In vitro activity of tigecycline against methicillin-resistant Staphylococcus aureus, including livestock-associated strains

The in vitro activity of tigecycline was determined using a well-defined collection of methicillin-resistant Staphylococcus aureus (MRSA) isolates (n = 202), including 33 livestock-associated strains. Susceptibility testing was performed using the Etest system. Among the 202 MRSA strains, three (1.5%) had a minimum inhibitory concentration (MIC) value for tigecycline greater than 0.5 mg/l, which are considered to be resistant. When these strains were tested using Iso-Sensitest medium, the MICs were substantially lower and no resistance was found. This discrepancy warrants further investigations into the preferred test conditions for tigecycline. In conclusion, tigecycline showed good activity against MRSA strains in vitro

Comparison of fingerprinting methods for typing methicillin-resistant Staphylococcus aureus sequence type 398

This study evaluates the multiple-locus variable-number tandem-repeat assay (MLVA) and pulsed-field gel electrophoresis (PFGE) when using restriction enzymes BstZI, SacII, and ApaI to fingerprint a diverse collection of methicillin (meticillin)-resistant Staphylococcus aureus (MRSA) sequence type 398 (ST398) isolates. These isolates had been characterized previously by multilocus sequence typing, spa typing, and staphylococcal cassette chromosome mec (SCCmec) typing. Typeability and discriminatory power were analyzed, and the concordance between the various methods was determined. All MRSA ST398 isolates were typeable by the MLVA and PFGE using BstZI, SacII, and ApaI. With each method, the MRSA ST398 isolates formed a separate group from the two non-ST398 MRSA strains. PFGE, performed with any of the three restriction enzymes, had the most discriminatory power, followed by MLVA, spa typing, and SCCmec typing. The MLVA showed the highest concordance with PFGE using ApaI and spa typing. As further expressed by the Wallace coefficient, the MLVA type was poorly predicted by spa typing, whereas the spa type was well predicted by MLVA. PFGE, using a combination of all three restriction enzymes, had the highest concordance with the MLVA but had a low probability of being predicted by MLVA. PFGE, using a combination of all three restriction enzymes, was able to predict SCCmec type and MLVA type completely and had a high probability of predicting spa type. Both the MLVA and PFGE could be used to discriminate among the MRSA ST398 isolates. Although the MLVA is a faster technique, PFGE had more discriminatory power than the MLVA, especially when a combination of restriction enzymes was used

Infection and colonization with methicillin resistant Staphylococcus aureus ST398 versus other MRSA in an area with a high density of pig farms.

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Multiple Cases of Familial Transmission of Community-Acquired Methicillin-Resistant Staphylococcus aureus

The worldwide emergence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) can have severe public health implications. Familial transmissions of CA-MRSA in The Netherlands were investigated. Among the families studied, two clusters of CA-MRSA could be identified. This report demonstrates that family members can serve as reservoirs of CA-MRSA which may become a serious problem in containing the spread of MRSA

High prevalence of methicillin resistant Staphylococcus aureus in pigs. Vet. Microbiol

Abstract Recently methicillin resistant Staphylococcus aureus (MRSA) was isolated from pigs and pig farmers in The Netherlands. In order to assess the dissemination of MRSA in the Dutch pig population, we screened 540 pigs in 9 slaughterhouses, where a representative portion of Dutch pigs (63%) was slaughtered in 2005. We found 209 (39%) of the pigs to carry MRSA in their nares. Forty-four of 54 groups of 10 consecutive pigs (81%), each group from a different farm, and all slaughterhouses were affected. All MRSA isolates belonged to 1 clonal group, showing Multi-Locus Sequence Type 398 and closely related spa types (mainly t011, t108 and t1254). Three types of the Staphylococcal Chromosome Cassette (SCCmec) were found: III (3%), IVa (39%) and V (57%). All 44 tested isolates (1 isolate per group) were resistant to tetracycline, reflecting the high and predominant use of tetracyclines in pig husbandry. Twenty-three percent of the isolates were resistant to both erythromycin and clindamycin and 36% to kanamycin, gentamicin and tobramycin but only a single isolate was resistant to co-trimoxazole and none to ciprofloxacin and several other antibiotics. The percentage of MRSA positive pigs was significantly different among slaughterhouses and among groups within slaughterhouses, indicating a high prevalence of MRSA in pigs delivered from the farms as well as cross contamination in the slaughterhouses.

Methicillin-resistant Staphylococcus aureus in people living and working in pig farms

We compared the prevalence of human and animal methicillin-resistant Staphylococcus aureus (MRSA) at pig farms in The Netherlands, and related this to individual and farm-level characteristics. More than half of the farms investigated (28/50) had MRSA in pigs or stable dust and about one third (15/50) of person(s) were identified as MRSA carriers. Human carriage was found only on farms with M RSA-positive pigs or dust. MRSA strains in human samples were the same spa-type as found in pigs and all were not typable by pulsed-field gel electrophoresis (NT-MRSA). Multivariate analyses showed that risk factors for human MRSA carriage were: working in pig stables (OR 40, 95% CI 8-209) and the presence of sows and finishing pigs (OR 9, 95% CI 3-30). Veterinary sample collectors sampling the pigs showed transient MRSA carriage only during the day of the farm visit. Working in pig stables with MRSA-positive pigs poses a high risk for acquiring MRSA, increasingly so when contact with live pigs is more intensive or long lastin