Biochemical and molecular detection of Pasteurella species associated with ovine pneumonia and their antibiogram

Abstract

Pneumonic pasteurellosis caused by Pasteurella species is believed to be one of the most common and economically important types of ovine pneumonia. No previous study about the disease in Al Madinah Region, Saudi Arabia. Thus, this study was conducted to determine the association rate of Mannheimia haemolytica and Pasteurella multocida with pneumonia in sheep and to update data about their antimicrobial susceptibility patterns. A total of 100 samples (57 nasal swabs and 43 lung tissues) were collected from live diseased and animals suspected to have died of pneumonia. Samples were subjected to bacteriological examination, biochemical identification of isolates by VITEK 2 system, direct molecular identification by real time polymerase chain reaction (RT-PCR), and antibiotic sensitivity test of the isolates. The results showed an overall (isolation and molecular) detection rate of 31% (31/100) for M. haemolytica (25%) and P. multocida (6%). The isolation method indicated that only six isolates (6%, 6/100) were confirmed by VITEK 2 as M. haemolytica, with excellent identification (probability reached 99%). While, direct molecular method (for samples other than those from which isolates were obtained, n=94) revealed that 19 (20.2%, 19/94) samples were positive for M. haemolytica and six (6.4%, 6/94) for P. multocida specific 16S rRNA genes. M. haemolytica isolates were found sensitive to oxytetracycline, nitrofurantoin, trimethoprim/sulfamethoxazole, ciprofloxacin, cefoxitin, ceftazidime, ceftriaxone, imipenem, and tigecycline, in order. While, they were found completely resistant to ix cloxacillin, streptomycin, and amoxicillin/clavulanic acid. In conclusion, the detection rate of M. haemolytica emphasized its role as a major cause of ovine pneumonia, whereas P. multocida is rare. In addition, these results invigorated the role of direct molecular detection and recommend it for laboratory differential diagnosis. The isolates were resistant to limited antimicrobial agents, nevertheless, the antimicrobial susceptibility test is important for proper treatment.