Clindamycin treatment of methicillin-resistant Staphylococcus aureus infections in children

Antibiotic Strategies for Severe Community-Acquired Pneumonia

Despite advancements in health systems and intensive care unit (ICU) care, along with the introduction of novel antibiotics and microbiologic techniques, mortality rates in severe community-acquired pneumonia (sCAP) patients have not shown significant improvement. Delayed admission to the ICU is a major risk factor for higher mortality. Apart from choosing the appropriate site of care, prompt and appropriate antibiotic therapy significantly affects the prognosis of sCAP. Treatment regimens involving ceftaroline or ceftobiprole are currently considered the best options for managing patients with sCAP. Additionally, several other molecules, such as delafloxacin, lefamulin, and omadacycline, hold promise as therapeutic strategies for sCAP. This review aims to provide a comprehensive summary of the key challenges in managing adults with severe CAP, focusing on essential aspects related to antibiotic treatment and investigating potential strategies to enhance clinical outcomes in sCAP patients.

Culture-directed antibiotics in peritoneal dialysis solutions: a systematic review focused on stability and compatibility

BACKGROUND

This systematic review summarises the stability of less commonly prescribed antibiotics in different peritoneal dialysis solutions that could be used for culture-directed therapy of peritonitis, which would be especially useful in regions with a high prevalence of multidrug antibiotic-resistant strains.

METHODS

A literature search of Medline, Scopus, Embase and Google Scholar for articles published from inception to 25 January, 2023 was conducted. Only antibiotic stability studies conducted in vitro and not recently reviewed by So et al. were included. The main outcomes were chemical, physical, antimicrobial and microbial stability. This protocol was registered in PROSPERO (registration number CRD42023393366).

RESULTS

We screened 1254 abstracts, and 28 articles were included in the study. In addition to those discussed in a recent systematic review (So et al., Clin Kidney J 15(6):1071-1078, 2022), we identified 18 antimicrobial agents. Of these, 9 have intraperitoneal dosing recommendations in the recent International Society for Peritoneal Dialysis (ISPD) peritonitis guidelines, and 7 of the 9 had stability data applicable to clinical practice. They were cefotaxime, ceftriaxone, daptomycin, ofloxacin, and teicoplanin in glucose-based solutions, tobramycin in Extraneal solution only and fosfomycin in Extraneal, Nutrineal, Physioneal 1.36% and 2.27% glucose solutions.

CONCLUSIONS

Physicochemical stability has not been demonstrated for all antibiotics with intraperitoneal dosing recommendations in the ISPD peritonitis guidelines. Further studies are required to determine the stability of antibiotics, especially in icodextrin-based and low-glucose degradation products, pH-neutral solutions.

Antibacterial activity of recently approved antibiotics against methicillin-resistant Staphylococcus aureus (MRSA) strains: A systematic review and meta-analysis

Background

Methicillin-resistant Staphylococcus aureus (MRSA) infections are considered an important public health problem, and treatment options are limited. Accordingly, in this meta-analysis, we analyzed published studies to survey in vitro activity of recently approved antibiotics against MRSA isolates.

Methods

We searched electronic databases; PubMed, Scopus, and Web of Science to identify relevant studies (until November 30, 2020) that have focused on the in vitro activity of telavancin, dalbavancin, oritavancin, and tedizolid against MRSA isolates. Statistical analyses were conducted using STATA software (version 14.0).

Results

Thirty-eight studies were included in this meta-analysis. Overall in vitro activity of tedizolid on 12,204 MRSA isolates was 0.250 and 0.5 µg/mL for MIC₅₀ and MIC₉₀, (minimum inhibitory concentration at which 50% and 90% of isolates were inhibited, respectively), respectively. The overall antibacterial activity of dalbavancin on 28539 MRSA isolates was 0.060 and 0.120 µg/mL for MIC₅₀ and MIC₉₀, respectively. The overall antibacterial activity of oritavancin on 420 MRSA isolates was 0.045 and 0.120 µg/mL for MIC₅₀ and MIC₉₀, respectively. The overall antibacterial activity of telavancin on 7353 MRSA isolates was 0.032 and 0.060 µg/mL for MIC₅₀ and MIC₉₀, respectively. The pooled prevalence of tedizolid, telavancin, and dalbavancin susceptibility was 100% (95% CI: 100–100).

Conclusion

Telavancin, dalbavancin, oritavancin, and tedizolid had potent in vitro activity against MRSA isolates. The low MICs and high susceptibility rates of these antibiotics recommend a hopeful direction to introduce useful antibiotics in treating MRSA infections in the future.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12941-022-00529-z.

Oral Is the New IV. Challenging Decades of Blood and Bone Infection Dogma: A Systematic Review

BACKGROUND

We sought to determine if controlled, prospective clinical data validate the long-standing belief that intravenous (IV) antibiotic therapy is required for the full duration of treatment for 3 invasive bacterial infections: osteomyelitis, bacteremia, and infective endocarditis.

METHODS

We performed a systematic review of published, prospective, controlled trials that compared IV-only to oral stepdown regimens in the treatment of these diseases. Using the PubMed database, we identified 7 relevant randomized controlled trials (RCTs) of osteomyelitis, 9 of bacteremia, 1 including both osteomyelitis and bacteremia, and 3 of endocarditis, as well as one quasi-experimental endocarditis study. Study results were synthesized via forest plots and funnel charts (for risk of study bias), using RevMan 5.4.1 and Meta-Essentials freeware, respectively.

RESULTS

The 21 studies demonstrated either no difference in clinical efficacy, or superiority of oral versus IV-only antimicrobial therapy, including for mortality; in no study was IV-only treatment superior in efficacy. The frequency of catheter-related adverse events and duration of inpatient hospitalization were both greater in IV-only groups.

DISCUSSION

Numerous prospective, controlled investigations demonstrate that oral antibiotics are at least as effective, safer, and lead to shorter hospitalizations than IV-only therapy; no contrary data were identified. Treatment guidelines should be modified to indicate that oral therapy is appropriate for reasonably selected patients with osteomyelitis, bacteremia, and endocarditis.

Mechanisms of Resistance to Macrolide Antibiotics among Staphylococcus aureus

Methicillin resistant Staphylococcus aureus strains pose a serious treatment problem because of their multi-drug resistance (MDR). In staphylococcal strains, resistance to macrolides, lincosamides, and streptogramin B (MLS_B) correlates with resistance to methicillin. The rapid transmission of erm genes responsible for MLS_B resistance has strongly limited the clinical application of traditional macrolides such as erythromycin. On the other hand, in the age of increasing insensitivity to antibiotics the idea of implementing a therapy based on older generation drugs brings hope that the spread of antibiotic resistance will be limited. A thorough understanding of the resistance mechanisms contributes to design of antibiotics that avoid bacterial insensitivity. This review highlights the mechanisms of action of macrolides and mechanism of resistance to these antibiotics among Staphylococcus aureus.

Clinical Practice Guideline by the Pediatric Infectious Diseases Society and the Infectious Diseases Society of America: 2021 Guideline on Diagnosis and Management of Acute Hematogenous Osteomyelitis in Pediatrics

This clinical practice guideline for the diagnosis and treatment of acute hematogenous osteomyelitis (AHO) in children was developed by a multidisciplinary panel representing Pediatric Infectious Diseases Society (PIDS) and the Infectious Diseases Society of America (IDSA). This guideline is intended for use by healthcare professionals who care for children with AHO, including specialists in pediatric infectious diseases, orthopedics, emergency care physicians, hospitalists, and any clinicians and healthcare providers caring for these patients. The panel's recommendations for the diagnosis and treatment of AHO are based upon evidence derived from topic-specific systematic literature reviews. Summarized below are the recommendations for the diagnosis and treatment of AHO in children. The panel followed a systematic process used in the development of other IDSA and PIDS clinical practice guidelines, which included a standardized methodology for rating the certainty of the evidence and strength of recommendation using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) approach. A detailed description of background, methods, evidence summary and rationale that support each recommendation, and knowledge gaps can be found online in the full text.

Correlation of MRSA polymerase chain reaction (PCR) wound swab testing and wound cultures in skin and soft tissue infections

Methicillin-resistant Staphylococcus aureus is a considerable pathogen in the setting of skin and soft tissue infections (SSTIs). MRSA PCR swab testing is widely used in the setting of respiratory tract infections, however little data exists relating to the use of MRSA PCR swab testing in SSTIs. Three thousand, nine hundred and ninety-five patients were included in this retrospective study that aimed to validate the clinical correlation of MRSA PCR wound swab testing in SSTIs through sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) analysis. From this review, MRSA PCR wound swabs were found to have a sensitivity of 97.6% (97.5-98.5), a specificity of 94.9% (94.3-95.7), a PPV of 92.3% (91.4-93.2), and a NPV of 98.4% (98.0-98.8). The study results demonstrate that the MRSA SSTI PCR assays have a high NPV and the potential to be a vital tool in de-escalating antimicrobial therapy associated with SSTIs.

Antimicrobial action of autologous platelet-rich plasma on MRSA-infected skin wounds in dogs

Effective antimicrobial preparations, other than antibiotics, are important for the treatment of potentially fatal drug-resistant infections. Methicillin-resistant Staphylococcus aureus (MRSA) is one of the leading causes of hospital-acquired and post- operative infections. Fortunately, the antimicrobial properties of platelet-rich plasma (PRP) against various microorganisms enable its potential use as an alternative to conventional antibiotics. The present work was designed to evaluate the hypothesized antimicrobial activity of PRP against MRSA infected skin wounds. Six adult male dogs were divided equally into control and PRP groups. Unilateral circular full-thickness skin wounds were created then a MRSA suspension was injected locally. Treatment started at 1st week post infection with subcutaneous infiltration of autologous activated PRP every week in the PRP group and with topical application of clindamycin cream twice daily in the control group. PRP decreased wound size and significantly increased wound contractility and re-epithelization, as confirmed by histopathological and immunohistochemical findings. Also PRP treated group showed significant decrease in ROS and redox imbalance with over expression of the TNF-α and VEGFA genes that indicate angiogenesis and maximum antibacterial activity after three weeks. In conclusion, CaCl₂-activated PRP exhibited antimicrobial activity against MRSA infection, which improved the infected wound healing re-epithelization and granulation tissue formation.

What Is the Evidence for Co-trimoxazole, Clindamycin, Doxycycline, and Minocycline in the Treatment of Methicillin-Resistant Staphylococcus aureus (MRSA) Pneumonia?

Objective: To review the evidence for trimethoprim-sulfamethoxazole (TMP-SMX), clindamycin, doxycycline, and minocycline in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) pneumonia. Data Source: MEDLINE, PubMed, EMBASE, Google, Google Scholar, Cochrane Central Register of Controlled Trials from 1946 to May 20, 2019. The search was performed with the keywords methicillin-resistant Staphylococcus aureus, MRSA, Staphylococcus aureus, pneumonia, trimethoprim, sulfamethoxazole drug combination, trimethoprim, sulfamethoxazole, TMP-SMX, co-trimoxazole, clindamycin, doxycycline, and minocycline. Data Extraction: Studies reporting the use of the above antibiotics for MRSA pneumonia treatment with clinical outcomes were included. Search parameters were limited to English language and human studies only. Data Synthesis: The search yielded 16 relevant articles: 6 TMP-SMX, 8 clindamycin, zero doxycycline, and 2 minocycline. For TMP-SMX, prospective randomized trials showed variable results; however, these studies were not specifically designed to assess MRSA pneumonia treatment. Retrospective studies with clindamycin suggested that it could be used as monotherapy or in combination with other anti-MRSA antibiotics. There was no evidence for doxycycline use, but 2 small retrospective reviews appeared to support minocycline as a treatment option. Relevance to Patient Care and Clinical Practice: These antibiotics are often used in clinical practice as potential treatment options for MRSA pneumonia. This article reviews the evidence for the clinical efficacy and safety of these agents. Conclusions: There are limited data to support use of TMP-SMX, clindamycin, doxycycline, or minocycline in MRSA pneumonia treatment. Randomized controlled trials are required to determine the effectiveness of these antibiotics. Clinicians should base their decision to use these agents on a case-by-case basis depending on clinical status and susceptibility results.

Determination of antimicrobial susceptibility patterns in Staphylococcus aureus strains recovered from patients at two main health facilities in Kabul, Afghanistan

Background

Staphylococcus aureus (S. aureus) is a major pathogen implicated in skin and soft tissue infections, abscess in deep organs, toxin mediated diseases, respiratory tract infections, urinary tract infections, post-surgical wound infections, meningitis and many other diseases. Irresponsible and over use of antibiotics has led to an increased presence of multidrug resistant organisms and especially methicillin resistant Staphylococcus aureus (MRSA) as a major public health concern in Afghanistan. As a result, there are many infections with many of them undiagnosed or improperly diagnosed. We aimed to establish a baseline of knowledge regarding the prevalence of MRSA in Kabul, Afghanistan, as well as S. aureus antimicrobial susceptibility to current available antimicrobials, while also determining those most effective to treat S. aureus infections.

Methods

Samples were collected from patients at two main Health facilities in Kabul between September 2016 and February 2017. Antibiotic susceptibility profiles were determined by the disc diffusion method and studied using standard CLSI protocols.

Results

Out of 105 strains of S. aureus isolated from pus, urine, tracheal secretions, and blood, almost half (46; 43.8%) were methicillin-sensitive Staphylococcus aureus (MSSA) while 59 (56.2%) were Methicillin-resistant Staphylococcus aureus (MRSA). All strains were susceptible to vancomycin. In total, 100 (95.2%) strains were susceptible to rifampicin, 96 (91.4%) susceptible to clindamycin, 94 (89.5%) susceptible to imipenem, 83 (79.0%) susceptible to gentamicin, 81(77.1%) susceptible to doxycycline, 77 (77.1%) susceptible to amoxicillin + clavulanic acid, 78 (74.3%) susceptible to cefazolin, 71 (67.6%) susceptible to tobramycin, 68 (64.8%) susceptible to chloramphenicol, 60 (57.1%) were susceptible to trimethoprim-sulfamethoxazole, 47 (44.8%) susceptible to ciprofloxacin, 38 (36.2%) susceptible to azithromycin and erythromycin, 37 (35.2%) susceptible to ceftriaxone and 11 (10.5%) were susceptible to cefixim. Almost all (104; 99.05%) were resistant to penicillin G and only 1 (0.95%) was intermediate to penicillin G. Interestingly, 74.6% of MRSA strains were azithromycin resistant with 8.5% of them clindamycin resistant. Ninety-six (91.4%) of the isolates were multi-drug resistant.

Conclusions

There was a high rate of Methicillin resistance (56.2%) among S. aureus strains in the samples collected and most (91.4%) were multidrug resistant. The most effective antibiotics to treat Staph infections were vancomycin, rifampicin, imipenem, clindamycin, amoxicillin-clavulanic acid, cefazolin, gentamicin and doxycycline. The least effective were azithromycin, ceftriaxone, cefixim and penicillin. We recommend that, where possible, in every case of S. aureus infection in Kabul, Afghanistan, Antibiotic susceptibility testing (AST) should be performed and responsible use of antibiotics should be considered.

Sequential Parenteral to Oral Clindamycin Dosing in Pediatric Musculoskeletal Infection: A Retrospective Review of 30 mg/kg/d Versus 40 mg/kg/d

BACKGROUND

Children with musculoskeletal infection in methicillin-resistant Staphylococcus aureus (MRSA) prevalent communities are often treated with oral clindamycin. Current guidelines recommend approximately 40 mg/kg/d for MRSA infections. This study investigates the clinical practice of using 30 mg/kg/d of clindamycin as an alternative for outpatient dosing.

METHODS

Children with musculoskeletal infection treated with outpatient clindamycin from 2009 to 2014 were studied by retrospective review. The amount of clindamycin administered was determined from dose, interval and duration of outpatient treatment. Hospital readmission, surgeries and sequelae were assessed. Severity of illness was determined for children with osteomyelitis. The readmission rate of 25 children treated with 40 mg/kg/d was compared with that of 190 children treated with 30 mg/kg/d. The reason for readmission was evaluated to consider whether antibiotic dosing strategy was a potential factor.

RESULTS

Among 215 children studied, the average outpatient duration of treatment was 32.8 days. There was no significant difference in the rate of readmission between dosing cohorts. Severity of illness scores (0-10 scale) was significantly higher among readmitted children with osteomyelitis (mean 9.8 ± 0.4) than among those with osteomyelitis who were not readmitted (mean 2.9 ± 3.2), P = 0.001. Sequelae were more common in the high-dose group and were noted in 3 children (12%) in that cohort compared with 6 children (3.2%) in the low-dose cohort (P > 0.05).

CONCLUSION

Oral dosing of 30 mg/kg/d was effective for musculoskeletal infection in children in an MRSA prevalent community. Illness severity appeared to have greater impact on readmission and sequelae than did antibiotic dosing.

Pharmacokinetics, Safety and Tolerability of Single Oral or Intravenous Administration of 200 mg Tedizolid Phosphate in Adolescents

BACKGROUND

Tedizolid is a novel oxazolidinone antibacterial US FDA approved for treatment of acute bacterial skin and skin structure infections in adults. This study assessed the pharmacokinetics, safety and tolerability of tedizolid phosphate in adolescents (12-17 years old) after administration of a single intravenous (IV) or oral dose.

METHODS

In this multicenter, open-label study, a single IV infusion (N = 10) or oral dose (N = 10) of 200 mg tedizolid phosphate was administered to adolescents already receiving antibacterial treatment for presumed or documented infection. Blood and urine samples were collected predose and over 24 hours.

RESULTS

Tedizolid pharmacokinetics was generally similar after IV or oral administration of 200 mg tedizolid phosphate. Mean (standard deviation) half-life values were similar for oral and IV routes, 8.3 (2.0) and 6.6 (0.7) hours, respectively. Absolute oral bioavailability of tedizolid (90% confidence interval) was 88.8% (70.4%-112.1%). Geometric mean ratio (90% confidence interval) of area under the concentration-time curve values for adolescents relative to values previously reported for adults after 200 mg of single-dose IV or oral administration were 0.847 (0.736-0.975). Tedizolid was well tolerated.

CONCLUSIONS

Overall pharmacokinetics of tedizolid was similar after administration of a single oral or IV 200 mg dose, and bioavailability was high. Exposure profiles were similar to those in adults. With clinical outcomes based on area under the concentration-time curve/minimum inhibitory concentration and current susceptibility of Gram-positive pathogens, results suggest that the 200 mg daily regimen of tedizolid phosphate can be extended to adolescents for clinical trials, and that dose adjustment may not be required when switching routes.

USA300 Methicillin-Resistant Staphylococcus aureus, United States, 2000-2013

We confirm USA300 in the West and Midwest and subsequent diffusion to the East Coast.

In the United States, methicillin-resistant Staphylococcus aureus (MRSA) with the USA300 pulsed-field gel electrophoresis type causes most community-associated MRSA infections and is an increasingly common cause of health care–associated MRSA infections. USA300 probably emerged during the early 1990s. To assess the spatiotemporal diffusion of USA300 MRSA and USA100 MRSA throughout the United States, we systematically reviewed 354 articles for data on 33,543 isolates, of which 8,092 were classified as USA300 and 2,595 as USA100. Using the biomedical literature as a proxy for USA300 prevalence among genotyped MRSA samples, we found that USA300 was isolated during 2000 in several states, including California, Texas, and midwestern states. The geographic mean center of USA300 MRSA then shifted eastward from 2000 to 2013. Analyzing genotyping studies enabled us to track the emergence of a new, successful MRSA type in space and time across the country.

Empirical therapy in Methicillin-resistant Staphylococcus Aureus infections: An Up-To-Date approach

Methicillin-resistant Staphylococcus aureus (MRSA) continues to be an important pathogen worldwide, with high prevalence of infection in both community and hospital settings. Timely and appropriate choice of empirical therapy in the setting of MRSA infection is imperative due to the high rate of associated morbidity and mortality with MRSA infections. Initial choices should be made based on the site and severity of the infection, most notably moderate skin and soft tissue infections which may be treated with oral antibiotics (trimethoprim-sulfamethoxazole, clindamycin, doxycycline/minocycline, linezolid) in the outpatient setting, versus choice of parenteral therapy in the inpatient setting of more invasive or severe disease. Though the current recommendations continue to strongly rely on vancomycin as a standard empiric choice in the setting of severe/invasive infections, alternative therapies exist with studies supporting their non-inferiority. This includes the use of linezolid in pneumonia and severe skin and skin structure infections (SSSI) and daptomycin for MRSA bacteremia, endocarditis, SSSIs and bone/joint infections. Additionally, concerns continue to arise in regards to vancomycin, such as increasing isolate MICs, and relatively high rates of clinical failures with vancomycin. Thus, the growing interest in vanomycin alternatives, such as ceftaroline, ceftobribole, dalbavancin, oritavancin, and tedizolid, and their potential role in treating MRSA infections.

Development and physicochemical characterization of clindamycin resinate for taste masking in pediatrics

PURPOSE

To evaluate the physicochemical characteristics of clindamycin HCl in a complex form (resinate) with ion exchange resin (IER) (Amberlite IRP69).

METHODS

Drug-resin complex was prepared by simple aqueous binding method. Drug binding study was carried out at different drug and resin concentrations. Several physicochemical characterization studies were conducted to evaluate the resinate complex. These studies included flow properties, in vitro drug release in SGF and SIF, DSC, TGA, mass spectroscopy and XPRD evaluations. In addition, stability study of resinate complex was conducted at 25 and 40 °C for up to 1 month.

RESULTS

Clindamycin and Amberlite IRP69 have formed a complex (resinate) and have shown good flow properties, good thermal properties and chemical stability (short term over 4 weeks) at 25 and 40 °C. Clindamycin release profiles from resinate in SGF and SIF have shown immediate release characteristics and release in simulated saliva has shown dependence on water volume.

CONCLUSION

The clindamycin stable complex with IER (Amberlite IRP69) has the potential for further development as a compatible pediatric liquid formulation (suspension) or a fast disintegrating tablet.

Multiple-locus VNTR Analyses of Methicillin-resistant Staphylococcus aureus from Jamaica

BACKGROUND

This study assessed the antimicrobial susceptibilities and the presence of inducible macrolide–lincosamide–streptogramin B (iMLSB) resistance in methicillin-resistant Staphylococcus aureus (MRSA) of Jamaica as well as the relatedness using polymerase chain reaction-based staphylococcal cassette chromosome mec (SCCmec) and multiple-locus variable numbers of tandem repeat analyses (MLVAs).

MATERIALS AND METHODS

Antimicrobial susceptibility, the presence of MLS_B resistance, and SCCmec and MLVA patterns were assessed for 61 nonduplicate isolates of MRSA from hospitalized patients.

RESULTS

While no isolate was resistant to vancomycin, 53 (86.9%) isolates were resistant to ciprofloxacin, 52 (85.3%) to erythromycin, 49 (80%) to lincomycin, and 45 (74%) to clindamycin. Of the 52 erythromycin-resistant isolates, 48% exhibited constitutive resistance and 8% showed inducible MLS_B (iMLS_B) resistance. Most (85%) of typable isolates were SCCmec type IV, and among these, 16 MLVA patterns were identified.

CONCLUSION

Multidrug resistance continues to characterize MRSA. Among the erythromycin-resistant isolates, constitutive resistance and iMLS_B resistance are common. These facts will complicate the treatment of MRSA infections and warrant continued surveillance and judicial use of antimicrobial agents.

Evaluation of the automated Vitek 2 system for detection of various mechanisms of macrolide and lincosamide resistance in Staphylococcus aureus

We evaluated the performance of the automated Vitek 2 system against disk diffusion for susceptibility testing of Staphylococcus aureus strains showing various resistance mechanisms to macrolides and lincosamides (ML). The Vitek 2 system showed 100% concordance with the D-zone test in detection of the most common resistance mechanisms to ML, including methylase and efflux systems.

Incidence of constitutive and inducible clindamycin resistance among hospital-associated Staphylococcus aureus

Clindamycin is one of the important alternative antibiotics in the therapy of Staphylococcus aureus infections. Clinical failure of clindamycin therapy has been reported due to multiple mechanisms that confer resistance to macrolides, lincosamides and Streptogramin B (MLSB) antibiotics. In vitro routine tests for clindamycin susceptibility may fail to detect inducible clindamycin resistance due to erm genes, resulting in the treatment failure. Although data from the developed countries have shown to be enormity of the problem, data from the developing countries are lacking. The aim of the study was to distinguish different resistance phenotypes in erythromycin-resistant S. aureus by a simple double-disc diffusion test (D test). A total of 153 S. aureus isolates were subjected to routine antibiotic susceptibility testing, including cefoxitin disc (30 μg) and by oxacillin screen agar. Inducible clindamycin resistance was tested by 'D test' as per CLSI guidelines. Odds ratios (OR) and 95 % confidence intervals (95 % CI) were calculated. P values were calculated using SPSS (version 18). Among 153 S. aureus isolates, 42 (27.45 %) were resistant to methicillin, whereas 111 (72.54 %) were methicillin susceptible. Out of the 63 (41.17 %) erythromycin-resistant S. aureus isolates, 14 (9.15 %) showed inducible resistance [P = 0.0002, odds ratio (OR) 18.30; 95 % confidence interval (CI) 8.72-25.77), 20 (13.07 %)] showed constitutive resistance (P = 0.002, OR 14.38, 95 % CI 5.33-21.49), while the remaining 29 (18.95 %) showed inducible phenotype. Inducible and constitutive resistance was found to be higher in MSSA when compared with MRSA. Clinical laboratories should perform D test routinely to guide the clinicians about the inducible clindamycin resistance and to prevent misuse of antibiotics.

Epidemiology and treatment of community-associated methicillin-resistantStaphylococcus aureusin children

Similar to the epidemiology of methicillin-sensitive Staphylococcus aureus, community-associated methicillin-resistant S. aureus infections occur in children in different regions of the USA and throughout the world. Although minor skin and soft-tissue infections predominate, life-threatening invasive disease and death can result. The novel genetic elements, staphylococcal cassette chromosome mec IV and V, explain the narrow antibiotic resistance pattern, and suggest the mechanism of spread among staphylococci. Panton-Valentine leukocidin apparently plays a role in its pathogenesis. Clindamycin therapy is often effective for treatment, but inducible resistance can develop if the isolate exhibits macrolide resistance due to the erm mechanism. Other drugs displaying in vitro activity against community-associated methicillin-resistant S. aureus include trimethoprim-sulfamethoxazole, tetracyclines, quinolones, linezolid and vancomycin. While experience in pediatric patients is limited, daptomycin, ketolides, glycylcyclines, newer glycopeptides and beta-lactamase-stable cephalosporins may be useful in the future. Further research could include well-designed studies of mechanisms of virulence, continued surveillance of changes in pathogenicity and susceptibility, as well as treatment effectiveness.

Performance of Vitek 2 for antimicrobial susceptibility testing of Staphylococcus spp. and Enterococcus spp

Vitek 2 (bioMérieux, Inc., Durham, NC) is a widely used commercial antimicrobial susceptibility testing system. We compared MIC results obtained by Vitek 2 to those obtained by the Clinical and Laboratory Standards Institute (CLSI) broth microdilution (BMD) reference method for 134 staphylococcal and 84 enterococcal clinical isolates. Nineteen agents were evaluated, including all those available on Vitek 2 for testing staphylococci and enterococci. The resistance phenotypes tested included methicillin-resistant Staphylococcus aureus (MRSA) (n = 58), S. aureus with inducible clindamycin resistance (ICR) (n = 30), trimethoprim-sulfamethoxazole-resistant MRSA (n = 10), vancomycin-resistant Enterococcus (n = 37), high-level gentamicin-resistant Enterococcus (n = 15), linezolid-resistant Enterococcus (n = 5), and daptomycin-nonsusceptible Enterococcus faecalis (n = 6). For the staphylococci, there was 98.9% categorical agreement (CA). There was one very major error (VME) for gentamicin in a Staphylococcus hominis isolate, six VMEs for inducible clindamycin in S. aureus isolates, and two major errors (ME) for daptomycin in an S. aureus and a Staphylococcus epidermidis isolate. For enterococci, there was 97.3% CA. Two VMEs were observed for daptomycin in isolates of E. faecalis and 2 ME, 1 for high-level gentamicin resistance and 1 for nitrofurantoin, in E. faecium isolates. Overall, there was 98.3% CA and 99% essential agreement for the testing of staphylococci and enterococci by the Vitek 2. With the exception of detecting ICR in S. aureus, Vitek 2 performed reliably for antimicrobial susceptibility testing of staphylococci and enterococci.

Skin and soft tissue infections

The approach to common skin and soft tissue infections (SSTIs) was previously well understood. However, the recent emergence of community-associated methicillin resistant Staphyloccocus aureus as a common pathogen has changed the epidemiology of these infections and has led clinicians to alter their practice and treatment of SSTI. This article discusses the present epidemiology of SSTI and community-acquired methicillin-resistant Staphylococcus aureus, evidence-based approach to incision and drainage, the utility of adjuvant antibiotic therapy after abscess drainage, and current antimicrobial approach to cellulitis and nondrained SSTIs. Methods to reduce transmission and recurrence of SSTI through decolonization strategies are also discussed.

Community-acquired disseminated methicillin-resistantStaphylococcus aureusinfection: case report and clinical implications

A 6-year-old girl with community-acquired disseminated infection caused by methicillin-resistant Staphylococcus aureus (MRSA) is described. She had sepsis, meningo-encephalitis, pyomyositis, osteomyelitis, pericarditis and pulmonary embolisation caused by a multi-resistant strain of MRSA. Vancomycin is not routinely recommended as the first-line antimicrobial agent for suspected Staphylococcus aureus infection; however, it should be considered pending susceptibility results in patients presenting with severe sepsis in areas where the prevalence of MRSA is high.

Improved understanding of factors driving methicillin-resistant Staphylococcus aureus epidemic waves

Methicillin-resistant Staphylococcus aureus (MRSA) remains one of the most important causes of nosocomial infections worldwide. Since the global spread of MRSA in the 1960s, MRSA strains have evolved with increased pathogenic potential. Notably, some strains are now capable of causing persistent infections not only in hospitalized patients but also in healthy individuals in the community. Furthermore, MRSA is increasingly associated with infections among livestock-associated workers, primarily because of transmission from animals to humans. Moreover, many MRSA strains have gained resistance to most available antibiotics. In this review, we will present current knowledge on MRSA epidemiology and discuss new endeavors being undertaken to understand better the molecular and epidemiological underpinnings of MRSA outbreaks.

The impact of evidence-based clinical practice guidelines applied by a multidisciplinary team for the care of children with osteomyelitis

BACKGROUND

Care of children with osteomyelitis requires multidisciplinary collaboration. This study evaluates the impact of evidence-based guidelines for the treatment of pediatric osteomyelitis when utilized by a multidisciplinary team.

METHODS

Guidelines for pediatric osteomyelitis were developed and were implemented by a multidisciplinary team comprised of individuals from several hospital services, including orthopaedics, pediatrics, infectious disease, nursing, and social work, who met daily to conduct rounds and make treatment decisions. With use of retrospective review and statistical analysis, we compared children with osteomyelitis who had been managed at our institution from 2002 to 2004 (prior to the implementation of the guidelines), referred to as Group I in this study, with those who were managed in 2009 according to the guidelines, referred to as Group II.

RESULTS

Two hundred and ten children in Group I were compared with sixty-one children in Group II. No significant differences between the two cohorts were noted for age, sex, incidence of methicillin-resistant Staphylococcus aureus infection (18.1% in Group I compared with 26.2% in Group II), incidence of methicillin-sensitive Staphylococcus aureus infection (23.8% in Group I compared with 27.9% in Group II), bacteremia, or surgical procedures. Significant differences (p < 0.05) between cohorts were noted for each of the following: the delay in magnetic resonance imaging after admission (2.5 days in Group I compared with one day in Group II), the percentage of patients who had received clindamycin as the initial antibiotic (12.9% in Group I compared with 85.2% in Group II), the percentage of patients who had had a blood culture before antibiotic administration (79.5% in Group I compared with 91.8% in Group II), the percentage of patients who had had a culture of tissue from the infection site (62.9% in Group I compared with 78.7% in Group II), the percentage of patients in whom the infecting organism was identified on tissue or blood culture (60.0% in Group I compared with 73.8% in Group II), the number of antibiotic changes (2.0 changes in Group I compared with 1.4 changes in Group II), and the mean duration of oral antibiotic use (27.7 days in Group I compared with 43.7 days in Group II). When compared with Group I, Group II had clinically important trends of a shorter total length of hospital stay (12.8 days in Group I compared with 9.7 days in Group II; p = 0.054) and a lower hospital readmission rate (11.4% in Group I compared with 6.6% in Group II; p = 0.34).

CONCLUSIONS

Evidence-based treatment guidelines applied by a multidisciplinary team resulted in a more efficient diagnostic workup, a higher rate of identifying the causative organism, and improved adherence to initial antibiotic recommendations with fewer antibiotic changes during treatment. Additionally, there were trends toward lower hospital readmission rates and a shorter length of hospitalization.

MRSA USA300 at Alaska Native Medical Center, Anchorage, Alaska, USA, 2000-2006

To determine whether methicillin-resistant Staphylococcus aureus (MRSA) USA300 commonly caused infections among Alaska Natives, we examined clinical MRSA isolates from the Alaska Native Medical Center, Anchorage, during 2000–2006. Among Anchorage-region residents, USA300 was a minor constituent among MRSA isolates in 2000–2003 (11/68, 16%); by 2006, USA300 was the exclusive genotype identified (10/10).

Systemic antibiotic therapy for chronic osteomyelitis in adults

The standard recommendation for treating chronic osteomyelitis is 6 weeks of parenteral antibiotic therapy. However, oral antibiotics are available that achieve adequate levels in bone, and there are now more published studies of oral than parenteral antibiotic therapy for patients with chronic osteomyelitis. Oral and parenteral therapies achieve similar cure rates; however, oral therapy avoids risks associated with intravenous catheters and is generally less expensive, making it a reasonable choice for osteomyelitis caused by susceptible organisms. Addition of adjunctive rifampin to other antibiotics may improve cure rates. The optimal duration of therapy for chronic osteomyelitis remains uncertain. There is no evidence that antibiotic therapy for >4-6 weeks improves outcomes compared with shorter regimens. In view of concerns about encouraging antibiotic resistance to unnecessarily prolonged treatment, defining the optimal route and duration of antibiotic therapy and the role of surgical debridement in treating chronic osteomyelitis are important, unmet needs.

Molecular characterization of methicillin-resistant Staphylococcus aureus obtained from the anterior nares of healthy Korean children attending daycare centers

OBJECTIVES

This study was performed to investigate the molecular characterization of methicillin-resistant Staphylococcus aureus (MRSA) isolated from the anterior nares of Korean children attending daycare centers.

METHODS

During September and October 2008, a survey of nasal carriage of MRSA was conducted among healthy children who were attending daycare centers in Seoul, Korea. Nasal swab samples were cultured to isolate S. aureus, and antimicrobial susceptibility was assessed using a disk diffusion test. All MRSA isolates were archived for subsequent molecular tests, including multilocus sequence typing, Panton-Valentine leukocidin (PVL) genes polymerase chain reaction (PCR), and staphylococcal cassette chromosome mec (SCCmec) typing.

RESULTS

Among 428 preschool-aged children enrolled, 9.3% (40/428) were colonized with MRSA. Among the 40 MRSA isolates, antibiotic susceptibilities to clindamycin and erythromycin were 97.5% (39/40) and 45% (18/40), respectively. All of the 21 strains susceptible to clindamycin and resistant to erythromycin had MLS(B)-inducible phenotypes. Sequence type (ST) 72-SCCmec type IV was the predominant clone (n=23; 57.5%), followed by ST72-SCCmec type II (n=6; 15%), ST1765-SCCmec type IV (n=4; 10%), ST1765-SCCmec type II (n=2; 5%), and ST1-SCCmec type IV (n=2; 5%). No clone was positive for PVL genes.

CONCLUSIONS

ST72 strains, which were previously found in hospital-associated MRSA, are now widely distributed in healthy Korean children. In addition, the prevalence of inducible resistance of clindamycin should be considered when selecting empirical antibiotics for community-associated MRSA infections in Korea.

Adherence to CLSI recommendations for testing of Staphylococcus aureus isolates in Louisiana hospitals: report of a clinical failure and results of a questionnaire study

We report a case of failure of clindamycin therapy due to inducible clindamycin resistance. We surveyed and found that only 52% of reporting hospitals in the state of Louisiana were performing the D test for inducible clindamycin resistance according to guidelines recommended by the Clinical and Laboratory Standards Institute (formerly the National Committee for Clinical Laboratory Standards).

Phenotypic and genotypic study of macrolide, lincosamide and streptogramin B (MLSB) resistance in clinical isolates of Staphylococcus aureus in Tehran, Iran

Background

Resistance to antimicrobial agents among Staphylococcus aureus is an increasing problem. Two common genes responsible for resistance to macrolide, lincosamide and streptogramin B (MLS_B) antibiotics are the ermA and ermC genes. Three resistance phenotypes have been detected to these antibiotics: strains containing cMLS_B (constitutive MLS_B) and iMLS_B (inducible MLS_B), which are resistant to macrolide, lincosamide and streptogramin B antibiotics, and MS, which is only resistant to macrolide and streptogramin B antibiotics. The aim of this study was to determine the prevalence of MLS_B phenotypes and genotypes in erythromycin-resistant strains of S. aureus isolated from patients in 4 university hospitals in Tehran, Iran.

Material/Methods

S. aureus strains were isolated from various clinical specimens and identified by routine phenotypic methods and PCR for nuc gene. Erythromycin resistance was determined by disk diffusion testing. Prevalence of MLS_B phenotypes was determined by use of the D-test. ermA and ermC genes were detected by PCR.

Results

Altogether, 126 erythromycin-resistant strains of S. aureus were detected. Prevalence of cMLS_B, iMLS_B and MS resistance phenotypes were 92.8%, 6.4%, and 0.8%, respectively; 60.3% of strains had ermA gene and 54.8% ermC gene; 61 strains (48.4%) contained 2 studied erm genes and 42 strains (33.3%) did not have any studied erm genes.

Conclusions

Due to the high prevalence of clindamycin resistance among S. aureus isolated from patients in Iran, we recommend clindamycin therapy only after proper antimicrobial susceptibility testing.

Retrospective cohort study of hospitalized adults treated with vancomycin or clindamycin for methicillin-resistant Staphylococcus aureus skin infections

BACKGROUND

Vancomycin alternatives, including clindamycin, have in vitro activity against current strains of methicillin-resistant Staphylococcus aureus (MRSA), but clinical evidence of their effectiveness is needed.

OBJECTIVE

The aim of this work was to compare health outcomes for hospitalized adult patients treated with vancomycin and clindamycin for skin and soft- tissue infections caused by MRSA.

METHODS

This was a retrospective chart review of patients admitted to University Hospital (San Antonio, Texas) with culture-proven MRSA skin or soft-tissue infections from July 1, 2006, to December 31, 2006. Patients were subdivided into groups according to antibiotics received on the first day of hospital admission. The primary outcome was composite failure, which was defined as having an additional positive MRSA culture 5 to 90 days after initial culture or requiring an additional intervention (eg, new course of antibiotics or additional incision and drainage within 90 days after initiation of therapy). Descriptive statistics were used to characterize each group; χ(2), Fisher exact, and Wilcoxon rank sum tests were used to assess differences between the vancomycin and clindamycin groups.

RESULTS

Ninety-one patients received vancomycin (n = 40) or clindamycin (n = 51) for a MRSA skin infection. Most vancomycin-treated patients received 1 g IV q12h (92.5% [37/40]), whereas most clindamycintreated patients received 600 mg IV q8h (51.0% [26/51]) or 900 mg IV q8h (27.5% [14/51]). The vancomycin and clindamycin groups had no significant differences with regard to median age (38 vs 37 years, respectively), male sex (62.5% [25/40] vs 74.5% [38/51]), or Hispanic ethnicity (77.5% [31/40] vs 78.4% [40/51]). All MRSA isolates were susceptible to vancomycin and trimethoprimsulfamethoxazole. Few patients who received clindamycin were resistant to clindamycin (3.9% [2/51]). No patients died in the hospital. There were no significant differences between the vancomycin (n = 40) and clindamycin (n = 51) groups with respect to composite failure (15.0% [6/40] vs 7.8% [4/51], respectively), microbiologic failure (2.5% [1/40] vs 3.9% [2/51]), additional inpatient interventions (5.0% [2/40] vs 3.9% [2/51]), or additional outpatient interventions (12.5% [5/40] vs 3.9% [2/51]). Most patients (93.4% [85/91]) received incision and drainage. When those who did not were excluded from the analyses, all trends remained unchanged.

CONCLUSIONS

In a single institution with a low rate of clindamycin resistance, there were no significant differences between vancomycin and clindamycin for the treatment of these hospitalized patients with MRSA skin infections, on the basis of clinical outcomes data. This finding warrants further investigation in a randomized controlled trial.

Randomized controlled trial of cephalexin versus clindamycin for uncomplicated pediatric skin infections

OBJECTIVE

To compare clindamycin and cephalexin for treatment of uncomplicated skin and soft tissue infections (SSTIs) caused predominantly by community-associated (CA) methicillin-resistant Staphylococcus aureus (MRSA). We hypothesized that clindamycin would be superior to cephalexin (an antibiotic without MRSA activity) for treatment of these infections.

PATIENTS AND METHODS

Patients aged 6 months to 18 years with uncomplicated SSTIs not requiring hospitalization were enrolled September 2006 through May 2009. Eligible patients were randomly assigned to 7 days of cephalexin or clindamycin; primary and secondary outcomes were clinical improvement at 48 to 72 hours and resolution at 7 days. Cultures were obtained and tested for antimicrobial susceptibilities, pulsed-field gel electrophoresis type, and Panton-Valentine leukocidin status.

RESULTS

Of 200 enrolled patients, 69% had MRSA cultured from wounds. Most MRSA were USA300 or subtypes, positive for Panton-Valentine leukocidin, and clindamycin susceptible, consistent with CA-MRSA. Spontaneous drainage occurred or a drainage procedure was performed in 97% of subjects. By 48 to 72 hours, 94% of subjects in the cephalexin arm and 97% in the clindamycin arm were improved (P = .50). By 7 days, all subjects were improved, with complete resolution in 97% in the cephalexin arm and 94% in the clindamycin arm (P = .33). Fevers and age less than 1 year, but not initial erythema > 5 cm, were associated with early treatment failures, regardless of antibiotic used.

CONCLUSIONS

There is no significant difference between cephalexin and clindamycin for treatment of uncomplicated pediatric SSTIs caused predominantly by CA-MRSA. Close follow-up and fastidious wound care of appropriately drained, uncomplicated SSTIs are likely more important than initial antibiotic choice.

Determination of antimicrobial susceptibility patterns and inducible clindamycin resistance in Staphylococcus aureus strains recovered from southeastern Turkey

BACKGROUND

In this study, we determined the susceptibility patterns of Staphylococcus aureus strains to various antimicrobials and prevalence of inducible clindamycin resistance (ICR) in these isolates.

METHODS

Two hundred and one S aureus strains, isolated from various clinical samples, were included in the study. Antibiotic susceptibilities were studied by disc diffusion method on the basis of the guidelines by the Clinical and Laboratory Standards Institute. The disc diffusion induction test (D test) was applied to determine ICR resistance among erythromycin-resistant S aureus isolates.

RESULTS

Of the 201 S aureus strains, 101 (50.2%) were resistant to methicillin. All strains were susceptible to vancomycin, teicoplanin, quinupristin/dalfopristin, and linezolid. It was found that 54 (53.4%) methicillin-resistant S aureus (MRSA) strains were erythromycin resistant, and 40 (39.6%) of them showed constitutive clindamycin resistance. ICR was detected in seven (6.9%) MRSA strains. It was found that 13 (13.0%) methicillin-susceptible S aureus (MSSA) strains were erythromycin resistant. Constitutive clindamycin resistance was seen in one (1.0%) MSSA strain, and ICR was detected in 10 (10.0%) cases.

CONCLUSION

There was a high rate of methicillin resistance among S aureus strains in our hospital. However, no statistically significant difference of ICR was observed between MRSA and MSSA strains (p=0.434) or between inpatients and outpatients (p=0.804). It was concluded that ICR should be routinely evaluated in each S aureus case to avoid therapy failure among patients.

Clinical practice guidelines by the infectious diseases society of america for the treatment of methicillin-resistant Staphylococcus aureus infections in adults and children

Evidence-based guidelines for the management of patients with methicillin-resistant Staphylococcus aureus (MRSA) infections were prepared by an Expert Panel of the Infectious Diseases Society of America (IDSA). The guidelines are intended for use by health care providers who care for adult and pediatric patients with MRSA infections. The guidelines discuss the management of a variety of clinical syndromes associated with MRSA disease, including skin and soft tissue infections (SSTI), bacteremia and endocarditis, pneumonia, bone and joint infections, and central nervous system (CNS) infections. Recommendations are provided regarding vancomycin dosing and monitoring, management of infections due to MRSA strains with reduced susceptibility to vancomycin, and vancomycin treatment failures.

Emergency department treatment failures for skin infections in the era of community-acquired methicillin-resistant Staphylococcus aureus

BACKGROUND

Despite rapidly increasing incidence of skin and soft tissue infections (SSTIs) presenting to emergency departments (EDs), outcome data for these infections are limited.

METHODS

This is a retrospective cohort study of children with culture-positive SSTI, managed as outpatients from a large pediatric ED in the year 2006. The primary outcome was treatment failure, defined as presence of 1 or more of the following: (1) change in antibiotic owing to poor clinical response, (2) subsequent incision and drainage, or (3) hospitalization. Demographics, isolated pathogens, and therapeutics were also assessed. To accurately capture the outcome of interest, only children who are observed in the hospital-based primary care network were included.

RESULTS

Among 148 eligible subjects, there were 158 SSTIs including 131 abscesses, 19 folliculitis, and 8 cellulitis. Mean age was 9.1 ± 6.2 years, 41.2% were male, and 94.6% were African American. Methicillin-resistant Staphylococcus aureus (MRSA) was isolated in 66%, methicillin-sensitive S. aureus (MSSA) in 21%, and others in 13%. Outcome data were available for 144 subjects (97.2%). Emergency department treatment failure rate was 7.6% (95% confidence interval, 3.3%-12.0%); 10 of 11 failures were abscesses. Only S. aureus produced treatment failure and occurred in 13.3% of MSSA and 6.4% MRSA infections (odds ratio, 1.9; 95% CI, 0.5-7.1). An antibiotic to which the organism was sensitive was prescribed for 9 (81.8%) of 11 treatment failures and did not differ between MRSA and MSSA; appropriate antibiotics were used in 91.5% of treatment successes.

CONCLUSIONS

The rate of ED treatment failure for SSTI is low and is more likely to occur with S. aureus infection, irrespective of methicillin resistance or appropriate antibiotic therapy.

Significance of MRSA strains in community associated skin and soft tissue infections

The study was conducted to determine the antibiotic susceptibility profile of community-associated methicillin resistant Staphylococcus aureus (CAMRSA) strains isolated from infections. S. aureus strains were isolated from clinical specimens using the standard procedures. CDC definition was used to classify CAMRSA. Antibiotic susceptibility test was done using Kirby-Bauer disk diffusion method. Double disk diffusion method (D-test) was used to detect inducible macrolide, lincosamide and streptogramin B resistance (inducible MLS B resistance ). A total of 83 CAMRSA were isolated from abscesses and other skin infections in persons without known risk factors for MRSA infection. All CAMRSA were susceptible to vancomycin. Out of 83 CAMRSA, 13 (15.65%) were D-test positive (inducible MLS B positive) and 6 (7.23%) were positive for constitutive MLS B resistance. Eight strains (9.63%) were resistant to tetracycline and 26 (31.32%) strains were resistant to erythromycin. Increased rate of inducible clindamycin resistance among CAMRSA indicates the importance of identification of such strains by D test to avoid treatment failure when clindamycin is used.

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.

Management of acute hematogenous osteomyelitis in children

In children, osteomyelitis is primarily hematogenous in origin and acute in nature. The principal cause of osteomyelitis in children is Staphylococcus aureus, and both the epidemiology and pathogenesis of S. aureus infections, including osteomyelitis, have changed in recent years owing to the emergence of community-associated methicillin-resistant S. aureus. This review focuses on advances in the diagnosis and overall management of acute hematogenous osteomyelitis in children with these changes in mind.

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) skin infections

PURPOSE OF REVIEW

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has become increasingly important as a cause of skin and soft tissue infections (SSTIs), particularly abscesses, in patients seen in the emergency department setting. The antibiotic sensitivity profile of Staphylococcus aureus isolates from SSTIs has changed over time in many geographic locations. Whether antibiotics are needed in the management of skin abscesses, and, if so, when, is controversial.

RECENT FINDINGS

A number of studies have looked at antibiotic therapy in conjunction with incision and drainage in managing abscesses. Factors evaluated were resolution of infection, need for change in antibiotic therapy, hospitalization after initial outpatient management, need for an additional drainage procedure, and recurrence of infection within 30 days after the initial incision and drainage procedure. For abscesses, clinical failure was associated with lack of adequate incision and drainage and not antibiotic use, regardless of the size of the abscess or the choice of antibiotic therapy. For other soft tissue infections, when antibiotic susceptibility data were available for the infection (impetigo or cellulitis with purulent drainage but no abscess), there was no difference in clinical resolution of MRSA infection even if the infecting organism was resistant to the antibiotic chosen for therapy.

SUMMARY

CA-MRSA has become an important cause of SSTIs. Current data suggest that most abscesses can be treated successfully with incision and drainage alone. Antibiotic choice is more crucial for management of cellulitis and should be guided by the prevalence of CA-MRSA in the community and its antibiotic susceptibility profile.

Methicillin-resistant Staphylococcus aureus: from the hospital to the community

Infections due to community-associated methicillin---resistant Staphylococcus aureus (CA-MRSA) are becoming more prevalent. CA-MRSA infections have unique epidemiologic features and virulence factors. Compared with health care-associated MRSA (HA-MRSA), most CA-MRSA is clonal type USA300 or 400 and has the Staphylococcal cassette chromosome mec type IV, which carries the mecA gene that encodes for resistance to methicillin and other beta-lactam antibiotics but generally not for other antibiotics. CA-MRSA often contains various virulence factors that may result in tissue necrosis. CA-MRSA clinical presentation includes mostly skin and soft tissue infections and less frequently pneumonia. In many of the small soft tissue abscesses due to CA-MRSA, primary treatment with surgical drainage may result in improvement without antibiotic therapy. Optimal treatment and prevention of CA-MRSA infections are unclear. However, distinction between CA-MRSA and HA-MRSA may be less relevant in the future, as CA-MRSA strains are now diagnosed in the hospital setting.

Community-associated meticillin-resistant Staphylococcus aureus

Meticillin-resistant Staphylococcus aureus (MRSA) is endemic in hospitals worldwide, and causes substantial morbidity and mortality. Health-care-associated MRSA infections arise in individuals with predisposing risk factors, such as surgery or presence of an indwelling medical device. By contrast, many community-associated MRSA (CA-MRSA) infections arise in otherwise healthy individuals who do not have such risk factors. Additionally, CA-MRSA infections are epidemic in some countries. These features suggest that CA-MRSA strains are more virulent and transmissible than are traditional hospital-associated MRSA strains. The restricted treatment options for CA-MRSA infections compound the effect of enhanced virulence and transmission. Although progress has been made towards understanding emergence of CA-MRSA, virulence, and treatment of infections, our knowledge remains incomplete. Here we review the most up-to-date knowledge and provide a perspective for the future prophylaxis or new treatments for CA-MRSA infections.