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.

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.

Staphylococcus singaporensis sp. nov., a new member of the Staphylococcus aureus complex, isolated from human clinical specimens.

Staphylococcus argenteus and Staphylococcus schweitzeri are the newest members of the Staphylococcus aureus complex. The number of clinical reports attributed to these new S. aureus complex members is limited. In a retrospective clinical laboratory study conducted over a 4-month period investigating the prevalence of S. argenteus and S. schweitzeri, a total of 43 isolates were selected. Phylogeny based on core-gene multilocus sequence typing (MLST) analysis confirmed that 37 were S. argenteus but a genetically distinct clade of six isolates was identified. Digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) analyses further supported the classification of these six isolates as a separate species. When compared to S. aureus complex reference genomes, the ANI values were ≤94 % and the dDDH values were <53 %. Based on the seven-gene S. aureus MLST scheme, the six isolates belong to five novel allelic profiles (ST6105, ST6106, ST6107, ST6108 and ST109). Their clinical infection features were similar to S. aureus. Skin and soft tissue infections presented in four out of the six cases. Routine clinical diagnostic identification using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and biochemical profiling does not differentiate these new members from the rest of the complex. Genotypic analysis suggests that the six isolates belong to a novel species, Staphylococcus singaporensis sp. nov. with isolate SS21T (=DSM 111408T=NCTC14419T) designated as the type strain.

Characterization of Staphylococcus roterodami sp. nov., a new species within the Staphylococcus aureus complex isolated from a human foot infection.

This article introduces a new Staphylococcus species cultivated from a human foot wound infection in a Dutch traveller returning from the island of Bali, Indonesia: Staphylococcus roterodami sp. nov. Based on the genomic sequence, there is strong molecular evidence for assigning the strain to a novel species within the S. aureus complex. Differences in cellular fatty acid spectrum and biochemical tests underline these findings. Its ecological niche and pathogenicity require further study. The type strain is DSM111914T (JCM34415T).

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.

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.

Identification and characterization of two novel superantigens among Staphylococcus aureus complex.

Staphylococcal enterotoxins (SEs), also known as superantigens, play a very important role in infections and food poisoning caused by Staphylococcus aureus. Recently, S. argenteus and S. schweitzeri were recognized as novel species closely related to S. aureus. In this study of these three species, it was found that two putative SE genes were located upstream of some vSaß pathogenicity islands and the deduced amino acid sequences showed < 65.3% identity with those of known SEs. The related proteins, designated staphylococcal enterotoxin-like toxin 26 (SEl26) and 27 (SEl27), were identified and characterized among the three species. The mRNAs encoding SEl26 and SEl27 were expressed during all the growth phases. Recombinant SEl26 and SEl27 exhibited superantigenic activity in human peripheral blood mononuclear cells and mouse splenocytes by examining cell proliferation and cytokine production. Interestingly, these two genes were present universally in S. argenteus sequence type 2250 with clinical importance. Meanwhile, SEl27 variants from different species showed differential sensitivity to human peripheral blood mononuclear cells, which corresponded to the primary bacterial species hosts. It was demonstrated from these results that SEl26 and SEl27 were characterized to be two novel SE toxins and some SEs evolved along with the bacteria when the organisms adapted the hosts' immune systems.