Efficacy evaluation of commercial disinfectants by using Salmonella enterica serovar Typhimurium as a test organism

Abstract

The efficacies of six commercial disinfectants were evaluated by using Salmonella enterica serovar Typhimurium under simulated natural conditions such as sub-zero temperature, short disinfecting time, and surface type (uneven or smooth). We used a suspensionmodel test to determine the disinfecting efficacy under varying contact times (1, 5, 10, and 30 min) and temperatures (25°C, 4°C, 0°C, and -10°C). The bactericidal effect according to surface structure was measured by using a carriermodel test at 25°C and -10°C. The effective concentrations of each disinfectant were fixed to give a disinfecting effect within a short time (< 1 min) at 25°C and -10°C. The suspension model results revealed that bactericidal efficacy significantly dropped at low temperature for most of the disinfectants used; a sodium dichloroisocyanurate product showed the strongest efficacy. In the carrier test, bacterial load on a wooden surface was more difficult to remove than that on a stainless-steel surface. The results show that commercial disinfectant products vary in their disinfecting efficacy, which is affected by several field factors including temperature, contact time, and carrier material. Environmental conditions and surface type for disinfection should be considered prior to selecting an optimal disinfectant in the field.

Keywords: Salmonella; carrier-model test; disinfectant; surface structure; suspension-model test.

Fig. 1. Evaluation of Salmonella Typhimurium bactericidal activity of six disinfectants by suspension testing at four different contact times and temperatures. Complete reduction of bacteria was defined as ≥ 7.8 log₁₀ reduction, while a > 5 log₁₀ reduction was considered effective. (A) 2.5% citric acid. (B) 0.03% CA + 0.02% QACs. (C) 0.5% MPS. (D) 1% MPS + 0.1% NaDCC. (E) 0.3% NaDCC. (F) 0.1% GA.

Fig. 2. The effect of each disinfectant against dried Salmonella Typhimurium on wood and stainless steel at 25℃ or −10℃ for 1 min or 5 min. Complete reduction of bacteria was defined as 5.1 log₁₀ reduction on stainless steel and 5.09 log₁₀ reduction on wood, while a 4 log₁₀ reduction was defined as effective. Error bars indicate standard deviations of the means. (A) 25℃ for 1 min. (B) 25℃ for 5 min. (C) −10℃ for 1 min. (D) −10℃ for 5 min. ^**Significant differences between the results from stainless steel and wood (p < 0.01).

Fig. 3. Evaluation of bactericidal activity for short contact times by different concentrations of each disinfectant at 25℃ and −10℃. Complete reduction of bacteria was defined as ≥ 7.8 log₁₀ reduction and > 5 log₁₀ reduction was considered effective reduction. (A) Citric acid. (B) Citric acid + QACs. (C) MPS. (D) MPS + NaDCC. (E) NaDCC. (F) Glutaraldehyde.