Antimicrobial and antibiofilm potentials of cinnamon oil and silver nanoparticles against Streptococcus agalactiae isolated from bovine mastitis: new avenues for countering resistance

Abstract

Background Streptococcus agalactiae (S. agalactiae) is a contagious pathogen of bovine mastitis. It has financial implications for the dairy cattle industry in certain areas of the world. Since antimicrobial resistance increases in dairy farms, natural antimicrobials from herbal origins and nanoparticles have been given more attention as an alternative therapy. Hence, this study reported the antimicrobial and antibiofilm potentials of cinnamon oil, silver nanoparticles (AgNPs), and their combination against multidrug-resistant (MDR) S. agalactiae recovered from clinical bovine mastitis in Egypt. Results Our findings revealed that 73% (146/200) of the examined milk samples collected from dairy cows with clinical mastitis were infected with Streptococci species. Of these, 9.59% (14/146) were identified as S. agalactiae and categorized as MDR. S. agalactiae isolates expressed four virulence genes (Hyl, cylE, scpB, and lmb) and demonstrated an ability to produce biofilms. Cinnamon oil showed high antimicrobial (MICs ≤0.063 μg /mL) and antibiofilm (MBIC50 = 4 μg/mL) potentials against planktonic and biofilms of S. agalactiae isolates, respectively. However, AgNPs showed reasonable antimicrobial (MICs ≤16 μg/mL) and relatively low antibiofilm (MBIC50 = 64 μg/mL) activities against screened isolates. Synergistic antimicrobial or additive antibiofilm interactions of cinnamon oil combined with AgNPs were reported for the first time. Scanning electron microscope (SEM) analysis revealed that biofilms of S. agalactiae isolates treated with cinnamon oil were more seriously damaged than observed in AgNPs cinnamon oil combination. Moreover, reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) showed that cinnamon oil exerted a remarkable down-regulation of pili biosynthesis genes (pilA and pilB) and their regulator (rogB) against S. agalactiae biofilms, meanwhile the AgNPs cinnamon oil combination demonstrated a lower efficacy. Conclusions This is an in vitro preliminary approach that documented the antibiofilm potential of cinnamon oil and the inhibitory activity of cinnamon oil and its combination with AgNPs against MDR S. agalactiae recovered from clinical mastitis. Further in vivo studies should be carried out in animal models to provide evidence of concept for implementing these alternative candidates in the treatment of dairy farms infected by streptococcal mastitis in the future.

Whole-Genome Sequencing of Gram-Negative Bacteria Isolated From Bovine Mastitis and Raw Milk: The First Emergence of Colistin mcr-10 and Fosfomycin fosA5 Resistance Genes in Klebsiella pneumoniae in Middle East

“…Treatment of mastitis is often applied without prior knowledge of cause-related agents and mostly with broad-spectrum antimicrobials, which are known to enhance resistance evolution to a greater extent. This increases the selective pressure on potentially present pathogens and is considered a possible human health hazard ( Neyra et al, 2014 ; Abd El-Aziz et al, 2021b ).…”

Environmental Streptococcus uberis Associated with Clinical Mastitis in Dairy Cows: Virulence Traits, Antimicrobial and Biocide Resistance, and Epidemiological Typing

“…Antimicrobial resistance is one of the world's leading threats to human and animal health [12]. It appears to have an extreme occurrence among streptococcal isolates of mastitis in Egypt [13] and S. uberis in many countries [4,14,15]. However, this susceptibility can vary from one region to another.…”

“…Even within the same region, it is necessary to monitor the pathogens' resistance to the antimicrobials used in the treatment of mastitis in various areas [16]. In Egypt, most bovine mastitis studies have focused on the inclusion of Escherichia coli, Staphylococcus aureus, Streptococcus agalactiae, and, infrequently, S. uberis [13,17,18].…”

Optimization of Streptococcus agalactiae Biofilm Culture in a Continuous Flow System for Photoinactivation Studies

“…There is no single recommended method for S. agalactiae biofilm growth experiments. S. agalactiae biofilms are usually grown on polystyrene 96-well plates in TSB [21][22][23][24] or THB [6,[25][26][27][28][29][30]. Some deviations have been reported, such as THB supplemented with yeast extract [31], TSB supplemented with bovine serum [5], TSB supplemented with 3% BSA [32], RPMI [27], cation adjusted-Mueller Hinton broth (CA-MHB) [33] or CA-MHB supplemented with lysed horse broth [34].…”

“…Against S. agalactiae biofilms, therapies based on human milk oligosaccharides [25,26], tea saponin [21], benzalkonium chloride [24], staphylococcal bacteriophage lysin CHAPk [32], or synthetic ellagic acid glycosides [29] have been proposed. Therapies based on the synergistic effect of antibiotics [34], synergistic effect of silver nanoparticles with eugenol [23], or silver nanoparticles with cinnamon oil [22] have also been proposed. We have previously summarized the use of photoinactivation against biofilms of ESKAPE pathogens [48], which cause numerous clinical infections.…”