This study is intended to determine the antimicrobial resistance properties and class 1 integrons of 30 Citrobacter freundii strains isolated from pet turtles in order to determine their threat to human health. Citrobacter freundii isolates were isolated and identified by employing biochemical tests and 16SrRNA gene sequencing. Disc diffusion test and PCR amplification were employed to detect antimicrobial resistance patterns and genes, respectively. Ampicillin, amoxicillin, cephalothin and nalidixic acid resistance were observed among all isolates. Rifampicin and cefoxitin resistance was the second most prevalent and observed in 97% of the isolates, respectively. All isolates scored multiple antimicrobial resistance (MAR) indices ≥ 0.2. Aminoglycoside resistant genes were the most prevalent. aac(3')-IIa was detected in 80% of the isolates followed by aphAI-IAB and strA-strB genes in 33% and 50% of the isolates, respectively. β-lactamase encoding blaTEM, blaCTX and blaSHV genes were detected in 53%, 43% and 17% of the isolates, respectively. tetA and tetB genes were the only tetracycline resistance genes detected in 17% and 10% of the isolates, respectively. Class 1 integron integrase encoding intI1 gene (47%) and dfrA17-aadA5 gene cassette array (7%) were also detected. Pet turtle-borne multidrug-resistant C. freundii is a reservoir of antimicrobial resistance determinants in the domestic environment which poses a risk of infection.

Garlic (Allium sativum) is known to have antimicrobial effects but there are few data on its effects against fish pathogenic bacteria. This study was conducted for possible development of natural food antimicrobials from garlic extracts, particularly allicin. The filter sterilized, aqueous extract of garlic was tested for its ability to inhibit the growth of 7 fish pathogenic bacteria (E. tarda, V. ichthyoenteri, V. harveyi, P. damselae, S. iniae, S. parauberis, L. garviae) using the disc diffusion test, minimum inhibitory concentration test, and minimum bacteriocidal concentration test. The garlic extract inhibited growth and killed most of the organisms tested. The disc diffusion test was performed using garlic extracts (100%, 50%, 25%, 10%, each 20㎍), and MIC test was also performed using a diluted concentration of garlic extracts (488 - 250,000 ㎍/㎖). According to the results, garlic extracts exhibited antimicrobial activity against all of seven bacteria, and these results suggest that this garlic extract can be used as an antimicrobial substance against fish bacterial diseases in the fish industry.

The acute and subacute toxicities of trichlorfon were evaluated in blacktetras (Gymnocorymbus ternetzi). Dipping of fishes for acute toxicity was performed for a period of 24 hrs, and TLm_24h value (median tolerance limit=LC₅₀) was 12 ppm. Severe damages were observed in various organs and among them, edema and hyperplasia of gill lamellas, and epithelial edema of renal tubules were relatively prominent. The most significant change was mild epithelial deema of renal tubules in subacute toxicity test which fishes were exposed to 1.2ppm of trichlorfon for 1 week.

The acute and subacute toxicities of copper sulfate were evaluated in zebrafish (Brachydanio rerio). Dipping of fishes for acute toxicity was performed for a period of 24 h, and TLm24h value (median tolerance limit = LC50) was 1.36 ppm. Clubbing of gill filaments due to severe epithelial hyperplasia of gill lamella were oberved. And epithelial edema, fusion and necrosis of renal tubules were presented. The most significant change was mild epithelial hyperplasia of gill lamella in subacute toxicity test which fishes were exposed to 0.15 ppm of copper sulfate for 1 week.