Microbial colonization of soft contact lenses over time.
OBJECTIVE
To compare the bacterial colonization of soft contact lenses in subjects for successively increasing periods, up to 13 nights of wear. The aim of this study was to determine whether increasing the length of lens wear predisposed subjects to high levels of microbial colonization of lenses.


METHODS
Subjects (N = 20) were divided into those with a prior history of adverse events (N = 6), gram-negative bacterial carriers (N = 6), and those with no previous history (N = 8).


RESULTS
There were no temporal changes in microbial colonization of lenses. Lenses from all wearers were colonized at least once during the study by gram-positive bacteria at low numbers (<10 cfu/ml). Gram-negative bacteria colonized lenses at least once in 80% of all wearers. Lenses from gram-negative bacterial carriers were more frequently colonized by Staphylococcus aureus and Pseudomonas sp. compared with subjects with no previous history and subjects with a prior history of adverse events, respectively. Lenses from gram-negative bacterial carriers were less frequently colonized by a range of gram-positive bacteria compared with subjects with a prior history of adverse events.


CONCLUSIONS
Increasing the length of lens wear up to 13 nights did not result in a predictable increase in bacterial colonization of contact lenses. Gram-positive bacteria were isolated frequently but in low numbers, whereas gram-negative bacteria were present sporadically.
Cornea and Contact Lens Research Unit, School of Optometry and Cooperative Research Centre for Eye Research and Technology, University of New South Wales, Sydney, Australia.
D F
DF
Sweeney
F
F
Stapleton
C
C
Leitch
J
J
Taylor
B A
BA
Holden
M D
MD
Willcox
D000328:Adult; D015169:Colony Count, Microbial; D003262:Contact Lenses, Extended-Wear / Q000382:microbiology*; D003263:Contact Lenses, Hydrophilic / Q000382:microbiology*; D006090:Gram-Negative Bacteria / Q000302:isolation & purification*; D006094:Gram-Positive Bacteria / Q000302:isolation & purification*; D006801:Humans; D008875:Middle Aged; D013997:Time Factors