R2169 Persistent suppression of bacterial growth after exposure to high-frequency alternated current

S628 by the predominance of phenolic monoterpenes, carvacrol and or timol. These results suggest that phenolic compounds are responsible for the antigiardial activity and have potential for use as therapeutic agents against giardiasis. R2169 Persistent suppression of bacterial growth after exposure to high-frequency alternated current C. Cassanelli, S. Roveta, A. Marchese, E.A. Debbia (Genoa, IT) Background: The exposure of a bacterial suspension to the hight frequency alternated current (HFAC) damages the bacterial envelope and delayes cell division. In this study was verified if the HFAC generated by Endox® Endodontic System, an instrument used in endodontic treatment for disinfection of the root canal, produced a phenomenon similar to postantibiotic effect. Methods: P. aeruginosa and E. faecalis strains employed in this study were clinical isolated belonging to the collection of this Laboratory. A sample of 0.1 ml of a saline bacterial suspension (105 cell/mL) was exposed to HFAC (140 msec, 500 kHz, 1200 kV) for three times and then resuspended in 10 ml of Mueller–Hinton broth. A suspension not treated was employed as control. The suspensions were grown at 37ºC for 6−8 hours; plate counts were performed every 60 min. All experiments were repeated for five times. Results: A persistent suppression of bacterial growth of about 3 hours was observed in the two bacterial species after exposure to HFAC. In the control strains no growth suppression was noted. Conclusion: The present findings suggest that HFAC generated by Endox® Endodontic System produce a damage in the structure of bacterical cells membrane. This phenomen can be usefull to study the possible variations in the permeability of bacterial membranes and is probaly responsable of bactericidal effect of this instrument. R2170 Assessment of susceptibilities of a range of antibiotic-resistant clinical isolates to Aloe vera inner gel F.M. Habeeb, A.A. Dashti, D. Morrison, A.I. Gray, V.A. Ferro (Kuwait, KW; Glasgow, UK) Since the discovery of penicillin in 1928, by Alexander Fleming, the emergence of antibiotic resistant bacterial strains has been a growing problem. This has led to an urgent global call for new antimicrobial drugs, particularly from natural resources. We investigated the therapeutic potential of Aloe vera, a plant known anecdotally for its anti-microbial properties. Aloe vera, has widespread use in health and beauty products, toiletries and disinfectants, however, we wished to determine if there was a scientific basis for its anti-microbial usage and whether this could be exploited for use against antibiotic resistant bacteria. Objectives: To determine the effect of Aloe vera on a range of clinical isolates identified as antibiotic resistant, including Gram positive (Methicillin-Resistant Staphylococcus aureus, [MRSA] and Enterococcus bovis) and Gram negative (Enterobacter cloacae) strains. Methods: A standard broth tube dilution method, as recommended by NCCLS was used to calculate the minimum inhibitory concentrations (MIC) of a preservative free Aloe vera inner gel powder (Aloe vera of America, Inc). The MIC is read as the lowest concentration of antimicrobial agent, which inhibited bacterial growth. Minimal bactericidal concentrations (MBC) were determined by inoculating 10 microlitres from each MIC broth tube without visible growth, on a Nutrient agar plate. Plates were then incubated in an inverted position at 37ºC. Following overnight incubation, the plates were examined for colony growth. Lack of growth indicates that the tested drug was bactericidal at that dilution and this was reported as MBC. Growth indicates that the drug was bacteriostatic at that dilution. Results: The results showed that the MIC of Aloe vera on MRSA 9, MRSA 6, E. cloacae, and E. bovis was 25, 25, 25 and 12.5 mg/mL respectively. The MBC of Aloe vera on MRSA 9, MRSA 6, E. cloacae, and E. bovis was 62.5, 125, 62.5 and 125 mg/mL respectively.

17th ECCMID / 25th ICC, Abstracts accepted for publication only Conclusion: Aloe vera has antimicrobial activity and it could be used in healthcare settings. If a product contains 250 mg/mL of Aloe vera this will result in 10×MIC for MRSA 9, MRSA 6, E. cloacae, 20×MIC for E. bovis, 4×MBC for MRSA 9 and E. cloacae and 2×MBC for MRSA 6 and E. bovis. This indicates that Aloe vera is active against these clinical isolates and has the potential to be a source for new antimicrobials.

Epidemiology of MRSA, VRE & other Gram-positives R2171 Comparison of coagulase-positive and coagulase-negative variants of MRSA strains isolated from hospital specimens K. Kopron, S. Giedrys-Kalemba (Szczecin, PL) Objectives: The purpose of the study was to estimate biochemical characteristic, drug resistance and genotype patterns of coagulasepositive and coagulase-negative HA-MRSA isolated from the same hospital. Methods: A total of 258 MRSA strains were determined as aetiological agent of different kind of infections in Clinical Hospital in Szczecin in the year 1999–2005. Isolates were collected from various materials (blood, bronchoalveolar washings, sputum, secretion from wounds, catheters, drains, liquids from pleura and peritoneum) and wards (intensive care unit, surgery, internal medicine, urology, dermatology, cardiology). The plasma coagulase tube test, the slide test for clumping factor, thermonuclease test, API–STAPH kit, mecA and coa genes were used for identification. Susceptibility tests according to CLSI guidelines were preformed for cefoxitin, erythromycin, clindamycin, tetracycline, gentamicin, rifampicin, ciprofloxacin, cotrimoxazole, chloramphenicol, fusidic acid, vancomycin. All isolates were subjected to the SmaI genomic DNA macrorestriction analysis (PFGE) and the obtained patterns were compared by software Molecular Analyst Fingerprinting Software. Results: All coagulase-positive MRSA were positive in tests for thermonuclease but 19 isolates were CF negative (10%). HA-MRSA coagulase-negative strains were isolated from clinical specimens with a relatively high frequency – 29% (74 strains), mostly from intensive care unit – 52% (39 strains). All these strains were positive in tests for clumping factor and thermonuclease, most of them possess coa gen. The coagulase-positive HA-MRSA strains were more resistant to chloramphenicol and rifampicin than coagulase-negative, which were more resistant to cotrimoxazole; the level of resistance to other drugs was similar, about 90–100%. No vancomycin resistant HA-MRSA were found. HA-MRSA strains belonged to 13 genotypes (A-M), grouped 2−48 isolates, and 6 unique patterns. Coagulase-negative strains were identified in 3 types (C, F, G) only, however in those types coagulasepositive MRSA were also found. Conclusion: Coagulase-negative MRSA strains are becoming more and more important problem in hospital infections. They belong to multidrug resistant strains and to the same epidemic/endemic genotypes as coagulase-positive MRSA. More attention should be given in their identification in routine diagnostic – phenotypic and genotypic methods are recommended. R2172 Antimicrobial resistance of Staphylococcus aureus nosocomial blood isolates in Russian intensive care units A. Dekhnich, E. Ryabkova, O. Kretchikova, N. Ivanchik (Smolensk, RU) Objectives: To evaluate the susceptibility of nosocomial strains of Staphylococcus aureus isolated from blood of patients hospitalised in ICUs in different parts Russia. Methods: A total of 143 strains of S. aureus isolated in 2004–2005 from patients with bacteraemia hospitalised in ICUs in 16 cities in different parts of Russia, were studied. Antimicrobials tested included chloramphenicol (CHL), ciprofloxacin (CIP), clindamycin (CLI), cotrimoxazole (CTX), erythromycin (ERY), fusidic acid (FUS), gentamicin