Formação de biofilmes e multirresistência a antimicrobianos de Staphylococcus Aureus isolados da higienização de ambiente de ordenha

Abstract

Milk is na excellent nutritional value food and because its composition is substrate for microorganisms multiplication, therefore a high microbial load at milking time will result in low quality final product. Pathogenic and spoilage microorganisms contamination appears as a public health problem, in addition of causing enjury to dairy industry. Presence of Staphylococcus aureus and aerobic mesophilic bacteria are one of the most common problems in dairy farms, mainly because of bovine mastitis incidence and fails of cleaning processes of milking equipment, which can result in biofilm formation. Staphylococcus pathogenicity is associated with bacterial adhesion mechanisms, indicated as important virulence factors, such as biofilms formation and bacterial resistance. This study quantified aerobic mesophilic bacteria and S. aureus in liner, water from cleaning equipment system Clean-in-Place (CIP), and milk cooling tank at different times, before and after milking, evaluating the detergency and sanitizing process. On quantification, there was a reduction in levels of S. aureus and aerobic mesophilic bacteria in liners, but there was no statistical difference in any cleaning process. In CIP water was significant differences, with 3.81 log10 reduction of aerobic mesophilic bacteria when using detergency 1 (D1) after milking 1 (O1). Bacterial load after detergency 2 (D2) of milking 2 (O2) when compared with what was obtained after the use of sanitizer 2 (S2), 8 hours after detergency, showed significant drop (P = 0.030), reducing 4.51 log10. For S. aureus, detergency D1 and D2 and sanitization S2 diminished bacterial count in relation to detected after milking, however there was no statistical difference (P > 0.05). S. aureus average value of set milk was 3.04 log10UFC.mL-1 and 3.11 log10UFC.mL-1 for milking 1 and 2. There was no significant difference for aerobic mesophilic bacteria and S. aureus among the results before and after milk cooling tank cleaning. Fifteen S. aureus strains isolated from milking environment were selected in order to test antimicrobial sensitivity, biofilm formation capacity and other virulence factors. All samples showed multidrug resistance profile, with two 100% resistant strains to the drugs, and the others were resistant to at least six active principles. From these, 100% were penicillin G resistant, 93,34% resistant to oxacillin, tetracycline, chloramphenicol, cephalexin, amoxicillin + clavulonic acid and sulfazotrim; 73,33% resistant to doxycycline and 80% to gentamicin; 53,34% resistant to ceftiofur and 33,34% to neomycin. Multiple antimicrobials resistance indexing (IRMA) ranged from 0,5 to 1,0. For biofilm formation in different incubation temperatures (3°C, 9°C, 25°C, 36°C and 42°C), biofilms were formed on at least three evaluated temperatures, including refrigeration temperatures. On other virulence factors, 13 (86,7%) formed capsule, 9 (60%) have shown the protease presence, 4 (26,7%) expressed the α-hemolysin fator and 2 (13,3%) β-hemolysin