Mycoplasma is associated with fatal diseases in human, animals, and fish. Mycoplasma of aquatic origin has not been thoroughly studied. The current study has shed the light on isolation and characterization of unique piscine Mycoplasma isolates retrieved from diverse geographical locations across the Egyptian state. Mycoplasma spp. was isolated using specific culture media. Mycoplasma was identified using the morphochemical tests and then confirmed molecularly by PCR of the 16S rRNA gene. The results indicated that the incidence of Mycoplasma from Cyprinus carpio, Oreochromis niloticus, Aulopiformes synodontida, and Clarias gariepinus were 33.33%, 16.36%, 8.108%, and 6.45%, respectively, while Mugil cephalus were negative for Mycoplasma isolation. Mycoplasma was detected only from gills and swim bladder of affected fish. Biochemically, the isolated Mycoplasmas were grouped into two clusters. Mycoplasma cluster 1 (35 isolates) and Mycolplasma cluster 2 (7 isolates). Mycoplasma cluster 1 was positive for tetrazolium reduction while Mycoplasma cluster 2 was negative. The phylogenetic tree of partial sequences of 16S rRNA showed that both clusters were grouped in one branch and separated from other Mycoplasma spp., suggesting that both clusters are belonging to one species. Interestingly, all fish Mycoplasma isolates were PCR negative for both Mycoplasma mobile and Mycoplasma monodon using specific species primers. This result confirmed that these two clusters belonged to unspecified Mycoplasma species, for which the temporary names Mycoplasma cluster 1 and Mycoplasma cluster 2 were designated. Pathogenicity trials of both Mycoplasmas clusters revealed that all inoculated Nile tilapias were susceptible to the unspecified Mycoplasmas.

支原体与人类，动物和鱼类的致命疾病有关。水生支原体尚未被彻底研究。当前的研究揭示了从埃及全境不同地理位置获取的独特鱼支原体分离株的分离和鉴定。支原体属。使用特定的培养基进行分离。使用形态化学测试鉴定支原体，然后通过PCR对16S rRNA基因进行分子确认。结果表明，发生率支原体从鲤鱼，罗非鱼，仙女鱼目synodontida，和尖齿胡鲇分别为33.33％，16.36％，8.108％，和6.45％，而鲻为负支原体隔离。仅从受影响鱼的腮和s中检测到支原体。生化方面，分离的支原体分为两个簇。支原体簇1（35个分离株）和支原体簇2（7个分离株）。支原体簇1的四唑还原阳性，而支原体簇2的阴性。16S rRNA部分序列的系统进化树显示，两个簇都聚集在一个分支中，并与另一个分开。支原体属，表明这两个簇都属于一个物种。有趣的是，所有鱼类支原体分离株均使用特定物种引物PCR检测到流动支原体和斑节对虾均为PCR阴性。该结果证实这两个簇属于未明确的支原体种类，为其临时名称命名为支原体簇1和支原体簇2。两种支原体簇的致病性试验表明，所有接种的尼罗罗非鱼对不明支原体均易感。