Occurrence, molecular identification and antibiotic resistance profiling of mycoplasma gallisepticum and mycoplasma synoviae from chronic respiratory disease cases in poultry birds and farm environment

Abstract

Avian mycoplasmosis is an important risk for commercial poultry production leading to enormous losses in terms of disease and productivity. The main causative agents are Mycoplasma gallisepticum and Mycoplasma synoviae. To study the variable degree of resistance to commonly prescribed and used antibiotics in mycoplasmosis, a total of 115 samples including tissue specimen and swabs were collected from chronic respiratory disease (CRD) cases of broiler and layer birds and their contaminated farm environment. The samples were directly passaged into the Brain Heart Infusion broth (supplemented with 10 % horse serum, NAD, cysteine, penicillin and thallium acetate). Positive samples were transferred to Brain Heart Infusion agar (Difco) for the isolation of Mycoplasma spp. while negative samples were declared after the third passage. Of the samples, 61.5% were found positive for Mycoplasma spp., which were recovered mostly after second passage. Out of total culture positive cases, Mycoplasma gallisepticum (MG) was identified in 62% cases and Mycoplasma synoviae (MS) in 38%, as confirmed through Polymerase Chain Reaction (PCR) using specific primers. The MG and MS isolates showed variable degrees of sensitivity against the commercially available drug of choice, tylosin. The highest Minimum Inhibitory Concentration (MIC) of enrofloxacin (112.38±4.34 µg/ml) was recorded against MG, followed by tetracyclin (91.58±4.66µl/ml), gentamicin (54.33±2.98 µg/ml), spiromicin (52.23±3.99 µg/ml) and tylosin (52.58±2.69 µg/ml). The highest MIC for enrofloxacin (168.24 ±3.82 µg/ml) was recorded against MS followed by tetracyclin (115.48±2.62 µg/ml), spiromicin (95.96 ±2.17 µg/ml), tylosin (84.84±2.56 µg/ml) and gentamicin (46.4±2.18 µg/ml). Multiplex PCR is a time tested tool for the molecular diagnosis and confirmation of Mycoplasma species.