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Protective Applications, LLC – D.G. Ahearn1

Microbiological Testing for Contact Lens

CareProducts Workshop – Jan 22, 2009

Acanthamoeba

D.G. Ahearn




ARVO Poster 2008




Original 9/12/07Rev. 12/16/07 (REC)D.G. Ahearn

Acanthamoeba keratitis

Acanthamoeba keratitis (AK) is a rare infection of the eye mostly associated with

contact lens wear. The first recognitions of the disease, in the mid-1970’s, followed

traumatic implantation of soil and vegetation, but thereafter to the current date,

about 90% of infections have been reported among soft contact lens users without

histories of overt trauma. The incidence of AK in the USA may be estimated at 1-2

per million per year among contact lens users, at least 10-fold the incidence of

non-users. The CDC, promoted by an apparent upswing of AK in Illinois (Joslin et

al., Am J. Ophthalmol, 142:212, 2006; Am J Ophthalmol, 144:169, 2007),

reviewed over 124 culture proven cases reported to USA eye centers between

2004-2006. The study employed the case controls from the Fusarium outbreak.






CDC noted in July 2007, a 16-fold greater risk of AK associated with the use of

Complete MoisturePlus (CMP) versus other multipurpose solutions. The CMP

solution, as marketed, has not been found to be contaminated (culture positive)

with Acanthamoeba . CMP, as a fresh solution, was nominally inhibitory for

common contact lens case contaminants relative to other MPS in several reports.

When CMP became contaminated in the contact lens case under the stress of

consumer use with poor hygienic practices, chance exposure to cysts or

trophozoites of Acanthamoeba from shower or drain aerosols has been proffered

to result in their amplification. Certain environmental stresses such as addition of

fresh CMP to the case (“topping off”) may induce trophozoites to rapid cyst

formation relative to that observed with other MPS. Studies by Kilvington et al (Eye

& contact Lens. 2008;34:133-139) indicate that this phenomenon is related to the

interaction of the propylene glycol content of the formulation.






Repeated “topping off” followed by evaporation and occasional rinsing of the case

with water, may enhance densities and survival of amoebic cysts in the MPS and

its drying residue. Cysts may be sequestered and protected in the drying film

within cationic cellulose-propylene glycol complexes. Without a manual rubbing

step and with insufficient rinsing ( with fresh CMP or water), trophozoites and

especially cysts may be transferred from the contact lens case via the contact lens

to the eye, increasing the risk of infection. The lens type, strain and density and

form of infectious amoeba propagules, and host immune factors, may all play a

role in the possible development of rare chronic or acute keratitis. Cysts,

particularly, may be irritating to the eye and predispose the eye to a diseased-

state infection with trophozoites.






Rare AK, in general, is associated with contact lens wear but the low incidence of

the disease has discerned among the various MPS (to this date) only use of CMPas a risk factor. Stress conditions that potentiate various MPS (including CMP) to

contamination by Acanthamoeba are still ill-defined. Our preliminary observations,

however, suggest that MPS, in general, are subject to partitioning and phase

separation of inhibitory components upon evaporation. All MPS, if repeatedly driedin the contact lens storage case, leave residues that under rare conditions

harbor amoebae.




MPS may evaporate from a contact lens caseunder ambient conditions and leave a more orless, “dry” film.

Various MPS, as they dry, may produce non-inhibitory residues that support growth or harbormicroorganisms such as Fusarium spp. and

Acanthamoeba.




Dried Films of MPS




Findings at GSU & Emory - Surface Contamination

Outer surface and thread of lens case

ZHANG et al

2006




AMOComplete MoisturePlus

Bausch & LombReNu MultiPlus

AlconOpti-Free Express

CIBA VisionAquify

Drying MPS and Phase Separation ZHANG et al

2008




AMOComplete MoisturePlus

Bausch & LombReNu MultiPlus

AlconOpti-Free Express

CIBA VisionAquify

A

c a n t h a m o e b a

F u s a r i u m

D r y f i l m

Drying MPS and Phase SeparationMPS with distinctive residue patterns after 20-h evaporation microscopic crystals and

humetant morphologies without and with conidia of fusaria and cysts of amoeba.

ZHANG et al 2008




Mature cysts of Acanthamoeba are produced in

“dried MPS” at 12-20 h from inocula of about 105

trophozoites, but were most prominent in CMP anda PBS control.

Cysts often were formed in clusters apparentlydependent in part upon rate of drying and initialaggregation or dispersion of the trophozoites in

the particular MPS.




Cluster of mature cysts

The foreign body sensation reported by

Acanthamoeba keratitis patients may be due to thepresence of cysts. Inflammation caused by cystsmay potentiate recurrent trophozoite invasions of cornea tissue in chronic infections.




Cysts in dried CMP ZHANG et al 2008




Phase Separation – maybe related to Acanthamoeba keratitis?

Findings at GSU & Emory - Dry MPS on surfaces

ARVO 2008




The Presentation

At 2008 ARVO meetings in Florida.

S. Zhang, Ph.D.1

, D.G. Ahearn, Ph.D.1

, R.D. StultingMD, Ph.D. 2, and S.A. Crow, Ph.D. 1

1George State University, 2 Emory University

Preceding slides are an

extension of




“Established and speculative

aspects of rareAcanthamoeba keratitis”

Microbiological Testing for Contact Lens CareProducts Workshop – Jan 22, 2009

Acanthamoeba D.G. Ahearn




1. Repeated rinsing and air drying of a contact lenscase with any MPS results in the eventualdevelopment of residue deposits or a film on andin the contact lens case.

2. The MPS deposits on the case may vary in theiractivity towards microorganisms. Some regions of the film or deposits may support (selective!)microbial growth whereas other regions may beinhibitory.




3. Some of the trophozoites in concentrations (near

105 ml) introduced into fresh and drying MPSundergo lysis while others are induced to producecysts.

4. The number of cysts produced during the dryingperiod vary with the MPS formulation and degreeof drying.

5. Low densities of trophozoites (near 103/ml in currently marketed MPS ) or cysts (near 100/ mlof MPS) do not yield readily recoverabletrophozoites from their 24-48 h dried films. Thevolume of MPS dried (one or two ml) and rate of drying can make a difference in recoveries.




6. The MPS deposits may harbor cysts of

Acanthamoeba (and sometimes trophozoites) overextended periods, either forming a protective andbinding coating or by their hydroscopic nature.The cysts may not be easily rinsed from the

storage case.

7. Recommendation: Clean case with a mild detergent

and hot water with a thorough rinse and air dry.With precaution warnings, an additional rinse withnon-stabilized H2O2 may be instituted. Alternately,a single rinse and air drying step with the MPS

following the cleaning step may be applied. Astandard replacement of the contact lens case isrecommended.




Protective Applications, LLC – D.G. Ahearn

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