CitationSarder H, Khan T, Saha ML, Punom NJ, Mandal SC and Rahman MS (2016) Prevalence and antibiotic susceptibility of Aeromonas hydrophila isolated from freshwater fishes. Journal of Fisheries 4(3): 411-419. DOI: 10.17017/jfish.v4i3.2016.177 Abstract Aeromonas hydrophila is an opportunistic microorganism. It is a secondary biological agent that contributes to the occurrence of fish diseases and its deterioration. This research was undertaken to determine the prevalence of A. hydrophila in some freshwater fishes collected from three different fish markets of Dhaka City and to test their antibiotic susceptibility. Total bacterial count and total aeromonas on different aeromonas selective media were enumerated using serial dilution technique. Bacterial isolates were characterized to identify A. hydrophila using biochemical tests and with comparison to reference strain (ATCC 7966). The lowest Aeromonas count was detected to be 2.83±0.40×10 2 cfu/g in Anabas testudineus and the highest was 1.03±0.153×10 3 cfu/g in Oreochromis mossambicus. On market basis highest aeromonas count was found in Anando Bazar (8.10±1.09×10 2 cfu/g) and lowest in Hatirpool Bazar (5.63±0.90×10 2 cfu/g) with no significant difference. Maximum susceptibility to amikacin and gentamicin was observed whereas all of the isolates were found resistant to a commonly used antibiotic amoxycillin. The obtained results point that antimicrobial susceptibility was more or less similar regardless of the origin of the samples collected. All the fishes investigated in this study contained A. hydrophila in their different organs.

Bacterial load and drug resistance pattern associated with some ready-to-eat (RTE) street foods such as Chatpoti, Fuchka, Singara, Panipuri, Ghugni-muri, Chola and water of Dhaka South City Corporation were investigated. Most of the samples were found to be contaminated and the bacterial load ranged from 2.4 × 104 - 9.2 × 106, 1.2 × 103 - 7.3 × 105 and 1.1 × 103 - 1.6 × 106 cfu/g of aerobic heterotrophic, coliform bacteria and Staphylococcus, respectively. The highest coliform load (7.3 × 105 cfu/ml) was found in the water of Gulistan. The highest aerobic heterotrophic bacteria (9.2 × 106 cfu/g) and Staphylococcus (1.6 × 106 cfu/g) were observed in the Chatpoti of Nilkhet. Among the isolated 100 different bacterial colonies, 20 Gram-positive and 8 Gram-negative isolates were studied in details. Based on the morphological and biochemical analysis, the Grampositive isolates were identified as Staphylococcus (9), Bacillus (4), Kurthia (3), Planococcus (1), Micrococcus (1), Listeria (1) and Renibacterium (1). Gram-negative isolates were identified as Klebsiella pneumoniae (3), Yersinia pestis (1), Y. pseudotuberculosis (1), Escherichia coli (1), Enterobacter aerogenes (1) and Plesiomonas shigelloides (1). The multi-drug resistance (MDR) pattern was found to be diverse. Among the MDR bacteria, Enterobacter aerogenes was found to be resistant against six common antibiotics. Plesiomonas shigelloides and Yersinia pestis were found to be resistant against five antibiotics. The multiple antibiotic resistant (MAR) indices of Gram-negative isolates ranged in between 22.22 and 66.67%. Conventionally identified five bacterial isolates with significant MAR indices were further identified with 16S rDNA sequencing and found to be as Enterobacter cloaceae Ecl1, Plesiomonas shigelloides CIFRI, Aeromonas sp. TIL_WAK_4, Aeromonas sp. 280 and Klebsiella pneumoniae KPS77. Conventional identification was found to be accurate for three isolates but the two Yersinia sp. were identified to be as Aeromonas sp. in 16S rDNA sequencing. Dhaka Univ. J. Biol. Sci. 27(1): 27-36, 2018 (January)

To identify the gut bacteria of Pangasianodon hypophthalmus (striped catfish; Pangas) using classical and molecular approach was carried out. Total bacterial count (TBC) in the gut of pangas from farm and market samples were found 5.07 ± 1.70 × 106 and 1.40 ± 0.47 × 106 cfu/g, respectively. The gut microbiota of pangas was dominated by members of the Gram-negative genera. Only three isolates (MyF1/1, MyF1/4 and GaW1/2) were found to be Gram-positive among the 16 representative isolates. Using 16S rRNA gene sequencing; Bacillus, Macrococcus, Citrobacter, Aeromonas, Proteus, Klebsiella, Enterobacter, Escherichia and Edwardsiella were found to be associated with the gut of this fish. Among them, Aeromonas was the most dominant genus (5 out of 16). Antibiotic sensitivity pattern reflected that all the isolates were sensitive to gentamycin. Multiple antibiotics resistant isolates were also identified of which MyF3/13 (identified as Citrobacter amalonaticus) was found resistant against seven tested antibiotics. The presence of pathogenic bacteria in fish gut revealed the improper handling practices in fish market and unhygienic condition in the culture sites which might be a reason of fish-borne disease outbreaks. On the other hand, widespread use of various antibiotics in aquaculture without proper awareness may lead to resistance to multiple antibiotics. Dhaka Univ. J. Biol. Sci. 29(1): 61-73, 2020 (January)

Eight different antibiotics were used against bacterial species. The antibiotics were tetracycline, ampicillin, gentamicin, kanamycin, neomycin, baquiloprim sulphadimidine, chloramphenicol and sulphamethoxazole trimethoprim.