Characteristics of Pseudomonas spp. isolated from food of animal origin

Abstract

Pseudomonas spp.as ubiquitous microorganism is often found in environmental raw materials as a contaminant. P. aeruginosa and P. fluorescens but also P. putida, P. fragi and P. cochorii may be isolated from milk and meet. From the view point of food hygiene synthesis of thermostable lipolytic and proteolytic enzymes in the cold chain of food production, can cause the spoilage of final product. As a causative agent of nosocomial infections, Pseudomonas spp. are often resistant to a large number of antimicrobial substances. Due to their ubiquity and ability to acquire resistance represents a potential risk to human health. The aims of the study were to assess antimicrobial susceptibility of Pseudomonas spp. isolated from food and to evaluate their proteolytic and lipolytic activity. A total of 40 isolates (20 from raw milk; 20 from carcasses of slaughtered pigs) were examined. All of the isolates were oxidase and, catalase positive, produced a pigment on Tryptone Soy Agar and had a characteristic odour. They also showed haemolysis on Blood agar, lipolysis on Tributyrin and proteolysis on Casein agar. Antimicrobial susceptibility testing was performed by disk diffusion test on piperacillin/ tazobactam, ticarcillin, imipenem, meropenem, aztreonam, amikacin, gentamicin, levofloxacin and ceftazidime. The sensitivity of milk isolates was 100%; 65%; 100%; 100%; 25%; 75%; 30%; 65% and 100%, whereas the susceptibility of carcass-derived isolates was 95%; 55%; 95%; 95%, 0%; 95%, 10%, 25% and 100%. Susceptibility of milk and carcass-derived isolates to piperacillin/tazobactam, ticarcillin, imipenem, meropenem, aztreonam, amikacin, gentamicin, levofloxacin and ceftazidime was 100%, 65%, 100%, 100%, 25%, 75%, 30%, 65%, 100% and 95%, 55%, 95%, 95%, 0%, 95%, 10%, 25%, 100%, respectively. There was no resistance to ceftazidime indicating no ESBL strains. MDR strains resistant to three or more antibiotics were 2 (10%) from milk and 4 (20%) from meat, namely ticarcillin, gentamicin, levofloxacin in milk isolates and ticarcillin, gentamicin, levofloxacin in three and piperacillin / tazobactam, ticarcillin, gentamicin, levofloxacin of one carcase isolate. In the present study, four MDR isolates were detected, 2 (10%) being isolated from milk and 4 (20%) from meat. Their resistance patterns were as follows: resistance to ticarcillin, gentamicin, levofloxacin (milk: n=2); resistance to ticarcillin, gentamicin, levofloxacin (carcase: n=3), resistance to piperacillin/tazobactam, ticarcillin, gentamicin, levofloxacin (carcase: n=1). In conclusion, pseudomonads might contaminate raw food of animal origin consequently leading to spoilage and considered as a reservoir of Pseudomonas spp. resistome.