Isolation, identification and drug resistance analysis of Morganella morganii from Symphysodon discus

ObjectiveThe present experiment was conducted to isolate and identify Morganella morganii from dis-eased Symphysodon discus and analyze its drug sensitivity, in order to provide scientific basis for clinical diagnosis and rational treatment of S. discus infected with M. morganii. MethodPathogen was isolated from diseased S. discus, and then identified by observing its morphology, determining physiological and biochemical indexes, analysing 16S rDNA se-quence. Drug sensitivity was analyzed by Kirby-Bauer’s agar diffusion method. ResultResults showed that, one dom-inant bacterial strain DS2015 that was isolated from diseased S. discus was gram-negative bacterium and shared 100%similarity in physiological and biochemical indexes with M. morganii. Its 16S rDNA sequence was 1208 bp in length (Gen-Bank database No. KR866070). Phylogenetic tree based on 16S rDNA sequence indicated that strain DS2015 was clus-tered with M. morganii, and Bootstrap test value was 99. In addition, the identification result based on Biolog also showed that, strain DS2015 was most likely to be M. morganii. The drug sensitivity test indicated that, strain DS2015 was highly sensitive to gentamycin, neomycin, kanamycin, piperacillin, piperacillin/sulbactam, ceftriaxone, chloramphenicol, nor-floxacin, ofloxacin and sulfamethoxazole/trimethoprim, but was resistant to 9 drugs such as penicillin G, cefalexin, cefra-dine, tetracycline, doxycycline, erythromycin, clindamycin, vancomycin and furazolidone. ConclusionM. morganii can cause S. discus infected symptoms such as body blackening, skin secreting massive mucus and fin festering, even lead to death in severe cases. Therefore, 10 kinds of antibiotics can be selected to treat S. discus infected with M. morganii, in-cluding gentamycin, neomycin, kanamycin, piperacillin, piperacillin/sulbactam, ceftriaxone, chloramphenicol, norfloxacin, ofloxacin and sulfamethoxazole/trimethoprim.