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: 74.012 Session: Antibiotic Resistance: Gram-Positive Date: Friday, March 12, 2010 Time: 12:30-13:30 Room: Poster & Exhibition Area/Ground Level Type: Poster Presentation Emergence of linezolid-resistant coagulase-negative staphylococci in an Intensive Care Unit O. Zarkotou 1 , G. Chrysos 1 , E. Magira 1 , G. Altouvas 1 , A. Prekates 1 , K. Digalaki 1 , A. Tsakris 2 1 Tzaneio General Hospital of Piraeus, Athens, Greece, 2 University of Athens, Medical School, Athens, Greece Background: Linezolid resistance is rare among coagulase-negative staphylococci (CoNS). Such isolates have been firstly detected in our institution at November 2008. Despite perceived low virulence of CoNS, infection in critically ill patients is of potential concern. We performed an epidemiological and laboratory investigation to assess this finding. Methods: For a 12-month period (November 2008-October 2009), we evaluated all patients harboring linezolid-resistant (LZ-R) CoNS clinical isolates. Clinical and laboratory records were reviewed. Species identification and MIC values determination were performed by Vitek 2 Compact (bioMerieux) and/or Etest (AB Biodisk). Environmental and staff screening was carried out as part of the investigation. Results: During the study period, 24 patients (16 males, mean age 45.9±20.4 years) harboring LZ-R CoNS were identified. A total of 46 LZ-R CoNS clinical isolates were recovered. The majority of them (41/46) were isolated from blood cultures, while the remaining 5 isolates recovered from central venous catheter (CVC) tips. Staphylococcus epidermidis was the predominant species (38/46). Linezolid MICs were >256 μg/ml for 43/46 isolates. All isolates were methicillin-resistant and glycopeptides- and daptomycin-susceptible. The mean time from admission to LZ-R CoNS isolation was 28±15.9 days. Records of patients showed that 7/24 had >2 comorbidities, 9/24 had prior hospitalizations and 9/24 had foreign materials placed. At index positive culture for LZ-R CoNS, all patients had CVCs, had received prolonged broad-spectrum antibiotic therapy and 16/24 were mechanically ventilated. Prior administration of linezolid with mean duration 11.2±7.5 days was noted for 21/24 patients. Overall in-hospital mortality was 25%. There was no attributed death. Most infections were treated with teicoplanin. Only 1/58 environmental samples grew LZ-R S. epidermidis. Screening of ICU-personnel was negative for LZ-R CoNS carriage. Strict infection control measures were established in order to restrain further dissemination of LZ-R strains, without significant reduction of the number of new cases. Conclusion: Isolation of LZ-R CoNS, though rare, may be observed in critically ill patients after prolonged administration of linezolid. Intense infection control measures, continuous surveillance and judicious use of linezolid are essential for preserving its effectiveness. Further study is necessary in order to determine the clonal profile of these isolates.
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: 74.013 Session: Antibiotic Resistance: Gram-Positive Date: Friday, March 12, 2010 Time: 12:30-13:30 Room: Poster & Exhibition Area/Ground Level Type: Poster Presentation Inducible clindamycin-resistance in clinical staphylococcal isolates with reduced vancomycin susceptibility in a University Teaching Hospital B. Olayinka 1 , A. Olayinka 2 , A. Obajuluwa 1 , J. Onaolapo 1 , P. Olurinola 1 1 Ahmadu Bello University, Zaria, Nigeria, 2 Ahmadu Bello University Teaching Hospital, Shika- Zaria, Nigeria Background: The chemotherapy of staphylococcal infections has been complicated by evolution of multidrug resistant strains, especially the methicillin-resistant Staphylococcus aureus (MRSA) now treated with various groups of antimicrobial agents, including, the glycopeptides (vancomycin); and the macrolides, lincosamides and streptogramin B (MLSB) class of antibiotics. The risk of clinical failure during therapy is increasingly being reported while therapeutic failures due to MLSB-inducible resistance (MLSB-i) is becoming more frequent. The study determined prevalence of inducible erm-mediated clindamycin resistance (MLSB-i) in clinical staphylococcal isolates with reduced vancomycin susceptibility in a University Teaching Hospital was determined. Methods: Suspected staphylococcal isolates from specimen submitted to the Medical Microbiology laboratory were screened for vancomycin resistance on vancomycin-agar screening plates; Brain Heart agar supplemented with 6g/ml vancomycin (BHI-V6); Mannitol Salt agar supplemented with 4 g/ml vancomycin (MSA-V4) and confirmed by E-test. All isolates with vancomycin MIC of 1.5 to 2 were tested for MLSB-i by the double-disc diffusion, D-test using erythromycin (ER, 15g) and clindamycin (CL, 2 g) discs placed 15mm-18mm apart on Muller- Hinton agar plates inoculated with the test organism. Results: A total of 43/195 (22.1%) grew on BHI-V6 within 24hrs while 66/195 (33.8%) grew on MSA-V4 in 24-48hrs of incubation. However, only 36 isolates had vancomycin MIC of between 1.5 to 2.0. Only 41.6% (15/36) of the isolates gave a positive D-test indicative of MLSB-i. Conclusion: This is of clinical importance because MLSB-i S. aureus undergo spontaneous mutation to constitutive clindamycin resistance at high rate and with potential to develop resistance during treatment. Routine testing of staphylococcal isolates for inducible clindamycin resistance is recommended in the 2006 CLSI guidelines and help to chose treatment failures especially for patients infected with inducible MLSB isolates as in our hospital.
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