Community-associated methicillin-resistant Staphylococcus aureus skin infections in a religious community

Neutrophil evasion strategies by Streptococcus pneumoniae and Staphylococcus aureus

Humans are well equipped to defend themselves against bacteria. The innate immune system employs diverse mechanisms to recognize, control and initiate a response that can destroy millions of different microbes. Microbes that evade the sophisticated innate immune system are able to escape detection and could become pathogens. The pathogens Streptococcus pneumoniae and Staphylococcus aureus are particularly successful due to the development of a wide variety of virulence strategies for bacterial pathogenesis and they invest significant efforts towards mechanisms that allow for neutrophil evasion. Neutrophils are a primary cellular defense and can rapidly kill invading microbes, which is an indispensable function for maintaining host health. This review compares the key features of Streptococcus pneumoniae and Staphylococcus aureus in epidemiology, with a specific focus on virulence mechanisms utilized to evade neutrophils in bacterial pathogenesis. It is important to understand the complex interactions between pathogenic bacteria and neutrophils so that we can disrupt the ability of pathogens to cause disease.

The Role Played by Contaminated Surfaces in the Transmission of Nosocomial Pathogens

Studies in the 1970s and 1980s suggested that environmental surface contamination played a negligible role in the endemic transmission of healthcare-associated infections. However, recent studies have demonstrated that several major nosocomial pathogens are shed by patients and contaminate hospital surfaces at concentrations sufficient for transmission, survive for extended periods, persist despite attempts to disinfect or remove them, and can be transferred to the hands of healthcare workers. Evidence is accumulating that contaminated surfaces make an important contribution to the epidemic and endemic transmission ofClostridium difficile,vancomycin-resistant enterococci, methicillin-resistantStaphylococcus aureus, Acinetobacter baumannii, Pseudomonas aeruginosa,and norovirus and that improved environmental decontamination contributes to the control of outbreaks. Efforts to improve environmental hygiene should include enhancing the efficacy of cleaning and disinfection and reducing the shedding of pathogens. Further high-quality studies are needed to clarify the role played by surfaces in nosocomial transmission and to determine the effectiveness of different interventions in reducing associated infection rates.

Lifestyle-Associated Risk Factors for Community-Acquired Methicillin-Resistant Staphylococcus aureus Carriage in the Netherlands: An Exploratory Hospital-Based Case-Control Study

BACKGROUND

Community-acquired MRSA (CA-MRSA) is rapidly increasing. Currently, it is unknown which reservoirs are involved. An exploratory hospital-based case-control study was performed in sixteen Dutch hospitals to identify risk factors for CA-MRSA carriage in patients not belonging to established risk groups.

METHODS

Cases were in- or outpatients from sixteen Dutch hospitals, colonised or infected with MRSA without healthcare- or livestock-associated risk factors for MRSA carriage. Control subjects were patients not carrying MRSA, and hospitalised on the same ward or visited the same outpatients' clinic as the case. The presence of potential risk factors for CA-MRSA carriage was determined using a standardised questionnaire.

RESULTS

Regular consumption of poultry (OR 2⋅40; 95% CI 1⋅08-5⋅33), cattle density per municipality (OR 1⋅30; 95% CI 1⋅00-1⋅70), and sharing of scuba diving equipment (OR 2⋅93 95% CI 1⋅19-7⋅21) were found to be independently associated with CA-MRSA carriage. CA-MRSA carriage was not related to being of foreign origin.

CONCLUSIONS

The observed association between the consumption of poultry and CA-MRSA carriage suggests that MRSA in the food chain may be a source for MRSA carriage in humans. Although sharing of scuba diving equipment was found to be associated with CA-MRSA carriage, the role played by skin abrasions in divers, the lack of decontamination of diving materials, or the favourable high salt content of sea water is currently unclear. The risk for MRSA MC398 carriage in areas with a high cattle density may be due to environmental contamination with MRSA MC398 or human-to-human transmission. Further studies are warranted to confirm our findings and to determine the absolute risks of MRSA acquisition associated with the factors identified.

Risk factors for community-associated Staphylococcus aureus skin infection in children of Maui

The prevalence of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infection, and Staphylococcus aureus (S. aureus) infection overall, has dramatically increased in the past 10 years. Children and Native Hawaiians and Pacific Islanders (NHPI) are disproportionately affected by CA-MRSA infection. The purpose of this case-control study was to identify risk factors for CA-S. aureus skin infections in children of Maui, Hawai'i, as a foundation for reducing the transmission of these infections. Survey data were obtained from patients in pediatric clinician offices over an 8-month period. NHPI participants were well-represented as 58% of cases and 54% of controls. Chi-square analysis and logistic regression were used to identify risk factors. Significant risk factors predictive of infection among all participants were (a) skin abrasions or wounds, (b) household contact, and (c) overweight or obesity. Risk factors predictive of infection among NHPI were (a) skin abrasions or wounds, (b) antibiotic use within 6 months, (c) overweight or obesity, and (d) a history of eczema or other skin disorder. The role of overweight or obesity in S. aureus skin infections among NHPI has not been identified in previous research and indicates a focus for additional education. Further research is needed to better understand the role of eczema, antibiotic use, overweight and obesity, and socio-cultural factors in these infections.

Neutrophils in innate host defense against Staphylococcus aureus infections

Staphylococcus aureus has been an important human pathogen throughout history and is currently a leading cause of bacterial infections worldwide. S. aureus has the unique ability to cause a continuum of diseases, ranging from minor skin infections to fatal necrotizing pneumonia. Moreover, the emergence of highly virulent, drug-resistant strains such as methicillin-resistant S. aureus in both healthcare and community settings is a major therapeutic concern. Neutrophils are the most prominent cellular component of the innate immune system and provide an essential primary defense against bacterial pathogens such as S. aureus. Neutrophils are rapidly recruited to sites of infection where they bind and ingest invading S. aureus, and this process triggers potent oxidative and non-oxidative antimicrobial killing mechanisms that serve to limit pathogen survival and dissemination. S. aureus has evolved numerous mechanisms to evade host defense strategies employed by neutrophils, including the ability to modulate normal neutrophil turnover, a process critical to the resolution of acute inflammation. Here we provide an overview of the role of neutrophils in host defense against bacterial pathogens and discuss strategies employed by S. aureus to circumvent neutrophil function.

Survival of environmental and clinical strains of methicillin-resistant Staphylococcus aureus [MRSA] in marine and fresh waters

Recent studies have found variable levels of methicillin-resistant Staphylococcus aureus [MRSA] in marine water from temperate and warmer climates suggesting that temperature may play a role in survival of MRSA in the environment. The aim of the study was to compare the survival of clinical and environmental MRSA and MSSA strains in fresh and marine water incubated at 13 °C and 20 °C over 14 days. Seven different MRSA strains and the MSSA ATCC 25923 were tested. Individual strains were diluted in sterile saline to a 0.5 McFarland standard (10(8) cfu/ml), serially diluted in duplicate to a final concentration of 10(5) cfu/ml in pooled filter-sterilized marine or fresh water and incubated at 13 °C or 20 °C in the dark. The results of this study found that temperature and salinity are important factors in MRSA and MSSA survival; the decay rate was ∼28% higher at 20 °C versus 13 °C and ∼34-44% higher in fresh water versus marine water. There was no statistical difference between environmental and clinical MRSA strain survival [P = 0.138]. The study found that MRSA/MSSA survival was significantly longer in marine water at 13 °C typical of the Pacific Northwest, which may have important implications for recreational beach visitors in colder climates.

Treatment of skin and soft tissue infections in the elderly: A review

BACKGROUND

Skin and soft tissue infections (SSTIs) have become the second most common type of infection among persons residing in long-term care facilities.

OBJECTIVE

The purpose of this article was to review the latest information on SSTIs among the elderly, including age-related changes, challenges, and treatment strategies in the era of emerging bacterial resistance.

METHODS

Relevant information was identified through a search of MEDLINE (1970-April 2010), International Pharmaceutical Abstracts (1970-April 2010), and Google Scholar using the terms skin and soft tissue infection, skin and skin structure infection, cellulitis, treatment guidelines, and elderly. Additional publications were found by searching the reference lists of the identified articles. Trials published since 1970 were selected for this review if they prospectively evaluated mostly adults (≥18 years of age), included >50 patients, and reported diagnostic criteria as well as clinical outcomes in patients treated for simple or complicated SSTIs.

RESULTS

Fifty-eight of 664 identified studies were selected and included in this review. A search of the literature did not identify any prospective clinical trials that were conducted exclusively in the elderly. Information on the treatment of SSTIs in the elderly was based solely on clinical studies that were conducted in adults in general. As recommended by the Infectious Diseases Society of America (IDSA) 2008 update, SSTIs should be suspected in elderly patients who have skin lesions and present with a decline in functional status, with or without fever. Patients who present with symptoms of systemic toxicity should be hospitalized for further evaluation. Current challenges in the management of SSTIs include the rapid emergence of community-acquired, methicillin-resistant Staphylococcus aureus (CA-MRSA), the emergence of macrolide-resistant streptococci within the past decade, and the lack of a reliable algorithm to differentiate potentially life-threatening SSTIs that require aggressive interventions and prompt hospitalization from those that can be managed in an outpatient setting. S aureus was the most common cause of SSTIs, being isolated in 42.8% (5015/11,723) of wounds, followed by streptococci. Common SSTIs in the elderly such as shingles, diabetic foot infections, infected pressure ulcers, and scabies, and their treatment were also discussed. Based on reviews of published trials, treatment of simple SSTIs generally consisted of administration of agents with activity against S aureus and Streptococcus species such as a penicillinase-resistant β-lactam, a first-generation cephalosporin, or clindamycin. Broadening of the antimicrobial spectrum to include gram-negative and anaerobic organisms should be implemented for complicated SSTIs such as diabetic foot infections and infected pressure ulcers. Local rates of MRSA, CA-MRSA, and macrolide-resistant streptococci should be considered when selecting empiric therapy.

CONCLUSIONS

A search of the literature did not identify any prospective clinical trials on the treatment of SSTIs in the elderly; therefore, it is recommended to follow treatment based on the current IDSA guidelines. More research and publications are needed to establish proper selection of antimicrobial agents, treatment strategies, and duration of therapy of SSTIs in the elderly population.

Prevalence of nasal Staphylococcus aureus carriage in the patients undergoing hemodialysis and evaluation of risk factors and laboratory parameters

BACKGROUND

In this study, we aimed to determine the nasal carriage rate of Staphylococcus aureus and risk factors in hemodialysis (HD) patients.

METHODS

One hundred eighty-four HD patients were evaluated. A second sample was taken from the subjects, the wipe samples of whom were isolated as S. aureus. And subjects whose second samples' results were the same were deemed as S. aureus carriers.

RESULTS

Fifty-two (28.3%) patients were identified as S. aureus carriers. In the control group, S. aureus carriage has been found out as 14.9% in 116 healthy subjects. The isolation rate of S. aureus has been found statistically significantly high in the age group of 41-61 years. But, methicillin-resistant S. aureus (MRSA) isolation ratio has been statistically high in the group over the age of 61 years. Sepsis history and gastrointestinal system disease development is closely related to bacterial isolation. MRSA isolation ratios have been found high in chronic lung disease patients, diabetic patients, patients with infection history, and patients with impaired general state of health. The carriage ratios have been found higher in the patients who are settled in urban areas, are subjected to dialysis for more than 10 years, and are hospitalized in the past year. However, the difference between the other groups is not statistically significant.

CONCLUSIONS

S. aureus carriage must be screened on regular intervals in HD patients. Nasal S. aureus carriage follow-up and treatment is a process that will protect patients from more severe clinical pictures.

Survival and transmission of community-associated methicillin-resistant Staphylococcus aureus from fomites

BACKGROUND

Transmission of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) from fomites appears to play an important role in CA-MRSA outbreaks. However, the amount and duration of transmissibility of MRSA have not been quantified.

METHODS

We assessed the survival and transmission of the CA-MRSA strain USA300-0114 from 9 fomites (razors, plastic toys, ceramic, soap, wood, vinyl, towels, bed sheets, and shoulder pads). Fomites were inoculated then briefly pressed onto sterile pigskin at 5 minutes; days 1, 2, 3, 7, and 10; and then weekly for 10 weeks. The experiment was repeated using 2 methicillin-susceptible S aureus (MSSA) and 3 health care-associated (HA) MRSA strains on select fomites.

RESULT

Bacteria could be transmitted to skin from all fomites except soap. Transmissibility decreased over time but more rapidly from porous (eg, towels) than nonporous (eg, vinyl) fomites (P = .0002), with some fomites showing transmissibility for more than 8 weeks after contamination. The CA-MRSA strain was transmissible longer than the HA-MRSA strains (P < .0001) and 1 MSSA strain.

CONCLUSION

CA-MRSA strains are transmissible from many fomites to skin with contaminated nonporous fomites exhibiting transmissibility many weeks after contamination. Transmissibility of HA-MRSA strains demonstrated attenuated transmissibility compared with CA-MRSA strains. Findings may have implications for CA-MRSA infection prevention.

Risk factors for community-associated methicillin-resistant Staphylococcus aureus cellulitis--and the value of recognition

OBJECTIVES

To identify the risk factors for community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) cellulitis.

METHODS

A review of risk factors for CA-MRSA skin and soft tissue infection in previously published literature was first performed. A retrospective cohort study was then conducted in a teaching ambulatory-care clinic of a tertiary medical center in Honolulu, Hawaii.

RESULTS

Of 137 cases with cellulitis diagnosed from January 2005 to December 2007, MRSA was recovered from 85 (62%) of patients who presented with either abscesses or skin ulcers. The recovery of MRSA was significantly associated with obesity (p=0.01), presence of abscesses (p=0.01), and lesions involving the head and neck (p=0.04). Independent risk factors by multivariate logistic regression analysis included the presence of abscesses [adjusted odds ratio (aOR) 2.72; 95% confidence interval (CI) 1.27-5.83; p=0.01] and obesity (aOR 2.33; 95%; CI 1.10-4.97; p%0.03). Patients with CA-MRSA were less likely to receive an appropriate antibiotic (p=0.04) and were more likely to require antibiotic change at evaluation in one week (p=0.04) compared with patients infected with non-MRSA bacteria.

CONCLUSIONS

The presence of abscesses and obesity were significantly associated with CA-MRSA cellulitis. Empiric therapy with antibiotics active against MRSA should be guided by these risk factors.

Community-acquired methicillin-resistant Staphylococcus aureus in surgically treated hand infections

PURPOSE

An increase in the incidence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections has been observed. The purpose of this study is to determine the change in proportion of surgically treated CA-MRSA hand infections over the last decade and to identify associated risk factors.

METHODS

A retrospective review was performed of all 159 hand infections treated in the operating room over an 11-year period (1997-2007). Mean age overall was 40 years, mean inpatient length of stay was 4.9 days, and 115 of the 159 patients were male. Examined data included known risk factors for MRSA, including human immunodeficiency virus infection, diabetes mellitus, intravenous drug use, incarceration, and homelessness.

RESULTS

Forty-eight patients had surgery for hand infections due to CA-MRSA. The yearly proportion of CA-MRSA increased over the study period, and the risk of having an MRSA infection was 41% higher with each progressive calendar year during the study period relative to the apparent incidence of non-MRSA hand infections. Other factors associated with CA-MRSA were intravenous drug use, felon-type infection, and prior hand infection. Multivariable logistic regression identified intravenous drug use as a significant, independent risk factor for CA-MRSA hand infection.

CONCLUSIONS

The proportion of surgically treated hand infections due to CA-MRSA has increased during the last decade. Intravenous drug use was the only independent risk factor for CA-MRSA infections treated in the operating room at our institution.

Prevalence of and risk factors for colonization by methicillin-resistant Staphylococcus aureus among adults in community settings in Taiwan

In order to determine the prevalence of methicillin (meticillin)-resistant Staphylococcus aureus (MRSA) colonization among adults in community settings in Taiwan and identify its risk factors, we conducted the present study. For a 3-month period, we enrolled all adults who attended mandatory health examinations at three medical centers and signed the informed consent. Nasal swabs were taken for the isolation of S. aureus. For each MRSA isolate, we performed multilocus sequence typing, identification of the staphylococcal cassette chromosome mec, tests for the presence of the Panton-Valentine leukocidin gene, and tests for drug susceptibilities. Risk factors for MRSA colonization were determined. The results indicated that the MRSA colonization rate among adults in the community settings in Taiwan was 3.8% (119/3,098). Most MRSA isolates belonged to sequence type 59 (84.0%). Independent risk factors for MRSA colonization included the presence of household members less than 7 years old (P < 0.0001) and the use of antibiotics within the past year (P = 0.0031). Smoking appeared to be protective against MRSA colonization (P < 0.0001).

Methicillin-resistant Staphylococcus aureus strain USA300: origin and epidemiology

Methicillin-resistant Staphylococcus aureus (MRSA) PFGE strain type USA300 (multilocus sequence type 8, clonal complex 8, staphylococcal cassette chromosome mec type IV) was first reported in the USA as a cause of skin and soft issue infection among college football players in Pennsylvania and among prisoners in Missouri in 2000. Over the next 5 years, USA300 became the predominant community-associated MRSA strain in the USA. It was the most common PFGE type recovered from skin and soft tissue infections in persons presenting to 11 emergency departments across the USA, and caused outbreaks in Native American populations, children in daycare centres, military recruits, prison inmates and among men who have sex with men. Although predominantly a cause of skin and soft issue infection, USA300 isolates also have been recovered from cases of invasive disease including bacteraemia, endocarditis, severe necrotizing pneumonia and osteomyelitis. Isolates of USA300 usually carry the genes encoding the Panton-Valentine leucocidin and the arginine catabolic mobile element, but rarely carry staphylococcal enterotoxin genes. USA300 isolates are becoming more resistant to antimicrobial agents, including erythromycin, levofloxacin, mupirocin and tetracycline, and have spread to Europe, South America and Australia. The emergence of the MRSA USA300 strain type represents a unique biological success story.

Staphylococcus aureus: a community pathogen

Staphylococcus aureus is a common human pathogen. S aureus infections most commonly clinically manifest as skin infections. There has been much interest in S aureus infections in the community over the past decade because of the rise of community-associated methicillin-resistant S aureus (CA-MRSA) infections, which have emerged globally over a relatively short period of time. In contrast to health care-associated methicillin resistant S aureus (HA-MRSA), circulating strains of CA-MRSA have characteristic pathogenesis, strain characteristics, epidemiology, and clinical manifestations that are distinct from HA-MRSA. In fact, CA-MRSA probably behaves more like community-associated methicillin-sensitive S aureus (MSSA). This article reviews current knowledge of the epidemiology and clinical manifestations of community-associated S aureus and CA-MRSA infections.

Multiclonal outbreak of methicillin-resistant Staphylococcus aureus infections on a collegiate football team

An outbreak of methicillin-resistant Staphylococcus aureus (MRSA) skin and soft tissue infections (SSTIs) occurred in a college football team in August 2006. Of 109 players on the team roster, 88 (81%) were interviewed during a cohort investigation. Twenty-five cases were identified, six of which were culture-confirmed. Available culture isolates were typed by pulsed-field gel electrophoresis (PFGE), which identified two different MRSA strains associated with the outbreak. Playing positions with the most physical contact (offensive linemen, defensive linemen, and tight ends) had the greatest risk of infection [risk ratio (RR) 5·1, 95% confidence interval (CI) 2·3–11·5. Other risk factors included recent skin trauma (RR 1·9, 95% CI 0·95–3·7), use of therapeutic hydrocollator packs (RR 2·5, 95% CI 1·1–5·7), and miscellaneous training equipment use (RR 2·1, 95% CI 1·1–4·1). The outbreak was successfully controlled through team education and implementation of improved infection-control practices and hygiene policies.

Using focus groups to revise an educational booklet for people living with methicillin-resistant Staphylococcus aureus (MRSA)

The incidence of methicillin-resistant staphylococcus aureus (MRSA) has grown in epidemic proportions; in many individuals, MRSA causes recurrent infections. MRSA infections can be transmitted from person to person through direct contact or contact with contaminated objects. Once confined to hospitalized individuals, MRSA is now seen in otherwise healthy individuals and congregate community settings. There is a demand for educational materials to guide MRSA patients in self-care, preventing recurrences, and reducing transmission. In 2004, Tacoma-Pierce County Health Department in Washington State led the effort to create an educational booklet for people with MRSA. Due to resource constraints, it was created without audience testing. In 2005, the revision of Living With MRSA involved audience testing using two focus groups comprising people living with MRSA and their families. This report describes the work of an interdisciplinary professional work group using focus groups to revise an educational booklet for people living with MRSA as patients, family members, and caregivers.