Colibacillosis, which is caused by Escherichia coli (E. coli), is one of the most common infectious diseases affecting poultry and causes the great economic losses to poultry production worldwide. The present study investigated the presence of E. coli in broiler chickens affected by colibacillosis and reared at various locations in Tiaret Province as well as evaluated the susceptibility of isolated E. coli strains to various antimicrobial agents. A total of 110 samples collected from 55 broiler chickens representing liver (n=55) and spleen (n=55) showing lesions suspected to be colibacillosis were analyzed by conventional methods, and 33 E. coli isolates were tested on a panel of seven antimicrobial agents using the disk diffusion method. The overall isolation rates of E. coli were 60% (33/55) and 50.9% (56/110) in whole chickens and organs, respectively. There was no variation in the isolation rate between organs: 50% (28/56) for liver and 50% (28/56) for spleen. All E. coli isolates tested showed 100% resistance to Nalidixic acid and Ofloxacine, followed by 93.93%, 90.90%, and 51.51% resistance to Tetracycline, Trimethoprim-sulfamethoxazole (Co-trimoxazole), and Chloramphenicol, respectively. However, low resistance to Gentamycin was observed (12.12%), whereas all E. coli isolates were susceptible to Colistin sulfate. Multidrug resistance was observed in 96.96% (32/33) of the isolates tested. We conclude that E. coli was largely present in broiler chickens affected by colibacillosis in Tiaret Province, and multidrug-resistant E. coli isolates showed high resistance to multiple antibiotics.

Equine reproductive failures for many different reasons are the main contributors to economic losses in the horse industry. This paper describes major bacterial agents isolated from thoroughbred mares that had reproductive failures in the previous year as well as the antimicrobial susceptibility of these bacterial isolates. A total of 146 vaginal and uterine swab samples were submitted to Jeju Self-Governing Veterinary Research Institute by equine veterinarians from 2011 to 2015. Streptococcus equi subspecies zooepidemicus were the most frequently encountered bacteria in 29 samples (48.3%). Other identified species included 21 samples (35%) with Escherichia coli, six samples (10%) with Klebsiella pneumoniae, and four samples (6.7%) with Pseudomonas aeruginosa. All Streptococcus equi subsp. zooepidemicus isolates were sensitive to amoxicillin-clavulanic acid, cefazolin, cefuroxime, and florfenicol, while all were resistant to tetracycline and kanamycin. All E. coli were sensitive to enrofloxacin, ciprofloxacin, and sulfamethoxazole-trimethoprim, and most were susceptible to cefazolin, amoxicillin-clavulanic acid, cefuroxime, florfenicol, and gentamicin. All K. pneumoniae isolates were sensitive to amoxicillin-clavulanic acid, cefazolin, cefuroxime, florfenicol, and ciprofloxacin, while all were resistant to sulfamethoxazole-trimethoprim. P. aeruginosa exhibited sensitivity to quinolones and aminoglycosides, particularly gentamicin, while all were resistant to cefazolin and cefuroxime.

목적 : Coagulase-negative Staphylococci 분리 균주에 대한 quinolone 계열 및 그람양성균에 효과적인 vancomycin과 erythromycin 항생제 감수성 정도를 알아보고 DNA gyrase 유전자를 분석하고자 한다. 방법 : 세균성 각막염이 의심되는 사람의 각막에서 검출한 Coagulase-negative Staphylococci 6 균주를 대상으로 ofloxacin, ciprofloxacin, levofloxacin, vancomycin, erythromycin 항생제 감수성을 실시한 후 각 균주들의 genomic DNA를 추출하여 PCR 증폭한 후 gyraseA 유전자의 DNA를 분석하였다. 결과 : 항생제 감수성 검사에서 S. epidermidis (SE-2, SE-3), S. hominis (SH-1) 그리고 S. saprophyticus (SS-1) 균주에서는 ofloxacin, ciprofloxacin, levofloxacin, vancomycin 감수성, erythromycin 내성으로 나타났으며, 나머지 균주에서는 모두 감수성으로 나타났다. gyraseA 유전자 분석에서는 S. epidermidis (SE-1) 균주에서 Met75→Thr, Met93→Val 으로 아미노산 이중 mutation이 관찰되었으며, S. warneri (SW-1)와 S. saprophyticus (SS-1) 균주에서는 다수의 silent mutation이 관찰되었다. 결론 : Coagulase-negative Staphylococci 분리균주에서 erythromycin 항생제의 내성이 있다는 것을 확인 할 수 있었으며, gyraseA 유전자 분석결과 아미노산 이중 mutation 및 silent mutation이 관찰되었다. 따라서 지금은 내성이 아니지만 silent mutation이 언제든지 내성을 일으킬 수 있을 것으로 생각된다.

Exudative epidermitis (EE) is a generalized skin disease of pigs, mainly caused by Staphylococcus hyicus (S. hyicus). Antibiotic resistant S. hyicus leads to the failure of antimicrobial treatments. This necessitates proper identification of the strains in the field and determination of their antimicrobial susceptibility. This study was carried out to isolate Korean S. hyicus and determine its antimicrobial resistance. Isolate was sensitive to ceftiofur, ciprofloxacin, enrofloxacin, gentamicin, neomycin, and tylosin, but remarkably resistant to amoxicillin, lincomycin, penicillin, streptomycin, and tetracycline. Our study contributes to the understanding of the characteristics and antimicrobial resistance of Korean S. hyicus, which in turn will provide an antimicrobial treatment strategy to control EE.

목 적: 세균성 각막염 치료에 주로 사용되는 퀴놀론계 항균제의 감수성 저하로 나타난 Serratia marcescens 균주에 대해 내성기전에 관여하는 주요 target인 gyrA와 parC 유전자를 분석하여 감수성 저하의 원인을 파악하고자 한다. 방 법: 퀴놀론계 항균제 감수성 저하 Serratia marcescens 균주들을 대상으로 genomic DNA를 추출 하여 PCR를 통해 증폭한 후 gyrA와 parC 유전자 QRDR의 DNA sequencing을 분석하였다. 결 과: parC 유전자 분석에서 SM5 균주는 Tyr51→His, Thr59→Asp으로 이중 아미노산 변이가 나타났 으며, SM6 균주는 Thr59→Asp으로, SM13 균주는 Tyr51→His으로 단일 아미노산 변이가 나타났다. 그리고 3 균주 모두 gyrA와 parC 유전자에 다수의 silent mutation이 관찰되었다. 결 론: target 유전자의 변이로 인한 항균제의 감수성이 저하되고 있다는 것을 확인할 수 있었으며, 특히 parC 유전자가 퀴놀론계 항균제의 감수성 저하를 일으키는 주요 표적임을 확인할 수 있었다. 앞으로도 세균성 각막염 치료에 퀴놀론계 항균제의 사용이 계속될 것이며, 많은 내성 균주들이 발생할거라 예측된다. 따라서 항균제를 사용할 때 내성에 대한 주의가 반드시 필요할 것으로 사료된다.

적리를 동반하는 돼지 분변에서 용혈성 균주를 분리 동정한 후, 장 독소 생성 유 무 및 항생제 감수성 시험을 수행하였다. 분리된 용혈성 균주 B. cereus BY06의 gyrB 유전자 염기서열을 분석한 결과, B. cereus와 99% 유사성을 나타내었다. PCR법에 의한 장 독소 유전자 검출 시험에서 B. cereus BY06는 장 독소 분비 양성으로 판정됨에 따라 설사형 식중독 균임이 확인되었다. B. cereus BY06를 이용한 항균제의 감수성 시험 결과, penicillin G에는 내성을 나타낸 반면 cephalothin, vancomycin, clindamycin, fusidic acid, gentamicin, ciprofloxacin, tetracycline 및 rifampin에 대하여 감수성을 나타냈다. 본 연구를 통해 돼지 분변에서 분리된 B. cereus 균주는 설사를 유발하는 장 독소를 분비하며, penicillin G에 대한 내성을 확인하였다.

Antibiotic resistant salmonellosis has shown a recent increase, making treatment of patients with Salmonella infections difficult. This study analyzed changes in the species, serogroups, and antimicrobial susceptibility of enteric pathogens isolated from stool specimens during a period of eight years from 2003 to 2010 in a tertiary hospital. In total, 237 pathogens (1.9%) were isolated from 12,289 stool specimens, comprising 50.6% NTS and 49% Vibrio parahaemolyticus. Serogroups D, B, and C Salmonella were isolated most frequently, in that order. Of the Salmonella, 49% of the isolates were ampicillin resistant and this rate for serogroups B, C, and D Salmonella was 56.8, 64.7, and 43.5%, respectively. Overall, the rates of trimethoprim-sulfamethoxazole (SXT), chloramphenicol (CM), and ciprofloxacin resistance were 11.0, 22.0, and 0%, respectively. Two cefotaxime-resistant Salmonella were isolated in 2010. All of the V. parahaemolyticus were susceptible to SXT, CM, and tetracycline. In conclusion, NTS and V. parahaemolyticus were the major enteric pathogens isolated from stool during the eight years examined, and the rate of Salmonella resistance to antimicrobial agents showed a significant increase. Antimicrobial susceptibility testing is mandatory for proper treatment of patients with Salmonella spp. infection.

The antimicrobial susceptibility of the 41 Bordetella bronchiseptica isolates was tested by using the Kirby-Bauer agar disk diffusion method. The B. bronchiseptica isolates were found to be sensitive to amoxicillin/clavulanic acid (100%), gentamicin (100%), neomycin (100%) and amikacin (97.6%), whereas they were resistant to streptomycin (100%), trimethoprim/sulfamethoxazole (100%), penicillin (100%) and ampicillin (97.6%). All the B. bronchiseptica isolates resisted to at least 4 antimicrobial agents and totally 8 different combinations of multiple antibiotic resistance patterns were noted. All of the B. bronchiseptica isolates, except one, were simultaneously resistant to streptomycin, trimethoprim/sulfamethoxazole, penicillin and ampicillin. The observed antibiotic resistance is not plasmid mediated as plasmids were absent from all the B. bronchiseptica isolates.

It has been reported that the antimicrobial susceptibility patterns of viridans streptococci vary according to geographical region. Although several studies on the antibiotic resistance of viridans streptococci in foreign countries have been reported, little is known about the distribution of resistance among viridans streptococci in Korea. In this study, 88 isolates of viridans streptococci from Korean students' dental plaque were identified as 12 different species. The susceptibility of these isolates to 8 antibiotics was investigated. The in vitro antibiotic activity of penicillin G, ampicillin, vancomycin, streptomycin, gentamicin, erythromycin, amoxicillin, and tetracycline was measured by the broth microdilution method. The range of the minimum inhibitory concentrations (MIC), MIC50, MIC90, and the percentage of the susceptible isolates were determined. Streptococcus mutans and Streptococcus salivarius were susceptible to the 8 antibiotics. Isolates with resistance to vancomycin, streptomycin, and amoxicillin were not found. The overall resistance rates of the 88 isolates to penicillin G, ampicillin, gentamicin, erythromycin, and tetracycline were 12.5%, 62.5%, 62.5%, 26.1%, and 26.1%, respectively.