Posters / International Journal of Antimicrobial Agents 42S2 (2013) S41–S159 S73 Objectives: To clarify the ratio of resistant isolates against various antimicrobials in C. koseri , we performed this study. Methods: We used total of 373 non-duplicate C. koseri isolated from various clinical specimen from 75 hospitals in western part of Japan in the period from 2008 to 2010. The MICs of various antimicrobials against the isolates were determined by the two-fold serial agar dilution method as described by the CLSI. The resistant isolates to antimicrobials were interpreted as showing more than following breakpoint MIC. Antimicrobials (their breakpoint MIC) used in this study as follows; ampicillin (8), piperacillin (8), piperacillin/ tazobactam (8/4), faropenem (2), cefazolin (8), cefotiam (8), cefmeta- zole (16), flomoxef (8), cefpodoxime (2), cefditoren (2), aztoreonam (8), imipenem (4), meropenem (4), levofloxacin (2), minocycline (4), gentamicin (4), tobramicin (4), amikacin (16), isepamicin (16), trimethoprim/sulfamethoxazole (2/38), and fosfomycin (64). Results: The susceptibility ratios of penicillins, faropenem, cephalo- sporins except ceftazidime and aztreonam against all 373 C. koseri isolates were less than 50%. The susceptibility ratios of piperacillin/ tazobactam, ceftazidime, cefmetazole, and flomoxef were 52.5, 52.8, 53.1, and 85.3, respectively. Imipenem and meropenem inhibited the growth of all 373 C. koseri isolates at 2 and 4 mcg/ml. The ratios of levofloxacin, minocycline, fosfomycin, and trimetho- prim/sulfamethoxazole were 33.8, 39.9, 98.9, and 63.5%. Concerning aminoglycosides, the susceptibility ratios of tobramycin, gentamicin, amikacin, and isepamicin were 76.9, 81.2, 97.9, 98.4%. Six of all 373 isolates showed high aminoglycoside-resistance; the MIC of all aminoglycosides used were more than 128 mcg/ml. Twenty-five of all 373 isolates showed resistance against all antimicrobials except carbapenems, amikacin, tobramycin, and fosfomycin. Conclusion: Most of C. koseri isolates have acquired beta-lactam resistance. The major factors of mechanisms of resistance were plasmid-mediated beta-lactamases, such as CTX-M-2, CTX-M-15, SHV-12, DHA-1, etc. About 7% of all isolates have acquired multi-drug resistance. P99 In vitro antimicrobial property of Rhodomyrtus tomentosa (Ait.) Hassk. against Streptococcus agalactiae isolated from cultured tilapia P. Na-Phatthalung 1 *, N. Suanyuk 2 , S.P. Voravuthikunchai 1 . 1 Department of Microbiology, 2 Department of Aquaculture, Prince of Songkla University, Songkhla, Thailand E-mail address : pinanong_np@hotmail.com Introduction: Streptocuccus agalactiae is an important fish pathogen in freshwater farms that resulted in a continuous decrease of tilapia production in aquaculture. Ethanol extract of Rhodomyrtus tomentosa leaf and its purified compound, rhodomyrtone has been previously demonstrated to possess a strong antibacterial activity against Gram- positive pathogens. Objectives: The purpose of this study was to investigate the in vitro antimicrobial activity of the Rhodomyrtus tomentosa extract on S. agalactiae isolated from tilapia during an outbreak in Southern, Thailand. Methods: Antimicrobial activity of the ethanol extract was performed using broth microdilutionmethod. Time-kill assay was also conducted to evaluate the bactericidal effect of the extract. Scanning electron microscope (SEM) was used to observe morphological changes of bacterial cells after exposure to the extract. In addition, the effect of an oxidative stress on bacterial cells after treatment with the extract was studied using hydrogen peroxide sensitivity assay. Results: Remarkable minimum inhibitory concentrations (MIC) of the Rhodomyrtus tomentosa extract against S. agalactiae (n = 10) were ranged from 31.25 to 62.5 mg/mL. The extract was demonstrated bac- teriostatic activity against a representative strain in time-kill studies. Additionally, SEM revealed an irregular shape, different size, and non- dividing of S. agalactiae cells after treated with sub-MIC (0.25×MIC) of Rhodomyrtus tomentosa extract. Interestingly, treatment with the extract at sub-MIC (0.125×MIC and 0.25×MIC) significantly increased sensitivity to hydrogen peroxide of exponential phase bacteria. Conclusion: These results suggested that Rhodomyrtus tomentosa is a promising candidate for a new antimicrobial agent against S. agalactiae which should be further study as an alternative for prevention and control of streptococcal infection in aquaculture. Using an antimicrobial agent base on natural source can reduce the residual levels of antibiotics in fish products and harmful effects to human health. Reference(s) Limsuwana S, et al . (2009) Phytomedicine. 16: 645–651. P100 Antibiotic susceptiblity pattern of Klebsiella pneumoniae from clinical samples at a tertiary hospital in Ile-Ife, South Western Nigeria A.O. Oladipo 1 *, S.J. Udoh 1 . 1 Medical Microbiology and Parasitology, Obafemi Awolowo University Teaching Hospitals Complex (OAUTHC), Ile-Ife, Nigeria E-mail address : beautifulworlds@yahoo.com Introduction: In the recent years, klebsiella pneumoniae has become important pathogen in nosocomial infections worldwide. All the isolates of klebsiella pneumoniae identified from January-December 2012 were subjected to antibiotic sensitivity testing on Mueller Hinton agar by modified Kirby–Bauer disc diffusion method using NCCLS guidelines. K. pneumoniae were most frequently isolated from urine 604 (42.5%), sputum 240 (29.9%) followed by blood 180 (42.9%), pus 86 (37.0%) and CSF with the least incidence of 34 (14.8%). All strains were resistant to antibiotics such as amoxycilin 64%, gentamicin 92.6%, erythromycin 82.3%, trimethoprim 88% sulfamethoxazole 96.3%, tetracycline 88.5%, ciprofloxacin 31.2%, nitrofurantoin 31.2%, ceftazidime 69%, cefotaxime 74%, ceftriaxone 79.6% while sensitivity to imipenem was 100% by all the organisms. This study suggested that there is a need for regular antibiotic stewardship and strict surveillance in the hospitals to prevent misuse of available antimicrobials. Keywords: Kebsiella pneumoniae , Gram-negative, noscomial infec- tion Objectives: To determine the antibiotic susceptiblity pattern of k. pneumoniae isolated from samples of patients attending aTertiary Hospitals at Ile-Ife, Nigeria Methods: K. pneumoniae strains were identified by their morphology and biochemical characteristics according to the standards. Antibiotic sensitivity testing was done for all the isolates on Mueller–Hinton agar by modified Kirby–Bauer disc diffusion technique (Bauer, 1990). Results: 1144 clinical samples were cultured from various sites from patients at Obafemi Awolowo University Teaching Hospitals Complex, Ile-Ife. K. pneumoniae were most frequently isolated from urine 604 (42.5%), sputum 240 (29.9%) followed by blood 180 (42.9%), pus 86 (37.0%) and CSF with the least incidence of 34 (14.8%). All isolates were resistant to different antibiotics such as amoxycilin 64%, gen- tamicin 92.6%, erythromycin 82.3%, trimethoprim, Sulfamethoxazole 96.3% tetracycline 88.5%, ciprofloxacin 31.2% nitrofurantoin 31.2%, ceftazidime 69%, cefotaxime 74%, ceftriaxone 79.6% with all the organisms showing 100% sensitivity to imipenem. Conclusion: All of the strains isolated were sensitive to imipenem. A major increase in resistance and decrease in sensitivity was observed for all the drugs tested towards k. pneumoniae strains isolated from blood, sputum, urine, CSF and pus samples. This study suggested that there is also a need to emphasize on the rational use of antimicrobials and regular antimicrobial susceptibility surveillance is essential. P101 Aeromonas species isolated from stool cultures and their susceptibilities to various antibiotics B. Ongen 1 *, M. Ilktac 1 , A. Aydın 1 , H. Nazik 1 . 1 Medical Microbiology Department, Istanbul University, Istanbul Medical Faculty, Istanbul, Turkey E-mail address : ongenb@gmail.com Introduction: Aeromonas spp. are emerging agents of gastroenteritis. Since most of the species produce inducible type chromosomal beta- lactamase, resistance can develop during beta-lactam therapy [1].