Molecular analysis of immune evasion cluster (IEC) genes and intercellular adhesion gene cluster (ICA) among methicillin-resistant and methicillin-sensitive isolates of Staphylococcus aureus

Whole genome sequencing of methicillin-resistant Staphylococcus aureus clinical isolates from Terengganu, Malaysia, indicates the predominance of the EMRSA-15 (ST22-SCCmec IV) clone

Despite the importance of methicillin-resistant Staphylococcus aureus (MRSA) as a priority nosocomial pathogen, the genome sequences of Malaysian MRSA isolates are currently limited to a small pool of samples. Here, we present the genome sequence analyses of 88 clinical MRSA isolates obtained from the main tertiary hospital in Terengganu, Malaysia in 2016-2020, to obtain in-depth insights into their characteristics. The EMRSA-15 (ST22-SCCmec IV) clone of the clonal complex 22 (CC22) lineage was predominant with a total of 61 (69.3%) isolates. Earlier reports from other Malaysian hospitals indicated the predominance of the ST239 clone, but only two (2.3%) isolates were identified in this study. Two Indian-origin clones, the Bengal Bay clone ST772-SCCmec V (n = 2) and ST672 (n = 10) were also detected, with most of the ST672 isolates obtained in 2020 (n = 7). Two new STs were found, with one isolate each, and were designated ST7879 and ST7883. From the core genome phylogenetic tree, the HSNZ MRSA isolates could be grouped into seven clades. Antimicrobial phenotype-genotype concordance was high (> 95%), indicating the accuracy of WGS in predicting most resistances. Majority of the MRSA isolates were found to harbor more than 10 virulence genes, demonstrating their pathogenic nature.

Genomic epidemiology and characterization of Staphylococcus aureus isolates from raw milk in Jiangsu, China: emerging broader host tropism strain clones ST59 and ST398

Staphylococcus aureus is highly pathogenic and can cause disease in both humans and domestic animals. The aim of this study was to investigate the genomic epidemiology of S. aureus isolates from raw milk in Jiangsu Province, China, to identify predominant lineages and their associated genomic and phenotypic characteristics. In this study, we identified 117 S. aureus isolates collected from 1,062 samples in Jiangsu Province between 2021 and 2022. Based on whole-genome sequencing (WGS) data from 117 S. aureus isolates, molecular analyses indicated CC1-ST1 (26.50%, 31/117), CC97-ST97 (18.80%, 22/117), CC398-ST398 (10.26%, 12/117), CC8-ST630 (7.69%, 9/117) and CC59-ST59 (2.56%, 3/117) were the major lineages. The prevalence of mecA-positive strains was 11.11%. Four methicillin-resistant S. aureus (MRSA) lineages were found, including MRSA-ST59-t172 (n = 3), OS-MRSA-ST398-t011 (n = 1), MRSA-ST630-t2196 (n = 2) and OS-MRSA-ST630-t2196 (n = 7). Phenotypic resistance to penicillin (30.77%, 36/117), ciprofloxacin (17.09%, 20/117) and erythromycin (15.38%, 18/117) was observed which corresponded with resistance genotypes. All of the isolates could produce biofilms, and 38.46% (45/117) of isolates had invasion rates in mammary epithelial cells (MAC-T) of greater than 1%. Interestingly, most biofilm-producing and invading isolates harbored ebp-icaA-icaB-icaC-icaR-clfA-clfB-fnbA-fnbB-sdrC-sdrD-sdrE-map-can (27.35%, 32/117) and ebp-icaA-icaB-icaC-icaD-icaR-clfA-clfB-fnbA-fnbB-sdrC-sdrD-sdrE-map (33.33%, 39/117) adherence-associated gene patterns and belonged to lineages CC1 and CC97, respectively. Virulence factor assays showed that 47.01% of the isolates contained at least enterotoxin genes. Isolates harboring the immune evasion cluster (IEC) genes (sea, sak, chp, and scn) were predominantly categorized as STs 464, 398, and 59. IEC-positive ST398 and ST59 isolates contained a very high proportion of virulence genes located on prophages, whereas most IEC-negative ST398 clade isolates carried broad-spectrum drug resistance genes. Meanwhile, the IEC-positive ST398 clade showed a close genetic relationship with isolates from the pork supply chain and hospital surgical site infections. MRSA-ST59 strains showed the closest genetic relationship with an isolate from quick-frozen products. High-risk livestock-associated strains ST398 and MRSA-ST59 were detected in raw milk, indicating a potential public health risk of S. aureus transmission between livestock and humans. Our study highlights the necessity for S. aureus surveillance in the dairy industry.

Anthroponotic-Based Transfer of Staphylococcus to Dog: A Case Study

Although usually harmless, Staphylococcus spp. can cause nosocomial and community-onset skin and soft tissue infections in both humans and animals; thus, it is considered a significant burden for healthcare systems worldwide. Companion animals have been identified as potential reservoirs of pathogenic Staphylococcus with specific reference to Methicillin Resistant Staphylococcus aureus (MRSA). In this study, we investigated the circulation and the genetic relationships of a collection of Staphylococcus spp. isolates in a family composed of four adults (a mother, father, grandmother, and grandfather), one child, and a dog, which were sampled over three years. The routes of transmission among humans and between humans and the dog werelyzed. The results displayed the circulation of many Staphylococcus lineages, belonging to different species and sequence types (ST) and being related to both human and pet origins. However, among the observed host-switch events, one of them clearly underpinnthroponotic route from a human to a dog. This suggests that companion animals can potentially have a role as a carrier of Staphylococcus, thus posing a serious concern about MRSA spreading within human and animal microbial communities.

Antibacterial Activity of Chinese Red Propolis against Staphylococcus aureus and MRSA

The antibacterial activity of propolis has long been of great interest, and the chemical composition of propolis is directly dependent on its source. We recently obtained a type of propolis from China with a red color. Firstly, the antibacterial properties of this unusual propolis were determined against Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA). Studies on its composition identified and quantified 14 main polyphenols of Chinese red propolis extracts (RPE); quantification was carried out using liquid chromatography triple quadrupole tandem mass spectrometry (LC-QQQ-MS/MS) and RPE was found to be rich in pinobanksin, pinobanksin-3-acetate, and chrysin. In vitro investigations of its antibacterial activity revealed that its activity against S. aureus and MRSA is due to disruption of the cell wall and cell membrane, which then inhibits bacterial growth. Despite its similar antibacterial activities against S. aureus and MRSA, metabolomic analysis further revealed the effects of RPE on bacteria metabolism were different. The untargeted metabolomic results showed that a total of 7 metabolites in 12 metabolic pathways had significant changes (Fold change > 2, p < 0.05 *) after RPE treatment in S. aureus, while 11 metabolites in 9 metabolic pathways had significant changes (Fold change > 2, p < 0.05 *) after RPE treated on MRSA. Furthermore, RPE downregulated several specific genes related to bacterial biofilm formation, autolysis, cell wall synthesis, and bacterial virulence in MRSA. In conclusion, the data obtained indicate that RPE may be a promising therapeutic agent against S. aureus and MRSA.

Detection, molecular characterization, and antibiogram of multi-drug resistant and methicillin-resistant Staphylococcus aureus (MRSA) isolated from pets and pet owners in Malaysia

BACKGROUND

The emergence of multidrug-resistant strains such as methicillin-resistant Staphylococcus aureus (MRSA) and multidrug-resistant Staphylococcus aureus (MDRSA) in animals and humans with continuous contact are a great zoonotic concern.

AIMS

This cross-sectional study was performed to investigate the carriage rate, genotypic characteristics, and to determine the antibiogram of S. aureus isolated from pets and pet owners in Malaysia.

METHODS

Nasal and oral swab samples from 40 cats, 30 dogs, and 70 pet owners were collected through convenient sampling. Presumptive colonies on mannitol salt agar were subjected to biochemical identification. S. aureus and MRSA were confirmed by PCR detection of nuc and mecA genes, respectively. Molecular profiles for antimicrobial resistance and virulence genes in S. aureus were also determined. The antibiogram was carried out via Kirby-Bauer test using 18 antibiotics.

RESULTS

17.5% of cats, 20% of dogs, and 27% of pet owners were S. aureus positive. MRSA was also detected in dogs, and pet owners. S. aureus isolates displayed high resistance against penicillin (72.7%), and amoxicillin/clavulanate (66.7%). 39.4% of S. aureus isolates showed multidrug-resistance traits, phenotypically. Molecular characterization of S. aureus revealed the presence of mecA, tetk, tetL, ermA, ermB, ermC, msrA, scn, chp, sak, sep, and sea genes.

CONCLUSION

This study showed the emergence of MRSA and MDRSA in pets and pet owners in Malaysia. The antibiogram findings showed resistance of S. aureus to multiple antibiotics. Furthermore, molecular analysis of immune evasion cluster (IEC) strongly suggests the spread of animal-adapted S. aureus lineages among pets and pet owners.

Genome-Wide Profiling of Enterotoxigenic Staphylococcus aureus Strains Used for the Production of Naturally Contaminated Cheeses

Staphylococcus aureus is a major human pathogen and an important cause of livestock infections. More than 20 staphylococcal enterotoxins with emetic activity can be produced by specific strains responsible for staphylococcal food poisoning, one of the most common food-borne diseases. Whole genome sequencing provides a comprehensive view of the genome structure and gene content that have largely been applied in outbreak investigations and genomic comparisons. In this study, six enterotoxigenic S. aureus strains were characterised using a combination of molecular, phenotypical and computational methods. The genomes were analysed for the presence of virulence factors (VFs), where we identified 110 genes and classified them into five categories: adherence (n = 31), exoenzymes (n = 28), genes involved in host immune system evasion (n = 7); iron uptake regulatory system (n = 8); secretion machinery factors and toxins' genes (n = 36), and 39 genes coding for transcriptional regulators related to staphylococcal VFs. Each group of VFs revealed correlations among the six enterotoxigenic strains, and further analysis revealed their accessory genomic content, including mobile genetic elements. The plasmids pLUH02 and pSK67 were detected in the strain ProNaCC1 and ProNaCC7, respectively, carrying out the genes sed, ser, and selj. The genes carried out by prophages were detected in the strain ProNaCC2 (see), ProNaCC4, and ProNaCC7 (both positive for sea). The strain ProNaCC5 resulted positive for the genes seg, sei, sem, sen, seo grouped in an exotoxin gene cluster, and the strain ProNaCC6 resulted positive for seh, a transposon-associated gene. The six strains were used for the production of naturally contaminated cheeses which were tested with the European Screening Method for staphylococcal enterotoxins. The results obtained from the analysis of toxins produced in cheese, combined with the genomic features represent a portrait of the strains that can be used for the production of staphylococcal enterotoxin-positive cheese as reference material.

Virulence of methicillin-resistant Staphylococcus aureus modulated by the YycFG two-component pathway in a rat model of osteomyelitis

Objectives

Methicillin-resistant Staphylococcus aureus (MRSA) strains present an urgent medical problem in osteomyelitis cases. Our previous study indicated that the YycFG two-component regulatory pathway is associated with the bacterial biofilm organization of MRSA strains. The aim of this study was to investigate the regulatory roles of ASyycG in the bacterial biofilm formation and the pathogenicity of MRSA strains using an antisense RNA strategy.

Methods

An ASyycG-overexpressing MRSA clinical isolate was constructed. The bacterial growth was monitored, and the biofilm biomass on bone specimens was examined using scanning electron microscopy and confocal laser scanning microscopy. Furthermore, quantitative RT-PCR (QRT-PCR) analysis was used to measure the expression of yycF/G/H and icaA/D in the MRSA and ASyycG strains. The expression of the YycG protein was quantified by Western blot assays. We validated the role of ASyycG in the invasive ability and pathogenicity of the strains in vivo using histology and peptide nucleic acid fluorescent in situ hybridization.

Results

The results showed that overexpression of ASyycG lead to a reduction in biofilm formation and exopolysaccharide (EPS) synthesis compared to the control MRSA strains. The ASyycG strains exhibited decreased expression of the yycF/G/H and icaA/D genes. Furthermore, Western blot data showed that the production of the YycG protein was inhibited in the ASyycG strains. In addition, we demonstrated that ASyycG suppressed the invasive ability and pathogenicity of the strain in vivo using an SPF (specific pathogen free) rat model.

Conclusion

In summary, the overexpression of ASyycG leads to a reduction in biofilm formation and bacterial pathogenicity in vivo, which provides a potential target for the management of MRSA-induced osteomyelitis.

Genetic characterization of two vancomycin-resistant Staphylococcus aureus isolates in Kerman, Iran

Aim

The aim of this study was the genetic characterization of two clinical vancomycin-resistant Staphylococcus aureus (VRSA) isolates.

Materials and methods

Resistance to vancomycin was determined by phenotypic method. PCR was used for detection of mecA, vanA, ermA, ermB, ermC, msrA/B, aph(2")-Ic, aph(3')-IIIa, pvl, Immune Evasion Cluster [sea, sep, chip, sak and scn] genes and biofilm operon icaABCD. On the other hand, multilocus sequence typing and agr typing methods were performed for the determination of clonal relationship and van operon was detected and sequenced.

Results

Vancomycin-resistant Staphylococcus aureus strain 1 (VRSA-1) was positive for vanA, ermA, ermC, aph(2")-Ic, aph(3')-IIIa, sea, sep, icaD genes, belonging to agr type I; SCCmec type III; spa type t030; and ST239. However, the genetic characterization of Vancomycin-resistant Staphylococcus aureus strain 2 (VRSA-2) revealed the presence of various types of resistance genes vanA, ermA, ermC, aph(2")-Ic, aph(3')-IIIa, sea, icaD, relating to agr type I; SCCmec type III; spa type t459; and ST239. The presence of transposon Tn1546 was determined by PCR sequencing.The Basic Local Alignment Search Tool analysis of van operon in the VRSA isolates showed 99.6% sequence homology to Tn1546 in vancomycin-resistant enterococci, indicating the vanA operon has an enterococcal origin.

Conclusion

In conclusion, the ST239 is one of the most common clones of MRSA isolates which involved the hospital-associated infections, therefore, the emergence of VRSA isolates with ST239 increased the spread of resistance to vancomycin in the hospital settings.

Genetic characterization of two vancomycin-resistant Staphylococcus aureus isolates in Kerman, Iran

Aim

The aim of this study was the genetic characterization of two clinical vancomycin-resistant Staphylococcus aureus (VRSA) isolates.

Materials and methods

Resistance to vancomycin was determined by phenotypic method. PCR was used for detection of mecA, vanA, ermA, ermB, ermC, msrA/B, aph(2”)-Ic, aph(3ʹ)-IIIa, pvl, Immune Evasion Cluster [sea, sep, chip, sak and scn] genes and biofilm operon icaABCD. On the other hand, multilocus sequence typing and agr typing methods were performed for the determination of clonal relationship and van operon was detected and sequenced.

Results

Vancomycin-resistant Staphylococcus aureus strain 1 (VRSA-1) was positive for vanA, ermA, ermC, aph(2”)-Ic, aph(3ʹ)-IIIa, sea, sep, icaD genes, belonging to agr type I; SCCmec type III; spa type t030; and ST239. However, the genetic characterization of Vancomycin-resistant Staphylococcus aureus strain 2 (VRSA-2) revealed the presence of various types of resistance genes vanA, ermA, ermC, aph(2”)-Ic, aph(3ʹ)-IIIa, sea, icaD, relating to agr type I; SCCmec type III; spa type t459; and ST239. The presence of transposon Tn1546 was determined by PCR sequencing.The Basic Local Alignment Search Tool analysis of van operon in the VRSA isolates showed 99.6% sequence homology to Tn1546 in vancomycin-resistant enterococci, indicating the vanA operon has an enterococcal origin.

Conclusion

In conclusion, the ST239 is one of the most common clones of MRSA isolates which involved the hospital-associated infections, therefore, the emergence of VRSA isolates with ST239 increased the spread of resistance to vancomycin in the hospital settings.