An extended logistic model of photodynamic inactivation for various levels of irradiance using the example of Streptococcus agalactiae

Abstract

Irradiance is an important factor influencing the acceleration of microorganism mortality in photodynamic inactivation (pDi) processes. experimental observations of pDi processes indicate that the greater the irradiation power is, the faster the decrease in the population size of microorganisms. However, commonly used mathematical models of PDI processes usually refer only to specific values of irradiance without taking into account the influence of change in irradiance on the dynamic properties of inactivation. The main goal of this paper is to analyze the effect of irradiance on the PDI process and attempt to mathematically model the obtained dependencies. the analysis was carried out using the example of photodynamic inactivation of the bacterium Streptococcus agalactiae with the adopted Logistic pDi model optimized for several selected levels of irradiance. to take into account the impact of changes in irradiation power on the pDi model, the selected parameters were made appropriately dependent on this factor. the paper presents several variants of parameter modification with an evaluation of the model fitting quality criterion. The discussion on appropriate selection of parameters to be modified was carried out as a comparative analysis of several case studies. The extended logistic PDI model obtained in the conducted research effectively describes the dynamics of microorganism mortality in the whole tested irradiation power range. This manuscript presents the results of experimental research on the photodynamic inactivation (PDI) process using the bacterium Streptococcus agalactiae as an example. Group B Streptococcus (GBS) bacteria, the most common species of which is S. agalactiae, are Gram-positive pathogens representing one of the major causes of life-threatening bacterial infections in newborns and infants. Perinatal infections can occur in the form of earlyonset disease (EOD) or late-onset disease (LOD). Early GBS infection in newborns occurs at up to 7 days of life, causing sepsis, pneumonia or meningitis, while the late form of infection occurs between the 7th and 89th days of life, causing septicemia or meningitis, as well as inflammation of the respiratory system, joints and connective tissue 1. In recent years, an alternative form of prevention of perinatal infection has been proposed. Intensive ongoing work is focused on the generation of an effective vaccine directed against polysaccharide capsular and protein surface antigens of S. agalactiae. Nevertheless, the occurrence of several serotypes of this bacterium and the high percentage of strains intractable to serotyping methods significantly impede the development of a universal vaccine. Therefore, the ideal solution for the prevention of perinatal GBS infections seems to be the design of a safe and fast treatment for eradication of group B streptococci, which would be administered to all pregnant women immediately before giving birth (at the beginning of the regular systolic or shortly after rupture of the fetal membranes), regardless of the ...

Viricidal Efficacy of a 405‐nm Environmental Decontamination System for Inactivation of Bacteriophage Phi6: Surrogate for SARS‐CoV‐2

“…Whereas it is to be expected and shown that use of higher irradiance 405-nm light levels will increase the rate of microbial inactivation (54), the data in this paper establish that lower levels of 405-nm light are actually more germicidally efficient. The log 10 reductions and GE values shown in Table 1 indicate that lower irradiance 405-nm light is more efficient on a per unit dose basis for phage inactivation in comparison to that of equivalent higher irradiance exposures.…”

Can antimicrobial blue light contribute to resistance development? Genome-wide analysis revealed aBL-protective genes in Escherichia coli

“…The dose–exposure time relationship in the context of phototherapy is an important issue. We have knowledge from the previous studies of our research group ( 81 ) that the irradiation power influences mortality dynamics. We have observed that the greater the irradiation power, the greater the bacterial mortality.…”

Antimicrobial Photodynamic Inactivation: An Alternative for Group B Streptococcus Vaginal Colonization in a Murine Experimental Model

“…The current study describes aPDI employing a harmless photoactive compound, i.e., rose bengal (RB), which was used in our previous mechanistic studies concerning aPDI treatment [ 21 , 42 , 43 ]. RB is a xanthene dye, which has been widely applied as a photoactive compound in photodynamic treatment [ 15 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 ].…”