Evaluating disinfectant efficacy on mixed biofilms comprising Shiga toxigenic Escherichia coli, lactic acid bacteria, and spoilage microorganisms

This study aimed to investigate the impact of temperature and the presence of other microorganisms on the susceptibility of STEC to biocides. Mature biofilms were formed at both 10°C and 25°C. An inoculum of planktonic bacteria comprising 106 CFU/mL of spoilage bacteria and 103 CFU/mL of a single E. coli strain (O157, O111, O103, and O12) was used to form mixed biofilms. The following bacterial combinations were tested: T1: Carnobacterium piscicola + Lactobacillus bulgaricus + STEC, T2: Comamonas koreensis + Raoultella terrigena + STEC, and T3: Pseudomonas aeruginosa + C. koreensis + STEC. Tested biocides included quaternary ammonium compounds (Quats), sodium hypochlorite (Shypo), sodium hydroxide (SHyd), hydrogen peroxide (HyP), and BioDestroy®-organic peroxyacetic acid (PAA). Biocides were applied to 6-day-old biofilms. Minimum Bactericidal Concentrations (MBC) and Biofilm Eradication Concentrations (BEC) were determined. Planktonic cells and single-species biofilms exhibited greater susceptibility to sanitizers (p < 0.0001). Lactobacillus and Carnobacterium were more susceptible than the rest of the tested bacteria (p < 0.0001). Single species biofilms formed by E. coli O111, O121, O157, and O45 showed resistance (100%) to Shypo sanitizer (200 ppm) at 25°C. From the most effective to the least effective, sanitizer performance on single-species biofilms was PAA > Quats > HyP > SHyd > Shypo. In multi-species biofilms, spoilage bacteria within T1, T2, and T3 biofilms showed elevated resistance to SHyd (30%), followed by quats (23.25%), HyP (15.41%), SHypo (9.70%), and BioDestroy® (3.42%; p < 0.0001). Within T1, T2, and T3, the combined STEC strains exhibited superior survival to Quats (23.91%), followed by HyP (19.57%), SHypo (18.12%), SHyd (16.67%), and BioDestroy® (4.35%; p < 0.0001). O157:H7-R508 strains were less tolerant to Quats and Shypo when combined with T2 and T3 (p < 0.0001). O157:H7 and O103:H2 strains in mixed biofilms T1, T2, and T3 exhibited higher biocide resistance than the weak biofilm former, O145:H2 (p < 0.0001). The study shows that STEC within multi-species biofilms' are more tolerant to disinfectants.

Influence of contemporary ceramo-metallic crown decontamination on the surface roughness, color stability, and disinfection. An in vitro analysis

AIM

To assess the antimicrobial effects, surface roughness (Ra), and color change (ΔE) of Morinda Citrofolia, Sapindus Mukorossi, Indocyanine green photosensitizer, and 2% NaOCl on metal ceramic crown colonized with C. Albicans, S aureus, S. mutans, and E. coli.

MATERIAL AND METHODS

An aggregate of 40 (n = 10 each) Ni/Cr metal-ceramic crowns were fabricated and inoculated with the American Type Culture Collection (ATCC) of varied microbial colonies colonized by C. Albicans, S aureus, S. mutans, and E. coli. After inoculation, specimens were exposed to four different types of disinfection methods i.e. group 1: MC, group 2: SM, group 3:ICGP, and group 4 2% NaOCl respectively to evaluate antimicrobial efficacy, Ra, and color change. Later, the microbial assay was performed and expressed as CFU/ml (log 10). Ra was assessed using a surface analyzer and color change ΔE was evaluated using a spectrophotometer Statistical analysis was performed by using two-way ANOVA and Post HocTukey's test maintaining a significance level of p less than 0.05.

RESULTS

The highest antimicrobial efficacy for metallic-ceramic crown decontamination against all inspected microbial colonies was unveiled by group 1: MC, whereas the lowest disinfection efficacy was revealed by group 4 sterilized with 2% NaOCl (control). Metallic ceramic crown decontamination with MC and SM substantiated equivalent antimicrobial efficacy in plummeting CFU/mL (log10) of C.Albicans, S aureus, S.mutans, and E. coli (p>0.05). However, ICGP as a crown disinfectant validated antimicrobial efficacy significantly less compared to MC and SM (p<0.05). Ra was assessed post-disinfection with no changes observed (p>0.05) among all groups. Similarly, ΔE was significantly higher in crowns disinfected with ICGP (p<0.05) CONCLUSION: Metallic ceramic crown decontamination using herbal disinfectants Morinda Citrofolia and Sapindus Mukorossi exhibited favorable antimicrobial efficacies against microbial colonies of C. albicans, S aureus, S.mutans, and E. coli with no changes in surface roughness and color.

Reduced Susceptibility and Increased Resistance of Bacteria against Disinfectants: A Systematic Review

Disinfectants are used to reduce the concentration of pathogenic microorganisms to a safe level and help to prevent the transmission of infectious diseases. However, bacteria have a tremendous ability to respond to chemical stress caused by biocides, where overuse and improper use of disinfectants can be reflected in a reduced susceptibility of microorganisms. This review aims to describe whether mutations and thus decreased susceptibility to disinfectants occur in bacteria during disinfectant exposure. A systematic literature review following PRISMA guidelines was conducted with the databases PubMed, Science Direct and Web of Science. For the final analysis, 28 sources that remained of interest were included. Articles describing reduced susceptibility or the resistance of bacteria against seven different disinfectants were identified. The important deviation of the minimum inhibitory concentration was observed in multiple studies for disinfectants based on triclosan and chlorhexidine. A reduced susceptibility to disinfectants and potentially related problems with antibiotic resistance in clinically important bacterial strains are increasing. Since the use of disinfectants in the community is rising, it is clear that reasonable use of available and effective disinfectants is needed. It is necessary to develop and adopt strategies to control disinfectant resistance.

Anti-biofilm activity of dodecyltrimethylammonium chloride microcapsules against Salmonella enterica serovar Enteritidis and Staphylococcus aureus

Dodecyltrimethylammonium chloride (DTAC) was trapped into maltodextrins/pectin spray dried microcapsules to improve its activity against Salmonella enteritidis and Staphylococcus aureus biofilms. Two different microcapsules were prepared: uncomplexed DTAC-microcapsules (UDM), containing DTAC and maltodextrins; and complexed DTAC-microcapsules (CDM) containing DTAC complexed with pectin and maltodextrins. The minimum inhibitory concentrations (MIC) of both free and microencapsulated DTAC were investigated against S. Enteritidis and S. aureus. The MICs of DTAC were significantly lower when encapsulated. CDM treatment resulted in a 2 and 3.2 log reduction in S. aureus and S. Enteritidis biofilm culturable biomass, respectively. Microencapsulation reduced the cytotoxicity of DTAC by up to 32-fold. Free DTAC and CDM targeted the cell membrane resulting in the leakage of the intracellular molecules and subsequent cell death. The development of DTAC microcapsules reduced the amount of DTAC required to maintain the high standards of cleanliness and hygiene required in the food processing industries.