Microbial contamination of contact lens care systems

Care practices of contact lens solutions and microbial contamination among wearers in Ghana

PURPOSE

This study sought to assess contact lens solutions care practices, and their microbial contamination among contact lens wearers in Ghana and to profile their antibiotic susceptibility pattern.

METHODS

The study employed a biphasic approach which involved a cross-sectional design that investigated participants' habits related to care for the solutions with a two-part questionnaire and a microbiological analysis of samples of contact lens care solutions of the participants for microbial contamination. A snowball sampling method provided access to 32 different contact lens wearers in four care facilities in Ghana. In most cases, the participants had no pre-existing familial relationship with each other or with the care facilities.

RESULTS

Out of 32 samples of contact lens solutions, 30 were tested for microbial contamination. A total of 23 (76.67 %) samples of contact lens solution were found to be contaminated with Enterobacter sp. (34.80 %), Pseudomonas sp. (21.70 %), Bacilli sp. (21.70 %), Klebsiella sp. (17.20 %), and Escherichia coli (4.60 %). The duration of solution storage in the open bottle and nonadherence to manufacturer instructions for solution storage showed a statistically significant association with microbial contamination (p ≤ 0.05).

CONCLUSION

Contact lens care solutions have been found to harbour multiple antibiotic-resistant bacteria that are potentially pathogenic to the corneal surface. The contamination is associated with some unhealthy solution-care practices among wearers.

A Rare Case of Endophthalmitis with Rhizobium radiobacter, Soon after a Resolved Keratitis: Case Report

BACKGROUND

Rhizobium (Agrobacterium) species are plant aerobic bacteria, which in some cases can produce endophthalmitis in humans after corneal trauma.

CASE PRESENTATION

A 42-year-old female patient presented in the Emergency Department of the Emergency County Hospital of Craiova, Romania, reporting pain, epiphora, and blurry vision in her right eye for about five days. This initial infectious keratitis episode was successfully resolved, but after 20 days she presented again after trauma with a leaf with corneal abscess. In the conjunctival secretion, R. radiobacter was identified. Despite antibiotherapy, the patient's state did not improve, and ultimately the eye was eviscerated.

METHODS

A search was performed in the ProQuest, PubMed, and ScienceDirect databases for the terms Agrobacterium, Rhizobium, radiobacter, and eye. We eliminated non-human studies, editorials and commentaries, and non-relevant content, and excluded the duplicates.

RESULTS

In total, 138 studies were initially obtained, and then we selected 26 studies for retrieval. After the selection process, we ended up including 17 studies in our analysis. Most studies reported R. radiobacter endophthalmitis after ocular surgical procedures or outdoor activities that involve exposure to soil.

CONCLUSION

R. radiobacter is a rare cause of endophthalmitis after eye trauma that generally responds well to usual antibiotherapy, but occasionally can evolve to severe, leading to the loss of the eye.

Multi-purpose Disinfecting Solutions only Partially Inhibit the Development of Ocular Microbes Biofilms in Contact Lens Storage Cases

PURPOSE

Certain ocular resident or pathogenic microbes may remain viable in the presence of multi-purpose disinfectant solutions (MPDSs), subsequently developing biofilms inside contact lens storage cases (CLSCs) which pose a risk of infection to wearers. This study evaluated the formation of ocular microbiota biofilms exposed to three top selling MPDS.

METHODS

Crystal violet assay was carried out for the verification of biofilm formation. The in vitro assays evaluated Pseudomonas aeruginosa UFPEDA 416 and Staphylococcus aureus UFPEDA 02 exposure of 48 h to MPDS, as well as the use of 40 KHz ultrasound at the beginning and with 24 h immersion in the MPDS. Subsequently, in vivo assays evaluated the formation of microbial biofilms on the CLSC walls containing silicone-hydrogel contact lenses immersed in MPDS from 15 healthy volunteer patients, who had been wearing the lenses for 7 days.

RESULTS

Biofilms were inhibited by 26%-98% in the in vitro assays, with a statistically significant difference only for P. aeruginosa UFPEDA 416 exposed to diluted MPDS. Most inhibitions occurred moderately and weakly. In addition, adherent cells were detected in more than 90% of the tests. Biofilm was not inhibited in more than one third of the results, nor was it disturbed, especially with the ultrasound treatments. The average of obtained optical densities at 590 nm was between 0.6 and 0.8 in the in vivo assays. The results were similar between the CLSC right and left wells. There was a correlation between microbial biofilm formation and the type of MPDS tested, with statistical difference between the three treatments.

CONCLUSION

MPDS promoted a partial inhibition of microbial biofilm formation but only one MPDS proved to be more effective in vitro and in vivo. This study, however, could not distinguish the effect of possible errors in the good hygiene practices of the users.

The effect of a compliance enhancement strategy (self‐review) on the level of lens care compliance and contamination of contact lenses and lens care accessories

PURPOSE

The aims were to determine the level of compliance of contact lens wearers, to identify which procedures have highest levels of non-compliance and to study the effectiveness of a compliance enhancement strategy on the level of compliance.

METHODS

The level of compliance for each subject was evaluated with a self-administered questionnaire together with microbiological examination of their contact lenses, lens cases and lens care solutions. The effect of an intervention to improve the level of compliance was determined by a controlled trial. A regular self-review exercise on proper lens handling was given to the test group once every three months for 12 months. The levels of compliance and contamination of contact lenses and lens care accessories between test and control groups were compared at the end of the 12-month period to evaluate the effect of the intervention.

RESULTS

Sixty-five subjects who were experienced contact lens wearers were recruited and 60 completed the study. All showed some degree of non-compliance in the care of their contact lenses and lens accessories. Most (about 60 per cent) were non-compliant with at least six of a total of 15 lens care procedures. The most common non-compliant behaviour among contact lens wearers was associated with the care of the lens case. By the end of the study period, our compliance enhancement strategy did not appear to have had a significant effect on the behaviour of our subjects, except for improvement in the care of lens cases. Compliance for other procedures improved in both test and control groups.

CONCLUSION

All subjects showed some degree of non-compliance and the spectrum of non-compliance was wide. The poorest levels of compliance were associated with care of the lens case, which was also the most frequently contaminated item. Our compliance enhancement strategy showed a significant difference in improvement in compliance between the intervention and control groups only in the care of lens cases.

Effect of povidone iodine contact lens disinfecting solution on orthokeratology lens and lens case contamination and organisms in the microbiome of the conjunctiva

PURPOSE

To compare lens cleaning routines using a povidone iodine-based rigid lens disinfecting solution and its effect on conjunctival colonisation, and lens and lens case contamination.

METHODS

Participants, aged 6-10 years, receiving orthokeratology treatment were randomised to four lens cleaning routines: with and without the use of daily and/or weekly cleaners, which were performed by their parents. Conjunctival colonisation was compared before lens wear and at 1-, 3-, and 6-month after commencement of lens wear. Contamination of lenses and lens cases was investigated at these times. Organisms were identified using MALDI-TOF mass spectrometry.

RESULTS

Of the 76 participants who completed the study, conjunctival colonization was present in 24 (32 %) at baseline. Of the remaining 52 participants, 34 consistently yielded no growth. Participants positive at baseline were statistically more likely to be colonized after commencement of lens wear (p = 0.020). Overall, colonization rate was reduced to 15 % (11/72) after 6-month lens wear, which reached significance for initially colonized participants (p < 0.001). Few cultures yielded potential ocular pathogens, with notably no Pseudomonas aeruginosa. Contamination rates of both lenses and lens cases were also low, with few isolations of ocular pathogens. No significant differences were observed between cleaning regimes for conjunctival colonization or contamination of lenses or cases.

CONCLUSIONS

Disinfection for rigid and ortho-k lens wearers may be effectively achieved with the use of povidone iodine-based solution, apparently regardless of cleaning routine adopted in the current study. The absence of pathogens in the conjunctiva, lenses, and lens cases in the great majority of samples indicates that it can improve the safety of overnight lens wear.

In Vitro Effect of Pitavastatin and Its Synergistic Activity with Isavuconazole against Acanthamoeba castellanii

Acanthamoeba keratitis (AK) can occur in healthy individuals wearing contact lenses and it is a painful, blinding infection of the cornea caused by a free-living ameba Acanthamoeba. Current treatment for AK relies on a combination of chlorhexidine, propamidine isethionate, and polyhexamethylene biguanide. However, the current regimen includes an aggressive disinfectant and in 10% of cases recurrent infection ensues. Therefore, development of efficient and safe drugs is a critical unmet need to avert blindness. Acanthamoeba sterol biosynthesis includes two essential enzymes HMG-CoA reductase (HMGR) and sterol 14-demethylase (CYP51), and we earlier identified a CYP51 inhibitor isavuconazole that demonstrated nanomolar potency against A. castellanii trophozoites. In this study, we investigated the effect of well-tolerated HMGR inhibitors and identified pitavastatin that is active against trophozoites of three different clinical strains of A.castellanii. Pitavastatin demonstrated an EC₅₀ of 0.5 to 1.9 µM, depending on strains. Combination of pitavastatin and isavuconazole is synergistic and led to 2- to 9-fold dose reduction for pitavastatin and 11- to 4000-fold dose reduction for isavuconazole to achieve 97% of growth inhibition. Pitavastatin, either alone or in combination with isavuconazole, may lead to repurposing for the treatment of Acanthamoeba keratitis.

In vivo efficacy of silver-impregnated barrel contact lens storage cases

PURPOSE

This study examined the rate and level of microbial contamination of silver and non-silver (control) barrel contact lens storage cases in vivo.

METHODS

A prospective, single-centre, randomized, double blinded, crossover study was conducted to evaluate the efficacy of silver and control barrel cases used with an Oxipol™-based disinfecting solution over a two-month period. Lens cases were collected, and the frequency, type and level of microbial contamination evaluated using viable culture and standard identification methods. Questionnaires were used to assess the contact lens-related hygiene compliance of the participants.

RESULTS

Forty eight daily contact lens wearers completed the study. Overall, 27 % of silver and 35 % control lens cases (P > 0.05) were contaminated, predominantly with Gram-positive bacteria. Only, 12 % of participants had good compliance, with 46 % having average compliance and 43 % poor compliance. Compliance score was not associated with level of microbial contamination. However, the use of hydrogel lenses in combination with silver cases compared to non-silver barrel cases resulted significantly greater numbers of bacteria colonising cases.

CONCLUSION

The present investigation demonstrated that the use of silver barrel cases does not reduce the overall rate and level of bacterial contamination, but that using hydrogel lenses in combination with silver cases resulted in higher numbers of bacteria isolated from cases.

Bacterial Coaggregation and Cohesion Among Isolates From Contact Lens Cases

Purpose

The aim of this study was to examine cohesion, coaggregation, and coculture between bacteria commonly isolated from contact lens cases.

Methods

Staphylococcus epidermidis, Staphylococcus haemolyticus, Micrococcus luteus, and Acinetobacter radioresistens (two strains each) isolated from contact lens cases of two asymptomatic wearers were used in this study. In the cohesion assay, bacteria were grown, washed, and examined by incubating lens cases with two different types of bacteria sequentially and assessing the number of adhered cells of each isolate. The ability of isolates to interfere with the growth of other isolates was tested by growing strains in cocultures for 24 hours and determining the numbers of cells of individual strains. For coaggregation, equal proportions of two bacterial suspensions were mixed and allowed to coaggregate for 24 hours. Inhibition of coaggregation was tested by the addition of lactose (0.06 M) or sucrose (0.06 M) or pronase.

Results

The initial adhesion of M. luteus or A. radioresistens significantly (P < 0.05) enhanced the subsequent adhesion of the staphylococci. The addition of A. radioresistens in liquid media significantly (P < 0.05) enhanced the growth of staphylococci. S. epidermidis or S. haemolyticus coaggregated with M. luteus or A. radioresistens. The degree of coaggregation varied between 30% and 54%. The highest coaggregation (54% ± 5%) was seen between A. radioresistens 22-1 and S. epidermidis 22-1, isolated from the same lens case. Only lactose or sucrose treatment of staphylococci could partly inhibit coaggregation of some pairs.

Conclusions

Coaggregation, cohesion, and growth promotion may facilitate the process of bacterial colonization of contact lens cases.

Knowledge, Behavior, and Free-Living Amoebae Contamination of Cosmetic Contact Lens Among University Wearers in Thailand: A Cross-Sectional Study

OBJECTIVE

To assess the general knowledge, behavior, and presence of potentially pathogenic amoebae in cosmetic contact lens (CCL) wearers.

METHODS

One hundred CCL asymptomatic wearers were randomly selected. A questionnaire regarding their lens use, and a pair of their CCL was obtained. Identification of free-living amoeba (FLA) strains was based on morphological diagnosis, enflagellation tests (for non-Acanthamoeba strains), and sequencing of the small-subunit rRNA gene fragments.

RESULTS

Most (92%) of the participants surveyed were women, and the average age of the participants was 21.5±0.2 years. The CCL wearers generally showed a moderate (47%) or good (35%) level of knowledge, and good (51%) or excellent (40%) use of CCL. Two CCL samples were positive for Acanthamoeba genotype T3 or Vahlkampfia. The Acanthamoeba-contaminated CCL was from a wearer who used saline for treating lenses, and the Vahlkampfia-contaminated CCL was from a wearer who used CCL while swimming.

CONCLUSIONS

This is the first report of the presence of potentially pathogenic FLA in used CCL from asymptomatic wearers in Thailand. Although there was satisfactory knowledge and practice of lens care use, the public should be aware of CCL contaminated with potentially pathogenic FLA that can directly or indirectly cause keratitis.

In vitro efficacy of corifungin against Acanthamoeba castellanii trophozoites and cysts

Painful blinding keratitis and fatal granulomatous amebic encephalitis are caused by the free-living amebae Acanthamoeba spp. Several prescription eye medications are used to treat Acanthamoeba keratitis, but the infection can be difficult to control because of recurrence of infection. For the treatment of encephalitis, no single drug was found useful, and in spite of the use of a combination of multiple drugs, the mortality rate remains high. Therefore, efficient, novel drugs are urgently needed for the treatment of amebic keratitis and granulomatous amebic encephalitis. In this study, we identified corifungin, a water-soluble polyene macrolide, as amebicidal. In vitro, it was effective against both the trophozoites and the cysts. Transmission electron microscopy of Acanthamoeba castellanii incubated with corifungin showed the presence of swollen mitochondria, electron-dense granules, degeneration of cytoplasm architecture, and loss of nuclear chromatin structure. These changes were followed by lysis of amebae. Corifungin also induced the encystment process of A. castellanii. There were alterations in the cyst cell wall followed by lysis of the cysts. Corifungin is a promising therapeutic option for keratitis and granulomatous amebic encephalitis.

A laboratory assessment of factors that affect bacterial adhesion to contact lenses

Adhesion of pathogenic microbes, particularly bacteria, to contact lenses is implicated in contact lens related microbial adverse events. Various in vitro conditions such as type of bacteria, the size of initial inoculum, contact lens material, nutritional content of media, and incubation period can influence bacterial adhesion to contact lenses and the current study investigated the effect of these conditions on bacterial adhesion to contact lenses. There was no significant difference in numbers of bacteria that adhered to hydrogel etafilcon A or silicone hydrogel senofilcon A contact lenses. Pseudomonas aeruginosa adhered in higher numbers compared to Staphylococcus aureus. Within a genera/species, adhesion of different bacterial strains did not differ appreciably. The size of initial inoculum, nutritional content of media, and incubation period played significant roles in bacterial adhesion to lenses. A set of in vitro assay conditions to help standardize adhesion between studies have been recommended.

Microbial contamination of contact lens care accessories and compliance with care regimens in Nepal

PURPOSE

To determine the rates of microbial contamination and identify contaminants associated with contact lens (CL) care accessories. To investigate self-reported compliance levels with care of CL accessories and its association with contamination level.

METHODS

A total of 46 CL cases and care solutions from asymptomatic soft contact lens wearers were collected. Samples from the CL cases and care solutions were cultured for microbiological identification and enumeration. A questionnaire regarding compliance to care and hygiene procedures were administered to each subject on their visit.

RESULTS

The percentage of microbial contamination for CL cases and care solutions was 50% and 10.9%, respectively. All the contaminants were bacterial. Staphylococcus aureus (37.0%, 17 of 46 cases) and Escherichia coli (8.7%, 4 of 46 cases) were the most common microorganisms detected in CL cases. In care solutions, S. aureus (8.7%, 4 of 46 samples), Pseudomonas aeruginosa (2.2%, 1 of 46 samples) were common contaminants. CL cases and care solutions that were used for <3 months were significantly less contaminated than those used for >3 months (10.9% versus 39.1%, p<0.05). Polyquad and Aldox based MPS solution showed no contamination. Subjects with medium or low compliance had highly significant rates of contaminations both in CL cases and solutions than for subjects with high compliance (p<0.05).

CONCLUSIONS

Nepalese Soft CL wearers are at high risk of developing ocular complications due to high CL case and solution contamination. Frequent replacement of CL cases and solutions, as well as good compliance is recommended to reduce risk of contamination.

Amoebicidal effects of contact lens disinfecting solutions

PURPOSE

To compare the traditional manual hemacytometer method and an automated counter (Vi-cell) to enumerate and distinguish between viable and non-viable amoeba, and to determine the efficacies of contact lens (CL) disinfecting solutions against three species of Acanthamoeba. The efficacies in the presence of a bacterial food source and bovine serum albumin (BSA) were investigated.

METHODS

Four brands of multipurpose solutions and a hydrogen peroxide disinfecting system (Oxysept) for soft CLs, and four disinfecting solutions for Rigid Gas Permeable (RGP) lenses were tested against three species of Acanthamoeba. Page's amoebic saline was included as a negative control and standard solutions of disinfecting agents, 6% hydrogen peroxide and 0.5% chlorhexidine, as positive controls. The effects of the presence of Pseudomonas aeruginosa and BSA on effectiveness were assessed.

RESULTS

None of the CL solutions tested achieved a 1-log reduction in viability of all three Acanthamoeba species within the manufacturer's recommended disinfection times. The presence of P. aeruginosa did not significantly affect disinfecting capacity of multipurpose solution solutions but reduced activity of RGP solutions and the hydrogen peroxide system. BSA reduced trophozoicidal activity of all solutions. Bland and Altman analysis showed good agreement between Vi-cell and hemacytometer.

CONCLUSIONS

The Vi-Cell analyzer offers a simple and effective method of determining amoebicidal activity. Our results show that the CL solutions tested could not satisfactorily kill Acanthamoeba.

The efficacy of stingless bee honey for the treatment of bacteria-induced conjunctivitis in guinea pigs

The efficacy of the conjunctival application of a crude concentration of stingless bee honey (SBH) for the treatment of bacterial conjunctivitis was investigated in an animal model. Bacterial conjunctivitis caused by Staphylococcus aureus or Pseudomonas aeruginosa was induced in Hartley guinea pigs. The conjunctival application of SBH or gentamicin was used for treatment, and the results of this treatment were compared with control values. Inflammatory signs, duration of infection (ie, positive culture), and time for the complete resolution of infection with S. aureus or P. aeruginosa were shortened by the conjunctival application of 1 drop (70 µL) of crude SBH twice daily. The potency of SBH was comparable with that of gentamicin. SBH may be a rational agent for the treatment of infective conjunctivitis in humans; it is inexpensive and commonly available to the rural population.

Contact lens disinfecting solutions antibacterial efficacy: comparison between clinical isolates and the standard ISO ATCC strains of Pseudomonas aeruginosa and Staphylococcus aureus

PURPOSE

To evaluate the disinfectant properties of the three multipurpose contact lens disinfecting solutions available in Iran, against clinical isolates and the standard ISO ATCC strains of Pseudomonas aeruginosa and Staphylococcus aureus, based on the international organization for standardization (ISO) 14729 guidelines.

METHODS

Three multipurpose solutions that were tested were ReNu Multiplus, Solo Care Aqua and All-Clean Soft. The test solutions were challenged with clinical isolates and the standard strains of P. aeruginosa(ATCC 9027) and S. aureus(ATCC 6538), based on the ISO Stand-alone procedure for disinfecting products. Solutions were sampled for surviving microorganisms at manufacturer's minimum recommended disinfection time. The number of viable organisms was determined and log reductions calculated.

RESULTS

All of the three test solutions in this study provided a reduction greater than the required mean 3.0 logarithmic reduction against the recommended standard ATCC strains of P. aeruginosa and S. aureus. Antibacterial effectiveness of Solo Care Aqua and All-Clean Soft against clinical isolates of P. aeruginosa and S. aureus were acceptable based on ISO 14729 Stand-alone test. ReNu MultiPlus showed a minimum acceptable efficacy against the clinical isolate of S. aureus, but did not reduce the clinical isolate by the same amount.

CONCLUSIONS

Although the contact lens disinfecting solutions meet/exceed the ISO 14729 Stand-alone primary acceptance criteria for standard strains of P. aeruginosa and S. aureus, their efficacy may be insufficient against clinical isolates of these organisms.

Adherence of acanthamoeba to lens cases and effects of drying on survival

PURPOSE

To compare the effects of drying the lens case with tissue on the presence of Acanthamoeba with cases left wet and to determine adherence to the lens case of varying concentrations of Acanthamoeba suspensions. The effect of drying on viability of Acanthamoeba in new, used, and soiled lens cases was compared over a 24 h period.

METHODS

New (16) and scratched (16) lens cases were rinsed with a range of Acanthamoeba suspensions. Eight of each group were dried with tissue and the presence of Acanthamoeba was determined in all cases using polymerase chain reaction. To examine effects of drying, forty-two lens case wells were scratched to simulate use and 21 of these were artificially soiled with serum Bovine albumin. These cases and a further 21 unused wells were contaminated with Acanthamoeba (×10/ml) and then left to dry in a cool, dry environment. Three wells of each group were sampled at time 0, 2, 4, 6, 8, 12, and 24 h, and the number of viable Acanthamoeba were determined.

RESULTS

Acanthamoeba were more likely to adhere to used than unused lens cases (p < 0.05). Detection of Acanthamoeba in wiped lens cases was at 2-log dilutions less than in cases left wet for both new and used lens cases. Adherence were significantly different between rinse and rinse/dried cases (p = 0.015). Air drying significantly reduced the numbers of viable amoebic cysts and trophozoites and the effect was time dependent. Survival was significantly higher in used and soiled wells.

CONCLUSIONS

Drying with tissue after rinsing significantly reduces numbers of adhering Acanthamoeba. Acanthamoeba were found to be able to adhere even to new unused cases, so the importance of proper cleaning and disinfection of lens cases cannot be underestimated. Air drying reduces viability but some viable cells were present at 24 h in soiled cases, confirming the role of biofilm in protecting organisms from desiccation.

Contamination of contact lens storage cases of asymptomatic refractive surgery candidates

PURPOSE

To examine the rates of contamination of contact lens storage cases of refractive surgery candidates and compare the growth yields of the traditional method of culturing and a broth-based method.

METHODS

Thirty contact lens storage cases of 16 asymptomatic refractive surgery candidates were studied. Samples from the lens storage case fluid were inoculated into Bactec Peds Plus F broth (Becton Dickinson) and also directly onto blood agar, chocolate agar, and Sabouraud dextrose agar ("traditional method"). Another sample was processed for amoebal contamination. The rate of contamination of cases and the types of pathogens were evaluated for the broth-based and traditional culturing methods. Correlation between right and left storage cases of the same patient was defined as contamination of the two compartments with the same pathogen or pathogens. To avoid statistical bias, only one compartment was included in the study for these patients.

RESULTS

Four storage cases were omitted due to growth correlation between right and left storage cases. Of the remaining 26 storage cases, 16 (61.5%) were found to be contaminated using the broth-based method and 10 (38.5%) using the traditional method (P=.011). High contamination rates were observed regardless of the type of disinfecting solution or type of contact lens used.

CONCLUSIONS

The broth-based method had significantly greater culture yield than the traditional method. The high rates of contamination of contact lens storage cases of refractive surgery patients may put this cohort at greater risk than non-contact lens wearing candidates for developing postoperative infections.

Hygiene compliance in contact lens wearers presenting to an ophthalmic casualty department

Poor compliance with contact lens care regimens is a factor considered important in the development of potentially sight-threatening microbial keratitis. The purpose of this study was to highlight particular areas of non-compliance in contact lens care. One hundred and sixty contact lens wearers, who presented to an ophthalmic casualty department over a period of six months, were surveyed using a self-administered questionnaire. Of the 142 patients who used daily wear lenses, 29 (20 per cent) did not clean/disinfect their contact lenses after every use. Soft contact lens wearers used a wide variety of care regimens, some of which would be ineffective in disinfecting the lenses. The care of the lens case was a particular problem, with only 10 patients (7 per cent) using a regular and effective method of case cleaning. Seventy-three patients (50 per cent) either rarely or never discarded their contact lens solutions 28 days after opening. Of the 128 patients wearing non-disposable lenses, 43 (34 per cent) either rarely or never used enzymatic cleaning tablets to remove protein from their lenses. Tap water, a potential source of microbial contamination, was used for rinsing contact lenses before or after cleaning by 36 patients (25 per cent). The results highlight specific areas where there was deviation from recognised standards of practice for contact lens care. There is a need for contact lens wearers to be re-educated in the care of their lenses. Since pharmacies are a major source of contact lens care products, pharmacy staff could have an important role to play in the counselling of contact lens wearers to help prevent serious ocular pathologies.

Microbial contamination of contact lenses, lens care solutions, and their accessories: a literature review

PURPOSE

A contact lens (CL) can act as a vector for microorganisms to adhere to and transfer to the ocular surface. Commensal microorganisms that uneventfully cohabitate on lid margins and conjunctivae and potential pathogens that are found transiently on the ocular surface can inoculate CLs in vivo. In the presence of reduced tissue resistance, these resident microorganisms or transient pathogens can invade and colonize the cornea or conjunctiva to produce inflammation or infection.

METHODS

The literature was reviewed and used to summarize the findings over the last 30 years on the identification, enumeration, and classification of microorganisms adherent to CLs and their accessories during the course of normal wear and to hypothesize the role that these microorganisms play in CL infection and inflammation.

RESULTS

Lens handling greatly increases the incidence of lens contamination, and the ocular surface has a tremendous ability to destroy organisms. However, even when removed aseptically from the eye, more than half of lenses are found to harbor microorganisms, almost exclusively bacteria. Coagulase-negative Staphylococci are most commonly cultured from worn lenses; however, approximately 10% of lenses harbor Gram-negative and highly pathogenic species, even in asymptomatic subjects. In storage cases, the incidence of positive microbial bioburden is also typically greater than 50%. All types of care solutions can become contaminated, including up to 30% of preserved products.

CONCLUSIONS

The process of CL-related microbial keratitis and inflammation is thought to be preceded by the presence or transfer or both of microorganisms from the lens to the ocular surface. Thus, this detailed understanding of lens-related bioburden is important in the understanding of factors associated with infectious and inflammatory complications. Promising mechanisms to prevent bacterial colonization on lenses and lens cases are forthcoming, which may decrease the incidence of microbially driven CL complications.

Acanthamoeba spp. and bacterial contamination in contact lens storage cases and the relationship to user profiles

Storage cases for contact lenses receive microbiota from the environment, body, and eye, which can form biofilms. These biofilms, in addition to causing discomfort and cloudy vision, can cause local irritation, facilitate the adherence of microorganisms, and lead to infection. The objective of this study was to evaluate the presence of bacteria and Acanthamoeba spp. in the biofilm and solutions in contact lens storage cases, and to assess their relationships to the habits of contact lens wearers. Eighty-one volunteers assembled from the ophthalmology section of a public hospital and from the Central Campus of the federal university, both in the state of Rio Grande do Sul, Brazil, provided the contact lens storage cases. The samples collected were inoculated into sheep blood agar, to isolate bacteria; and into 1.5% non-nutrient agar with an overlayer of Escherichia coli, to isolate free-living amoebas. Of the 81 samples analyzed, 58 (71%) showed bacterial growth and seven (8.6%) were positive for Acanthamoeba spp. The amoebas were identified according to the morphological criteria of Page (A new key to fresh water and soil gymnamoebae, Freshwater Biology Association, Ambleside, UK, 1988) and confirmed by PCR. The storage cases that were positive for Acanthamoeba spp. had a mean of 10(7) UFC/mL and belonged to individuals who had not taken sufficient care with hand washing.

Detection of virulence factors in Pseudomonas aeruginosa strains isolated from contact lens-associated corneal ulcers

PURPOSE

In microbial keratitis associated with contact lens use, Pseudomonas is the most common etiologic agent. The purpose of this study was to report on the microbiological findings of 8 P. aeruginosa strains isolated from contact lens-associated corneal ulcers.

METHODS

Scrapings from contact lens-related corneal ulcers were inoculated for culture. Identification and antibiotic susceptibility testing were performed by using the Vitek system (bioMérieux). The Pseudomonas' ability to form biofilm; produce gelatinase, elastase, and alkaline protease; and adhere to and invade human corneal epithelial cells was studied. Polymerase chain reaction with enterobacterial repetitive intergenic consensus primers (ERIC-PCR) was used to establish clonal relationship between the different isolates.

RESULTS

All the strains showed multiple antibiotic resistance (resistance to 4 or more antibiotics), but all were susceptible to aminoglycosides and fluoroquinolones. Biofilm production was weak in 5 cases and absent in the remaining 3 cases. All isolates were able to produce alkaline protease and gelatinase but not elastase. Adherence to human corneal epithelial cells was poor (0-15 bacteria/cell) in 5 cases and medium (16-60 bacteria/cell) in 3 cases. Five isolates were found to be efficient invaders (>1000 CFU/mL). ERIC-PCR showed 8 different genetic patterns.

CONCLUSIONS

Because multiresistant Pseudomonas isolates are common, we recommend antibiotic susceptibility testing in all cases of Pseudomonas keratitis so that, if there is no response to initial empiric treatment, antibiotics can be modified according to susceptibility results. The ability to produce alkaline protease and gelatinase and invade the corneal epithelium may play a major role in the pathogenesis of contact lens-related P. aeruginosa keratitis. Also, ERIC-PCR seems to be an inexpensive, fast, reproducible, and discriminatory DNA typing tool for effective epidemiologic surveillance of P. aeruginosa isolates potentially transmissible between patients with ocular infections.

Microbial contamination of contact lenses and lens care accessories of soft contact lens wearers (university students) in Hong Kong

PURPOSE

This study aimed to examine the rates of microbial contamination, and identify contaminants associated with contact lenses and lens care accessories used by a group of young contact lens wearers.

METHODS

Collected contact lenses, lens cases, and lens care solutions were studied by bacterial culture. Contamination rates of these samples were recorded and compared with those reported in previous studies.

RESULTS

Of the samples tested, 9% of lens extracts, 34% of case extracts and 11% of solution samples were contaminated with ocular pathogenic microorganisms. Serratia spp., Staphylococcus aureus and coagulase-negative staphylococci were the most common microorganisms isolated. Lens cases were the most frequently contaminated item. Lens cases also yielded the widest range of bacterial isolates. Contact lenses used by occasional wearers were associated with a higher contamination rate. Using either saline or multipurpose solution to rinse lenses before use appeared to be effective in reducing incidence of contamination.

CONCLUSION

Our findings demonstrate that contact lenses and lens care accessories are not well maintained by contact lens wearers. Regular reviews and reinforcement of lens care procedures for the usage and care of contact lenses and lens care accessories is therefore important and essential.

Efficacy of contact lens storage solutions against trophozoite and cyst of Acanthamoeba castellanii strain 1BU and their cytotoxic potential on corneal cells

Acanthamoeba is a free-living amoeba causing a potentially blinding infection of the cornea. Contact lens wearers are most at risk and account for about 95% of cases. We investigated the in vitro effectiveness of 10 contact lens solutions against Acanthamoeba castellanii and their cytotoxicity on corneal cells in vitro. Contact lens solutions were evaluated for their amoebicidal activities using an inverted light microscope. To determine of their cytotoxicity on corneal cells, agar diffusion tests were performed. According to the results obtained from the tests, AVIZOR Aqua Soft Comfort and Elegance(R) showed the best amoebicidal effect on A. castellanii trophozoites. Cysts were still viable after overnight (8 h) exposure. In the case of the cyctotoxic acitivities, All In One Light, Astek, SOLO-Care Aqua, Maxima, and Horien showed no cytotoxicity on the corneal cells. ReNu MultiPlus, AVIZOR Aqua Soft Comfort, Carrera, and Elegance showed mild cytotoxicity on the corneal cells. Plurisol.M presented moderate cytotoxicity on the corneal cells. All commercial solutions examined in this study are the lack of efficacy against A. castellanii. Improvement or development of new contact lens disinfecting systems by the manufacturers is needed to prevent Acanthamoeba keratitis.

Bacterial contamination of ophthalmic solutions used in an extended care facility

AIM

To assess the frequency of contamination of ophthalmic solutions in a long-term care facility and to describe the characteristics of contaminated solutions.

METHODS

One hundred and twenty-three ophthalmic solutions used for patient treatment in a long-term care facility were cultured for bacteria. The culture results were analysed according to the therapeutic class of the solution, how long the bottle had been in use and the appearance of the bottle on visual inspection.

RESULTS

10 (8%) of the 123 multiple-dose solutions were contaminated with bacteria: 4 (50%) of 8 steroid-containing anti-inflammatory solutions, 2 (33%) of 6 combination antimicrobial and steroid-containing anti-inflammatory solutions, 2 (6%) of 34 solutions for treatment of glaucoma, and 2 (4%) of 57 medications for "dry eye". None of the mydriatic, miotic or non-combination antimicrobial solutions was contaminated. Proteus mirabilis was identified in 8 (80%) of the 10 contaminated solutions. Only 30% of the contaminated solution bottles were classified as "dirty" bottles when the bottles were visually inspected. Neither the length of time the solutions had been in use nor the appearance of the bottle predicted contamination.

CONCLUSIONS

8% of ophthalmic solutions used in a long-term care facility were contaminated with bacteria, most frequently Proteus mirabilis. Compared with solutions not containing steroids, steroid solutions were 5.8 times more likely to be contaminated (RR = 5.84, 95% CI: 2.42 to 14.10, p<0.002). The frequent contamination during reuse of certain steroid-containing ophthalmic solutions raises the question of whether single-use solutions might be preferred for these and other classes of ocular drugs.

Comparative study of pH for different saline and multi-purpose contact lens solutions

In this study, we determined the pH of different saline and multipurpose contact lens solutions available on the Spanish market. We examined 10 samples of 14 solutions, seven of which are saline solutions and seven multipurpose ones, from different manufacturers. Both types of solution were found to have significant variations in pH, with values ranging from 6.70 to 7.57 for the saline solutions and 6.84 to 7.63 for the multipurpose solutions. We concluded that the solutions should not affect the ocular physiological performance because their pH values are within the buffering capacity of the eye.

Microbial flora of tears of orthokeratology patients, and microbial contamination of contact lenses and contact lens accessories

PURPOSE

The purpose of this study is to determine if there are changes in the ocular flora of overnight orthokeratology (ortho-k) patients, and the levels of contamination of their lenses and lens accessories, and to correlate compliance with levels of contamination.

METHOD

Normal ocular flora of 41 subjects was determined twice before commencing ortho-k lens wear by culture of the lower conjunctiva. Further specimens were collected on six follow-up visits after beginning lens wear, as were samples from their lenses, cases, and suction holders. A questionnaire on lens care was administered after the fifth visit.

RESULTS

Three subjects provided conjunctival samples yielding Staphylococcus aureus on one occasion before lens wear, one being positive for this organism after beginning lens wear. Of 38 subjects yielding no growth or only normal eye flora before use, 28 remained free of ocular pathogens after beginning lens wear. Only four subjects had positive cultures on more than one occasion after lens wear. There was no significant difference in isolation levels of pathogens with lens wear (p = 0.423). Lens culture of 54% of subjects yielded no growth or normal flora only; lenses of 16 subjects yielded potential pathogens, including three subjects contaminated on more than one occasion. Lens isolates did not match the organisms transiently colonizing the eye. Lens case, the most frequently contaminated item, was associated with lens contamination (p < 0.001), the same organism being isolated from both items in 11 subjects. Lens suction holder was less frequently contaminated. Neither lens case nor suction holder contamination was associated with isolates from the eye. Reported good compliance correlated with lack of contamination in all but one subject. The most frequent breaches in the lens care protocol were failure to clean, disinfect, and replace the lens case.

CONCLUSION

Ocular flora was not altered by ortho-k lens wear over an extended period, and patients remained free of infection. Contaminants identified were generally of a transient nature. Most patients had significant contamination of at least one item, most frequently the lens case. Lens case isolates were significantly associated with those from the lens. The majority of patients reporting good compliance had low or no contamination of their lenses and accessories.

Effect of storage temperatures and time on the efficacy of multipurpose solutions for contact lenses

PURPOSE

To determine the effect of storage time and temperature on the efficacy of four multipurpose solutions for soft contact lenses.

METHOD

Aliquots of multipurpose solutions (OPTI-FREE Express, ReNu MultiPlus, COMPLETE and SOLO-care) stored at different temperatures over a 3-month period, were challenged with contact lens-related ocular pathogens, Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans.

RESULTS

The results showed that OPTI-FREE Express had the best activity against Ps. aeruginosa at all temperatures; ReNu MultiPlus performed well at 25 degrees C; COMPLETE barely achieved activity requirements at all temperatures, and lost efficacy after 2 months. SOLO-care maintained its activity best against Ps. aeruginosa at 30 degrees C. Storage at fridge temperature reduced activity of all solutions. Regardless of storage temperature, activities of all solutions against S. aureus markedly decreased by 2 months. Only OPTI-FREE Express met FDA requirements against C. albicans.

CONCLUSION

Performance of multipurpose solutions is affected by time and temperature of storage. Contact lens users should be aware that the efficacy of opened solutions may not be sustained for as long as 3 months. Manufacturers should reconsider their recommendations to further safeguard the ocular health of contact lens wearers.

Acanthamoeba spp. as agents of disease in humans

Acanthamoeba spp. are free-living amebae that inhabit a variety of air, soil, and water environments. However, these amebae can also act as opportunistic as well as nonopportunistic pathogens. They are the causative agents of granulomatous amebic encephalitis and amebic keratitis and have been associated with cutaneous lesions and sinusitis. Immuno compromised individuals, including AIDS patients, are particularly susceptible to infections with Acanthamoeba. The immune defense mechanisms that operate against Acanthamoeba have not been well characterized, but it has been proposed that both innate and acquired immunity play a role. The ameba's life cycle includes an active feeding trophozoite stage and a dormant cyst stage. Trophozoites feed on bacteria, yeast, and algae. However, both trophozoites and cysts can retain viable bacteria and may serve as reservoirs for bacteria with human pathogenic potential. Diagnosis of infection includes direct microscopy of wet mounts of cerebrospinal fluid or stained smears of cerebrospinal fluid sediment, light or electron microscopy of tissues, in vitro cultivation of Acanthamoeba, and histological assessment of frozen or paraffin-embedded sections of brain or cutaneous lesion biopsy material. Immunocytochemistry, chemifluorescent dye staining, PCR, and analysis of DNA sequence variation also have been employed for laboratory diagnosis. Treatment of Acanthamoeba infections has met with mixed results. However, chlorhexidine gluconate, alone or in combination with propamidene isethionate, is effective in some patients. Furthermore, effective treatment is complicated since patients may present with underlying disease and Acanthamoeba infection may not be recognized. Since an increase in the number of cases of Acanthamoeba infections has occurred worldwide, these protozoa have become increasingly important as agents of human disease.

Effect of a chitin derivative in combination with cleaning and preservation solutions for contact lenses on adherence of fungi

The objective of the study was to evaluate the effect of supplementation of a chitin soluble extract (CSE) to clinically used commercial contact lenses' cleaning/preservation solutions on adherence of Aspergillus niger and Candida albicans to contact lenses. CSE (25 mg ml-1) was added to Solocare or Oxysept. Adherence of A. niger or C. albicans to contact lenses was assessed by exposing lenses to fungi in test solutions and enumeration of fungal colony forming unit. The study included three parts: (i) the disinfecting and adherence-inhibiting effect of Solocare and Oxysept: (ii) the adherence-inhibiting effect of CSE; (iii) the effect of Solocare + CSE or Oxysept + CSE on the fungal adherence to contact lenses. The experiments showed that: (i) Solocare had a significant disinfecting effect on A. niger and C. albicans while that of Oxysept was only minimal. (ii) Neither Solocare nor Oxysept had an inhibitory effect on the fungal adherence. (iii) CSE inhibited significantly the adherence of A. niger and C. albicans. (iv) Addition of CSE to Solocare or Oxysept resulted in almost complete inhibition of adherence Supplementing CSE to lenses' maintenance solutions increases their antifungal potential by adding anti-adherence activity to the disinfecting effect of these solutions, bearing the potential to serve as a prophylactic means.

Risk factors for contact lens associated microbial keratitis

Although the risk of developing contact lens associated microbial keratitis is small, the potential consequences of this condition, such as vision loss, are serious. This paper presents an analysis of the risk factors that have been identified for contact lens induced microbial keratitis, which include extended wear, hypoxia, non-compliance, blepharitis, diabetes mellitus, epithelial trauma, steroid use, therapeutic lens use, tobacco use, and possibly travel to warm climates. By remaining mindful of these risk factors, practitioners can take action and offer advice to patients so as to optimize the safety of contact lens wear.

Adherence of Aspergillus species to soft contact lenses and attempts to inhibit the adherence

The aim of this research was to assess the adherence of various Aspergillus species (A. niger, A. fumigatus, A. flavus) to contact lenses with different water content and to attempt to inhibit the adherence of Aspergillus spp. to the contact lenses by a chitin derivative (CSE). Adherence of Aspergillus spp. to lenses with higher water content was greater. Differences were found between the adherence levels of various Aspergillus species to contact lenses with different water content. CSE significantly inhibits the adherence in vitro of A. niger, A. fumigatus and A. flavus to soft contact lenses. These findings suggest a possibility for prevention of fungal ocular infections caused by Aspergillus spp. in wearers of contact lenses.

Bacillus cereus keratitis associated with contact lens wear

OBJECTIVE

We report the first case of contact lens-related Bacillus cereus keratitis and ulcer associated with B. cereus contamination of the contact lens case. This is also the first study to investigate and establish the genetic identity of an organism isolated from the cornea and contact lens case in a patient with contact lens-associated keratitis.

DESIGN

Case report.

INTERVENTION AND TESTING

Conjunctival swabs and corneal scrapings from the left eye were inoculated for culture. The contact lens case was also cultured. Antibiotic susceptibility testing was determined by agar disk diffusion method. Initial treatment with topical ciprofloxacin and fortified tobramycin was given. Genetic analysis of the bacterial isolates was performed using polymerase chain reaction (PCR) with enterobacterial repetitive intergenic consensus primers (ERIC; ERIC-PCR). Susceptibility of B. cereus to heat and contact lens disinfecting solutions containing hydrogen peroxide, hydrogen peroxide-catalase, polyquaternium-1, and polyaminopropyl biguanide (PAPB) was tested.

MAIN OUTCOME MEASURES

Clinical features, culture results, and antibiotic susceptibility testing were analyzed. The ERIC-PCR amplification products were visualized in ethidium bromide-stained agarose gel. Bacterial growth after exposure to heat and contact lens disinfecting solutions was assessed on blood agar plates.

RESULTS

B. cereus was grown from the conjunctiva, corneal ulcer, and contact lens case. All isolates were sensitive to gentamicin, tobramycin, ciprofloxacin, clindamycin, and vancomycin. The corneal ulcer gradually healed over the next 6 days. Results of ERIC-PCR showed that the isolates from the cornea and contact lens case were indistinguishable, thus demonstrating the source of infecting organism to be the contaminated contact lens case. Exposure to a temperature of 80 degrees C for 20 minutes and incubation with hydrogen peroxide-catalase, polyquaternium-1, and PAPB for the minimum recommended time failed to kill B. cereus. Only exposure to hydrogen peroxide for 4 hours eradicated the organism.

CONCLUSIONS

B. cereus should be considered a possible etiologic agent of contact lens-associated keratitis. Heat and many types of contact lens disinfecting solutions may be ineffective in eradicating B. cereus from contaminated contact lens cases. Only prolonged exposure to hydrogen peroxide appeared to be sporicidal to B. cereus in this study.

Resistance of Pseudomonas aeruginosa isolates to hydrogel contact lens disinfection correlates with cytotoxic activity

One of the most common pathogens in infection of hydrogel contact lens wearers is Pseudomonas aeruginosa, which can gain access to the eye via contamination of the lens, lens case, and lens care solutions. Only one strain per species is used in current regulatory testing for the marketing of chemical contact lens disinfectants. The aim of this study was to determine whether P. aeruginosa strains vary in their susceptibility to hydrogel contact lens disinfectants. A method for rapidly screening bacterial susceptibility to contact lens disinfectants was developed, based on measurement of the MIC. The susceptibility of 35 P. aeruginosa isolates to two chemical disinfectants was found to vary among strains. MICs ranged from 6.25 to 100% for both disinfectants at 37 degrees C, and a number of strains were not inhibited by a 100% disinfectant concentration in the lens case environment at room temperature (22 degrees C). Resistance to disinfection appeared to be an inherent rather than acquired trait, since some resistant strains had been isolated prior to the introduction of the disinfectants and some susceptible P. aeruginosa strains could not be made more resistant by repeated disinfectant exposure. A number of P. aeruginosa strains which were comparatively more resistant to short-term disinfectant exposure also demonstrated the ability to grow to levels above the initial inoculum in one chemical disinfectant after long-term (24 to 48 h) disinfectant exposure. Resistance was correlated with acute cytotoxic activity toward corneal epithelial cells and with exsA, which encodes a protein that regulates cytotoxicity via a complex type III secretion system. These results suggest that chemical disinfection solutions may select for contamination with cytotoxic strains. Further investigation of the mechanisms and factors responsible for resistance may also lead to strategies for reducing adverse responses to contact lens wear.

Acanthamoeba keratitis associated with fungal keratitis

PURPOSE

To report fungal infection complicating Acanthamoeba keratitis.

METHODS

Case report. A 45-year-old woman with contact lens-related bilateral Acanthamoeba keratitis developed corneal ulcer, corneal perforation, and mature cataract in the left eye, which was managed by penetrating keratoplasty, lensectomy, and vitrectomy.

RESULTS

Histopathologic examination of the keratoplasty specimen from the left eye revealed extensive lamellar stromal necrosis with the coexistence of both empty cysts and branching hyphae. Cultures from the keratoplasty specimen grew Scedosporium apiospermum.

CONCLUSION

Keratomycosis caused by S. apiospermum may complicate protracted Acanthamoeba keratitis.

Treatment of postkeratitis fusarium endophthalmitis with amphotericin B lipid complex

PURPOSE

The authors report the first case of Fusarium solani keratitis that progressed to fungal endophthalmitis and was successfully treated with amphotericin B lipid complex (ABLC).

METHOD

The case of a 34-year-old immunocompetent woman who developed a contact lens-related F. solani keratitis requiring emergency penetrating keratoplasty (PKP) was analyzed. The immunocompetent patient developed fungal endophthalmitis (anterior chamber tap positive for F. solani three months after PKP) and was eventually treated with ABLC.

RESULTS

Systemic amphotericin B (total, 0.42 g) and ketoconazole in addition to topical natamycin and amphotericin did not prove to be effective in eradicating the mycosis in the anterior chamber. Under ABLC treatment (total, 8.79 g), the anterior chamber inflammation resolved completely. No recurrence was observed during an 11-month follow-up after treatment was discontinued.

CONCLUSION

ABLC proved to be effective in treating F. solani endophthalmitis. It is an important addition to the ophthalmic armamentarium, and appeared to be a better therapeutic agent than standard amphotericin B in this patient.

Discrimination between clinically relevant and nonrelevant Acanthamoeba strains isolated from contact lens- wearing keratitis patients in Austria

Eighteen cases of Acanthamoeba-associated keratitis among contact lens wearers seen at the Department of Ophthalmology, Karl-Franzens-University, Graz, Austria, between 1996 and 1999 are reviewed. The amoebae were proven to be the causative agents in three patients. The aim of our study was to discriminate between clinically relevant and nonrelevant isolates and to assess the relatedness of the isolates to published strains. Altogether, 20 strains of free-living amoebae, including 15 Acanthamoeba strains, 3 Vahlkampfia strains, and 2 Hartmannella strains, were isolated from clinical specimens. The virulent Acanthamoeba strains were identified as A. polyphaga and two strains of A. hatchetti. To our knowledge this is the first determination of keratitis-causing Acanthamoeba strains in Austria. Clinically relevant isolates differed markedly from nonrelevant isolates with respect to their physiological properties. 18S ribosomal DNA sequence types were determined for the three physiologically most-divergent strains including one of the keratitis-causing strains. This highly virulent strain exhibited sequence type T6, a sequence type not previously associated with keratitis. Sequence data indicate that Acanthamoeba strains causing keratitis as well as nonpathogenic strains of Acanthamoeba in Austria are most closely related to published strains from other parts of the world. Moreover, the results of our study support the assumption that pathogenicity in Acanthamoeba is a distinct capability of certain strains and not dependent on appropriate conditions for the establishment of an infection.

The reculture technique: individualizing the treatment of Acanthamoeba keratitis

PURPOSE

To assess the efficacy of three drugs in different concentrations against different strains of Acanthamoeba using the reculture technique.

METHODS

Cysts and trophozoites were immersed in five separate solutions. The solutions administered included 0.1% and 0.02% polyhexamethylene biguanide (PHMB), 0.1% and 0.02% chlorhexidine, and propamidine isethionate (Brolene). Readings took place after 1, 5, and 24 hours. The cysts and trophozoites were then recultured for an additional period of 48 hours. An effective drug was defined as a medication that inhibited any growth of trophozoites using the reculture technique.

RESULTS

Chlorhexidine at concentrations of 0.1% and 0.02% was the only effective drug against all five strains of Acanthamoeba examined, and no trophozoites were detected on plates immersed with this agent. Only 0.1% chlorhexidine was effective in destroying all cysts in the five strains examined.

CONCLUSION

We found that 0.02% chlorhexidine was efficient in irradicating all trophozoites and 0.1% chlorhexidine was effective in eradicating all cysts in the samples we examined. Therefore, it may be possible that 0.02% chlorhexidine is a good initial treatment in amoebic keratitis. Sensitivity testing, then, may be performed using the reculture technique and specification of therapy can be made accordingly.