Inhibitory Effect of some Nanomaterials on Streptococcus species Producing Biofilm Isolated from some Dairy Farms

Abstract

Multidrug resistant, Streptococcus (Strep.) producing biofilm (SPB) considered the most important environmental pathogens associated with concern problems in dairy farms and confers public health hazard. This cohort study aimed to evaluate Strep. spp. in dairy farms, antibiotic resistance pattern against 15 antibiotics, and detected the ability of isolates to biofilm formation phenotypically by quantitative (polystyrene), qualitative (Congo Red Agar (CRA)) and Geno-typically by lmb and brpA genes. The minimum biofilm eradication concentration (MBEC) of chitosan nanoparticles (CNPs) and carvacrol nano-emulsions (CNE) were investigated in vitro by polystyrene method (which is considered the first record, according to the authors knowledge) in field by washing milking utensils. A total of 150 milk samples (cows and buffaloes) were collected, in addition to 48 swabs from milking utensils of different farms in Assiut Governorate, Egypt. The prevalence of Strep. spp. was 21.72% of all examined samples and the most frequently isolated pathogen was Strep. agalactia (12.6 %). Overall, there were 14% of isolates resistant to vancomycin. Strep. uberis revealed the highest resistance to most antibiotics used and 80% of it considered biofilm producers. SPB were classified to strong (23.3%), moderate (32.5%), weak (27.9%) and non-producers (16.3%) by polystyrene method, while, 55.8% considered biofilm producers by CRA. All SPB were positive to lmb and only three were negative to brpA genes. The prepared nanomaterials were characterized by Transmission Electron Microscope (TEM) and the MBECs were 30% and 20 % for CNPs and CNE, respectively. In addition, complete inhibition to SPB in milking utensils occurred at 10 and 20 minutes from washing by CNE 20% and CNPs 30%, respectively. The present study concluded that most of the isolated Strep. spp. are biofilm producers, which are resistant to studied chemotherapeutic agents. CNE is considered more efficient than CNPs for elimination of SPB.