Clinical characteristics and molecular analysis of USA300 and ST 764 methicillin-resistant Staphylococcus aureus isolates from outpatients in Japan by PCR-Based open reading frame typing

Assessing the discriminability of PCR-based open reading frame typing versus single-nucleotide polymorphism analysis via draft whole-genome sequencing of methicillin-resistant Staphylococcus aureus in nosocomial transmission analysis

Phylogenetic analysis based on single-nucleotide polymorphism (SNP)-based through whole-genome sequencing is recognized as the standard method for probing nosocomial transmission. However, the application of WGS is constrained by the high cost of equipment and the need for diverse analysis tools, which limits its widespread use in clinical laboratory settings. In Japan, the prevalent use of PCR-based open reading frame typing (POT) for tracing methicillin-resistant Staphylococcus aureus (MRSA) transmission routes is attributed to its simplicity and ease of use. Although POT's discriminatory power is considered insufficient for nosocomial transmission analysis, conclusive data supporting this notion is lacking. This study assessed the discriminatory capabilities of SNP analysis and POT across 64 clinical MRSA strains. All 21 MRSA strains of ST5/SCCmec IIa, having more than 16 SNPs, demonstrated distinct clones. Conversely, two strains shared the same POT number and were identified as group A. Among the 12 MRSA strains of ST8/SCCmec IVl with over nine SNPs, five fell into POT group B, and five into POT group C. All four MRSA strains of ST8/SCCmec IVa were classified into POT group D, although they included strains with more than 30 SNPs. Among the 27 MRSA strains of ST1/SCCmec IVa, 14 were classified into POT group E. However, except for two clusters (each comprising two or three strains), all had SNP counts >10 (Fig. 1-D). SNP analysis of MRSA in CC1/SCCmec IV showed that several strains had the same number of SNPs in POT number (106-183-37), even among bacteria with >100 SNPs, indicating POT's limited use in detailed nosocomial transmission analysis.

Genotypic Shift and Diversification of MRSA Blood Stream Isolates in a University Hospital Setting: Evidence from a 12-Year Observational Study

There have been few reports regarding the long-term trends in the genotypes of methicillin-resistant Staphylococcus aureus (MRSA) bloodstream isolates. Therefore, this study was performed to investigate the longitudinal trends in the genotypes of MRSA bloodstream isolates obtained from hospitalized patients during a 12-year study period from 2010 to 2021 at a tertiary care university hospital. Over the 12-year period from 2010 to 2021, we conducted a genetic investigation focusing on 245 MRSA strains isolated from the blood of hospitalized patients. The genotypes of the MRSA bloodstream isolates were determined by Staphylococcal Cassette Chromosome mec (SCCmec) typing, accessory gene regulator (agr) typing, PCR-based ORF typing (POT), and multilocus sequence typing (MLST). Strains with the same POT type detected in two or more isolates were designated as epidemic clones, while strains without a common POT type were classified as sporadic clones. Until 2015, isolates with SCCmec II/agr II were prevalent, but isolates with SCCmec IV/agr III increased from 2016. A total of 128 strains (52%) were identified as epidemic clones, while 117 strains (48%) were classified as sporadic clones. The detection rate of sporadic clones increased significantly since 2016 (p < 0.05). The epidemic clones were classified into three clusters, with MRSA of clonal complex (CC) 1 being prominent after 2016. This study showed that the genotypes of MRSA bloodstream isolates underwent a shift from SCCmec II/agr II type to SCCmec IV/agr III type, with a notable increase in MRSA of CC1, after 2016. There was a significant increase in the proportion of sporadic strains among the isolates, suggesting the diversification of genotypes.

Importance of Toxin Genes and Polymerase Chain Reaction-Based Open Reading Frame Type Analyses for Severe Staphylococcus aureus Infection in Children

This study analyzed 26 Staphylococcus aureus strains, including 16 methicillin-resistant S. aureus (MRSA) and 10 methicillin-susceptible S. aureus (MSSA), collected from eight medical institutions in the Chiba Prefecture that requested a toxin gene analysis between 2015 and 2021. A total of 14 Panton-Valentine leukocidin (PVL) positive strains were identified, including MSSA. PVL-positive strains were classified into seven types according to polymerase chain reaction-based open reading frame typing (POT); of these types, three POT MRSA strains have not been previously reported, and one has been previously reported as PVL-negative. Some strains tested positive for both PVL and toxic shock syndrome toxin 1. One POT type was identified in both PVL-positive and PVL-negative strains. To the best of our knowledge, this is the first report on the regional spread of highly pathogenic S. aureus strains based on the POT method in children from multiple medical institutions. This method is useful for estimating the spread of toxin gene-carrying strains in the community owing to its association with toxin genes. As the number of PVL-positive strains in Japan increases, it is important to analyze the isolates of severe S. aureus infections in children by combining toxin gene analyses with the POT method.

Estimated medical costs of methicillin-resistant Staphylococcus aureus infection classified by polymerase chain reaction-based open reading frame typing in Japan

This retrospective, observational cohort study investigated the economic impact of genotype by classifying methicillin-resistant Staphylococcus aureus (MRSA) by using the polymerase chain reaction-based open reading frame typing (POT) method. Using administrative claims and bacteriological data for April 2016 to March 2021 from the University of Yamanashi Hospital, we ascertained the POT1 numbers and classified MRSA as either "hospital-derived" or "community-derived". We defined MRSA-associated medical practices and estimated the associated medical costs. After applying inverse probability of treatment weighting (IPTW)-based adjustment for patient characteristics between the two groups, we estimated the differences in medical costs during the "total therapy period" (defined as the interval from specimen submission to Day 42 after the susceptibility report) and the "definitive therapy period" (defined as the interval from susceptibility reporting to Day 42). Among the 135 MRSA-infected patients, 54 and 81 were classified as having hospital-derived and community-derived MRSA infections, respectively. Significant differences in patient characteristics were observed with regard to age (p = 0.0478), sex (p = 0.0422), surgery (p = 0.0349), chemotherapy (p = 0.0457) and immunosuppressive drug use (p = 0.0222). The median duration of the definitive therapy was 29 and 27 days, and the mortality rate during this period was 11% and 5% for the hospital-derived and community-derived types, respectively. After IPTW-based adjustment, the medical costs for the total therapy period were 324,480 and 296,462 Japanese yen (JPY) per patient for the hospital-derived and community-derived types, respectively, whereas the medical costs for the definitive therapy period were 279,635 and 256,542 JPY per patient for the hospital-derived and community-derived types, respectively. No statistically significant difference was detected (p = 0.5813 and p = 0.6355, respectively). In this study, MRSA healthcare costs were compared according to the POT scores, and no statistically significant differences were observed between hospital-derived and community-derived MRSA infections.

Residual Tau-Fluvalinate in Honey Bee Colonies Is Coupled with Evidence for Selection for Varroa destructor Resistance to Pyrethroids

Varroa destructor is considered one of the most devastating parasites of the honey bee, Apis mellifera, and a major problem for the beekeeping industry. Currently, the main method to control Varroa mites is the application of drugs that contain different acaricides as active ingredients. The pyrethroid tau-fluvalinate is one of the acaricides most widely used in beekeeping due to its efficacy and low toxicity to bees. However, the intensive and repetitive application of this compound produces a selective pressure that, when maintained over time, contributes to the emergence of resistant mites in the honey bee colonies, compromising the acaricidal treatments efficacy. Here we studied the presence of tau-fluvalinate residues in hives and the evolution of genetic resistance to this acaricide in Varroa mites from honey bee colonies that received no pyrethroid treatment in the previous four years. Our data revealed the widespread and persistent tau-fluvalinate contamination of beeswax and beebread in hives, an overall increase of the pyrethroid resistance allele frequency and a generalized excess of resistant mites relative to Hardy-Weinberg equilibrium expectations. These results suggest that tau-fluvalinate contamination in the hives may seriously compromise the efficacy of pyrethroid-based mite control methods.

Association between the point-rating system used for oral health and the prevalence of Gram-negative bacilli in hematological inpatients: A retrospective cohort study

Gram-negative bacteremia is a major cause of death among hematology inpatients who require heavy-dose chemotherapy and hematopoietic stem cell transplantation. Gram-negative bacillus (GNB) is more likely to be detected when the oral health is poor. However, there is a dearth of studies on the relationship between oral assessment and prevalence of GNB in hematology inpatients.This retrospective study aimed to evaluate the relationship between the original point-rating system for oral health examinations (point-oral exam) and the prevalence of GNB in hematology inpatients at the hematology ward of the Yamanashi University Hospital. GNB was detected by cultivating samples from the sputum and blood of each patient.A total of 129 subjects underwent a medical checkup and point-oral exam. The sputum and blood culture results of 55 patients were included in this study. The total points of patients positive for GNB (n = 25, 45.5%) were significantly higher than those who were negative for GNB (total score: median, 25th, 75th, percentile; 6 [4, 7] vs 2 [1, 4]; P = .00016). Based on the receiver operating characteristic analysis, a cutoff score of 5 proved to be most useful to detect GNB.An oral evaluation with a cutoff value of 5 or higher in the point-oral exam might indicate the need for a more thorough oral management to prevent the development of systemic infections from GNB.