Community-acquired methicillin-resistant Staphylococcus aureus in pediatrics

Clonal Complexes Distribution of Staphylococcus aureus Isolates from Clinical Samples from the Caribbean Islands

The aim of this study was to comprehensively characterise S. aureus from the Caribbean Islands of Trinidad and Tobago, and Jamaica. A total of 101 S. aureus/argenteus isolates were collected in 2020, mainly from patients with skin and soft tissue infections. They were characterised by DNA microarray allowing the detection of ca. 170 target genes and assignment to clonal complexes (CC)s and strains. In addition, the in vitro production of Panton-Valentine leukocidin (PVL) was examined by an experimental lateral flow assay. Two isolates were identified as S. argenteus, CC2596. The remaining S. aureus isolates were assigned to 21 CCs. The PVL rate among methicillin-susceptible S. aureus (MSSA) isolates was high (38/101), and 37 of the 38 genotypically positive isolates also yielded positive lateral flow results. The isolate that did not produce PVL was genome-sequenced, and it was shown to have a frameshift mutation in agrC. The high rate of PVL genes can be attributed to the presence of a known local CC8-MSSA clone in Trinidad and Tobago (n = 12) and to CC152-MSSA (n = 15). In contrast to earlier surveys, the USA300 clone was not found, although one MSSA isolate carried the ACME element, probably being a mecA-deficient derivative of this strain. Ten isolates, all from Trinidad and Tobago, were identified as MRSA. The pandemic ST239-MRSA-III strain was still common (n = 7), but five isolates showed a composite SCCmec element not observed elsewhere. Three isolates were sequenced. That showed a group of genes (among others, speG, crzC, and ccrA/B-4) to be linked to its SCC element, as previously found in some CC5- and CC8-MRSA, as well as in S. epidermidis. The other three MRSA belonged to CC22, CC72, and CC88, indicating epidemiological connections to Africa and the Middle East.

Characterisation of Methicillin-Resistant Staphylococcus aureus from Alexandria, Egypt

The present study aims to characterise clinical MRSA isolates from a tertiary care centre in Egypt's second-largest city, Alexandria. Thirty isolates collected in 2020 were genotypically characterised by microarray to detect their resistance and virulence genes and assign them to clonal complexes (CC) and strains. Isolates belonged to 11 different CCs and 14 different strains. CC15-MRSA-[V+fus] (n = 6), CC1-MRSA-[V+fus+tir+ccrA/B-1] (PVL+) (n = 5) as well as CC1-MRSA-[V+fus+tir+ccrA/B-1] and CC1153-MRSA-[V+fus] (PVL+) (both with n = 3) were the most common strains. Most isolates (83%) harboured variant or composite SCCmec V or VI elements that included the fusidic acid resistance gene fusC. The SCCmec [V+fus+tir+ccrA/B-1] element of one of the CC1 isolates was sequenced, revealing a presence not only of fusC but also of blaZ, aacA-aphD and other resistance genes. PVL genes were also common (40%). The hospital-acquired MRSA CC239-III strain was only found twice. A comparison to data from a study on strains collected in 2015 (Montelongo et al., 2022) showed an increase in fusC and PVL carriage and a decreasing prevalence of the CC239 strain. These observations indicate a diffusion of community-acquired strains into hospital settings. The beta-lactam use in hospitals and the widespread fusidic acid consumption in the community might pose a selective pressure that favours MRSA strains with composite SCCmec elements comprising mecA and fusC. This is an unsettling trend, but more MRSA typing data from Egypt are required.

The Correlation Between Biofilm-Forming Ability of Community-Acquired Methicillin-Resistant Staphylococcus aureus Isolated from the Respiratory Tract and Clinical Characteristics in Children

Objective

This study aimed to investigate the biofilm-forming ability, molecular typing, and antimicrobial resistance of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) strains isolated from the respiratory tract of children and their correlation with clinical characteristics.

Methods

All CA-MRSA strains were isolated from hospitalized children, and their presentation, molecular typing, antimicrobial susceptibility, and biofilm formation were investigated. The clinical characteristics were compared between the strong and weak biofilm producer groups.

Results

Fifty-three CA-MRSA strains were isolated from the respiratory samples of 53 children, with nearly half of them being young infants (0-12 months). Approximately, 88.7% (47/53) of the isolates were resistant to four or more antibiotics, mainly β-lactam antibiotics, lincosamides, and macrolides. Twelve sequence types (STs) and 20 subtypes of staphylococcal protein A (spa) typing were identified, with ST59-t437 (39.6%, 21/53) as the predominant subtype. All strains showed the ability to form biofilms. When compared to children with weak biofilm-forming CA-MRSA strains, those with strong biofilm-forming strains had higher proportions of lower respiratory tract infections (LRTI) (88.5% vs 59.3%), obvious cough symptoms (84.6% vs 51.9%), and severe chest imaging manifestations (76.9% vs 37.0%). Furthermore, a strong biofilm-forming ability significantly increased the risk of prolonged cough in children with LRTI (44.4% vs 14.3%), and a positive correlation between the duration of cough and the extent of biofilm formation was observed. Medical history investigation revealed that the strong biofilm-forming group had a much higher percentage of macrolides intake than the weak biofilm-forming group in the last month before admission (61.5% vs 14.8%).

Conclusion

ST59-t437 was the most prevalent clone in CA-MRSA respiratory isolates among the hospitalized children. All CA-MRSA strains formed biofilms. The stronger the biofilm-forming ability, the more serious and prolonged were the respiratory symptoms.

Panton-Valentine Leukocidin Induces Cytokine Release and Cytotoxicity Mediated by the C5a Receptor on Rabbit Alveolar Macrophages

Necrotizing pneumonia caused by Panton-Valentine leukocidin (PVL)-positive community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has high mortality rates and is currently a serious clinical issue. PVL is a two-component toxin (LukS-PV and LukF-PV). It can cause necrosis in target cells by forming pores consisting of an octamer comprised of LukS-PV and LukF-PV. However, considering the specificity of PVL towards several target cells and species, the specific effect of PVL remains controversial. Therefore, we focused on necrotizing pneumonia caused by PVL-positive S. aureus and clarified the effect of PVL on alveolar macrophages, which play a central role in innate immunity in the alveolar space. We constructed recombinant PVL (rPVL) components and stimulated alveolar macrophages isolated from rabbits to evaluate cytotoxicity and pro-inflammatory cytokine release. Recombinant LukS-PV (rLukS-PV), but not recombinant LukF-PV (rLukF-PV), induced pro-inflammatory cytokine release. Specifically, tumor necrosis factor (TNF)-α release was mediated by the C5a receptor (C5aR) expressed on rabbit alveolar macrophages, and the toxicity of rPVL, consisting of rLukS-PV and rLukF-PV, towards rabbit alveolar macrophages was mediated by the same receptor. Overall, our findings shed light on the C5aR-mediated cytotoxic effect of PVL on alveolar macrophages, which may be useful for understanding the mechanism of necrotizing pneumonia caused by PVL.

Linoleic acid salt with ultrapure soft water as an antibacterial combination against dermato-pathogenic Staphylococcus spp

AIMS

Skin colonization of Staphylococcus spp. critically affects the severity of dermatitis in humans and animals. We examined different types of fatty acid salts for their antibacterial activity against Staphylococcus spp. when used in ultrapure soft water (UPSW). We also evaluated their therapeutic effect on a spontaneous canine model of dermatitis.

METHODS AND RESULTS

UPSW, in which Ca(++) and Mg(++) were replaced with Na(+) , was generated using a water softener with cation-exchange resin. Staphylococcus aureus (Staph. aureus), Staphylococcus intermedius (Staph. intermedius), and Staphylococcus pseudintermedius (Staph. pseudintermedius) were incubated with various fatty acid salts in distilled water (DW) or UPSW and the number of bacteria was counted. Among the fatty acids, oleic acid salt and linoleic acid (LA) salt reduced the number of these bacteria. Also, UPSW enhanced the antibacterial effect of LA on Staph. spp. In spontaneously developed itchy dermatitis in companion dogs, shampoo treatment with liquid soap containing 10% LA in UPSW improved skin conditions.

CONCLUSIONS

LA salt showed antibacterial activity against Staph. spp. Treatment with soap containing LA with UPSW reduced clinical conditions in dogs with dermatitis.

SIGNIFICANCE AND IMPACT OF THE STUDY

Because colonization of Staph. spp. on the skin exacerbates dermatitis, the use of LA-containing soap in UPSW may reduce unpleasant clinical symptoms of the skin.

Emergency ultrasound-assisted examination of skin and soft tissue infections in the pediatric emergency department

OBJECTIVES

The objective was to evaluate the test characteristics of clinical examination (CE) with the addition of bedside emergency ultrasound (CE+EUS) compared to CE alone in determining skin and soft tissue infections (SSTIs) that require drainage in pediatric patients.

METHODS

This was a prospective study of CE+EUS as a diagnostic test for the evaluation of patients 2 months to 19 years of age evaluated for SSTIs in a pediatric emergency department (ED). Two physicians clinically and independently evaluated each lesion, and the reliability of the CE for diagnosing lesions requiring drainage was calculated. Trained pediatric emergency physicians performed US following their CEs. The authors determined and compared the test characteristics for evaluating a SSTI requiring drainage for CE alone and for CE+EUS for those lesions in which the two physicians agreed and were certain regarding their CE diagnosis (clinically evident). The performance of CE+EUS was evaluated in those lesions in which the two physicians either disagreed or were uncertain of their diagnosis (not clinically evident). The reference standard for determining if a lesion required drainage was defined as pus expressed at the time of the ED visit or within 2 days by follow-up assessment.

RESULTS

A total of 387 lesions underwent CE+EUS and were analyzed. CE agreement between physicians was fair (κ = 0.38). For the 228 lesions for which physicians agreed and were certain of their diagnoses, sensitivity was 94.7% for CE and 93.1% for CE+EUS (difference = -1.7%; 95% confidence interval [CI] = -3.4% to 0%). The specificity of CE was 84.2% compared to 81.4% for CE+EUS (difference = -2.8%; 95% CI = -9.7% to 4.1%). For lesions not clinically evident based on CE, the sensitivity of CE was 43.7%, compared with 77.6% for CE+EUS (difference = 33.9%; 95% CI = 1.2% to 66.6%). The specificity of CE for this group was 42.0%, compared with 61.3% for CE+EUS (difference = 19.3%; 95% CI = -13.8% to 52.4%).

CONCLUSIONS

For clinically evident lesions, the addition of ultrasound (US) did not significantly improve the already highly accurate CE for diagnosing lesions requiring drainage in this study population. However, there were many lesions that were not clinically evident, and in these cases, US may improve the accuracy of the CE.

Use of bleach baths for the treatment of infected atopic eczema

Atopic eczema is one of the most common skin disorders in young children and also affects adults. Staphylococcus aureus infection is the most frequent complication of atopic eczema and is involved in the worsening of the disease. Antibiotic therapy against S. aureus has been an important component of treatment for atopic eczema but there are concerns about antibiotic overuse and increasing bacterial resistance. This has led some clinicians to recommend the use of homemade remedies such as bleach baths as an adjunctive treatment for patients with infected atopic eczema, despite the fact that there have been few published studies in this area. Balancing safety concerns with efficacious treatment is of particular importance in the paediatric population. This review discusses the historical use of bleach in medicine as well as its recent use for atopic eczema. Further, the chemistry and safety of bleach as well as alternative therapies are examined.

Nosocomial transmission of community-acquired methicillin-resistant Staphylococcus aureus in a well-infant nursery of a teaching hospital

BACKGROUND

Infection due to community-acquired strains of methicillin-resistant Staphylococcus aureus (CA-MRSA) has been reported with increasing frequency. Herein is described the nosocomial transmission of CA-MRSA involving 13 neonates and two mothers in a well-infant nursery in a teaching hospital in Saudi Arabia.

METHODS

From October to November 2009, temporally related cases of CA-MRSA skin and soft-tissue infection occurred in newborns shortly after discharge from a well-infant nursery. An outbreak investigation including case identification, review of medical records, staff screening, environmental cultures, pulsed-field gel electrophoresis, and a case-control study were conducted. Controls were selected from among asymptomatic neonates admitted to the same nursery and matched for the day of admission.

RESULTS

Fifteen subjects were found to be CA-MRSA positive: 13 neonates and two mothers. The crude attack rate among neonates was 5.5% during the outbreak period. All 13 neonates presented with skin and soft-tissue infection; one of the mothers had mastitis and a breast abscess. The source of the outbreak was not evident. Pulsed-field gel electrophoresis showed that all of the tested isolates from one strain except one, all contained the staphylococcal cassette chromosome mec (SCCmec) type IV.

CONCLUSION

MRSA strains that initially emerged in the community are now causing disease in health-care settings. Adherence to standard infection control practices, including consistent hand hygiene, in newborn nurseries is important to prevent transmission in such settings.

Community-Associated Methicillin-Resistant Staphylococcus aureus Infections in the Athlete

CONTEXT

Community-associated methicillin-resistant Staphlococcus aureus (CA-MRSA) has become of increasing concern in the athletic setting. Appropriate recognition, treatment, and prevention measures are all paramount to protect individual athletes and teamwide outbreaks.

EVIDENCE ACQUISITION

Relevant electronic databases (Medline or PubMed) through 2008 were searched. Articles and studies relevant to this topic were reviewed for pertinent clinical information.

STUDY TYPE

Clinical review.

RESULTS

CA-MRSA is an increasing problem both in the community at large and in the athletic population.

CONCLUSION

Early infections based on methicillin-resistant Staphlococcus aureus are often misidentified, leading to delay in appropriate treatment. A high level of suspicion, prompt recognition, and appropriate treatment can minimize morbidity associated with CA-MRSA. Careful selection of antibiotics in suspected cases is important, with more severe infections requiring hospitalization and intravenous antibiotics. Eradication of bacteria in colonized patients has not yet proven to be effective. Prevention of infections is multifaceted, and it includes education, proper personal hygiene, routine cleaning of equipment, and proper wound care.

Community-acquired methicillin-resistant Staphylococcus aureus hand infections in the pediatric population

PURPOSE

Recent studies have reported rates of methicillin-resistant Staphylococcus aureus (MRSA) hand infections in patients without risk factors ranging from 26% to 73%. The purpose of our study was to review a large series of pediatric hand infections to determine the rate of MRSA and identify potential risk factors.

METHODS

A retrospective review was performed on patients younger than 15 who were seen for hand infections (2001-2010). Patients were categorized according to medical problems, need for operation, abscess location, and mechanism of injury. Potential MRSA risk factors were assessed using a multivariate-regression model.

RESULTS

During the 10-year period, 415 patients were seen for hand infections. A total of 146 patients met the inclusion criteria: patients younger than 15 years of age who presented to the plastic surgery service requiring consultation for hand infections. The overall prevalence of MRSA-positive cultures was found to be 30%. The prevalence of MRSA was 29% in healthy patients and 0% in immunocompromised patients. The prevalence of MRSA increased in a linear fashion from patients without documentation of incision and drainage procedures to patients adequately treated with bedside incision and drainage to patients who required surgical drainage. There was a trend toward a higher prevalence of MRSA in deep space abscesses compared to other abscesses. Patients with a history of trauma and previous MRSA infections had a higher rate of MRSA than other patients.

CONCLUSIONS

Traditionally, MRSA has been associated with hospitalization, intravenous drug use, recent antibiotic use, and compromised immunity. In our study, more severe, deep-space abscesses requiring surgical drainage and patients with a history of previous MRSA infections were found to have a higher prevalence of MRSA. The immunocompromised patients had no cases of MRSA and had higher incidences of less virulent bacterial infections. This suggests that acquisition of community-acquired MRSA skin and soft tissue infections in children and adolescents might not be associated with the traditional risk factors.

TYPE OF STUDY/LEVEL OF EVIDENCE

Prognostic IV.

A nosocomial outbreak of community-associated methicillin-resistant Staphylococcus aureus among healthy newborns and postpartum mothers

BACKGROUND

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has increasingly been isolated from individuals with no predisposing risk factors; however, such strains have rarely been linked to outbreaks in the hospital setting. The present study describes the investigation of an outbreak of CA-MRSA that occurred in the maternal-newborn unit of a large community teaching hospital in Toronto, Ontario.

METHODS

Screening and clinical specimens collected from mothers and newborns delivered during the outbreak period, as well as from staff on the affected unit, were submitted for microbiological testing. Computerized delivery logs and nursing notes were reviewed, and a case control study was conducted.

RESULTS

Analysis by pulsed-field gel electrophoresis revealed 38 babies and seven mothers with MRSA colonization and/or infection by the same unique strain (Canadian MRSA-10-related) from September to December 2004. Isolates were characterized as having the staphylococcal chromosome cassette mec type IVa and were positive for the Panton-Valentine leukocidin gene. No one health care worker was associated with all cases; however, mothers and newborns exposed to one particular nurse (Nurse A) were almost 23 times (odds ratio 22.7, 95% CI 3.3 to 195.9) more likely to acquire MRSA than those with no such contact. MRSA was successfully isolated from Nurse A and from an environmental swab of a telephone recently used by Nurse A; both isolates matched the pulsed-field gel electrophoresis pattern of the outbreak strain.

CONCLUSION

The first nosocomial outbreak of CA-MRSA among healthy newborns and postpartum mothers in Canada is described. Effective control of sustained MRSA transmission within an institution may require prompt identification, treatment and monitoring of colonized and/or infected staff.

[Necrotizing community-acquired Staphylococcus aureus pneumonia]

Acute necrotizing pneumonia due to Panton-Valentine secreting Staphylococcus aureus was identified as a clinical entity by Gilet et al., in 2002. This severe acute necrotizing pneumonia occurring in previously healthy children and adolescents can lead to a rapid fatal outcome even if quickly diagnosed and treated. We report the case of a healthy 10-year-old girl presenting with hemorrhagic necrotizing pneumonia and septic shock. Bacteriological cultures yielded methicillin-susceptible Staphylococcus aureus. The course of the disease was characterized by recurrent uncontrolled hemoptysia leading to refractory hypoxemia. The details of the hospital stay are presented. We discuss the clinical features of the disease and describe recent epidemiologic data and Panton-Valentine toxin research results as well as primary hospital care and treatment.

Imaging of Chest Infections in Children

■ Imaging studies have limited value in the differentiation between viral and bacterial lower respiratory tract infections (moderate evidence).

■ CT provides more information than plain radiographs for complicated pulmonary infections with empyema, pleural effusion, or bronchopleural fistula (moderate evidence).

■ In immunocompromised patients, CT has been shown to characterize the type of infection better than plain radiographs (moderate evidence).

■ Ultrasound has an advantage over CT in the identification and characterization of complicated effusions (moderate evidence).

■ Early detection and therefore intervention for pleural complications of pneumonia are critical and can result in better outcomes (moderate evidence).

■ Early surgery (VATS) is more cost-effective than thoracotomy (without or with image guidance) in the treatment of empyemas in children (strong evidence).

Current issues in the management of sinonasal methicillin-resistant Staphylococcus aureus

PURPOSE OF REVIEW

Staphylococcus aureus is an important pathogen, contributing to both pediatric and adult infections in the USA. In recent years, methicillin-resistant Staphylococcus aureus (MRSA) has become a source of public fear and outcry. In this article, we review facts and fiction of sinonasal MRSA.

RECENT FINDINGS

Although the exact role of bacteria in chronic rhinosinusitis continues to be debated, the role of MRSA in these patients is even less apparent. When MRSA is involved, there are few to guide treatment. Oral, parenteral, and topical antibiotics are all used in the treatment of sinonasal MRSA. MRSA eradication has been advocated by some; however, there are few data to support the efficacy of eradication. Current treatment regimens by the authors are reviewed.

SUMMARY

There is much that is not known about the role of MRSA in sinonasal infection, and the impact of sinonasal MRSA on the health quality of the community also remains undefined. Treatment outlines are presented; however, with the current state of data, these treatment preferences lack a solid, evidence-based foundation that is favored. Future studies will lay the foundation for more rigorously supported treatment algorithms.

Treatment of Staphylococcus aureus colonization in atopic dermatitis decreases disease severity

OBJECTIVES

The goals were to determine the prevalence of community-acquired methicillin-resistant Staphylococcus aureus colonization in patients with atopic dermatitis and to determine whether suppression of S aureus growth with sodium hypochlorite (bleach) baths and intranasal mupirocin treatment improves eczema severity.

METHODS

A randomized, investigator-blinded, placebo-controlled study was conducted with 31 patients, 6 months to 17 years of age, with moderate to severe atopic dermatitis and clinical signs of secondary bacterial infections. All patients received orally administered cephalexin for 14 days and were assigned randomly to receive intranasal mupirocin ointment treatment and sodium hypochlorite (bleach) baths (treatment arm) or intranasal petrolatum ointment treatment and plain water baths (placebo arm) for 3 months. The primary outcome measure was the Eczema Area and Severity Index score.

RESULTS

The prevalence of community-acquired methicillin-resistant S aureus in our study (7.4% of our S aureus-positive skin cultures and 4% of our S aureus-positive nasal cultures) was much lower than that in the general population with cultures at Children's Memorial Hospital (75%-85%). Patients in the group that received both the dilute bleach baths and intranasal mupirocin treatment showed significantly greater mean reductions from baseline in Eczema Area and Severity Index scores, compared with the placebo group, at the 1-month and 3-month visits. The mean Eczema Area and Severity Index scores for the head and neck did not decrease for patients in the treatment group, whereas scores for other body sites (submerged in the dilute bleach baths) decreased at 1 and 3 months, in comparison with placebo-treated patients.

CONCLUSIONS

Chronic use of dilute bleach baths with intermittent intranasal application of mupirocin ointment decreased the clinical severity of atopic dermatitis in patients with clinical signs of secondary bacterial infections. Patients with atopic dermatitis do not seem to have increased susceptibility to infection or colonization with resistant strains of S aureus.

Lemierre's syndrome: methicillin-resistant Staphylococcus aureus (MRSA) finds a new home

Lemierre's syndrome is septic thrombophlebitis of the internal jugular vein, arising as a complication of an oropharyngeal infection. This thrombophlebitis frequently results in septic emboli to organs such as the lungs. The causative agent in most previously described cases is Fusobacterium necrophorum, an anaerobic Gram-negative organism. We present the case of an 8-year-old previously healthy girl who came to the Emergency Department with a 5-day history of left-sided neck pain and was subsequently diagnosed with methicillin-resistant Staphylococcus aureus (MRSA) Lemierre's syndrome. MRSA has not previously been described in Lemierre's syndrome in the Emergency Medicine literature. The clinical presentation, findings, and management of the syndrome are discussed. Regardless of etiology, once the diagnosis of Lemierre's syndrome is made, long-term broad-spectrum intravenous therapy will be necessary.

Emergency department management of community-acquired methicillin-resistant Staphylococcus aureus

Staphylococcus aureus is a known cause of a variety of illnesses that present to the emergency department, including skin and soft tissue infections, pneumonia, and sepsis. Managing these conditions has become more difficult with the emergence of bacterial strains in the community that are resistant to traditional first-line antibiotics. Emergency care providers need to be aware of the increased prevalence of these resistant bacteria, to understand the characteristics of the infections with which they are associated, and to know the effective antibiotic options for treating these bacterial infections in the emergency department patient population.

Acute rise in methicillin-resistant Staphylococcus aureus infections in a coastal community

OBJECTIVE

Describe the incidence of head and neck community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections over a 5-year period at a coastal tertiary medical center.

STUDY DESIGN

Retrospective chart review.

SUBJECTS AND METHODS

All patients presenting to the otolaryngology service with cultures taken from head and neck infections between 1999 and 2004 were eligible for inclusion. Statistical analysis was used to determine significance of the changing incidence of isolated organisms over the study period.

RESULTS

CA-MRSA infections rose from 21% to 64% over the 5-year period. The increasing trend in CA-MRSA infections reached statistical significance from 2003 to 2004. All CA-MRSA isolates were resistant to cefazolin and penicillin, but most were sensitive to clindamycin.

CONCLUSIONS

Our data demonstrates a striking increase in the incidence of CA-MRSA. We have tailored our treatment of cutaneous head and neck infections to include empiric treatment for CA-MRSA using clindamycin. Awareness and monitoring of this trend will be important for all practitioners involved in the care of these patients.

Severe Sepsis Attributable to Community-Associated Methicillin-Resistant Staphylococcus aureus: An Emerging Fatal Problem

We observed a number of cases of sepsis from bacteremia in children from community-associated methicillin-resistant Staphylococcus aureus (MRSA), which led us to study its patterns of infection and outcome. A retrospective review identifying children admitted to our institution with blood culture-proven community-associated MRSA sepsis over a 2-year period was performed. The inclusion criteria were younger than 19 years old, two or more blood cultures for MRSA within 48 hours of admission, evidence of systemic inflammatory response syndrome, and no prior hospital admissions within 6 months. Eight patients were included; seven required mechanical ventilation. Vasopressors were required in seven patients. Four patients required extra-corporeal membrane oxygenation. Four patients had culture-proven septic arthritis or thrombophlebitis and three of these patients developed bilateral necrotizing pneumonia. Bilateral necrotizing pneumonia was identified in the other four patients, but the primary source of infection was never identified. The overall intact neurologic survival was 50 per cent. Children with severe community-associated MRSA sepsis can rapidly progress to cardiorespiratory failure. Mortality appears to be high, and children may benefit from a search of their soft tissues and joints to identify the source of infection to prevent embolic dissemination.

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.

Community-acquired methicillin-resistant Staphylococcus aureus

Published data confirm that community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infections are increasing in incidence in both urban and rural settings. The statistical risk is higher for athletes, military personnel, prison inmates, intravenous drug abusers, the homeless, children in daycare, and certain Native American groups, but the infections are by no means restricted to these populations. Roughly 85% of the infections involve the skin and subcutaneous tissue, with the most common presentations being an abscess or folliculitis. The typical associated gene cassette is quite small and codes only for methicillin resistance. Abscesses generally respond to drainage.

LEARNING OBJECTIVE

At the conclusion of this learning activity, participants should recognize groups at high risk for community-acquired MSRA infections and manage these infections appropriately.

Interference between Streptococcus pneumoniae and Staphylococcus aureus: In vitro hydrogen peroxide-mediated killing by Streptococcus pneumoniae

The bactericidal activity of Streptococcus pneumoniae toward Staphylococcus aureus is mediated by hydrogen peroxide. Catalase eliminated this activity. Pneumococci grown anaerobically or genetically lacking pyruvate oxidase (SpxB) were not bactericidal, nor were nonpneumococcal streptococci. These results provide a possible mechanistic explanation for the interspecies interference observed in epidemiologic studies.

Community-associated Methicillin-resistant Staphylococcus aureus: Overview and Local Situation

Introduction: Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has emerged worldwide. In contrast to healthcare-associated MRSA (HA-MRSA), CA-MRSA isolates are usually susceptible to multiple non-beta-lactam antibiotics and cause a distinct spectrum of infections in epidemiologically disparate populations – in particular, cutaneous abscesses, necrotising fasciitis and necrotising pneumonia. They arise from a broader genetic background, and possess differing virulence genes. We aim to describe the distribution of different molecular subtypes of CA-MRSA among various regions and discuss briefly the implications of CA-MRSA from a local perspective. Methods: Literature review of articles on CA-MRSA, focusing mainly on reports where the genetic background of isolates had been analysed using multi-locus sequence typing (MLST). Singapore data were obtained from the local CA-MRSA database. Results: MLST analysis demonstrated the presence of epidemic subtypes of CA-MRSA within most geographic areas. In parts of the United States, community MRSA infections currently exceed those caused by their methicillin-susceptible counterparts. In Singapore, CA-MRSA infections are increasing, predominantly as a result of the spread of ST30 clones. Conclusion: Available evidence suggests that the emergence of MRSA from the community is not going to be a transient phenomenon. Local guidelines for dealing with this phenomenon at both therapeutic and preventive levels are needed prior to the potential development of a situation mirroring that of meso-endemic HA-MRSA in local hospitals or CA-MRSA epidemics in parts of USA. Key words: Bacterial typing, Epidemic, Epidemiology, Infection control

Antimicrobial resistance in gram-positive bacteria

Gram-positive bacteria are common causes of bloodstream and other infections in hospitalized patients in the United States, and the percentage of nosocomial bloodstream infections caused by antibiotic-resistant gram-positive bacteria is increasing. Methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) are of particular concern. In the United States, approximately 60% of staphylococcal infections in the intensive care unit are now caused by MRSA, and percentages continue to rise. Outbreaks of hospital-acquired MRSA (HA-MRSA) are typically the result of clonal spread by MRSA being transferred from patient to patient, frequently using healthcare personnel as intermediaries. HA-MRSA strains are generally multidrug resistant. Vancomycin is the standard treatment for serious MRSA infections, but a few cases of vancomycin-resistant S aureus (VRSA) have recently emerged in the United States. Community-acquired MRSA (CA-MRSA) is also increasing. Soft tissue infections are the most frequent presentations of CA-MRSA, but life-threatening invasive infections occur as well, including necrotizing pneumonia. The mechanisms of methicillin resistance are the same for CA-MRSA and HA-MRSA, but susceptibilities to non-â-lactam antibiotics often differ. CA-MRSA exhibits broader antibiotic susceptibility than does HA-MRSA. The proportion of enterococci resistant to vancomycin continues to rise in the hospital setting, with the overwhelming majority of infections due to Enterococcus faecium. Clonal spread of VRE has been documented, but polyclonal outbreaks associated with antimicrobial use are also common. The relations between antibiotic use and VRE colonization are complex and related to the antienterococcal activity, biliary excretion, and antianaerobic activity of the antibiotic. Recent results show a decline in invasive pneumococcal disease (IPD) since the introduction of 7-valent pneumococcal conjugate vaccine, and suggest that, where available, vaccines may be useful in the battle to slow the spread of resistant gram-positive cocci.

Antimicrobial resistance in gram-positive bacteria

Gram-positive bacteria are common causes of bloodstream and other infections in hospitalized patients in the United States, and the percentage of nosocomial bloodstream infections caused by antibiotic-resistant gram-positive bacteria is increasing. Methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) are of particular concern. In the United States, approximately 60% of staphylococcal infections in the intensive care unit are now caused by MRSA, and percentages continue to rise. Outbreaks of hospital-acquired MRSA (HA-MRSA) are typically the result of clonal spread by MRSA being transferred from patient to patient, frequently using healthcare personnel as intermediaries. HA-MRSA strains are generally multidrug resistant. Vancomycin is the standard treatment for serious MRSA infections, but a few cases of vancomycin-resistant S aureus (VRSA) have recently emerged in the United States. Community-acquired MRSA (CA-MRSA) is also increasing. Soft tissue infections are the most frequent presentations of CA-MRSA, but life-threatening invasive infections occur as well, including necrotizing pneumonia. The mechanisms of methicillin resistance are the same for CA-MRSA and HA-MRSA, but susceptibilities to non-beta-lactam antibiotics often differ. CA-MRSA exhibits broader antibiotic susceptibility than does HA-MRSA. The proportion of enterococci resistant to vancomycin continues to rise in the hospital setting, with the overwhelming majority of infections due to Enterococcus faecium. Clonal spread of VRE has been documented, but polyclonal outbreaks associated with antimicrobial use are also common. The relations between antibiotic use and VRE colonization are complex and related to the antienterococcal activity, biliary excretion, and antianaerobic activity of the antibiotic. Recent results show a decline in invasive pneumococcal disease (IPD) since the introduction of 7-valent pneumococcal conjugate vaccine, and suggest that, where available, vaccines may be useful in the battle to slow the spread of resistant gram-positive cocci.

Community-Acquired Methicillin Resistant Staphylococcus aureus Skin Infection

Staphylococcus aureus is one of the most common pathogens in skin and soft tissue infections, as well as in potentially serious nosocomial infections in patients who acquire it when hospitalized. Penicillin was introduced in the 1940's as an effective treatment against S. aureus. However, shortly after penicillin's introduction, penicillin resistance to S. aureus emerged due to a plasmid-mediated beta-lactamase enzyme. In 1959, a semisynthetic penicillin, methicillin was introduced to overcome the resistance problem. However, within a year, bacteria resistant to methicillin and other penicillinase stable beta-lactams, were present. Worldwide emergence of methicillin-resistant S aureus (MRSA) was established by the 1980's. Since that time, MRSA has become widespread in hospitals and long-term care facilities around the world, accounting for numerous nosocomial infections. Recently, there has been an alarming increase in the incidence of community-acquired MRSA (CA-MRSA). Patients with CA-MRSA began to be reported in the early 1990's and its prevalence has continued to increase. This paper summarizes the current information known about CA-MRSA as it relates to skin infections including populations at risk, clinical presentation, and treatment options.

Control of a cluster of community-associated, methicillin-resistant Staphylococcus aureus in neonatology

To control an outbreak of community-associated MRSA (CA-MRSA) in a neonatology unit, an investigation was conducted that involved screening neonates and parents, molecular analysis of MRSA isolates and long-term follow-up of cases. During a two-month period in the summer of 2000, Panton-Valentine leukocidin (PVL)-producing CA-MRSA (strain ST5-MRSA-IV) was detected in five neonates. The mother of the index caseshowed signs of mastitis and wound infection and consequently tested positive for CA-MRSA. A small cluster of endemic, PVL-negative MRSA strains (ST228-MRSA-I) occurred in parallel. Enhanced hygiene measures, barrier precautions, topical decolonization of carriers, and cohorting of new admissions terminated the outbreak. Four months after the outbreak, the mother of another neonate developed furunculosis with the epidemic CA-MRSA strain. One infant had persistent CA-MRSA carriage resulting in skin infection in a sibling four years after the outbreak. In conclusion, an epidemic CA-MRSA strain was introduced by the mother of the index case. This spread among neonates and was subsequently transmitted to another mother and a sibling. This is the first report of a successfully controlled neonatology outbreak of genetically distinct PVL-producing CA-MRSA in Europe.

Cutaneous bacterial infections in the newborn

PURPOSE OF REVIEW

This review examines neonatal bacterial skin infections with respect to host immunity, bacterial pathogens, patterns of infection, and new therapeutic approaches.

RECENT FINDINGS

Advances have been made in our understanding of innate host defense and the emerging role of cutaneous antimicrobial peptides of the cathelicidin and defensin families. Toll-like receptors are being investigated with respect to their interactions with bacteria and other components of the innate immune defense, such as the antimicrobial peptides. The epidermal barrier remains an active area of research. Studies confirm that maintaining an intact epidermal barrier by minimizing exposure to soap and by not removing vernix caseosa are simple measures to improve skin barrier function. Active barrier-enhancing measures such as the application of topical emollients have shown mixed results in the prevention of nosocomial infection. A meta-analysis of studies performed in developed countries showed a trend of increasing risk for coagulase-negative staphylococcal infection. By contrast, a randomized controlled trial showed that infants treated with sunflower oil are less likely to experience nosocomial infections than are control infants. Infants with bacteremia and no known source of infection should be carefully examined because cutaneous abscesses have been shown to be an important nidus of infection. Methicillin-resistant Staphylococcus aureus is reaching epidemic proportions, making surface cultures an essential part of the evaluation of cutaneous bacterial infection.

SUMMARY

New insights have been gained regarding the basic science of neonatal host defense and these advances may produce new ways of approaching the prevention and treatment of bacterial skin infections in the newborn period.