Comparison of community-onset Staphylococcus argenteus and Staphylococcus aureus sepsis in Thailand: a prospective multicentre observational study

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.

Prevalence of Staphylococcus argenteus among food handlers, kitchen utensils, and food samples in Japan

Staphylococcus argenteus has received increased attention from an aspect of food safety since several food poisoning outbreaks caused by the bacterium were reported in Japan. However, S. argenteus prevalence among food handlers and utensils has not yet been investigated. In this study, we investigated S. argenteus prevalence among a collection of coagulase-positive staphylococci (CPS) that were isolated during food sanitary inspections in Japan. Out of a total of 191 CPS isolates, 14 were identified as S. argenteus. One was isolated from shelled shrimp, nine were isolated from food handlers' hand swabs, and four were isolated from kitchen utensils. Whole-genome sequencing revealed that transmission of S. argenteus from human hands to utensils was possible. Though all 14 isolates were negative for the pvl and tst-1 genes, 6 harbored the seb gene. Only 21.4% of S. argenteus isolates were resistant to antibiotics, while 62.1% of the S. aureus isolates from the same sources were confirmed to be resistant. To the best of our knowledge, this is the first report to demonstrate possible transmission of S. argenteus from food handlers to utensils in food-processing environments.

Genetic characterization of methicillin-resistant / susceptible Staphylococcus aureus (MRSA/MSSA) and Staphylococcus argenteus clinical isolates in Bangladesh: Dominance of ST6-MRSA-IV/t304 and detection of cfr/fexA in ST8-MSSA/t008

Objectives

Coagulase-positive staphylococcus (CoPS), represented by Staphylococcus aureus, is a major cause of infections in humans. This study aimed to investigate molecular epidemiological characteristics, antimicrobial resistance, and their trends of CoPS in Bangladesh.

Methods

Clinical isolates of CoPS were collected from two medical institutions in Bangladesh for a 2-year period and analyzed for their species, genotypes, virulence factors, antimicrobial susceptibility, and resistance determinants.

Results

172 CoPS isolates collected were identified as S. aureus or S. argenteus (170 and two, respectively). Methicillin-resistant S. aureus (MRSA) accounted for 36% (n = 61), having Staphylococcal cassette chromosome mec (SCCmec)-IV (82%) or V (18%). Panton-Valentine leukocidin (PVL) genes were detected at higher rate in methicillin-susceptible S. aureus (MSSA) (62%) than MRSA (26%). MRSA comprised 11 STs, including a dominant type ST6 (46%) associated with mostly SCCmec-IVa/spa-t304, and one isolate had genetic features of the USA300 clone (ST8/SCCmec-IVa/coa-IIIa/spa-t008/ACME-I/ΦSa2USA). STs of CC1, CC88, and CC398 were common in MSSA, with CC88 showing the highest PVL-positive rate. One MSSA isolate (ST8/spa-t008) harbored fexA and cfr showing susceptibility to linezolid. S. argenteus was methicillin-susceptible and belonged to ST2250/coa-XId.

Conclusions

Genetic characteristics of current MRSA/MSSA in Bangladesh were revealed, with first identification of S. argenteus at low prevalence.

Staphylococcus argenteus bacteremia in the Republic of Korea

In 2015, Staphylococcus argenteus and Staphylococcus schweitzeri were proposed as new species, distinct from Staphylococcus aureus and collectively referred to as the S. aureus complex. However, no clinical reports of these new species exist in Korea. Upon the application of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for all bloodstream isolates since September 2022, S. argenteus was identified in one patient. Therefore, we aimed to search for new species among the archives of the S. aureus bacteremia cohort and describe their clinical and microbiological characteristics. Among the 691 archived S. aureus isolates between 2012 and 2018, one was identified as S. argenteus via MALDI-TOF MS. Both S. argenteus isolates (one in 2022) were obtained from patients with extensive pneumonia accompanied by bacteremia and both cases had fatal outcomes. They harbored multiple virulence genes (clfA, clfB, fnbpA, sdrC, sdrD, sdrE, bbp, cna, see, seg, sei, blaZ, fnbpB, and map) but did not harbor mecA and pvl. No matched sequence type (ST) was found in either isolate, and both S. argenteus isolates were closely related to ST1594, ST1593, ST1793, and ST1303, which belonged to S. argenteus. S. argenteus accounted for <1% of the S. aureus complex but had clinical characteristics similar to S. aureus. Therefore, clinicians should be aware of these factors to avoid misidentifying these strains as coagulase-negative staphylococci, and appropriate reporting is required to minimize confusion.IMPORTANCEStaphylococcus argenteus, a member of Staphylococcus aureus complex, has been reported as an important pathogen that causes clinically invasive infections in humans similar to S. aureus. Clinical isolates of S. argenteus have been reported across the world, showing a large geographical difference in prevalence and genomic profile. However, there have been no clinical reports regarding this new species in Korea. This is the first report to investigate the clinical and genetic characteristics of S. argenteus identified in patients with bacteremia, and the proportion of S. argenteus bacteremia among S. aureus bacteremia cohort in Korea.

Clonal Flux and Spread of Staphylococcus aureus Isolated from Meat and Its Genetic Relatedness to Staphylococcus aureus Isolated from Patients in Saudi Arabia

In this study, we investigated both meat-derived and methicillin-resistant Staphylococcus aureus (MRSA), exploring their genetic relatedness to patient-derived MRSA isolates in Saudi Arabia. We collected 250 meat samples and identified 53 S. aureus isolates, with 79% being methicillin-sensitive Staphylococcus aureus (MSSA) and 21% being MRSA. Moreover, we included 80 clinically confirmed patient-derived MRSA isolates. We identified the most common S. aureus clone in both patients and retail meat. In meat, ST6 and ST97 were the most common clones in 55% of the MRSA isolates, and ST1153 and ST672 were the most common in 21% and 17% of the MSSA isolates. In patients, ST5 and ST6 were the predominant clones in 46% of the S. aureus isolates. CC5/ST5-SCCmecVc-t311 and CC361/ST672-SCCmecV-t3841 were common MRSA clones in both meat and patients. CC97 and CC361 clones were the second most prevalent S. aureus clones in meat and were relatively common in patients. Furthermore, we sequenced and characterized novel S. aureus strains ST8109, ST8110, and ST8111. The genomic similarities between meat- and patient-derived S. aureus isolates suggest that retail meat might be a reservoir for S.aureus and MRSA transmission. Therefore, a structured One Health approach is recommended for S. aureus dissemination, genetic characterization, antibiotic resistance, and impact on human health.

Prevalence and characterization of Staphylococcus aureus and Staphylococcus argenteus isolated from rice and flour products in Guangdong, China

Staphylococcus aureus and Staphylococcus argenteus have been implicated in food poisoning outbreaks, and have been found in various types of food products according to our previous study. Rice and flour products are popular and widely consumed around the world. However, limited data are available on the microbial safety of S. aureus in rice and flour products, and S. argenteus has never been reported. Thus, this study aimed to investigate the contamination of S. aureus and S. argenteus in 250 fresh rice and flour product samples from five cities in Guangdong, China. According to qualitative and quantitative analyses, 68 (27.2 %) and 11 (4.4 %) samples were positive for S. aureus and S. argenteus, including 9 samples that exceeded 100 MPN/g. For antibiotics susceptibility tests in 16 antibiotics, the S. aureus isolates exhibited higher rates of resistance and multidrug resistance than S. argenteus. The S. aureus and S. argenteus isolates were mainly resistant to penicillin (70.21 %; 79.17 %), tetracycline (20.21 %; 58.33 %) and azithromycin (19.68 %, 8.33 %). However, the other antibiotic resistance rates were <10 %. Furthermore, the genetic background of the isolates was analyzed by whole-genome sequencing (WGS). As a result, the S. aureus isolates were divided into 18 known sequence types (STs) and 4 novel STs (ST7675, ST7679, ST7680 and ST7682), which mainly belonged to ST188 (20.6 %) and ST6 (14.7 %). The S. argenteus isolates mainly belonged to ST2250 (90.9 %), with a novel type (ST7683). In total, 36 and 16 antibiotic resistance genes (ARGs) were found in S. aureus and S. argenteus isolates, respectively. In addition, 91 virulence genes (VFs) were detected in S. aureus isolates as well as 90 % of core VFs were similar to S. argenteus. More than 20 % of the S. aureus isolates carried the classic enterotoxin gene (sea-sec), but chp, cna and map were free in all S. argenteus isolates. Importantly, 33.8 % of S. aureus isolates belonged to the immune evasion cluster (IEC) type B, whereas most of S. argenteus isolates (90.9 %) belong to IEC type E. According to the phylogenetic analysis, the S. aureus and S. argenteus isolates in fresh rice and flour products may indicate loss or acquisition of ARGs and VFs to survive and adapt to the environment. Our study confirmed the presence of S. argenteus in rice and flour products at first and focused on the multi-dimensional systematic comparative analysis of S. aureus and S. argenteus to reveal their ubiquity and similarities or differences, and provide more accurate and effective basic information for follow-up monitoring and tracking.

Fatal bacteremia caused by Staphylococcus argenteus: A case report

RATIONALE

Staphylococcus argenteus (S argenteus) is a novel and emerging species that is part of the Staphylococcus aureus (S aureus) complex. Fatal cases of bloodstream infection caused by S argenteus are rarely reported and should be considered in medical practice.

PATIENT CONCERNS

A 44-year-old male was admitted to our hospital with reduced appetite, high fever and unconsciousness. Laboratory tests indicated infection, muscle damage, and alkalosis in the patient. Brain computed tomography (CT) demonstrated small hematoma in left frontal lobe with peripheral cerebral edema. Chest CT demonstrating chronic bronchitis, emphysema, and bullae in the right lung. Blood culture was collected on the first day of hospitalization for microbial culture and pathological examination.

DIAGNOSIS

The isolate from blood culture was identified as S argenteus by MALDI-TOF MS after the patient death.

INTERVENTIONS

The patient was subjected to empirical antibiotic treatment with piperacillin/tazobactam.

OUTCOMES

After 48 hours of hospitalization, the patient died after ineffective rescue.

LESSONS

The patient had long-term heavy drinking and smoking as well as chronic malnutrition, which may account for his immune deficiency. The immunocompromised people are more vulnerable to infection by S argenteus and then develop bacteremia. The use of piperacillin/tazobactam may have contributed to the patient death.

Prevalence and Characteristics of Invasive Staphylococcus argenteus among Patients with Bacteremia in Hong Kong

Staphylococcus argenteus is a novel Staphylococcus species derived from Staphylococcus aureus. Information on the prevalence and genetic characteristics of invasive S. argenteus in Asia is limited. In this study, 275 invasive S. aureus complex strains were retrieved from blood culture specimens in Hong Kong and re-analyzed using MALDI-TOF mass spectrometry and an in-house multiplex real-time PCR for S. argenteus. The prevalence of invasive S. argenteus in Hong Kong was found to be 4.0% (11/275). These strains were primarily susceptible to commonly used antibiotics, except penicillin. Whole-genome sequencing revealed the circulation of three S. argenteus genotypes (ST-2250, ST-1223, and ST-2854) in Hong Kong, with ST-2250 and ST-1223 being the predominant genotypes. The local ST-2250 and ST-1223 strains showed close phylogenetic relationships with isolates from mainland China. Antimicrobial-resistant genes (fosB, tet-38, mepA, blaI, blaZ) could be found in nearly all local S. argenteus strains. The ST-1223 and ST-2250 genotypes carried multiple staphylococcal enterotoxin genes that could cause food poisoning and toxic shock syndrome. The CRISPR/Cas locus was observed only in the ST-2250 strains. This study provides the first report on the molecular epidemiology of invasive S. argenteus in Hong Kong, and further analysis is needed to understand its transmission reservoir.

Unveiling the First Staphylococcus argenteus Infection in Portugal

N/a.

Staphylococcus argenteus Infections, Brazil

In 2015, two new species related to the Staphylococcus aureus were proposed. We describe five isolates of the new species Staphylococcus argenteus cultured from human cases of bacteremia and skin and soft tissue infections. This is the first report of S. argenteus, from South America, causing community-acquired and nosocomial infections.

Characterization of the phenotypes of methicillin- and vancomycin-susceptible Staphylococcus argenteus after vancomycin passages

OBJECTIVES

Staphylococcus argenteus is generally more susceptible to antibiotic treatments than Staphylococcus aureus; however, the study showed that the daptomycin/vancomycin-resistant S. argenteus was isolated from a patient with repeated antibiotic treatments. In this study, the methicillin- and vancomycin-susceptible S. argenteus isolates were used to characterize the phenotypes of S. argenteus after vancomycin passages in vitro.

METHODS

Eleven S. argenteus isolates were used for passaging under different concentrations of vancomycin. The minimal inhibitory concentration (MIC) of vancomycin was determined by the agar dilution assay, and the biofilm mass of the passaged variants was quantified by the crystal violet staining assay and observed under the confocal microscope.

RESULTS

The MIC of vancomycin for eight of 11 S. argenteus isolates was increased from ≤2 µg/mL to ≤4-8 µg/mL after vancomycin passages. Two variants with the high-level vancomycin-intermediate (vancomycin MIC ≤8 µg/mL) phenotype were identified, and the parental strains of these variants did not have the heterogeneous vancomycin-intermediate population determined by the population profile analysis. Further, three S. argenteus isolates showed an increase in biofilm production and icaA transcription after the low-dose (2 µg/mL) vancomycin passages.

CONCLUSIONS

S. argenteus is capable of acquiring a vancomycin-tolerant phenotype and/or converting to a strong biofilm producer after vancomycin passages, which could contribute to the decrease of their antibiotic susceptibility.

Investigation of methicillin-resistant Staphylococcus aureus, methicillin-susceptible Staphylococcus aureus, and Staphylococcus argenteus from wild long-tailed macaques (Macaca fascicularis) at Kosumpee Forest Park, Maha Sarakham, Thailand

Background and Aim

In the past, the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) infections in both humans and animals has increased across Thailand. Staphylococcus argenteus has been associated with infections among humans, exotic pets, and livestock. Both species have been identified in non-human primate species from geographically diverse locations but not from non-human primates in Thailand. This study aimed to determine the presence of MRSA/methicillin-susceptible S. aureus (MSSA) and S. argenteus isolates collected from buccal swab samples in Macaca fascicularis at Kosumpee Forest Park (KFP), Maha Sarakham, Northeast Thailand.

Materials and Methods

Aseptic buccal swab samples were collected from 30 free-ranging macaques in November 2018. All isolates were tested using multiple biochemical tests and S. aureus latex slide agglutination test. Presumptive S. aureus isolates were tested for the presence of the mecA gene using polymerase chain reaction (PCR) assays. The isolates were phenotypically determined to be resistant to a β-lactam antibiotic using the disk diffusion method with a 30 mg cefoxitin disk. The isolates were analyzed by PCR for the non-ribosomal peptide synthetase (NRPS) gene to distinguish S. argenteus from S. aureus.

Results

Fifteen macaques (50%) were colonized with S. aureus and 21 isolates were characterized. Three of the macaques carried both the MRSA and MSSA isolate. One animal carried both MRSA and S. argenteus isolate, and one animal carried only S. argenteus. The NRPS gene analysis confirmed that 2 isolates (9.52%) were S. argenteus and 19 isolates (90.48%) were S. aureus [five MSSA and 14 MRSA].

Conclusion

This study is the first to identify MRSA/MSSA and S. argenteus in wild free-ranging M. fascicularis from Thailand at the KFP in Maha Sarakham. This study is also the first report on the occurrence of S. argenteus carriage in M. fascicularis from Thailand.

Staphylococcus schweitzeri—An Emerging One Health Pathogen?

The Staphylococcus aureus-related complex is formed by the Staphylococcus aureus, Staphylococcus schweitzeri, Staphylococcus argenteus, Staphylococcus roterodami and Staphylococcus singaporensis. Within this complex, S. schweitzeri is the only species mainly found in African wildlife, but it is rarely detected as a colonizer in humans or as a contaminant of fomites. The few detections in humans are most likely spillover events after contact with wildlife. However, since S. schweitzeri can be misidentified as S. aureus using culture-based routine techniques, it is likely that S. schweitzeri is under-reported in humans. The low number of isolates in humans, though, is consistent with the fact that the pathogen has typical animal adaptation characteristics (e.g., growth kinetics, lack of immune evasion cluster and antimicrobial resistance); however, evidence from selected in vitro assays (e.g., host cell invasion, cell activation, cytotoxicity) indicate that S. schweitzeri might be as virulent as S. aureus. In this case, contact with animals colonized with S. schweitzeri could constitute a risk for zoonotic infections. With respect to antimicrobial resistance, all described isolates were found to be susceptible to all antibiotics tested, and so far no data on the development of spontaneous resistance or the acquisition of resistance genes such the mecA/mecC cassette are available. In summary, general knowledge about this pathogen, specifically on the potential threat it may incur to human and animal health, is still very poor. In this review article, we compile the present state of scientific research, and identify the knowledge gaps that need to be filled in order to reliably assess S. schweitzeri as an organism with global One Health implications.

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.

Isolation and characterization of Staphylococcus argenteus strains from retail foods and slaughterhouses in Japan

Staphylococcus argenteus has been recently established as a novel species of Staphylococcus aureus complex. It is known to cause various human diseases, such as skin and soft-tissue infections, sepsis, and staphylococcal food poisoning, although the source of infection has not been clearly described. In food poisoning cases, the source of bacterial contamination in food is unknown. This study examined the prevalence of S. argenteus among retail fresh food and poultry slaughterhouses in Japan. Among 642 food samples examined, successful isolation of S. argenteus was achieved in 21 of 151 (13.9%) chicken samples. No isolations from pork, beef, fish, or vegetables in retail markets were confirmed. Multiple-locus sequence typing revealed that the 21 isolates were classified into four sequence types (ST) that were divided into 14 subtypes using spa-typing. All food isolates were susceptible to methicillin and did not show positivity for the Panton-Valentine leukocidin gene. When bacteria were isolated from two poultry slaughterhouses in the same region, 14 S. argenteus strains were successfully isolated from only one slaughterhouse. Thirteen of 14 strains were isolated from a poultry carcass and slaughterhouse environments during a certain sampling period and were all classified as ST5961 with identical spa-type. Also, the number of single nucleotide variants (SNVs) detected on the core genomes of the same 13 strains were between 0 and 17, suggesting a long-term inhabitation of an S. argenteus strain inside the facility. Furthermore, one isolate from chicken meat was also genetically linked with the same lineage of slaughterhouse isolates, with ≤15 SNVs being detected. Additionally, one slaughterhouse isolate from chiller water and three chicken isolates were classified into the same cluster by phylogenetic analysis, although the number of pairwise SNVs ranged from 62 to 128. To the best of the authors' knowledge, this is the first study that demonstrated S. argenteus in a food processing facility and the possible bacterial contamination on food during food processing.

Evolutionary Divergence of the Novel Staphylococcal Species Staphylococcus argenteus

Currently, invasive infections caused by Staphylococcus argenteus, which is a recently named staphylococcal species, are increasingly reported worldwide. However, only a few genomic studies of S. argenteus have offered comprehensive information regarding its genetic diversity, epidemiological characteristics, antimicrobial resistance genes (ARGs), virulence genes and other profiles. Here, we describe a comparative genomic analysis by population structure, pangenome, panmobilome, region-specific accessory genes confer an adaptive advantage in 153 S. argenteus strains which comprised 24 strains sequenced in this study and 129 strains whose genome sequences were available from GenBank. As a result, the population of S. argenteus comprised seven genetically distinct clades, including two major clades (C1 and C2), with distinct isolation source patterns. Pangenome analysis revealed that S. argenteus has an open pangenome composed of 7,319 genes and a core genome composed of 1,508 genes. We further determined the distributions of 75 virulence factors (VFs) and 30 known ARGs and identified at least four types of plasmids and 93 complete or partial putative prophages. It indicate that S. argenteus may show a similar level of pathogenicity to that of S. aureus. This study also provides insights into the evolutionary divergence of this pathogen, indicating that the geographical distribution was a potential driving force behind the evolutionary divergence of S. argenteus. The preferential horizontal acquisition of particular elements, such as staphylococcal cassette chromosome mec elements and plasmids, was observed in specific regions, revealing potential gene exchange between S. argenteus strains and local S. aureus strains. Moreover, multiple specific genes related to environmental adaptation were identified in strains isolated from East Asia. However, these findings may help promote our understanding of the evolutionary divergence of this bacterium at a high genetic resolution by providing insights into the epidemiology of S. argenteus and may help combat its spread.

Genomic Analysis of Global Staphylococcus argenteus Strains Reveals Distinct Lineages With Differing Virulence and Antibiotic Resistance Gene Content

Infections due to Staphylococcus argenteus have been increasingly reported worldwide and the microbe cannot be distinguished from Staphylococcus aureus by standard methods. Its complement of virulence determinants and antibiotic resistance genes remain unclear, and how far these are distinct from those produced by S. aureus remains undetermined. In order to address these uncertainties, we have collected 132 publicly available sequences from fourteen different countries, including the United Kingdom, between 2005 and 2018 to study the global genetic structure of the population. We have compared the genomes for antibiotic resistance genes, virulence determinants and mobile genetic elements such as phages, pathogenicity islands and presence of plasmid groups between different clades. 20% (n = 26) isolates were methicillin resistant harboring a mecA gene and 88% were penicillin resistant, harboring the blaZ gene. ST2250 was identified as the most frequent strain, but ST1223, which was the second largest group, contained a marginally larger number of virulence genes compared to the other STs. Novel S. argenteus pathogenicity islands were identified in our isolates harboring tsst-1, seb, sec3, ear, selk, selq toxin genes, as well as chromosomal clusters of enterotoxin and superantigen-like genes. Strain-specific type I modification systems were widespread which would limit interstrain transfer of genetic material. In addition, ST2250 possessed a CRISPR/Cas system, lacking in most other STs. S. argenteus possesses important genetic differences from S. aureus, as well as between different STs, with the potential to produce distinct clinical manifestations.

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.

Phenotypic and Genomic Profiling of Staphylococcus argenteus in Canada and the United States and Recommendations for Clinical Result Reporting

Staphylococcus argenteus is a newly described species, formerly known as S. aureus clonal complex 75 (CC75). Here, we describe the largest collection of S. argenteus isolates in North America, highlighting identification challenges. We present phenotypic and genomic characteristics and provide recommendations for clinical reporting. Between 2017 and 2019, 22 isolates of S. argenteus were received at 2 large reference laboratories for identification. Identification with routine methods (biochemical, matrix-assisted laser desorption ionization-time of flight mass spectrometry [MALDI-TOF MS], 16S rRNA gene analysis) proved challenging to confidently distinguish these isolates from S. aureus Whole-genome sequencing analysis was employed to confirm identifications. Using several different sequence-based analyses, all clinical isolates under investigation were confirmed to be S. argenteus with clear differentiation from S. aureus Seven of 22 isolates were recovered from sterile sites, 11 from nonsterile sites, and 4 from surveillance screens. While sequence types ST1223/coa type XV, ST2198/coa type XIV, and ST2793/coa type XId were identified among the Canadian isolates, the majority of isolates (73%) belonged to multilocus sequence types (MLST) ST2250/coa type XId and exhibited a high degree of homology at the genomic level. Despite this similarity, 5 spa types were identified among ST2250 isolates, demonstrating some diversity between strains. Several isolates carried mecA, as well as other resistance and virulence determinants (e.g., PVL, TSST-1) commonly associated with S. aureus Based on our findings, the growing body of literature on S. argenteus, the potential severity of infections, and possible confusion associated with reporting, including use of incorrect breakpoints for susceptibility results, we make recommendations for clinical laboratories regarding this organism.

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.

Colonization with Staphylococcus aureus and Klebsiella pneumoniae causes infections in a Vietnamese intensive care unit

Pre-existing colonization with Staphylococcus aureus or Klebsiella pneumoniae has been found to increase the risk of infection in intensive care patients. We previously conducted a longitudinal study to characterize colonization of these two organisms in patients admitted to intensive care in a hospital in southern Vietnam. Here, using genomic and phylogenetic analyses, we aimed to assess the contribution these colonizing organisms made to infections. We found that in the majority of patients infected with S. aureus or K. pneumoniae, the sequence type of the disease-causing (infecting) isolate was identical to that of corresponding colonizing organisms in the respective patient. Further in-depth analysis revealed that in patients infected by S. aureus ST188 and by K. pneumoniae ST17, ST23, ST25 and ST86, the infecting isolate was closely related to and exhibited limited genetic variation relative to pre-infection colonizing isolates. Multidrug-resistant S. aureus ST188 was identified as the predominant agent of colonization and infection. Colonization and infection by K. pneumoniae were characterized by organisms with limited antimicrobial resistance profiles but extensive repertoires of virulence genes. Our findings augment the understanding of the link between bacterial colonization and infection in a low-resource setting, and could facilitate the development of novel evidence-based approaches to prevent and treat infections in high-risk patients in intensive care.

Molecular characterization of clinical isolates from vascular access infection: A single-institution study

Hemodialysis requires repeated, reliable access to the systemic circulation; therefore, a well‐functioning vascular access (VA) procedure is crucial for stable hemodialysis. VA infections (VAIs) constitute the most challenging complication and cause considerable morbidity, loss of access, and even death. In this study, we investigated the molecular profiles of different bacterial isolates retrieved from various types of VA grafts. We collected clinical isolates from hemodialysis patients with VAIs in our institution for the period between 2013 and 2018. We identified the bacterial isolates using standard biochemical procedures; we used a polymerase chain reaction for coagulase‐negative staphylococci (CoNS) and Burkholderia cepacia complex (BCC) species identification. The antibiotic resistance and molecular profile were analyzed using the disk diffusion method and multilocus sequence typing, respectively. We studied 150 isolates retrieved from patients with VAI and observed that Staphylococcus aureus was the predominant bacterial species, followed by S. argenteus, BCC, and CoNS. According to multilocus sequence typing data, we identified a wide variety of sequence types (STs) in S. aureus isolates, with ST59, ST45, and ST239 being the predominant types. Burkholderia cepacia with two new ST types, namely ST1723 and ST1724, accounted for most of the BCC infections, along with ST102 B. contaminans, which were mainly isolated from infected tunneled‐cuffed catheters. In summary, the increased incidence of S. argenteus and BCC infections provides insights into their potential clinical effects in VAIs. The various STs identified in different bacterial species indicate the high genetic diversity of bacterial species isolated from VAIs in our institution.

Case Commentary: Daptomycin Resistance in Staphylococcus argenteus-from Northern Australia to San Francisco

Staphylococcus argenteus infection was initially described in Aboriginal patients in the Northern Territories of Australia as a predominant cause of skin infections and is rare outside Southeast Asia. A first well-characterized case of S. argenteus infection has now been described in the United States, involving a recurrent hemodialysis catheter infection, in which unstable daptomycin resistance evolved during daptomycin therapy. The unique colonial pigmentation of S. argenteus isolates in strains otherwise identified as Staphylococcus aureus is noteworthy.

Thoracic aortic mycotic aneurysm due to Staphylococcus argenteus: A case report

Staphylococcus argenteus was subdivided as a novel species from Staphylococcus aureus in 2014. We herein report a case of mycotic aneurysm caused by S. argenteus. A 59-year-old woman with diabetes and schizophrenia visited at the emergency room because of falling. Chest computed tomography revealed a left humerus fracture and a thoracic aortic aneurysm. With her elevated WBC count and CRP level, she was suspected to have a mycotic aneurysm. After being transferred to our hospital, vascular graft replacement surgery was performed. Isolates of blood cultures and surgical specimens were identified as S. argenteus by Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MAS MALDI Biotyper Ver. 8.0). Although S. argenteus lacks staphyloxanthin, a carotenoid pigment, it is coagulase positive. In addition to traditional and automated biochemical identification systems, even MALDI-TOF MAS may misidentify the organism as S. aureus depending on its version. S. argenteus should be considered when coagulase-negative Staphylococcus like colonies are obtained from samples of S. aureus infection. To our knowledge, this is the first case of aortic mycotic aneurysm caused by S. argenteus in Japan. Although S. argenteus is considered less virulent than Staphylococcus aureus, we should closely monitor the prevalence and the clinical impact of this pathogen on community-acquired infections and health care-associated infections.

Heterogeneity of Molecular Characteristics among Staphylococcus argenteus Clinical Isolates (ST2250, ST2793, ST1223, and ST2198) in Northern Taiwan

Staphylococcus argenteus is an emerging pathogen that is recognized as non-pigmented Staphylococcus aureus. However, the molecular characteristics of S. argenteus and its virulence factors have not been well studied. The present study analyzed 96 isolates of S. argenteus recovered from blood. Identification of S. argenteus was based on results of MALDI-TOF MS and lacking crtM gene. All 96 isolates were methicillin-susceptible. Multilocus sequence typing (MLST) revealed four sequence types: ST2250 (n = 72), ST2793 (n = 12), ST1223 (n = 10), and ST2198 (n = 2). All 72 ST2250 isolates harbored CRISPR loci with polymorphism of direct repeats and spacers, but no other STs carried CRISPR loci. To date, ST2793 isolates have rarely been reported in other countries. Collagen-binding adhesin gene (cna) and staphylococcal enterotoxin type C (sec) were detected in 12 (100%) and 8 (67%) ST2793 isolates, respectively. ST1223 has been reported as food poisoning pathogens, and enterotoxin gene clusters (egc) were detected in all 10 isolates, while seb gene was detected in three isolates. Two ST2198 isolates carried bone sialoprotein-binding protein gene (bbp), belonging to agr type IV. Our focus on the heterogeneity of molecular characterization in four ST types of S. argenteus revealed that S. argenteus had been isolated as early as 2000. Each ST type of S. argenteus harbors particular genetic markers that may contribute to their virulence.

First investigation of Staphylococcus argenteus in a Brazilian collections of S. aureus isolated from bovine mastitis

Background

Staphylococcus argenteus is a new specie positive coagulase staphylococci. We investigate the presence of S. argenteus in isolates previously classified as S. aureus, obtained from the milk of cows with mastitis in Brazil.

Results

Among 856 S. aureus tested in chocolate agar, tryptone soya agar and salt egg yolk agar, white or colorless colonies were observed in 185 (21.6%) isolates. Regarding the ctrOPQMN operon, 111 (60%) presented the complete cluster. Despite some missing genes in this cluster, the remaining strains (74) were confirmed as S. aureus using the nrps gene.

Conclusions

As far as we know, this is the first review of S. aureus collection in Brazil and S. argenteus does not appear to be a significant problem in Brazilian herds.

Human infections caused by Staphylococcus argenteus in Germany: genetic characterisation and clinical implications of novel species designation

We report a series of Staphylococcus argenteus infections from Saarland, Germany. Travel histories were unremarkable for extra-European sojourns, indicating an autochthonous transmission mode. Multilocus sequence typing revealed that all isolates were members of the clonal complex CC2250. In only one case, guideline-adherent treatment with an isoxazolyl penicillin was prescribed. Our report illustrates the perils of novel species designations, which may lead to misconceptions and suboptimal treatment choices among clinicians.

Bacterial keratoconjunctivitis caused by Staphylococcus argenteus belonging to sequence type 1223 isolated in Japan

Staphylococcus argenteus, characterized by the formation of non-pigmented (white) colonies, was recently identified as a new lineage separated from Staphylococcus aureus. However, correct identification of this lineage is difficult because of the similar characteristics to S. aureus. Here, we describe the first known case of keratoconjunctivitis due to S. argenteus in a 64-year-old man with diabetes. The symptoms of the patient were not improved by antibiotic therapy using levofloxacin eye drops (15 mg/mL). The conjunctival scraping was cultured, and coagulase-positive staphylococci forming white colonies were detected. Matrix-assisted laser desorption/ionization-time of flight mass spectrometry confirmed the species as S. argenteus with a spectral score of 1.97. After the antibiotic was changed to vancomycin eye drops (10 mg/mL), the patient's symptom clearly improved. Multi-locus sequence typing showed that this isolate belonged to sequence type 1223, which has been predominantly isolated worldwide. Furthermore, this isolate harbored various virulence genes associated with S. aureus, such as staphylococcal enterotoxins and leukocidin. Since only limited information is available for this organism, further studies are needed to establish the epidemiology of S. argenteus.

Staphylococcus argenteus as an etiological agent of prosthetic hip joint infection: a case presentation

This report presents a case of prosthetic hip infection caused by Staphylococcus argenteus, a potentially overlooked etiology of prosthetic joint infections (PJIs). Whole-genome sequencing showed that the S. argenteus isolate was an ST2250 and clustered within other CC2250 isolates, the largest clonal group of S. argenteus. This sequence type is prevalent and may be associated with invasive infections. The present isolate was phenotypically fully susceptible to all tested antimicrobial agents and genome analysis did not detect any resistance genes, nor were any staphylococcal cassette chromosome residues detected. Despite initial appropriate management with debridement and biofilm-active antibiotics, the outcome was unfavorable with recurrence and a persistent infection treated with suppressive antibiotics. Regarding the repertoire of genomic traits for virulence in S. argenteus, PJIs caused by this bacterium should be treated accordingly as Staphylococcus aureus PJIs.

Staphylococcus argenteus isolated from retail foods in China: Incidence, antibiotic resistance, biofilm formation and toxin gene profile

Staphylococcus argenteus is a novel species of coagulase-positive staphylococci which was separated from Staphylococcus aureus in 2014. It can threaten human health like S. aureus but can not identify with conventional biochemical or other phenotypic testing. From 2011 to 2016, 1581 S. aureus strains were isolated from 4300 samples from retail foods covering most provincial capitals in China. According to multilocus sequence typing (MLST) and PCR confirmation, 7.2% of isolates (114/1581) were confirmed as S. argenteus. The pathogen was distributed in 22 of 39 sampled cities and all food types. Interestingly, most S. argenteus positive samples were collected from coastal cities in South China. MLST detected 8 different sequence types (STs), including five new STs. CC2250 was the predominant lineage of S. argenteus, followed by CC1223. To further characterize the isolates, their antibiotic resistance, virulence genes, biofilm formation and biofilm-related genes were examined. The pvl gene was not detected in S. argenteus, and only 1 isolate (0.9%) was positive for the tsst-1 gene. For 18 enterotoxin genes, 16.7% (19/114) of isolates harboured more than three genes, whereas 70.2% (80/114) of isolates had none of the investigated genes. Penicillin and ampicillin were the major antibiotics to which the S. argenteus isolates were resistant, followed by tetracycline, kanamycin and fusidic acid. A total of 94.7% of isolates had the ability to produce biofilms and all isolates harboured icaA, fnbA, and fib genes. Other biofilm-related genes, such as eno, clfB, fnbB, and icaC, were also found in 99.1%, 92.1%, 88.6%, and 74.6% of isolates, respectively. This study is the first systematic investigation of the prevalence of S. argenteus in retail foods in China and shows their ubiquity in food. We also provide comprehensive surveillance of the incidence of S. argenteus in retail foods and information to enable more accurate and effective treatment of infections of this new species.

Staphylococcus argenteus and Staphylococcus schweitzeri are cytotoxic to human cells in vitro due to high expression of alpha-hemolysin Hla

Staphylococcus argenteus and Staphylococcus schweitzeri are newly identified species of the S. aureus-related complex. S. argenteus, as occurring globally and showing significant prevalence and comparable infection and morbidity rates compared to S. aureus, is becoming clinically important. Whole genome sequencing has revealed the presence of several virulence genes but the molecular mechanisms of S. argenteus infection and virulence are largely unknown. Here, we studied the effect of a previously characterized clinical S. argenteus isolate on human cells in vitro. The clinical isolate, together with the S. argenteus type strain MSHR1132T and the S. schweitzeri type strain FSA084T, had a cytotoxic effect on the cells, which showed necrotic cell death after a few hours of treatment. The protein causing the cytotoxic effect was purified and identified by mass spectrometry as alpha-hemolysin, Hla, which is awell-known pore-forming toxin in S.aureus. The cytotoxic effect could be blocked with an antibody against Hla. S.argenteus showed 12–15 fold higher expression levels of hla at the RNA level and 4–6 fold higher expression levels at the protein level compared to S.aureus. The higher expression levels of hla were supported by higher RNA levels of the regulatory factors sarA and saeR. Also, the RNAIII component of the accessory gene regulator (agr) quorum sensing system was 8,000–10,000 fold higher in the S.argenteus isolates compared to S.aureus. This is the first study on the effect of S.argenteus on ahuman cell line and strengthens the idea of significant virulence of S.argenteus.

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

Aim: To determine the genetic makeup of methicillin-sensitive/methicillin-resistant Staphylococcus aureus (MSSA/MRSA) from nasal colonization and environmental contamination in dental clinics. Materials and Methods: Nasal swabs from students and health care workers and environmental swabs were obtained at two academic dental clinics in the United Arab Emirates. The StaphyType DNA microarray-based assay was used for molecular characterization. Results: Forty-eight S. aureus isolates were identified phenotypically (nasal: n = 43; environmental: n = 5), but 6 of these were assigned to S. argenteus by genotyping. These were CC_(argenteus)2596, CC_(arg)2250-MSSA, CC_(arg)2250-MSSA-(Panton Valentine leukocidin [PVL]+) (n = 2), and CC_(arg)2198-MSSA (n = 2). MRSA nasal colonization rate was 5.4% (n/N = 8/146) with the following strain affiliations: CC5-MRSA-[IV+fus+ccrAB], "Maltese Clone"; CC6-MRSA-IV, "WA MRSA-51"; CC22-MRSA-IV (PVL+/tst+); CC22-MRSA-[IV+fus+ccrAA/(C)]; and two each of CC5-MRSA-[VI+fus] and CC97-MRSA-[V/VT+fus]. The SCC-borne fusidic acid resistance (fusC) gene was detected in MRSA (n = 5) and MSSA (n = 1). Some MSSA strains, CC1-MSSA-[fus+ccrAB1] and ST1278-MSSA-[ccrA1], harbored recombinase genes. A CC30-MSSA harbored ACME locus/arc-genes, while ST1278-MSSA-[ccrA1] had an ACME-III element. Enterotoxin genes were commonly carried, but tst-1 gene was found in only CC22, CC30, and CC34 strains, while pvl genes were identified in CC_(arg)2250 and CC22-MRSA-IV. Of the 51 noncoagulase staphylococci (CoNS) identified, 18 were mecA positive. Conclusion: The findings demonstrate the first report of rare strains (ST1278 MSSA, CC_(arg)2198, CC_(arg)2596, and PVL+CC_(arg)2250) in our region. Detection of MSSA with recombinase genes and ACME loci alongside mecA-positive CoNS is of clinical significance as this could provide a milieu for acquisition and transfer of SCC-elements, either with different ACME types, with fusC or the mecA gene resulting in conversion of MSSA into MRSA.

Methicillin-resistant Staphylococcus argenteus misidentified as methicillin-resistant Staphylococcus aureus emerging in western Sweden

Two strains included in a whole-genome sequencing project for methicillin-resistant Staphylococcus aureus (MRSA) were identified as non-Staphylococcus aureus when the sequences were analysed using the bioinformatics software ALEX (www.1928diagnostics.com, Gothenburg, Sweden). Sequencing of the sodA gene of these strains identified them as Staphylococcus argenteus. The collection of MRSA in western Sweden was checked for additional strains of this species. A total of 18 strains of S. argenteus isolated between 2011 and December 2017 were identified.

Staphylococcus argenteus: An emerging subclinical bovine mastitis pathogen in Thailand

Background and Aim:

Staphylococcus argenteus is an emerging species of the Staphylococcus aureus complex. It has usually been misidentified as S. aureus by conventional methods and its characteristics. S. argenteus is potentially emerging in both humans and animals with an increasing global distribution. This study aimed to differentiate and identify S. argenteus from S. aureus collected and isolated from milk samples of subclinical bovine mastitis cases in Maha Sarakham Province, Northeastern Thailand.

Materials and Methods:

Forty-two isolates of S. aureus were studied from 132 individual milk samples collected from subclinical bovine mastitis cases of 15 dairy farms in three districts of Maha Sarakham, Thailand. The identification was confirmed by conventional and immune-agglutination methods. Fifteen representative isolates which were suspected as being S. argenteus were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS).

Results:

The result from MALDI-TOF MS confirmed that seven from 15 isolates were S. argenteus and eight isolates were S. aureus.

Conclusion:

This study indicated that MALDI-TOF MS used as an identification and classification method could accurately differentiate the novel species, S. argenteus, from the S. aureus complex which is usually misdiagnosed. In addition, the identification of S. argenteus seems to be very limited in technical difficulty despite the fact that it may be the important causative pathogen in bovine mastitis as well as a pathogenic bacterium in food and milk. Therefore, it is essential for both bovine medicine and veterinary public health to emphasize and recognize this bacterial pathogen as an emerging disease of staphylococcal bacteria that there is a need for further study of S. argenteus infections.

Predictive Validity of the qSOFA Score for Sepsis in Adults with Community-Onset Staphylococcal Infection in Thailand

The quick sequential organ failure assessment (qSOFA) score has had limited validation in lower resource settings and was developed using data from high-income countries. We sought to evaluate the predictive validity of the qSOFA score for sepsis within a low- and middle-income country (LMIC) population with culture-proven staphylococcal infection. This was a secondary analysis of a prospective multicenter cohort in Thailand with culture-positive infection due to Staphylococcus aureus or S. argenteus within 24 h of admission and positive (≥2/4) systemic inflammatory response syndrome (SIRS) criteria. Primary exposure was maximum qSOFA score within 48 h of culture collection and primary outcome was mortality at 28 days. Baseline risk of mortality was determined using a multivariable logistic regression model with age, gender, and co-morbidities significantly associated with the outcome. Predictive validity was assessed by discrimination of mortality using area under the receiver operating characteristic (AUROC) curve compared to a model using baseline risk factors alone. Of 253 patients (mean age 54 years (SD 16)) included in the analysis, 23 (9.1%) died by 28 days after enrollment. Of those who died, 0 (0%) had a qSOFA score of 0, 8 (35%) had a score of 1, and 15 (65%) had a score ≥2. The AUROC of qSOFA plus baseline risk was significantly greater than for the baseline risk model alone (AUROC_qSOFA = 0.80 (95% CI, 0.70–0.89), AUROC_baseline = 0.62 (95% CI, 0.49–0.75); p < 0.001). Among adults admitted to four Thai hospitals with community-onset coagulase-positive staphylococcal infection and SIRS, the qSOFA score had good predictive validity for sepsis.

The Whole-Genome Sequence of Plasmid-Bearing Staphylococcus argenteus Strain B3-25B from Retail Beef Liver Encodes the Type VII Secretion System and Several Virulence Factors

The whole-genome sequence of Staphylococcus argenteus strain B3-25B, isolated from retail beef liver, comprises a circular chromosome (2,676,222 bp) and a single plasmid (21,570 bp). The chromosome harbors genes encoding the type VII secretion system and several virulence factors.

Molecular Epidemiological Characterization of Staphylococcus argenteus Clinical Isolates in Japan: Identification of Three Clones (ST1223, ST2198, and ST2550) and a Novel Staphylocoagulase Genotype XV

Staphylococcus argenteus, a novel emerging species within Staphylococcus aureus complex (SAC), has been increasingly reported worldwide. In this study, prevalence of S. argenteus among human clinical isolates, and their clonal diversity and genetic characteristics of virulence factors were investigated in Hokkaido, the northern main island of Japan. During a four-month period starting from March 2019, twenty-four S. argenteus and 4330 S. aureus isolates were recovered from clinical specimens (the ratio of S. argenteus to S. aureus :0.0055). Half of S. argenteus isolates (n = 12) belonged to MLST sequence type (ST) 2250 and its single-locus variant, with staphylocoagulase genotype (coa-) XId, while the remaining isolates were assigned to ST2198/coa-XIV (n = 6), and ST1223 with a novel coa-XV identified in this study (n = 6). All the isolates were mecA-negative, and susceptible to all the antimicrobials tested, except for an ST2198 isolate with blaZ and an ST2250 isolate with tet(L) showing resistance to ampicillin and tetracyclines, respectively. Common virulence factors in the S. argenteus isolates were staphylococcal enterotoxin (-like) genes sey, selz, sel26, and sel27 in ST2250, selx in ST2198, and enterotoxin gene cluster (egc-1: seg-sei-sem-sen-seo) in ST1223 isolates, in addition to hemolysin genes (hla, hlb, and hld) distributed universally. Elastin binding protein gene (ebpS) and MSCRAMM family adhesin SdrE gene (sdrE) detected in all the isolates showed high sequence identity among them (> 97%), while relatively lower identity to those of S. aureus (78–92%). Phylogenetically, ebpS, sdrE, selx, sey, selw, sel26, and sel27 of S. argenteus formed clusters distinct from those of S. aureus, unlike sec, selz, tst-1, and staphylokinase gene (sak). The present study revealed the prevalence of S. argenteus among clinical isolates, and presence of three distinct S. argenteus clones (ST2250; ST2198 and ST1223) harboring different virulence factors in northern Japan. ST2198 S. argenteus, a minor clone (strain BN75-like) that had been rarely reported, was first identified in Japan as human isolates.

Emergence of novel methicillin-resistant Staphylococcus aureus strains in a tertiary care facility in Riyadh, Saudi Arabia

PURPOSE

There is a need for continuous surveillance of methicillin-resistant Staphylococcus aureus (MRSA) to identify emergence of new strains. We hypothesize that MRSA strains are evolving with ongoing acquisition of SCCmec elements. This study was carried out to evaluate the evolution of MRSA at a tertiary care facility in Saudi Arabia.

METHODS

MRSA isolates associated with invasive clinical infection, which were identified in 2017 at the microbiology laboratory, King Khalid University Hospital (KKUH) in Riyadh, Saudi Arabia, were studied. The molecular characterization of isolates was carried out using StaphyType DNA microarray (Alere Technologies GmbH/Abbott, Jena, Germany).

RESULTS

The 125 MRSA isolates studied belonged to 18 clonal complexes (CC) which were distributed into 32 strain assignments. The predominant CC were CC5 (n=30), CC6 (n=17), CC80 (n=13), CC22 (n=12), CC361 (n=12). The findings demonstrated the first identification of CC152, CC361 and CC1153 MRSA as well as ST5-MRSA-[I+fus], "Geraldine Clone", CC6-MRSA-IV (PVL+) and CC88-MRSA-V (PVL+), WA MRSA-117 in Saudi Arabia. Four novel variants were identified: CC5-MRSA-[VI+fus+tirS], CC22-MRSA-[V/VT+fus](PVL+), CC152-MRSA-[V+fus](PVL+) and CC361-MRSA-[VT+fus]. Fifty-four isolates (n/N=54/125; 43.2%) including the novel strains carried the Q6GD50 SCCfusC gene while the Panton-Valentine leukocidin genes were present in 30.4% (n/N=38/125).

CONCLUSION

The findings demonstrate an expanding MRSA repertoire in our setting including emergence of previously unreported clonal complexes and novel strains. The high carriage of fusC gene suggests a role for fusidic acid misuse in driving the evolution of the MRSA genome and underscores the need for increased monitoring of antibiotic use.

Implications of identifying the recently defined members of the Staphylococcus aureus complex S. argenteus and S. schweitzeri: a position paper of members of the ESCMID Study Group for Staphylococci and Staphylococcal Diseases (ESGS)

BACKGROUND

Staphylococcus argenteus and Staphylococcus schweitzeri, previously known as divergent Staphylococcus aureus clonal lineages, have been recently established as novel, difficult-to-delimit, coagulase-positive species within the S. aureus complex. Methicillin-resistant strains of S. argenteus are known from Australia and the UK. Knowledge of their epidemiology, medical significance and transmission risk is limited and partly contradictory, hampering definitive recommendations. There is mounting evidence that the pathogenicity of S. argenteus is similar to that of 'classical' S. aureus, while as yet no S. schweitzeri infections have been reported.

AIM

To provide decision support on whether and how to distinguish and report both species.

SOURCES

PubMed, searched for S. argenteus and S. schweitzeri.

CONTENT

This position paper reviews the main characteristics of both species and draws conclusions for microbiological diagnostics and surveillance as well as infection prevention and control measures.

IMPLICATIONS

We propose not distinguishing within the S. aureus complex for routine reporting purposes until there is evidence that pathogenicity or clinical outcome differ markedly between the different species. Primarily for research purposes, suitably equipped laboratories are encouraged to differentiate between S. argenteus and S. schweitzeri. Caution is urged if these novel species are explicitly reported. In such cases, a specific comment should be added (i.e. 'member of the S.aureus complex') to prevent confusion with less- or non-pathogenic staphylococci. Prioritizing aspects of patient safety, methicillin-resistant isolates should be handled as recommended for methicillin-resistant Staphylococcus aureus (MRSA). In these cases, the clinician responsible should be directly contacted and informed by the diagnosing microbiological laboratory, as they would be for MRSA. Research is warranted to clarify the epidemiology, clinical impact and implications for infection control of such isolates.

Low incidence of Staphylococcus argenteus bacteremia in Hiroshima, Japan

Staphylococcus argenteus is a globally distributed cause of human infection; however, it has been misidentified as Staphylococcus aureus in diagnostic laboratories. Invasive infection caused by S. argenteus has been increasingly reported worldwide. However, there have been no reports on S. argenteus bacteremia in Japan. Therefore, we conducted a retrospective study to investigate the incidence of S. argenteus bacteremia at Hiroshima University Hospital between 2013 and 2017. S. argenteus was identified based on the absence of the crtM gene and multi-locus sequence typing. S. argenteus was identified in 2 of the 201 S. aureus blood culture isolates (1.0%). Both S. argenteus isolates belonged to sequence type 2250 harboring the staphylococcal enterotoxin Y gene (sey) and were susceptible to methicillin. One of them was penicillin-resistant, harboring a blaZ gene. The primary sites of infection were lower leg cellulitis and catheter-related blood stream infection. No patients died during hospitalization. This study suggested a low incidence of S. argenteus bacteremia in Japan when compared with reports from other countries. Further studies are necessary to investigate the prevalence of S. argenteus infection in Japan and the clinical impact of S. argenteus compared to S. aureus.

Staphylococcus argenteus from rabbits in Thailand

Staphylococcus argenteus, a novel species of the genus Staphylococcus or a member of the S. aureus complex, is closely related to S. aureus and is usually misidentified. In this study, the presence of S. argenteus in isolated S. aureus was investigated in 67 rabbits with abscess lesions during 2014-2016. Among 19 S. aureus complex isolates, three were confirmed to be S. argenteus by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, nonribosomal peptide synthetase gene amplification, and multilocus sequence type. All S. aureus complex isolates, including the S. aureus isolates, were examined for their antimicrobial resistance phenotype by disk diffusion and for their resistance genotype by PCR assays. Among the S. argenteus isolates, one was susceptible to all antimicrobial drugs and the other two were resistant to penicillin and doxycycline. In contrast, most S. aureus isolates were resistant to penicillin (37.5%), and gentamicin (12.5%). Moreover, S. aureus isolates harbored the blaZ, mecA, aacA-aphD, and mrs(A) as well as mutations of gyrA and grlA, but S. argenteus isolates carried solely the blaZ. S. argenteus isolates were investigated for enterotoxin (sea-sed) and virulence genes by PCR. One isolate carried sea, sec, and sed, whereas the other two isolates carried only sea or sed. No isolate carried seb and see. All three S. argenteus isolates carried hla, hlb, and clfA, followed by pvl, whereas coa, spa (IgG-binding region), and spa (x region) were not detected in the three isolates. This paper presents the first identification of S. argenteus from rabbits in Thailand. S. argenteus might be pathogenic because the isolates carried virulence genes. Moreover, antimicrobial resistance was observed. Investigations of this new bacterial species should be conducted in other animal species as well as in humans.

Staphylococcus spp. associated with subclinical bovine mastitis in central and northeast provinces of Thailand

Background

Staphylococcus spp. are major cause of bovine mastitis (BM) worldwide leading to economic damage to dairy farms and public health threat. Recently, a newly emerged Staphylococcus argenteus has been found as a human and animal pathogen. Molecular characteristics, virulence and antibiotic resistant phenotypes of bacteria causing BM in Thailand are rare. This study aimed to investigated Staphylococcus spp. associated with subclinical bovine mastitis (SCM) in Thailand.

Methods

Milk samples were collected from 224 cows of 52 dairy herds in four central and northeast provinces. Total somatic cell counts (SCC) and California mastitis test (CMT) were used to identify SCM cows. Milk samples were cultured for Staphylococcus spp. Coagulase-positive isolates were subjected to pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Organisms suspected as S. argenteus were verified by detecting nonribosomal peptide synthetase gene. All isolates were checked for antibiograms and the presence of various virulence genes.

Results

From the 224 milk samples of 224 cows, 132 (59%) were positive for SCM by SCC and CMT and 229 staphylococcal isolates were recovered. They were 32 coagulase-positive (24 S. aureus and eight S. argenteus) and 197 coagulase-negative. PFGE of the S. aureus and S. argenteus revealed 11 clusters and a non-typeable pattern. MLST of representatives of the 11 PFGE clusters, three PFGE non-typeable S. aureus isolates from different locations and S. argenteus showed 12 sequence types. The eight S. argenteus isolates belonged to ST1223 (three isolates), ST2250 (two isolates), and ST2793 (two isolates). The antimicrobial tests identified 11 (46%) methicillin-resistant S. aureus and 25 (13%) methicillin-resistant coagulase-negative isolates, while seven S. argenteus were methicillin-susceptible and one isolate was methicillin-resistant. All of the 229 isolates were multiply resistant to other antibiotics. The most prevalent virulence genes of the 24 S. aureus isolates were clfA, coa and spa (X and IgG-binding region) (100%), hla (96%), pvl (96%) and sec (79%). Six S. argenteus isolates carried one enterotoxin gene each and other virulence genes including coa, clfA, hla/hlb, spa, tsst and pvl, indicating their pathogenic potential.

Conclusion and perspective

This is the first report on the S. argenteus from cow milk samples with SCM. Data on the molecular characteristics, virulence genes and antibiograms of the Staphylococcus spp. obtained from the present study showed a wide spread and increasing trend of methicillin-resistance and multiple resistance to other antibiotics. This suggests that the "One Health" practice should be nurtured, not only at the dairy farm level, but also at the national or even the international levels through cooperation of different sectors (dairy farmers, veterinarians, medical and public health personnel and scientists) in order to effectively combat and control the spread of these pathogens.

Which methods are appropriate for the detection of Staphylococcus argenteus and is it worthwhile to distinguish S. argenteus from S. aureus?

Purpose

To further analyze a clinical isolate originally identified as methicillin-resistant Staphylococcus aureus (MRSA) using whole-genome sequencing and comparative genomics.

Materials and methods

Classical diagnostic methods such as cultivation, biochemical tests, and PCR were supplemented with whole-genome sequencing and comparative genomics, to identify the isolate.

Results

The isolate was phenotypically similar to MRSA. However, the presence of the nuc gene could not be confirmed using PCR, while it was positive for the mecA gene. Whole-genome sequencing correctly identified the isolate as Staphylococcus argenteus. The isolate possessed several resistance genes, such as mecA, blaZ (β-lactam antibiotics) and dfrG (trimethoprim). The nuc gene differed from that of MRSA. Six phylogenetic distinct clusters were identified by average nucleotide identity (ANI) analysis of all available S. argenteus whole-genome sequences. Our isolate, RK308, clustered with those isolated in Europe and Asia.

Conclusion

Due to the invasive potential, the multi-drug resistance and the similarity to MRSA, S. argenteus should be included in the MRSA screening. Due to the divergent genome compared to MRSA, new PCR approaches have to be developed to avoid an unnoticed spreading of S. argenteus.

Community-Acquired Staphylococcus argenteus Sequence Type 2250 Bone and Joint Infection, France, 2017

We report a rare case of Staphylococcus argenteus bone and joint infection in a 9-year-old boy in France. His finger arthritis was complicated by osteitis 5 weeks later, which resulted in a secondary intervention. This case indicates the virulence of S. argenteus, an emerging pathogen whose clinical effects are poorly described.

Accurate differentiation of novel Staphylococcus argenteus from Staphylococcus aureus using MALDI-TOF MS

Aim: We evaluated a Staphylococcus argenteus-specific diagnostic profile of matrix-assisted laser desorption/ionization time-of-flight mass spectrometer for accurate identification of this novel bacterium. Materials & methods: Staphylococcus argenteus was identified based on negative crtM gene and presence of specific sequence types. A classification model was generated by cluster analysis of matrix-assisted laser desorption/ionization time-of-flight mass spectrometer results and ClinProTools software for 25 S. argenteus and 25 methicillin-susceptible S. aureus (MSSA). The performance of the classification model was validated against 72 S. argenteus and 72 MSSA isolates. Results: With cluster analysis and classification model, differentiation of 72 S. argenteus from 72 MSSA had 100.0% accuracy by chemical extraction method and 87.5% sensitivity and 100.0% specificity by direct smear method. Conclusion: The classification model could accurately differentiate S. argenteus from MSSA.