Microbiology of skin and soft tissue infections in the age of community-acquired methicillin-resistant Staphylococcus aureus

The objectives of this study were to determine the etiology of skin and soft-tissue infections (SSTIs) in a general population, and to describe patient characteristics, SSTI types, frequency of microbiologic testing, and the role of methicillin-resistant Staphylococcus aureus (MRSA) over time. Using electronic databases, we identified SSTI episodes and microbiologic testing among members of a large US health plan. Between 2006 and 2009, 648 699 SSTI episodes were identified, of which 23% had a specimen, of which 15% were blood. A pathogen was identified in 58% of SSTI cultures. S. aureus was the most common pathogen (80% of positive cultures). Half of S. aureus isolates were MRSA. Among cellulitis and abscess episodes with a positive blood culture, 21% were methicillin-sensitive S. aureus, 16% were MRSA, 21% were beta-hemolytic streptococci and 28% were Gram negative bacteria. Between 1998 and 2009, the percentage of SSTIs for which a culture was obtained increased from 11% to 24%. In SSTI episodes with a culture-confirmed pathogen, MRSA increased from 5% in 1998 to 9% in 2001 to 42% in 2005, decreasing to 37% in 2009. These data can inform the choice of antibiotics for treatment of SSTIs.     

Epidemiology and molecular characteristics of community-associated methicillin-resistant and methicillin-susceptible Staphylococcus aureus from skin/soft tissue infections in a children's hospital in Beijing,China

To evaluate the epidemiology and molecular features of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) and methicillin-sensitive S. aureus (MSSA) from children with skin and soft tissue infections (SSTIs) in Beijing, China, prospective community-acquired S. aureus SSTIs surveillance was conducted at the Beijing Children's Hospital, Beijing, China, for a 12-month period from August 1, 2008, to July 30, 2009. Susceptibility to 12 antimicrobials was determined by the agar dilution method. Genotypic characteristics of CA-MRSA isolates were tested by SCCmec typing, spa typing, and multilocus sequence typing. Panton–Valentine leukocidin gene was detected. Of 1104 cases, 31.8% (351) were community-acquired S. aureus. CA-MRSA accounted for 4% (14) of S. aureus. Among 14 CA-MRSA and 120 MSSA isolates tested, 100% and 91.7% were multidrug resistant, respectively. ST59-MRSA-IVa-t437 (42.9%) was the most common form of CA-MRSA. Spa typing analysis of 120 MSSA isolates was performed, followed by pulsed-field gel electrophoresis and multilocus sequence typing of a selected number of isolates. The most common spa types among MSSA were t084 (8.3%), t091 (5.8%), t034 (5%), t127 (4.2%), t002 (4.2%), and t796 (4.2%). No predominant spa type was seen. Of the MSSA isolates that could be classified into spa-CCs, 15.0% had a genetic background observed in CA-MRSA clones (spa-CC437, spa-CC342, and spa-CC377). Panton-Valentine Leukocidin (PVL)-positive community-acquired S. aureus strains were more commonly associated with skin abscesses than other SSTIs (29.4% versus 5.9%, P < 0.01).In conclusion, CA-MRSA infections are not common among Chinese children with SSTIs. Our findings show that MSSA strains in China have diverse genetic backgrounds.     

Characterization of ST80 Panton-Valentine leukocidin-positive community-acquired methicillin-resistant Staphylococcus aureus clone in Tunisia

The spread of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has been reported in communities worldwide. In this study, we characterized 64 Tunisian CA-MRSA by agr typing, polymerase chain reaction assay for 20 virulence genes, staphylococcal chromosomal cassette mec (SCCmec) typing, pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and protein A gene (spa) typing. All our isolates were lukS-PV-lukF-PV positive, etd positive, and edin positive. They harbored SCCmec type IV and belonged to agr group 3. PFGE typing showed that our isolates were distributed in 11 different pulsotypes. spa typing and MLST, performed with isolates representative of each PFGE pattern, revealed that all isolates had a unique spa type (t044) and a common sequence type (ST80). The isolates showed susceptibility to the majority of antibiotics, and resistance to kanamycin, erythromycin, and tetracycline, but intermediate resistance to fusidic acid. Full analysis of our results revealed that our isolates were nonmultiresistant and belonged to a single clonal type ST80.     

Change in the molecular epidemiology of methicillin-resistant Staphylococcus aureus bloodstream infections in Taiwan

A multiresistant community-associated methicillin-resistant Staphylococcus aureus clone (sequence type 59) established itself as a significant cause of nosocomial bloodstream infections soon after emergence in the communities. Multiresistance might be one of the characteristics that could have contributed to its quick adaptation to hospital environments.     

Antibiotic-associated diarrhea due to methicillin-resistant Staphylococcus aureus

Staphylococcus aureus has been implicated as a cause of antibiotic-associated diarrhea; however, reports rarely originate from the United States. We report 5 cases of antibiotic-associated diarrhea caused by methicillin-resistant S. aureus (MRSA). Eighty percent of the stool specimens were greenish. Heavy growth of MRSA from greenish stool culture may warrant oral vancomycin therapy.     

Diagnostic and therapeutic evaluation of community-acquired methicillin-resistant Staphylococcus Aureus (MRSA) skin and soft tissue infections in the emergency department

Background

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections commonly present as skin and soft-tissue infections (SSTIs). Treatment often includes incision and drainage with or without adjunctive antibiotics. Emergency department (ED) pharmacists wished to provide specific data to emergency physicians to better inform antibiotic choices for patients with SSTIs.

Study Objectives

The objectives of this study were to describe local susceptibility trends of CA-MRSA isolates obtained from patients with SSTIs and describe diagnostic and empiric therapeutic management of CA-MRSA SSTIs among ED health care providers at University of Utah Hospitals and Clinics.

Methods

Susceptibility of all unique CA-MRSA SSTI isolates for 2008 were identified and compiled into an antibiogram. ED providers evaluated their diagnostic and treatment habits using a self-assessment questionnaire, which was verified against charted information documented in the electronic medical records for patients presenting to the ED with a CA-MRSA SSTI.

Results

The ED antibiogram indicated that 57/58 (98%) CA-MRSA SSTI isolates were susceptible to sulfamethoxazole/trimethoprim (SMX/TMP); 50/58 (86%) isolates were susceptible to tetracycline, and 47/58 (81%) isolates were susceptible to clindamycin. Incision and drainage were performed in 23/25 (92%) patient cases, which was consistent with providers’ perceived habits (100%). SMX/TMP monotherapy was preferred among 23/35 (66%) providers, however, SMX/TMP combined with cephalexin was the antibiotic regimen prescribed in 9/22 (41%) patient cases.

Conclusions

Cephalexin was often added to cover for potential cellulitis due to Streptococcus spp., however, the surrounding erythema may simply be an extension of the CA-MRSA infection. Department-specific antibiograms are useful in guiding empiric antibiotic selection and may help providers judiciously prescribe antibiotics only when necessary.     

Risk factors and mortality of nosocomial infections of methicillin-resistant Staphylococcus aureus in an intensive care unit

Purpose

Methicillin-resistant Staphylococcus aureus (MRSA) infections are an increasing worldwide problem. We determined risk factors and predictors of mortality of MRSA nosocomial infections (NIs).

Materials and Methods

A prospective cohort study was performed in an adult mixed medical and surgical intensive care unit from 2003 to 2007. Stratified analyses and generalized linear modeling were used to assess risk factors and predictors of infection and mortality.

Results

A total of 184 infections (3.6% of all infections) were due to S aureus, and 97.8% of these were methicillin resistant. The most common infection sites were respiratory tract (35.6%) and bloodstream (30.6%). Stratified analyses of length of stay (LOS) before onset of MRSA NI and death indicated that MRSA infection (odds ratio [OR], 38.49; 95% confidence interval [CI], 25.53-58.09) and mortality (OR, 4.72; 95% CI, 1.92-11.99) were more likely for LOS more than 15 days than for LOS less than 7 days. After controlling for potentially confounding factors by use of generalized linear modeling analysis, we identified the following as independent risk factors: LOS before onset of MRSA infection (OR, 1.03; 95% CI, 0.01-1.04), serum creatinine (OR, 5.87; 95% CI, 1.37-9.21) level, use of mechanical ventilator (OR, 6.71; 95% CI, 1.58-8.5), and central venous catheter (OR, 1.13; 95% CI, 1.05-1.31).

Conclusions

Methicillin resistance is very common with S aureus infection. In our intensive care unit, use of invasive devices/procedures and LOS were the most important risk factors for infection.     

In vitro activity of daptomycin against Staphylococcus aureus and vancomycin-resistant Enterococcus faecium isolates associated with skin and soft tissue infections: first results from India

The in vitro activity of daptomycin and selected comparator agents against Staphylococcus aureus and vancomycin-resistant Enterococcus faecium (VREF) isolates recovered from hospitalized patients with skin and soft tissue infection's was evaluated by Clinical and Laboratory Standards Institute broth microdilution method. Daptomycin was the most active agent against both S. aureus (MIC₉₀, 1 μg/mL; 100% susceptible) and VREF (MIC₉₀, 4 μg/mL; 100% susceptible), making it an excellent therapeutic option.     

Development of the novel chromogenic screening medium for methicillin-resistant Staphylococcus aureus

MRSA-chrom, a novel chromogenic screening agar medium for methicillin-resistant Staphylococcus aureus (MRSA), was developed. There were all MRSA strains recovered in 24 h as a specific blue-colored colony among 130 microbes including 42 MRSA strains. MRSA-chrom showed the highest detection ratio among 4 commercially available selective media using 50 clinical specimens.     

Pathotype and susceptibility profile of a community-acquired methicillin-resistant Staphylococcus aureus strain responsible for a case of severe pneumonia

Recent articles have described an increasing number of infections due to Panton–Valentine leukocidin PVL-positive community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) worldwide. We report a case of necrotizing pneumonia successfully treated with levofloxacin in Italy, sustained by a PVL-positive CA-MRSA, belonging to ST88 and carrying a staphylococcal chromosomal cassette mec type V. Further molecular characterization of isolates revealed that they were PVL positive, belonged to the agr IV allele, possessed a capsular type 8, and had an almost complete pathotype composed of leukocidins and numerous adhesins. In addition, the strains were strong biofilm producers.     

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.     

Coexistence of mupirocin and antiseptic resistance in methicillin-resistant Staphylococcus aureus isolates from Korea

In this study, we determined the prevalence of mupirocin and antiseptics resistance in methicillin-resistant Staphylococcus aureus (MRSA) at a secondary- and a tertiary-care hospital in Korea. Mupirocin susceptibility test, ileS gene sequencing, and polymerase chain reaction for mupA, qacA/B, and smr gene were performed with 456 nonduplicated MRSA isolates collected from 2 hospitals in Korea. Genetic relatedness was determined by spa typing and multilocus sequence typing (MLST). The rates of low-level and high-level mupirocin resistance were 7% and 2% in the secondary-care hospital and 17% and 2% in the tertiary-care hospital, respectively. The positive rate of qacA/B and smr gene in mupirocin-resistant MRSA was 65% and 71%, respectively. In spa typing, most mupirocin-resistant MRSA showed genetic relatedness and some of the highly resistant isolates were ST239 and ST5 in MLST analysis. The distribution of low-level and high-level mupirocin resistance and the coexistence of antiseptic resistance in MRSA can result in failure of decolonization in Korea.     

Clinical,microbiologic, and genetic determinants of persistent methicillin-resistant Staphylococcus aureus bacteremia

Methicillin-resistant Staphylococcus aureus bacteremia (MRSAB) often persists despite full susceptibility to vancomycin; therefore, associated factors were assessed. A retrospective cohort analysis of 222 patients with MRSAB treated with vancomycin was conducted; patients with persistent MRSAB (pMRSAB) were compared to those with nonpersistent bacteremia (NPB). Incidence of pMRSAB was 9%. More patients with vancomycin MIC = 2 mg/L had pMRSAB (16%) compared to patients with vancomycin MIC <2 mg/L (5%), P = 0.012. SCCmec type and Panton–Valentine leukocidin production were similar between patients with pMRSAB and NPB. There was no difference in vancomycin troughs, time to first dose, or area under the concentration–time curve/MIC between groups. More metastatic complications were observed in pMRSAB 63% versus NPB 32% (P = 0.005). Multivariate analysis found endocarditis (odds ratio [OR], 2.3; P = 0.021), complicated MRSAB (OR, 2.6; P = 0.009), vancomycin MIC = 2 (OR, 2.6; P = 0.009), and septic shock (OR 2.2 P = 0.031), which were independent predictors of pMRSAB.     

Genetic characterization of Staphylococcus aureus isolates causing bloodstream infections in Austria

A total of 112 Staphylococcus aureus bloodstream isolates were genetically characterized. Spa typing and DNA microanalysis exhibited high diversity, resulting in 64 different spa types and 9 different SplitsTree clusters. Methicillin-resistant S. aureus (MRSA) were found in 6 cases only, including the first case of life-stock–associated MRSA (MRSA ST398) in bloodstream infection in Austria.     

Epidemiology and susceptibilities of methicillin-resistant Staphylococcus aureus in Taiwan: emphasis on chlorhexidine susceptibility

Chlorhexidine is an antiseptic agent used for hand hygiene worldwide. To evaluate the susceptibility of methicillin-resistant Staphylococcus aureus (MRSA) to chlorhexidine, this study determined MICs of chlorhexidine and another 12 antimicrobial agents, carriage of the Panton–Valentine leukocidin, qacA/B, and smr genes, genetic relatedness by multilocus sequence typing (MLST), and staphylococcal cassette chromosome mec element type for 206 MRSA clinical isolates from the Taiwan Surveillance of Antimicrobial Resistance program III and IV (years 2002 and 2004) from 26 hospitals. Using MLST, we respectively identified 102 (49.5%), 68 (33.0%), 13 (6.3%), 5 (2.4%), 5 (2.4%), and 13 (6.3%) isolates as ST239, ST59, ST5, ST241, ST573, and other types. The MIC₅₀ and MIC₉₀ of chlorhexidine for all 206 isolates were 2 and 8 μg/mL, respectively. Seventy-three (35.4%) isolates carried qacA/B gene, but none carried smr. For the 72 (35.0%) MRSA isolates with chlorhexidine MIC ≥4 μg/mL, 53 were ST239 (49 of them carried qacA gene), 12 were ST5 (all carried qacB gene), 5 were ST241 (4 carried qacA gene), 1 was ST338 (and carried qacA gene), and 1 was ST573 (and carried qacA gene). Compared with other sequence-type MRSA isolates, ST239 MRSA isolates were the most resistant to both chlorhexidine and other antimicrobial agents. Methicillin-resistant S. aureus strains with disinfectant resistance qacA/B genes are common in Taiwan. High frequency of qacA/B genes among specific sequence types (ST239, ST5, and ST241) resulted in low susceptibility to chlorhexidine. Periodic surveillance of antiseptic susceptibility among MRSA isolates is important for the control of nosocomial hospital-acquired infections.