Treatment of community-acquired methicillin-resistant Staphylococcus aureus in children

Metagenomic insights into isolable bacterial communities and antimicrobial resistance in airborne dust from pig farms

This study aims to investigate bacterial communities and antimicrobial resistance (AMR) in airborne dust from pig farms. Airborne dust, pig feces and feed were collected from nine pig farms in Thailand. Airborne dust samples were collected from upwind and downwind (25 meters from pig house), and inside (in the middle of the pig house) of the selected pig house. Pig feces and feed samples were individually collected from the pen floor and feed trough from the same pig house where airborne dust was collected. A direct total bacteria count on each sampling plate was conducted and averaged. The ESKAPE pathogens together with Escherichia coli, Salmonella, and Streptococcus were examined. A total of 163 bacterial isolates were collected and tested for MICs. Pooled bacteria from the inside airborne dust samples were analyzed using Metagenomic Sequencing. The highest bacterial concentration (1.9-11.2 × 103 CFU/m3) was found inside pig houses. Staphylococcus (n = 37) and Enterococcus (n = 36) were most frequent bacterial species. Salmonella (n = 3) were exclusively isolated from feed and feces. Target bacteria showed a variety of resistance phenotypes, and the same bacterial species with the same resistance phenotype were found in airborne dust, feed and fecal from each farm. Metagenomic Sequencing analysis revealed 1,652 bacterial species across all pig farms, of which the predominant bacterial phylum was Bacillota. One hundred fifty-nine AMR genes of 12 different antibiotic classes were identified, with aminoglycoside resistance genes (24%) being the most prevalent. A total of 251 different plasmids were discovered, and the same plasmid was detected in multiple farms. In conclusion, the phenotypic and metagenomic results demonstrated that airborne dust from pig farms contained a diverse array of bacterial species and genes encoding resistance to a range of clinically important antimicrobial agents, indicating the significant role in the spread of AMR bacterial pathogens with potential hazards to human health. Policy measurements to address AMR in airborne dust from livestock farms are mandatory.

Necrotizing pneumonia and purulent meningitis caused by bloodstream infection of CA-MRSA in a child: A rare case report

CASE PRESENTATION

We report the case of a girl aged 2 years and 10 months who had fever for 2 days, vomiting, poor mental status for 1 day, and one episode of convulsions.

SYMPTOMS AND SIGNS

The patient experienced a rapid onset of symptoms with fever, vomiting, and convulsions. Upon physical examination on admission, she presented with the following: temperature 38.6°C; pulse 185 beats/min; respiration 49 beats/min; blood pressure 89/51 mmHg; drowsiness; piebald skin all over her body; rice-grain-sized pustular rashes scattered on the front chest and both lower limbs, protruding from the surface of the skin; bilateral pupils that were equal in size and a circle with a diameter of about 3.0 mm, and slow light reflex; cyanotic lips; shortness of breath; positive for the three-concave sign; a small amount of phlegm that could be heard in both lungs; capillary refill time of 5 s; cold extremities; and a positive Babinski sign.

DIAGNOSTIC METHOD

A chest computed tomography scan showed multiple nodular and flake-like high-density shadows of varying sizes in each lobe in bilateral lungs, and a cavity with blurred edges could be seen in some nodules. A cranial magnetic resonance imaging examination demonstrated that the hyperintensity of diffusion-weighted imaging could be observed on the left cerebellar hemisphere and left parietal blade. Blood cultures, sputum, cerebrospinal fluid, and bronchoalveolar lavage fluid (BALF) by fiberoptic bronchoscopy all indicated the growth of methicillin-resistant Staphylococcus aureus (MRSA).

TREATMENT METHODS

After admission, the child was given meropenem combined with vancomycin, cefoperazone sulbactam combined with rifamycin, linezolid (oral) for anti-infection successively, and other adjuvant therapies.

CLINICAL OUTCOMES

The patient recovered clinically and was discharged from our hospital.

RECOMMENDED READERS

Neurology; Respiratory Medicine; Infectious Diseases Department.

Weaning of septic patients from the ventilator in the intensive care unit by attention approach to common antibiotic regimens

Background:

Sepsis is a chronic blood infection that is more common in patients with ventilatory and disability. This study aimed to evaluate the effect of common antibiotic regimens on weaning sepsis patients from mechanical ventilator.

Methods:

In this prospective cross-sectional study, we classified 70 sepsis patients under mechanical ventilation which sedates with midazolam and do not take muscle relaxants into two groups: meropenem and levofloxacin versus meropenem, levofloxacin, and clindamycin. The duration of intubation and the number of patients who needed re-intubation (and their duration of extubation) were recorded. Data were analyzed using SPSS software.

Results:

In the present study, 68.6% were male and 31.4% were female. The mean age was calculated to be 37.98. The mean duration of mechanical ventilation and stay in the ICU in the group of two drugs (meropenem + levofloxacin) showed a significant decrease compared to the group of three drugs (P < 0.05). But no significant difference was observed in terms of ventilator connection time (P < 0.05).

Conclusion:

The differences in terms of mean duration of mechanical ventilation and ICU stay between the groups indicate that the two-drug regimen (meropenem + levofloxacin) is more efficient in bringing [sepsis] patients back to recovery.

A decade of antimicrobial resistance in Staphylococcus aureus: A single center experience

Background

The emergence of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) resulted in the recommended use of clindamycin and trimethoprim-sulfamethoxazole (TMP-SMX) for suspected S. aureus infections. The objective of this study was to determine the resistance to methicillin, clindamycin, and TMP-SMX in S. aureus isolates during a 10-year period.

Methods

Retrospective review of the antimicrobial susceptibilities of all S. aureus isolates in the outpatient and inpatient settings at Nationwide Children’s Hospital from 1/1/2005 to 12/31/2014. Duplicate isolates from the same site and year and those obtained for MRSA surveillance or from patients with cystic fibrosis were excluded.

Results

Of the 57,788 S. aureus isolates from 2005–2014, 40,795 (71%) were included. In the outpatient setting, methicillin resistance decreased from 54% to 44% (p<0.001) while among inpatient isolates, no significant change was observed. From 2009–2014, resistance to clindamycin among outpatient isolates increased from 16% to 17% (p = 0.002) but no significant trend was observed among inpatient isolates (18% to 22%). Similarly, TMP-SMX resistance increased in outpatient S. aureus isolates from 2005–2014 (0.9% to 4%, p<0.001) but not among inpatient isolates. Among both inpatient and outpatient isolates, methicillin-susceptible S. aureus (MSSA) exhibited higher resistance to both clindamycin and TMP-SMX than MRSA. In addition, resistance to methicillin, clindamycin and TMP-SMX varied widely according to the site of specimen collection.

Conclusion

In a decade where >40,000 S. aureus isolates were identified at a large pediatric hospital, substantial changes in methicillin, clindamycin, and TMP-SMX resistance occurred. These findings highlight the importance of ongoing surveillance of the local antimicrobial resistance in S. aureus in order to guide empiric antimicrobial therapy.

Current and future treatment options for community-associated MRSA infection

INTRODUCTION

Community-associated MRSA (CA-MRSA) represents a global epidemic which beautifully encapsulates the fascinating ability of bacterial organisms to adapt quickly on an evolutionary basis to the extreme selective pressure of antibiotic exposure. In stark contrast to Healthcare-associated MRSA (HA-MRSA), it has become apparent that CA-MRSA is less straight forward of a challenge in terms of controlling its transmission, and has forced clinicians to adjust empiric management of clinical syndromes such as skin and soft tissue infection (SSTI) as well as pneumonia.

AREAS COVERED

This review details the history and epidemiology of CA-MRSA, while covering both current and future treatment options that are and may be available to clinicians. The authors reviewed both historic and more recent literature on this ever-evolving topic.

EXPERT OPINION

While development of new anti-MRSA agents should be encouraged, the importance of antimicrobial stewardship in the battle to stay ahead of the curve with regards to the ongoing control of the MRSA epidemic should be emphasised.

Structural insights of lincosamides targeting the ribosome of Staphylococcus aureus

Antimicrobial resistance within a wide range of pathogenic bacteria is an increasingly serious threat to global public health. Among these pathogenic bacteria are the highly resistant, versatile and possibly aggressive bacteria, Staphylococcus aureus. Lincosamide antibiotics were proved to be effective against this pathogen. This small, albeit important group of antibiotics is mostly active against Gram-positive bacteria, but also used against selected Gram-negative anaerobes and protozoa. S. aureus resistance to lincosamides can be acquired by modifications and/or mutations in the rRNA and rProteins. Here, we present the crystal structures of the large ribosomal subunit of S. aureus in complex with the lincosamides lincomycin and RB02, a novel semisynthetic derivative and discuss the biochemical aspects of the in vitro potency of various lincosamides. These results allow better understanding of the drugs selectivity as well as the importance of the various chemical moieties of the drug for binding and inhibition.

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.

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.

Future Trends in Antimicrobial Chemotherapy: Expert Opinion on the 43rdICAAC

The current document bestows an expert synopsis of key new information presented at the 43rd Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) meeting in 2003. Data is presented on the socio-political aspects of and policies on antimicrobial prescribing, novel mechanisms of resistance in Streptococcus pneumoniae, and current epidemiological trends in global resistance. Novel information on new (and existing) antimicrobial agents--new penicillins, cephalosporins, monobactams and oxipenem inhibitors, ketolides, glycopeptides, fluoroquinolones (and hybrids), peptides, daptomycin, aminomethylcyclines, glycylcyclines, and newer formulations of agents such as amoxycillin-clavulanate--provides renewed hope that resistant pathogens can be controlled through use of more potent agents. Improved strategies for the use of existing antimicrobial agents, such as the use of high-dose regimens, short-course therapy, also may delay or reduce the development of resistance and preserve the value of our antibiotic armamentarium.

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.

Treatment of MRSA soft tissue infections: an overview

MRSA is becoming increasingly common worldwide. With the emergence of new highly spreadable strains (community associated or CA-MRSA) novel presentation skin and soft tissue infections (SSTI) are being seen. Recurrent SSTI, including folliculitis, furunculosis and abscesses account for an increasing proportion of SSTI seen in the emergency department. Empirical antimicrobial management choices can be difficult, but clues to the nature of the MRSA may be gleaned from the history and clinical presentation. More severe SSTI due to necrotising fasciitis and purpura fulminans are emerging and warrant the broadest possible empirical Gram-positive cover, ideally with antimicrobials that stop exotoxin production, and sometimes intravenous immunoglobulin to neutralise exotoxins already produced.

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.

Public health surveillance for methicillin-resistant Staphylococcus aureus: comparison of methods for classifying health care- and community-associated infections

OBJECTIVES

We compared 3 methods for classifying methicillin-resistant Staphylococcus aureus (MRSA) infections as health care associated or community associated for use in public health surveillance.

METHODS

We analyzed data on MRSA infections reported to the Michigan Department of Community Health from October 1, 2004, to December 31, 2005. Patient demographics, risk factors, infection information, and susceptibility were collected for 2151 cases. We classified each case by the health care risk factor, infection-type, and susceptibility pattern methods and compared the results of the 3 methods.

RESULTS

Demographic, clinical, and microbiological variables yielded similar health care-associated and community-associated distributions when classified by risk factor and infection type. When 2 methods yielded the same classifications, the overall distribution was similar to classification by 3 methods. No specific combination of 2 methods was superior.

CONCLUSIONS

MRSA categorization by 2 methods is more accurate than it is by a single method. The health care risk factor and infection-type methods yield comparable classification results. Accuracy is increased by using more variables; however, further research is needed to identify the optimal combination.

The emergence of severe, community-acquired methicillin-resistant Staphylococcus aureus infections

The number of community acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections is rapidly increasing. Most CA-MRSA infections are localized soft tissue infections; however, severe life-threatening infections have been occasionally described. This report serves to increase the awareness of severe CA-MRSA infections by presenting a fulminant CA-MRSA infection with sepsis, endocarditis, septic pulmonary emboli, and extensive soft tissue and bone destruction. A review of the literature revealed 14 cases of severe CA-MRSA infections with a median age of 13 y; 93% had no underlying medical condition. Only 1 case was initially treated with antibiotics effective for MRSA. The fatality rate was 64%, and 40% of patients who survived had significant disabilities.

Usefulness of antibiogram surveillance for methicillin-resistant Staphylococcus aureus in outpatient pediatric populations

We assessed the impact of distributing an outpatient age-specific methicillin-resistant Staphylococcus aureus (MRSA) antibiogram on physician knowledge of MRSA prevalence and choice of empiric therapy. Questionnaires were given to 125 physicians at outpatient pediatric clinics in Monroe County, NY, before and after antibiogram distribution (response rates, 42% and 24%, respectively). The median physician-estimated MRSA prevalence (among S. aureus skin infections) was 15% before they received the antibiogram and 20% after. According to the antibiogram, the true 2005 prevalence was 25% among skin infections. When asked to select empiric therapy for a pediatric outpatient with a skin abscess, while assuming varying levels of MRSA prevalence, most selected cephalexin when the prevalence was assumed to be 20% or less, and trimethoprim-sulfamethoxazole when the prevalence was assumed to be 30% or greater. These data suggest that antibiograms may improve empiric therapy decision making by increasing knowledge of local outpatient prevalence of antibiotic resistance.

Methicillin-resistant Staphylococcus aureus--positive surgical site infections in face-lift surgery

OBJECTIVES

To determine the incidence of methicillin-resistant Staphylococcus aureus (MRSA)-positive surgical site infections after face-lift surgery and to discuss the screening, prevention, and treatment of such infections.

METHODS

The patient charts of 780 patients who underwent a deep-plane rhytidectomy between 2001 and 2007 were reviewed for postoperative wound infections. Culture results and sensitivities were recorded. To our knowledge, this is the first study that documents MRSA-positive surgical site infections after face-lift surgery.

RESULTS

Five of 780 patients (0.6%) who underwent face-lift surgery by the senior surgeon had postoperative surgical site infections. Four of the 5 patients had cultures that were positive for MRSA. Two of these patients (0.3%) required hospitalization and had collections that had to be opened or drained and developed wound breakdown. Both patients eventually responded to wound care along with intravenous and then oral antibiotic therapy. The other 2 MRSA-infected patients responded to oral antibiotic therapy and local wound care alone. The 2 complicated infections occurred on postoperative days 5 and 8. These 2 patients were the only ones among the 5 patients with positive cultures who had known recent contact with another physician or a hospital. All infections occurred in the year 2006, with 3 patients experiencing infection in the last 4 months of the year. Herein, we describe the incidence and sequelae of MRSA infections and colonization. The 2 major different subsets of MRSA are community-acquired MRSA and health care-associated MRSA. Surgical site infections that are positive for MRSA blur this division, which affects many aspects of the course of disease and treatment. We also discuss strategies for screening, preventing, and treating MRSA surgical site infections.

CONCLUSIONS

Methicillin-resistant S aureus-positive surgical site infection is an increasingly problematic issue in all surgical fields. In the future, MRSA-positive infections will be more prevalent and will require well-developed screening, prevention, and treatment strategies.

Biological activities of novel gyrase inhibitors of the aminocoumarin class

Thirty-one aminocoumarin antibiotics derived from mutasynthesis experiments were investigated for their biological activities. Their inhibitory activities toward Escherichia coli DNA gyrase were determined in two different in vitro assays: an ATPase assay and a DNA supercoiling assay. The assays gave a similar rank order of the activities of the compounds tested, although the absolute 50% inhibitory concentrations (IC(50)s) obtained in each assay were different. To confirm that the compounds also acted as gyrase inhibitors in vivo, reporter gene assays were carried out with E. coli by using gyrA and sulA promoter fusions with the luxCDABE operon. A strong induction of both promoters was observed for those compounds that showed gyrase inhibitory activity in the biochemical assays. Compounds carrying analogs of the prenylated benzoyl moiety (ring A) of clorobiocin that were structurally very different showed high levels of activity both in the biochemical assay and in the reporter gene assay, indicating that the structure of this moiety can be varied considerably without a loss of affinity for bacterial gyrase. The experimentally determined IC(50)s were compared to the binding energies calculated in silico, which indicated that a shift of the pyrrole carboxylic acid moiety from the O-3'' to the O-2'' position of the deoxysugar moiety has a significant impact on the binding mode of the compounds. The aminocoumarin compounds were also investigated for their MICs against different bacterial pathogens. Several compounds showed high levels of activity against staphylococci, including a methicillin-resistant Staphylococcus aureus strain. However, they showed only poor activities against gram-negative strains.

Macrolide and clindamycin resistance in Staphylococcus aureus isolates and antibiotic use in a Veterans Affairs Medical Center

A retrospective analysis of 13,946 Staphylococcus aureus isolates revealed a stable incidence of isolates that were resistant to both clindamycin and erythromycin, but a significantly increasing incidence of isolates that were susceptible to clindamycin and resistant to erythromycin during 1991-1995, 1996-2000, and 2001-2005. The use of macrolides and clindamycin also increased during 1996-2005. The incidence of S. aureus isolates with inducible clindamycin resistance increased steadily and significantly during the period from August 2004 through December 2005.

Practical management: community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA): the latest sports epidemic

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has gained international recognition as a superbug that causes serious infectious outbreaks in high-risk populations such as athletes. Clusters of cases in various athletic teams, particularly contact sports, have been reported since 1993 in the United States and more recently in Canada. CA-MRSA infections are not limited to North America, and all athletes are considered high risk. Skin-to-skin contact appears to be the primary mode of transmission. While typical infections are local skin and soft-tissue abscesses, CA-MRSA infections can spread systemically and lead to significant morbidity and mortality if not promptly identified and treated. The gold standard of treatment for all abscesses is incision and drainage with wound culture for bacterial identification and antibiotic sensitivity testing. A limited number of antibiotics are currently useful in the treatment of CA-MRSA and are reviewed. Geographical variation in patterns of antibiotic resistance further complicates the treatment. Meticulous, consistent use of infection prevention strategies is critical to control outbreaks in the athletic population. Good hygiene, prompt identification of infection, limited exposure to infected persons and contaminated objects, and proper treatment combined with close follow-up of infected athletes will help contain CA-MRSA outbreaks. Future research is needed to explore person-to-person and fomite transmission risks, to define the significance of nasal carriage and skin colonization in relation to CA-MRSA infections, and to further investigate antibiotic resistance patterns. Universal education is needed for all athletes and personnel who provide care in the athletic setting to help control this widespread epidemic.

Emergence of community-acquired methicillin-resistant Staphylococcus aureus soft tissue infections

PURPOSE

Our objective is to describe the changing incidence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) and its treatment within East Tennessee.

METHODS

A retrospective chart review of 245 patients treated with incision and drainage of soft tissue infections from March 2000 to September 2005 was completed. Consent was obtained from our local institutional review board. Forty patients were excluded because no cultures were recorded or because they failed the criteria for the diagnosis of CA-MRSA. We examined our data using chi2 analysis. P value of less than .05 was considered statistically significant.

RESULTS

The most common organism cultured was CA-MRSA (33%; 67 of 205). Non-CA-MRSA accounted for 4% (9 of 205). The age of patients ranged from 1 month to 21 years, with a mean age of 6.5 years. Stratified by year, the incidence of positive cultures for CA-MRSA has increased 159% since 2004 and 868% since 2003. In addition, the average age of patients has decreased from 8.3 years in 2000 to 6.1 years in 2005.

CONCLUSIONS

Community-acquired MRSA has emerged as the dominant source of soft tissue infection requiring incision and drainage regardless of site in East Tennessee. This has caused a change in the choice of empiric antibiotic treatment of soft tissue abscesses in our region. These infections now account for the third most common reportable disease to the Department of Health in East Tennessee.

Community-acquired methicillin-resistant Staphylococcus aureus skin infections: a review of epidemiology, clinical features, management, and prevention

Community-acquired methicillin-resistant Staphylococcus aureus (CAMRSA) infection is a global problem of epidemic proportions. Many of the patients who develop CAMRSA skin lesions do not have infection-associated risk factors. Abscess, abscess with accompanying cellulitis, and cellulitis are the most common presentations of cutaneous CAMRSA infection; occasionally, these CARMSA-related lesions are misinterpreted as spider or insect bites. Other manifestations of cutaneous CAMRSA infection include impetigo, folliculitis, and acute paronychia. The management of CAMRSA skin infection includes incision and drainage, systemic antimicrobial therapy, and adjuvant topical antibacterial treatment. In addition, at the initial visit, bacterial culture of the lesion should be considered. Direct skin-to-skin contact, damage to the skin surface, sharing of personal items, and a humid environment are potential mechanisms for the acquisition and transmission of cutaneous CAMRSA infection. Measures that strive to eliminate these causes are useful for preventing the spread of CAMRSA skin infection.

Epidemiology of methicillin-resistant Staphylococcus aureus at a pediatric healthcare system, 1991-2003

BACKGROUND

The emergence and epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) at a Minneapolis pediatric healthcare facility was investigated.

METHODS

Children with MRSA infections from January 1991 to December 2003 were classified as community-associated (CA) or healthcare-associated (HA) using established criteria. Isolates were subtyped using pulsed-field gel electrophoresis and grouped into pulsed-field types (PFTs). Case and isolate characteristics were compared and temporal trends were assessed.

RESULTS

The first isolate classified as CA-MRSA in this healthcare facility was identified in 1991. CA-MRSA cases (n = 188) were more likely than HA-MRSA cases (n = 83) to have a skin or soft tissue infection (80% versus 59%) and to belong to a racial or ethnic minority group (82% versus 55%), whereas HA-MRSA cases were younger (median age, 3.4 years versus 4.9 years). The proportion of both CA- and HA-MRSA isolates susceptible to clindamycin and erythromycin declined during the study period. Isolates classified as CA-MRSA were more likely than HA-MRSA isolates to be USA300 (21% versus 11%, P = 0.05) and USA400 (62% versus 31%, P < 0.001) PFTs. Associations between case race/ethnicity and isolate PFT were observed independent of case classification.

CONCLUSIONS

CA-MRSA is well established in this pediatric population. Although no discernable changes in CA- or HA-MRSA case characteristics were documented during the study period, significant changes were observed in CA-MRSA isolate characteristics, indicating that this pathogen continues to evolve.

Emerging Options for Treatment of Invasive, Multidrug-ResistantStaphylococcus aureusInfections

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

Regulatory disincentives for developing antibiotics for common indications

Pediatric and adult community-acquired respiratory tract infections remain some of the most common reasons for visits to primary care practitioners, and the antibiotics used to treat them are historically highly profitable for their manufacturers. Despite these facts and the continued evolving need for new treatments for these infections, virtually no new agents have been developed in the past decade. This review explores some regulatory guidelines that could potentially explain the dearth of development, and it provides some practical answers for resolving them.

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.

Isolation of Staphylococcus aureus and antibiotic-resistant Staphylococcus aureus from residential indoor bioaerosols

OBJECTIVE

In this study we evaluated the levels of Staphylococcus aureus and antibiotic-resistant S. aureus in colony-forming units (CFU) per cubic meter of air.

DESIGN

We used Andersen two-stage samplers to collect bioaerosol samples from 24 houses in El Paso, Texas, using tryptic soy agar as the collection media, followed by the replicate plate method on Chapman Stone selective medium to isolate S. aureus. The Kirby-Bauer disk diffusion method was used to determine antibiotic resistance to ampicillin, penicillin, and cefaclor, which represent two distinct classes of antibiotics.

RESULTS

The average recovered concentration of respirable heterotrophic organisms found outside each home was 345.38 CFU/m3, with an average of 12.63 CFU/m3 for S. aureus. The average recovered concentration of respirable heterotrophic organisms found inside each home was 460.23 CFU/m3, with an average of 15.39 CFU/m3 for S. aureus. The respirable S. aureus recovered from inside each home had an average resistance of 54.59% to ampicillin and 60.46% to penicillin. Presence of cefaclor-resistant and of multidrug-resistant S. aureus was the same, averaging 13.20% per house. The respirable S. aureus recovered from outside each home had an average resistance of 34.42% to ampicillin and 41.81% to penicillin. Presence of cefaclor-resistant and of multidrug-resistant S. aureus was the same, averaging 13.96% per house.

CONCLUSIONS

This study indicates that antibiotic-resistant bioaerosols are commonly found within residential homes. Our results also suggest that resistant strains of airborne culturable S. aureus are present in higher concentrations inside the study homes than outside the homes.

Community-acquired methicillin-resistant Staphylococcus aureus infections in children

Methicillin-resistant Staphylococcus aureus (MRSA) is now an established community pathogen in many areas of the United States as well as the world. Community-acquired MRSA (CA-MRSA) infections have changed several aspects of staphylococcal infections in children including the epidemiology, clinical manifestations, laboratory approach, antibiotic management, and prevention.

Children hospitalized with skin and soft tissue infections: a guide to antibacterial selection and treatment

Skin and soft tissue infections in children are an important cause for hospitalization. A thorough history and physical examination can provide clues to the pathogens involved. Collection of purulent discharge from lesions should be completed prior to initiating antimicrobial therapy, and results of bacteriologic studies (Gram stain and culture) should guide therapeutic decisions. The main pathogens involved in these infections are Staphylococcus aureus and group A beta-hemolytic streptococci, but enteric organisms also play a role especially in nosocomial infections. Increasing antibacterial resistance is becoming a major problem in the treatment of these infections worldwide. Specifically, the rise of methicillin-resistant S. aureus and glycopeptide-resistant S. aureus pose challenges for the future. Infections of the skin and soft tissues can be broadly classified based on the extent of tissue involvement. Superficial infections such as erysipelas, cellulitis, bullous impetigo, bite infections, and periorbital cellulitis may require hospitalization and parenteral antibacterials. Deeper infections such as orbital cellulitis, necrotizing fasciitis, and pyomyositis require surgical intervention as well as parenteral antibacterial therapy. Surgery plays a key role in the treatment of abscesses and for the debridement of necrotic tissue in deep infections. Intravenous immunoglobulin, as an adjunctive therapy, can be helpful in treating necrotizing fasciitis. For most infections an antistaphylococcal beta-lactam antibacterial is first-line therapy. Third-generation cephalosporins and beta-lactam/beta-lactamase inhibitor antibacterials as well as clindamycin or metronidazole are often required to provide broad-spectrum coverage for polymicrobial infections.Special populations, such as immunocompromised children, those with an allergy to penicillins, and those that acquire infections in hospitals, require specific antibacterial strategies. These usually involve broader antimicrobial coverage with increased Gram-negative (including antipseudomonal) and anerobic coverage. In patients with a true allergy to penicillins, clindamycin and vancomycin play an important role in treating Gram-positive infections. Newer antibacterial agents, such as linezolid and quinupristin/dalfopristin, are increasingly being studied in children for the treatment of skin and soft tissue infections. These agents hold promise for the future especially in the treatment of highly resistant, Gram-positive organisms such as methicillin-resistant S. aureus, vancomycin-resistant S. aureus, and vancomycin-resistant enterococci.

Update on the management of skin, soft-tissue, and osteoarticular infections in children

PURPOSE OF REVIEW

To provide an update on the diagnosis and management of skin, soft-tissue, and osteoarticular infections in children.

RECENT FINDINGS

Our understanding of the epidemiology of skin and soft-tissue infections and osteoarticular infections is changing rapidly. Community-associated methicillin-resistant Staphylococcus aureus has become a predominant cause of childhood skin and soft-tissue infections. Kingella kingae is also increasingly identified as a cause of osteoarticular infections. Challenges in Staphylococcus aureus treatment and Kingella kingae identification are changing the approach to skin and soft-tissue infections and osteoarticular infections.

SUMMARY

Community-associated methicillin-resistant Staphylococcus aureus should be considered a cause of skin and soft-tissue infections. Empiric antimicrobial choices should be modified in areas in which there is a more than 10% prevalence of community-associated methicillin-resistant Staphylococcus aureus infection. Decontamination of shared sports equipment should be undertaken to minimize person-to-person spread. No established guideline for eradication of carriage of community-associated methicillin-resistant Staphylococcus aureus exists. Kingella kingae is a more prevalent cause of osteoarticular infections than previously recognized and can cause outbreaks of invasive infection via person-to-person transmission. Modification of culturing procedures for osteoarticular infections including inoculation of infected joint fluid and bone in blood-culture bottles should be considered.

Ductus arteriosus aneurysm with community-acquired methicillin-resistant Staphylococcus aureus infection and spontaneous rupture: a potentially fatal quandary

We present the case of a 6-month-old previously healthy girl who presented with high fever, labored breathing, and an enlarged cardiac silhouette on her chest radiograph. Comprehensive evaluation discovered a ductus arteriosus aneurysm and pericardial effusion with methicillin-resistant Staphylococcus aureus bacteremia. Despite pericardiocentesis and appropriate intravenous antibiotics, there was rapid enlargement of the aneurysm and accumulation of echogenic material within the ductus arteriosus aneurysm. Infected aneurysm rupture was identified during emergency surgery. This infant also had vocal cord paresis, a likely complication of the surgery. The clinical course, diagnosis, and treatment of this patient are discussed. Infection of a ductus arteriosus or an infected ductal arteriosus aneurysm is a rare and potentially fatal clinical entity. In the era of increasing community-acquired methicillin-resistant S aureus infections, this is a diagnosis that requires a high index of suspicion.

Treatment of chronic rhinosinusitis exacerbations due to methicillin-resistant Staphylococcus aureus with mupirocin irrigations

INTRODUCTION

Chronic rhinosinusitis (CRS) exacerbations due to methicillin-resistant Staphylococcus aureus (MRSA) are routinely encountered. Treatment often involves intravenous antibiotics that provide only transient benefits. Mupirocin has well-recognized antistaphylococcal activity, and its nasal formulation is approved by the Food and Drug Administration for the eradication of nasal colonization with MRSA.

OBJECTIVE

The aim of this study was to describe the use of mupirocin nasal irrigations for the treatment of CRS exacerbations due to MRSA.

MATERIALS AND METHODS

Charts of patients who received mupirocin nasal irrigations for MRSA exacerbations of CRS between January 2000 and October 2003 were reviewed.

RESULTS

Forty-two MRSA-positive cultures were obtained from 24 patients (mean age, 61 years; range, 38-82 years; 15 women and 6 men). Twenty-eight episodes were treated with mupirocin nasal irrigations and doxycycline; 4 were treated with mupirocin nasal irrigations and trimethoprim-sulfamethoxazole, and 7 episodes were treated with mupirocin nasal irrigations alone. Patients were reevaluated at approximately 4 to 6 weeks. Repeat cultures were not obtained in 12 patients (because of clinical and endoscopic resolution). Adequate follow-up was unavailable for 3 patients, and of the 27 repeat cultures, only 1 grew MRSA. Twelve patients had at least one recurrence, with a mean number of episodes of 1.75 (range, 1-8 episodes). The mean follow-up was 11.8 months (range, 3-27 months).

CONCLUSIONS

Mupirocin nasal irrigations may avoid the need for intravenous antibiotics, which often provide temporary benefits and entail greater cost and morbidity. Thus, mupirocin nasal irrigations may provide a relatively simple means for the management of MRSA exacerbations of CRS.

Staphylococcal skin infections in children: rational drug therapy recommendations

Staphylococcus aureus remains one of the most common and troublesome of bacteria causing disease in humans, despite the development of effective antibacterials and improvement in hygiene. The organism is responsible for over 70% of all skin and soft tissue infections in children and accounts for up to one-fifth of all visits to pediatric clinics. Skin and soft tissue infections that are predominantly caused by S. aureus include bullous and non-bullous impetigo, folliculitis, furunculosis, carbunculosis, cellulitis, surgical and traumatic wound infections, mastitis, and neonatal omphalitis. Other skin and soft tissue infections may also be caused by S. aureus but are often polymicrobial in origin and require special consideration. These include burns, decubitus ulcers (particularly in the perianal region), puncture wounds of the foot, as well as human and mammalian bites. Treatment of staphylococcal skin infections varies from topical antiseptics to prolonged intravenous antibacterials, depending on severity of the lesions and the health of the child. The treatment of choice for oral antibacterials remains the penicillinase-resistant penicillins such as flucloxacillin. Cefalexin and erythromycin are suitable cost-effective alternatives with broader cover, although care must be taken with the use of macrolides because of development of resistance to multiple families of antibacterials, particularly the lincosamides. Other cephalosporins such as cefadroxil and cefprozil are also effective, can be given once daily and have a better tolerability profile -- while azithromycin has a further advantage of a 3-day course. However, all of these agents are more expensive. Although the antibacterials have been given for 10 days in most clinical trials, there is no evidence that this duration is more effective than a 7-day course. In children requiring intravenous therapy, ceftriaxone has a major advantage over other antibacterials such as sulbactam/ampicillin and cefuroxime in that it can be given once daily and may, therefore, be suitable for outpatient treatment of moderate-to-severe skin infections. Newer-generation cephalosporins and loracarbef are also effective and have a broader spectrum of activity, but do not offer any added benefit and are significantly more expensive. Skin and soft tissue infections due to methicillin-resistant S. aureus (MRSA) are still relatively uncommon in children. Well children with community-acquired MRSA infections can be treated with clindamycin or trimethoprim-sulfamethoxazole (cotrimoxazole), but must be observed closely for potentially severe adverse effects. In severe infections, vancomycin remains the treatment of choice, while intravenous teicoplanin and clindamycin are suitable alternatives. Linezolid and quinupristin/dalfopristin are currently showing great promise for the treatment of multi-resistant Gram-positive infections. While the choice of antibacterial is important, supportive management, including removal of any infected foreign bodies, surgical drainage of walled-off lesions, and regular wound cleaning, play a vital role in ensuring cure.

Community-acquired methicillin-resistant Staphylococcus aureus, a new player in sports medicine

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has emerged as a major pathogen, with distinct clinical characteristics and target populations. It has a striking ability to infect the young and the healthy. Persons in crowded conditions are at risk, including athletes, military personnel, jail inmates, and children in daycare. Most CA-MRSA infections are composed of simple and complicated skin and soft tissue infections; invasive disease occurs in 6% to 10% of cases. CA-MRSA infections can be treated with trimethoprim-sulfamethoxazole, doxycycline, or clindamycin. For severe infections, vancomycin, daptomycin, quinupristin/dalfopristin, or linezolid can be used. Infection control should be an integral part of any CA-MRSA treatment program.

Epidural abscesses

Until recently epidural abscess was considered a rare, almost theoretical, complication of central nerve block, but anecdotal reports suggest that this is no longer the case. Thus a review of the risk factors, pathogenesis, clinical features and outcome of this condition is appropriate, the primary aim being to make recommendations on best anaesthetic practice to minimize the risk of this serious complication. A search of EMBASE(c), PUBMED(c) and MEDLINE(c) databases from 1966 to September 2004 was performed using several strategies, supplemented by reference list screening. Spontaneous epidural abscess is rare, accounting for 0.2-1.2 cases per 10,000 hospital admissions per year. Estimates of the incidence after central nerve block vary from 1:1,000 to 1:100,000. Risk factors (compromised immunity, spinal column disruption, source of infection) are present in the majority of patients, whether the condition is spontaneous or associated with central nerve block. Presentation is vague, fever and back pain usually preceding neurological deficit. Diagnosis requires a high index of suspicion and modern imaging techniques. Treatment involves early surgical drainage to prevent permanent deficit and high dose parenteral antibiotics chosen with bacteriological advice. Primary prevention depends on proper use of full aseptic precautions. Epidural abscess can be a catastrophic consequence of central nerve block. Early diagnosis will minimize permanent damage, but primary prevention should be the aim. There is a need for a large survey to indicate the true incidence to better inform the risk-benefit ratio for central nerve block.

Intranasal exposure to bacterial superantigens induces airway inflammation in HLA class II transgenic mice

Staphylococcus aureus is widely prevalent in the nasopharynges of healthy individuals (carriers) but can also cause serious infections. S. aureus can elaborate a variety of superantigen exotoxins in "carrier" or "pathogenic" states. Streptococcus pyogenes can also colonize the nasopharynx and elaborate superantigens. Unlike the acute effects of superantigen exotoxins absorbed through the gut or vaginal mucosa, little is known regarding the pathogenesis of superantigens entering through the intranasal route. In the current study, we evaluated the local and systemic effects of staphylococcal enterotoxin B (SEB) and streptococcal pyrogenic exotoxin A (SPEA) delivered through the intranasal route. Superantigens were administered intranasally on multiple occasions, and experimental animals were sacrificed on day 8 for experimental analyses. SEB-induced airway inflammation was more pronounced for HLA-DR3 transgenic mice than for BALB/c mice, consistent with bacterial superantigens binding more efficiently to human than murine major histocompatibility complex class II. The nature of the airway inflammation in HLA-DR3 mice was determined by the concentration of SEB applied intranasally. Low concentrations (20 ng) induced eosinophilic airway inflammation as well as eosinophil degranulation, whereas intranasal exposure to higher concentrations (2,000 ng) resulted in neutrophilic airway inflammation, permanent airway destruction, toxic shock, and mortality. SEB-induced eosinophilic inflammatory response was enhanced in signal transducer and activator of transcription (STAT)-4-deficient HLA-DQ8 transgenic mice with defective interleukin-12 signaling. Intranasal administration of SPEA induced airway inflammation and systemic immune activation in HLA-DQ8 transgenic mice. In conclusion, repeated chronic intranasal exposure to bacterial superantigens causes airway inflammation and systemic immune activation.