Tracking the evolution of the two successful CC59 methicillin-resistant Staphylococcus aureus clones in Taiwan: the divergence time of the two clades is estimated to be the 1980s

Effective treatment of a broad-host-range lytic phage SapYZU15 in eliminating Staphylococcus aureus from subcutaneous infection

Multidrug resistance (MDR) Staphylococcus aureus is frequently isolated from food products, and can cause severe clinical infection. Bacteriophage (phage) therapy is a promising biocontrol agent against MDR S. aureus in food contamination and clinical infections. In this study, the antimicrobial susceptibility of 47 S. aureus isolates from three swine farms, two slaughterhouses, and four markets (Yangzhou, China) were evaluated. The biological characteristics of four lytic S. aureus phages were compared and the lytic activity of phage SapYZU15 against MDR S. aureus was assessed using milk, fresh pork and a mouse model of subcutaneous abscess. The results showed that 28 S. aureus isolates (59.6%, 28/47) exhibited multiple antibiotic resistance to at least three different classes of antibiotics. Compared to SapYZU01, SapYZU02, and SapYZU03, SapYZU15 had a shorter latent period (10 min), larger burst size (322.00 PFU/cell), broader host range, wider temperature stability (-80 to 50 °C), and pH stability. Furthermore, SapYZU15 significantly reduces the counts of S. aureus in milk and pork (5.69 and 1.16 log colony-forming unit/mL, respectively) at 25 °C and controls the growth of S. aureus at 4 °C. Compared to the mice infected with S. aureus MRSA JCSC 4744 and cocktail (S. aureus YZUsa1, YZUsa4, YZUsa12, YZUsa14, and MRSA JCSC 4744), treatment with SapYZU15 led to faster tissue healing, less weight loss, and lower viable S. aureus counts in the murine abscess model. Moreover, prevention with SapYZU15 effectively inhibited abscess formation through a synergistic effect with pro-inflammatory cytokines. Consequently, our results suggest that SapYZU15 is an effective strategy for controlling S. aureus contamination in food products, and possesses an immense potential to treat and prevent clinic infection caused by MDR S. aureus strains. The interactions and mechanisms between SapYZU15 and its bacterial host differed depending on the model, temperature, and multiplicity of infection (MOI).

Genomic Insights of First ermB-Positive ST338-SCCmecVT/CC59 Taiwan Clone of Community-Associated Methicillin-Resistant Staphylococcus aureus in Poland

We report the first Polish representative of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA), lukS/F-PV-positive, encoding the ermB gene, as a genetic determinant of constitutive resistance to macrolides, lincosamides, and streptogramin B antibiotics, cMLS-B. This is the first detection of the CA-MRSA strain responsible for nosocomial infection in the Warsaw Clinical Hospital. Resistance to β-lactams associates with a composite genetic element, SCCmec cassette type V_T (5C2&5). We assigned the strain to sequence type ST338 (single-locus variant of ST59), clonal complex CC59, spa-type t437, and agr-type I. Genomic-based comparison was designated SO574/12 as an international Taiwan clone, which has been so far described mainly in the Asia-Pacific region. The ermB gene locates on the chromosome within the 14,690 bp mobile element structure, i.e., the MES_PM1-like structure, which also encodes aminoglycoside- and streptothricin-resistance genes. The MES_PM1-like structure is a composite transposon containing Tn551, flanked by direct repeats of IS1216V insertion sequences, which probably originates from Enterococcus. The ermB is preceded by the 273 bp regulatory region that contains the regulatory 84 bp ermBL ORF, encoding the 27 amino acid leader peptides. The latest research suggests that a new leader peptide, ermBL2, also exists in the ermB regulatory region. Therefore, the detailed function of ermBL2 requires further investigations.

A Possible Role of Insertion Sequence IS1216V in Dissemination of Multidrug-Resistant Elements MESPM1 and MES6272-2 between Enterococcus and ST59 Staphylococcus aureus

Sequence type 59 (ST59) is the dominant type of community-associated methicillin-resistant Staphylococcus aureus (MRSA) in Taiwan. Previously, we reported that ST59 MRSA harbors enterococcal IS1216V-mediated multidrug-resistant composite transposons MESPM1 or MES6272-2. The MES were found to have a mosaic structure, largely originating in enterococci and partly native to S. aureus. The current study aimed to track the origin of the MES and how they disseminated from enterococci to ST59 S. aureus. A total of 270 enterococcal isolates were analyzed, showing that two ST64 Enterococcus faecalis isolated in 1992 and 11 clonal complex 17 Enterococcus faecium harbored MESPM1-like and MES6272-2-like structures, respectively. Sequence analysis revealed that ST64 E. faecalis strain N48 acquired the MESPM1-like structure on the plasmid pEflis48. The pEflis48 harbored the enterococci-originated region (erythromycin, kanamycin, and streptomycin resistances) and the S.aureus-originated region (chloramphenicol resistance) of MESPM1 but was separated by the replication region of the plasmid. Homologous recombination between the two direct repeats of IS1216V resulted in excision of the replication region of the plasmid to regenerate MESPM1. The p4780-1 and pV19 of E. faecium carried MES6272-2-like structures with IS1216V, albeit with multiple insertions by other insertion sequences. The findings show that IS1216V plays important roles in bidirectional gene transfer of multidrug resistance between enterococci and S. aureus.

Identification of key interactions between SARS-CoV-2 main protease and inhibitor drug candidates

The number of cases of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection (COVID-19) has reached over 114,000. SARS-CoV-2 caused a pandemic in Wuhan, China, in December 2019 and is rapidly spreading globally. It has been reported that peptide-like anti-HIV-1 drugs are effective against SARS-CoV Main protease (Mpro). Due to the close phylogenetic relationship between SARS-CoV and SARS-CoV-2, their main proteases share many structural and functional features. Thus, these drugs are also regarded as potential drug candidates targeting SARS-CoV-2 Mpro. However, the mechanism of action of SARS-CoV-2 Mpro at the atomic-level is unknown. In the present study, we revealed key interactions between SARS-CoV-2 Mpro and three drug candidates by performing pharmacophore modeling and 1 μs molecular dynamics (MD) simulations. His41, Gly143, and Glu166 formed interactions with the functional groups that were common among peptide-like inhibitors in all MD simulations. These interactions are important targets for potential drugs against SARS-CoV-2 Mpro.