureus (MRSA) is a major pathogen associated with severe morbidity and mortality and poses a significant threat to public health worldwide. The genetic diversity based on sequence types of MRSA strains was illustrated in previous studies; meanwhile, the diversity along with the predominant sequence type, especially in Egypt, remains unknown. The purpose of the current study was to determine the diversity of the predominant MRSA clone ST239-MRSA (n = 50) isolated from different hosts and clinical samples and to illustrate the correlation between the resistance patterns, toxin genes, and the genetic background in Port-said and El-Sharkia Governorates, Egypt. The ST239-MRSA clone was analyzed by phenotypic antibiotyping and various genotypic assays comprising SCCmec, agr, spa, coa, and coa-RFLP in addition to toxin gene profiles. Most of the analyzed strains (40/50, 80%) were multidrug resistant (MDR), belonged to SCCmec-III, agr-I, and coa genotype I, and harbored sea and pvl genes. A negative correlation between the toxin gene profiles and antimicrobial resistance was recorded. Meanwhile, the correlation between the toxin gene profiles and the genetic background was not observed in this study. Although ST239-MRSA strains belonged to a single sequence type, they exhibited a high degree of phenotypic and genotypic diversity, indicating weak clonality and adaptability. With such diversity, it is assumed that these strains may have undergone different evolutionary processes during transmission events among and/or within a single host or tissue niche.

Molecular characterization of methicillin-resistant Staphylococcus aureus genotype ST764-SCCmec type II in Thailand

Methicillin-resistant Staphylococcus aureus (MRSA) is a significant causative agent of hospital-acquired infections. We characterized MRSA isolated from August 2012 to July 2015 from Thammasat University Hospital. Genotypic characterization of MRSA SCCmec type II and III isolates were scrutinized by whole genome sequencing (WGS). The WGS data revealed that the MRSA SCCmec type II isolates belonged to ST764 previously reported mainly in Japan. All of tested isolates contained ACME Type II′, SaPIn2, SaPIn3, seb, interrupted SA1320, and had a virulence gene profile similar to Japan MRSA ST764. Rigorous surveillance of MRSA strains is imperative in Thailand to arrest its potential spread.

Methicillin-resistant Staphylococcus aureus in China: a multicentre longitudinal study and whole-genome sequencing

The aim of this study was to investigate the genomic epidemiology of MRSA in China to identify predominant lineages and their associated genomic and phenotypic characteristics. In this study, we conducted whole-genome sequencing on 565 MRSA isolates from 7 provinces and municipalities of China between 2014 and 2020. MRSA isolates were subjected to MLST, spa typing, SCCmec typing, analysis of virulence determinants and antimicrobial susceptibility testing. Among 565 MRSA isolates tested, clonal complex (CC) 59 (31.2%), CC5 (23.4%) and CC8 (13.63%) were the major lineages, and the clonal structure was dominated by ST59-t437-IV (14.9%), ST239-t030-III (6.4%) and ST5-t2460-II (6.0%), respectively. Of note, CC8, the predominant lineage in 2014–2015, was replaced by CC59 after 2016. Interestingly, the extension and unstable structure of the CC5 population was observed, with ST5-t311-II, ST764-t1084-II, ST5-t2460-II and ST764-t002-II existing complex competition. Further analysis revealed that virulence determinant profiles and antibiograms were closely associated with the clonal lineage. The CC59 MRSA was less resistant to most tested antimicrobials and carried fewer resistance determinants. But rifampicin resistance and mupirocin resistance were closely linked with CC8 and CC5, respectively. MRSA isolates conservatively carried multiple virulence genes involved in various functions. PVL encoding genes were more common in ST338, CC30, CC398, ST8 and CC22, while tsst-1 was associated with ST5. In conclusion, the community-associated CC59-ST59-t437-IV lineage was predominant in China, with diverse clonal isolates alternately circulating in various geographical locations. Our study highlights the need for MRSA surveillance in China to monitor changes in MRSA epidemiology.

shsA: A novel orthologous of sasX/sesI virulence genes is detected in Staphylococcus haemolyticus Brazilian strains

The surface protein SasX, has a key role in methicillin-resistant Staphylococcus aureus (MRSA) colonization and pathogenesis, and has been associated with the epidemic success of some MRSA clones. To date, only one SasX homologous protein, named SesI, has been described in Staphylococcus epidermidis. In this work, we analyze the occurrence of the sasX gene and its genetic environment in Staphylococcus haemolyticus S. haemolyticus clinical strains (n = 62) were screened for the presence of the sasX gene and its carrier, the prophage Φ SPβ-like. A deep characterization was done in one strain (MD43), through which we determined the complete nucleotide sequence for the S. haemolitycus sasX-like gene. Whole genome sequencing of strain MD43 was performed, and the gene, termed here because of its unique attributes, shsA, was mapped to the Φ SPβ-like prophage sequence. The shsA gene was detected in 33 out of 62 strains showing an average identity of 92 and 96% with the sasX and sesI genes and at the amino acid level, 88% identity with SasX and 92% identity with SesI. The ~124Kb Φ SPβ-like prophage sequence showed a largely intact prophage compared to its counterpart in S. epidermidis strain RP62A, including the sesI insertion site. In conclusion, we identified a new sasX ortholog in S. haemolyticus (shsA). Its horizontal spread from this reservoir could represent an emergent threat in healthcare facilities since so far, no S. aureus sasX⁺ strains have been reported in Brazil.

Evolutionary Processes Driving the Rise and Fall of Staphylococcus aureus ST239, a Dominant Hybrid Pathogen

Selection plays a key role in the spread of antibiotic resistance, but the evolutionary drivers of clinically important resistant strains remain poorly understood. Here, we use genomic analyses and competition experiments to study Staphylococcus aureus ST239, a prominent MRSA strain that is thought to have been formed by large-scale recombination between ST8 and ST30. Genomic analyses allowed us to refine the hybrid model for the origin of ST239 and to date the origin of ST239 to 1920 to 1945, which predates the clinical introduction of methicillin in 1959. Although purifying selection has dominated the evolution of ST239, parallel evolution has occurred in genes involved in antibiotic resistance and virulence, suggesting that ST239 has evolved toward an increasingly pathogenic lifestyle. Crucially, ST239 isolates have low competitive fitness relative to both ST8 and ST30 isolates, supporting the idea that fitness costs have driven the demise of this once-dominant pathogen strain.

Emergence of Methicillin-Resistant Staphylococcus aureus ST239/241 SCCmec-III Mercury in Eastern Algeria

In this paper, we investigate the epidemiology of infections-associated Staphylococcusaureus (S. aureus) from the Medical Intensive Care Unit (MICU) at University Hospital Center of Constantine (UHCC) in Algeria, with a special emphasis on methicillin-resistant strains (MRSA) revealed by cefoxitin disks (30 μg), then confirmed by penicillin-binding protein (PBP2a) agglutination and real-time polymerase chain reaction (RT-PCR) targeting mecA and mecC genes. Staphylococcal Cassette Chromosome mec (SCCmec type), staphylococcal protein A (spa-type), multilocus sequence type (MLST), Panton-Valentine Leucocidin (PVL), and toxic shock syndrome toxin-1 (TSST-1) were further investigated in all isolates, and whole genome sequencing was performed for a selected subset of three hospital-acquired MRSA (HA-MRSA) isolates. A measurement of 80% out of the 50 S. aureus isolates were identified as HA-MRSA harbouring the mecA gene, and 72.5% of them were multidrug resistant (MDR). Twelve STs, four different SCCmec cassettes, fourteen spa types, ten isolates Panton-Valentine Leukocidin (PVL)-positive, and three isolates TSST-1 were identified. Interestingly, there was a high prevalence (n = 29; 72.5%) of a worrisome emerging clone: the HA-MRSA ST239/241 SCCmec-III mercury with PVL negative, resistant to β-lactams, aminoglycosides, quinolones, and tetracyclines. Other clones of HA-MRSA isolates were also identified, including PVL-positive ST80 SCCmec-IV/SCCmec-unknown (22.5%), ST34 SCCmec-V with TSST-1 positive (2.5%), and PVL-negative ST72 SCCmec-II (2.5%). Genome analysis enables us to describe the first detection of both PVL-negative HA-MRSA ST239/241 SCCmec-III mercury carrying ccrC, as well as SCCmec-V cassette, which dramatically changes the epidemiology of S. aureus infections in one of the hospitals in eastern Algeria.

Clonal Diversity and Molecular Characteristics of Methicillin-Susceptible and -Resistant Staphylococcus aureus from Pediatric Patients in Myanmar

The spread of multidrug-resistant and virulent Staphylococcus aureus among children is a public health concern, but the actual conditions in Myanmar have not been characterized. In this study, a total of 244 clinical isolates of S. aureus collected from pediatric patients in Yangon Children's Hospital during a 1-year period were analyzed for their drug resistance and genetic features. Methicillin-resistant S. aureus (MRSA) accounted for 19.7% of isolates associated with staphylococcal cassette chromosome mec (SCCmec) type III, IV, or V. Panton-Valentine leukocidin (PVL) genes were detected in 61.5% of all isolates, with a significantly higher prevalence in methicillin-susceptible S. aureus (MSSA; 67.9%) than in MRSA (35.4%) isolates. Sequence type (ST) 239/SCCmec-III was the most common MRSA clone lacking PVL genes, while PVL-positive MRSA belonged to mostly ST361/SCCmec-V and ST772/SCCmec-V. Among MSSA isolates, ST121, ST2990, ST88, and ST1930 were dominant, harboring mostly PVL genes. ST239 MRSA isolates exhibited the highest resistance rates to antimicrobials, and quinolone resistance was found in the dominant MRSA clones (ST239, ST361, and ST772) and some MSSA lineages. The present study revealed the prevalence and clonal diversity of MRSA/MSSA in children in Myanmar in relation to drug resistance and virulence determinants.

Exploring the evolution and epidemiology of European CC1-MRSA-IV: tracking a multidrug-resistant community-associated meticillin-resistant Staphylococcus aureus clone

This study investigated the evolution and epidemiology of the community-associated and multidrug-resistant Staphylococcus aureus clone European CC1-MRSA-IV. Whole-genome sequences were obtained for 194 European CC1-MRSA-IV isolates (189 of human and 5 of animal origin) from 12 countries, and 10 meticillin-susceptible precursors (from North-Eastern Romania; all of human origin) of the clone. Phylogenetic analysis was performed using a maximum-likelihood approach, a time-measured phylogeny was reconstructed using Bayesian analysis, and in silico microarray genotyping was performed to identify resistance, virulence-associated and SCCmec (staphylococcal cassette chromosome mec) genes. Isolates were typically sequence type 1 (190/204) and spa type t127 (183/204). Bayesian analysis indicated that European CC1-MRSA-IV emerged in approximately 1995 before undergoing rapid expansion in the late 1990s and 2000s, while spreading throughout Europe and into the Middle East. Phylogenetic analysis revealed an unstructured meticillin-resistant S. aureus (MRSA) population, lacking significant geographical or temporal clusters. The MRSA were genotypically multidrug-resistant, consistently encoded seh, and intermittently (34/194) encoded an undisrupted hlb gene with concomitant absence of the lysogenic phage-encoded genes sak and scn. All MRSA also harboured a characteristic ~5350 nt insertion in SCCmec adjacent to orfX. Detailed demographic data from Denmark showed that there, the clone is typically (25/35) found in the community, and often (10/35) among individuals with links to South-Eastern Europe. This study elucidated the evolution and epidemiology of European CC1-MRSA-IV, which emerged from a meticillin-susceptible lineage prevalent in North-Eastern Romania before disseminating rapidly throughout Europe.

Genetic characterization of two methicillin-resistant Staphylococcus aureus spa type t127 strains isolated from workers in the dairy production chain in Greece

Methicillin-resistant Staphylococcus aureus (MRSA) constitutes a constant threat for the public health. Aim of the present study was to analyse the whole genome sequences of two MRSA strains belonging to Staphylococcus protein A (spa) type t127 isolated from humans working in two distantly located dairy production farms in Greece.MRSA strains were isolated from the nasal cavity of a food handler in a milk industry in Epirus, northwestern Greece (E-MRSA), and a person working in a cattle farm in Thrace, northeastern Greece (T-MRSA). Whole genome sequences taken using next generation sequencing were analysed for resistance and virulence genes applying various bioinformatic tools.Both isolates were assigned to ST1-IVa-t127 type, and they were transferring genes conferring resistance to tetracycline, β-lactams, and aminoglycosides; T-MRSA was carrying additional genes leading to macrolide, lincosamide and streptogramin B (MLSB) resistance. Both isolates were carrying three plasmid replicon types, rep5, rep7 and rep16, while T-MRSA harboured also rep10 and rep15. E-MRSA carried scn and sak genes which were absent from T-MRSA.In conclusion, the genetic characterization of two unrelated ST1-IVa-t127 MRSA strains isolated from humans in close contact with livestock in Greece can be used as basis for further epidemiological and evolutionary studies.

Staphylococcus aureus ST228 and ST239 as models for expression studies of diverse markers during osteoblast infection and persistence

The ability of S. aureus to infect bone and osteoblasts is correlated with its incredible virulence armamentarium that can mediate the invasion/internalization process, cytotoxicity, membrane damage, and intracellular persistence. We comparatively analyzed the interaction, persistence, and modulation of expression of selected genes and cell viability in an ex vivo model using human MG‐63 osteoblasts of two previously studied and well‐characterized S. aureus clinical strains belonging to the ST239‐SCCmecIII‐t037 and ST228‐SCCmecI‐t041 clones at 3 h and 24 h post‐infection (p.i). S. aureus ATCC12598 ST30‐t076 was used as a control strain. Using imaging flow cytometry (IFC), we found that these strains invaded and persisted in MG‐63 osteoblasts to different extents. The invasion was evaluated at 3 h p.i and persistence at 24 h p.i., in particular: ATCC12598 internalized in 70% and persisted in 50% of MG‐63 cells; ST239‐SCCmecIII internalized in 50% and persisted in 45% of MG‐63 cells; and ST228‐SCCmecI internalized in 30% and persisted in 20% of MG‐63 cells. During the infection period, ST239‐III exerted significant cytotoxic activity resulting from overexpression of hla and psmA and increased expression of the genes involved in adhesion, probably due to the release and re‐entry of bacteria inside MG‐63 cells at 24 h p.i. The lower invasiveness of ST228‐I was also associated with non‐cytotoxic activity inside osteoblasts. This clone was unable to activate sufficient cellular reaction and succumbed inside MG‐63 cells. Our findings support the idea of considering new strategies, based on a translational approach—eukaryotic host–pathogen interaction (EHPI)—and to be applied on a large scale, to predict S. aureus /osteoblast interaction and treat bone infections. Such strategies rely on the study of the genetic and biochemical basis of both pathogen and host.

Different Modulatory Effects of Four Methicillin-Resistant Staphylococcus aureus Clones on MG-63 Osteoblast-Like Cells

Staphylococcus aureus is a Gram-positive bacterium responsible for a variety of mild to life-threatening infections including bone infections such as osteomyelitis. This bacterium is able to invade and persist within non-professional phagocytic cells such as osteoblasts. In the present study, four different S. aureus strains, namely, 2SA-ST239-III (ST239), 5SA-ST5-II (ST5), 10SA-ST228-I (ST228), and 14SA-ST22-IVh (ST22), were tested for their ability to modulate cell viability in MG-63 osteoblast-like cells following successful invasion and persistence. Methicillin-sensitive S. aureus (MSSA) ATCC-12598-ST30 (ST30) was used as control strain. Despite being proven that ST30, ST239, and ST22 have a similar ability to internalize and persist in MG-63 osteoblast-like cells under our experimental conditions, we demonstrated that the observed decrease in cell viability was due to the different behavior of the considered strains, rather than the number of intracellular bacteria. We focused our attention on different biochemical cell functions related to inflammation, cell metabolism, and oxidative stress during osteoblast infections. We were able to show the following: (1) ST30 and ST239 were the only two clones able to persist and maintain their number in the hostile environment of the cell during the entire period of infection; (2) ST239 was the only clone able to significantly increase gene expression (3 and 24 h post-infection (p.i.)) and protein secretion (24 h p.i.) of both interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) in MG-63 osteoblast-like cells; (3) the same clone determined a significant up-regulation of the transforming growth factorbeta 1 (TGF-β1) and of the metabolic marker glyceraldehyde 3-phosphate dehydrogenase (GAPDH) mRNAs at 24 h p.i.; and (4) neither the MSSA nor the four methicillin-resistant S. aureus (MRSA) strains induced oxidative stress phenomena in MG-63 cells, although a high degree of variability was observed for the different clones with regard to the expression pattern of nuclear factor E2-related factor 2 (Nrf2) and its downstream gene heme oxygenase 1 (HO-1) activation. Our results may pave the way for an approach to S. aureus-induced damage, moving towards individualized therapeutic strategies that take into account the differences between MSSA and MRSA as well as the distinctive features of the different clones. This approach is based on a change of paradigm in antibiotic therapy involving a case-based use of molecules able to counteract pro-inflammatory cytokines activity such as selective cytokine signaling inhibitors (IL-6, TNF-α).

Antibiotic resistance profile and molecular characterization of Staphylococcus aureus strains isolated in hospitals in Kabul, Afghanistan

The aim of this study was to investigate the molecular features and the antibiotic resistance profile of 98 clinical Staphylococcus aureus isolates collected during 6 months in two hospitals of Kabul, Afghanistan. For all isolates, antimicrobial resistance patterns were determined by the disc diffusion method (including methicillin resistance which was detected using cefoxitin). The presence of the mecA/mecC genes was detected by PCR. Strains were then extensively characterized using microarray analysis. Of the 98 S. aureus isolates, methicillin-resistant S. aureus (MRSA) prevalence was high at 66.3%. Antibiotic susceptibility testing also revealed a high resistance rate to penicillin (100%), erythromycin (66.3%), ciprofloxacin (55.1%), and cotrimoxazole (40.8%). Resistance to tobramycin was detected in 25.5%, to gentamicin in 16.3%, to chloramphenicol in 34.7%, and to doxycycline in 23.5% of the isolates. All the MRSA isolates were mecA-positive and none of them harbored mecC. Isolates were grouped into twelve clonal complexes and twenty-seven distinct clones. The most frequently detected clones were the Southwest Pacific clone (CC30-MRSA-IV PVL+) (21/65 MRSA, 32.3%), the CC22-MRSA-IV TSST-1+ clone (11/65 MRSA, 16.9%), and the Bengal Bay clone (ST772-MRSA-V PVL+) (11/65 MRSA, 16.9%). The PVL genes were found in 59.2% (46/65 MRSA and 12/33 methicillin-susceptible S. aureus, MSSA) and tst1 gene in 16.3% of isolates. This molecular study highlights the high prevalence of MRSA and the large genetic diversity of the S. aureus isolates circulating and detected in two hospitals of Kabul, with the presence of multiple virulence and antibiotic resistance genes.

First report of methicillin-resistant Staphylococcus aureus carrying the mecC gene in human samples from Iran: prevalence and molecular characteristics

There is a lack of information concerning mecC clinical methicillin-resistant Staphylococcus aureus (MRSA) strains throughout the world. In the present survey, 345 MRSA strains were characterized by antimicrobial susceptibility testing and staphylococcal cassette chromosome mec element (SCCmec) typing. mecC-positive MRSA isolates were characterized by study of biofilm formability, adhesion and virulence analysis, multilocus sequence typing, accessory gene regulator (agr) typing, S. aureus protein A locus (spa) typing and staphylocoagulase typing. The present study found ten SCCmec types, with the majority being SCCmec type III (38.3%). The presence of mecC was confirmed in three isolates from skin wounds (two isolates) and burn wounds (one isolate). All the mecC-positive isolates carried SCCmec XI and belonged to coa type III. Molecular typing showed that these isolates belonged to clonal complex/ST130-spa type t843-agr type III (two isolates) and clonal complex/ST599-spa type 5930-agr type I. The presence of SCCmec type IV confirms the hypothesis of extensive infiltration from the community to the hospital. Detection of MRSA isolates harbouring the mecC gene highlights the need to perform routine detection methods and molecular investigations in order to identify these emerging strains and limit their transfer in hospitals and communities.

Genomic Characterization of Methicillin-Resistant Staphylococcus aureus (MRSA) by High-Throughput Sequencing in a Tertiary Care Hospital

Methicillin-resistant Staphylococcus aureus (MRSA) strains are associated with serious complications and poor clinical outcome. In Egypt, they contribute to more than 70% of S. aureus healthcare-associated infections. This study combined whole-genome sequencing, bioinformatics, and statistical analyses to identify the phylogeny, resistome, virulome and potential genotype–phenotype–clinical correlation among 18 clinical isolates of MRSA in a tertiary hospital in Cairo, Egypt. The ST1535-V MRSA clone was the most frequently isolated (16.6%), followed by ST5-VI, ST1-V and ST239-III (11.1% each). SCCmec V, VI, IV and III types were detected at frequencies of 50%, 16.6%, 11.1% and 11.1%, respectively. None of the tested virulence genes were detected in all isolates, but they ranged in distribution from 1/18 to 17/18. The Panton–Valentine leukocidin (PVL)-encoding genes were detected in only four isolates and were enriched in isolates causing non-severe cases. Phylogenetic analysis revealed relatedness between three ST1535-Vs, two ST5-VIs, two ST239-IIIs and two ST1-Vs; however, only the two genetically related ST1-V isolates were epidemiologically linked. While disease outcome and source of infection had no correlation with a particular genotypic pattern, the sequence type was the most correlated factor with phylogeny and genotypic patterns, and a few genes were associated with non-severe cases.

Molecular investigations on a chimeric strain of Staphylococcus aureus sequence type 80

A PVL-positive, methicillin-susceptible Staphylococcus aureus was cultured from pus from cervical lymphadenitis of a patient of East-African origin. Microarray hybridisation assigned the isolate to clonal complex (CC) 80 but revealed unusual features, including the presence of the ORF-CM14 enterotoxin homologue and of an ACME-III element as well as the absence of etD and edinB. The isolate was subjected to both, Illumina and Nanopore sequencing allowing characterisation of deviating regions within the strain´s genome. Atypical features of this strain were attributable to the presence of two genomic regions that originated from other S. aureus lineages and that comprised, respectively, 3% and 1.4% of the genome. One deviating region extended from walJ to sirB. It comprised ORF-CM14 and the ACME-III element. A homologous but larger fragment was also found in an atypical S. aureus CC1/ST567 strain whose lineage might have served as donor of this genomic region. This region itself is a chimera comprising fragments from CC1 as well as fragments of unknown origin. The other deviating region comprised the region from htsB to ecfA2, i.e., another 3% of the genome. It was very similar to CC1 sequences. Either this suggests an incorporation of CC1 DNA into the study strain, or alternatively a recombination event affecting “canonical” CC80. Thus, the study strain bears witness of several recombination events affecting supposedly core genomic genes. Although the exact mechanism is not yet clear, such chimerism seems to be an additional pathway in the evolution of S. aureus. This could facilitate also a transmission of virulence and resistance factors and therefore offer an additional evolutionary advantage.

Staphylococcus aureus and Methicillin Resistant S. aureus in Nepalese Primates: Resistance to Antimicrobials, Virulence, and Genetic Lineages

Staphylococcus aureus is a ubiquitous pathogen and colonizer in humans and animals. There are few studies on the molecular epidemiology of S. aureus in wild monkeys and apes. S. aureus carriage in rhesus macaques (Macaca mulatta) and Assam macaques (Macaca assamensis) is a species that has not previously been sampled and lives in remote environments with limited human contact. Forty Staphylococcus aureus isolates including 33 methicillin-susceptible S. aureus (MSSA) and seven methicillin-resistant S. aureus (MRSA) were characterized. Thirty-four isolates were from rhesus macaques and six isolates (five MSSA, one MRSA) were from Assam macaques. Isolates were characterized using StaphyType DNA microarrays. Five of the MRSA including one from Assam macaque were CC22 MRSA-IV (PVL+/tst+), which is a strain previously identified in Nepalese rhesus. One MRSA each were CC6 MRSA-IV and CC772 MRSA-V (PVL+). One MSSA each belonged to CC15, CC96, and CC2990. Six MRSA isolates carried the blaZ, while ten known CC isolates (seven MRSA, three MSSA) carried a variety of genes including aacA-aphD, aphA3, erm(C), mph(C), dfrA, msrA, and/or sat genes. The other 30 MSSA isolates belonged to 17 novel clonal complexes, carried no antibiotic resistance genes, lacked Panton–Valentine Leukocidin (PVL), and most examined exotoxin genes. Four clonal complexes carried egc enterotoxin genes, and four harbored edinB, which is an exfoliative toxin homologue.

Urban brown rats (Rattus norvegicus) as possible source of multidrug-resistant Enterobacteriaceae and meticillin-resistant Staphylococcus spp., Vienna, Austria, 2016 and 2017

Background

Brown rats (Rattus norvegicus) are an important wildlife species in cities, where they live in close proximity to humans. However, few studies have investigated their role as reservoir of antimicrobial-resistant bacteria.

Aim

We intended to determine whether urban rats at two highly frequented sites in Vienna, Austria, carry extended-spectrum β-lactamase-producing Enterobacteriaceae, fluoroquinolone-resistant Enterobacteriaceae and meticillin-resistant (MR) Staphylococcus spp. (MRS).

Methods

We surveyed the presence of antimicrobial resistance in 62 urban brown rats captured in 2016 and 2017 in Vienna, Austria. Intestinal and nasopharyngeal samples were cultured on selective media. We characterised the isolates and their antimicrobial properties using microbiological and genetic methods including disk diffusion, microarray analysis, sequencing, and detection and characterisation of plasmids.

Results

Eight multidrug-resistant Escherichia coli and two extensively drug-resistant New Delhi metallo-β-lactamases-1 (NDM-1)-producing Enterobacter xiangfangensis ST114 (En. cloacae complex) were isolated from nine of 62 rats. Nine Enterobacteriaceae isolates harboured the bla_CTX-M gene and one carried a plasmid-encoded ampC gene (bla_CMY-2). Forty-four MRS were isolated from 37 rats; they belonged to seven different staphylococcal species: S. fleurettii, S. sciuri, S. aureus, S. pseudintermedius, S. epidermidis, S. haemolyticus (all mecA-positive) and mecC-positive S. xylosus.

Conclusion

Our findings suggest that brown rats in cities are a potential source of multidrug-resistant bacteria, including carbapenem-resistant En. xiangfangensis ST114. Considering the increasing worldwide urbanisation, rodent control remains an important priority for health in modern cities.

Clinical, Epidemiologic, and Laboratory Aspects of Methicillin-Resistant Staphylococcus aureus Infections

Oxacillin-resistant Staphylococcus aureus (abbreviated MRSA for historical reasons) is a major pathogen responsible for both hospital- and community-onset disease. Resistance to oxacillin in most clinical isolates of S. aureus is mediated by PBP2a, a penicillin-binding protein with low affinity to beta-lactams, encoded primarily by the mecA gene. Rapid and accurate methods of susceptibility testing of S. aureus isolates to identify MRSA infections are important tools to limit the spread of this organism. This review focuses on the clinical significance of MRSA infections and new approaches for the laboratory diagnosis and epidemiologic typing of MRSA strains.

MRSA Strains in Nepalese Rhesus Macaques (Macaca mulatta) and Their Environment

This study looked at 227 saliva samples from Rhesus macaques (Macaca mulatta) and 218 samples from the surrounding environments. From these samples, MRSA isolates were collected from Rhesus saliva samples (n = 13) and environmental samples (n = 19) near temple areas in Kathmandu, Nepal. For comparison, selected MRSA isolates (n = 5) were obtained from patients with wound infections from a Kathmandu hospital. All isolates were characterized using Abbott StaphyType® DNA microarrays. Eighteen isolates (62%) from monkeys (n = 4; 31%) and environmental samples (n = 14; 74%), were CC22-MRSA-IV. Most (n = 16) of them carried both, the PVL locus and toxic shock toxin gene (tst1), an unusual combination which is the same as in previously characterized strain from Nepalese macaques and pigs. The five human isolates also belonged to that strain type. Eight monkey MRSA isolates were CC361-MRSA-IV. One MRSA from a monkey and one from an environmental sample, were CC88-MRSA-V. Other environmental MRSA included one each, CC121-MRSA-VT, and CC772 -MRSA-V. Two were CC779-MRSA-VT, potentially a novel clone. All MRSA carried the blaZ gene. The aacA-aphD, dfrA, and erm (C) genes were very common in isolates from all sources. One macaque MRSA carried the resistance genes aphA3 and sat, neither previously identified in primate MRSA isolates. This current study suggests that humans could be a potential source of the MRSA in the macaques/environment and transmission may be linked to humans feeding the primates and/or living in close proximity to each other.

Comparative Genomic Analysis of Staphylococcus haemolyticus Reveals Key to Hospital Adaptation and Pathogenicity

Staphylococcus haemolyticus is a skin commensal gaining increased attention as an emerging pathogen of nosocomial infections. However, knowledge about the transition from a commensal to an invasive lifestyle remains sparse and there is a paucity of studies comparing pathogenicity traits between commensal and clinical isolates. In this study, we used a pan-genomic approach to identify factors important for infection and hospital adaptation by exploring the genomic variability of 123 clinical isolates and 46 commensal S. haemolyticus isolates. Phylogenetic reconstruction grouped the 169 isolates into six clades with a distinct distribution of clinical and commensal isolates in the different clades. Phenotypically, multi-drug antibiotic resistance was detected in 108/123 (88%) of the clinical isolates and 5/46 (11%) of the commensal isolates (p < 0.05). In the clinical isolates, we commonly identified a homolog of the serine-rich repeat glycoproteins sraP. Additionally, three novel capsular polysaccharide operons were detected, with a potential role in S. haemolyticus virulence. Clinical S. haemolyticus isolates showed specific signatures associated with successful hospital adaption. Biofilm forming S. haemolyticus isolates that are resistant to oxacillin (mecA) and aminoglycosides (aacA-aphD) are most likely invasive isolates whereas absence of these traits strongly indicates a commensal isolate. We conclude that our data show a clear segregation of isolates of commensal origin, and specific genetic signatures distinguishing the clinical isolates from the commensal isolates. The widespread use of antimicrobial agents has probably promoted the development of successful hospital adapted clones of S. haemolyticus clones through acquisition of mobile genetic elements or beneficial point mutations and rearrangements in surface associated genes.

Genotyping of methicillin-resistant Staphylococcus aureus from sepsis patients in Pakistan and detection of antibodies against staphylococcal virulence factors

In order to obtain more information on the MRSA population structure in the border region of Afghanistan and Pakistan, we collected and genotyped MRSA causing bloodstream infections from a tertiary care hospital in Peshawar, Pakistan, that serves the local population as well as Afghan immigrants and refugees. Thirty-one MRSA isolates from 30 patients were included and characterized by microarray hybridisation. For 25 patients, serum samples were tested using protein microarrays in order to detect antibodies against staphylococcal virulence factors. The most conspicuous result was the high rate of PVL-positive MRSA. Twenty-two isolates (71%) harboured lukF/S-PV genes. The most common lineage was CC772-MRSA-V/VT (PVL+) to which eleven isolates were assigned. The second most common strain was, surprisingly, CC8-MRSA-[IV+ACME] (PVL+), "USA300" (9 isolates). Two isolates were tst1 positive CC22-MRSA-IV, matching the Middle Eastern "Gaza Epidemic Strain". Another two were PVL-positive CC30-MRSA-IV. The remaining isolates belonged to, possibly locally emerging, CC1, CC5, and CC8 strains with SCC mec IV elements. Twenty-three patient sera were positive for anti-PVL-IgG antibodies. Several questions arise from the present study. It can be assumed that MRSA and high rates of PVL-positive S. aureus/MRSA are a public health issue in the Afghanistan/Pakistan border region. A possible emergence of the "USA300" clone as well as of the CC772 lineage warrants further investigation.

Molecular characterisation of methicillin-resistant Staphylococcus pseudintermedius from dogs and the description of their SCCmec elements

In recent years an increasing number of methicillin-resistant S. pseudintermedius (MRSP) has been observed in both, healthy and clinically infected dogs. The aim of the study was the characterisation of MRSP isolates from clinical routine diagnostics of a German laboratory in order to assess the abundancy of resistance genes and SCCmec elements. 97 isolates from 96 dogs were analysed using microarrays detecting resistance genes and SCCmec-associated markers. All isolates harboured mecA and blaZ. Other abundant resistance markers (in >80% of isolates) included aacA-aphD, aphA3 and sat as well as erm(B). Tetracycline resistance genes (tet(K), tet(M)) and cat also were common (in >20%). The vast majority (n = 59) of isolates carried SCCmec III elements. SCCmec IV and V elements were identified in 21 and 15 isolates, respectively. Irregular or pseudo-SCCmec elements were found in 2 isolates. The high degree of uniformity of hybridisation patterns of tested strains suggest that the majority of MRSP infections was caused by one single strain and comparison to previously published reports and sequences suggest that this was the ST71-SCCmec III strain that also predominates elsewhere in Western Europe.

Genetic Profiling and Comparison of Human and Animal Methicillin-Resistant Staphylococcus aureus (MRSA) Isolates from Serbia

The aim of this study was to characterize a collection of methicillin-resistant Staphylococcus aureus (MRSA) isolates of human and animal origin from Serbia. In total, 36 MRSA isolates-30 obtained from humans and six from companion animals-were investigated by PCR for the presence of antibiotic and biocide resistance determinants and virulence genes (PVL-Panton⁻Valentine leukocidin, ETs-exfoliative toxins, TSST-toxic shock syndrome toxin, SEs-staphylococcal enterotoxins, and MSCRAMMs-microbial surface components recognizing adhesive matrix molecules and biofilm). Isolates were analyzed by staphylococcal cassette chromosome mec (SCCmec), spa, and dru typing, as well as by multiple locus variable number of tandem repeat analyses (MLVA), multilocus sequence typing (MLST), and subsequently, eBURST. The majority of human MRSA isolates were resistant to gentamicin, erythromycin, clindamycin, and ciprofloxacin. Different antibiotic resistance genes were detected: aac-aphD, ant(6')-Ia, erm(A), erm(B), erm(C), tet(K), tet(M), fexA, and catpC221. All isolates were susceptible to teicoplanin and linezolid. SCCmec type III was prevalent in human isolates, while SCCmec elements in animals were mostly nontypeable. t037 was the predominant spa type in human and t242 in animal MRSA isolates. The prevalent dru type was dt11c in human and dt10a in animal MRSA isolates. MRSA isolates exhibited 27 different MLVA types. ST239 was predominant in human, while ST5 was prevalent in canine MRSA isolates. PVL was found in two, while tsst-1 was detected in three human isolates. Human-associated clones belonging to ST5, ST45, and ST239 MRSA clones were discovered in companion animals, which suggests anthropozoonotic transmission.

Methicillin-Resistant Staphylococcus aureus ST80 Induce Lower Cytokine Production by Monocytes as Compared to Other Sequence Types

Methicillin-resistant Staphylococcus aureus (MRSA) remains an important cause of nosocomial and community-associated infections due to its ability to produce toxins and evade host's immune responses. The aim of the present study was to investigate the association of monocytes immune response in terms of cytokines produced after inoculation with different MRSA clones. Thirty-one clinical MRSA strains were selected on the basis of clonal types, accessory gene regulator (agr) groups and toxin genes carriage. Isolates were identified as S. aureus by Gram stain, catalase, coagulase production and PCR for nuc gene. The presence of mecA, lukS/lukF-PV (Panton-Valentine Leukocidin) and tst (Toxic Shock Syndrome Toxin-1) genes, as well as, the determination of agr groups was performed by PCR. Clonality was investigated by means of multi-locus sequence typing (MLST). Peripheral blood mononuclear cells were stimulated with live bacterial cells for 45 min at a ratio of 1:10. Cells were incubated for 10 h and supernatants were collected. The levels of Tumor Necrosis Factor alpha (TNFa), IL-1b, IL-8, IL-6, IL-12p40, IL-10, interferon-gamma (IFN-γ) and IL-2, were measured by Human Cytokine Multiplex Immunoassay kit. Thirteen strains were tst and 12 lukS/lukF-PV-positive. Seven strains belonged to ST80 and ST225, five to ST30 and ST239, while the remaining seven isolates were grouped together as "other." Strains belonging to ST80 induced statistically lower levels of TNFa, IL-1b, IL-8, IL-6, IL-10, IFN-γ, and IL-2. PVL-positive strains classified into ST80 clone induced statistically lower concentrations of most cytokines as compared to PVL-positive strains belonging to other clones, tst-positive strains and toxin-negative ones. Strains of agr3 group belonging to ST80 induced statistically lower concentrations of most tested cytokines as compared to agr3 strains not-belonging to ST80, agr2 or agr1. This low induction of immune response by MRSA ST80 cannot be attributed to the presence of neither lukS/lukF-PV nor agr3.

Characterization of Staphylococcal Cassette Chromosome mec Elements from Methicillin-Resistant Staphylococcus pseudintermedius Infections in Australian Animals

Staphylococcus pseudintermedius is a significant veterinary pathogen and occasional cause of infections in humans. β-Lactams are an important group of antimicrobials used to treat staphylococcal infections in humans and animals. However, when staphylococci become methicillin resistant via the acquisition of a mobile genetic element called staphylococcal cassette chromosome mec (SCCmec), they become resistant to all β-lactams. This study detected a novel SCCmec element among a cluster of methicillin-resistant S. pseudintermedius isolates from animals in Australia. It also detected SCCmec elements in S. pseudintermedius that had high similarity to those identified in methicillin-resistant Staphylococcus aureus, demonstrating how human and animal pathogens can share the same resistance determinants.

We examined the oxacillin resistance phenotype and genomic structure of staphylococcal cassette chromosome mec (SCCmec) elements from 77 veterinary methicillin-resistant Staphylococcus pseudintermedius (MRSP) isolates. Isolates were characterized by oxacillin broth microdilution, whole-genome sequencing, and bioformatics analysis. Five previously described SCCmec elements, and a sixth novel element, were identified: SCCmec III (also known as II-III), ΨSCCmec₅₇₃₉₅, and SCCmec_NA45 (a SCCmec VII variant), all previously described in MRSP, and SCCmec IVg and SCCmec V_T, previously described in both methicillin-resistant Staphylococcus aureus (MRSA) and MRSP. The sixth element was novel and found among nine geographically clustered isolates. This novel pseudostaphylococcal cassette chromosome (ΨSCCmec_KW21) contained a class A mec gene complex but lacked ccr genes. It also harbored heavy metal (cadmium) resistance determinants. The median oxacillin MIC values among ΨSCCmec_KW21, SCCmec III, and SCCmec V_T isolates were significantly higher than those determined for the SCCmec_NA45 VII variant isolates and ΨSCCmec₅₇₃₉₅ and SCCmec IVg isolates. ΨSCCmec_KW21 was found exclusively in sequence type 497 (ST497), an MRSP clone that is locally successful in Victoria, Australia. Future studies are necessary to determine if this clone has disseminated further afield and if ΨSCCmec_KW21 has moved into other MRSP lineages or staphylococcal species.

IMPORTANCEStaphylococcus pseudintermedius is a significant veterinary pathogen and occasional cause of infections in humans. β-Lactams are an important group of antimicrobials used to treat staphylococcal infections in humans and animals. However, when staphylococci become methicillin resistant via the acquisition of a mobile genetic element called staphylococcal cassette chromosome mec (SCCmec), they become resistant to all β-lactams. This study detected a novel SCCmec element among a cluster of methicillin-resistant S. pseudintermedius isolates from animals in Australia. It also detected SCCmec elements in S. pseudintermedius that had high similarity to those identified in methicillin-resistant Staphylococcus aureus, demonstrating how human and animal pathogens can share the same resistance determinants.