14th ICID - Poster Abstracts - International Society for Infectious ...

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When citing these abstracts please use the following reference: Author(s) of abstract. Title of abstract [abstract]. Int J Infect Dis 2010;14S1: Abstract number. Please note that the official publication of the International Journal of Infectious Diseases 2010, Volume 14, Supplement 1 is available electronically on http://www.sciencedirect.com Final Abstract Number: 74.018 Session: Antibiotic Resistance: Gram-Positive Date: Friday, March 12, 2010 Time: 12:30-13:30 Room: Poster & Exhibition Area/Ground Level Type: Poster Presentation Real time PCR resolution of community acquired MRSA reservoirs: A strategy for the reduction of time to detection of hospital acquired MRSA S. Connolly, S. N. Connolly, Y. Pasari Teesside University, Middlesbrough, United Kingdom Background: Community acquired methicillin resistant Staphylococcus aureus (CA-MRSA) are infiltrating hospitals and becoming the dominant colonising strains. While the optimal MRSA detection strategy remains debatable reliance on conventional microbiological methods causes delay in identifying MRSA carriers culminating in cross infection and dissemination of hospital acquired MRSA infection. Methods: Nasal swab specimens were subjected to routine culture based and selective chromogenic screening, antibiotic susceptibility testing, as well as molecular detection using standard PCR and SYBR Green real-time PCR assays. MRSA was identified through the amplification of staphylococcal 16S rRNA, mecA and PVL genes. Results: Time to detection was within 5 hours of admission using the real-time method versus 2 days for standard PCR and 4 days for microbiological methods. All hospital acquired MRSA strains carried the mecA gene and showed multiple resistance to a panel of antibiotics. The community source of the existing hospital strains was established through amplification of the PVL gene, identified both singularly and in multiplex PCR assays with mecA, demonstrating that HA-MRSA originated through the dissemination of CA-MRSA by cross infection of the carriers. PVL positive multiply resistant MRSA strains were identified from nasal specimens of healthy individuals who had not recently visited hospitals, while healthy MRSA carriers from care home facilities did not contain the PVL gene and these strains demonstrated sensitivity towards most antibiotics. Conclusion: Thus, MRSA strains with specialised PVL-encoded virulence determinants persist in the hospital environment. This is in contrast to care home facilities where, in the absence of the selective pressure of antibiotics, low level resistance and PVL negative CA-MRSA strains are selected, whereas dominance of the more virulent PVL positive MRSA is curtailed. PCR assays, particularly SYBR Green real-time PCR, of mecA and PVL genes are preferential procedures in contrast to conventional methods for the rapid detection of CA-MRSA as a means of control of cross infection and the dissemination of HA-MRSA
When citing these abstracts please use the following reference: Author(s) of abstract. Title of abstract [abstract]. Int J Infect Dis 2010;14S1: Abstract number. Please note that the official publication of the International Journal of Infectious Diseases 2010, Volume 14, Supplement 1 is available electronically on http://www.sciencedirect.com Final Abstract Number: 74.019 Session: Antibiotic Resistance: Gram-Positive Date: Friday, March 12, 2010 Time: 12:30-13:30 Room: Poster & Exhibition Area/Ground Level Type: Poster Presentation Study of Vancomycin (VA) and Trimethoprim/sulfamethoxazole (TMP-SMX) activity on community-associated Methicillin Resistant Staphylococcus aureus (CA-MRSA) biofilms (Bf) in vitro A. Farinati 1 , M. V. Campana 1 , S. C. Lopez 1 , R. Notario 2 , J. M. Casellas 3 , G. Vazquez 1 1 Facultad de Medicina, Universidad del Salvador, Buenos Aires, Argentina, 2 Laboratorio CIBIC, Rosario, Santa FE, Argentina, 3 Laboratorio CIBIC , Rosario, Santa Fe, Argentina Background: Empirical CA-MRSA treatment could be affected by Bf development.There is an increasing appreciation that planktonic microbes account for only a very small proportion of microbial life, the bulk are found in a sessile form in Bf. Therefore, we study the influence of VA and TMP-SMX in early Bf development. Methods: To better elucidate this, we work with 6 CA-MRSA. We employ the MIC (1.5 mg/l-0.125 mg/l) and sub-MIC (0.5 mg/l-0.06 mg/l) of VA and TMP-SMX respectively. As control we use one HA-MRSA with similar VA MIC and sub-MIC but with 20 mg/l (MIC) and10 mg/l (sub-MIC) to TMP-SMX. Aliquots of overnight cultures in tryticase soy broth were incubated with glass coupons during 3 h for cell attachement. Coupons were transferred to fresh media with and without corresponding antibiotic (AM) concentrations, incubated for 24 h and evaluation previous staining with cristal violet Results: Visual observations revealed that CA-MRSA isolates are less effective to form Bf than HA-MRSA. Both AMs (MIC and sub-MIC) didn´t affect CA-MRSA but affected in different degrees HA-MRSA Bf development. Microscopically CA-MRSA with both AM produced more extracellular polymeric substances (EPS) than CA-MRSA without AM and similar to HA-MRSA with or without AM. Microcolonies structures were similar in all glass coupons for all isolates. The results showed that the presence of both AM seems not to affect early CA-MRSA Bf formation and there was an increase of EPS production. Recent reports showed a relationship between VA MIC and failure among patients with MRSA bacteremia treated with VA, atributing this failure to > 1.5 mg/l MIC. Conclusion: Our experiment might explain controversies about effectiveness of AM treatment due to Bf formation rather than presence of planktonic CA-MRSA in the patients. It is necessary to use or add other AM with activity in early stage of Bf different of VA or TMP-SMX in patients with suspected or established CA-MRSA infections.
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