¹Ophthalmic Institute Laboratory, Department of Ophthalmology, 'Gregorio Marañon' University General Hospital, Madrid, Spain

Correspondence: EF Rubio, c/Vizconde de los Asilos 12, 2° B 28027 Madrid, Spain. Tel: +34 91 5867326; Fax: +34 91 7423586; E-mail: elfernan@wol.es

Received 23 April 2003; Accepted 25 November 2003; Published online 27 February 2004.

Abstract

Purpose To describe the monthly prevalence of conjunctival bacteria in patients undergoing cataract extraction and the possible climatic influence on it, in Madrid, in order to clarify postsurgical endophthalmitis pathogenesis.

Methods The lower conjunctival content sample of 4432 consecutive patients awaiting cataract surgery was cultured from January 1994 to December 1996. The dates of the operations and the rehospitalization for postsurgical endophthalmitis, if this took place, were checked. The isolated bacteria were grouped to study the statistical significance of the differences in the monthly prevalence differences (² tests). Temperature and relative humidity are given monthly for the area where our patients live.

Results The total frequency of the conjunctival bacteria increases in April, May, and June, when the daily average temperature rises from 12 to 22°C and the relative humidity oscillates between 45 and 60% in our area. Bacteria groups' frequency was significantly higher as follows: Staphylococci coagulase negative (>60%) in April, May, and June; Corynebacteriumsp (>33%), Staphylococcus Aureus(>8%), and other Gram-positive bacteria (>2.5%) in May; Streptococcus Pneumoniaeincreases (>3.4%) in March, November, and December; Haemophilussp (>3.4%) in January and April; Gram-negative Cocci (>3%) in April; and other Streptococcussp (>6%) in April, May, and September. Our incidence of rehospitalization for endophthalmitis after cataract extraction in May and June together was 3.37 times higher than in the other months.

Conclusion Conjunctival bacteria of our patients undergoing cataract surgery present a seasonal prevalence pattern, which could be considered as a predisposing condition for having postsurgical endophthalmitis in certain months.