MRSA Surveillance Research Articles

P-1177. Impact of Staphyloccocus aureus Surveillance and Decolonization on MRSA and MSSA Infections in a Neonatal Intensive Care Unit

Abstract Background Staphyloccus aureus (SA) infection causes significant morbidity and mortality in NICU patients. Colonization by SA is a risk factor for infection. Surveillance and decolonization aims to curb the transmission of SA isolates thereby reducing rates of SA infection. Figure 1. Epidemic Curve of MRSA Colonization and Infections 2012-2023 Methods This retrospective study from 2012-2023 takes place in a 42-bed level-three NICU in Texas Children’s Hospital (Houston, Texas). Neonates are admitted to a private room and undergo weekly surveillance from admission/birth until discharge. Surveillance cultures for MRSA and subsequent decolonization of MRSA-positive neonates began in Oct. 2016. MRSA surveillance was changed to PCR (with reflex to culture if positive) in June 2017. Surveillance PCR (with reflex to culture if positive) and decolonization for MSSA began in Oct. 2021. Colonization is defined as detection by PCR or isolation by culture of SA from nares, umbilicus, or groin. Colonized neonates are treated with mupirocin twice daily for five days and if at least 4 weeks chronologic age or 36 weeks gestational age, topical 2% chlorhexidine wipes daily for five days. Infection is defined by the isolation of SA from cultures in the context of illness. Multiple positive specimens from the same site are considered the same infection if isolated within a 14-day window. Epidemic curves compare colonization and infections before and after the protocol. This study was approved by the Baylor College of Medicine Institutional Review Board. Figure 2. Epidemic Curve of MSSA Colonization and Infections 2012-2023 Results Surveillance and decolonization of MRSA-colonized neonates reduced the number of MRSA infections from its peak in 2016 (Figure 1). We continue to see SA-colonized infants especially with a substantial MSSA colonization burden. Despite the high rate of MSSA colonization, the number of MSSA infections remains low (Figure 2). Control charts (Figure 3 and 4) demonstrate rate, mean and upper limit of infection rates calculated per 1000 patient days. Figure 3. Control Chart for MRSA Infections Conclusion The implementation of surveillance and targeted decolonization has been shown to decrease the number of MRSA infection even with ongoing colonization. Despite the high burden of MSSA-colonization, we do not see major peaks of MSSA infections. Further studies should explore if the presence of resistance genes to mupirocin and/or chlorhexidine explains ongoing colonization. Figure 4. Control Chart for MSSA Infections Disclosures All Authors: No reported disclosures

P-322. Transmission of Methicillin-Resistant Staphylococcus aureus to Healthcare Personnel Gloves and Gowns: a Cohort Study of VA Hospitals in 5 States

Abstract Background The aim of this study was to determine the rate of MRSA transmission to healthcare personnel (HCP) gloves and gown and to determine which patient care interactions and HCP roles are associated with greater transmission of MRSA. Methods Patients with a positive MRSA clinical or surveillance culture within the past 7 days were enrolled at 5 VA medical centers. Research team members observed 5 HCP in the room for each patient and recorded any items that were touched on a standardized data collection form. After completion of tasks and prior to room exit, HCP gloves and gown were cultured separately. The primary outcome was a surrogate measure for transmission defined as “yes” if a HCP glove or gown was contaminated with MRSA. Results We enrolled 799 patients and obtained 3,832 glove and gown cultures. Transmission of MRSA to gloves or gown occurred 713/3832 (18.6%) of the time while 589/3832 (15.4%) of interactions resulted in contamination of gloves and 319/3831 (8.3%) of interactions resulted in contamination of gowns. The gloves and gown of physical therapists and occupational therapists were most frequently contaminated with transmission occurring in 24/84 (29%) and 11/38 (29%) of observations respectively (Table 1). Any interactions that involved touching the patient (patient alone or patient and environment) resulted in glove or gown contamination in 622/2901 (21.4%) of observations, while touching only the environment resulted contamination in 91/931 (9.8%) of observations. Specific patient care activities with the highest rates of transmission included touching the endotracheal tube (12/35, 34%) and assisting the patient with bathing and hygiene (89/283, 31%). Specific environmental items touched with the highest rates of transmission included the call button (75/221, 34%) and the lift (31/125, 27%) (Figure 1). Conclusion Contamination of HCP gloves and gowns with MRSA occurs frequently when caring for Veteran patients particularly when there is direct patient contact. Hospitals may consider optimizing contact precautions by using fewer precautions for low-risk interactions and more precautions for high-risk interactions. Disclosures Anthony Harris, MD, MPH, Innoviva: Advisor/Consultant|UpToDate: Infection Control Editor

Prevalence of MRSA in canine and feline clinical samples from one-third of veterinary practices in Germany from 2019-2021.

MRSA is a major contributor to AMR-related deaths. The WHO's global action plan emphasizes a One Health approach, acknowledging the connection between humans and their companion animals. It is agreed on that comprehensive AMR surveillance is needed. This study provides a large-scale overview of MRSA occurrence in cats and dogs in Germany, serving as a foundation for continuous surveillance. The study analysed all results of canine and feline bacterial diagnostic samples from a large laboratory, encompassing samples received from veterinary practices between January 2019 and December 2021. MRSA prevalence between host species, sample types and geographical distribution were compared. Additionally, data were contrasted with human MRSA surveillance data from Germany. Samples originated from 3491 German veterinary practices, representing 33.1% of practices and clinics nationally. Bacterial examination results from 175 171 samples were analysed, identifying S. aureus in 5526 of these samples (3.2% isolation rate). S. aureus in clinical samples was more prevalent in cats (5.6%) than dogs (2.0%). Methicillin resistance was found in 17.8% of S. aureus samples and was higher in dogs (20.4%, 95%CI 18.9-22.0) than cats (15.6%, 95%CI 14.3-17.0). The highest MRSA prevalence was found in canine wound samples (32%), compared to skin/soft tissue, respiratory tract and other (<23% respectively). The study reveals a 17.8% MRSA prevalence, which is higher than the human outpatient MRSA prevalence (5.4%). Restriction and regulation of veterinary antibiotic use should be validated with AMR surveillance. Our study shows that this is feasible in companion animals with significant coverage.

741. Assessing the Concordance of MRSA Carriage Screening with MRSA Infections

Abstract Background There is a lack of research on MRSA surveillance in children. This study focused on children with confirmed MRSA infections to determine the utility of MRSA screens in guiding empiric anti-MRSA treatment for children without history of MRSA infection. We examined the concordance of screens to assess for differences by infection type, and used statistical analysis to determine significant contributors to concordance. Methods Pediatric hospital patients admitted from 2002-2022 were included. Subjects had MRSA infections subsequent to a MRSA surveillance screen performed in the preceding year. Statistical analysis, namely multivariable and binomial regression, identified associations between MRSA screens and infections. Number needed to treat analysis calculated the utility of re-screening. Results Among 246 subjects, 39.0% had concordant screens. 151 (61.4%) screens were obtained in the two weeks preceding infection. Sensitivity for bacteremia was 50.0% (n=42), for ET/respiratory 44.4% (n=81), for SSTI 29.4% (n=102). For children under 6 months of age, sensitivity was 35.9% (n=78). Multivariable analysis significantly associated days since MRSA screening and decreasing likelihood of concordance. Binomial regression modeled the probability of concordance to drop below 50.0% for all infections after four days, after six days for bacteremia specifically, and twelve days for ET/respiratory infections. Probability of Concordance Over Time The probability of MRSA screening concordance over time based upon binomial prediction modeling. Each line represents the probability of concordance on a given day subsequent to MRSA screening. Number Needed to Treat (test) Analysis A theoretical control arm of patients receiving no re-screening is compared to a theoretical treatment arm receiving re-screening. Each column represents the number needed to re-screen (for a given number of days) to predict one MRSA infection. Absolute risk reduction is overlaid. Conclusion The concordance of screens was far lower than NPV found in past studies. Bacteremia concorded at 50.0%, ET/respiratory infections 44.4%, SSTI 29.4%. The number of days elapsed since MRSA screening proved the only significant covariate. When that covariate modeled the probability of screening concordance with infection, 7 days represented when the probability of concordance fell to or dropped below 50.0% for infection types. Only patients with a known MRSA infection were included in our study, and concordance of screens was far lower than NPV found in past studies; previous results may have been impacted by low prevalence to inform high NPV. We suggest that negative MRSA screens should not invalidate reasonable suspicion for MRSA infection in patients with high pre-test probabilities for infection. Re-screening patients may optimize concordance. Disclosures All Authors: No reported disclosures

Genomic comparison of mecC-carrying methicillin-resistant Staphylococcus aureus from hedgehogs and humans in the Netherlands.

MRSA carrying the mecC gene (mecC-MRSA) have been found in humans and animals worldwide. A high carriage rate of mecC-MRSA has been described among hedgehogs in different countries. We performed genomic comparison of mecC-MRSA from hedgehogs and humans using next-generation sequencing (NGS) to investigate possible zoonotic transmission in the Netherlands. Nasal swabs from hedgehogs (n = 105) were cultured using pre-enrichment and selective plates. Isolates were sequenced using Illumina NGS platforms. These data were compared with sequence data of mecC-MRSA (n = 62) from the Dutch national MRSA surveillance in humans. Fifty hedgehogs were found to be MRSA positive, of which 48 carried mecC. A total of 60 mecC-MRSA isolates derived from 50 hedgehogs were compared with the human isolates. Fifty-nine mecC-MRSA from hedgehogs and all but one isolate from humans belonged to clonal complexes CC130 and CC1943. The mecC gene was located within the SCCmec XI element. Most mecC-MRSA did not carry other resistance genes besides mecC and blaZ. Two human isolates carried erm(C). Isolates differed in the presence of various virulence genes, which were linked to distinct STs and clonal complexes. Some isolates had up to 17 virulence genes, which underlines their pathogenic potential. No genetic clusters of hedgehog and human isolates were found. mecC-MRSA from hedgehogs and humans mainly belonged to the same two clonal complexes, indicating a common source. No firm evidence for recent zoonotic transmission was found. Further studies are needed to investigate the role of hedgehogs in the occurrence of mecC-MRSA in humans.

Whole genome sequencing reveals new links between spa t172/CC59 methicillin-resistant Staphylococcus aureus cases in low-endemicity region of Southwest Finland, 2007‒2016

Methicillin-resistant Staphylococcus aureus (MRSA) rates have remained relatively low in Finland. In Southwest Finland, however, annual MRSA incidence increased from 12 to 25/100,000 between 2007 and 2016 with spa t172 strain causing one fourth (237/983) of all cases. This provoked us to study the molecular epidemiology of t172-MRSA, aiming to better understand the transmission of this strain type. We combined epidemiological data and whole genome sequencing (WGS) of a set of 64 (27%, 64/237) t172-MRSA isolates covering 10years. Isolates represented sporadic and index cases of all identified healthcare-associated outbreaks (HAOs) and family clusters (FCs). Among the included 62 isolates, core-genome MLST analysis revealed eight genomic clusters comprising 24 (38.7%) isolates and 38 (61.3%) non-clustered isolates. Cluster 1 comprised ten and the remaining seven clusters two isolates each, respectively. Two epidemiologically distinct HAOs were linked in cluster 1. FCs were involved in all clusters. All strains were associated with epidemic clonal complex CC59. We were able to confirm the spread of several successful t172-MRSA subclones in regional healthcare and the community. WGS complemented routine surveillance by revealing undetected links between t172-MRSA cases. Targeted, WGS-based typing could enhance MRSA surveillance without the need for routine WGS diagnostics.

Genetic Characteristics of Methicillin-Resistant Staphylococcus argenteus Isolates Collected in the Dutch National MRSA Surveillance from 2008 to 2021.

ABSTRACTStaphylococcus argenteus is a recently described member of the Staphylococcus aureus complex (SAC) and is associated with human disease. The frequency and intensity of infections caused by S. argenteus are similar to those of Staphylococcus aureus. S. argenteus can harbor antibiotic resistance genes and a variety of virulence factors analogous to methicillin-resistant S. aureus (MRSA). The aim of our study was to analyze a collection of isolates in the Dutch national MRSA surveillance from January 2008 until March 2021 that were nontypeable by multilocus variable-number tandem-repeat analysis (MLVA). Matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-ToF MS) was used for identifying the S. argenteus isolates, and whole-genome sequencing and SeqSphere were used to generate an in-house whole-genome multilocus sequence typing (wgMLST) scheme for typing the isolates. Furthermore, the presence of antibiotic resistance genes, replicons, and virulence genes was determined. Of 52,467 isolates submitted as MRSA from January 2008 until March 2021, 64 isolates (0.12%) were nontypeable with MLVA, and 54 of them were identified with mass spectrometry (MALDI-ToF MS) as S. argenteus. It appeared in retrospect that the first methicillin-resistant S. argenteus (MRSArg) was already submitted in 2008. An in-house-developed S. argenteus wgMLST scheme revealed that S. argenteus isolates clustered in 5 genomic groups which were characterized by distinct MLST types, resistomes, plasmid replicon families, and virulence factors. All but one isolate carried the staphylococcal chromosomal cassette mec (SCCmec) type IV harboring the methicillin resistance gene mecA and represent MRSArg. Most of the isolates with SCCmec subtype IVc(2B) had a trimethoprim resistance gene, dfrG, and harbored a blaZ-carrying plasmid, and most MRSArg isolates have the immune-modulating genes scn and sak. Nine of the 47 isolates carried enterotoxin-encoding genes seg, sei, sem, seo, and seu, which might be able to cause food poisoning. In some persons there was long-term persistence of MRSArg, and there were several genetically related MRSArg isolates in people living in close proximity, suggesting direct human-human transmission.IMPORTANCE We show that MRSArg has been circulating in the Netherlands since at least 2008. Although MRSArg is distinct from MRSA, it has a comparable population structure and carries similar resistance and virulence genes. The Dutch national MRSA surveillance has been expanded to include other methicillin-resistant members of the S. aureus complex, such as S. argenteus and Staphylococcus schweitzeri.

Identifying patient-level risk factors associated with non-β-lactam resistance outcomes in invasive MRSA infections in the United States using chain graphs.

BackgroundMRSA is one of the most common causes of hospital- and community-acquired infections. MRSA is resistant to many antibiotics, including β-lactam antibiotics, fluoroquinolones, lincosamides, macrolides, aminoglycosides, tetracyclines and chloramphenicol.ObjectivesTo identify patient-level characteristics that may be associated with phenotype variations and that may help improve prescribing practice and antimicrobial stewardship.MethodsChain graphs for resistance phenotypes were learned from invasive MRSA surveillance data collected by the CDC as part of the Emerging Infections Program to identify patient level risk factors for individual resistance outcomes reported as MIC while accounting for the correlations among the resistance traits. These chain graphs are multilevel probabilistic graphical models (PGMs) that can be used to quantify and visualize the complex associations among multiple resistance outcomes and their explanatory variables.ResultsSome phenotypic resistances had low connectivity to other outcomes or predictors (e.g. tetracycline, vancomycin, doxycycline and rifampicin). Only levofloxacin susceptibility was associated with healthcare-associated infections. Blood culture was the most common predictor of MIC. Patients with positive blood culture had significantly increased MIC of chloramphenicol, erythromycin, gentamicin, lincomycin and mupirocin, and decreased daptomycin and rifampicin MICs. Some regional variations were also observed.ConclusionsThe differences in resistance phenotypes between patients with previous healthcare use or positive blood cultures, or from different states, may be useful to inform first-choice antibiotics to treat clinical MRSA cases. Additionally, we demonstrated multilevel PGMs are useful to quantify and visualize interactions among multiple resistance outcomes and their explanatory variables.

Effectiveness of umbilical culture for surveillance of methicillin-resistant Staphylococcus aureus among neonates admitted to neonatal intensive care units.

To compare the culture sensitivities of MRSA detection, we collected 988 paired umbilical and nasal cultures from screened neonates. MRSA positivity rates were 79.1% from umbilicus and 41.9% from nares (P = .01). The umbilicus was a more useful culture site than the nares for surveillance of MRSA among neonates upon admission.

Methicillin-resistant Staphylococcus aureus in China: a multicentre longitudinal study and whole-genome sequencing

ABSTRACT The aim of this study was to investigate the genomic epidemiology of MRSA in China to identify predominant lineages and their associated genomic and phenotypic characteristics. In this study, we conducted whole-genome sequencing on 565 MRSA isolates from 7 provinces and municipalities of China between 2014 and 2020. MRSA isolates were subjected to MLST, spa typing, SCCmec typing, analysis of virulence determinants and antimicrobial susceptibility testing. Among 565 MRSA isolates tested, clonal complex (CC) 59 (31.2%), CC5 (23.4%) and CC8 (13.63%) were the major lineages, and the clonal structure was dominated by ST59-t437-IV (14.9%), ST239-t030-III (6.4%) and ST5-t2460-II (6.0%), respectively. Of note, CC8, the predominant lineage in 2014–2015, was replaced by CC59 after 2016. Interestingly, the extension and unstable structure of the CC5 population was observed, with ST5-t311-II, ST764-t1084-II, ST5-t2460-II and ST764-t002-II existing complex competition. Further analysis revealed that virulence determinant profiles and antibiograms were closely associated with the clonal lineage. The CC59 MRSA was less resistant to most tested antimicrobials and carried fewer resistance determinants. But rifampicin resistance and mupirocin resistance were closely linked with CC8 and CC5, respectively. MRSA isolates conservatively carried multiple virulence genes involved in various functions. PVL encoding genes were more common in ST338, CC30, CC398, ST8 and CC22, while tsst-1 was associated with ST5. In conclusion, the community-associated CC59-ST59-t437-IV lineage was predominant in China, with diverse clonal isolates alternately circulating in various geographical locations. Our study highlights the need for MRSA surveillance in China to monitor changes in MRSA epidemiology.

A tale of two STs: molecular and clinical epidemiology of MRSA t304 in Norway 2008\u20132016

The purpose of this study was to investigate the epidemiological, molecular, and clinical characteristics of MRSA t304/ST8 and t304/ST6 in Norway from 2008 to 2016. Clinical and epidemiological data were collected for each case included in the study. Strains were characterized by PCR, spa typing, antimicrobial susceptibility testing, and whole genome sequencing. The overall number of cases of MRSA t304 increased from 27 in 2008 to 203 in 2016. Most MRSA t304/ST8 cases were defined as HA-MRSA (89.9%) and diagnosed in persons with Norwegian background, many of them living in nursing homes (62.3%). The number of t304/ST8 cases declined throughout the study period and it has not been reported in Norway since 2014. The increasing MRSA t304/ST6 genotype has mainly been introduced to Norway by immigration from the Middle East, but also from other parts of the world. The t304/ST6 clone is mostly classified as CA-MRSA (75.1%), does not seem to cause serious infections, is not multi-resistant, and has not yet caused outbreaks in Norway. This study provides an example of two MRSA clones with the same spa type found in different epidemiological settings. This is very unusual, but still a reminder that spa typing in some cases may have insufficient discriminatory power for surveillance of MRSA. Our results highlight the importance of active surveillance and characterization of emerging MRSA clones with high potential for spread in the community, which may potentially cause outbreaks in healthcare facilities.

Epidemiology, Molecular Characteristics of Methicillin-Resistant Staphylococcus Aureus in China: A Multicenter Longitudinal Study Based on Whole-Genome Sequencing

The aim of this study was to investigate the genomic epidemiology of MRSA in China to identify predominantly linages and their associated antimicrobial resistance and virulence profiles. In this study, we conducted whole-genome sequencing (WGS) on 565 MRSA isolates from 7 provinces and municipalities of China between 2014 and 2020. MRSA isolates were subjected to MLST, spa typing staphylococcal cassette chromosome mec (SCC mec) typing, analysis of virulence determinants and antimicrobial susceptibility testing. Among 565 MRSA isolates tested, clonal complex (CC) 59 (31.2%), CC5 (23.4%) and CC8 (13.63%) were the major lineages, and the clonal structure was dominated by ST59-t437-IV (14.9%), ST239-t030-III (6.4%), ST5-t2460-II (6.0%). Of note, CC8, the predominant lineage in 2014-2015, was replaced by CC59 in 2016-2017 and since then alternately dominant with CC5. Interestingly, the complicated dynamic change of CC5 population structure was observed with ST764-t1084-II, ST5-t2460-II, ST764-t1084-II and ST764-t002-II successively dominant. Further analysis revealed that virulence determinant profiles and antibiograms were closely associated with the clonal lineage. The CC59 MRSA less resistance to most tested antimicrobial and relatively lower methicillin MIC, while ciprofloxacin, sulfamethoxazole/trimethoprim and rifampicin resistance was closely linked with CC8. MRSA isolates conservatively carried multiple virulence genes for capsule, exoenzymes, secretion, iron uptake and metabolism, biofilm formation and hemolysis. PVL encoding genes was markedly more common in ST338, CC30, CC398, ST8 and CC22, while tsst-1 was associated with ST5. In conclusion, the community-associated CC59-ST59-t437-IV lineage was found to be most predominant in China, with diverse clonal isolates alternately circulating in various geographical locations. Our study highlights the need for MRSA surveillance in China in order to monitor changes in MRSA epidemiology. Funding Information: This study was funded by grants from the Natural Science Fund of China (82072343). Declaration of Interests: The authors declare that there are no conflicts of interest.

Evaluation of MRSA Surveillance Nasal Swabs for Predicting MRSA Infection in Surgical Intensive Care Unit Patients

We aimed to examine the clinical value of serial MRSA surveillance cultures to rule out a MRSA diagnosis on subsequent cultures during a patient's surgical intensive care unit (SICU) admission. We performed a retrospective cohort study to evaluate patients who received a MRSA surveillance culture at admission to the SICU (n=6,915) and collected and assessed all patient cultures for MRSA positivity during their admission. The primary objective was to evaluate the transition from a MRSA negative surveillance on admission to MRSA positive on any subsequent culture during a patient's SICU stay. Percent of MRSA positive cultures by type following MRSA negative surveillance cultures was further analyzed. 6,303 patients received MRSA nasal surveillance cultures at admission with 21,597 clinical cultures and 7,269 MRSA surveillance cultures. Of the 6,163 patients with an initial negative, 53 patients (0.87%) transitioned to MRSA positive. Of the 139 patients with an initial positive, 30 (21.6%) had subsequent MRSA positive cultures. Individuals who had an initial MRSA surveillance positive status on admission predicted MRSA positivity rates for cultures in qualitative lower respiratory cultures (64.3% versus. 3.1%), superficial wound (60.0% versus 1.6%), deep wound (39.0% versus 0.8%), tissue culture (26.3% versus 0.6%), and body fluid (20.8% versus 0.7%) cultures when compared to MRSA negative patients on admission. Following MRSA negative nasal surveillance cultures patients showed low likelihood of MRSA infection suggesting empiric anti-MRSA treatment is unnecessary for specific patient populations. SICU patient's MRSA status at admission should guide empiric anti-MRSA therapy.

Modified methicillin-resistant Staphylococcus aureus detected in neonatal intensive care patients.

ObjectivesAs part of an active MRSA surveillance programme in our neonatal ICU, we identified nares surveillance cultures from two infants that displayed heterogeneity in methicillin resistance between isolated subclones that lacked mecA and mecC.MethodsThe underlying mechanism for the modified Staphylococcus aureus (MODSA) methicillin-resistance phenotype was investigated by WGS.ResultsComparison of finished-quality genomes of four MODSA and four MSSA subclones demonstrated that the resistance changes were associated with unique truncating mutations in the gene encoding the cyclic diadenosine monophosphate phosphodiesterase enzyme GdpP or a non-synonymous substitution in the gene encoding PBP2.ConclusionsThese two cases highlight the difficulty in identifying non-mecA, non-mecC-mediated MRSA isolates in the clinical microbiology laboratory, which leads to difficulties in implementing appropriate therapy and infection control measures.

Association Between Contact Precautions and Transmission of Methicillin-Resistant Staphylococcus aureus in Veterans Affairs Hospitals

The effectiveness and importance of contact precautions for endemic pathogens has long been debated, and their use has broad implications for infection control of other pathogens. To estimate the association between contact precautions and transmission of methicillin-resistant Staphylococcus aureus (MRSA) across US Department of Veterans Affairs (VA) hospitals. This retrospective cohort study used mathematical models applied to data from a population-based sample of adults hospitalized in 108 VA acute care hospitals for at least 24 hours from January 1, 2008, to December 31, 2017. Data were analyzed from May 2, 2019, to December 11, 2020. A positive MRSA test result, presumed to indicate contact precautions use according to the VA MRSA Prevention Initiative. The main outcome was the association between contact precautions and MRSA transmission, defined as the relative transmissibility attributed to contact precautions. A contact precaution effect estimate (<1 indicates a reduction in transmission associated with contact precautions) was estimated for each hospital and then pooled over time and across hospitals using meta-regression. In this cohort study of 108 VA hospitals, more than 2 million unique individuals had over 5.6 million admissions, of which 14.1% were presumed to have contact precautions with more than 8.4 million MRSA surveillance tests. Pooled estimates found associations between contact precautions and transmission to be stable from 2008 to 2017, with estimated transmission reductions ranging from 43% (95% credible interval [CrI], 38%-48%) to 51% (95% CrI, 46%-55%). Over the entire 10-year study period, contact precautions reduced transmission 47% (95% CrI, 45%-49%), and the intrafacility autocorrelation coefficient estimate was 0.99, suggesting consistent estimates over time within facilities. Larger facilities and those with higher admission screening compliance observed additional reductions in transmission associated with contact precautions (relative rate, 0.84; 95% CI, 0.74-0.96 and 0.74; 95% CI, 0.58-0.96, respectively) compared with smaller facilities and those with lower admission screening compliance. Facilities in the southern US had a smaller transmission reduction attributable to contact precautions (relative rate, 1.14; 95% CI, 1.01-1.28) compared with facilities in other regions in the US. In this cohort study of adults in VA hospitals, transmissibility of MRSA was found to be reduced by approximately 50% among patients with contact precautions. These results provide an explanation for decreasing acquisition rates in VA hospitals since the MRSA Prevention Initiative.

248. Why so Much Vancomycin and Piperacillin/Tazobactam Usage Given Known Risks of Nephrotoxicity

BackgroundDespite years of published data describing the increased risk of nephrotoxicity with use of vancomycin and piperacillin/tazobactam (VPT), this combination remains one of the most utilized antibiotic combinations at our institution. There is limited data describing the appropriateness of empiric use of this broad-spectrum regimen. Our primary objective was to evaluate the appropriateness of the anti-methicillin resistant Staphylococcus aureus (MRSA), anti-pseudomonal, and anti-anaerobic spectrum of activity for patients empirically treated with this combination. Our secondary objective was to evaluate the appropriateness of diagnostic evaluation in patients started on this combination.MethodsA retrospective cohort study was performed on a random sample of unique patients prescribed the combination of VPT from October 2019 through March 2020. Demographic and clinical data were abstracted from the electronic medical record. Based on predetermined criteria, we evaluated the appropriateness of the spectrum of activity of empiric therapy and the diagnostic evaluation.ResultsOf 100 patients evaluated, 96 patients (96%) received VPT as empiric treatment. The indications for use are shown in Table 1. Pneumonia and soft tissue/bone/joint infections were the most common indications. The appropriateness of anti-MRSA, anti-pseudomonal, and anti-anaerobic therapy is shown in Table 2. In only 35% of patients was the full spectrum of activity appropriate. Of 47 patients treated empirically for pneumonia, 35 (74%) had an order for a respiratory culture and 7 (15%) for a nasal MRSA surveillance culture. Of 30 patients treated empirically for soft tissue//joint infections, wound cultures were obtained in 22 (73%). Nineteen patients underwent surgical intervention, of whom 17 (89%) had cultures obtained.Table 1. Indications for Empiric Vancomycin and Piperacillin/tazobactam Combination Therapy Table 2: Appropriateness of Spectrum of Activity for Empiric Vancomycin and Piperacillin/tazobactam Combination Therapy ConclusionAt our institution VPT use was usually empiric and unnecessarily broad for the syndrome being treated. Microbiologic testing was suboptimal and may have resulted in prolonged therapy. Although interventions aimed at de-escalating VPT are useful, interventions aimed at ensuring appropriate empiric use of this combination and ensuring appropriate diagnostic testing may be just as important.Disclosures All Authors: No reported disclosures

The molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) in the Czech Republic.

To gain data on the current molecular epidemiology and resistance of MRSA in the Czech Republic. Between September 2017 and January 2018, a total of 441 single-patient MRSA isolates were collected from 11 Czech hospitals and analysed by spa typing, SCCmec typing, antibiotic susceptibility testing, detection of the PVL toxin and the arcA gene. Of all MRSA isolates, 81.41% (n = 359) belonged to the CC5-MRSA clone represented by the spa types t003 (n = 136), t586 (n = 92), t014 (n = 81), t002 (n = 20) and other spa types (n = 30); a majority of the CC5 isolates (n = 348, 96.94%) carried SCCmec type II. The occurrence of CC5-MRSA was more likely in older inpatients and associated with a healthcare origin (P < 0.001). The CC5-MRSA isolates were resistant to more antimicrobial drugs compared with the other MRSAs (P < 0.001). Interestingly, t586 was detected in blood samples more often than the other spa types and, contrary to other spa types belonging to CC5-MRSA, t586 was not associated with patients of advanced age. Other frequently found lineages were CC8 (n = 17), CC398 (n = 11) and CC59 (n = 10). The presence of the PVL was detected in 8.62% (n = 38) of the MRSA isolates. The healthcare-associated CC5-MRSA-II lineage (t003, t586, t014) was found to be predominant in the Czech Republic. t586 is a newly emerging spa type in the Czech Republic, yet reported rarely in other countries. Our observations stress the need for MRSA surveillance in the Czech Republic in order to monitor changes in MRSA epidemiology.

Risk of hospitalization and death within 2years after methicillin-resistant Staphylococcus aureus (MRSA) diagnosis in persons colonized or infected with livestock and non-livestock-associated MRSA-A nationwide register-based cohort study.

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) CC398 has emerged in humans throughout Europe and the USA during the last decade and is associated with the spread of LA-MRSA CC398 in production animals. In this study, we investigated the risk of subsequent hospitalization with an S.aureus-related diagnosis and death within the first 2years after MRSA diagnosis. The study included 7,521 carriers of MRSA, an age-matched reference population of 376,041 individuals and 7,607 patients infected with MRSA. Hazard ratios (HR) for hospitalization with an S.aureus-related diagnosis were 4.09 (95% CI: 2.78-6.00) and for death 1.21 (95% CI: 0.80-1.83) in LA-MRSA CC398 carriers compared with the reference population. Comparing carriers of LA-MRSA CC398 and non-CC398 MRSA, HR for hospitalization was 0.61 (95% CI: 0.37-0.99) and death 0.25 (95% CI: 0.16-0.40), respectively. Patients initially diagnosed with LA-MRSA CC398 or non-CC398 MRSA infection differed from MRSA carriers in terms of older age, higher Charlson comorbidity index score and longer hospital stays. HR for subsequent hospitalization and death was similar regardless having infection with LA-MRSA CC398 or non-CC398 MRSA at the time of MRSA diagnosis. We established that MRSA CC398 carriers have a lower risk of hospitalization and death up to 2years after MRSA diagnosis than non-CC398 MRSA carriers do. In contrast, MRSA carriage, regardless the MRSA strain is a burden in terms of hospitalization and death when compared to the background reference population. Further, we established that there are no differences in risk of subsequent hospitalization and death in patients initially diagnosed with MRSA CC398 or non-CC398 MRSA infection. We suggest that public health surveillance of MRSA clearly needs to distinguish between carriage and infection as well as strain type before any inference from number of cases to disease burden is made.

Prolonged carriage of (livestock-associated) MRSA in individuals without professional livestock contact.

To investigate prolonged carriage of MRSA in adults from the general population living in a livestock-dense area, using WGS. A cross-sectional study during 2014-15 among 2492 adults without professional livestock contact identified 14 (0.6%) nasal MRSA carriers, 10 of which carried livestock-associated (LA)-MRSA of multiple-locus variable-number tandem repeat analysis (MLVA) complex (MC) 398. Two years later, 12 MRSA-positive and 88 MRSA-negative participants provided a second nasal swab and filled in a short questionnaire. Isolates from persons who were MRSA positive at both timepoints were compared using MLVA and isolates with the same MLVA type were sequenced. The WGS data were used for core-genome MLST (cgMLST) and resistome analysis, including sequenced isolates from the national MRSA surveillance. All MRSA-negative persons tested negative again, while 6 of the 12 initially MRSA-positive persons tested positive again. MLVA revealed that isolate pairs from five individuals had the same MLVA type, of which three were LA-MRSA. cgMLST showed that the distance between these isolate pairs ranged between 3 and 13 genes, while the minimum distance to unrelated isolates from the national MRSA surveillance was 38 genes. Moreover, the resistome present in the five isolate pairs was identical within each pair. None of the prolonged carriers was hospitalized during the 3 months before the sampling moment and none of them with LA-MRSA had contact with livestock in this period. Prolonged carriage of MRSA, including LA-MRSA, can be demonstrated after more than 30 months in persons without professional livestock contact.

Prevalence of methicillin-resistant Staphylococcus aureus in healthy Chinese population: A system review and meta-analysis.

ObjectiveTo comprehensively determine the prevalence of MRSA in healthy Chinese population, the influencing factors of MRSA colonization and its antibiotic resistance.MethodsArticles that studied prevalence or influencing factors of MRSA carriage in healthy Chinese population were retrieved from PubMed, Ovid database, three Chinese electronic databases. The pooled prevalence of MRSA, its antibiotic resistance and influencing factors were analyzed by STATA12.0.Results37 studies were included. The pooled prevalence of MRSA was 21.2% (95% CI: 18.5%-23.9%), and the prevalence of S.aureus was 15% (95% CI: 10%-19%), with a significant heterogeneity (MRSA: I2 = 97.6%, P<0.001; S.aureus: I2 = 98.4%, P < 0.001). In subgroup analysis, the pooled prevalence of MRSA was 28% (95%CI: 10%-51%) for Livestock-related workers, 18% (95%CI: 11%-26%) for children, 20% (95%CI: 12%-29%) for healthcare workers, 7% (95%CI: 3%-13%) for community residents. The prevalence of MRSA in studies with oxacillin disk diffusion method (28%, 95%CI: 21%-35%) seemed higher than that with the mecA gene method(12%, 95%CI: 7%-19%). MRSA in studies conducted in Taiwan was more common than in Mainland China and Hong Kong. Similar results were found in meta-regression. Influencing factors for MRSA colonization were noted in seven eligible studies, they included younger age (OR: 3.54, 95% CI: 2.38–5.26; OR: 2.24, 95% CI: 1.73–2.9), attending day care centers (DCCs) (OR: 1.95, 95% CI: 1.4–2.72; OR: 1.53, 95% CI: 1.2–1.95), flu vaccination (OR:1.73, 95% CI: 1.28–2.35), using antibiotics within the past year (OR: 2.05, 95% CI:1.35–3.11), residing in northern Taiwan (OR: 1.45, 95% CI: 1.19–1.77), regular visits to health care facility (OR: 23.83, 95% CI: 2.72–209.01), household member working in health care facility (OR: 8.98, 95% CI:1.4–55.63), and contact with livestock (OR: 6.31, 95% CI: 3.44–11.57). Moreover, MRSA was found to be highly resistant to penicillin, ampicillin, erythromycin, and clindamycin, with a pooled resistance ratio of 100, 93, 88, and 75%, respectively. However, no resistance were noted to vancomycin.ConclusionThe pooled prevalence of MRSA was considerably high in health Chinese population. Additionally, these strains showed extreme resistance to penicillin, ampicillin, erythromycin and clindamycin. Public MRSA protection measures and the surveillance of MRSA should be strengthened to reduce the spread of MRSA among hospitals, communities, and livestock.