Antimicrobial activity of crude extracts from actinomycetes against mastitis pathogens

Abstract

The emergence of antimicrobial resistance to commonly used antibiotics has necessitated the development of new antimicrobial products. Crude extracts produced by actinomycetes contain antimicrobial metabolites that can inhibit bacterial growth. The objective of our study was to evaluate the antimicrobial activity of crude extracts (Caat1-54 and CaatP5-8) produced by actinomycetes against isolates of Staphylococcus aureus, Staphylococcus chromogenes, Streptococcus dysgalactiae, and Streptococcus uberis, which were obtained from the milk of cows affected by mastitis in 23 dairy herds. Twenty isolates of each bacterial species were used to define minimum inhibitory concentrations (MIC) of both crude extracts and ceftiofur (positive control). The MIC and MIC were defined at the concentration required to inhibit the growth of 50 and 90% of bacterial isolates tested, respectively. The MIC results were evaluated by survival analysis. Staphylococcus aureus isolates presented MIC of Caat 1-54 ≥6.25 µg/mL, ceftiofur ≥12.5 µg/mL, and Caat P5-8 ≥100 µg/mL. Streptococcus uberis presented MIC of ceftiofur ≥0.39 µg/mL, Caat 1-54 ≥50 µg/mL, and Caat P5-8 ≥100 µg/mL. Staphylococcus chromogenes isolated from subclinical mastitis presented MIC of Caat 1-54 ≥0.78 µg/mL and ceftiofur and Caat P5-8 of ≥6.25 and ≥100 µg/mL, respectively. Streptococcus dysgalactiae isolated from clinical mastitis presented similar MIC values between antimicrobials tested (ceftiofur, Caat 1-54, and Caat P-58), but these values (≥100 µg/mL) were higher than the values obtained from other pathogens evaluated in the present study. Our results indicate that Caat 1-54 and Caat P5-8 crude extracts present in vitro antimicrobial activity against isolates of Staph. aureus, Staph. chromogenes, Strep. dysgalactiae, and Strep. uberis isolated from clinical and subclinical mastitis.

Metabolic Profile, Biotransformation, Docking Studies and Molecular Dynamics Simulations of Bioactive Compounds Secreted by CG3 Strain

“…Due to the low amount and instability of compound 39, only compound 43 was tested for antimicrobial and cytotoxic activities at concentrations ≥ 66.66 µg/mL, and the results indicate that 43 did not show any antimicrobial activity against Staphylococcus aureus [15]. Consequently, the antibacterial activity in Figure 1 at t R : 10.50-11.30 min can be linked to kenalactam B (39).…”

“…The two tubes were shaken for 20 min, followed by a centrifugation step at 9000 rpm for 10 min. The ethyl acetate was evaporated at 40 • C using a rotary evaporator, and the residue was dissolved in 1 mL of methanol and then centrifuged at 14,000 rpm for 10 min [39].…”

Is AMR in Dairy Products a Threat to Human Health? An Updated Review on the Origin, Prevention, Treatment, and Economic Impacts of Subclinical Mastitis

“… 169 , 170 Animal feed containing microbial extracts and probiotics can be regarded as an efficient technique for treating cow mastitis. 171 , 172 Few research has stated that how probiotics taken orally affect the bovine mastitis. It was demonstrated that oral treatment of L. casei Zhang and L. plantarum P-8 drastically decreased SCC and increased milk production.…”

Antimicrobial activity of polyhexamethylene biguanide nanoparticles against mastitis-causing Staphylococcus aureus

“…Staphylococcus aureus (n = 20) was isolated from mammary quarter milk samples of cows affected by clinical (n = 11; 11 herds) and subclinical (n = 9; 9 herds) mastitis in commercial dairy herds (n = 15) located in Southeast Brazil. These isolates were obtained from previous studies (Leite et al, 2018;Tomazi et al, 2018) and selected due to their resistance (or multiresistance) to antimicrobials commonly used for mastitis treatment (our unpublished data). The Staph.…”

“…A volume of 10 µL of standardized bacterial solution was applied in each well (except for broth sterility controls); the plates were covered and homogenized at 200 rpm for 10 min on a stirring table (Quimis) and then incubated at 37°C. After 18 h, 30 µL of 0.05% thiazolyl blue tetrazolium bromide (MTT; Sigma-Aldrich) was added to the plates for MIC determination by visual inspection (Leite et al, 2018).…”