Characteristics of patients with healthcare-associated infection due to SCCmec type IV methicillin-resistant Staphylococcus aureus.
ABSTRACT Methicillin-resistant Staphylococcus aureus (MRSA) with the staphylococcal cassette chromosome mec (SCCmec) type IV allele is most commonly associated with community-acquired MRSA (CA-MRSA) infection; however, such organisms have also been identified in the healthcare setting. The objective of the present study was to characterize the epidemiology of and clinical outcomes associated with SCCmec-IV MRSA infection acquired in the healthcare setting, compared with infection caused by MRSA of other SCCmec types.
We evaluated a cohort of 100 inpatients with MRSA infection that met the Centers for Disease Control and Prevention definition for healthcare-associated infection and compared the patients' demographic characteristics, the antimicrobial susceptibilities of the MRSA isolates, the infection types, and the associated clinical and microbiological outcomes. For each MRSA isolate, the SCCmec type and the presence of Panton-Valentine leukocidin (PVL) were determined by polymerase chain reaction methods.
SCCmec-IV MRSA isolates were isolated from 53 patients (42% of these isolates were positive for PVL), and SCCmec-II or SCCmec-III MRSA was isolated from 47 patients (3% of these isolates were positive for PVL). No differences were noted between the patients in the SCCmec-II/III group and the patients in the SCCmec-IV group with respect to age (median, 55 vs 50 years); sex (77% vs 64% of patients were male); medical service (surgical service, 60% in both groups; ICU admission, 55% vs 53%), Acute Physiology and Chronic Health Evaluation II score (median, 8 vs. 7); infection type; or underlying comorbidities, except for presence of a burn wound (13% vs 2%; P < .04). Patients in the SCCmec-II/III group were more likely to have multiple sites of infection (P = .006) and a longer length of stay (LOS) prior to detection of MRSA than were patients in the SCCmec-IV group (median, 4 vs 1 days; P < .001). Total LOS was significantly greater for patients in the SCCmec-II/III, compared with those in the SCCmec-IV group (P = .006). Multiple logistic regression identified liver disease and longer LOS prior to detection of MRSA as predictors of infection with SCCmec-II/III MRSA. Rates of susceptibility to clindamycin, gentamicin, ciprofloxacin, levofloxacin, and tetracycline was significantly greater among SCCmec-IV MRSA isolates, compared with type II/III isolates (P < or = .05). Compared with SCCmec-IV isolates acquired in the community, the susceptibility rates among healthcare-associated SCCmec-IV isolates was significantly less for clindamycin, gentamicin, and levofloxacin, indicating that these organisms may quickly acquire resistance to non- beta -lactam antibiotics, as do SCCmec-II/III strains.
SCCmec-IV MRSA appears to have become established in hospitals. The onset of infection caused by SCCmec-IV strains is earlier than the onset of infection with SCCmec-II/III strains; however, associated types of infection are similar. Infection with SCCmec-II/III MRSA is currently associated with an adverse impact on outcome, compared with infection with SCCmec-IV MRSA. Further research is warranted to determine the impact of SCCmec type IV strains in hospital settings.
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ABSTRACT: Outdoor shallow wetland mesocosms, designed to simulate surface constructed wetlands to improve lagoon wastewater treatment, were used to assess the role of macrophytes in the dissipation of wastewater nutrients, selected pharmaceuticals, and antibiotic resistance genes (ARGs). Specifically, mesocosms were established with or without populations of Typha spp. (cattails), Myriophyllum sibiricum (northern water milfoil), and Utricularia vulgaris (bladderwort). Following macrophyte establishment, mesocosms were seeded with ARG-bearing organisms from a local wastewater lagoon, and treated with a single pulse of artificial municipal wastewater with or without carbamazepine, clofibric acid, fluoxetine, and naproxen (each at 7.6 μg/L), as well as sulfamethoxazole and sulfapyridine (each at 150 μg/L). Rates of pharmaceutical dissipation over 28 d ranged from 0.073 to 3.0 d− 1, corresponding to half-lives of 0.23 to 9.4 d. Based on calculated rate constants, observed dissipation rates were consistent with photodegradation driving clofibric acid, naproxen, sulfamethoxazole, and sulfapyridine removal, and with sorption also contributing to carbamazepine and fluoxetine loss. Of the seven gene determinants assayed, only two genes for both beta-lactam resistance (blaCTX and blaTEM) and sulfonamide resistance (sulI and sulII) were found in sufficient quantity for monitoring. Genes disappeared relatively rapidly from the water column, with half-lives ranging from 2.1 to 99 d. In contrast, detected gene levels did not change in the sediment, with the exception of sulI, which increased after 28 d in pharmaceutical-treated systems. These shallow wetland mesocosms were able to dissipate wastewater contaminants rapidly. However, no significant enhancement in removal of nutrients or pharmaceuticals was observed in mesocosms with extensive aquatic plant communities. This was likely due to three factors: first, use of naïve systems with an unchallenged capacity for nutrient assimilation and contaminant removal; second, nutrient sequestration by ubiquitous filamentous algae; and third, dominance of photolytic processes in the removal of pharmaceuticals, which overshadowed putative plant-related processes.Science of The Total Environment 06/2014; s 482–483:294–304. · 3.16 Impact Factor
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ABSTRACT: Staphylococcus aureus is a leading cause of hospital-(HA) and the community-acquired (CA) infections worldwide. Recently, S. aureus strains resistant to methicillin (MRSA) have become established within both communities. We isolated 314 isolates of MRSA from hospitalized patients in a referral hospital (HA isolates) and its outpatient clinic (n=268) (CA-isolates) in Tehran, Iran between February 2008 and December 2010. These isolates were tested for their susceptibility to 17 antibiotics and typed using the PhPlate system. The diversity in the structure of SCCmec elements and ccr types were also detected using a multiplex-PCR assay and isolates were examined for the presence of different classes of prophages. Whilst all isolates were resistant to penicillin, the HA-isolates were significantly more resistant to all other antibiotics tested than the CA-isolates. Isolates carrying only SCCmec type III and ccr type 3 were dominant (91%), but 20% of the CA-isolates belonging to less prevalent types, carried only SCCmec types IVa, c and ccr type 2. These isolates also carried pvl gene and contained SGA prophage type. Our results indicate that whilst the dominant clonal groups of HA- and CA-MRSA belong to SCCmec type III and carry ccr type 3 genes, several distinct but less prevalent types of CA-MRSA carrying SCCmec type IVa, c and type 2 ccr are also found in Tehran. These strains carry pvl genes and SGA prophage type, a characteristic that may be used as a marker for detection of CA-MRSA in this country.Journal of Medical Microbiology 03/2014; · 2.27 Impact Factor
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ABSTRACT: The Australian Group on Antimicrobial Resistance (AGAR) performs regular multicentre period prevalence studies to monitor changes in antimicrobial resistance. In 2011, 29 laboratories in Australia participated in the national surveillance of Staphylococcus aureus resistance. The survey only included unique isolates from clinical specimens collected ≥48 h after hospital admission. MRSA accounted for 30.3% of S. aureus isolates. MRSA resistance to ciprofloxacin, erythromycin, tetracycline, trimethoprim/sulfamethoxazole, gentamicin and clindamycin (constitutive resistance) varied considerably between regions. Resistance to non-β-lactam antimicrobials was uncommon in MSSA, with the exception of erythromycin. Regional variation in resistance was due to the differential distribution of MRSA clones between regions. The proportion of S. aureus genetically characterised as healthcare-associated MRSA (HA-MRSA) was significantly lower in this survey (18.2%) compared with the 2005 survey (24.2%) (P < 0.0001). Although four HA-MRSA clones were characterised, 98.8% of HA-MRSA were classified as either ST22-MRSA-IV [2B] (EMRSA-15) or ST239-MRSA-III [3A] (Aus-2/3 EMRSA). Multiclonal community-associated MRSA (CA-MRSA) increased markedly from 6.5% in 2005 to 11.7% of all S. aureus in 2011 (P < 0.0001). Although the proportion of MRSA resistant to non-β-lactam antimicrobials has decreased nationally, the proportion of S. aureus that are MRSA has remained stable. This is primarily due to non-multiresistant CA-MRSA becoming more common in Australian hospitals at the expense of the long-established multiresistant ST239-MRSA-III [3A] (Aus-2/3 EMRSA). Given hospital outbreaks of CA-MRSA are thought to be extremely rare, it is most likely that patients colonised at admission with CA-MRSA have become infected with the colonising strain during their hospital stay.Journal of Global Antimicrobial Resistance. 09/2013; 1(3):149–156.