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Methicillin‐resistant Staphylococcus aureus (MRSA) has been recognised as an important cause of hospital‐associated infections in humans for several decades. MRSA is resistant to the most commonly used antibiotics. The MRSA lineage ST398 (MRSA ST398) has been recently described as a cause of infection for people occupationally exposed to pigs, by direct or indirect contact. MRSA ST398 can occasionally be introduced into hospitals as a result of community‐acquired human infections. To assess the occurrence and the diversity of MRSA in pig primary production, a European Union‐wide preliminary survey was carried out in parallel with a baseline survey on Salmonella spp. in holdings with breeding pigs to determine the prevalence of holdings positive for MRSA and MRSA ST398.

Staphylococcus aureus is one of the most important pathogens in humans as well as in livestock. Particularly, bovine mastitis caused by S. aureus is a serious issue in dairy farms due to disease recurrence. Here, cases of S. aureus-mediated intramammary infection occurring in the Miyagi Prefecture in Japan were monitored from May 2015 to August 2019; a total of 59 strains (49 from bovine milk and 10 from bulk milk) were obtained from 15 dairy farms and analyzed via sequence-based typing methods and antibiotic susceptibility tests. Two pairs of isolates were determined as recurrence cases from the same cows in distinct farms. The sequence type (ST), spa type, and coa type of each pair were the same: one pair showed ST705, t529, and VIb and the other showed ST352, t267, and VIc. In addition, the possession of toxin genes analyzed of each pair was exactly the same. Furthermore, seven oxacillin-sensitive clonal complex 398 isolates were obtained from a single farm. This is the first confirmed case of a Methicillin-Sensitive SA (MSSA) ST398 strain isolated from mastitis-containing cows in Japan. Our findings suggest that nationwide surveillance of the distribution of ST398 strains in dairy farms is important for managing human and animal health.

Abstract Background We conducted a longitudinal study to evaluate changes in the clinical presentation and epidemiology of Staphylococcus aureus bacteremia (SAB) in an academic, US medical center. Methods Consecutive patients with monomicrobial SAB were enrolled from January 1995 to December 2015. Each person’s initial bloodstream S. aureus isolate was genotyped using spa typing. Clonal complexes (CCs) were assigned using Ridom StaphType software. Changes over time in both the patient and bacterial characteristics were estimated with linear regression. Associations between genotypes or clinical characteristics and complications were estimated using multivariable regression models. Results Among the 2348 eligible participants, 54.2% had an implantable, foreign body of some type. This proportion increased significantly during the 21-year study period, by 0.96% annually (P = .002), as did comorbid conditions and acquisition outside of the hospital. Rates of any metastatic complication also significantly increased, by 0.94% annually (P = .019). Among the corresponding bloodstream S. aureus isolates, spa-CC012 (multi-locus sequence type [MLST] CC30), -CC004 (MLST CC45), -CC189 (MLST CC1), and -CC084 (MLST CC15) all significantly declined during the study period, while spa-CC008 (MLST CC8) significantly increased. Patients with SAB due to spa-CC008 were significantly more likely to develop metastatic complications in general, and abscesses, septic emboli, and persistent bacteremia in particular. After adjusting for demographic, racial, and clinical variables, the USA300 variant of spa-CC008 was independently associated with metastatic complications (odds ratio 1.42; 95% confidence interval 1.02–1.99). Conclusions Systematic approaches for monitoring complications of SAB and genotyping the corresponding bloodstream isolates will help identify the emergence of hypervirulent clones and likely improve clinical management of this syndrome. During 21 years of continuous enrollment in this prospective, observational cohort study of 2348 patients, bacterial genotypes, patient characteristics, and metastatic complication rates changed significantly. The emergence of the USA300 genotype was independently associated with an increase in metastatic complications.

A European Union‐wide baseline survey on methicillin‐resistant Staphylococcus aureus (MRSA) was conducted in 2008 in holdings with breeding pigs. A total of 1,600 holdings housing and selling mainly breeding pigs (breeding holdings), and 3,473 holdings housing breeding pigs and selling mainly pigs for fattening or slaughter (production holdings) from 24 Member States and two other European countries were included in the survey. Pooled dust samples collected from holdings were tested for MRSA. The likelihood of a limited set of holding‐level factors to be potentially associated with MRSA‐positive holdings were analysed by multiple regression analysis, separately for breeding and for production holdings. These analyses showed that the risk of holdings of being contaminated with MRSA increased as the number of breeding pigs in the holding increased, in both breeding and production holdings. Analyses at country‐level demonstrated a strong positive association between the prevalence of MRSA‐positive breeding holdings and MRSA‐positive production holdings, suggesting a vertical dissemination of MRSA between the holdings. A complementary country‐level analysis using TRAde Control and Expert System data on intra‐Community trade further disclosed strong positive associations between the prevalence of MRSA‐positive holdings with breeding pigs and the volume of imported breeding pigs, and a proxy for numbers of imported breeding pigs at risk of being colonised with MRSA. Further investigation of the diversity of MRSA Staphylococcus protein A types (spa‐types) showed that the distribution of spa‐types differed significantly between countries. Spa‐types belonging to lineages MRSA ST1, ST5, and ST8 tested negative for Panton‐Valentine leukocidin (PVL) toxin genes, suggesting that these strains were not related to the PVL‐positive MRSA strains known in human medicine. Further investigations of risk factors for MRSA holding contamination at country level, as well as investigations on prevention and intervention measures to contain MRSA contamination in pig holdings are recommended.

We aimed to determine the prevalence of antimicrobial resistance, carriage of Panton-Valentine leucocidin (PVL), and the clonal structure of MRSA isolates collected from skin and soft tissue infections at a tertiary care hospital in Pakistan. Between August 2021 and May 2022, 154 non-repetitive MRSA isolates were consecutively collected and characterized by antimicrobial susceptibility testing, SCCmec typing, spa typing, and detection of PVL by PCR. MLST clonal complexes (CCs) were inferred from spa type using the Based Upon Repeat Pattern (BURP) algorithm. High levels of resistance were observed to ciprofloxacin (85.7%), erythromycin (76.0%), sulfamethoxazole (68.8%), gentamicin (68.8%), fusidic acid (57.8%), tetracycline (55.8%), and clindamycin (42.2%). Clonal analysis revealed 16 lineages, with the most frequent being CC8-MRSA-IV (27.3%), PVL-positive “Bengal Bay” CC1/ST772-MRSA-V (26.0%), and CC1-MRSA-IV (16.2%). PVL was detected in 45.5% of isolates across multiple lineages. Our findings highlight the coexistence of high antimicrobial resistance and frequent PVL carriage among MRSA in Pakistan. Given the association of PVL with severe infections and the limited treatment options for multidrug-resistant strains, these data underscore a significant public health concern and the need for systematic surveillance and prudent antibiotic use.

108 isolates of Staphylococcus aureus, belonging to six large ribogroups according to the automated Ribo-Printer® system, were studied with two highly used molecular methods for epidemiological studies, namely multi-locus sequence typing (MLST) and spa typing, followed by BURP and eBURST v3 analysis for clustering spa types and sequence (ST) types. The aim was to evaluate whether automated ribotyping could be considered a useful screening tool for identifying S. aureus genetic lineages with respect to spa typing and MLST. Clarifying the relationship of riboprinting with these typing methods and establishing whether ribogroups fit single clonal complexes were two main objectives. Further information on the genetic profile of the isolates was obtained from agr typing and the search for the mecA, tst genes, and the IS256 insertion sequence. Automated ribotyping has been shown to predict spa clonal complexes and MLST clonal complexes. The high cost and lower discriminatory power of automated ribotyping compared to spa and MSLT typing could be an obstacle to fine genotyping analyzes, especially when high discriminatory power is required. On the other hand, numerous advantages such as automation, ease and speed of execution, stability, typeability and reproducibility make ribotyping a reliable method to be juxtaposed to gold standard methods.

Background. Strategies to prevent Staphylococcus aureus infection in hospitals focus on patient-to-patient transmission. We used whole-genome sequencing to investigate the role of colonized patients as the source of new S. aureus acquisitions, and the reliability of identifying patient-to-patient transmission using the conventional approach of spa typing and overlapping patient stay. Methods. Over 14 months, all unselected patients admitted to an adult intensive care unit (ICU) were serially screened for S. aureus. All available isolates (n = 275) were spa typed and underwent whole-genome sequencing to investigate their relatedness at high resolution. Results. Staphylococcus aureus was carried by 185 of 1109 patients sampled within 24 hours of ICU admission (16.7%); 59 (5.3%) patients carried methicillin-resistant S. aureus (MRSA). Forty-four S. aureus (22 MRSA) acquisitions while on ICU were detected. Isolates were available for genetic analysis from 37 acquisitions. Whole-genome sequencing indicated that 7 of these 37 (18.9%) were transmissions from other colonized patients. Conventional methods (spa typing combined with overlapping patient stay) falsely identified 3 patient-to-patient transmissions (all MRSA) and failed to detect 2 acquisitions and 4 transmissions (2 MRSA). Conclusions. Only a minority of S. aureus acquisitions can be explained by patient-to-patient transmission. Whole-genome sequencing provides the resolution to disprove transmission events indicated by conventional methods and also to reveal otherwise unsuspected transmission events. Whole-genome sequencing should replace conventional methods for detection of nosocomial S. aureus transmission.

Background: The bacterial species S. aureus is the most common causative agent of mastitis in cows in most countries with a dairy industry. The prevalence of infection caused by S. aureus ranges from 2% to more than 50%, and it causes 10–12% of all cases of clinical mastitis. Aim: The objective was to analyze 237 strains of S. aureus isolated from the milk of cows with subclinical mastitis regarding the spa, mecA, mecC and pvl genes and to perform spa and multi-locus sequence typing (MLST). Methods: Sequencing amplified gene sequences was conducted at Macrogen Europe. Ridom StaphType and BioNumerics software was used to analyze obtained sequences of spa and seven housekeeping genes. Results: The spa fragment was present in 204 (86.1%) of strains, while mecA and mecC gene were detected in 10 strains, and the pvl gene was not detected. Spa typing successfully analyzed 153 tested isolates (64.3%), confirming 53 spa types, four of which were new types. The most frequent spa type was t2678 (14%). MLST typed 198 (83.5%) tested strains and defined 32 different allele profiles, of which three were new. The most frequent allele profile was ST133 (20.7%). Six groups (G) and 15 singletons were defined. Conclusion: Taking the number of confirmed spa types and sequence types (STs) into account, it can be concluded that the strains of S. aureus isolated from the milk of cows with subclinical mastitis form a heterogenous group. To check the possible zoonotic potential of isolates it would be necessary to test the persons and other livestock on the farms.

Little is known about the structure of S. aureus population and the enterotoxin gene content in wild boar. In 1025 nasal swabs from wild boars, 121 S. aureus isolates were identified. Staphylococcal enterotoxin (SE) genes were identified in 18 isolates (14.9%). The seb gene was found in 2 S. aureus isolates, sec in 2 isolates, the see and seh genes were found in 4 and 11 isolates, respectively. The production of SEs was evaluated in bacteria grown in microbial broth. Concentration of SEB reached 2.70 µg/ml after 24 h and 4.46 µg/ml at 48 h. SEC was produced at 952.6 ng/ml after 24 h and 7.2 µg/ml at 48 h. SEE reached 124.1 ng/ml after 24 h and 191.6 ng/ml at 48 h of culture. SEH production reached 4.36 µg/ml at 24 h and 5.42 µg/ml at 48 h of culture. Thirty-nine spa types were identified among S. aureus isolates. The most prevalent spa types were t091 and t1181, followed by t4735 and t742, t3380 and t127. Twelve new spa types, i.e., t20572‒t20583 were identified. The wild boar S. aureus population was shown to contain previously identified animal/human-associated spa types and spa types not identified in humans or animals. We also indicate that wildlife animals can be a significant reservoir of see-positive S. aureus.