Healthcare-associated Methicillin-resistant Staphylococcus Aureus Research Articles

Effects of sub-inhibitory concentrations of nafcillin, vancomycin, ciprofloxacin, and rifampin on biofilm formation of clinical methicillin-resistant Staphylococcus aureus.

Bacteria can be exposed to sub-MICs of antibiotics at the beginning and end of a dosing regimen, between doses, or during low-dose therapies. Growing evidence suggests that sub-MICs of antimicrobials can stimulate MRSA biofilm formation and alter the composition of the biofilm matrix. Pevious studies have found that sub-MICs of oxacillin, methicillin, and amoxicillin promote biofilm formation in some community-acquired MRSA (CA-MRSA). We evaluated biofilm induction by sub-MICs of four different classes of antibiotics in 44 CA-MRSA and 63 healthcare-associated MRSA (HA-MRSA) strains. Our study indicated that sub-MICs of nafcillin, vancomycin, ciprofloxacin, and rifampin frequently promote biofilm induction in clinical MRSA isolates. Strong biofilm induction in sub-MICs of nafcillin, ciprofloxacin, and rifampin was more frequent in HA-MRSA than in CA-MRSA. Antibiotic-induced biofilm formation depends on the antibiotic class, MRSA strain, and antibiotic resistance. Our results emphasize the importance of maintaining effective bactericidal concentrations of antibiotics to treat biofilm-related infections.

Comparative Analysis of Two Commercial Automated Systems with Agar Dilution for Oxacillin Susceptibility and Their Association with Genotypes of Invasive Staphylococcus aureus Isolates (2011-2021).

Determining oxacillin susceptibility using reference methods and automated systems is crucial for treating invasive infections caused by Staphylococcus aureus. This study compares the oxacillin susceptibility results from the two automated systems with agar dilution and correlates them with genotypes of invasive S. aureus. Non-duplicate S. aureus invasive isolates were collected over an 11-year period. The oxacillin susceptibility was determined with Phoenix 100 (Jan 2011 to Aug 2018) or Vitek 2 (Sep 2018 to Dec 2021), and susceptibility for oxacillin and cefoxitin was determined with agar dilution. Methicillin-resistant S. aureus (MRSA) was confirmed with mecA existence, and the genotype was determined using SCCmec. The association between genotype and antibiotic susceptibility using two automated systems and agar dilution was evaluated. A total of 842 invasive S. aureus, including 443 mecA+ MRSA and 399 mecA- MSSA, were collected. The susceptibility rates of oxacillin determined by two automated systems and agar dilution were 68.8% (76.8% for Phoenix 100 and 57.6% for Vitek 2) and 54.0%, respectively. When compared with the oxacillin susceptibility using agar dilution, the categorical agreement for Phoenix 100 and Vitek 2 were 0.46% and 0.88%, respectively (p < 0.001). One hundred and forty-three isolates were misinterpreted as oxacillin-susceptible S. aureus (OSSA) using automated systems while comparing with agar dilution, among which molecularly community-associated MRSA (CA-MRSA) outnumbered healthcare-associated MRSA (HA-MRSA) (99 vs 34, p < 0.001). There were 70 mecA+ OSSA (OS-MRSA) using agar dilution, among which 42 harbored SCCmec types were predominantly categorized as CA-MRSA (38, p < 0.001). The categorical agreement of Vitek 2 in determining oxacillin susceptibility and predicting mecA existence is comparable with agar dilution, whereas Phoenix 100 is not. Most of those ORSA determined by agar dilution but misinterpreted as OSSA by automated systems and OS-MRSA are categorized as CA-MRSA.

Global epidemiology of asymptomatic colonisation of methicillin-resistant Staphylococcus aureus in the upper respiratory tract of young children: a systematic review and meta-analysis

ObjectiveTo estimate the global prevalence of asymptomatic colonisation, and determine the associated risk factors, antibiotic resistance and genotypes of methicillin-resistant Staphylococcus aureus (MRSA) in the upper respiratory tract of young...

Australian Group on Antimicrobial Resistance (AGAR) Australian Staphylococcus aureus Surveillance Outcome Program (ASSOP) Bloodstream Infection Annual Report 2022.

From 1 January to 31 December 2022, fifty-five institutions across Australia participated in the Australian Staphylococcus aureus Surveillance Outcome Program (ASSOP). The aim of ASSOP 2022 was to determine the proportion of Staphylococcus aureus bacteraemia (SAB) isolates in Australia that were antimicrobial resistant, with particular emphasis on susceptibility to methicillin and on characterisation of the molecular epidemiology of the methicillin-resistant isolates. A total of 3,214 SAB episodes were reported, of which 77.5% were community-onset. Overall, 15.0% of S. aureus were methicillin resistant. The 30-day all-cause mortality associated with methicillin-resistant SAB was 21.4%, which was significantly different to the 16.8% all-cause mortality associated with methicillin-susceptible SAB (p = 0.02). With the exception of the β-lactams and erythromycin, antimicrobial resistance in methicillin-susceptible S. aureus was rare. However, in addition to the β-lactams, approximately 31% of methicillin-resistant S. aureus (MRSA) were resistant to ciprofloxacin; 30% to erythromycin; 13% to tetracycline; 11% to gentamicin; and 2% to co-trimoxazole. One MRSA isolate, with a daptomycin MIC of 1.5 mg/L, harboured the A302V mprF and A23V cls2 mutations. When applying the European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints, teicoplanin resistance was detected in one MRSA isolate. Resistance to vancomycin or linezolid was not detected. Resistance to non-β-lactam antimicrobials was largely attributable to the healthcare-associated MRSA (HA-MRSA) clone ST22-IV [2B] (EMRSA-15), and to the community-associated MRSA (CA-MRSA) clone ST45-V [5C2&5] which has acquired resistance to multiple antimicrobials including ciprofloxacin, clindamycin, erythromycin, gentamicin, and tetracycline. The ST22-IV [2B] (EMRSA-15) clone is the predominant HA-MRSA clone in Australia. Nonetheless, 86% of methicillin-resistant SAB episodes were due to CA-MRSA clones. Although polyclonal, approximately 72% of CA-MRSA clones were characterised as ST93-IV [2B] (Queensland clone); ST5-IV [2B]; ST45-V [5C2&5]; ST1-IV [2B]; ST30-IV [2B]; ST97-IV [2B]; ST953-IV [2B]; and ST8-IV [2B]. As CA-MRSA is well established in the Australian community, it is important to monitor antimicrobial resistance patterns in community- and healthcare-associated SAB as this information will guide therapeutic practices in treating S. aureus bacteraemia.

High Incidence of Metastatic Infections in Panton-Valentine Leucocidin-Negative, Community-Acquired Methicillin-Resistant Staphylococcus aureus Bacteremia: An 11-Year Retrospective Study in Japan.

Panton-Valentine leucocidin (PVL)-negative community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) was originally disseminated in Japan and has since replaced healthcare-associated MRSA (HA-MRSA). However, the clinical characteristics of CA-MRSA bacteremia (CA-MRSAB) compared with those of HA-MRSA bacteremia (HA-MRSAB) are unknown. We aim to clarify differences and investigate associations between the clinical manifestations and virulence genes associated with plasma-biofilm formation in PVL-negative CA-MRSA. From 2011 to 2021, when CA-MRSA dramatically replaced HA-MRSA, 79 MRSA strains were collected from blood cultures and analyzed via SCCmec typing and targeted virulence gene (lukSF-PV, cna, and fnbB) detection. The incidence of metastatic infection was significantly higher in CA-MRSAB than in HA-MRSAB. PVL genes were all negative, although cna and fnbB were positive in 55.6% (20/36) and 50% (18/36) of CA-MRSA strains and 3.7% (1/27) and 7.4% (2/27) of HA-MRSA strains, respectively. cna and fnbB carriage were not associated with the development of metastatic infections in MRSAB; however, the bacteremia duration was significantly longer in CA-MRSAB harboring cna. CA-MRSAB may be more likely to cause metastatic infections than HA-MRSAB. Since CA-MRSA is dominant in Japan, suspected metastatic infection foci should be identified by computed tomography, magnetic resonance imaging, and echocardiography when treating MRSAB.

Multidisciplinary treatment for infective endocarditis complicated with systemic multiple abscess due to Panton-Valentine leukocidin producing community-acquired methicillin-resistant Staphylococcus aureus and Candida albicans: a case report

BackgroundInfective endocarditis resulting from community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is a rare, but often fatal heart disorder. Here, we report a case of multidisciplinary treatment for infective endocarditis with systemic multiple abscesses due to Panton-Valentine leukocidin (PVL) producing CA-MRSA and Candida albicans.Case presentationThe patient suffered from infective endocarditis, destructive thyroiditis, hemorrhagic cerebral infarction due to mycotic embolism, lung abscess, multiple skeletal muscle abscess, and disseminate intravascular coagulopathy. Aggressive medical treatment as well as mechanical circulatory support was required before the curative surgical treatment. Blood cultures were positive for MRSA and Candida albicans. Genomic analysis of MRSA revealed Staphylococcal Cassette Chromosome mec IVc and also the virulence gene encoding PVL.ConclusionsCA-MRSA strains have higher pathogenicity and are more destructive to tissue than healthcare-associated MRSA strains because of the toxins they produce, including PVL. Multidisciplinary treatment including aggressive surgery was required to rescue the patient.

The Occurrence of Methicillin-Resistant Staphylococcus Aureus (MRSA) Around the World and Antibiotic Therapy for Selected Infections Caused By MRSA

Abstract Staphylococcus aureus is a Gram-positive bacterium, which can cause serious bacterial infections in humans. It constitutes an important etiological factor of many diseases, for instance, soft tissue and skin infections (including skin boils and abscesses), as well as life-threatening necrotizing pneumonia or toxic shock syndrome. It is estimated that about 25–30% of people are carriers of S. aureus mainly in the anterior nostrils. A smaller percentage of people are carriers of methicillin-resistant S. aureus (MRSA). In accordance with its definition, methicillin-resistant S. aureus is resistant to almost all β-lactam antibiotics. This phenomenon is mainly caused by the presence of penicillin-binding protein in the cell wall – PBP2a, which is the product of the mecA gene, which is part of the complex called SCCmec (staphylococcal cassette chromosome mec). Methicillin-resistant S. aureus (MRSA) results in endemic in hospitals around the world and are one of the leading causes of morbidity and mortality in society. Infections initiated by hospital strains of MRSA (health care-associated MRSA, HA-MRSA) concern mainly immunocompromised patients after surgery. In addition, there are populations of acommunity-associated MRSA (CA-MRSA) strains and populations of livestock-associated MRSA (LA-MRSA) strains. The treatment of infections with MRSA etiology, after exhausting the possibilities of standard antibiotic therapy with the use of i.e. vancomycin, is based on treatment with new-generation antibiotics, such as dalbavacin.

Multidrug-Resistant Staphylococcus aureus Isolates in a Tertiary Care Hospital, Kingdom of Bahrain.

Methicillin-resistant Staphylococcus aureus (MRSA) is a ubiquitous pathogen associated with a wide spectrum of human infections. In recent decades, MRSA infections have been increasingly reported in individuals without established risk factors, infecting immunocompetent members of the community. This emergence is attributed to the production of various virulence factors, notably Panton-Valentine leukocidin(PVL). The aim of this study was to better understand the prevalence, antibiotic resistance profiles, and molecular characteristics of S. aureus and MRSA in a tertiary care hospital in the Kingdom of Bahrain. This cross-sectional study was carried out in a tertiary hospital for a one-year period, from December 2020 to December 2021. A total of 161 consecutive S. aureus isolates were collected. Antibiotic susceptibility was tested using BD Phoenix™ automated identification and susceptibility testing system. Molecular analysis was conducted via conventional PCR and conventional multiplex PCR for SCCmec typing. In this study, 161 S. aureus isolates were investigated, 60% (n=97) were characterized as MRSA, of which, 12% (n=12) were healthcare-associated methicillin-resistant Staphylococcus aureus (HA-MRSA) while 88% (n=85) were community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA). No statistically significant difference (P>0.05) in antibiotic resistance trends between HA-MRSA and CA-MRSA was detected. Multidrug resistance (MDR) amounted to 19% (n=30) of all S. aureus isolates, 14% (n=9) of methicillin-susceptible Staphylococcus aureus (MSSA) isolates, and 22% (n=21) of MRSA isolates. SCCmec typing demonstrated a high prevalence of type IV (61%, n=59), followed by type V (32%, n=31), then type II (4%, n=4), and type III (3%, n=3). The PVL prevalence was 39% (n=25) in MSSA and 62% (n=60) in MRSA, 33% (n=4) in HA-MRSA, and 66% (n=56) in CA-MRSA. This study demonstrated the emergence of PVL-producing CA-MRSA in a tertiary care hospital, as well as the detection of PVL-producing MDR strains. This development prompts serious measures to be taken in order to sustain a healthy clinical environment.

Preventing healthcare-associated MRSA bacteremia: getting to the root of the problem.

Bloodstream infections caused by methicillin-resistant Staphylococcus aureus (MRSA) remain a major challenge in most countries worldwide. We describe a quasi-experimental sequential intervention at Mater Dei Hospital, Malta, to reduce hyper-prevalence of healthcare-associated MRSA bacteremia (HA-MRSA-B). The hospital initiated a hand hygiene (HH) campaign in 2008 to improve alcohol hand rub (AHR) use. In 2011, this was followed by root cause analysis (RCA) of all HA-MRSA-B cases and finally universal MRSA admission screening in 2014. Change-point analysis was used to evaluate the impact of the interventions. The effect of the HH campaign became evident when AHR consumption reached 40L/1000 occupied bed days (BD). RCAs identified intravascular devices as the likely risk factor in 83% of all HA-MRSA-B; specifically non-tunneled double-lumen hemodialysis catheters (36%), peripheral venous cannulas (25%), and central venous catheters (22%). Interventions to improve their management resulted in the greatest reduction of HA-MRSA-B rates. They were informed by the RCA findings and targeted behavior change through education, motivation, and system change. Universal MRSA admission screening provided the final decline in incidence. Each intervention affected HA-MRSA-B rates after a lag period of approximately 18-24 months. Overall, HA-MRSA-B incidence decreased from 1.72 cases/10000BD in 2008 to 0.18/10000BD in 2019; a reduction of almost 90%. Intravenous device interventions were also associated with a reduction of methicillin-sensitive Staphylococcus aureus (MSSA) bacteremia rates. Significant improvement in HA-MRSA-B is possible, even in highly endemic regions. It requires well-planned behavior change interventions which are compatible with local context and culture.

Australian Group on Antimicrobial Resistance (AGAR) Australian Staphylococcus aureus Surveillance Outcome Program (ASSOP).

From 1 January to 31 December 2021, forty-eight institutions around Australia participated in the Australian Staphylococcus aureus Surveillance Outcome Programme (ASSOP). The aim of ASSOP 2021 was to determine the proportion of Staphylococcus aureus bacteraemia (SAB) isolates in Australia that were antimicrobial resistant, with particular emphasis on susceptibility to methicillin and on characterisation of the molecular epidemiology of the methicillin-resistant isolates. A total of 2,928 SAB episodes were reported, of which 78.4% were community-onset. Overall, 16.9% of S. aureus isolates were methicillin resistant. The 30-day all-cause mortality associated with methicillin-resistant SAB was 15.0%, which was not significantly different from the 14.4% all-cause mortality associated with methicillin-susceptible SAB (p = 0.7). With the exception of the β-lactams and erythromycin, antimicrobial resistance in methicillin-susceptible S. aureus was rare. However, in addition to the β-lactams, approximately 36% of methicillin-resistant S. aureus (MRSA) were resistant to ciprofloxacin; 30% to erythromycin; 15% to tetracycline; 16% to gentamicin; and 3% to co-trimoxazole. When applying the European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints, teicoplanin resistance was detected in three S. aureus isolates. Resistance to vancomycin or linezolid was not detected. Resistance to non-β-lactam antimicrobials was largely attributable to the healthcare-associated MRSA (HA-MRSA) clone ST22-IV [2B] (EMRSA-15), and the community-associated MRSA (CA-MRSA) clone ST45-V [5C2&5] which has acquired multiple antimicrobial resistance determinants including ciprofloxacin, erythromycin, clindamycin, gentamicin and tetracycline. The ST22-IV [2B] (EMRSA-15) clone is the predominant HA-MRSA clone in Australia. Nonetheless, 85% of methicillin-resistant SAB episodes were due to CA-MRSA clones. Although polyclonal, approximately 68% of CA-MRSA clones were characterised as ST93-IV [2B] (Queensland clone); ST45-V [5C2&5]; ST5-IV [2B]; ST1-IV [2B]; ST30-IV [2B]; and ST97-IV [2B]. As CA-MRSA is well established in the Australian community, it is important to monitor antimicrobial resistance patterns in community- and healthcare-associated SAB as this information will guide therapeutic practices in treating S. aureus bacteraemia.

2054. Trends in Incidence and Epidemiology of Methicillin-Resistant Staphylococcus aureus Bloodstream Infection, 2005–2020

Abstract Background Methicillin-resistant Staphylococcus aureus (MRSA) is a serious antimicrobial resistance threat; prevention efforts have focused primarily on healthcare-associated MRSA infections. We assessed progress in MRSA bloodstream infection (BSI) prevention during 2005-2020. Methods MRSA BSI data were from CDC Emerging Infections Program’s active, population-based surveillance for invasive S. aureus in 17 counties in 6 states (sites). A case was defined as isolation of MRSA from a blood culture in a resident of the catchment area. Cases were considered hospital-onset (HO) if the culture was obtained &amp;gt; 3 days after hospitalization, healthcare-associated community-onset (HACO) if the culture was obtained in an outpatient setting or ≤ 3 days after hospitalization in a patient with ≥ 1 prior major healthcare exposures, or otherwise community-associated (CA). Annual incidence was calculated per 100,000 census population for each epidemiologic classification. Results MRSA BSI incidence decreased from 32.2 (per 100,000 population) in 2005 to a nadir of 15.7 in 2016, then increased during 2017-2019 to 17.0 and decreased in 2020 to 16.4. (Figure 1). HACO comprised &amp;gt; 50% of all cases throughout 2005-2020 and mirrored the pattern of overall rates. HO rates decreased from 9.2 to 2.3 during 2005-2013 and fell below CA rates starting in 2012; rates were lowest during 2017-2019 (1.8-2.1) and increased in 2020 to 2.4. CA rates remained 3.0-4.6 throughout the surveillance period; during 2015-2019, rates increased from 3.0 to 4.0, then in 2020 decreased to 3.4. All sites saw decreases in overall MRSA BSI rates by &amp;gt; 50% during 2005-2020, and HACO rates in 2020 were at least 50% of total rates for each site. However, the relative proportion of CA and HO rates during 2020 varied by site (Figure 2), with CA MRSA BSI more than twice as common as HO MRSA BSI in two sites. Figure 1.Incidence rates of methicillin-resistant Staphylococcus aureus bloodstream infection, by epidemiologic classification, in 6 Emerging Infections Program sites, 2005–2020Figure 2.Ratio of incidence (per 100,000 population) of community-associated (CA) to hospital-onset (HO) methicillin-resistant Staphylococcus aureus bloodstream infection, in 6 Emerging Infections Program sites, 2020 Conclusion MRSA BSI rates fell by more than half during the 15-year surveillance period, reflecting substantial declines in HACO and HO cases; however, the recent plateau suggests a need for additional preventive measures that restore previous progress. Increased focus on CA MRSA BSI prevention may be needed in some areas depending on local epidemiology. Disclosures Ghinwa Dumyati, MD, Pfizer: Grant/Research Support William Schaffner, MD, VBI Vaccines: Advisor/Consultant.

Methicillin-Resistant Staphylococcus aureus Membrane Vesicles Inhibit the Proliferation and Induce the Apoptosis of Epithelial Cells.

Staphylococcus aureus, or methicillin-resistant Staphylococcus aureus (MRSA), is the predominant pathogen in skin and soft tissue infections (SSTIs), and MRSA membrane vesicles (MVs) play a pivotal role in bacterial pathogenesis and the modulation of the host immune response. We aimed to investigate the interaction between MRSA MVs and epithelial cells. In this study, MVs were isolated from an MRSA culture supernatant using the ELD method, comprising an electrophoretic technique used in combination with a 300 kDa cut-off dialysis bag. The proteomic analysis of the MRSA MVs via mass spectrometry showed that shared and distinct proteins exist in the MVs from clinical MRSA isolates with different genetic backgrounds, such as health-care-associated MRSA (HA-MRSA) and community-associated MRSA (CA-MRSA). These MRSA MVs were found to suppress the proliferation and increase the apoptosis of HaCaT cells. We conducted qPCR array, quantitative real-time PCR (qRT-PCR), and Western blotting (WB) analyses, and the results indicated that BCL2 antagonist/killer 1 (Bak1) may be involved in the apoptosis of HaCaT epithelial cells. Our findings suggest that MRSA MVs inhibit the proliferation and induce the apoptosis of epithelial cells.

PREVALENCE OF METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS AND OTHER STAPHYLOCOCCAL NASAL CARRIAGES AMONG HEALTHCARE WORKERS, PHRAMONGKUTKLAO HOSPITAL

Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a group of S. aureus strains containing the SCCmec gene causing beta-lactam antibiotic resistance. MRSA is common in healthcare settings and can cause serious problems.&#x0D; Objective: The study aimed to investigate the prevalence of MRSA nasal colonization among privates of the Medical Private Company, Phramongkutklao Hospital, including antibiotic susceptibility pattern of S. aureus isolates and risk factors of S. aureus nasal carriage.&#x0D; Methods: Nasal swabs were obtained from the anterior nares of 170 privates. Staphylococcal isolates were identified using a catalase test, tube coagulase test and matrix-assisted laser desorption/ ionization time of flight mass spectrometry (MALDI-TOF MS). MRSA detection was screened using cefoxitin disk diffusion and confirmed using the mecA gene detection and SCCmec typing. Antibiotic susceptibility patterns of S. aureus were examined using the disk diffusion method. A questionnaire was collected from the subjects to determine risk factors for S. aureus nasal carriage.&#x0D; Results: Of 170 subjects, 157 (92.35%) revealed staphylococcal positive, yielding 161 staphylococcal isolates. The prevalence of MRSA, methicillin-resistant Staphylococcus epidermidis (MRSE), and methicillin-susceptible Staphylococcus aureus (MSSA) nasal carriage was 0.59, 1.18 and 8.82%, respectively. The MRSA isolate carried mecA revealing SCCmec type II. The MSSA isolates indicated low resistance to tetracycline (13.3%), whereas the MRSA isolate resisted ciprofloxacin, clindamycin, erythromycin, gentamicin, oxacillin and tetracycline. Using multiple logistic regression analysis, a significant risk factor for S. aureus nasal carriage was utensil sharing (adjusted odds ratio=4.41; 95% CI=1.33-14.61).&#x0D; Conclusion: Healthcare-associated MRSA existed among privates of the Medical Private Company. An associated risk factor for acquiring S. aureus was utensil sharing which could be used to help improve prevention and control management among privates.

Staphylococcus aureus infection in children: diagnosis and treatment in the context of antibiotic resistance spread

The emergence and rapid spread of methicillin-resistant Staphylococcus aureus (MRSA) isolates in the world significantly complicated the treatment and changed the approaches to the diagnosis of staphylococcal infections in children. Staphylococcus aureus is a widespread microorganism dangerous for humans. A wide range of virulence factors the list of which is still being added allows it to quickly enter the body through damaged barriers and cause local and invasive infections, toxin-mediated diseases, as well as persist for a long time. Currently, two fundamentally different variants of MRSA are distinguished: health care-associated and community-acquired. Health care-associated MRSA are resistant to a greater number of antimicrobial agents, while community-acquired MRSA isolates are characterized by recurrent infections and a more severe course of invasive diseases. In addition, MRSA is gradually developing resistance to those antibacterial agents that were the basis of treatment for these infections, primarily clindamycin and vancomycin. All this requires global and regional monitoring of MRSA spread in different variants of staphylococcal infections and the sensitivity of the isolates found to antibiotics in order to optimize empiric and pathogen-specific antibacterial therapy. The article presents data on the activity of various antimicrobial agents against S.aureus, analyzes the available information on the prevalence of MRSA in Ukraine and the results of local monitoring for antibiotic resistance, which turned out to be unidirectional with global trends. Clinical and laboratory criteria for diagnosis of local staphylococcal infections, invasive and toxin-mediated diseases in childhood were presented. Treatment of S.aureus infections involves the necessary surgical interventions and antibacterial therapy considering current epidemiological situation on the spread of MRSA and their sensitivity to antimicrobial agents. Further studies are needed to determine the prevalence of MRSA in children in Ukraine to develop antibacterial therapy algorithms for various types of staphylococcal infections.

Impact of vancomycin use trend change due to the availability of alternative antibiotics on the prevalence of Staphylococcus aureus with reduced vancomycin susceptibility: a 14-year retrospective study

BackgroundWe investigated the trend change in vancomycin-intermediate Staphylococcus aureus (VISA)/heterogeneous VISA (hVISA) prevalence among methicillin-resistant S. aureus (MRSA) bacteremia strains and antistaphylococcal antibiotic use together with mutation studies of vancomycin resistance-related gene loci to evaluate the impact of changes in antibiotic use after new antistaphylococcal antibiotics became available.MethodsAmong 850 healthcare-associated MRSA isolates from 2006 to 2019 at a tertiary hospital in South Korea, hVISA/VISA was determined by modified PAP/AUC analysis, and the identified hVISA/VISA strains were genotyped. Gene mutations at vraSR, graSR, walKR, and rpoB were studied by full-length sequencing. Antistaphylococcal antibiotic use in 2005–2018 was analyzed.ResultsTwo VISA and 23 hVISA strains were identified. The prevalence rate ratio of hVISA/VISA carrying mutations at the two-component regulatory systems among MRSA was 0.668 (95% CI 0.531–0.841; P = 0.001), and the prevalence rate ratio of hVISA/VISA carrying rpoB gene mutations was 1.293 (95% CI 0.981–1.702; 174 P = 0.068). Annual vancomycin use density analyzed by days of therapy (DOT) per 1,000 patient-days did not decrease significantly, however the annual average length of time analyzed by the number of days vancomycin was administered for each case showed a significantly decreasing trend.ConclusionsDuring the 14-year period when the average length of vancomycin therapy decreased every year with the availability of alternative antibiotics, the prevalence of hVISA/VISA did not decrease significantly. This seems to be because the resistant strains carrying the rpoB mutations increased despite the decrease in the strains carrying the mutations at the two-component regulatory systems.

Prevalence of SCCmec Types I, II, III, and pvl gene among Methicillin-Resistant Staphylococcus aureus (MRSA) isolated from clinical specimens in Sanglah General Hospital

Background: Methicillin-Resistant Staphylococcus aureus (MRSA) is a big challenge for health services worldwide which causes infections both in healthcare and community. Healthcare-associated MRSA (HA-MRSA) strains are shown to be resistant to beta-lactam antibiotics and several non-beta lactam antibiotics. At the same time, the community-associated MRSA (CA-MRSA) tends to be resistant to beta-lactam antibiotics. MRSA carried staphylococcal cassette chromosome (SCCmec) types I, II, III, IV, and V. SCCmec types I, II, and III were predominantly found in  HA-MRSA strain while SCCmec types IV and V predominantly found in CA-MRSA strains. Furthermore, the panton valentine leukocidine (pvl) gene is commonly found in CA-MRSA strains. Therefore, this study aimed to determine the prevalence of SCCmec types I, II, III, and pvl gene in MRSA isolated from clinical specimens in Sanglah General Hospital. Methods: This study was a cross-sectional descriptive study. MRSA was isolated from clinical specimens (sputum, wounds, tissue, blood, etc.) from January 2020 to July 2021 and identified by the Vitek 2 Compact (Biomerieux, France) at the Clinical Microbiology Laboratory of Sanglah Hospital. Prevalence of SCCmec and pvl gene using PCR. Data were analyzed using Microsoft Excel version 2010 for Windows. Results: Most of the specimens (69.56%) were wound. Seventeen (73.91%) out of 23 MRSA isolates were positive for the SCCmec III and pvl gene, while none was positive for the SCCmec I and SCCmec II. About 19 (82.60%) isolates were resistant to two or more non-beta-lactam antibiotics. Conclusions: The isolates of MRSA in this study were predominantly isolated from wound specimens, with the most prevalent genetic element being SCCmec III. In this study, although most MRSA isolates carried SCCmec III that suggested as HA-MRSA, however, most of the strains harbored the pvl gene. This interesting phenomenon needs to be further elucidated.

Australian Group on Antimicrobial Resistance (AGAR) Australian Staphylococcus aureus Sepsis Outcome Programme (ASSOP) Annual Report 2020.

From 1 January to 31 December 2020, forty-nine institutions around Australia participated in the Australian Staphylococcus aureus Sepsis Outcome Programme (ASSOP). The aims of ASSOP 2020 were to determine the proportion of Staphylococcus aureus bacteraemia (SAB) isolates in Australia that were antimicrobial resistant, with particular emphasis on susceptibility to methicillin; and to characterise the molecular epidemiology of the methicillin-resistant isolates. A total of 2,734 SAB episodes were reported, of which 79.7% were community-onset. Of S. aureus isolates, 17.6% were methicillin resistant. The 30-day all-cause mortality associated with methicillin-resistant SAB was 14.2%, which was not significantly different from the 13.3% mortality associated with methicillin-susceptible SAB (p = 0.6). With the exception of the β-lactams and erythromycin, antimicrobial resistance in methicillin-susceptible S. aureus was rare. However, in addition to the β-lactams, approximately 35% of methicillin-resistant S. aureus (MRSA) were resistant to erythromycin, 33% to ciprofloxacin, 13% to tetracycline, 13% to gentamicin and 4% to co-trimoxazole. When applying the European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints, teicoplanin resistance was detected in four S. aureus isolates. Resistance was not detected for vancomycin and linezolid. Resistance to non-beta-lactam antimicrobials was largely attributable to two healthcare-associated MRSA (HA-MRSA) clones: ST22-IV [2B] (EMRSA-15) and ST239-III [3A] (Aus-2/3 EMRSA). The ST22-IV [2B] (EMRSA-15) clone is the predominant HA-MRSA clone in Australia. However, 85% percent of methicillin-resistant SAB isolates were community-associated MRSA (CA-MRSA) clones. Although polyclonal, approximately 77% of CA-MRSA clones were characterised as: ST93-IV [2B] (Queensland CA-MRSA); ST5-IV [2B]; ST45-V [5C2&5]; ST1-IV [2B]; ST30-IV [2B]; ST8-IV [2B]; and ST97-IV [2B]. The CA-MRSA clones, in particular ST45-V [5C2&5], have acquired multiple antimicrobial resistance determinants including ciprofloxacin, erythromycin, clindamycin, gentamicin and tetracycline. The multi-resistant ST45-V [5C2&5] clone accounted for 11.0% of CA-MRSA. As CA-MRSA is well established in the Australian community, it is important to monitor antimicrobial resistance patterns in community- and healthcare-associated SAB as this information will guide therapeutic practices in treating S. aureus sepsis.

Genotyping of methicillin-resistant Staphylococcus aureus isolates causing invasive infections using spa typing and their correlation with antimicrobial susceptibility

Correlation of antimicrobial susceptibility patterns with particular spa types could help physicians select appropriate antibiotics for the treatment of invasive methicillin-resistant Staphylococcus aureus (MRSA) infections. The aim of this study was to investigate invasive MRSA isolates through delineating the molecular typing results and correlating them with antibiotic susceptibility testing results. A total of 670 non-duplicate mecA-positive MRSA isolates from patients with invasive infections were collected from a 5-year nationwide antimicrobial surveillance programme [Tigecycline In vitro Surveillance in Taiwan (TIST)] and 58 spa types were identified among 639 isolates (95.4%) by determining the allelic profile of the spa gene using PCR and nucleotide sequencing. Six major spa types, including spa t002 (n=103; 15.4%) and t037 (n=253, 37.8%), were classified as healthcare-associated MRSA (HA-MRSA; 53.1%), while t437 (n=151; 22.5%), t441 (n=13; 1.9%), t1081 (n=19; 2.8%) and t3525 (n=14; 2.1%) were classified as community-associated MRSA (CA-MRSA; 29.4%). Antimicrobial susceptibility was determined by agar dilution or broth microdilution for various antibiotics, and Etest was also used both for daptomycin and vancomycin. The declining trend in vancomycin minimum inhibitory concentration (MIC) was in parallel with an increasing frequency of CA-MRSA. Antibiotic susceptibility patterns were correlated with particular spa types and this correlation could help physicians select appropriate antibiotics for the treatment of invasive MRSA infections.

Predicting Methicillin-Resistant Staphylococcus aureus (MRSA) Bloodstream Infection Incidence Rates using Canadian Nosocomial Infection Surveillance Program (CNISP)

Methicillin-Resistant Staphylococcus aureus (MRSA) is among the most prevalent nosocomial pathogens globally, causing significant morbidity, mortality, and healthcare costs. MRSA bloodstream infection (BSI) incidence rates in Canadian hospitals have significantly risen by almost 60% and have a mortality of over 20% upon Intensive Care Unit admission. MRSA is believed to be spread through healthcare workers; thus, high hand hygiene compliancy in addition to environmental cleaning are the cornerstone countermeasures to disrupting its transmission. The Public Health Agency of Canada (PHAC), in collaboration with the Canadian Nosocomial Infection Surveillance Program (CNISP), conducts national, sentinel surveillance on healthcare-associated infections like MRSA. As a Student Epidemiologist, I developed a research proposal detailing two study objectives: 1) develop a regression model to predict all incident MRSA BSI rates among acute-care hospitals in Canada using CNISP MRSA BSI incident cases from 2000 to 2019, and 2) create a compartmental (Susceptible-Infected-Recovered-Deceased) model to determine the impact of various Infection Prevention and Control (IPC) measures on the risk of healthcare-associated MRSA BSI transmission specifically. This study hopes to demonstrate that proper IPC compliance is associated with lower incident MRSA BSI rates with the goal being to produce a manuscript draft by 2021. MRSA poses a serious threat to patient safety globally and is becoming a growing national public health concern in Canada; determining which IPC strategy is most effective at disrupting MRSA transmission is essential to reducing incidence and mortality rates.

Molecular characterization of healthcare and community-associated methicillin-resistant Staphylococcus aureus using phage open-reading frame typing.

The polymerase chain reaction-based open reading frame typing (POT) method is a simple and rapid method for the strain-level discrimination of methicillin-resistant Staphylococcus aureus (MRSA). We investigated the molecular characteristics of S. aureus strains by multilocus sequencing typing (MLST) and POT and the profiles of antibiotic resistance and virulence genes of MRSA isolates in a single center of Tokyo, Japan. Five types by MLST and 19 types by POT were detected in the 25 MRSA isolates. ST5 and a POT1 score of 93 were associated with healthcare-associated MRSA, whereas ST8 and a POT1 score of 106 were associated with community-associated MRSA. Each strain evaluated by POT score was completely associated with similar profiles of antibiotic resistance and virulence genes. These data showed that the POT system was a powerful molecular tool for the epidemiological characterization of MRSA isolates, which correlated with the profiles of antibiotic resistance and virulence genes.