|Year : 1998 | Volume
| Issue : 4 | Page : 229-232
Microbiological profile of anterior chamber aspirates following uncomplicated cataract surgery
N Venkatesh Prajna, S Sathish, P Chitra Rajalakshmi, Celine George
Aravind Eye Hospital and Post Graduate Institute of Ophthalmology, Madurai, India
N Venkatesh Prajna
Aravind Eye Hospital and PG Institute of Ophthalmology, 1 Anna Nagar, Madurai - 625 020
Source of Support: None, Conflict of Interest: None
Anterior chamber aspirate cultures were done for 66 patients who underwent either an uncomplicated intracapsular cataract extraction, extracapsular cataract extraction with posterior-chamber intraocular lens implantation, or phacoemulsification with posterior-chamber intraocular lens implantation. The aspirate was obtained at the time of wound closure. The aspirates were immediately transferred to the microbiology laboratory where one drop of the aspirate was placed on a glass slide for gram stain, and the remainder was unequally divided and inoculated into blood agar, chocolate agar and thioglycolate broth. The cultures were incubated at 37° C with 5% CO2 and held for 5 days. Of 66 patients 4 (6%), had smear-positive anterior chamber aspirates. None of the aspirates showed any growth on any of the 3 culture media used. None of the eyes in the study developed endophthalmitis. This study concludes that there is no contamination of the anterior chamber by viable bacteria after cataract surgery, irrespective of the mode of intervention.
Keywords: Anterior chamber, aspirate, cataract surgery, culture
|How to cite this article:|
Prajna N V, Sathish S, Rajalakshmi P C, George C. Microbiological profile of anterior chamber aspirates following uncomplicated cataract surgery. Indian J Ophthalmol 1998;46:229-32
There has been considerable debate regarding the sterility of the anterior chamber following uncomplicated cataract surgery. Authors have reported varying incidence of contamination of the anterior chamber following different modes of cataract intervention procedures. These studies assume particular relevance in the context of the ongoing debate regarding the routine use of antibiotics in the irrigating fluids for uncomplicated cataract surgeries. Investigators who believe in the routine use of antibiotics, like gentamicin and vancomycin base their theory on studies which have noted a high intraocular contamination rate. However, a recent directive from the Centers for Disease Control and Prevention discourages the routine use of such antibiotics for routine surgical prophylaxis.
In this study we cultured fluid from the anterior chamber of 66 patients who underwent either an uncomplicated intracapsular cataract extraction (ICCE), extracapsular cataract extraction with posterior chamber intraocular lens implantation (ECCE+PCIOL), or phacoemulsification with posterior chamber intraocular lens implantation (PE+PCIOL). This study was designed to assess the relative frequencies of organisms cultured from the anterior chamber. Our institute provided a good setting for this study on the whole spectrum of cataract-intervention procedures since all 3 procedures mentioned are being performed on a routine basis.
| Materials and Methods|| |
Sixty six patients who met the following criteria were included in the study:
- 1. No history or evidence of previous surgery or penetrating injury to the eye.
- 2. No adnexal, local or systemic infections at the time of surgery.
- 3. No known malignancy or history of intake of steroids and other immunosuppressive agents.
- 4. No intraoperative complications like posterior capsule rupture or vitreous loss.
- 5. No other additional procedures were combined except for the surgery intended (ICCE, ECCE+PCIOL, PE+PCIOL).
All the surgeries were performed by one of the authors at Aravind Eye Hospital, Madurai, Tamil Nadu. Patients were assigned to one of the above- mentioned surgical procedures according to the indications. Patients who were aphakic in the fellow eye and preferred to remain aphakic in the operative eye were assigned to undergo ICCE. The remaining patients were non-randomly assigned to either ECCE+PCIOL or PE+PCIOL.
All the patients were hospitalized the day before surgery and their eyelashes were trimmed at bedside, with a pair of sharp scissors smeared with chloramphenicol ointment. Each patient received a facial scrub and topical chloramphenicol (0.5%) eye drops on an hourly basis for 6 hours, one day before surgery. On the day of surgery the operative eye was dilated with 1% cyclopentolate and 2.5 % phenylephrine eye drops. All the surgeries were performed under local anaesthesia (2% xylocaine with 1 in 200,000 adrenaline) using a O'Briens facial block and a standard retrobulbar block. In the operating room, the periocular area was disinfected with 10% povidone iodine and a drop of 1% povidone iodine was placed in the conjunctival fornices. The eyelids, nose, cheek, forehead and ipsilateral brow were scrubbed thoroughly with 10% povidone iodine. The eyelids were retracted from the operative field by using a sterile plastic self-adhesive drape. A central aperture permitted exposure of the globe, while the eyelids remained exteriorized covered by a plastic drape and secured by a lid speculum.
| Surgical Procedures|| |
After placing a lid speculum and a superior rectus bridle suture, a limbal- based conjunctival flap was fashioned. A 120-140 degree corneoscleral section was made. After a peripheral iridectomy the lens was extracted with the help of cryo probe. The anterior chamber was filled with balanced salt solution. The wound was closed with a minimum of 5 interrupted 8-0 silk sutures. At the end of the surgery 0.1 to 0.2 ml of anterior chamber fluid was aspirated using a sterile disposable tuberculin syringe fitted to a 27 gauge needle.
After placing a lid speculum and a superior rectus bridle suture, a fornix-based conjunctival flap was made. A 120 degree corneo-scleral section was made. 2% Hydroxy propyl methyl cellulose was injected into the anterior chamber and a can opener anterior capsulotomy was completed with the help of a bent 25 gauge needle. The nucleus was delivered by pressure counter pressure technique and cortex aspiration was completed with a manual Simcoe canula. A biconvex posterior chamber intraocular lens was implanted. The wound was closed with a minimum of 5 interrupted 10-0 nylon sutures. At the end of the surgery 0.1 to 0.2 ml of anterior chamber fluid was aspirated using a sterile disposable tuberculin syringe fitted to a 27 gauge needle. The irrigating fluid used was ringer lactate supplemented with 1 in 1000 adrenaline and did not contain any antibiotics.
After placing a lid speculum and a superior rectus bridle suture a 4mm scleral tunnel was fashioned, 3mm from the limbus. PE was performed after a routine capsulorrhexis. The section was then extended by 1.5 mm and a 5 mm optic biconvex lens was implanted in the bag. At the end of the surgery, 0.1-0.2 ml of the anterior chamber fluid was aspirated through the scleral tunnel wound. None of the eyes required sutures for wound closure.
The specimens thus obtained were transported immediately in a sterile container to the microbiology laboratory situated on the same floor as the operating room. In the laboratory, direct smears were made from a drop of the aspirate which was stained with gram stain and examined for the presence of microorganisms. Half the remaining aspirate was inoculated into thioglycolate broth tube, and the rest was inoculated into blood agar and chocolate agar. The culture media used in this study were subjected to standard quality control regimes. The cultures were incubated at 37°C with 5% CO2 and held for 5 days. If microbial growth was evident, the culture media were kept until additional tests could be performed as indicated to identify the cultured microorganism further. Cultures were called positive only if organisms grew in the central inoculated area of the agar within 4 days of inoculation.
These culture media were chosen to maximize isolation and identification of both aerobes and anaerobes alike, in light of the limited volume of inoculum. The increased sensitivity of the thioglycolate broth in microbial recovery serves as a control for potential contaminants recovered from chocolate agar alone. All cultures were interpreted by experienced medical microbiologists.
| Results|| |
A total of 66 patients meeting the inclusion criteria were enrolled in this study. There were 42 (63.6%) men and 24 (36.3%) women. The patients ranged in age from 50 years to 78 years with a mean age of 64 years. 18 (27.2%) of them underwent ICCE, 23 (34.3%) of them underwent ECCE+PCIOL and 25 (37.8%) of them underwent PE+PCIOL. 4 (6%) of 66 anterior chamber aspirates showed microorganisms (3 gram-positive cocci and 1 diphtheroid) in direct smears. None of the anterior chamber aspirates including the smear-positive specimens grew microorganisms in any of the 3 cultures used.
| Discussion|| |
This study was designed to determine the incidence of anterior chamber contamination by viable bacteria, following either ICCE, ECCE+PCIOL or PE+PCIOL. This study documents the absence of viable organisms in the anterior chamber of patients after uncomplicated cataract surgery.
In 1972 Constantaras et al concluded that the anterior chamber remained sterile after intracapsular cataract surgery. This study was performed after ICCE without IOL implantation, and demonstrated one positive anterior chamber aspirate culture out of 100 eyes. This one culture grew S. epidermidis and was considered a contaminant. However this study was refuted by several subsequent studies, based on the fact that Constantaras, Metzger and Frenkel based their conclusion on one drop of anterior chamber aspirate per patient.
Sherwood et al demonstrated that fluid on the external ocular surface entered the anterior chamber during extracapsular cataract surgery. Of 101 patients who underwent extracapsular cataract extraction, 29 had organisms recovered from their anterior chamber fluid at the conclusion of the cataract surgery. Preoperative antibiotics were not used in any of these patients. They however did not delineate the frequency with which the species were recovered from the anterior chamber aspirates.
In 1991 Dickey et al studied 30 patients undergoing uncomplicated cataract surgery with lens implantation and reported a 43% incidence of anterior chamber contamination with coagulase negative staphylococcus being the most common isolate. In their study the isolated organism grew either in chocolate agar or thioglycolate broth, but none of the organisms grew in both media. The same authors concluded in another study in 1994 that gentamicin used in a concentration of 8 μg/ml in the intraocular irrigating fluid can reduce or eliminate the expected intraocular bacterial load after cataract surgery. Gentamicin sulphate, an aminoglycoside, exerts its bactericidal effect on a broad spectrum of gram-negative bacteria. Gentamicin's inaction against gram-positive organisms precludes its use as a single agent in postoperative endophthalmitis prophylaxis. No control group was used in this study. Instead, the author compared this group of patients with those from a previous study. The lack of control group and the microbiologic methods used could produce misleading results.
Samad et al in 1995 studied 103 patients who underwent uncomplicated phacoemulsification and IOL implantation and reported a 5% incidence of positive cultures of the intraocular aspirates. They concluded that there is reduced contamination of the anterior chamber following uncomplicated phacoemulsification and IOL implantation.
Our study was conducted in a large community-based tertiary-care referral hospital which routinely offers ICCE, ECCE+PCIOL and PE+PCIOL to the patient population based on their needs. The incidence of clinically and microbiologically significant anterior chamber contamination (which was defined as growth of the organism within the central inoculated area of the agar within 4 days of inoculation) is lower than any previously documented study involving simultaneous cataract removal and lens implantation., In this study all surgeries were performed by a single surgeon and the preoperative preparation was the same for all patients irrespective of the type of cataract surgery they underwent. None of the patients in this study developed endophthalmitis. All the aspirates were cultured in the microbiology laboratory in Aravind Eye Hospital which handles a large load of infective cases on a routine basis.
The quantity of anterior chamber aspirates obtained in our study was much larger than that obtained in previous studies., We also followed a technique similar to Samad and colleagues, dividing the anterior chamber aspirate unequally (half of the aspirate was inoculated into thioglycolate broth while the reminder was inoculated into blood agar and chocolate agar) and inoculating them into 3 culture media. The staining of the aspirate revealed gram-positive cocci in 3 cases (2 ICCE and 1 ECCE+PCIOL) and diphtheroid in one case (ECCE+PCIOL). None of these aspirates showed any growth on any of the culture media used. Quality control of the culture media used was ensured using injecting test suspensions of common organisms including Pneumococcus and Pseudomonas equivalent in turbidity to a McFarland's 0.5 standard.
Several factors may have contributed to the diminished recovery of microorganisms in this study. These include patient factors, preoperative preparations and microbiologic design. This study design preselected for a healthier patient population by careful attention to the exclusion characteristics.
In conclusion, this study has demonstrated that the anterior chamber may remain sterile during cataract surgery. Strict aseptic preoperative protocol and direct instillation of topical povidone iodine solution on to the globe immediately before surgery may have further enhanced our results.
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