|Year : 1999 | Volume
| Issue : 3 | Page : 185-189
Bacterial contamination of anterior chamber during IOL surgery
R Srinivasan, RA Reddy, S Rene, R Kanungo, MK Natarajan
Department of Ophthalmology, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry, India
Department of Ophthalmology, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry
Source of Support: None, Conflict of Interest: None
PURPOSE: To study the nature and frequency of bacterial contamination during cataract surgery. METHODS: The preoperative smears from the conjunctiva and anterior chamber (AC) fluid aspirates during extra-capsular cataract surgery (ECCE) with posterior chamber intraocular lens (PCIOL) implantation in 40 eyes were analysed for aerobic and anaerobic bacteria. Any change in the bacterial strains isolated before and after cataract surgery was also studied. RESULTS: AC fluid aspirates were positive for bacteria in 15 eyes (37.5%). Coagulase-negative Staphylococcus was the most common aerobe (39.4%) and Propionibacterium acnes the most common anaerobe. Of the 15 cases with positive AC fluid cultures, 6 showed an organism in the AC aspirate different from the conjunctival smear. CONCLUSION: Clinically there was no endophthalmitis in any of the eyes. Factors such as preoperative antibiotic use, the antibacterial properties of aqueous, or low inoculum size could explain this. The preoperative conjunctival smear may not be useful in predicting the AC fluid contamination or outcome of cataract surgery
Keywords: Endophthalmitis, conjunctival flora, anterior chamber contamination
|How to cite this article:|
Srinivasan R, Reddy R A, Rene S, Kanungo R, Natarajan M K. Bacterial contamination of anterior chamber during IOL surgery. Indian J Ophthalmol 1999;47:185-9
|How to cite this URL:|
Srinivasan R, Reddy R A, Rene S, Kanungo R, Natarajan M K. Bacterial contamination of anterior chamber during IOL surgery. Indian J Ophthalmol [serial online] 1999 [cited 2019 Nov 21];47:185-9. Available from: http://www.ijo.in/text.asp?1999/47/3/185/14918
It has been postulated that the anterior chamber (AC) remains sterile during cataract extraction. But more recently other investigators have demonstrated that bacteria routinely enter the AC during cataract surgery., Egger and associates studied the correlation between contamination of the AC and operation technique. Hara and coworkers have investigated the changes in the bacterial strains present before and after cataract surgery and found that preoperative cultures are not a useful guide to predict the organism responsible for postoperative infections. Agarwal et al have concluded that polypropylene haptic intraocular lenses (IOLs) were associated with a significant increase in bacteria in the anterior chamber compared to all Polymethylmethacrylate (PMMA) IOLs.
This study, involving 40 patients, was designed to assess the rate of contamination of the AC at the end of cataract surgery, correlate the risk of contamination with the duration of the surgery, and to establish the relationship, if any, between conjunctival flora and those found in the AC after surgery.
| Materials and Methods|| |
Forty patients who met the following criteria were included
- 1. No history or evidence of previous surgery or penetrating injury to the eye.
- 2. No evidence of systemic or local infection at the time of surgery.
- 3. No evidence of posterior capsular rupture during surgery.
- 4. No additional procedures [except for posterior chamber intraocular lens implantation (PCIOL)].
- 5. No topical or systemic antibiotic therapy 2 weeks prior to surgery.
All patients were hospitalised the day before surgery. The study patients consisted of 24 females and 16 male patients, age ranging from 30-82 years (mean? ± standard deviation = 61.37 years ± 13.22). All patients underwent extra-capsular cataract extraction (ECCE) with PCIOL implantation by the same surgeon (RS).
Preoperative preparation included trimming of eyelashes on the eve of surgery, application of mercurochrome around the eye and topical chloramphenicol the night before and the early morning of the day of surgery. Pupils were dilated with 1% cyclopentolate and 2% homatropine ophthalmic solutions; 0.03% flurbiprofen drops were used for sustained dilatation of pupil. In the operating room, a single point percutaneous peribulbar anaesthesia was given and digital pressure was used to achieve hypotony. The eyelids, nose, cheek, eyebrow and forehead were scrubbed with Savlon (Chlorhexidine gluconate IP 7.5% V/V + Cetrimide IP 15% W/V + Isopropyl Alcohol 6-8% V/V - Jeplon, Jeps Pharma (P) Ltd.) for one minute and with 70% alcohol for another minute. Lid margins were scrubbed with a cotton-tipped applicator. The eye and surrounding skin were irrigated with sterile 0.9% saline solution. The head was draped with a sterile cloth towel and sterile linen drapes were placed over the patient. A conjunctival swab was taken from the lower fornix using a sterile cotton-tipped applicator and inoculated directly on to cooked meat broth. Using a fornix-based conjunctival flap, uncomplicated cataract extraction was performed and a PC IOL was placed in all cases. Sterile compound sodium lactate with epinephrine 1:10000 dilution, and hydroxypropyl methyl cellulose were used during surgery. The viscoelastic substance was removed before closure. At the end of the surgery, a 27-gauge cannula attached to a tuberculin syringe was inserted into the anterior chamber between the sutures; 0.1-0.2 ml of aqueous was aspirated and inoculated directly onto the cooked meat broth. Subconjunctival gentamicin (20 mg) with dexamethasone (2 mg) was injected and the eye closed with pad and bandage. The duration of surgery was noted in each instance.
The inoculated, cooked meat broth was immediately transferred to the microbiology laboratory and incubated at 35°C for 48 hours. Subcultures on to blood agar medium and MacConkey agar were performed. Blood agar plates were incubated at 5-10% CO2 atmosphere. Simultaneous subcultures were made to Brain Heart Infusion Blood Agar (with supplements hemin and vitamin K), phenylethyl alcohol blood agar, and plain blood agar. These plates were incubated in an anaerobic jar with cold catalyst. Evacuation and replacement method was followed to create an anaerobic environment.
The aerobic cultures were examined after 24 hours of incubation. Colony characteristics were studied and cell morphology examined under microscope. The necessary biochemical tests were conducted and the organisms identified as per standard procedures., Anaerobically incubated plates were examined after 48 hours incubation at 35° C. Representative colonies from each type were selected and checked for aerotolerance. The organisms were identified based on colony characteristics, cellspace morphology, and biochemical tests as per standard procedures., All procedures were performed by same technician (MKN).
| Results|| |
All the 40 preoperative conjunctival swabs grew aerobic organisms and 11 (27.5%) grew anaerobic organisms. The organisms isolated and their relative frequency are given in [Table - 1]. In 18 (45%) of 40 eyes, more than one organism was grown (17 aerobic/one anaerobic). Coagulase-negative Staphylococcus was the most common aerobic organism and Propionibacterium acnes was the most common anaerobe isolated. Anterior chamber aspirates were positive for bacteria in 15 (37.5%) eyes (termed as cases with positive cultures). More than one organism was identified in 3 eyes. Coagulase-negative Staphylococcus was the most common organism in the anterior chamber aspirate [Table - 2]. A change in the bacterial strains before and after cataract surgery was evaluated. Of the 15 cases with positive cultures, 6 (40%) showed a different organism in the anterior chamber aspirate than that in conjunctiva. The remaining 9 cases had the same organism in preoperative conjunctival and anterior chamber aspirate cultures.
The bacterial strains identified before and after surgery are listed in [Table - 3]. The mean duration of surgery in culture-positive cases was 48.33 minutes (S.D = 11.127); the mean duration of surgery in culture-negative cases was 45.40 minutes (S.D = 11.07). The difference in the mean duration of surgery was not significant (student's t test). Of the 15 cases with positive cultures 3 presented with excessive uveitis during postoperative follow up which necessitated subconjunctival gentamicin and betamethasone injections and topical antibiotic-steroid drops 8 times a day. In all these eyes the inflammation settled within a week with no recurrence.
| Discussion|| |
Though there has been a dramatic decrease in the incidence of postoperative endophthalmitis over a period of 50 years to 0.1%, it still remains the most devastating complication of intraocular surgery. Two previous studies have reported contamination of anterior chamber during routine uncomplicated ECCE from 25.5% to 43%. [3, 4] Our study with a contamination rate of 37.5% corroborates the above studies. Similar to this studies our study has also documented coagulase-negative Staphylococcus as the most common organism. Coagulase-negative Staphylococcus has been documented to constitute about 38-60% of culture-positive endophthalmitis after cataract surgery., Our study also emphasizes the possible contamination of AC fluid with Propionibacterium acnes, the organism considered significant in anaerobic and chronic postoperative endophthalmitis.
Tsutomu Hara et al in their study on 58 consecutive eyes demonstrated that 67% of the bacterial strains in eyes with positive cultures (4 out of 6 eyes) did not match those found preoperatively in the same eye. Phacoemulsification with IOL implantation was done in this study. In our study 40% of the cases with positive cultures (6 out of 15) showed a different organism from that in the preoperative culture. Of these 2 (case 8 and 34) also grew the organisms seen in the preoperative culture - those are Pseudomonas and Haemophilus normally not present in the conjunctival sac. The possibility of these being contaminants cannot be ruled out.
The reasons to account for this change in bacterial strains could be related to the virulence of the organisms, size of the inoculum, overgrowth of more common organisms in the preoperative specimen, and most significantly, origin from a source other than the patients' own eye.
Correlation between the time taken for surgery and the contamination rate was not statistically significant, contrary to the long-held impression that longer the duration of surgery, the higher the contamination rate. This is further supported by the finding that even with high contamination rates, we did not encounter any case of endophthalmitis. Virulence of the organisms, inoculum size, integrity of the posterior capsule, and antimicrobial properties of the aqueous humour may be the factors that influence progression or non-progression to endophthalmitis.
Three of our cases with positive cultures that developed excessive uveitis could actually represent low-grade infections that got "burnt out" due to intensive topical and subconjunctival antibiotic and steroid therapy. In all these eyes inflammation regressed within a week without recurrence. Of the 3 cases 2 grew same organisms in both conjunctival culture and aqueous culture (Coagulase-negative Staphylococcus + Propionibacterium acnes). In one case the organisms were different (Conjunctival culture: Staphylococcus aureus + Streptococcus faecalis; Aqueous culture: Diphtheroids).
The organism in endophthalmitis is generally exogenous and results from entry of organisms into the eye during surgery. Sources of contamination include instruments, and the infusion fluid. In addition, the conjunctival sac itself normally harbours several commensals. Contamination of the multidose topical preparations used preoperatively could also be a source. Variable contamination rates (up to 30%) have been demonstrated in the topically used medications.,,
Therefore, it is very important to reduce the rate of contamination to prevent even a remote chance of endophthalmitis. To this end modifications that may be needed include:
- 1. Immediate aspiration of the "fluid pool" over the operative ocular surface using an automated aspirating needle to prevent the fluid in the conjunctival sac from entering the anterior chamber.
- 2. Few sutures placed just before irrigation and aspiration (closed- chamber irrigation aspiration) may help to reduce the entry of organisms into the anterior chamber.
From this study it could be concluded that:
- 1. Contamination of the anterior chamber is relatively frequent after ECCE. However, overt (clinically apparent) endophthalmitis is fortunately rare.
- 2. Possible sources of organisms could include periocular tissues and medications used.
- 3. Anaerobic organisms have come to play a significant role and cannot be neglected.
- 4. Preoperative bacterial culture is a poor predictor of the bacterial type found in the aqueous postoperatively.
Studies have been done to compare routine ECCE with PC IOL and small-incision phacoemulsification. Beiji et al and Manners et al did not find a significant difference in culture-positive rates in the two procedures.
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[Table - 1], [Table - 2], [Table - 3]