Evaluation of Staphylococcus aureus Nasal Carriage Screening before Vascular Surgery

INTRODUCTION: Staphylococcus aureus is the most important pathogen in the development of surgical site infections (SSI). Patients who carry S. aureus in the nose are at increased risk for the development of SSI in cardiothoracic and orthopedic surgery. In these populations it has been shown that the risk for SSI can be substantially reduced by eradicating S. aureus carriage. For vascular surgery the relation between nasal carriage and surgical site infections has not been clearly investigated. For this reason we performed this study to analyze the relation between S. aureus nasal carriage and SSI in our vascular surgery population. METHODS: A prospective cohort study was undertaken, including all patients undergoing vascular surgery between January first 2010 and December 31th 2010. Before surgery patients were screened for S. aureus nasal carriage using a PCR technique. The presence of SSI was recorded based on criteria of the CDC. RESULTS: Screening was performed in 224. Of those, 55 (24.5%) were positive, 159 (71.0%) were negative and 10 (4.5%) were inconclusive. In the screened vascular population 4 S. aureus SSI occurred in the 55 carriers compared with 6 in 159 non-carriers (p=0.24). A stratified analysis revealed a 10-fold increased risk in nasal carriers undergoing central reconstruction surgery (3 S. aureus SSI in 20 procedures versus 1 in 65 procedures in non-carriers, p=0.039). DISCUSSION: In patients undergoing central reconstruction surgery nasals carriers are at increased risk for the development of S. aureus SSI. These patients will probably benefit from perioperative treatment to eradicate nasal carriage

Nasal Colonization of Humans with Methicillin-Resistant Staphylococcus aureus (MRSA) CC398 with and without Exposure to Pigs

Background: Studies in several European countries and in North America revealed a frequent nasal colonization of livestock with MRSA CC398 and also in humans with direct professional exposure to colonized animals. The study presented here addresses the question of further transmission to non exposed humans. Methods: After selecting 47 farms with colonized pigs in different regions of Germany we sampled the nares of 113 humans working daily with pigs and of their 116 non exposed family members. The same was performed in 18 veterinarians attending pig farms and in 44 of their non exposed family members. For investigating transmission beyond families we samples the nares of 462 pupils attending a secondary school in a high density pig farming area. MRSA were detected by direct culture on selective agar. The isolates were typed by means of spa-sequence typing and classification of SCCmec elements. For attribution of spa sequence types to clonal lineages as defined by multi locus sequence typing we used the BURP algorithm. Antibiotic susceptibility testing was performed by microbroth dilution assay. Results: At the farms investigated 86% of humans exposed and only 4.3% of their family members were found to carry MRSA exhibiting spa-types corresponding to clonal complex CC398. Nasal colonization was also found in 45% of veterinarians caring for pig farms and in 9% of their non exposed family members. Multivariate analysis revealed that antibiotic usage prior to sampling beard no risk with respect to colonization. From 462 pupils only 3 were found colonized, all 3 were living on pig farms. Conclusion: These results indicate that so far the dissemination of MRSA CC398 to non exposed humans is infrequent and probably does not reach beyond familial communities

Persistence of Livestock Associated MRSA CC398 in Humans Is Dependent on Intensity of Animal Contact

INTRODUCTION: The presence of Livestock Associated MRSA (LA-MRSA) in humans is associated with intensity of animal contact. It is unknown whether the presence of LA-MRSA is a result of carriage or retention of MRSA-contaminated dust. We conducted a longitudinal study among 155 veal farmers in which repeated nasal and throat swabs were taken for MRSA detection. Periods with and without animal exposure were covered. METHODS: Randomly, 51 veal calf farms were visited from June-December 2008. Participants were asked to fill in questionnaires (n = 155) to identify potential risk factors for MRSA colonisation. Nasal and throat swabs were repeatedly taken from each participant for approximately 2 months. Swabs were analysed for MRSA and MSSA by selective bacteriological culturing. Spa-types of the isolates were identified and a ST398 specific PCR was performed. Data were analyzed using generalized estimation equations (GEE) to allow for correlated observations within individuals. RESULTS: Mean MRSA prevalence was 38% in farmers and 16% in family members. Presence of MRSA in farmers was strongly related to duration of animal contact and was strongly reduced in periods with absence of animal contact (-58%). Family members, especially children, were more often carriers when the farmer was a carrier (OR = 2,

Methicillin Resistant Staphylococcus aureus ST398 in Veal Calf Farming: Human MRSA Carriage Related with Animal Antimicrobial Usage and Farm Hygiene

Introduction Recently a specific MRSA sequence type, ST398, emerged in food production animals and farmers. Risk factors for carrying MRSA ST398 in both animals and humans have not been fully evaluated. In this cross-sectional study, we investigated factors associated with MRSA colonization in veal calves and humans working and living on these farms. Methods A sample of 102 veal calf farms were randomly selected and visited from March 2007–February 2008. Participating farmers were asked to fill in a questionnaire (n = 390) to identify potential risk factors. A nasal swab was taken from each participant. Furthermore, nasal swabs were taken from calves (n = 2151). Swabs were analysed for MRSA by selective enrichment and suspected colonies were confirmed as MRSA by using slide coagulase test and PCR for presence of the mecA-gene. Spa types were identified and a random selection of each spa type was tested with ST398 specific PCR. The Sequence Type of non ST398 strains was determined. Data were analyzed using logistic regression analysis. Results Human MRSA carriage was strongly associated with intensity of animal contact and with the number of MRSA positive animals on the farm. Calves were more often carrier when treated with antibiotics, while farm hygiene was associated with a lower prevalence of MRSA. Conclusion This is the first study showing direct associations between animal and human carriage of ST398. The direct associations between animal and human MRSA carriage and the association between MRSA and antimicrobial use in calves implicate prudent use of antibiotics in farm animals

Modeling methicillin-resistant Staphylococcus aureus in hospitals: Transmission dynamics, antibiotic usage and its history

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) is endemic in many hospital settings, posing substantial threats and economic burdens worldwide. METHODS: We propose mathematical models to investigate the transmission dynamics of MRSA and determine factors that influence the prevalence of MRSA infection when antibiotics are given to patients to treat or prevent infections with either MRSA itself or other bacterial pathogens. RESULTS: Our results suggest that: (i) MRSA always persists in the hospital when colonized and infected patients are admitted; (ii) the longer the duration of treatment of infected patients and the lower the probability of successful treatment will increase the prevalence of MRSA infection; (iii) the longer the duration of contamination of health care workers (HCWs) and the more their contacts with patients may increase the prevalence of MRSA infection; (iv) possible ways to control the prevalence of MRSA infection include treating patients with antibiotic history as quickly and efficiently as possible, screening and isolating colonized and infected patients at admission, and compliance with strict hand-washing rules by HCWs. CONCLUSION: Our modeling studies offer an approach to investigating MRSA infection in hospital settings and the impact of antibiotic history on the incidence of infection. Our findings suggest important influences on the prevalence of MRSA infection which may be useful in designing control policies

Dynamic of livestock-associated methicillin-resistant Staphylococcus aureus CC398 in pig farm households: a pilot study.

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