Contrasting pediatric and adult methicillin-resistant Staphylococcus aureus isolates

Epidemiological and microbiological characteristics of S. aureus pediatric infections in Colombia 2018-2021, a national multicenter study (Staphylored Colombia)

Background

Staphylococcus aureus infections are a significant cause of morbidity and mortality in pediatric populations worldwide. The Staphylo Research Network conducted an extensive study on pediatric patients across Colombia from 2018 to 2021. The aim of this study was to describe the epidemiological and microbiological characteristics of S. aureus in this patient group.

Methods

We analyzed S. aureus isolates from WHONET-reporting centers. An "event" was a positive culture isolation in a previously negative individual after 2 weeks. We studied center characteristics, age distribution, infection type, and antibiotic susceptibilities, comparing methicillin sensitive (MSSA) and resistant S. aureus (MRSA) isolates.

Results

Isolates from 20 centers across 7 Colombian cities were included. Most centers (80%) served both adults and children, with 55% offering oncology services and 85% having a PICU. We registered 8,157 S. aureus culture isolations from 5,384 events (3,345 MSSA and 1,961 MRSA) in 4,821 patients, with a median age of 5 years. Blood (26.2%) and skin/soft tissue (18.6%) were the most common infection sources. Most isolates per event remained susceptible to oxacillin (63.2%), clindamycin (94.3%), and TMP-SMX (98.3%). MRSA prevalence varied by city (<0.001), with slightly higher rates observed in exclusively pediatric hospitals. In contrast, the MRSA rate was somewhat lower in centers with Antimicrobial Stewardship Program (ASP). MRSA was predominantly isolated from osteoarticular infections and multiple foci, while MSSA was more frequently associated with recurrent infections compared to MRSA.

Conclusions

This is the largest study of pediatric S. aureus infections in Colombia. We found MSSA predominance, but resistance have important regional variations. S. aureus remains susceptible to other commonly used antibiotics such as TMP-SMX and clindamycin. Ongoing monitoring of S. aureus infections is vital for understanding their behavior in children. Prospective studies within the Staphylored LATAM are underway for a more comprehensive clinical and genetic characterization.

Predictive Value of Methicillin-Resistant Staphylococcus aureus Nasal Swab PCR Assay for MRSA Infection in Critically Ill Pediatric Patients

BACKGROUND

Critically ill pediatric patients are frequently initiated methicillin-resistant Staphylococcus aureus (MRSA) active antibiotics during infection evaluation even though MRSA infections are rare in many patient populations. The MRSA nasal swab polymerase chain reaction assay (MRSA-NS-PCR) is a test that has been shown to have a high negative predictive value (NPV) for MRSA infection in adults. This study evaluated the diagnostic test characteristics of the MRSA-NS-PCR in predicting the presence of MRSA infection in critically ill pediatric patients.

STUDY DESIGN

A retrospective cohort study was performed in a 44-bed pediatric intensive care unit (PICU) between 2013 and 2017. 3860 pediatric patients (54% male, median age 4 years [IQR 1-11 years]) admitted to the PICU who met pediatric systemic inflammatory response syndrome (pSIRS) criteria, were screened with a MRSA-NS-PCR, and had cultures obtained within seven days of MRSA-NS-PCR collection were included. Predictive values and post-test probabilities of the MRSA-NS-PCR for MRSA infection were calculated.

RESULTS

MRSA-NS-PCR was positive in 8.6% of patients. MRSA infection was identified in 40 patients, equaling an incidence rate of 2 per 1000 patient days. The MRSA-NS-PCR demonstrated a positive predictive value (PPV) of 9.7%, a NPV of 99.8%, and a post-test probability for a negative test of 0.2% for MRSA infection.

CONCLUSIONS

The MRSA-NS-PCR has a poor PPV but a high NPV for MRSA infection in PICU patients when the incidence of MRSA infection is low. Creation of protocols to guide antimicrobial selection based on MRSA-NS-PCR results may lead to improved antimicrobial stewardship and significant risk reduction.

Phylogenetic Analysis and Virulence Characteristics of Methicillin-Resistant Staphylococcus aureus ST45 in China: a Hyper-Virulent Clone Associated with Bloodstream Infections

Methicillin-resistant Staphylococcus aureus (MRSA) sequence type 45 (ST45) was rarely found in China. This study was conducted to trace the transmission and evolution of emerging MRSA ST45 strains in mainland China and explore its virulence. A total of 27 ST45 isolates were included for whole-genome sequencing and genetic characteristic analysis. Epidemiological results showed that MRSA ST45 isolates were often obtained from blood, primarily originated in Guangzhou, and carried diverse virulence and drug resistance genes. Staphylococcal cassette chromosome mec type IV (SCCmec IV) dominated in MRSA ST45 (23/27, 85.2%). ST45-SCCmec V was located on a phylogenetic clade distinct from the SCCmec IV cluster. We selected two representative isolates, MR370 (ST45-SCCmec IV) and MR387 (ST45-SCCmec V), and performed hemolysin activity, a blood killing assay, a Galleria mellonella infection model, and a mouse bacteremia model, as well as real-time fluorescence quantitative PCR. MR370 was proved to have extreme virulence in the phenotypic assays and at the mRNA level compared with ST59, ST5, and USA300 MRSA strains. MR387 was comparable to USA300-LAC on the phenotype and was verified to have higher expression of scn, chp, sak, saeR, agrA, and RNAIII than USA300-LAC. The results emphasized the extraordinary performance of MR370 and the good potential of MR387 in virulence causing bloodstream infection. Meanwhile, we conclude that China MRSA ST45 showed two different clonotypes, which may be widespread in the future. The entire study is valuable as a timely reminder and reports virulence phenotypes of China MRSA ST45 for the first time. IMPORTANCE Methicillin-resistant Staphylococcus aureus ST45 is epidemic worldwide. This study contributed to the awareness of the Chinese hyper-virulent MRSA ST45 strains and served as a timely reminder of its wide dissemination of clonotypes. Further, we provide novel insights for prevention from the perspective of bloodstream infections. ST45-SCCmec V is a clonotype deserving special attention in China, and we performed genetic and phenotypic analyses for the first time on it.

Therapeutic Drug Monitoring of Antibiotics in the Elderly: A Narrative Review

PURPOSE

Antibiotic dosing adaptation in elderly patients is frequently complicated by age-related changes affecting the processes of drug absorption, distribution, metabolism, and/or elimination. These events eventually result in treatment failure and/or development of drug-related toxicity. Therapeutic drug monitoring (TDM) can prevent suboptimal antibiotic exposure in adult patients regardless of age. However, little data are available concerning the specific role of TDM in the elderly.

METHODS

This review is based on a PubMed search of the literature published in the English language. The search involved TDM studies of antibiotics in the elderly performed between 1990 and 2021. Additional studies were identified from the reference lists of the retrieved articles. Studies dealing with population pharmacokinetic modeling were not considered.

RESULTS

Only a few studies, mainly retrospective and with observational design, have specifically dealt with appropriate antibiotic dosing in the elderly based on TDM. Nevertheless, some clinical situations in which the selection of optimal antibiotic dosing in the elderly was successfully guided by TDM were identified.

CONCLUSIONS

Elderly patients are at an increased risk of bacterial infections and inadequate drug dosing compared to younger patients. Therefore, the availability of TDM services can improve the appropriateness of antibiotic prescriptions in this population.

Use of the Electronic Health Record to Optimize Antimicrobial Prescribing

PURPOSE

This review summarizes how interventions in the electronic health record (EHR) can optimize antimicrobial stewardship across the continuum of antimicrobial decision making, from diagnosis of infection to discontinuation of therapy. In addition, opportunities to optimize provider communication and patient education are identified.

METHODS

A narrative review was conducted to identify how interventions in the EHR can influence antimicrobial prescribing behavior. Examples from pediatrics were specifically identified. Interventions were then categorized into high-impact/low-effort, high-impact/high-effort, and low-impact/low-effort groupings based on historical experience.

FINDINGS

EHR-based interventions can be used for stratifying patients at risk for infection and are useful in identifying patients with new-onset infections. Additional tools include automatically updated antibiograms tailored to specific patient populations, timely authorization of restricted antimicrobials, and more accurate allergy labeling. Medical errors can be reduced and communication between providers can be improved by standardized data fields. Clinical decision support tools can guide appropriate selection of therapy, and visual prompts can reduce unnecessarily prolonged therapy. Benchmarking of antimicrobial use, tailored patient education, and improved communication during transitions of care are enhanced through EHR-based interventions.

IMPLICATIONS

Prescribing behavior can be modified through a range of interventions in the EHR, including tailored education, alerts, prompts, and restrictions on provider behavior. Further studies are needed to compare the effectiveness of various strategies.

Linking antimicrobial resistance surveillance to antibiotic policy in healthcare settings: the COMBACTE-Magnet EPI-Net COACH project

OBJECTIVES

To systematically summarize the evidence on how to collect, analyse and report antimicrobial resistance (AMR) surveillance data to inform antimicrobial stewardship (AMS) teams providing guidance on empirical antibiotic treatment in healthcare settings.

METHODS

The research group identified 10 key questions about the link between AMR surveillance and AMS using a checklist of 9 elements for good practice in health research priority settings and a modified 3D combined approach matrix, and conducted a systematic review of published original studies and guidelines on the link between AMR surveillance and AMS.

RESULTS

The questions identified focused on AMS team composition; minimum infrastructure requirements for AMR surveillance; organisms, samples and susceptibility patterns to report; data stratification strategies; reporting frequency; resistance thresholds to drive empirical therapy; surveillance in high-risk hospital units, long-term care, outpatient and veterinary settings; and surveillance data from other countries. Twenty guidelines and seven original studies on the implementation of AMR surveillance as part of an AMS programme were included in the literature review.

CONCLUSIONS

The evidence summarized in this review provides a useful basis for a more integrated process of developing procedures to report AMR surveillance data to drive AMS interventions. These procedures should be extended to settings outside the acute-care institutions, such as long-term care, outpatient and veterinary. Without proper AMR surveillance, implementation of AMS policies cannot contribute effectively to the fight against MDR pathogens and may even worsen the burden of adverse events from such interventions.

Antimicrobial Resistance Profile and Molecular Characteristics of Staphylococcus aureus Isolates from Hospitalized Adults in Three Regions of Vietnam

This study aimed to investigate antimicrobial resistance profile, multidrug resistance (MDR), and molecular characteristics of pathogenic Staphylococcus aureus isolates from hospitalized Vietnamese adults. Two hundred and twenty-three pathogenic S. aureus isolates were obtained from the hospitals located in 3 regions of Vietnam. The minimum inhibitory concentrations were determined to detect the antibiotic susceptibility of the isolates. The molecular characteristics of S. aureus isolates were investigated through antibiotic-resistant genes analysis, staphylococcal cassette chromosome mec typing, pulsed-field gel electrophoresis, and multilocus sequence typing. Substantial differences among the 3 regions were found in the prevalence rates of methicillin-resistant S. aureus (north: 48.6%, central: 58.7%, south: 78.9%) and MDR (north: 65.8%, central: 79.7%, and south: 84.2%). The prevalence rates of the genes tetK/M, aacA/aphD, ermA/B/C, and mecA increased substantially from north to south. ST188-SCCmecIV and ST239-SCCmecII isolates were most commonly found in the 2 largest clusters. ST188 predominance was observed in the largest cluster in methicillin-resistant and methicillin-sensitive S. aureus isolates, including SCCmecIII and SCCmecIVa, in fatal cases. Our results revealed a high occurrence of MDR and possible north-south trend in antibiotic resistance profile, MDR patterns, and frequency of antibiotic-conferring genes among S. aureus isolates. ST188 predominance raises concerns about the global importance of host-adapted ST188 in East Asian populations.

Staphylococcus aureus Resistance Patterns in Wisconsin: 2018 Surveillance of Wisconsin Organisms for Trends in Antimicrobial Resistance and Epidemiology (SWOTARE) Program Report

OBJECTIVE

Surveillance of antimicrobial resistance patterns on a local level can reveal paradigms not obvious on a regional or national scale. Data collection from this perspective may potentially impact local prescribing patterns and empiric treatment guidelines. The objective of this study was to establish a baseline Staphylococcus aureus antibiogram for the state of Wisconsin and to elucidate potential geographic and demographic factors associated with antimicrobial resistance.

DESIGN

Multi-center laboratory surveillance, with testing at a single site utilizing standardized media and susceptibility testing protocols.

METHODS

309 isolates of clinically-significant S. aureus were collected from hospital microbiology laboratories across Wisconsin in 2018, with distribution across seven geographic regions. Each isolate was tested using reference broth microdilution methods against a panel of 15 antimicrobial agents. Percentage susceptibility data, as well as median and 90th percentile minimum inhibitory concentration (MIC) values, were computed for each antimicrobial agent as a function of geographic region or demographic category.

RESULTS

Increased resistance to penicillin (≥ 86.0% of isolates), erythromycin (≥ 56.8%), cefoxitin (≥ 45.5%), levofloxacin (≥ 25.0%), and clindamycin (≥ 20.5%) was observed in the Southcentral, Lake Winnebago, and Southeast regions of Wisconsin. In addition, isolates phenotypically classified as methicillin-resistant S. aureus (MRSA) were found to have increased rates of resistance to clindamycin, erythromycin, and levofloxacin as compared to S. aureus isolates susceptible to cefoxitin. S. aureus isolates demonstrated nearly 100% in vitro susceptibility to ceftaroline, dalbavancin, and telavancin. Statewide S. aureus isolates exhibited a vancomycin MIC₉₀ of 1 μg/mL. S. aureus isolates from patients aged 20-39 years were more likely to demonstrate cefoxitin resistance when compared to other age groups (P ≤ 0.03), while isolates from patients ≥ 80 years were more likely to exhibit resistance to levofloxacin and clindamycin (P ≤ 0.046).

CONCLUSIONS

Several antimicrobial agents continue to demonstrate in vitro efficacy against clinical isolates of S. aureus (including MRSA) throughout Wisconsin, including three agents with recently-published susceptibility testing guidelines. However, continued surveillance efforts may be necessary in the Lake Winnebago, Southeast, and Southcentral regions to further assess higher rates of resistance to a number of antimicrobial agents.

Regional outbreak of community-associated methicillin-resistant Staphylococcus aureus ST834 in Japanese children

Background

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infection has recently become a challenging problem worldwide and in Japan. We experienced 10 pediatric patients infected with CA-MRSA and hospitalized from 2011 to 2014 in a tertiary care hospital in Saitama, Japan, and assessed the characteristic of the strains using a whole genome sequencing (WGS)-based approach.

Methods

CA-MRSA strains isolated from infected patients who required hospitalization for treatment were evaluated in this study. Antimicrobial susceptibility tests, molecular typing by PCR and pulse-field gel electrophoresis (PFGE) were performed to characterize MRSA strains. WGS was performed for detailed genetic analysis.

Results

A total of 582 MRSA strains (35.2%) were identified among 1625 S. aureus strains collected during the study period. Ten MRSA strains (1.7%) were defined as CA-MRSA clinically, and all were isolated from pediatric patients. All strains mainly caused purulent lymphadenitis, were susceptible to fluoroquinolone and tetracycline, exhibited sequence type (ST) 834 or its single-locus variants and contained staphylococcal cassette chromosome mec (SCCmec) type IVc. Phylogenic analysis by PFGE and WGS revealed close relatedness of all strains, with the number of single nucleotide polymorphisms ranging from 35 to 119 by WGS. Out of the ten strains, nine possessed the genomic island SaPISaitama2 containing tst, sec and sel genes. SaPISaitama2 comprises a mosaic of genomic islands SaPIm4 and SaPIm1 harbored by a hospital-associated MRSA strain Mu50.

Conclusions

This study describes a regional outbreak of ST834-related CA-MRSA in children with a unique pathogenicity island in Japan. Pediatric patient tropism of this clone could be enhanced by susceptibility to fluoroquinolones and tetracyclines, which cannot be prescribed to children.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3646-z) contains supplementary material, which is available to authorized users.

S. aureus Infections in Chicago, 2006-2014: Increase in CA MSSA and Decrease in MRSA Incidence

OBJECTIVE To examine trends in Staphylococcus aureus infections in adults and children at a single academic center in 2006-2014. DESIGN Retrospective cohort study. SETTING Inpatient, outpatient, and emergency department settings in a private, tertiary referral center. PATIENTS Patients with an infection culture that grew S. aureus in January 1, 2006, through March 31, 2014. METHODS The first isolate per year for each patient was classified as community-associated (CA-), healthcare-associated (HA-), or HA-community-onset S. aureus. The incidence density of S. aureus, methicillin-susceptible S. aureus (MSSA), and methicillin-resistant S. aureus (MRSA) infections were calculated per quarter year. RESULTS Overall, 5,491 MRSA and 5,398 MSSA isolates were included. MRSA infections decreased by an average of 5.2% annually (P<.001). MRSA skin and soft-tissue infection (SSTI) incidence density decreased in adults (-3.5%; P<.001) and children (-2.9%; P=.004). MSSA infections at all anatomic sites increased by an average of 1.9% annually (P=.007) in adults and decreased 5.1% annually (P<.001) in children. MSSA SSTI incidence density increased in adults (+3.8%; P<.001) and children (+5.6%; P<.001). For MRSA and MSSA SSTI isolates, susceptibility to tetracycline and clindamycin decreased significantly. CONCLUSIONS In 2006-2014, MRSA SSTI incidence decreased among children and adults. MSSA SSTI incidence density increased in children and adults, suggesting that current empiric SSTI treatment recommendations may not be optimal. Adults experienced an overall increase in MSSA infections, which may prompt consideration of the need for horizontal infection control practices to decrease MSSA infection risk. Infect Control Hosp Epidemiol 2017;38:1226-1234.

Molecular epidemiology of Panton-Valentine Leukocidin-positive community-acquired methicillin resistant Staphylococcus aureus isolates in pastoral communities of rural south western Uganda

Background

The emergence of multidrug resistant Staphylococcus aureus strains, including methicillin resistant (MRSA), is a global concern. Treatment of bacterial infections in Uganda’s health care settings is largely empirical, rarely accompanied by laboratory confirmation. Here we show the burden, characteristics of MRSA and epidemiology of Panton-Valentine Leukocidin (PVL) positive strains in asymptomatic carriers in pastoral households of south-west Uganda.

Methods

Nasal swabs from 253 participants were cultured following standard methodology. MRSA strains were identified by detection of the mecA gene and SCCmec typing, and PVL genes detected by PCR. Pulsed Field Gel Electrophoresis (PFGE) was done to evaluate possible transmission patterns. Spa typing of PVL positive isolates was done to study the epidemiology of virulent strains in this setting.

Results

S. aureus was isolated in 29% (n = 73) of the participants, of which 48 were MRSA by mecA typing. PVL-encoding genes were found in 49.3% (n = 36) of the 73 isolates, of which 25 were also mecA positive. Among the PVL negative strains (n = 37), 62.2% (n = 23) carried the mecA gene. The most common SCCmec type was V, detected in 39 (18 PVL positive and 21 PVL negative) isolates. PFGE clustered 21/36 (58.3%) PVL positive isolates divided in four pulsotypes and 18/37 (48.6%) PVL negative isolates divided in eight pulsotypes. The most prevalent Spa types were t318 (26.5%, n = 9) and t645 (20.6%, n = 7); while other common Spa types were t11656 (n = 3), t127 (n = 3) and t355 (n = 3).

Conclusion

The study shows a high prevalence of community acquired (CA)-MRSA, and PVL-positive isolates with two predominant spa types in rural Uganda, further complicating infection control strategies in these underprivileged communities.

Antimicrobial resistance of Staphylococcus aureus isolated from skin infections and its implications in various clinical conditions in Korea

BACKGROUND

Periodic investigations into patterns of antimicrobial resistance can help to optimize the efficacy of treatment and limit the development of resistance.

OBJECTIVES

The aim of this study was to update information on patterns of antimicrobial resistance in Staphylococcus aureus isolated from skin infections in South Korea.

METHODS

We retrospectively analyzed clinical information and in vitro antimicrobial resistance data for 965 clinical S. aureus isolates obtained from skin infections during 2010-2013 in a university hospital in South Korea.

RESULTS

The rate of resistance to oxacillin (methicillin-resistant S. aureus [MRSA]) was 47.4%. Similar rates of resistance to erythromycin (45.6%), fusidic acid (44.0%), and clindamycin (42.3%) were noted. The rate of resistance to mupirocin was 8.4%. Overall, 4.9% of isolates were resistant to both fusidic acid and mupirocin. None of the isolates showed resistance to habekacin, synercid, teicoplanin, or vancomycin. Generally, antimicrobial resistance rates did not increase from 2010 to 2013 except with reference to a few agents such as mupirocin and rifampin. Isolates from surgical patients, inpatients, non-dermatology outpatients, and adult patients showed relatively high rates of resistance to multiple antimicrobials. Resistance to mupirocin was not only lower than that to fusidic acid but was consistent across clinical contexts.

CONCLUSIONS

The prevalence of MRSA in skin infections in South Korea did not increase during 2010-2013. Isolates from dermatology outpatients showed relatively lower rates of resistance to multiple antimicrobials than isolates from non-dermatology outpatients. Among topical antimicrobials, resistance to mupirocin was relatively low regardless of clinical condition.

Pathogens causing urinary tract infections in infants: a European overview by the ESCAPE study group

Knowledge of the distribution spectrum of causative organisms and their resistance patterns has become a core requirement for the rational and effective management of urinary tract infections. In the context of a prospective trial on the use of antibiotic prophylaxis in infants with underling kidney malformations, we conducted an online survey among paediatric nephrologists on positive urine cultures (July 2010-June 2012) from both hospitalized and non-hospitalized infants under 24 months of age. We collected 4745 urine cultures (UCs) at 18 units in 10 European countries. Escherichia coli was the most frequent bacterium isolated from UCs; however, in 10/16 hospitals and in 6/15 community settings, E. coli was isolated in less than 50% of the total positive UCs. Other bacterial strains were Klebsiella, Enterococcus, Proteus and Pseudomonas not only from hospital settings. E. coli showed a high resistance to amoxicillin and trimethoprim and variable to cephalosporin. Nitrofurantoin had a good rate of efficacy, with 11/16 hospitals and 11/14 community settings reporting a resistance lower than 5%.

CONCLUSION

E. coli is the most common organism causing UTIs in infants; however, other bacterial strains are frequently isolated. As a result, antibiotic prophylaxis should be more elastic and adaptable over time in order to guarantee maximum efficacy.

Pediatric Antimicrobial Susceptibility Trends across the United States

Objective.

Antimicrobial susceptibility patterns across US pediatric healthcare institutions are unknown. A national pooled pediatric antibiogram (1) identifies nationwide trends in antimicrobial resistance, (2) allows across-hospital benchmarking, and (3) provides guidance for empirical antimicrobial regimens for institutions unable to generate pediatric antibiograms.

Methods.

In January 2012, a request for submission of pediatric antibiograms between 2005 and 2011 was sent to 233 US hospitals. A summary antibiogram was compiled from participating institutions to generate proportions of antimicrobial susceptibility. Temporal and regional comparisons were evaluated using χ² tests and logistic regression, respectively.

Results.

Of 200 institutions (85%) responding to our survey, 78 (39%) reported generating pediatric antibiograms, and 55 (71%) submitted antibiograms. Carbapenems had the highest activity against the majority of gram-negative organisms tested, but no antibiotic had more than 90% activity against Pseudomonas aeruginosa. Approximately 50% of all Staphylococcus aureus isolates were methicillin resistant. Western hospitals had significantly lower proportions of S. aureus that were methicillin resistant compared with all other regions tested. Overall, 21% of S. aureus isolates had resistance to clindamycin. Among Enterococcus faecium isolates, the prevalence of susceptibility to ampicillin (25%) and vancomycin (45%) was low but improved over time (P < .01), and 8% of E. faecium isolates were resistant to linezolid. Southern hospitals reported significantly higher prevalence of E. faecium with susceptibilities to ampicillin, vancomycin, and linezolid compared with the other 3 regions (P < .01).

Conclusions.

A pooled, pediatric antibiogram can identify nationwide antimicrobial resistance patterns for common pathogens and might serve as a useful tool for benchmarking resistance and informing national prescribing guidelines for children.

Invasive community-acquired Staphylococcus aureus among pediatric population of Eastern Iran

BACKGROUND AND OBJECTIVE

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is increasingly reported worldwide. We aimed to determine the frequency of invasive CA-MRSA in children admitted to the pediatric wards of Imam Reza and Ghaem hospitals of Mashhad, Iran.

MATERIALS AND METHODS

In this retrospective study, data regarding S. aureus isolates from pediatric patients' sterile body sites (i.e. blood' joint, bone and lymph node aspiration) were retrieved in a time period from March 2006 to March 2012. Disc diffusion data was analyzed to determine the resistance pattern of the isolates, and differentiation between community-acquired and nosocomial S. aureus was done according to CDC guidelines.

RESULTS

Twenty three invasive community-acquired S. aureus isolates from sterile body sites were identified, of which seventeen (74%) were CA-MRSA. The CA-MRSA isolates showed high frequency of resistance to non-β-lactam antibiotics (71% to erythromycin' 53% to co-trimoxazole, 44% to gentamicin and 36% to ciprofloxacin).

CONCLUSION

In this study, the majority of invasive community-acquired S. aureus isolates were found to be CA-MRSA. Therefore, we recommend that primary treatment should be with antibiotics such as clindamycin, vancomycin, linezolid or daptomycin for any invasive infection suspected to be caused by S. aureus in these two hospitals.

All purulence is local - epidemiology and management of skin and soft tissue infections in three urban emergency departments

BACKGROUND

Skin and soft tissue infection (SSTIs) are commonly treated in emergency departments (EDs). While the precise role of antibiotics in treating SSTIs remains unclear, most SSTI patients receive empiric antibiotics, often targeted toward methicillin-resistant Staphylococcus aureus (MRSA). The goal of this study was to assess the efficiency with which ED clinicians targeted empiric therapy against MRSA, and to identify factors that may allow ED clinicians to safely target antibiotic use.

METHODS

We performed a retrospective analysis of patient visits for community-acquired SSTIs to three urban, academic EDs in one northeastern US city during the first quarter of 2010. We examined microbiologic patterns among cultured SSTIs, and relationships between clinical and demographic factors and management of SSTIs.

RESULTS

Antibiotics were prescribed to 86.1% of all patients. Though S. aureus (60% MRSA) was the most common pathogen cultured, antibiotic susceptibility differed between adult and pediatric patients. Susceptibility of S. aureus from ED SSTIs differed from published local antibiograms, with greater trimethoprim resistance and less fluoroquinolone resistance than seen in S. aureus from all hospital sources. Empiric antibiotics covered the resultant pathogen in 85.3% of cases, though coverage was frequently broader than necessary.

CONCLUSIONS

Though S. aureus remained the predominant pathogen in community-acquired SSTIs, ED clinicians did not accurately target therapy toward the causative pathogen. Incomplete local epidemiologic data may contribute to this degree of discordance. Future efforts should seek to identify when antibiotic use can be narrowed or withheld. Local, disease-specific antibiotic resistance patterns should be publicized with the goal of improving antibiotic stewardship.

Comparison of hospital-wide and age and location - stratified antibiograms of S. aureus, E. coli, and S. pneumoniae: age- and location-stratified antibiograms

Background

Antibiograms created by aggregating hospital-wide susceptibility data from diverse patients can be misleading. To demonstrate the utility of age- and location-stratified antibiograms, we compared stratified antibiograms for three common bacterial pathogens, E. coli, S. aureus, and S. pneumoniae. We created stratified antibiograms based on patient age (<18 years, 18–64 years, >/=65 years), and inpatient or outpatient location using all 2009 E. coli and S. aureus, and all 2008–2009 S. pneumoniae isolates submitted to our clinical microbiology laboratory. We compared susceptibility rates among cumulative and stratified antibiograms using descriptive statistics.

Findings

For E. coli and S. aureus, the institution-wide antibiogram overestimated resistance in pediatic isolates and underestimated resistance in isolates from the elderly. For E. coli, pediatric isolates were less susceptible to ampicillin and ampicillin-sulbactam and more susceptible to gentamicin and ciprofloxacin compared to adult isolates (p < 0.05 for all), and isolates from patients >65 years were least susceptible to ciprofloxacin (71%). For S. aureus, susceptibility to oxacillin, clindamycin, and levofloxacin was highest among children and decreased with increasing age (p < .001 for all). For S. pneumoniae, pediatric isolates were less susceptible than adult isolates to all agents except penicillin (IV breakpoint). Within children there were significant differences in susceptibility of inpatient and outpatient isolates of E. coli but not of S. aureus or S. pneumoniae.

Conclusions

Stratified antibiograms reveal age - associated differences in susceptibility of E. coli, S. aureus, and S. pneumoniae that are obscured by hospital-wide antibiograms. Age-stratified antibiograms have potential to influence antibiotic selection.

Pediatric-specific antimicrobial susceptibility data and empiric antibiotic selection

OBJECTIVE

Duke University Health System (DUHS) generates annual antibiograms combining adult and pediatric data. We hypothesized significant susceptibility differences exist for pediatric isolates and that distributing these results would alter antibiotic choices.

METHODS

Susceptibility rates for Escherichia coli isolates from patients aged ≤12 years between July 2009 and September 2010 were compared with the 2009 DUHS antibiogram. Pediatric attending and resident physicians answered case-based vignettes about children aged 3 months and 12 years with urinary tract infections. Each vignette contained 3 identical scenarios with no antibiogram, the 2009 DUHS antibiogram, and a pediatric-specific antibiogram provided. Effective antibiotics exhibited >80% in vitro susceptibility. Frequency of antibiotic selection was analyzed by using descriptive statistics.

RESULTS

Three hundred seventy-five pediatric isolates were identified. Pediatric isolates were more resistant to ampicillin and trimethoprim-sulfamethoxazole (TMP-SMX) and less resistant to amoxicillin-clavulanate and ciprofloxacin (P < .0005 for all). Seventy-five resident and attending physicians completed surveys. In infant vignettes, physicians selected amoxicillin-clavulanate (P < .05) and nitrofurantoin (P < .01) more often and TMP-SMX (P < .01) less often with pediatric-specific data. Effective antibiotic choices increased from 68.6% to 82.2% (P = .06) to 92.5% (P < .01) across scenarios. In adolescent vignettes, providers reduced TMP-SMX use from 66.2% to 42.6% to 19.0% (P < .01 for both). Effective antibiotic choices increased from 32.4% to 57.4% to 79.4% (P < .01 and P = .01).

CONCLUSIONS

Pediatric E. coli isolates differ significantly in antimicrobial susceptibility at our institution, particularly to frequently administered oral antibiotics. Knowledge of pediatric-specific data altered empirical antibiotic choices in case vignettes. Care of pediatric patients could be improved with use of a pediatric-specific antibiogram.

Activity analyses of staphylococcal isolates from pediatric, adult, and elderly patients: AWARE Ceftaroline Surveillance Program

Ceftaroline, the active metabolite of the prodrug ceftaroline fosamil, is a broad-spectrum cephalosporin with bactericidal activity against resistant Gram-positive organisms, including methicillin-resistant Staphylococcus aureus (MRSA), and common Gram-negative organisms. We evaluated the activity of ceftaroline and various antimicrobial agents against S. aureus isolates according to patient age. A total of 2143 consecutive unique patient strains of clinical significance were collected between January and December 2010 from 65 US medical centers as part of the Assessing Worldwide Antimicrobial Resistance Evaluation (AWARE) Program. Ceftaroline and various comparator agents were tested by reference Clinical and Laboratory Standards Institute broth microdilution methods. Ceftaroline was consistently active against methicillin-susceptible S. aureus (MSSA) (MIC(50), 0.25 μg/mL; MIC(90), 0.25 μg/mL; 100.0% susceptible) and MRSA (MIC(50), 0.50 μg/mL, MIC(90), 1 μg/mL; 98.4% susceptible) from all age groups. In general, resistance rates to erythromycin, clindamycin, and levofloxacin were higher in the population aged ≥ 65 years, whereas resistance rates to clindamycin and levofloxacin were lowest among isolates from patients aged 6-17 years. When tested against MSSA, levofloxacin resistance was higher among isolates from patients aged ≥ 65 years (16.1%) than among isolates from the other age groups (6.1%-10.5%), and ceftaroline was generally 16-fold more active than ceftriaxone (MIC(50), 4 μg/mL; MIC(90), 4 μg/mL; 97.9% susceptible overall). Ceftaroline (MIC(50), 0.50 μg/mL; MIC(/90), 1 μg/mL), daptomycin (MIC(50), 0.25 μg/mL; MIC(90), 0.5 μg/mL), linezolid (MIC(50), 1 μg/mL; MIC(90), 1 μg/mL), and vancomycin (MIC(50), 1 μg/mL(;) MIC(90), 1 μg/mL) were the most active compounds tested against MRSA strains, and the activity of these compounds did not vary significantly among the age groups. In contrast, susceptibility rates to clindamycin and levofloxacin varied from 94.0% and 60.7% (aged 6-17 years), respectively, to only 57.6% and 15.1% (aged ≥ 65 years), respectively, among MRSA strains. The results of this study showed major differences in the susceptibility rates to clindamycin and levofloxacin according to patient age group. The results also indicate that ceftaroline is highly active against MSSA and MRSA isolated from US medical centers, independent of patient age group.

The increasing prevalence of clindamycin resistance in Staphylococcus aureus isolates in children with head and neck abscesses

OBJECTIVE

To retrospectively review trends in clindamycin resistance among Staphylococcus aureus head and neck abscesses between January 2000 and June 2008.

METHODS

Between January 2000 and June 2008, inpatient and out-patient S aureus isolates were reviewed for antibiotic susceptibility. In particular, cultures from 153 abscesses in the head and neck region were assessed for clindamycin and methicillin resistance patterns.

RESULTS

Annual clindamycin resistance rates for all S aureus isolates, and specifically for S aureus head and neck abscesses, revealed concerning levels of clindamycin and methicillin resistance. After 2002, the mean clindamycin resistance rate in head and neck abscesses was approximately 27%. The number of new cases of methicillin-resistant S aureus per year increased from four cases in 2000 to 44 cases in 2007.

CONCLUSION

Antibiotic resistance should be considered following failed empirical therapy of head and neck abscesses with clindamycin.

Multidrug-resistant clones of community-associated meticillin-resistant Staphylococcus aureus isolated from Chinese children and the resistance genes to clindamycin and mupirocin

This study aimed to correlate the multidrug resistance (MDR) and sequence type (ST) clones of community-associated (CA) meticillin-resistant Staphylococcus aureus (MRSA) to identify the genes responsible for clindamycin and mupirocin resistance in S. aureus isolates from paediatric hospitals in mainland China. A total of 435 S. aureus isolates were collected. Compared with CA meticillin-susceptible S. aureus (MSSA), the resistance rates of CA-MRSA to ciprofloxacin, chloramphenicol, gentamicin and tetracycline were higher (19.0 vs 2.6 %, P<0.001; 14.7 vs 3.1 %, P<0.001; 14.7 vs 3.1 %, P<0.01; and 46.0 vs 13.3 %, P<0.001, respectively). Compared with hospital-associated (HA)-MRSA, the resistance rates of CA-MRSA to ciprofloxacin, gentamicin, rifampicin, tetracycline and trimethoprim-sulfamethoxazole were lower (19 vs 94.8 %, P<0.001; 14.7 vs 84.4 %, P<0.001; 5.5 vs 88.3 %, P<0.001; 46 vs 94.8 %, P<0.001; and 1.8 vs 9.1 %, P<0.01, respectively). The resistance rates of CA-MRSA, HA-MRSA and CA-MSSA to clindamycin (92.0, 77.9 and 64.1 %, respectively) and erythromycin (85.9, 77.9 and 63.1 %, respectively) were high. The MDR rates (resistance to three or more non-β-lactams) were 49.6, 100 and 14 % in the CA-MRSA, HA-MRSA and CA-MSSA isolates, respectively. Five of seven ST clones in the CA-MRSA isolates, namely ST59, ST338, ST45, ST910 and ST965, had MDR rates of >50 % (67.9, 87.5, 100, 50 and 83.3 %, respectively). The constitutive phenotype of macrolide-lincosamide-streptogramin B (MLS(B)) resistance (69 %) and the ermB gene (38.1 %) predominated among the MLS(B)-resistant CA S. aureus strains. The resistance rate to mupirocin was 2.3 % and plasmids carrying the mupA gene varied in size between 23 and 54.2 kb in six strains with high-level resistance as determined by Southern blot analysis. The present study showed that resistance to non-β-lactams, especially to clindamycin, is high in CA-MRSA isolates from Chinese children and that the profile of resistance is related to clonal type. This study revealed distinctive patterns of MLS(B)-resistant genes among CA S. aureus isolates.

Differences in methicillin-resistant Staphylococcus aureus strains isolated from pediatric and adult patients from hospitals in a large county in California

Studies of U.S. epidemics of community- and health care-associated methicillin-resistant Staphylococcus aureus (MRSA) suggested differences in MRSA strains in adults and those in children. Comprehensive population-based studies exploring these differences are lacking. We conducted a prospective cohort study of inpatients in Orange County, CA, collecting clinical MRSA isolates from 30 of 31 Orange County hospitals, to characterize differences in MRSA strains isolated from children compared to those isolated from adults. All isolates were characterized by spa typing. We collected 1,124 MRSA isolates from adults and 159 from children. Annual Orange County population estimates of MRSA inpatient clinical cultures were 119/100,000 adults and 22/100,000 children. spa types t008, t242, and t002 accounted for 83% of all isolates. The distribution of these three spa types among adults was significantly different from that among children (χ(2) = 52.29; P < 0.001). Forty-one percent of adult isolates were of t008 (USA300), compared to 69% of pediatric isolates. In multivariate analyses, specimens from pediatric patients, wounds, non-intensive care unit (ICU) wards, and hospitals with a high proportion of Medicaid-insured patients were significantly associated with the detection of t008 strains. While community- and health care-associated MRSA reservoirs have begun to merge, significant differences remain in pediatric and adult patient populations. Community-associated MRSA spa type t008 is significantly more common in pediatric patients.

Molecular analysis of community-acquired methicillin-susceptible and resistant Staphylococcus aureus isolates recovered from bacteraemic and osteomyelitis infections in children from Tunisia

Thirty-six children (27 boys, nine girls) that fulfilled CDC criteria for community-acquired infections were diagnosed with bacteraemia and/or osteomyelitis caused by Staphylococcus aureus during an 18-month period (2006-2008). Antibiotic susceptibility was determined by an agar dilution method. SCCmec type, carriage of pvl genes, agr type and spa-typing were determined using specific PCR protocols. Clonal relatedness was examined by pulsed field gel electrophoresis-SmaI and mutilocus sequence typing techniques. From the 36 isolates, eight (22%) corresponded to methicillin-resistant Staphylococcus aureus (MRSA) -t044/042-CC80/CC5-IVc-pvl(+) -agrIII/II. The highest genetic diversity was observed among the 28 community-acquired methicillin-susceptible S. aureus (CA-MSSA) isolates: 22 spa-variants that also grouped by multilocus sequence typing in CC1, CC5, CC6, CC8, CC30, CC80, CC97 and the singletons ST464, ST1467, ST1468 and ST1469. The pvl genes were detected in all eight CA-MRSA isolates and in eight CA-MSSA isolates (28%), being significantly more frequent among isolates causing osteoarticular infection (11 of 12, 92%) than in the bacteraemic isolates (six of 24, 25%). Based on patients' age, three groups were considered: newborns, infants and children. Bacteraemia was diagnosed in all newborns and infants, whereas in 42% of the children group osteomyelitis was the unique presentation. In most cases, the portal of entry was either the skin or unknown. In general, favourable outcome was observed, except in four cases-three of whom had severe complications and one died. In summary, we analysed the epidemiological and genetic background of community-acquired staphylococcal strains causing bacteraemic and/or osteomyelitis infections in children from Tunisia, describing three new sequence types and one novel spa type.

Reliability of the BD GeneOhm methicillin-resistant Staphylococcus aureus (MRSA) assay in detecting MRSA isolates with a variety of genotypes from the United States and Taiwan

The BD GeneOhm methicillin-resistant Staphylococcus aureus (MRSA) assay is a molecular screening test for detection of MRSA in nasal colonization. This assay coamplifies the extremity of staphylococcal chromosome cassette mec (SCCmec) and adjacent chromosomal DNA at the SCCmec insertion site. Increasing reports of novel SCCmec types and the diverse genetic backgrounds of MRSA strains prompted us to test the accuracy of the BD GeneOhm MRSA kit with 914 MRSA isolates with a variety of SCCmec types harbored in 21 genetic backgrounds, as determined by the multilocus sequence type (ST). The BD GeneOhm MRSA assay was performed on colony lysates; purified genomic DNA (0.2 pg/μl and 0.2 ng/μl) was tested to confirm negative results from lysates. Of 914 MRSA isolates tested, 911 tested positive (detection rate, 99.7%). The SCCmec types carried by assay-positive isolates were I, II, III, IV, V, V(5C2&5), VI, and VIII and SCCmec composite islands with mec class A and ccr complexes 2 and 4. One of the assay-negative isolates had a community-associated genotype: ST8, SCCmec type IV. However, this was an outlier among the 99.8% (434/435) ST8, SCCmec type IV-containing isolates that tested positive. The two other assay-negative isolates had a health care-associated genotype (ST5); both carried a distinct, uncommon, composite SCCmec type. In summary, the BD GeneOhm MRSA assay had a high rate of detection of MRSA isolates harboring common and uncommon SCCmec types from the United States and Taiwan.

Antibiotic susceptibility patterns of Staphylococcus aureus isolates from Australian children

AIM

Staphylococcus aureus is an important cause of serious illness in children. Antibiotic resistance is an international problem and affects initial antibiotic choice. We aimed to describe susceptibility patterns of S. aureus isolates from Australian children to inform optimal empiric treatment of staphylococcal infections in this population.

METHODS

We analysed susceptibility data for all S. aureus isolates from children at Australian tertiary paediatric hospitals in 2006. Susceptibility rates were compared between hospitals and states, and with published studies of S. aureus isolates from Australian adults.

RESULTS

Overall, the proportion of methicillin-resistant S. aureus (MRSA) in Australian children was low (9.8%), and in each state it was less than for the comparable adult population. There were significant differences in susceptibility patterns between different states. Most MRSA isolates were susceptible to clindamycin (73%) and all isolates were reported as susceptible to vancomycin. Susceptibility patterns for isolates from bacteraemic patients were similar to those for isolates from all patients.

CONCLUSIONS

These data support current Australian recommendations for the use of flucloxacillin or a first-generation cephalosporin as initial treatment of non-life-threatening staphylococcal infections. However, broad spectrum antibiotic therapy including agents that are effective against MRSA should be considered for more serious infections. Appropriate specimens should be collected for susceptibility testing to enable directed treatment for MRSA and other resistant organisms. This study highlights the importance of using local, age-specific data in planning antibiotic treatment guidelines, as results vary substantially from city to city and between adults and children.

Community-associated methicillin-resistant Staphylococcus aureus: epidemiology and clinical consequences of an emerging epidemic

Staphylococcus aureus is an important cause of skin and soft-tissue infections (SSTIs), endovascular infections, pneumonia, septic arthritis, endocarditis, osteomyelitis, foreign-body infections, and sepsis. Methicillin-resistant S. aureus (MRSA) isolates were once confined largely to hospitals, other health care environments, and patients frequenting these facilities. Since the mid-1990s, however, there has been an explosion in the number of MRSA infections reported in populations lacking risk factors for exposure to the health care system. This increase in the incidence of MRSA infection has been associated with the recognition of new MRSA clones known as community-associated MRSA (CA-MRSA). CA-MRSA strains differ from the older, health care-associated MRSA strains; they infect a different group of patients, they cause different clinical syndromes, they differ in antimicrobial susceptibility patterns, they spread rapidly among healthy people in the community, and they frequently cause infections in health care environments as well. This review details what is known about the epidemiology of CA-MRSA strains and the clinical spectrum of infectious syndromes associated with them that ranges from a commensal state to severe, overwhelming infection. It also addresses the therapy of these infections and strategies for their prevention.

Epidemiology and susceptibilities of methicillin-resistant Staphylococcus aureus in Northeastern Ohio

A retrospective survey was performed on all staphylococcal infections diagnosed by the Ashtabula County Medical Center (Ashtabula, OH) during 2006 and 2007. Of the 1,612 Staphylococcus aureus isolates evaluated for their antibiotic resistances, 947 were methicillin-resistant S aureus (MRSA). In 2007, MRSA infections reached 589 cases per 100,000 inhabitants, a 77% increase compared with 2006. The increase in MRSA infections was noticeable among youth (6-25 years old), middle-aged people (45-50 years old), and elderly people (86-90 years old). MRSA infections increased among inpatients by 58%, among outpatients by 43%, and among nursing home residents by 183%. More than 66% of MRSA infections were found among healthy people in the community with no apparent risk factors. More than 88.7% of the infections belong to only 9 profiles of antibiotic resistance indiscriminately distributed among inpatients, outpatients, and nursing home residents. This report sheds further light on the rapid spread of MRSA across Northeastern Ohio, stressing the need for better education in preventive measures and infection control at the level of community and health care settings.

Community-associated methicillin-resistant Staphylococcus aureus: trends in case and isolate characteristics from six years of prospective surveillance

OBJECTIVES

In 2000, the Minnesota Department of Health (MDH) implemented active, sentinel site surveillance for community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA). Data from 2000-2005 were analyzed to determine trends in case characteristics, pulsed-field types (PFTs), and antimicrobial susceptibilities including inducible clindamycin resistance (ICR).

METHODS

Active sentinel site surveillance was initiated in 2000 at 12 hospital laboratories that served inpatients and outpatients. Patient medical records were reviewed to determine if they met the epidemiologic case criteria for CA-MRSA; isolates were obtained from patients meeting these criteria. The MDH Public Health Laboratory performed pulsed-field gel electrophoresis subtyping and antimicrobial susceptibility testing, including ICR.

RESULTS

The proportion of MRSA cases classified as CA increased from 11% to 33% (p<0.01). The proportion of cases with skin or soft tissue infections also increased compared with other infection types from 75% to 87% (p<0.01). During the surveillance period, USA300 replaced USA400 as the dominant PFT. With the change in dominant PFT, the proportion of isolates susceptible to erythromycin (45% to 13%, p<0.01) and ciprofloxacin (80% to 59%, p<0.01) decreased. The proportion of erythromycin-resistant/clindamycin-susceptible isolates with ICR (93% to 14%, p<0.01) decreased. The proportion of susceptible isolates also changed within the USA300 PFT; the proportion of isolates susceptible to erythromycin (33% vs. 3%) and the proportion susceptible to ciprofloxacin (67% to 62%) decreased significantly.

CONCLUSION

CA-MRSA increased dramatically from 2000 to 2005. Changes in the predominant PFT have impacted susceptibility profiles of CA-MRSA, including ICR. Continued surveillance is needed to monitor the changing epidemiology of CA-MRSA and to inform clinical decisions.

Community-associated Staphylococcus aureus infections and nasal carriage among children: molecular microbial data and clinical characteristics

An increasing number of infections caused by community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) carrying the Panton-Valentine leukocidin (PVL) genes was recently identified in Greece. In the present study, 170 patients with S. aureus infections and 123 uninfected children (<15 years old) who had been tested for nasal carriage were evaluated during a 2-year period. The MecA, PVL and superantigen family genes, and MRSA clones, were investigated by molecular methods. Sites of infection and laboratory findings for patients were recorded. The results were compared and statistically analysed. Among 123 uninfected children 73 (59%) carried S. aureus, including four MRSA strains. Of these, three MRSA and three methicillin-sensitive S. aureus (MSSA) strains were PVL-positive (p <0.0001). Ninety-six patients (96/170) exhibited skin and soft-tissue infections (SSTIs), and 74 exhibited invasive infections. The incidence of staphylococcal infections increased during July to September each year. In total, 110 S. aureus isolates were PVL-positive (81 from SSTIs and 29 from invasive infections, p <0.0001). Ninety-nine out of 106 MRSA (93%) isolates from 170 patients carried the PVL genes (p <0.0001); 97 belonged to the clonal complex CC80. Leukocyte and polymorphonuclear cell counts were higher among children with MRSA infections (p <0.005). MSSA predominated among patients with invasive infections (43/74), and carried mainly genes of the superantigen family. Children <5 years of age showed a higher risk of MRSA infection. The present study demonstrates that infections due to PVL-positive CA-MRSA spread easily among children, and SSTIs can lead to invasive infections. Nasal colonization may be an additional factor contributing to the emergence of CA-MRSA.

Identification and control of an outbreak of ciprofloxacin-susceptible EMRSA-15 on a neonatal unit

We report the identification and control of an outbreak of a ciprofloxacin-susceptible strain of UK epidemic meticillin-resistant Staphylococcus aureus (EMRSA)-15 on a neonatal unit (NNU). All babies were screened for MRSA on admission using ciprofloxacin-containing media which did not detect the outbreak strain. The first identified case was a premature baby who developed MRSA bacteraemia with associated tibial osteomyelitis and multiple subcutaneous abscesses. The outbreak strain was subsequently identified in the nasopharyngeal secretions of a second child who was not clinically infected. Screening of all patients on the NNU using non-ciprofloxacin-media identified two other colonised babies. All four patient isolates were EMRSA-15, spa type t022, SCCmec IV, Panton-Valentine leucocidin (PVL) negative, indistinguishable by pulsed-field gel electrophoresis and susceptible to all non-beta-lactam antimicrobials tested. The outbreak strain was cultured from four of 48 environmental sites in a communal milk-expressing room. Unsupervised movement of mothers to and from the milk-expressing room may have contributed to the outbreak. Control measures included cohort isolation of affected babies, improved environmental cleaning, increased emphasis on hand hygiene and education of mothers. Ciprofloxacin-containing media should be used with caution for MRSA screening in settings where ciprofloxacin-susceptible strains (including community-associated MRSA) are increasing in prevalence.

Pediatric community-acquired methicillin-resistant Staphylococcus aureus infection and colonization: trends and management

PURPOSE OF REVIEW

The scourge of community-acquired methicillin-resistant Staphylococcus aureus in pediatrics continues unabated. This review provides information on changes in epidemiology, therapeutic considerations, and measures to control the epidemic.

RECENT FINDINGS

The epidemiology and clinical manifestations of methicillin-resistant S. aureus have undergone important changes that pose challenges in recognition, diagnosis, and treatment for the pediatrician. Community-acquired methicillin-resistant S. aureus used to be predominantly associated with localized disease among previously healthy children; however, there are recent reports of more invasive and severe diseases with some fatalities. The antibiotic susceptibility pattern is also changing with some community-acquired methicillin-resistant S. aureus having resistance patterns indistinguishable from that of hospital-acquired methicillin-resistant S. aureus. Thus the choice of antibiotics is becoming even more challenging in pediatrics, with an already-limited armamentarium of antibiotics. The management of common skin diseases such as furunculosis and boils now requires close collaboration between the general pediatrician and the infectious diseases specialist.

SUMMARY

As the burden of community-acquired methicillin-resistant S. aureus disease continues to increase, pediatricians must have a high index of suspicion and must institute appropriate antimicrobial therapy based on community or regional antibiotic susceptibility of community-acquired methicillin-resistant S. aureus. There is an urgent need for effective infection control programs, including active surveillance components, to help curb the epidemic.

Emerging Options for Treatment of Invasive, Multidrug-ResistantStaphylococcus aureusInfections

Limited established treatment options exist for the treatment of serious, invasive infections caused by multidrug-resistant Staphylococcus aureus, most notably nosocomially acquired methicillin-resistant S. aureus (MRSA). Although vancomycin represents the gold standard for therapy of such invasive infections, reports of increasing in vitro resistance to vancomycin, combined with reports of clinical failures (with this and other antistaphylococcal agents), underscore the need for alternative therapies. Older agents with favorable in vitro activity available in both oral and intravenous dose forms include trimethoprim-sulfamethoxazole and clindamycin. Limited clinical data exist to support their routine use as initial therapy in the treatment of invasive disease. However, these and other options (e.g., tetracyclines) are being reexplored in the setting of increasing concern over MRSA acquired in the community setting. Newer treatment options for MRSA include linezolid, quinupristin-dalfopristin, daptomycin, and tigecycline. With the exception of linezolid, these newer agents require intravenous administration. Combination therapy may be considered in select invasive diseases refractory to standard monotherapies. These diseases include infections such as endocarditis, meningitis, and prosthetic device infections. Additional alternatives to vancomycin are under clinical investigation. Those in later stages of development include oritavancin, dalbavancin, telavancin, and ceftobiprole.