Pseudomonas aeruginosa growth in nonsteroidal antiinflammatory solution

Pseudomonas aeruginosa growth in nonsteroidal antiinflammatory solution

1793 CORRESPONDENCE there is no published report assessing bacterial growth in unpreserved eyedrops containing carboxymethylcellulose. Recently, Ist...

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1793

CORRESPONDENCE

there is no published report assessing bacterial growth in unpreserved eyedrops containing carboxymethylcellulose. Recently, Ista Pharmaceuticals, Inc., sponsored a study designed to investigate the ability of 3 bacterial strains (Staphylococcus epidermidis, Staphylococcus aureus, and P aeruginosa) and one fungal isolate (Candida albicans), all obtained from the American Type Culture Collection (Manassas, Virginia, USA), to grow in Acuvail.A Multiple test tubes of Acuvail were inoculated with S epidermidis (ATCC 14990), S aureus (ATCC 6538), P aeruginosa (ATCC 15442), and C albicans (ATCC 10231) to achieve a target concentration of approximately 100 colonyforming units (CFU)/mL. The tubes were incubated at 25 C, and samples were aseptically removed at 0, 24, and 36 hours. The samples were cultured to enumerate the population at each time point. The 0 hour served as the inoculum control. Pseudomonas aeruginosa was too numerous to count after 24 hours, and the plate was confluent with growth after 36 hours (Table 1). For the other 3 organisms, the number of CFU/mL after 24 and 36 hours was similar to that at the 0 hour. Staphylococcus epidermidis, S aureus, and C albicans did not survive and replicate in the Acuvail solution to the same degree as P aeruginosa. In a second experiment, multiple test tubes of Acuvail were inoculated with P aeruginosa to achieve a final concentration of 75 CFU/mL and incubated at 20 C to 25 C. At 0, 6, and 12 hours, samples were aseptically removed and cultured to enumerate the population at each time point. Pseudomonas aeruginosa increased from an average of 75 CFU/mL at 0 hour to 118 CFU/mL after 6 hours and approximately 516 CFU/mL after 12 hours, which represents a 57% increase after 6 hours and a 588% increase after 12 hours (Table 2). Under these experimental conditions, Acuvail appears to be supporting P aeruginosa growth, suggesting that if the solution were contaminated

REFERENCES 1. Alpins NA. A new method of analyzing vectors for changes in astigmatism. J Cataract Refract Surg 1993; 19:524–533 2. Jaffe NS, Clayman HM. The pathophysiology of corneal astigmatism after cataract extraction. Trans Am Acad Ophthalmol Otolaryngol 1975; 79:OP615–OP630 3. Shirayama M, Wang L, Weikert MP, Koch DD. Comparison of corneal powers obtained from 4 different devices. Am J Ophthalmol 2009; 148:528–535 4. Elliott M, Simpson T, Richter D, Fonn D. Repeatability and comparability of automated keratometry: the Nikon NRK-8000, the Nidek KM-800 and the Bausch and Lomb keratometer. Ophthalmic Physiol Opt 1998; 18:285–293 5. Menassa N, Kaufmann C, Goggin M, Job OM, Bachmann LM, Thiel MA. Comparison and reproducibility of corneal thickness and curvature readings obtained by the Galilei and the Orbscan II analysis systems. J Cataract Refract Surg 2008; 34:1742–1747 6. Alpins N. Astigmatism analysis by the Alpins method. J Cataract Refract Surg 2001; 27:31–49 7. Kaufmann C, Thiel MA, Esterman A, Dougherty PJ, Goggin M. Astigmatic change in biaxial microincisional cataract surgery with enlargement of one incision: a prospective controlled study. Clin Exp Ophthalmol 2009; 37:254–261 8. Kaufmann C, Krishnan A, Landers J, Esterman A, Thiel MA, Goggin M. Astigmatic neutrality in biaxial microincisional cataract surgery. J Cataract Refract Surg 2009; 35:1555–1562

Pseudomonas aeruginosa growth in nonsteroidal antiinflammatory solution Antonio Pinna, MD Pseudomonas aeruginosa endophthalmitis is among the most serious complications of cataract surgery.1 The condition is often associated with a poor visual prognosis. Acuvail is a new nonsteroidal antiinflammatory ophthalmic solution for the treatment of pain and inflammation following cataract surgery. It contains ketorolac tromethamine 0.45% as an active ingredient and carboxymethylcellulose as an inactive ingredient; it is preservative free and packaged in unit-dose vials. Experimental evidence indicates that carboxymethylcellulose can support the growth of some strains of Pseudomonas and Escherichia coli.2–4 To my knowledge,

Table 1. Pseudomonas aeruginosa growth in Acuvail after 24- and 36-hour incubation. 0 Hour* (CFU/mL) Test Organism Pseudomonas aeruginosa Negative control Positive control (qualitative)

Plate 1

Plate 2

Average

57 0

54 0

56 !1

24 Hours (CFU/mL) Plate 1

Plate 2

Average

TNTC TNTC TNTC 0 0 !1 Pseudomonas aeruginosa C (growth)

CFU Z colony-forming units; TNTC Z too numerous to count *Inoculum control C Estimated count

J CATARACT REFRACT SURG - VOL 36, OCTOBER 2010

36 Hours (CFU/mL) Plate 1

Plate 2

Average

Confluent 0

Confluent 0

Confluent !1

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CORRESPONDENCE

Table 2. Pseudomonas aeruginosa growth in Acuvail after 6- and 12-hour incubation. 0 Hour* (CFU/mL) Test Organism Pseudomonas aeruginosa Negative control Positive control (qualitative)

6 Hours (CFU/mL)

12 Hours (CFU/mL)

Plate 1

Plate 2

Average

Plate 1

Plate 2

Average

Plate 1

Plate 2

Average

78

72

75

106

130

118

0

0

!1

O300 (504)C 0

O300 (528)C 0

O300 (516)C !1

0 0 !1 Pseudomonas aeruginosa C (growth)

CFU Z colony-forming units *Inoculum control C Estimated count

with P aeruginosa during use, the organism would survive and replicate over time. Reuse of unit-dose vials is relatively common in patients with ocular surface problems. Since each vial contains approximately 6 to 8 drops, patients are often tempted to use one vial for several doses to save money. The results of the above-mentioned studies suggest that reuse of a single vial of Acuvail for 6 hours or more in the postoperative period is cause for great concern because of the risk for microbial contamination and growth in the unpreserved solution inside the vial. These experiments also suggest that carboxymethylcellulose might support P aeruginosa growth. Further studies are necessary to assess the ability of Pseudomonas to grow in other preservative-free eye products containing carboxymethylcellulose. As recommended by the manufacturer, postcataract-surgery patients should be instructed that the solution from one single-use vial of Acuvail is to be used immediately after opening; the remaining content should be discarded after administration. Noncompliance with these recommendations (ie, reuse of an open vial) may result in contamination of the solution with ocular pathogens, such as Pseudomonas, which may cause sight-threatening infections, such as postoperative endophthalmitis or keratitis.1,5 REFERENCES 1. Pinna A, Usai D, Sechi LA, Zanetti S, Jesudasan NCA, Thomas PA, Kaliamurthy J. An outbreak of post-cataract surgery endophthalmitis caused by Pseudomonas aeruginosa. Ophthalmology 2009; 116:2321–2326. Available at: http://download. journals.elsevierhealth.com/pdfs/journals/0161-6420/PIIS01616 4200900606X.pdf. Accessed May 2. Hazlewood GP, Laurie JI, Ferreira LMA, Gilbert HJ. Pseudomonas fluorescens subsp. cellulosa: an alternative model for bacterial cellulase. J Appl Bacteriol 1992; 72:244–251. Available at: http://www3.interscience.wiley.com/cgi-bin/fulltext/119988884/ PDFSTART. Accessed May 28, 2010 3. Bolam DN, Ciruela A, McQueen-Mason S, Simpson P, Williamson MP, Rixon JE, Boraston A, Hazlewood GP, Gilbert HJ.

Pseudomonas cellulose-binding domains mediate their effects by increasing enzyme substrate proximity. Biochem J 1998; 331: 775–781. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/ PMC1219417/pdf/9560304.pdf. Accessed May 28, 2010 4. Kim Y-S, Jung H-C, Pan J-G. Bacterial cell surface display of an enzyme library for selective screening of improved cellulase variants. Appl Environ Microbiol 2000; 66:788–293. Available at: http://aem.asm.org/cgi/reprint/66/2/788. Accessed May 28, 2010 5. Pinna A, Usai D, Sechi LA, Molicotti P, Zanetti S, Carta A. Detection of virulence factors in Pseudomonas aeruginosa strains isolated from contact lens-associated corneal ulcers. Cornea 2008; 27:320–326

OTHER CITED MATERIAL A. ISTA Technical Bulletin 120909

Increasing the safety of cataract surgery of hard lenses: Phaco-on-top technique Gysbert van Setten, MD, PhD Online Video In hard, loose crystalline lenses, phacoemulsification of the fourth (last) quadrant is the most tricky part of the entire surgery. Most complications occur then, severely impairing the surgical outcome. To overcome this problem, a technique called phaco on top has been introduced. In this technique, the final lens residue is phacoemulsified after the intraocular lens (IOL) is implanted. The technique is an improvement over earlier techniques in which the surgeon approaches the last fragments more anteriorly, which could lead to lesions of the iris, among other problems.1 In the phaco-on-top technique, the IOL is inserted under/behind the nucleus residue using a standard technique. A Sinskey hook or similar device is then introduced via the paracentesis, gently stabilizing the IOL in position. The phacoemulsification tip is introduced into the capsular bag. Initially, the hard lens material (nucleus) is pushed close to the edge of the IOL, out of the center of the IOL (Figure 1, a). Then, the IOL is gently tilted so there is a safety

J CATARACT REFRACT SURG - VOL 36, OCTOBER 2010