Objective:

To evaluate the bactericidal efficacy of three types of ultraviolet light according to their wavelength: UVA (315 nm - 400 nm), UVB (280 nm - 315 nm) and UVC (200 nm - 280 nm).

Materials and methods:

Two processes were carried out in the experimental phase. The first process consisted of obtaining the bacterial inoculum E. coli. The bacteria grew in liquid LB culture medium at an OD of 600 nm, where a concentration of 3.9x107 CFU/ml was obtained. Subsequently, 30 μl of bacteria were seeded in petri dishes with solid LB culture medium. The second process consisted of the assembly and arrangement of the UV light. In this case, LED were used for each type of UV light which allowed the design of three lamps with different power (1, 3, 5 watts/per LED). Once the bacteria were inoculated in the culture medium, each plate was irradiated with a lamp using powers of 0.051 w/cm2, 0.152 w/cm2 or 0.254 w/cm2 at intervals of 1, 3 and 5 minutes and with a distance fixed exposure of the lamp to the of 1cm culture. Afterwards, the petri dishes were left at 37°C for 16 hours.

Results:

The lamps using UVA light did not have any type of effect on the bacteria. Lamps that generate UVB light slightly affected the growth of bacteria only under conditions of high power and long exposure times. The UVC lamps managed to fulfill the bactericidal effect by eliminating all the bacteria from the area of direct incidence of the UV light.

Conclusion:

UVA and UVB light do not have marked bactericidal effects, while UVC light has a bactericidal effect in the area of incidence, independent of the power and exposure time.

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