Bacterial contamination of the anterior chamber during phacoemulsification

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In their excellent report about a common concern of clinical ophthalmologists, Leong et al.1 highlighted 2 important issues for clinical ophthalmologists: the conjunctiva as a primary source of bacteria causing postoperative endophthalmitis and the ability of povidone–iodine to reduce the conjunctival bacterial load. Additionally, their view that a negative culture of anterior chamber aspirates does not necessarily imply sterility of the anterior chamber should be an alarm bell for ophthalmologists. The authors believe the causes of the negative culture include the following: only part of the anterior chamber was aspirated; contaminating bacteria have an affinity for adherence to the IOL2; and the small number of bacteria in the sampling was missed. In this regard, the sensitivity and specificity of the polymerase chain reaction (PCR) for bacterial detection is very high.3 However, this is expensive and cannot be practiced by all ophthalmologists. We also agree with Mistlberger et al.,4 who think the surgical technique does not have a significant effect on contamination. However, 2 factors mentioned by Leong et al. raise queries. First, it is difficult to comprehend that no topical antibiotic agents were used before surgery. Second, it is not clear why the culture plates were preserved for 15 days since aerobic bacteria grow in this media within 24 to 48 hours and anaerobic bacteria grow within 48 to 72 hours. Were the authors looking for fungi? We believe one does not expect fungal infection in this type of study, as fungi are rare even as a commensal organism in the conjunctival sac. Further, the authors seem to have used the terms enrichment and enriched synonymously. Enrichment media/broth is a liquid-selective medium that is used to selectively suppress the growth of certain unwanted bacteria, particularly from specimens in which normal flora tends to overgrow pathogens. However, in cultures obtained from conjunctival sacs, the laboratory needs to isolate and identify all types of bacteria (aerobic and anaerobic) without selectively suppressing the growth of any organism. Hence, enriched media, liquid and solid, are used to promote growth of even fastidious bacteria, which could be the source of postoperative infections, as shown by the authors. Culture sensitivity can be increased by enriched culture medium and not an enrichment technique. We conducted a similar microbial evaluation of the conjunctival sac and anterior chamber aspirates in eyes that had conventional extracapsular cataract extraction (ECCE) with poly(methyl methacrylate) (PMMA) intraocular lens (IOL) implantation or phacoemulsification with PMMA IOL implantation. Four interrupted, 10-0 monofilament nylon sutures with buried knots were applied in the ECCE group and 2 sutures, in the phaco group. All patients received topical ciprofloxacin hydrochloride 0.3% 4 times 24 hours before surgery. Periorbital and ocular preparation was carried out with povidone–iodine 5% twice followed by methylated spirit cleaning. Four samples were collected (2 conjunctival swabs and 2 anterior chamber aspirates) as described by Leong et al.,5 and the samples were directly inoculated onto blood agar, chocolate agar, and brain–heart infusion broth. They were incubated at 37°C with 5% to 10% carbon dioxide. The material was also smeared on slides for gram and Giemsa staining. Subcultures were made after bacterial growth was identified by standard methods. A culture was considered positive when there was growth of the same organism on 2 or more media or confluent growth at the site of inoculation on 1 solid medium with consistent direct microscopic findings. The positivity was 16/30 (53%) in the first sample, 2/30 (6%) in the second, 1/30 (3%) in the third, and 4/30 (13%) in the fourth. Coagulase-negative staphylococci were the most common (7) followed by Corynebacterium (5), Escherchia coli (1), streptococci (1), Enterobacter (1), and Acetobacter (1) from the preoperative samples. The anterior chamber aspirates revealed growth of Corynebacterium in both groups (1 each), but no intraocular infection was observed during the 6-month follow-up. We agree with the views of the authors regarding the factors for preventing postoperative endophthalmitis. However, preoperative topical broadspectrum antibiotic agents for 24 hours would be a useful adjunct, especially in patients with poor ocular hygiene. Anita Panda MD Manyank S. Pangtey MD Monoroma Deb MD Vinita Garg MD Badri P. Badhu MD aNew Delhi, India bDharan, Nepal