Antimicrobial efficacy of riboflavin/UVA combination (365 nm) in vitro for bacterial and fungal isolates: a potential new treatment for infectious keratitis.
OBJECTIVE
To demonstrate the antimicrobial properties of riboflavin/UVA (365 nm) against common pathogens.


METHODS
One group of bacteria (Pseudomonas aeruginosa [PA], Staphylococcus aureus [SA], and Staphylococcus epidermidis [SE]) was tested by using Kirby-Bauer discs with (1) empty disc (Control - C); (2) riboflavin 0.1% (B2); (3) riboflavin 0.1% previously activated by UVA (B2'); (4) UVA alone (UVA); (5) group 2+additional UVA exposure (UVA+B2); and (6) group 3+additional UVA exposure (UVA+B2'). In addition, another group of microbes was tested with the same approach: methicillin-resistant S. aureus (MRSA), multidrug-resistant P. aeruginosa (MDRPA), drug-resistant Streptococcus pneumoniae (DRSP), and Candida albicans (CA). The mean growth inhibition zone (GIZ) in square millimeters was measured around the discs. The mean standard deviation (MSD) was calculated to be 3.65 when alpha = 0.01. A mean deviation (MD) > MSD indicates a significant difference.


RESULTS
In the first group, the GIZ was significantly greater after UVA (MD = 14.30), UVA+B2 (MD = 39.61), and UVA+B2' (MD = 40.45) when compared with C, B2, and B2'. UVA alone was less effective than UVA+B2 (MD = 25.31) and UVA+B2' (MD = 26.15). The second group demonstrated increased GIZ in UVA (MD = 6.98), UVA+B2 (MD = 17.80), and UVA+B2' (MD = 21.15) when compared with C, B2, and B2'. UVA alone was less effective against the second group of bacteria than was UVA+B2 (MD = 10.82) and UVA+B2' (MD = 14.17). CA did not show any GIZ after treatment.


CONCLUSIONS
Riboflavin/UVA was effective against SA, SE, PA, MRSA, MDRPA, and DRSP, but was ineffective on CA and has the potential for use in treatment of microbial keratitis in the future.
Martins
Suy Anne R
SA
Wilmer Ophthalmological Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA.
Combs
Juan Castro
JC
Noguera
Guillermo
G
Camacho
Walter
W
Wittmann
Priscila
P
Walther
Rhonda
R
Cano
Marisol
M
Dick
James
J
Behrens
Ashley
A
D001419:Bacteria / Q000187:drug effects* / Q000528:radiation effects*; D002176:Candida albicans / Q000187:drug effects / Q000528:radiation effects; D015169:Colony Count, Microbial; D003131:Combined Modality Therapy; D003320:Corneal Ulcer / Q000188:drug therapy / Q000382:microbiology / Q000532:radiotherapy; D024881:Drug Resistance, Bacterial; D018432:Drug Resistance, Multiple; D005486:Flavin Mononucleotide / Q000494:pharmacology*; D005658:Fungi / Q000187:drug effects* / Q000528:radiation effects*; D017319:Photosensitizing Agents / Q000494:pharmacology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000528:radiation effects; D013211:Staphylococcus aureus / Q000187:drug effects / Q000528:radiation effects; D013212:Staphylococcus epidermidis / Q000187:drug effects / Q000528:radiation effects; D013296:Streptococcus pneumoniae / Q000187:drug effects / Q000528:radiation effects; D014466:Ultraviolet Rays; D014467:Ultraviolet Therapy
D017319:Photosensitizing Agents; D005486:Flavin Mononucleotide