Panton-Valentine leukocidin (PVL) isoforms among Staphylococcus aureus lineages isolated from hospitals in Rio de Janeiro, Brazil

Abstract

Panton-Valentine leukocidin (PVL) is a Staphylococcus aureus virulence factor codified by lukSF-PV genes. Single-nucleotide polymorphisms (SNPs) at lukSF-PV genes can lead to two PVL sequence variants (R and H) generating different PVL isoforms. This study analyzed lukSF-PV genes SNPs among four different clonal lineages (STs/CC 1, 5, 8, and 30) of nine S. aureus isolated at Brazilian hospitals. The sequenced products showed SNPs at seven sites (positions 121, 470, 527, 663, 856, 1396, and 1729), leading to non-synonymous substitutions in all isolates investigated. Our findings showed new R and H isoforms variants in S. aureus isolated in Brazil and suggest a possible relationship between H2b isoform and the ST30/CC30 lineage. Keywords Staphylococcus aureus. Panton-Valentine leukocidin (PVL) isoforms. Brazilian lineages Panton-Valentine leukocidin (PVL) is a bicomponent and pore-forming toxin that targets phagocytes, leading to membrane damage and cell death in vitro, often associated with recurrent Staphylococcus aureus skin and soft tissue infections and necrotizing pneumonia [1]. PVL can be produced by both methicillin-susceptible (MSSA) and methicillinresistant S. aureus (MRSA) isolates [1, 2]. The USA300/ ST8 MRSA is the commonly PVL-positive lineage found in the USA [3], while in Latin American countries, including Brazil, the USA1100/ST30 MRSA is frequently reported [2, 4]. PVL-codifying genes, lukS-PV and lukF-PV, are carried by a temperate prophage and may be transferred from one isolate to another via phage transduction [5]. Although the PVL genes are considered highly conserved [6], it was demonstrated at least 22 points mutations or SNPs (single-nucleotide polymorphism) in both lukS-PV and lukF-PV [6-11] (Table 1). Based on the nucleotide substitution, the PVL proteins were classified in two major sequence variants of lukSF-PV, named as H or R variants [7]. Despite the recognized role of PVL on S. aureus disease severity [12], the influence of PVL isoforms on protein toxicity and disease outcome remains unknown. Molecular modeling studies suggested that the R isoform may alter pore formation and increase PVL leukotoxicity [7]. On the other hand, some authors suggested that the protein isoform does not influence PVL toxicity, since H and R isoforms could be found at similar frequencies among S. aureus isolates recovered from invasive diseases [6, 13]. However, it is important to point that mutations at virulence-related genes, besides increasing the molecular diversity of bacterial isolates, may lead to gain or loss of protein function. Due to the importance of PVL on S. aureus disease outcome [12], the comprehension of PVL structure and diversity is crucial to understand the microbial pathogenicity and may help the improvement of specific therapeutic drug target design. Moreover, there is no study regarding PVL isoforms of PVLpositive S. aureus isolates from Brazil. Thus, the present study aimed to determine the PVL isoforms of S. aureus previously isolated from different hospitals in Rio de Janeiro [...

Seed treatment with prodigiosin controls damping-off of cucumber caused by Pythium ultimum

“…Manufacturer (Epicentre Biotechnologies, Madison, WI) supplied primers designed to the 5′ and 3′ flanking regions of mini-Tn5 Km, and oriented to sequence 5′ up-stream and 3′ down-stream, were used (KAN-2 FP-1 Forward Primer 5′-ACCTACAACAAAGCTCTCATCAACC-3′; KAN-2 RP-1 Reverse Primer 5′-GCAATGTAACATCAGAGATTTTGAG-3′). Whole genome sequencing was recently conducted with strain N4-5 (Ferreira et al 2020 ) and the genome map can be downloaded from NCBI bioproject PRJNA477367.…”