Trends and characteristics of culture-confirmed Staphylococcus aureus infections in a large U.S. integrated health care organization

Molecular Epidemiologic and Geo-Spatial Characterization of Staphylococcus aureus Cultured from Skin and Soft Tissue Infections from United States-Born and Immigrant Patients Living in New York City

(1) Background: With increasing international travel and mass population displacement due to war, famine, climate change, and immigration, pathogens, such as Staphylococcus aureus (S. aureus), can also spread across borders. Methicillin-resistant S. aureus (MRSA) most commonly causes skin and soft tissue infections (SSTIs), as well as more invasive infections. One clonal strain, S. aureus USA300, originating in the United States, has spread worldwide. We hypothesized that S. aureus USA300 would still be the leading clonal strain among US-born compared to non-US-born residents, even though risk factors for SSTIs may be similar in these two populations (2) Methods: In this study, 421 participants presenting with SSTIs were enrolled from six community health centers (CHCs) in New York City. The prevalence, risk factors, and molecular characteristics for MRSA and specifically clonal strain USA300 were examined in relation to the patients' self-identified country of birth. (3) Results: Patients born in the US were more likely to have S. aureus SSTIs identified as MRSA USA300. While being male and sharing hygiene products with others were also significant risks for MRSA SSTI, we found exposure to animals, such as owning a pet or working at an animal facility, was specifically associated with risk for SSTIs caused by MRSA USA300. Latin American USA300 variant (LV USA300) was most common in participants born in Latin America. Spatial analysis showed that MRSA USA300 SSTI cases were more clustered together compared to other clonal types either from MRSA or methicillin-sensitive S. aureus (MSSA) SSTI cases. (4) Conclusions: Immigrants with S. aureus infections have unique risk factors and S. aureus molecular characteristics that may differ from US-born patients. Hence, it is important to identify birthplace in MRSA surveillance and monitoring. Spatial analysis may also capture additional information for surveillance that other methods do not.

In Vitro Activities of Ceftobiprole, Dalbavancin, Tedizolid and Comparators against Clinical Isolates of Methicillin-Resistant Staphylococcus aureus Associated with Skin and Soft Tissue Infections

Skin and soft tissue infections (SSTIs) are associated with significant morbidity and healthcare costs, especially when caused by methicillin-resistant Staphylococcus aureus (MRSA). Vancomycin is a preferred antimicrobial therapy for the management of complicated SSTIs (cSSTIs) caused by MRSA, with linezolid and daptomycin regarded as alternative therapeutic options. Due to the increased rates of antimicrobial resistance in MRSA, several new antibiotics with activity against MRSA have been recently introduced in clinical practice, including ceftobiprole, dalbavancin, and tedizolid. We evaluated the in vitro activities of the aforementioned antibiotics against 124 clinical isolates of MRSA obtained from consecutive patients with SSTIs during the study period (2020-2022). Minimum inhibitory concentrations (MICs) for vancomycin, daptomycin, ceftobiprole, dalbavancin, linezolid and tedizolid were evaluated by the MIC Test Strip using Liofilchem strips. We found that when compared to the in vitro activity of vancomycin (MIC₉₀ = 2 μg/mL), dalbavancin possessed the lowest MIC₉₀ (MIC₉₀ = 0.094 μg/mL), followed by tedizolid (MIC₉₀ = 0.38 μg/mL), linezolid, ceftobiprole, and daptomycin (MIC₉₀ = 1 μg/mL). Dalbavancin demonstrated significantly lower MIC₅₀ and MIC₉₀ values compared to vancomycin (0.064 vs. 1 and 0.094 vs. 2, respectively). Tedizolid exhibited an almost threefold greater level of in vitro activity than linezolid, and also had superior in vitro activity compared to ceftobiprole, daptomycin and vancomycin. Multidrug-resistant (MDR) phenotypes were detected among 71.8% of the isolates. In conclusion, ceftobiprole, dalbavancin and tedizolid exhibited potent activity against MRSA and are promising antimicrobials in the management of SSTIs caused by MRSA.

Thermal susceptibility and antibiotic synergism of methicillin-resistant Staphylococcus aureus biofilms

Methicillin-Resistant Staphylococcus aureus (MRSA) biofilms are among the most dangerous infections on medical implants, typically requiring surgical explantation and replacement. This study investigated the thermal susceptibility of MRSA biofilms to thermal shocks from 60 to 80 °C for 1-30 min as well as the effect of various antibiotics (most notably methicillin) on thermal mitigation. Pre- and post-shock exposure to three different classes of antibiotics (ciprofloxacin, tobramycin, and methicillin) at concentrations ranging from 0.25 to 128 μg mL-1 were investigated. MRSA biofilms exhibited thermal susceptibility comparable to other common nosocomial pathogens, such as Pseudomonas aeruginosa, though with greater variability. Exposure to antibiotics of any class significantly decreased the degree of thermal shock required for reliable mitigation, including at subclinical concentration. These combined treatments reduced biofilm population more than the sum of thermal and chemical treatments alone, demonstrating synergism, while also indicating a critical population drop of ∼4.5 log10 beyond which the biofilms typically became non-viable.

Methicillin-resistant Staphylococcus aureus nasal carriage among patients on haemodialysis with newly inserted central venous catheters

BACKGROUND

Although methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization is common among end-stage kidney disease patients undergoing haemodialysis, few studies were focused on MRSA nasal carriers among haemodialysis patients with central venous catheters (CVCs). The aim of this study is to evaluate the risk factors, various clinical outcomes and effect of decolonization for MRSA nasal colonization among patients on haemodialysis via CVCs.

METHODS

This was a single-centre non-concurrent cohort study of 676 patients who had new haemodialysis CVCs inserted. They were all screened for MRSA colonization via nasal swabs and were categorized into two groups: MRSA carriers and MRSA noncarriers. Potential risk factors and clinical outcomes were analysed in both groups. All MRSA carriers were given decolonization therapy and the effect of decolonization on subsequent MRSA infection was also performed.

RESULTS

Eighty-two patients (12.1%) were MRSA carriers. Multivariate analysis showed that MRSA carrier (OR 5.44; 95% CI 3.02-9.79), long-term care facility resident (OR 4.08; 95% CI 2.07-8.05), history of Staphylococcus aureus infection (OR 3.20; 95% CI 1.42-7.20) and CVC in situ > 21 days (OR 2.12; 95% CI 1.15-3.93) were independent risk factors for MRSA infection. There was no significant difference in all-cause mortality between MRSA carriers and noncarriers. The MRSA infection rates were similar between MRSA carriers with successful decolonization and those who had failed/incomplete decolonization in our subgroup analysis.

CONCLUSION

MRSA nasal colonization is an important cause of MRSA infection among haemodialysis patients with CVCs. However, decolonization therapy may not be effective in reducing MRSA infection.

Quantifying patient- and hospital-level antimicrobial resistance dynamics in Staphylococcus aureus from routinely collected data

Antimicrobial resistance (AMR) to all antibiotic classes has been found in the pathogen Staphylococcus aureus . The reported prevalence of these resistances vary, driven by within-host AMR evolution at the patient level, and between-host transmission at the hospital level. Without dense longitudinal sampling, pragmatic analysis of AMR dynamics at multiple levels using routine surveillance data is essential to inform control measures. We explored S. aureus AMR diversity in 70,000 isolates from a UK paediatric hospital between 2000-2020, using electronic datasets containing multiple routinely collected isolates per patient with phenotypic antibiograms, hospitalisation information, and antibiotic consumption. At the hospital-level, the proportion of isolates that were meticillin-resistant (MRSA) increased between 2014-2020 from 25 to 50%, before sharply decreasing to 30%, likely due to a change in inpatient demographics. Temporal trends in the proportion of isolates resistant to different antibiotics were often correlated in MRSA, but independent in meticillin-susceptible S. aureus . Ciprofloxacin resistance in MRSA decreased from 70% to 40% of tested isolates between 2007-2020, likely linked to a national policy to reduce fluoroquinolone usage in 2007. At the patient level, we identified frequent AMR diversity, with 4% of patients ever positive for S. aureus simultaneously carrying, at some point, multiple isolates with different resistances. We detected changes over time in AMR diversity in 3% of patients ever positive for S. aureus . These changes equally represented gain and loss of resistance. Within this routinely collected dataset, we found that 65% of changes in resistance within a patient’s S. aureus population could not be explained by antibiotic exposure or between-patient transmission of bacteria, suggesting that within-host evolution via frequent gain and loss of AMR genes may be responsible for these changing AMR profiles. Our study highlights the value of exploring existing routine surveillance data to determine underlying mechanisms of AMR. These insights may substantially improve our understanding of the importance of antibiotic exposure variation, and the success of single S. aureus clones.

Genomic Update of Phenotypic Prediction Rule for Methicillin-Resistant Staphylococcus aureus (MRSA) USA300 Discloses Jail Transmission Networks with Increased Resistance

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of health care-associated (HA) and community-associated (CA) infections. USA300 strains are historically CA-MRSA, while USA100 strains are HA-MRSA. Here, we update an antibiotic prediction rule to distinguish these two genotypes based on antibiotic resistance phenotype using whole-genome sequencing (WGS), a more discriminatory methodology than pulsed-field gel electrophoresis (PFGE). MRSA clinical isolates collected from 2007 to 2017 underwent WGS; associated epidemiologic data were ascertained. In developing the rule, we examined MRSA isolates that included a population with a history of incarceration. Performance characteristics of antibiotic susceptibility for predicting USA300 compared to USA100, as defined by WGS, were examined. Phylogenetic analysis was performed to examine resistant USA300 clades. We identified 275 isolates (221 USA300, 54 USA100). Combination susceptibility to clindamycin or levofloxacin performed the best overall (sensitivity 80.7%, specificity 75.9%) to identify USA300. The average number of antibiotic classes with resistance was higher for USA100 (3 versus 2, P < 0.001). Resistance to ≤2 classes was predictive for USA300 (area under the curve (AUC) 0.84, 95% confidence interval 0.78 to 0.90). Phylogenetic analysis identified a cluster of USA300 strains characterized by increased resistance among incarcerated individuals. Using a combination of clindamycin or levofloxacin susceptibility, or resistance to ≤2 antibiotic classes, was predictive of USA300 as defined by WGS. Increased resistance was observed among individuals with incarceration exposure, suggesting circulation of a more resistant USA300 clade among at-risk community networks. Our phenotypic prediction rule could be used as an epidemiologic tool to describe community and nosocomial shifts in USA300 MRSA and quickly identify emergence of lineages with increased resistance.

IMPORTANCE Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of health care-associated (HA) and community-associated (CA) infections, but the epidemiology of these strains (USA100 and USA300, respectively) now overlaps in health care settings. Although sequencing technology has become more available, many health care facilities still lack the capabilities to perform these analyses. In this study, we update a simple prediction rule based on antibiotic resistance phenotype with integration of whole-genome sequencing (WGS) to predict strain type based on antibiotic resistance profiles that can be used in settings without access to molecular strain typing methods. This prediction rule has many potential epidemiologic applications, such as analysis of retrospective data sets, regional monitoring, and ongoing surveillance of CA-MRSA infection trends. We demonstrate application of this rule to identify an emerging USA300 strain with increased antibiotic resistance among incarcerated individuals that deviates from the rule.

Staphylococcal Skin and Soft Tissue Infections

Staphylococcus aureus is the most common bacteria causing purulent skin and soft tissue infections. Many disease-causing S aureus strains are methicillin resistant; thus, empiric therapy should be given to cover methicillin-resistant S aureus. Bacterial wound cultures are important for characterizing local susceptibility patterns. Definitive antibiotic therapy is warranted, although there are no compelling data demonstrating superiority of any one antibiotic over another. Antibiotic choice is predicated by the infection severity, local susceptibility patterns, and drug-related safety, tolerability, and cost. Response to therapy is expected within the first days; 5 to 7 days of therapy is typically adequate to achieve cure.

Current Epidemiology, Etiology, and Burden of Acute Skin Infections in the United States

The US burden of acute skin infections is substantial. While Staphylococcus aureus and Streptococcus spp. are the most common causes, gram-negative bacteria and mixed infections can occur in some settings. These mixed infections are more likely to result in inappropriate empiric antibiotic therapy. Important challenges remain in diagnosing and treating acute skin infections.

Health Disparities in Staphylococcus aureus Transmission and Carriage in a Border Region of the United States Based on Cultural Differences in Social Relationships: Protocol for a Survey Study

Background

Health care–associated Staphylococcus aureus infections are declining but remain common. Conversely, rates of community-associated infections have not decreased because of the inadequacy of public health mechanisms to control transmission in a community setting. Our long-term goal is to use risk-based information from empirical socio-cultural-biological evidence of carriage and transmission to inform intervention strategies that reduce S aureus transmission in the community. Broad differences in social interactions because of cultural affiliation, travel, and residency patterns may impact S aureus carriage and transmission, either as risk or as protective factors.

Objective

This study aims to (1) characterize S aureus carriage rates and compare circulating pathogen genotypes with those associated with disease isolated from local clinical specimens across resident groups and across Hispanic and non-Hispanic white ethnic groups and (2) evaluate social network relationships and social determinants of health-based risk factors for their impact on carriage and transmission of S aureus.

Methods

We combine sociocultural survey approaches to population health sampling with S aureus carriage and pathogen genomic analysis to infer transmission patterns. Whole genome sequences of S aureus from community and clinical sampling will be phylogenetically compared to determine if strains that cause disease (clinical samples) are representative of community genotypes. Phylogenetic comparisons of strains collected from participants within social groups can indicate possible transmission within the group. We can therefore combine transmission data with social determinants of health variables (socioeconomic status, health history, etc) and social network variables (both egocentric and relational) to determine the extent to which social relationships are associated with S aureus transmission.

Results

We conducted a first year pilot test and feasibility test of survey and biological data collection and analytic procedures based on the original funded design for this project (#NIH U54MD012388). That design resulted in survey data collection from 336 groups and 1337 individuals. The protocol, described below, is a revision based on data assessment, new findings for statistical power analyses, and refined data monitoring procedures.

Conclusions

This study is designed to evaluate ethnic-specific prevalence of S aureus carriage in a US border community. The study will also examine the extent to which kin and nonkin social relationships are concordant with carriage prevalence in social groups. Genetic analysis of S aureus strains will further distinguish putative transmission pathways across social relationship contexts and inform our understanding of the correspondence of S aureus reservoirs across clinical and community settings. Basic community-engaged nonprobabilistic sampling procedures provide a rigorous framework for completion of this 5-year study of the social and cultural parameters of S aureus carriage and transmission.

Determinants of methicillin-resistant Staphylococcus aureus (MRSA) prevalence in the Asia-Pacific region: A systematic review and meta-analysis

OBJECTIVES

Published literature on methicillin-resistant Staphylococcus aureus (MRSA) in the Asia-Pacific region was reviewed to document the prevalence of MRSA in the region and to examine the impact of variability in study design on the reported MRSA prevalence data.

METHODS

This review included studies reporting MRSA prevalence between 2000 and 2016. Studies were excluded if they did not contain complete information on antimicrobial susceptibility testing (AST) methods. Primary outcomes were the proportion of MRSA among S. aureus isolates (resistance proportion) or among individual samples (prevalence).

RESULTS

A total of 229 studies in 19 countries/territories were included in the study. There was substantial heterogeneity in both outcomes (resistance proportion, I²=99.59%; prevalence, I²=99.83%), precluding pooled averages, and meta-regression analyses revealed that these variations were explained by country income status and participant characteristics but not by methodological differences in AST. Also, no significant secular changes in MRSA prevalence or resistance proportions in Asia-Pacific were found.

CONCLUSION

The resistance proportions and prevalence of MRSA infections in Asia-Pacific are comparable with those reported in other regions with no significant secular changes in the past decade. Country income status and characteristics of the sample population explained more variation in the reported resistance proportions and prevalence of MRSA than methodological differences in AST across locations in the region.

Molecular analysis of immune evasion cluster (IEC) genes and intercellular adhesion gene cluster (ICA) among methicillin-resistant and methicillin-sensitive isolates of Staphylococcus aureus

Introduction

Resistance to antibiotics and presence of virulence factors play an important role in increased mortality associated with infection due to Staphylococcus aureus. In this study, we determine antibiotic resistance pattern, presence of the icaADBC locus as well as biofilm formation and distribution and diversity the immune evasion cluster (IEC) genes in clinical isolate of S. aureus from Kerman, Iran.

Materials and methods

During 15 months, 100 clinical isolates S. aureus recovered from different patients were admitted to Kerman University affiliated hospitals. Resistance to different antibiotic agents was determined by disk diffusion method. Phenotypic method was used to the determination of biofilm formation ability and methicillin-resistance S. aureus (MRSA). Polymerase chain reaction technique (PCR) was used to the detection of nuc, mecA, icaA, icaD, icaB, icaC, scn, sea, sak, sep and chp genes.

Results

Forty-four isolates were considered as MRSA and all of isolates were sensitive to vancomycin and linezolid. Our results showed, 77.2% (34/44) of MRSA and 8.9 % (5/56) of MSSA isolates were multidrug resistant. The predominant IEC variant was type B and our results displayed that 77.7% of the MRSA isolates harbor loci icaD and mecA. There was no significant difference in production biofilm between MSSA and MRSA isolates (P ≥ 0.05). There was significant difference in presence IEC types between MSSA and MRSA isolates (P = 0.000).

Conclusions

The presence of icaADBC locus may not be a determining factor for biofilm formation in Staphtlocooci and other mechanisms might be involved in this process.The high prevalence IEC types in MSSA isolates can indicate that the presence of these genes can be an advantage for pathogenesis of these isolates in different infections.

Prevalence and Factors Associated With Multidrug-Resistant Gram-Negative Organisms in Patients With Spinal Cord Injury

OBJECTIVE

Infections caused by multidrug-resistant gram-negative organisms (MDRGNOs) have been increasing every year. The objective of this study was to describe the prevalence of MDRGNOs and factors associated with MDRGNOs in patients with spinal cord injury or disorder (SCI/D).

DESIGN

Retrospective cohort study.

METHODS

Department of Veterans Affairs (VA) electronic health record data from 142 VA facilities were evaluated for 19,642 patients with SCI/D. Multivariable cluster-adjusted models were fit to identify factors associated with MDRGNO.

RESULTS

Gram-negative (GN) cultures occurred in 44% of patients with SCI/D receiving care at VA facilities, and 11,527 (41.3%) GN cultures had an MDRGNO. The most frequent GN organisms (GNOs) were Escherichia coli (28.5%), Klebsiella pneumoniae (17.0%), and Pseudomonas aeruginosa (16.0%). Two-thirds of GN cultures were from the outpatient setting, where MDRGNO prevalence was 37.6%. Significant geographic variation in the prevalence of MDRGNOs was identified (South, 44.7%; Northeast, 44.3%; West, 36.8%; Midwest, 34.4%). Other factors associated with an MDRGNO were older age, injury characteristics, comorbidities, specimen type, healthcare setting, and healthcare exposure. Black (odds ratio [OR], 1.58; 95% confidence interval [CI], 1.39–1.78) and Hispanic race (OR, 1.58; 95% CI, 1.28–1.95), polymicrobial culture (OR, 2.67; 95% CI, 2.46–2.90), and antibiotic use in the previous 90 days (OR, 1.62; 95% CI, 1.50–1.76) were also associated with having an MDRGNO.

CONCLUSIONS

MDRGNOs were common in community and healthcare settings among veterans with SCI/D, with significant geographic variation. Health care and antibiotic exposures were significant factors associated with MDRGNOs. Priority should be given to controlling the spread of MDRGNOs in this special population, including a focus on judicious use of antibiotics.

Infect Control Hosp Epidemiol 2017;38:1464–1471

Introduction to the Centers for Disease Control and Prevention and the Healthcare Infection Control Practices Advisory Committee Guideline for the Prevention of Surgical Site Infections

Surgical site infection (SSI) is a common type of health-care-associated infection (HAI) and adds considerably to the individual, social, and economic costs of surgical treatment. This document serves to introduce the updated Guideline for the Prevention of SSI from the Centers for Disease Control and Prevention (CDC) and the Healthcare Infection Control Practices Advisory Committee (HICPAC). The Core section of the guideline addresses issues relevant to multiple surgical specialties and procedures. The second procedure-specific section focuses on a high-volume, high-burden procedure: Prosthetic joint arthroplasty. While many elements of the 1999 guideline remain current, others warrant updating to incorporate new knowledge and changes in the patient population, operative techniques, emerging pathogens, and guideline development methodology.

Multi-drug resistant organism infections in a medical ICU: Association to clinical features and impact upon outcome

OBJECTIVE

To define clinical features associated with Intensive Care Unit (ICU) infections caused by multi-drug resistant organisms (MDRO) and their impact on patient outcome.

DESIGN

A single-center, retrospective case-control study was carried out between January 2010 and May 2010.

SETTING

A medical ICU (MICU) in the United States.

PATIENTS

The study included a total of 127 MDRO-positive patients and 186 MDRO-negative patients.

INTERVENTIONS

No interventions were carried out.

RESULTS

Out of a total of 313 patients, MDROs were present in 127 (41.7%). Based on the multivariate analysis, only infection as a cause of admission [OR 3.3 (1.9-5.8)]), total days of ventilation [OR 1.07 (1.01-1.12)], total days in hospital [OR 1.04 (1.01-1.07)], immunosuppression [OR 2.04 (1.2-3.5)], a history of hyperlipidemia [OR 2.2 (1.2-3.8)], surgical history [OR 1.82 (1.05-3.14)] and age [OR 1.02 (1.00-1.04)] were identified as clinical factors independently associated to MDROs, while the Caucasian race was negatively associated to MDROs. The distribution of days on ventilation, days in hospital and days of antibiotic treatment prior to infection differed between the MDRO-positive and MDRO-negative groups. The MDRO-positive patients showed a greater median number of days in hospital and days of antibiotic treatment before infection, with a greater median number of days in hospital, days of antibiotic treatment and days of ventilation after infection, compared to the MDRO-negative patients. The mortality rate was not significantly different between the two groups. Appropriate empirical antibiotic therapy was prescribed in 82% of the MDRO-positive cases - such treatment being started within 24h after onset of the infection in 68.5% of the cases.

CONCLUSION

Defining clinical factors associated with MDRO infections and administering timely and appropriate empirical antibiotic therapy may help reduce the mortality associated with these infections. In our hospital we did not withhold broad spectrum drugs as empirical therapy in patients with clinical features associated to MDRO infection. Our rate of appropriate empirical therapy was therefore high, which could explain the absence of excessive mortality in patients infected with MDROs.

Polymorphisms in HLA Class II Genes Are Associated With Susceptibility to Staphylococcus aureus Infection in a White Population

BACKGROUND

Staphylococcus aureus can cause life-threatening infections. Human susceptibility to S. aureus infection may be influenced by host genetic variation.

METHODS

A genome-wide association study (GWAS) in a large health plan-based cohort included biologic specimens from 4701 culture-confirmed S. aureus cases and 45 344 matched controls; 584 535 single-nucleotide polymorphisms (SNPs) were genotyped on an array specific to individuals of European ancestry. Coverage was increased by imputation of >25 million common SNPs, using the 1000 Genomes Reference panel. In addition, human leukocyte antigen (HLA) serotypes were also imputed.

RESULTS

Logistic regression analysis, performed under the assumption of an additive genetic model, revealed several imputed SNPs (eg, rs115231074: odds ratio [OR], 1.22 [P = 1.3 × 10(-10)]; rs35079132: OR, 1.24 [P = 3.8 × 10(-8)]) achieving genome-wide significance on chromosome 6 in the HLA class II region. One adjacent genotyped SNP was nearly genome-wide significant (rs4321864: OR, 1.13; P = 8.8 × 10(-8)). These polymorphisms are located near the genes encoding HLA-DRA and HLA-DRB1. Results of further logistic regression analysis, in which the most significant GWAS SNPs were conditioned on HLA-DRB1*04 serotype, showed additional support for the strength of association between HLA class II genetic variants and S. aureus infection.

CONCLUSIONS

Our study results are the first reported evidence of human genetic susceptibility to S. aureus infection.

In Vitro Activity of Ceftaroline against Staphylococcus aureus Isolated in 2012 from Asia-Pacific Countries as Part of the AWARE Surveillance Program

Ceftaroline, the active metabolite of the prodrug ceftaroline-fosamil, is an advanced-generation cephalosporin with activity against methicillin-resistant Staphylococcus aureus (MRSA). This investigation provides in vitro susceptibility data for ceftaroline against 1,971 S. aureus isolates collected in 2012 from seven countries (26 centers) in the Asia-Pacific region as part of the Assessing Worldwide Antimicrobial Resistance and Evaluation (AWARE) program. Broth microdilution as recommended by the CLSI was used to determine susceptibility. In all, 62% of the isolates studied were MRSA, and the ceftaroline MIC90 for all S. aureus isolates was 2 μg/ml (interpretive criteria: susceptible, ≤1 μg/ml). The overall ceftaroline susceptibility rate for S. aureus was 86.9%, with 100% of methicillin-sensitive S. aureus isolates and 78.8% of MRSA isolates susceptible to this agent. The highest percentages of ceftaroline-nonsusceptible MRSA isolates came from China (47.6%), all of which showed intermediate susceptibility, and Thailand (37.1%), where over half (52.8%) of isolates were resistant to ceftaroline (MIC, 4 μg/ml). Thirty-eight ceftaroline-nonsusceptible isolates (MIC values of 2 to 4 μg/ml) were selected for molecular characterization. Among the isolates analyzed, sequence type 5 (ST-5) was the most common sequence type encountered; however, all isolates analyzed from Thailand were ST-228. Penicillin-binding protein 2a (PBP2a) substitution patterns varied by country, but all isolates from Thailand had the Glu239Lys substitution, and 12 of these also carried an additional Glu447Lys substitution. Ceftaroline-fosamil is a useful addition to the antimicrobial agents that can be used to treat S. aureus infections. However, with the capability of this species to develop resistance to new agents, it is important to recognize and monitor regional differences in trends as they emerge.

In Vitro Activity of Ceftaroline against Staphylococcus aureus Isolates Collected in 2012 from Latin American Countries as Part of the AWARE Surveillance Program

The in vitro activities of ceftaroline and comparators, using broth microdilution, were determined against 1,066 Staphylococcus aureus isolates from hospitalized patients. Seventeen medical centers from Latin American countries contributed isolates. Methicillin-resistant S. aureus (MRSA) percentages ranged from 46% (Brazil) to 62% (Argentina). All methicillin-susceptible S. aureus (MSSA) isolates were susceptible to ceftaroline. Ceftaroline activity against MRSA varied with MIC90s of 0.5 (Venezuela) to 2 (Brazil, Chile, and Colombia) μg/ml, which was the highest MIC value. ST-5 was the most common sequence type.

Stable Expression and Characterization of an Optimized Mannose Receptor

The mannose receptor (MR) is a macrophage surface receptor that recognizes pathogen associated molecular patterns (PAMPs) from a diverse array of bacterial, fungal and viral pathogens. Functional studies of the MR are hampered by the scarcity of human cell lines that express the receptor. Current model systems available for the study of MR biology often demonstrate low levels of expression and do not retain many of the classical MR properties. Although several laboratories have reported transient and stable expression of MR from plasmids, preliminary data from our laboratory suggests that these plasmids produce a protein that lacks critical domains and is often not stable over time. In this current report we describe the generation and characterization of a novel human codon-optimized system for transient and stable MR expression. Rare codons and sequences that contribute to mRNA instability were modified to produce mRNA that is qualitatively and quantitatively improved. Confocal imaging of the transient and stably expressed optimized receptor demonstrates a distribution consistent with previous reports. To demonstrate the functional characteristics of the optimized receptor, we further show that the introduction of codon-optimized MR plasmid can confer MR-associated phagocytosis of S. aureus to non-phagocytic HeLa cells. We show that three molecules participate in the engagement and internalization of S. aureus. MR was found to colocalize with Toll-like receptor 2 (TLR2) and Rab5 following exposure to pHrodo-stained S. aureus, suggesting cooperation among the three molecules to engage and internalize the bacterial particle. This study describes a transfection capable, optimized MR receptor with functional characteristics similar to the wild type receptor and further demonstrates a new system for the continued study of MR biology and function.

Meticillin-resistant Staphylococcus aureus and meticillin-susceptible Staphylococcus aureus screening in a cohort of haemodialysis patients: carriage, demographics and outcomes

BACKGROUND

Patients on haemodialysis are vulnerable to colonization with Staphylococcus aureus due to frequent hospital contact, indwelling devices, and impaired immunity. Additionally colonization is associated with increased risk of infection.

AIM

To determine the prevalence of both meticillin-resistant S. aureus (MRSA) and meticillin-susceptible S. aureus (MSSA) carriage in our haemodialysis cohort and to identify any risk factors predisposing to carriage, recolonization, or persistent carriage following a decolonization programme.

METHODS

All haemodialysis patients screened for S. aureus carriage between June 2009 and May 2011 were retrospectively followed up for 18 months using hospital electronic records. Statistical analysis was performed using IBM SPSS version 19.

FINDINGS

Out of 578 patients screened, 288 patients (49%) had at least one positive swab (10% MRSA, 90% MSSA). Of these patients, 265 completed a course of decolonization therapy following which 36% successfully eradicated (eradicators) and 64% did not (non-eradicators). There was no statistically significant difference in patient demography, type of vascular access, 18-month patient mortality, or number of hospital admissions between the two groups. Those who failed to eradicate were more likely to have had an episode of S. aureus bacteraemia within the study period compared to those who successfully decolonized (P = 0.003).

CONCLUSION

Half of our haemodialysis cohort was colonized with S. aureus at any one time over an 18-month period. Following decolonization, one-third of patients remained successfully eradicated for 18 months. Non-eradicators have an increased risk of bacteraemia, which is associated with poor mortality. We would recommend routine screening and aggressive attempts to decolonize.

Health care-associated methicillin-resistant Staphylococcus aureus infections increases the risk of postdischarge mortality

BACKGROUND

Although many studies have estimated the impact of health care-associated methicillin-resistant Staphylococcus aureus (MRSA) infections on mortality during initial hospitalization, little is known about the long-term risk of death in these patients. The purpose of this study was to quantify the effect of MRSA health care-acquired infections (HAIs) on mortality after hospital discharge.

METHODS

Our study cohort consisted of patients with inpatient admission within the U.S. Department of Veterans Affairs system between October 1, 2007, and September 30, 2010. Of these patients, we identified those with a positive MRSA culture from electronic microbiology reports. We constructed multivariable Cox proportional hazards regressions to assess the impact of a positive culture on postdischarge mortality in the 365 days following discharge using both the full cohort and a propensity score-matched subsample.

RESULTS

In our analysis cohort of 369,743 inpatients, positive MRSA cultures were recorded in 3,599 (1.0%) patients. We found that positive cultures resulted in an increased risk of postdischarge mortality both in the full cohort (hazard ratio = 1.42, P < .001) and in the subset of propensity score-matched patients (hazard ratio = 1.37, P < .0001).

CONCLUSION

We found that MRSA HAIs significantly elevate the long-term risk of mortality. These results underscore the importance of infection prevention efforts in the hospital.

Postoperative Staphylococcus aureus infections in Medicare beneficiaries

Staphylococcus aureus (S. aureus) infections are important because of their increasing frequency, resistance to antibiotics, and high associated rates of disabilities and deaths. We examined the incidence and correlates of S. aureus infections following 219,958 major surgical procedures in a 5% random sample of fee-for-service Medicare beneficiaries from 2004-2007. Of these surgical patients, 0.3% had S. aureus infections during the hospitalizations when index surgical procedures were performed; and 1.7% and 2.3%, respectively, were hospitalized with infections within 60 days or 180 days following admissions for index surgeries. S. aureus infections occurred within 180 days in 1.9% of patients following coronary artery bypass graft surgery, 2.3% following hip surgery, and 5.9% following gastric or esophageal surgery. Of patients first hospitalized with any major infection reported during the first 180 days after index surgery, 15% of infections were due to S. aureus, 18% to other documented organisms, and no specific organism was reported on claim forms in 67%. Patient-level predictors of S. aureus infections included transfer from skilled nursing facilities or chronic hospitals and comorbid conditions (e.g., diabetes, congestive heart failure, chronic obstructive pulmonary disease, and chronic renal disease). In a logarithmic regression, elective index admissions with S. aureus infection stayed 130% longer than comparable patients without that infection. Within 180 days of the index surgery, 23.9% of patients with S. aureus infection and 10.6% of patients without this infection had died. In a multivariate logistic regression of death within 180 days of admission for the index surgery with adjustment for demographics, co-morbidities, and other risks, S. aureus was associated with a 42% excess risk of death. Due to incomplete documentation of organisms in Medicare claims, these statistics may underestimate the magnitude of S. aureus infection. Nevertheless, this study generated a higher rate of S. aureus infections than previous studies.

New patterns of methicillin-resistant Staphylococcus aureus (MRSA) clones, community-associated MRSA genotypes behave like healthcare-associated MRSA genotypes within hospitals, Argentina

Methicillin-resistant Staphylococcus aureus (MRSA) burden is increasing worldwide in hospitals [healthcare-associated (HA)-MRSA] and in communities [community-associated (CA)-MRSA]. However, the impact of CA-MRSA within hospitals remains limited, particularly in Latin America. A countrywide representative survey of S. aureus infections was performed in Argentina by analyzing 591 clinical isolates from 66 hospitals in a prospective cross-sectional, multicenter study (Nov-2009). This work involved healthcare-onset infections-(HAHO, >48 hospitalization hours) and community-onset (CO) infections [including both, infections (HACO) in patients with healthcare-associated risk-factors (HRFs) and infections (CACO) in those without HRFs]. MRSA strains were genetically typed as CA-MRSA and HA-MRSA genotypes (CA-MRSAG and HA-MRSAG) by SCCmec- and spa-typing, PFGE, MLST and virulence genes profile by PCR. Considering all isolates, 63% were from CO-infections and 55% were MRSA [39% CA-MRSAG and 16% HA-MRSAG]. A significantly higher MRSA proportion among CO- than HAHO-S. aureus infections was detected (58% vs 49%); mainly in children (62% vs 43%). The CA-MRSAG/HA-MRSAG have accounted for 16%/33% of HAHO-, 39%/13% of HACO- and 60.5%/0% of CACO-infections. Regarding the epidemiological associations identified in multivariate models for patients with healthcare-onset CA-MRSAG infections, CA-MRSAG behave like HA-MRSAG within hospitals but children were the highest risk group for healthcare-onset CA-MRSAG infections. Most CA-MRSAG belonged to two major clones: PFGE-type N-ST30-SCCmecIVc-t019-PVL(+) and PFGE-type I-ST5-IV-SCCmecIVa-t311-PVL(+) (45% each). The ST5-IV-PVL(+)/ST30-IV-PVL(+) clones have caused 31%/33% of all infections, 20%/4% of HAHO-, 43%/23% of HACO- and 35%/60% of CACO- infections, with significant differences by age groups (children/adults) and geographical regions. Importantly, an isolate belonging to USA300-0114-(ST8-SCCmecIVa-spat008-PVL(+)-ACME(+)) was detected for the first time in Argentina. Most of HA-MRSAG (66%) were related to the Cordobes/Chilean clone-(PFGE-type A-ST5-SCCmecI-t149) causing 18% of all infections (47% of HAHO- and 13% of HACO-infections). Results strongly suggest that the CA-MRSA clone ST5-IV-PVL(+) has begun to spread within hospitals, replacing the traditional Cordobes/Chilean-HA-MRSA clone ST5-I-PVL(-), mainly in children. Importantly, a growing MRSA reservoir in the community was associated with spreading of two CA-MRSA clones: ST5-IV-PVL(+), mainly in children with HRFs, and ST30-IV-PVL(+) in adults without HRFs. This is the first nationwide study in Argentina providing information about the molecular and clinical epidemiology of CA-MRSA, particularly within hospitals, which is essential for designing effective control measures in this country and worldwide.

PA-1, a novel synthesized pyrrolizidine alkaloid, inhibits the growth of Escherichia coli and Staphylococcus aureus by damaging the cell membrane

In the present study, antimicrobial activity and mode of a novel synthesized pyrrolizidine alkaloid (PA-1) were investigated. PA-1 exhibited predominantly strong antibacterial activity toward six bacteria tested with minimal inhibitory concentration (MIC) values ranging from 0.0039 to 0.025 mg ml(-1). The time-kill assay indicated that PA-1 killed Escherichia coli and Staphylococcus aureus completely at 2MIC (minimum bactericidal concentration) within 8 h. Besides, PA-1-induced death rates of most sensitive strains (E. coli, 97.80% and S. aureus, 96.24%) were analyzed by flow cytometry. A combination of approaches was used to verify the membrane damage of E. coli and S. aureus. Results showed that release of 260 nm absorbing materials quickly increased after PA-1 treatment. PA-1 also rapidly promoted the uptake of crystal violet from 24.52 to 97.12% for E. coli and from 19.68 to 97.63% for S. aureus when the concentrations were changed from MIC to 4MIC. Furthermore, the cellular membrane damages were testified by the significant increase of fluorescence intensity and decrease of membrane potential. Finally, lecithin and phosphate groups were applied to search the possibly targets on the cytoplasmic membrane. Results showed that PA-1 acted on cytoplasmic membrane phospholipids and phosphate groups of S. aureus but not of E. coli. In conclusion, the novel synthesized PA-1 exerted its antibacterial activity by acting on membrane phospholipids and phosphate groups and then damaging the structures of cellular membrane, which finally led to cell death.

Replacement of HA-MRSA by CA-MRSA infections at an academic medical center in the midwestern United States, 2004-5 to 2008

We noted anecdotally that infections designated as health care-associated (HA-) MRSA by epidemiologic criteria seemed to be decreasing in incidence at the University of Chicago Medical Center (UCMC) after 2004. We compared MRSA patients seen at any site of clinical care at UCMC and the isolates that caused their infections in 2004-5 (n = 545) with those in 2008 (n = 135). The percent of patients with MRSA infections cultured > 2 days after hospital admission decreased from 19.5% in 2004-5 to 7.4% in 2008 (p = 0.001). The percent in 2004-5 compared with 2008 who had a hospitalization (49.1% to 26.7%, p = 0.001) or surgery (43.0% to 14.1%, p<0.001) in the previous year decreased. In 2008 a greater percent of patients was seen in the emergency department (23.1% vs. 39.3%) and a smaller percent both in intensive care units (15.6% vs. 6.7%) and in other inpatient units (40.7% vs. 32.6%) (p<0.001). The percent of patients with CA-MRSA infections by the CDC epidemiologic criteria increased from 36.5% in 2004-5 to 62.2% in 2008 (p<0.001). The percent of MRSA isolates sharing genetic characteristics of USA100 decreased from 27.9% (152/545) to 12.6% (17/135), while the percent with CA-MRSA (USA300) characteristics increased from 53.2% (290/545) to 66.7% (90/135). The percent of infections that were invasive did not change significantly. Our data suggest that HA-MRSA infections, both by epidemiologic and microbiologic criteria, relative to CA-MRSA, decreased between 2004-5 and 2008 at UCMC.

Skin infections and antibiotic stewardship: analysis of emergency department prescribing practices, 2007-2010

Introduction: National guidelines suggest that most skin abscesses do not require antibiotics, and that cellulitis antibiotics should target streptococci, not community-associated MRSA (CA-MRSA). The objective of this study is to describe antimicrobial treatment of skin infections in U.S. emergency departments (EDs) and analyze potential quality measures.

Methods: The National Hospital Ambulatory Medical Care Survey (NHAMCS) is a 4-stage probability sample of all non-federal U.S. ED visits. In 2007 NHAMCS started recording whether incision and drainage was performed at ED visits. We conducted a retrospective analysis, pooling 2007–2010 data, identified skin infections using diagnostic codes, and identified abscesses by performance of incision and drainage. We generated national estimates and 95% confidence intervals using weighted analyses; quantified frequencies and proportions; and evaluated antibiotic prescribing practices. We evaluated 4 parameters that might serve as quality measures of antibiotic stewardship, and present 2 of them as potentially robust enough for implementation.

Results: Of all ED visits, 3.2% (95% confidence interval 3.1–3.4%) were for skin infection, and 2.7% (2.6–2.9%) were first visits for skin infection, with no increase over time (p=0.80). However, anti-CA-MRSA antibiotic use increased, from 61% (56–66%) to 74% (71–78%) of antibiotic regimens (p<0.001). Twenty-two percent of visits were for abscess, with a non-significant increase (p=0.06). Potential quality measures: Among discharged abscess patients, 87% were prescribed antibiotics (84–90%, overuse). Among antibiotic regimens for abscess patients, 84% included anti-CA-MRSA agents (81–89%, underuse).

Conclusion: From 2007–2010, use of anti-CA-MRSA agents for skin infections increased significantly, despite stable visit frequencies. Antibiotics were over-used for discharged abscess cases, and CA-MRSA-active antibiotics were underused among regimens when antibiotics were used for abscess. [West J Emerg Med. 2014;15(3):282–289.]

Incidence, trends and demographics of Staphylococcus aureus infections in Auckland, New Zealand, 2001-2011

Background

New Zealand has a higher incidence of Staphylococcus aureus disease than other developed countries, with significant sociodemographic variation in incidence rates. In contrast to North America, the majority of disease is due to methicillin-susceptible S. aureus (MSSA), although relatively little is known about the comparative demographics of MSSA and methicillin-resistant S. aureus (MRSA) infections in New Zealand.

Methods

Our objectives were to describe the trends, incidence and patient demographics of all S. aureus infections in patients presenting to our institution between 2001 and 2011, and compare the epidemiology of MSSA and MRSA infections. We identified all patients with S. aureus infections over the study period. A unique S. aureus infection was defined as the first positive S. aureus culture taken from the same patient within a thirty-day period. Standard definitions were used to classify episodes into community- or healthcare-associated S. aureus infection.

Results

There were 16,249 S. aureus infections over the study period. The incidence increased significantly over the study period from 360 to 412 per 100,000 population (P < 0.001), largely driven by an increase in community-associated non-invasive MSSA infections. When compared with MSSA infections, patients with non-multiresistant MRSA infections were more likely to be older, have hospital-onset infections and be Māori or Pacific Peoples.

Conclusions

Our work provides valuable baseline data on the epidemiology and trends of S. aureus infections in New Zealand. The significant increase in community-associated S. aureus infections is of public health importance. Future studies should investigate the reasons underlying this concerning trend.

What is the rate of methicillin-resistant Staphylococcus aureus and Gram-negative infections in open fractures?

BACKGROUND

There have been increasing reports of methicillin-resistant Staphylococcus aureus (MRSA) infections in the community, but it is unclear whether infectious organisms in open fracture infections have changed and if our current regimen of antibiotic prophylaxis is therefore obsolete.

QUESTIONS/PURPOSES

We determined the recent incidence of MRSA and Gram-negative organism infections after open fractures.

METHODS

We performed a retrospective cohort study on 189 patients with 202 open fractures treated from 2009 to 2010. During the followup, patients were evaluated for signs of infection using the Centers for Disease Control and Prevention criteria. We determined the organisms using routine microbiology culture. The minimum followup was 3 months (median, 47 months; range, 3-108 months).

RESULTS

Of the 202 open fractures, 20 (10%) developed infections. The most common organism was Staphylococcus, whereas five (25%) of those infected were positive for MRSA, and 11 (55%) of those with infection were cultured for at least one Gram-negative organism. Six (30%) open fractures had infections that grew out multiple organisms. The incidence of MRSA infections in our open fracture population was 2.5%.

CONCLUSIONS

There is a high incidence of MRSA and Gram-negative infections after open fractures, which may indicate that current antibiotic regimens need to be changed.

LEVEL OF EVIDENCE

Level IV, retrospective case-series. See the Guidelines for Authors for a complete description of levels of evidence.

Molecular epidemiology of hospital-onset methicillin-resistant Staphylococcus aureus infections in Southern Chile

Methicillin-resistant Staphylococcus aureus (MRSA) is a pathogen of public health importance. In Chile, the Cordobes/Chilean clone was the predominant healthcare-associated MRSA (HA-MRSA) clone in 1998. Since then, the molecular epidemiological surveillance of MRSA has not been performed in Southern Chile. We aimed to investigate the molecular epidemiology of HA-MRSA infections in Southern Chile to identify the MRSA clones involved, and their evolutionary relationships with epidemic international MRSA lineages. A total of 303 single inpatient isolates of S. aureus were collected in the Valdivia County Hospital (2007-2008), revealing 33% (100 MRSA/303) prevalence for HA-MRSA infections. The SCCmec types I and IV were identified in 97% and 3% of HA-MRSA, respectively. All isolates lacked the pvl genes. A random sample (n = 29) of all MRSA was studied by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), SCCmec subtyping, agr and spa typing, and virulence genes profiling. PFGE analysis revealed the predominance (89%, 26/29) of pulsotype A and three additional pulsotypes, designated H1, I33, and G1. Pulsotype A (ST5-SCCmecI-spa-t149) is clonally related to the Cordobes/Chilean clone. Pulsotype H1 (ST5-SCCmecIVNT-spa-t002) is genetically related to the Pediatric clone (ST5-SCCmecIV). Pulsotype I33 (ST5-SCCmecIVc-spa-t002) is clonally related by PFGE to the community-associated MRSA (CA-MRSA) clone spread in Argentina, I-ST5-IVa-PVL(+). The G1 pulsotype (ST8-SCCmecIVc-spa-t024) is clonally related to the epidemic USA300 CA-MRSA. Here, we demonstrate the stability of the Cordobes/Chilean clone over time as the major HA-MRSA clone in Southern Chile. The identification of two CA-MRSA clones might suggest that these clones have entered into the healthcare setting from the community. These results emphasize the importance of the local surveillance of MRSA infections in the community and hospital settings.

Incidence, microbiology, and patient characteristics of skin and soft-tissue infections in a U.S. population: a retrospective population-based study

Background

Skin and soft tissue infections (SSTIs) are commonly occurring infections with wide-ranging clinical manifestations, from mild to life-threatening. There are few population-based studies of SSTIs in the period after the rapid increase in community-acquired methicillin-resistant Staphyloccus aureus (MRSA).

Methods

We used electronic databases to describe the incidence, microbiology, and patient characteristics of clinically-diagnosed skin and soft tissue infections (SSTIs) among members of a Northern California integrated health plan. We identified demographic risk factors associated with SSTIs and MRSA infection.

Results

During the three-year study period from 2009 to 2011, 376,262 individuals experienced 471,550 SSTI episodes, of which 23% were cultured. Among cultured episodes, 54% were pathogen-positive. Staphylococcus aureus (S. aureus) was isolated in 81% of pathogen-positive specimens, of which nearly half (46%) were MRSA. The rate of clinically-diagnosed SSTIs in this population was 496 per 10,000 person-years. After adjusting for age group, gender, race/ethnicity and diabetes, Asians and Hispanics were at reduced risk of SSTIs compared to whites, while diabetics were at substantially higher risk compared to non-diabetics. There were strong age group by race/ethnicity interactions, with African Americans aged 18 to <50 years being disproportionately at risk for SSTIs compared to persons in that age group belonging to other race/ethnicity groups. Compared to Whites, S. aureus isolates of African-Americans and Hispanics were more likely to be MRSA (Odds Ratio (OR): 1.79, Confidence Interval (CI): 1.67 to 1.92, and, OR: 1.24, CI: 1.18 to 1.31, respectively), while isolates from Asians were less likely to be MRSA (OR: 0.73, CI: 0.68 to 0.78).

Conclusions

SSTIs represent a significant burden to the health care system. The majority of culture-positive SSTIs were caused by S. aureus, and almost half of the S. aureus SSTIs were methicillin-resistant. The reasons for African-Americans having a higher likelihood, and Asians a lower likelihood, for their S. aureus isolates to be methicillin-resistant, should be further investigated.

Kaiser Permanente Vaccine Study Center: Highlights of 2009-2012

The Kaiser Permanente Vaccine Study Center is a specialized research organization in Oakland, California. They have been an active vaccine research group for many years, and have participated in and led a multitude of vaccine studies. This article will review the last three years of research activities.

Epidemics of community-associated methicillin-resistant Staphylococcus aureus in the United States: a meta-analysis

Staphylococcus aureus is the most frequent cause of skin and soft tissue infections in humans. Methicillin-resistant strains of S. aureus (MRSA) that emerged in the 1960s presented a relatively limited public health threat until the 1990s, when novel community-associated (CA-) MRSA strains began circulating. CA-MRSA infections are now common, resulting in serious and sometimes fatal infections in otherwise healthy people. Although some have suggested that there is an epidemic of CA-MRSA in the U.S., the origins, extent, and geographic variability of CA-MRSA infections are not known. We present a meta-analysis of published studies that included trend data from a single site or region, and derive summary epidemic curves of CA-MRSA spread over time. Our analysis reveals a dramatic increase in infections over the past two decades, with CA-MRSA strains now endemic at unprecedented levels in many US regions. This increase has not been geographically homogeneous, and appears to have occurred earlier in children than adults.

Epidemiology of mecA-Methicillin Resistant Staphylococcus aureus (MRSA) in Iran: A Systematic Review and Meta-analysis

OBJECTIVES

Staphylococcus aureus (S. aureus) is a prevalent pathogen worldwide. Methicillin resistant S. aureus (MRSA), which is usually multi-resistant in hospitals, has been a daunting challenge for clinicians for more than half a century. The aim of this systematic review and meta-analysis is to determine the relative frequency (R.F.) of MRSA in different regions of Iran.

MATERIALS AND METHODS

Search terms "Staphylococcus aureus", "Methicillin", "mecA" and "Iran" were used in PubMed, Scirus and Google Scholar. Two Persian scientific search engines and ten recent national congresses were also explored. Articles/abstracts, which used clinical specimens and had done PCR to detect the mecA gene, were included in this review. Comprehensive Meta-Analysis and Meta-Analyst software were used for statistical analysis.

RESULTS

Out of 2690 results found in the mentioned databases, 48 articles were included in the final analysis. These studies were done in Ahvaz, Falavarjan, Fasa, Gorgan, Hamedan, Isfehan, Kashan, Mashhad, Sanandaj, Shahrekord, Shiraz, Tabriz, Tehran and Tonekabon. Pooled estimation of 7464 S. aureus samples showed that 52.7%±4.7 (95% confidence interval [CI]) of strains were mecA positive. MRSA R.F. in different studies varied from 20.48% to 90% in Isfehan and Tehran, respectively. We found a moderate heterogeneity (I(2)= 48.5%) of MRSA R.F. among studies conducted in Tehran (ranging from 28.88% to 90%, mean 52.7% [95% CI: 46.6%±0.58.8%]).

CONCLUSION

According to the results of this study, MRSA R.F. in Iran is in the high range. Thus, measures should be taken to keep the emergence and transmission of these strains to a minimum.

Nostrils of healthy volunteers are independent with regard to Staphylococcus aureus carriage

The right and left nares of healthy adults (n = 251) were swabbed separately to determine carriage of Staphylococcus aureus in each nostril. Carriers were significantly more likely to carry S. aureus in one nostril than in both. Of those carrying S. aureus in both nostrils, 20% carried genetically distinct strains in each. Nostrils belonging to a single individual should not be assumed to be homogenous with respect to carriage of S. aureus.

Long-term effects of pneumococcal conjugate vaccine on nasopharyngeal carriage of S. pneumoniae, S. aureus, H. influenzae and M. catarrhalis

Background

Shifts in pneumococcal serotypes following introduction of 7-valent pneumococcal conjugate vaccine (PCV-7) may alter the presence of other bacterial pathogens co-inhabiting the same nasopharyngeal niche.

Methodology/Principal Findings

Nasopharyngeal prevalence rates of S. pneumoniae, S. aureus, H. influenzae and M. catarrhalis were investigated before, 3 and 4.5 years after introduction of PCV-7 in the national immunisation program in children at 11 and 24 months of age, and parents of 24-month-old children (n≈330/group) using conventional culture methods. Despite a virtual disappearance of PCV-7 serotypes over time, similar overall pneumococcal rates were observed in all age groups, except for a significant reduction in the 11-month-old group (adjusted Odds Ratio after 4.5 years 0.48, 95% Confidence Interval 0.34–0.67). Before, 3 and 4.5 years after PCV-7 implementation, prevalence rates of S. aureus were 5%, 9% and 14% at 11 months of age (3.59, 1.90–6.79) and 20%, 32% and 34% in parents (1.96, 1.36–2.83), but remained similar at 24 months of age, respectively. Prevalence rates of H. influenzae were 46%, 65% and 65% at 11 months (2.22, 1.58–3.13), 52%, 73% and 76% at 24 months of age (2.68, 1.88–3.82) and 23%, 30% and 40% in parents (2.26, 1.58–3.33), respectively. No consistent changes in M. catarrhalis carriage rates were observed over time.

Conclusions/Significance

In addition to large shifts in pneumococcal serotypes, persistently higher nasopharyngeal prevalence rates of S. aureus and H. influenzae were observed among young children and their parents after PCV-7 implementation. These findings may have implications for disease incidence and antibiotic treatment in the post-PCV era.