D.P. Isore

Detection and characterization of pathogenic Pseudomonas aeruginosa from bovine subclinical mastitis in West Bengal, India

Aim: Subclinical mastitis in bovines is mainly responsible for the huge economic loss of the dairy farmers, of which Pseudomonas aeruginosa is one of the causative agents. The study was aimed at a screening of suspected milk samples from different cattle farms of West Bengal for detection and confirmation of P. aeruginosa strains followed by their characterization. Materials and Methods: Around 422 milk samples were screened from different dairy farms primarily by on-spot bromothymol blue (BTB) test and then in the lab by somatic cell counts (SCC) to finally consider 352 samples for detection of P. aeruginosa. Selective isolation and confirmation of the isolates were done using selective media, viz., cetrimide and Pseudomonas agar followed by confirmation by fluorescent technique. Molecular characterization of the strains was done by polymerase chain reaction for the presence of toxA (enterotoxin A, 352 bp) and exoS (exoenzyme S, 504 bp) genes. Results: Approximately, 371 (87.9%) samples were positive in on-spot BTB test among which 352 (94.8%) samples revealed high SCC values (more than 3 lakh cells/ml) showing infection when screened. Among these, 23 (6.5%) samples yielded typical Pseudomonas sp. isolates out of which only 19 (5.4%) isolates were confirmed to be P. aeruginosa which showed characteristic blue-green fluorescence due to the presence of pigment pyoverdin under ultraviolet light. Out of these 19 isolates, 11 isolates were positive for toxA, 6 isolates for exoS, and 2 for both these pathogenic genes. Conclusion: Approximately, 5.4% cases of bovine subclinical mastitis infections in South Bengal were associated with P. aeruginosa which possess pathogenic genes such as toxA (63.2%) and exoS (36.8%).

Lymphocystis infection in an uncommon host: Goldfish (Carassius auratus, Linn.)

Creamy white coloured nodules were observed on skin of the dorsal part of head of 5 months old goldfish (Carassius auratus Linn.), kept in an aquarium. On microscopy of collected skin tissue, clumps of cells were observed suggesting Lymphocystis disease (LCD) affected fibroblasts. To confirm presence of Lymphocystis disease virus (LCDV) in the lesions, nodules were pooled and total DNA was extracted. Subsequently, polymerase chain reaction (PCR) was performed using established primers of major capsid protein (MCP) of LCDV that confirmed presence of LCD virus in the lesion. The affected fish was treated with potassium permanganate and showed no lesion in post treatment periods (6th day onward) up to 1 month. Detection of LCD infection in an un-common host i.e. goldfish expands the knowledge regarding susceptible host range of the virus.

Detection of methicillin resistance and antimicrobial sensitivity of Staphylococcus Aureus from domestic animals

Staphylococcus aureus is a fascinating pathogen residing on skin and mucous membrane of domestic animals and man. A total of 92 clinical samples (milk, nasal swab, wound swab) from cattle (n = 36), goat (n = 29) and dog (n = 27) of West Bengal, India were examined by conventional and molecular methods for S. aureus. Screening for methicillin resistance was determined phenotypically by cefoxitin disc diffusion and genotypically by mecA PCR. A total of 41 isolates of S. aureus from cattle (n = 20), goat (n = 13) and dog (n = 8) were confirmed by S. aureusspecific thermonuclease (nuc) gene polymerase chain reaction (PCR). Out of 41, two (4.88%) isolates, one each of cattle and goat, were found to be methicillin-resistant S. aureus (MRSA). Antimicrobial susceptibility of all the 41 isolates of S. aureus was determined in Bauer-Kirby disc diffusion tests. They were found to be highly sensitive to amikacin (95.12%), linezolid (100%), vancomycin (100%) and highly resistant to ampicillin (39.02%) followed by tetracycline (24.39%), azithromycin (17.07%), ciprofloxacin (17.07%) and sparfloxacin (17.07%). Prevalence of MRSA was found to be low in clinical isolates of S. aureus from domestic animals and isolates were resistant to several classes of antimicrobials.

Changes in Humoral Immunity Due to Different Doses of Levamisole in Ppr Vaccinated Goats

Healthy, PPRV sero-negative Black Bengal goats (12) were divided into three groups and levamisole was injected in two groups @ 2.5 and @ 5.0 mg/kg body weight with three doses at 24 h intervals. After seven days all the animals were vaccinated with PPR vaccine. On i-ELISA, the magnitude of antibody titre in serum samples was more in levamisole and PPR vaccine treated groups than only PPR vaccine treated group. It was concluded that levamisole may be injected @ 2.5 to 5.0 mg/kg body weight to get stronger immunity against PPR in infection-prone region.

Antibiogram of bacterial isolates originated from clinical infections of dog in Kolkata, West Bengal

Prevalent aerobic bacteria in 66 clinical samples belonging to diverse clinical conditions such as pyoderma and wound (n = 24), keratitis (n = 6), otitis (n = 10), pyometra (n = 12) and urinary tract infections (n = 14) of dogs in Kolkata, West Bengal, were detected by standard bacteriological methodology. Antibiotic sensitivity of the isolated bacterial cultures (n = 72) were performed by disc diffusion method against 13 antimicrobials. Staphylococcus sp. were most prevalent isolates (57.6%) followed by Escherichia coli (36.4%). Majority of E. coli (91.7%) isolates were found to be cefotaxime resistant indicating high prevalence of extended spectrum beta-lactamases. However, E. coli (n = 24) isolates were found to be highly sensitive to amikacin (75.0%) and levofloxacin (50%), Staphylococcus sp. (n = 38) to amikacin (88.9%) and gatifloxacin (66.7%), Pseudomonas aeruginosa (n = 6) to amikacin (100%), and gatifloxacin (66.7%) and Proteus mirabilis (n = 4) were 100% sensitive to amikacin, azithromycin, gentamicin and gatifloxacin. The bacterial isolates (n = 72), in general, were found highly resistant to ampicillin–sulbactum (94.4%), amoxicillin–clavulanic acid (86.1%), ceftizoxime (91.7%), cotrimoxazole (77.8%) and tetracycline (75%) which were least effective antimicrobials for treatment. This antimicrobial sensitivity study may be useful to veterinary clinicians for better management of clinical infections of dog.

Isolation, molecular identification and antibiogram of Pasteurella multocida in haemorrhagic septicaemia outbreak of buffaloes in West Bengal

Pasteurella multocida was isolated from clinically ill buffaloes in an outbreak of haemorrhagic septicaemia (HS). The isolates were identified by conventional culture along with molecular method of identification by polymerase chain reaction (PCR). An expected PCR amplicon of ∼460 bp and ∼620 bp products was observed using species specific PM-PCR, capsular type B specific PCR assays, respectively. In Kirby-Bauer disc diffusion method, the isolates were found to be sensitive to ofloxacin, ceftriaxone, cotrimoxazole, amikacin, gentamicin, intermediately sensitive to ciprofloxacin and resistant to tetracycline, ampicllin-salbactam, azithromycin, ceftazidime. PCR assays were found simple and quick diagnostic approach of haemorrhagic septicaemia and P. multocida capsular type B was found resistant to many antimicrobials.

Pathogenicity test of Staphylococcus sp. by experimental animal inoculation technique

Mastitis continues to have major economic impact on dairy industry and has become a global problem. Genetic upliftment of the indigenous dairy cattle through cross breeding programme has enhanced the milk yielding capacity of mammary gland predisposing susceptibility to the various infections of the mammary gland. About 95% of intramammary infections are caused by Staphylococcus spp. and Streptococcus spp. The remaining 5% are caused by other organisms. The present study was undertaken to study the pathogenicity of the Methicillin-resistant Staphylococcus aureus (MRSA) by experimental animal inoculation test.