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UV Light and Antibiotic Resistance
The feature ``Bacterial Responses to Ultraviolet Light'' (ASM News, August 1999, p. 535-541) and ``A Place in the Sun,'' the interview on p. 537, describe many changes in the bacterial world caused by (increased) UV radiation. Both pointed also to the effect of UV light in induction of the lytic cycle in lysogenic bacterial strains leading to the liberation of bacteriophages and virions into the environment. It should be mentioned that bacteriophages, induced by this and other factors (autholysis, disinfectants, some antibiotics), can transduce genes of antibiotic resistance to susceptible bacteria. From the admirable pioneering works of Mark H. Richmond (Biochem J. 94:584-593, 1965) and Richard P. Novick (J. Gen. Microbiol. 33:21-136, 1963) in staphylococci and penicillinase, and of Bruce W. Holloway (Bacteriol. Rev. 33:419-443, 1969) in Pseudomonas aeruginosa, it became clear that transduction of antibiotic resistance can be an important factor in spread of antibiotic resistance genes in environment where UV light appeared for certain purposes (e.g., operating theaters). H. Knothe et al. (Zentralbl. Bakteriol. 250:506-510, 1981) and other authors described lysogenic wild-type strains of P. aeruginosa with multiple drug resistance in patients from which bacteriophages transducing aminoglycosides resistance to susceptible strains in vitro could be isolated. Furthermore, J. Blahovi et al. (J. Chemother. 4:335-337, 1992; J. Antimicrob. Chemother. 41:660-662, 1998) isolated in various hospitals in several countries wild-type bacteriophages in antibiotic-resistant strains of P. aeruginosa which, after isolation, transduced resistance to ``advanced'' b -lactams including ceftazidime, aztreonam and even imipenem, or meropenem. The authors even demonstrated the existence of P. aeruginosa strains with so-called bimodal transferability (M. Babalova et al., Zentralbl. Bakteriol. 283:61-68, 1995), i.e., they transferred genes of antibiotic resistance both by conjugation as well as by transduction.
Thus, it should be suspected that not only conjugational transfer of plasmids or transpositional transfer of integrons (A. A. Salyers et al., Antimicrob. Agents Chemother. 41:2321-2325, 1997), but also the process of transduction by bacteriophages induced by UV radiation or other stimuli, even by antibiotics, can increase the size of--and the gene flow between--pools of antibiotic-resistant bacteria.
Institute of Preventive and Clinical Medicine
Bratislava, Slovak Republic