title: UV-C-irradiation sublethal stress does not alter antibiotic susceptibility of the viridans group streptococci to β-lactam, macrolide, and fluoroquinolone antibiotic agents.
abstract: OBJECTIVE
  Previous work has indicated that environmental stresses on bacteria might lead to an upregulation of stress response. LED curing lights (315-400 nm) and other UV lights used in tooth whitening cosmetic procedures might act as stresses. We examined the effect of UV-C light, as a high-energy surrogate to the lower-energy UV-A light used in such instruments, to examine its effect on the antibiotic susceptibility of viridans group streptococci.
  
  
  METHODS
  Twelve species of viridans group streptococci were examined in this study: Streptococcus anginosus, Streptococcus australis, Streptococcus cristatus, Streptococcus gordonii, Streptococcus infantis, Streptococcus mitis, Streptococcus mutans, Streptococcus oralis, Streptococcus parasanguinis, Streptococcus pneumoniae, Streptococcus salivarius, and Streptococcus sanguinis. These organisms were exposed to varying degrees of sublethal UV-C radiation, and their minimum inhibitory concentration susceptibility was determined by broth dilution assay against three classes of commonly-used antibiotics: β-lactams (penicillin), macrolides (erythromycin), and fluoroquinolones (ciprofloxacin).
  
  
  RESULTS
  There was no significant difference between antibiotic susceptibility before UV-C exposure and following maximum sublethal stress, prior to cell death due to fatal UV-C exposure.
  
  
  CONCLUSIONS
  Exposure to UV-C light will not result in altered antibiotic susceptibility patterns on viridans group streptococci. Given that UV-C is more toxic and mutagenic than UV-A light, it is unlikely than UV-A light would yield any difference in response to such exposure.
authors.affiliation: Department of Bacteriology, Belfast City Hospital, Belfast, Northern Ireland, UK.
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Maeda
authors.forename: Wilson A
authors.initials: WA
authors.lastname: Coulter
authors.forename: Colin E
authors.initials: CE
authors.lastname: Goldsmith
authors.forename: B
authors.initials: B
authors.lastname: Cherie Millar
authors.forename: John E
authors.initials: JE
authors.lastname: Moore
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002939:Ciprofloxacin / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial / Q000528:radiation effects*; D004917:Erythromycin / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D010406:Penicillins / Q000494:pharmacology*; D014466:Ultraviolet Rays; D034363:Viridans Streptococci / Q000187:drug effects* / Q000528:radiation effects
chemical_list: D000900:Anti-Bacterial Agents; D010406:Penicillins; D002939:Ciprofloxacin; D004917:Erythromycin