Antimicrobial efficacy of quaternary ammonium compounds (QACs) against multidrug resistant bacterial species causing cellulitis in broiler chicken

Avian cellulitis is one of the most important field problems facing the poultry sector. Sever financial losses resulted from the condemnation of the broiler carcasses infected with cellulitis lesions. In light of this, the current study was aimed to isolation and identification of the bacterial species causing cellulitis in broiler chickens in Dakahlia and Sharkia Governorates, Egypt. The bacterial isolates were tested for their antimicrobial susceptibility and molecular detection of some virulence and antimicrobial resistance genes. In addition to evaluate the antibacterial activity of quaternary ammonium compounds and glutaraldehyde (TH4 ®) against the bacterial isolates. Four bacterial species were isolated; E. coli, S. aureus, P. aeruginosa and Proteus mirabilis with percentages of (75%), (20%), (6%) and (5%) respectively. E. coli was recorded as the most predominant isolated bacteria in this study with12 different sero- groups (O1, O2, O26, O55, O78, O91, O121, O125, O126, O128, O153 and O158). E. coli O78 and O91 were the most prevalent identified sero- groups.  The antimicrobial susceptibility testing revealed higher resistances against doxycycline and ampicillin (95.6%), amoxicillin (90.7%), norfloxacin (84%), oxytetracycline (79.1%) and amikacin (71.6%) in E. coli, doxycycline (73.3%), oxytetracycline (80%)            ,ampicillin(75%), streptomycin (80%), erythromycin (73.3%), and oxacillin (86.7%) in S. aureus, doxycycline (83.3%), oxytetracycline (77.8%), ampicillin (83.3%), amoxicillin (88.9%), neomycin (72.2%) and erythromycin (77.8%) in P. aeruginosa and doxycycline, oxytetracycline, ampicillin, amoxicillin, streptomycin and erythromycin (100% for each of them) in Proteus mirabilis. All isolated bacterial species were multidrug resistance (MDR). The molecular identification showed the detection of virulence genes: iutA in E. coli, nuc in S. aureus, toxA in P.aeruginosa and rsbA in Proteus mirabilis., with percentage of (100%). blaTEM, tetA (A), qnrA, tetK, mecA, aac(6')aph (2''), ereA and aada1 resistance genes were  reported in this study. Quaternary ammonium compounds in combination glutaraldehyde (TH4 ®) with 2% concentration showed the highest antibacterial activity against the examined multidrug resistant bacterial isolates. These results suggested for application of 2% TH4 ® to achieve effective disinfectant programs in poultry farms.