جستجوی مقالات مرتبط با کلیدواژه "lactococcosis" در نشریات گروه "دامپزشکی"

Infectious diseases and microbial antibiotic resistance are the major problems of fish farming industry annually causing remarkable losses. Apart from the economic losses caused by these infections, some of these agents are zoonotic and may be transmitted to humans. This study was aimed to identify the common causative agents of infections in rainbow trout farms and to determine their antibiotic resistance toward some common antibiotics. Sampling was performed during a nine-month period between March and December 2021 by visiting and inspecting rainbow trout farms and the affected fish with disease symptoms were obtained from the farmed fish in Mazandaran, Lorestan, Chaharmahal and Bakhtiari and Zanjan provinces. Bacterial culture was undertaken from anterior kidney or spleen organs and the isolated bacterial strains were identified by phenotyping, biochemical and molecular assays. Antibiotic resistance pattern was evaluated by disk diffusion method (DDM) and minimum inhibition concentration against erythromycin, oxytetracycline, florfenicol, enrofloxacin and nitrofurantoin. Seventy-four bacterial isolates of Gram-positive cocci or Gram-negative coccobacilli were isolated. In phenotyping, biochemical and molecular (PCR) assays Lactococcus garvieae (12 isolates, 16.2 %), Aeromonas hydrophila (9 isolates, 12.2 %), Streptococcus iniae (17 isolates, 23 %), Streptococcus agalactiae (20 isolates, 27 %), and Yersinia ruckeri (16 isolates, 21.7 %) were identified. The majority of these isolates were obtained from the fish farms in Mazandaran province. Erythromycin and oxytetracycline with 87.8 % resistance were antibiotics with the highest resistance, while enrofloxacin with 24.3 % resistance revealed the lowest level of resistance. Antibiotic resistance rates for florfenicol and nitrofurantoin were also 43.2 % and 44.4 %, respectively. The highest antibiotic resistance was detected in the bacterial isolates of Lactococcus garvieae, Aeromonas hydrophila, Streptococcus iniae, Streptococcus agalactiae and Yersinia ruckeri, respectively. This study shows that the spread of streptococcosis, lactococcosis, yersiniasis and Aeromonas septicemia and their frequent treatments has led to an increase in antibiotic resistance, especially against commonly used drugs such as erythromycin and oxytetracycline.

The occurrence of resistance to antibiotics in bacterial pathogens due to their unnecessary consumption, as well as,the importance of use antibiotics in the outbreaks with heavy economic failures cause that finding optimal clinical dosage would be striking. The present study was intended to the determination of optimal clinical dosage of orally administered florfenicol in rainbow trout with the experimental Streptococcosis/ Lactococcosis, and assessment of drug residues in their muscles. First, the median lethal dose (LD50) of Streptococcus iniae and Lactococcus garvieae for fish was determined via daily casualty record and calculating the probit regression. These doses were applied to determine ED50 in control and orally treated groups with dosages including 5, 10, 20, and 40 mg/kg-1 BW in 10 consecutive days. The liver and muscles of the survived fish were sampled three times after the therapeutic session, since sample and standards preparing, the chemical analysis was performed by high-performance liquid chromatography. Amounts of orally administered florfenicol for L. garvieae and S. iniae were 14.52 and 15.49 mg/kg BW during 10 consecutive days, respectively. Maximum limit residual (MRL) of sampling tenth day in the liver and muscle were 0.461±0.064 and 0.622±0.103 µg/g that were significantly lower than authorized amount of the European agency for the evaluation of medicinal products. The optimal clinical dosage of florfenicol in rainbow trout with the experimental disease was equal to mean of the median effective dose of the drug was known 15 mg/kg BW that it takes at least 10-day recovery time after administration of this dosage for safe consuming of these fishes

Strepococcosis and lactococcosis are economically important zoonotic diseases in aquaculture industry particularly in farmed rainbow trout. The annual loss due to the disease is tens millions USD. Because of the disease occurrence in farmed rainbow trout in Iran، this study was aimed to identify 20 risk factors in 38 trout farm in Fars (16 farms) and Lorestan (22 farms) provinces. Infected fish were sampled for the confirmation of the disease occurrence by bacteriological and molecular methods. The obtained results showed that there was a closed correlation between the presence of the risk factors (90%) and clinical signs (100%) of the disease. Also، bacteriological and molecular diagnosis methods، confirmed that the disease occurrence in 30 trout farms (15 fish farms in Lorestan and 15 fish farms in Fars) were involved in clinical farm of diseases. The results of this study also showed that the number of fish farms infected with Lactococcus garvieae was higher than Streptococcus iniae. Also، presence of both risk factors and clinical signs of the disease were significant in the trout farms of Fars and Lorestan provinces.

Lactococcus garvieae is the etiological agent of lactococcosis, an emerging disease which affects several fish species and causes important economic losses both in marine and freshwater aquaculture. Lactococcosis usually happens when water temperature increases over 15°C during the year. Normally, it causes a hyperacute and haemorrhagic septicemia in fish. This paper presents a procedure for producing experimental vaccine for rainbow trout (Oncorhynchus mykiss) lactococcosis including aspects such as pathogen characterization, pathogenicity, mass cultivation, safety, potency and field trial tests for immersion use. In the potency test, after challenging the vaccinated fish with live pathogenic bacteria (1×107 bacteria per milliliter of immersing solution) and observing for 72 hours thereafter, 10% of fish died while the control group showed 60% mortality within the observation time. In the field trial from vaccination time onward till marketing of the fish, those mortalities that occurred in groups of vaccinated and non-vaccinated fish were recorded. Total death occurred in the vaccinated group was 11%, while in non vaccinated group this number was approaching 23%. This observation indicates a 50% reduction in mortality in the vaccinated group. This is the first report on experimental vaccine against lactococcosis in fish that is produced and tested in Iran.