Inhibition of bacterial biofilms by carboxymethyl chitosan combined with silver, zinc and copper salts

Abstract

Investigation of the antimicrobial action of carboxymethyl chitosan (CMCh) is among the alternative approaches in the control of pathogenic microorganisms. This study aimed to screen the toxicity using the brine shrimp lethality assay and to investigate the inhibitory activity of carboxymethyl in isolation or in combination with silver nitrate, copper sulfate and zinc sulfate on biofilm formation by Staphylococcus aureus ATCC 6538, Staphylococcus epidermidis ATCC 12228, Kocuria rhizophila ATCC 9341, Pseudomonas aeruginosa ATCC 9027, Escherichia coli ATCC 25312, and Burkholderia cepacia ATCC 17759. The CMCh was obtained by reacting chitosan with monochloroacetic acid under alkaline conditions, and the occurrence of carboxymethylation was evidenced by FTIR and H NMR spectroscopy. The CMCh was combined with metallic salts (AgNO, CuSO·5HO and ZnSO) to perform the bioassays to screen the toxicity, to determine the minimum inhibitory concentration and the impact of sub-inhibitory concentrations against biofilm formation. Although CMCh did not show inhibitory activity against bacterial growth, it had an interesting level of inhibition of bacterial biofilm. The results suggest that sub-inhibitory concentrations of compounds were effective against biofilm formation.

Inhibition of the Citrus Canker Pathogen Using a Photosensitizer Assisted by Sunlight Irradiation

“…We want to point out that the adjuvant agent, zinc phthalocyanine, has absorption at the far red region (Kobayashi et al, 2003), and thus does not interfere with the photodynamic effect of the DIBPD. The minimum inhibitory concentration (MIC) of zinc salt or its metal against bacteria was very high (500 µg/ml, or 3.12 mM) (Goncalves et al, 2017;Gugala et al, 2019), much higher than the concentration of adjuvant that we used here. Thus, it is unlikely that the antimicrobial efficacy of PSC observed here was due to the zinc salt in the adjuvant.…”

Larvicidal Activity of Inorganic Salts Against Anopheles Stephensi and Culex Quinquefasciatus

“…The weak acid characteristic of (NH4)2SO4 and NaH2PO4 and the weak base characteristic of Na2CO3 and NaHCO3 may be responsible for the larvicidal activities of these inorganic salts; because no mortality of Anopheles stephensi and Culex quinquefasciatus larvae was observed with the neutral inorganic salts sodium chloride (NaCl) and sodium phosphate (Na3PO4) aqueous solutions, even at doses 10 times higher than those tested for the weak acid and weak base inorganic salts (data no shown). Previous studies found that inorganic salts have very interesting antimicrobial [28,29], fungicide (especially Na2CO3 and NaHCO3) [30,31] and insecticide properties [32]. Darriet et al [33] also found that mineral and organic compounds have an impact on the development of larvae because the NPK fertilizer placed in water killed all the Aedes Aegypti larvae before pupation.…”

Biofilms Formed by Pathogens in Food and Food Processing Environments

“…Nanoparticles (NPs) can be used for both inhibition of biofilm formation and eradication of already formed ones [108].…”