Bactericidal, Bacteriolytic, and Antibacterial Virulence Activities of Boesenbergia pandurata (Roxb) Schltr Extract against Streptococcus pyogenes

Purpose: To determine the anti-Streptococcus pyogenes activity of the chloroform extract of Boesenbergia pandurata (Roxb.) Schltr. (Zingiberaceae) and investigate its possible antibacterial mechanisms of action.Methods: Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values were investigated against 47 clinical isolates of S. pyogenes. Time-kill study was performed to determine how quickly the extract acts on S. pyogenes. The ability of the extract to damage bacterial cell wall and effects on S. pyogenes virulence factors including protease enzyme and haemolysin were investigated.Results: The extract exhibited good antibacterial activity against all of the clinical isolates of S. pyogenes with similar MIC and MBC ranging from 3.91-62.50 μg/ml. Complete killing of the bacterial cells by the extract at concentrations of 4MIC, 2MIC, and MIC occurred within 4, 8, and 12 h, respectively. Treatment of the bacterial cells with the extract at 2MIC and 4MIC caused cell lysis. All the test concentrations (1/32 - 1/2MIC) produced no effects on protease and haemolysin enzymes.Conclusion: Boesenbergia pandurata extract has powerful in vitro activity against S. pyogenes. The ability of the extract to lyse the bacterial cells suggests that the mechanism of action may be associated with cell wall and cell membrane damage.Keywords: Antibacterial, Bacteriocidal, Bacteriolytic, Virulence, Boesenbergia pandurata, Streptococcus pyogenes

Anti-Streptococcus pyogenes Activity of Selected Medicinal Plant Extracts Used in Thai Traditional Medicine

Purpose: To evaluate the anti-Streptococcus pyogenes activity of selected medicinal plants used in Thai traditional medicine.Methods: Sixty-nine extracts of 51 selected Thai medicinal plant species were tested for anti-S. pyogenes activity by paper disc agar diffusion and broth microdilution methods.Results: Ten plants including Boesenbergia pandurata (Roxb.) Schltr., Cinnamomum bejolghota (Buch.-Ham.) Sweet, Cinnamomum porrectum (Roxb) Kosterm, Eleutherine americana Merr., Gymnopetalum cochinchinensis (Lour.) Kurz, Piper betle L., Quercus infectoria G. Olivier, Quisqualis indica L, Rhodomyrtus tomentosa (Aiton) Hassk., and Walsura robusta Roxb. demonstrated good antibacterial activity against S. pyogenes NPRC 101. These plants were selected and further evaluated for their anti-S. pyogenes activity against 11 isolates of S. pyogenes from patients with upper respiratory tract infections. Three plants including Boesenbergia pandurata, Eleutherine americana, and Rhodomyrtus tomentosa exhibited good antibacterial activity against all S. pyogenes isolates and produced similar activities against different tested isolates. Boesenbergia pandurata and Rhodomyrtus tomentosa demonstrated antibacterial activity with the same minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) range of 3.91 - 31.25 μg/ml whereas Eleutherine americana displayed MIC and MBC values of 250 and 250-500 μg/ml against all S. pyogenes isolates.Conclusion: Boesenbergia pandurata, Eleutherine americana, and Rhodomyrtus tomentosa have great antibacterial potentials against S. pyogenes.Keywords: Antibacterial activity, Boesenbergia pandurata, Eleutherine americana, Rhodomyrtus tomentosa, Streptococcus pyogenes, Thai medicinal plant, Upper respiratory tract infection

Pectin and xyloglucan influence the attachment of Salmonella enterica and Listeria monocytogenes to bacterial cellulose-derived plant cell wall models

Minimally processed fresh produce has been implicated as a major source of foodborne microbial pathogens globally. These pathogens must attach to the produce in order to be transmitted. Cut surfaces of produce that expose cell walls are particularly vulnerable. Little is known about the roles that different structural components (cellulose, pectin, and xyloglucan) of plant cell walls play in the attachment of foodborne bacterial pathogens. Using bacterial cellulose-derived plant cell wall models, we showed that the presence of pectin alone or xyloglucan alone affected the attachment of three Salmonella enterica strains (Salmonella enterica subsp. enterica serovar Enteritidis ATCC 13076, Salmonella enterica subsp. enterica serovar Typhimurium ATCC 14028, and Salmonella enterica subsp. indica M4) and Listeria monocytogenes ATCC 7644. In addition, we showed that this effect was modulated in the presence of both polysaccharides. Assays using pairwise combinations of S. Typhimurium ATCC 14028 and L. monocytogenes ATCC 7644 showed that bacterial attachment to all plant cell wall models was dependent on the characteristics of the individual bacterial strains and was not directly proportional to the initial concentration of the bacterial inoculum. This work showed that bacterial attachment was not determined directly by the plant cell wall model or bacterial physicochemical properties. We suggest that attachment of the Salmonella strains may be influenced by the effects of these polysaccharides on physical and structural properties of the plant cell wall model. Our findings improve the understanding of how Salmonella enterica and Listeria monocytogenes attach to plant cell walls, which may facilitate the development of better ways to prevent the attachment of these pathogens to such surfaces