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

Contamination of fresh vegetables in municipal stores with pathogenic Acanthamoeba genotypes; a public health concern

Acanthamoeba spp. cause keratitis and encephalitis, and are a proper carrier of foodborne pathogens. A total of 70 samples including garden cress, chives, mint, parsley, and basil were collected. Samples were cultured onto a 2% non-nutrient agar medium. The cultures were analyzed using morphological and molecular techniques. In total, 18 (25.7%) out of 70 samples were positive including garden cress 10/22 (45.45%), chives 3/12 (25%), mint 2/13 (15.38%), basil 2/13 (15.38%), and parsley 1/10 (10%). The diagnostic fragment 3 was successfully sequenced in 15 samples and represented 11 (73.3%) T4, three (20%) T5, and one T9 genotypes. In addition, three, two, and one strains, belonging to the genotypes T4, T5, and T9 were ranked highly pathogenic. This is the first study reporting contamination of the most commonly consumed fresh vegetables with pathogenic Acanthamoeba genotypes. Our findings signify the public health concerns due the contamination of vegetables in municipal public markets.

A history of over 40 years of potentially pathogenic free-living amoeba studies in Brazil - a systematic review

Free-living amoeba (FLA) group includes the potentially pathogenic genera Acanthamoeba, Naegleria, Balamuthia, Sappinia, and Vermamoeba, causative agents of human infections (encephalitis, keratitis, and disseminated diseases). In Brazil, the first report on pathogenic FLA was published in the 70s and showed meningoencephalitis caused by Naegleria spp. FLA studies are emerging, but no literature review is available to investigate this trend in Brazil critically. Thus, the present work aims to integrate and discuss these data. Scopus, PubMed, and Web of Science were searched, retrieving studies from 1974 to 2020. The screening process resulted in 178 papers, which were clustered into core and auxiliary classes and sorted into five categories: wet-bench studies, dry-bench studies, clinical reports, environmental identifications, and literature reviews. The papers dating from the last ten years account for 75% (134/178) of the total publications, indicating the FLA topic has gained Brazilian interest. Moreover, 81% (144/178) address Acanthamoeba-related matter, revealing this genus as the most prevalent in all categories. Brazil’s Southeast, South, and Midwest geographic regions accounted for 96% (171/178) of the publications studied in the present work. To the best of our knowledge, this review is the pioneer in summarising the FLA research history in Brazil.

Comparison of compliance with care procedures performed by orthokeratology wearers and their parents and factors affecting compliance

PURPOSE

To compare the levels of compliance with care routines of orthokeratology (ortho-k) wearers and their parents and to identify factors affecting compliance in a hospital setting in Chengdu, China.

METHODS

Patients who had worn ortho-k lenses for at least one month were invited to participate in a survey on compliance. Wearers or their parents were required to complete a questionnaire to determine their compliance with hand hygiene, ortho-k lenses and accessory care procedures.

RESULTS

A total of 200 wearers, 78 male wearers and 122 female wearers, median age 12 (range 8-18) years were enrolled. Except for use of lens solution, the percentage of participants reporting total compliance with all procedures did not differ significantly between lens wearers and their parents. However, compliance for some items was significantly higher when performed by parents p < 0.001-0.01). 'Eye care practitioner provided instructions' was a significant protective factor for most procedures (p < 0.001-0.04). Age and sex were significant risk factors for some items (p < 0.001-0.04; p = 0.03-0.04, respectively), with girls having higher compliance than boys. 'Parental supervision' was a significant protective factor for some items (p = 0.02-0.04) when wearers performed the procedures themselves. When parents performed lens care procedures, only 'eye care practitioner provided instructions' was a significant variable (p = 0.001-0.04).

CONCLUSION

Some degree of non-compliance was noted in the majority of ortho-k wearers, particularly for the care of the lens case and suction holder. Compliance with care of some items was higher when performed by parents. Regular reinforcement of care procedures by practitioners is important, especially for older and male lens wearers. Parental supervision is necessary when children perform lens care procedures themselves, even for older wearers.

The role of Acanthamoeba spp. in biofilm communities: a systematic review

Acanthamoeba spp. have always caused disease in immunosuppressed patients, but since 1986, they have become a worldwide public health issue by causing infection in healthy contact lens wearers. Amoebae of the Acanthamoeba genus are broadly distributed in nature, living either freely or as parasites, and are frequently associated with biofilms throughout the environment. These biofilms provide the parasite with protection against external aggression, thus favoring its increased pathogeny. This review aims to assess observational studies on the association between Acanthamoeba spp. and biofilms, opening potential lines of research on this severe ocular infection. A systematic literature search was conducted in May 2020 in the following databases: PubMed Central^®/Medline, LILACS, The Cochrane Library, and EMBASE^®. The studies were selected following the inclusion and exclusion criteria specifically defined for this review. Electronic research recovered 353 publications in the literature. However, none of the studies met the inclusion criterion of biofilm-producing Acanthamoeba spp., inferring that the parasite does not produce biofilms. Nonetheless, 78 studies were classified as potentially included regarding any association of Acanthamoeba spp. and biofilms. These studies were allocated across six different locations (hospital, aquatic, ophthalmic and dental environments, biofilms produced by bacteria, and other places). Acanthamoeba species use biofilms produced by other microorganisms for their benefit, in addition to them providing protection to and facilitating the dissemination of pathogens residing in them.

Effect of Hygiene Procedures on Lens Case Contamination with Povidone-Iodine or Multipurpose Disinfecting Solutions

SIGNIFICANCE

A multipurpose disinfecting solution (MPDS), which contains povidone-iodine (PI) as a disinfectant, has high disinfecting efficacy not only on planktonic bacterium but also on the case biofilms. The addition of case hygiene practice removed more bacteria from cases than MPDS alone.

PURPOSE

This study compared the ability of two MPDSs, one containing PI and another containing polyaminopropyl biguanide and polyquaternium, to reduce bacterial numbers in solution or adhered to the cases following case hygiene procedures.

METHODS

Bacterial strains (Delftia acidovorans, Pseudomonas aeruginosa, Stenotrophomonas maltophilia, Serratia marcescens, Staphylococcus aureus, and Staphylococcus epidermidis) were exposed to the MPDSs for the recommended disinfection times, and the viable number evaluated according to ISO 14729. Cases were inoculated with bacterial strains and incubated for 24 hours to allow for biofilm formation. Cases were disinfected with both disinfecting solutions for 4 hours and rinsed, followed by recapping or air-drying, or tissue-wiping and air-drying for 18 hours. The number of survivors was counted using standard culture techniques.

RESULTS

Both products exceeded the recommended 3-log reduction against planktonic bacteria. Regarding biofilm, after rinsing and recapping wet, the numbers of D. acidovorans (mean difference [95% confidence interval] log10 colony-forming units per case, -2.9 [0.8 to -4.6], P < .01), P. aeruginosa (-2.0 [0.5 to -3.1], P < .01), S. marcescens (-1.7 [0.8 to -3.5], P < .05), and S. epidermidis (-2.1 [0.6 to -3.5], P < .05) in PI cases were significantly lower than in the dual-disinfectant MPDS storage cases. After air-drying, the PI storage cases had significantly lower numbers of S. maltophilia (-2.6 [0.6 to -4.0], P < .01), D. acidovorans (-1.6 [0.7 to -3.3], P < .05), and S. aureus (-1.6 [0.7 to -3.1], P < .05). The addition of tissue-wiping reduced the bacterial numbers in the MPDS storage cases to levels in the PI storage cases.

CONCLUSIONS

Contact lens users should be recommended to tissue-wipe and air-dry their lens storage cases after disinfection with regular MPDS.

Development of a contact Lens risk survey

PURPOSE

To describe the development and report psychometric properties of the Contact Lens Risk Survey (CLRS) to identify patients at risk for soft contact lens-related complications.

METHODS

Psychometric properties of the CLRS, a web-based survey with branching logic, were determined using data from 5 multi-site fieldings (n = 1059), including re-fielding to sub groups. Responses from participants with and without an active red eye were used to identify risk factors of a red eye event and calculate an overall risk score. A 6th fielding of the CLRS (n = 171) was used to assess discriminate validity.

RESULTS

Participants needed 11-12 min to complete the survey with a negligible difference by age. Internal consistency was excellent (Cronbach's α ≥ 0.70) for 3 of the 5 constructs identified by factor analysis. Twelve of the 17 survey items exhibited excellent within-subject repeatability (Kappa ≥ 0.61). Between-subject agreement, assessed in 18-25 year olds, was high for the majority of items, suggesting good generalizability across different populations of SCL wearers. The ability of the model using individual items of the CLRS to discriminate Controls and participants with a red eye was good with an area under the curve of 0.779.

CONCLUSION

The CLRS tool is a repeatable and valid instrument to standardize documentation of demographic, behavior, and exposure factors which appear to drive the greatest risk of a contact lens related red eye event.

Adhesion of Pseudomonas aeruginosa, Achromobacter xylosoxidans, Delftia acidovorans, Stenotrophomonas maltophilia to contact lenses under the influence of an artificial tear solution

Corneal infection is a devastating sight-threatening complication that is associated with contact lens (CL) wear, commonly caused by Pseudomonas aeruginosa. Lately, Achromobacter xylosoxidans, Delftia acidovorans, and Stenotrophomonas maltophilia have been associated with corneal infection. This study investigated the adhesion of these emerging pathogens to CLs, under the influence of an artificial tear solution (ATS) containing a variety of components commonly found in human tears. Two different CL materials, etafilcon A and senofilcon A, either soaked in an ATS or phosphate buffered saline, were exposed to the bacteria. Bacterial adhesion was investigated using a radio-labeling technique (total counts) and plate count method (viable counts). The findings from this study revealed that in addition to P. aeruginosa, among the emerging pathogens evaluated, A. xylosoxidans showed an increased propensity for adherence to both CL materials and S. maltophilia showed lower viability. ATS influenced the viable counts more than the total counts on CLs.

Evaluation of prevention and disruption of biofilm in contact lens cases

PURPOSE

The presence of biofilm in the lens case has been shown to be a risk factor for contamination of lenses and consequently microbial keratitis. This study aimed to evaluate effectiveness of solutions for rigid contact lenses in prevention and disruption of biofilm in lens cases and methods for biofilm detection.

METHOD

This study adopted a stepwise approach to evaluate effectiveness of four rigid lens disinfecting solutions against biofilm. These included two polyhexamethylene bigiuanide (PHMB) solutions and a chlorhexidine/PHMB-based solution, as well as a novel povidone-iodine formulation. The presence of biofilm following exposure to the solutions was assessed using both crystal violet (CV) staining and MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) viability assay, taking into account the effect of lens case design. Three lens case designs, conventional flat, large bucket type, and cylindrical cases, were investigated for the ability to trap stain and allow biofilm formation.

RESULTS

Considerable differences were noted between solutions in their ability to prevent and disrupt biofilm (p < 0.001). Lens case design greatly influenced optical density (OD) measurements even in negative controls, as cylindrical cases trapped more stain, increasing OD readings. Correcting for this factor reduced variations, but could not differentiate between residues and biofilm. MTT assay revealed that both povidone-iodine and chlorhexidine-containing solutions could effectively kill > 95% of organisms, whilst PHMB-based solutions were less effective with up to 55% of staphylococci and 41% of Pseudomonas surviving at 24 h.

CONCLUSION

Biofilm can rapidly form in lens cases and may not be killed by disinfecting solutions. Of the solutions tested, none were able to prevent biofilm formation or disrupt established biofilm, but those containing chlorhexidine or povidone iodine were able to penetrate the biofilm and kill organisms. Assessment of biofilm by CV assay may be confounded by lens case design. Whilst CV assay can demonstrate presence of biofilm, this technique should be accompanied by viability assay to determine bactericidal activity.

Review of Contact Lens-Related Complications

The purpose of this article is to provide a review of existing literature describing complications with contemporary contact lenses and their management. It is envisioned that this will serve as a useful summary of noninfectious and infectious complications associated with contact lens wear.

Effectiveness of sampling methods employed for Acanthamoeba keratitis diagnosis by culture

PURPOSE

This retrospective, observational study was designed to evaluate the effectiveness of the sampling methods commonly used for the collection of corneal scrapes for the diagnosis of Acanthamoeba keratitis (AK) by culture, in terms of their ability to provide a positive result.

METHODS

A total of 553 samples from 380 patients with suspected AK received at the Parasitology Section of the Public Health Institute of Chile, between January 2005 and December 2015, were evaluated. A logistic regression model was used to determine the correlation between the culture outcome (positive or negative) and the method for sample collection. The year of sample collection was also included in the analysis as a confounding variable.

RESULTS

Three hundred and sixty-five samples (27%) from 122 patients (32.1%) were positive by culture. The distribution of sample types was as follows: 142 corneal scrapes collected using a modified bezel needle (a novel method developed by a team of Chilean corneologists), 176 corneal scrapes obtained using a scalpel, 50 corneal biopsies, 30 corneal swabs, and 155 non-biological materials including contact lens and its paraphernalia. Biopsy provided the highest likelihood ratio for a positive result by culture (1.89), followed by non-biological materials (1.10) and corneal scrapes obtained using a modified needle (1.00). The lowest likelihood ratio was estimated for corneal scrapes obtained using a scalpel (0.88) and cotton swabs (0.78).

CONCLUSION

Apart from biopsy, optimum corneal samples for the improved diagnosis of AK can be obtained using a modified bezel needle instead of a scalpel, while cotton swabs are not recommended.

Acanthamoeba spp. in Contact Lenses from Healthy Individuals from Madrid, Spain

Purpose

Acanthamoeba keratitis (AK) is a painful and potentially blinding corneal infection caused by Acanthamoeba spp. In Madrid, environmental studies have demonstrated a high presence of these free-living amoebae in tap water. Since most of AK cases occur in contact lenses (CL) wearers with inadequate hygiene habits, the presence of Acanthamoeba in discarded CL has been studied and compared with other common etiological agents of keratitis, such as Pseudomonas aeruginosa and Staphylococcus aureus.

Methods

One hundred and seventy-seven healthy individuals from Madrid contributed their discarded CL and answered a questionnaire on hygiene habits. DNA was extracted from the CL solution and analyzed by real-time PCR for Acanthamoeba, Pseudomonas aeruginosa and Staphylococcus aureus. These CL and their solutions were also cultured on non-nutrient agar to isolate Acanthamoeba.

Results

Among the 177 samples, Acanthamoeba DNA was detected in 87 (49.2%), P. aeruginosa DNA in 14 (7.9%) and S. aureus DNA in 19 (10.7%). Cultivable amoebae, however, were observed in only one sample (0.6%). This isolate was genotyped as T4. The habits reported by this CL owner included some recognized risk factors for AK, but in this study only the practice of “not cleaning the CL case” presented some statistical significant association with Acanthamoeba DNA presence. Detection of the investigated bacterial DNA did not demonstrate statistical significant association with the studied practices, but the presence of P. aeruginosa revealed a possible inhibition of Acanthamoeba in these samples.

Conclusions

The PCR results suggest a high presence of Acanthamoeba spp. in healthy CL wearers from Madrid, but we can assume that CL solutions are properly disinfecting the CL since only 1.1% of the positive PCR samples correspond to viable amoebae and, after four years, only one participant reported stronger ocular problems. Nevertheless, more studies are necessary to corroborate this hypothesis.

Amoebicidal efficacy of a novel multi-purpose disinfecting solution: first findings

Free-living amoebae of the genus Acanthamoeba can cause a sight-threatening corneal infection, Acanthamoeba keratitis, mostly in contact lens wearers. The use of ineffective contact lens disinfecting solutions is one of the most important risk factors for this infection. This study concerns a new multi-purpose contact lens disinfecting solution, OPTI-FREE® PureMoist®, tested for its efficacy against Acanthamoeba trophozoites and cysts by using the most probable number technique for amoebic enumeration. Acanthamoeba castellanii ATCC 50373 and an environmental strain of Acanthamoeba genotype T4 isolated from tap water in Istanbul were used during the experiments. OPTI-FREE® PureMoist® achieved total kill (more than a 3-log reduction) of trophozoites of both strains before the manufacturer-recommended disinfection time (6h). In contrast, this solution had limited cysticidal activity against the ATCC strain but more against the environmental strain, with log reductions of 0.75 and 2.20, respectively, after 6h of exposure.

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.

Acanthamoeba T4 genotype associated with keratitis infections in Tunisia

Acanthamoeba keratitis (AK) is a sight-threatening infection. We report five cases of AK diagnosed from 2005 to 2009 in the Laboratory of Parasitology-Mycology at Habib Bourguiba Sfax Hospital, Tunisia. All were associated with improper care of contact lenses (rinsing of contact lenses with tap water and inappropriate cleaning) and lens storage. The patients displayed different clinical presentations: corneal inflammation, corneal ulceration, and corneal abscess. The diagnosis was made after direct examination, culture, and polymerase chain reaction amplification with specific primers. The genotype classification was based on the highly variable DF3 region in the 18S rRNA gene. This is the first study characterizing Acanthamoeba genotype in Tunisia and North Africa. All Acanthamoeba isolates were associated to the T4 genotype. Three different DF3 sequence types were related to AK infections T4/10, T4/15, and T4/16.

Occurrence and characterization of Acanthamoeba similar to genotypes T4, T5, and T2/T6 isolated from environmental sources in Brasília, Federal District, Brazil

Species of Acanthamoeba can cause keratitis and brain infections. The characterization of environmental isolates is necessary to analyze the risk of human infection. We aimed at identifying and genotyping Acanthamoeba isolates from soil, swimming pools, and water features in Brasília, Federal District, Brazil, as well as determining their physiological characteristics and pathogenic potential. Among the 18 isolates studied, eight were similar to genotype T5, five to T4, and one to T2/T6, classified by the sequence analysis of 18S rDNA. Genotypes of four isolates were not determined. Ten isolates (55%) grew at 37 °C and seven (39%) grew in media with 1.5M mannitol, which are the physiological parameters associated with pathogenic Acanthamoeba; also, four isolates from swimming pools presented high pathogenic potential. Our results indicate a widespread distribution of potentially pathogenic Acanthamoeba T4, T5, and T2/T6 in different environmental sources in Brasília, revealing the potential risk of human infection and the need of preventive measures.

Non-compliance with contact lens wear and care practices: a comparative analysis

PURPOSE

To compare the effects of existing patient awareness of lens-related complications and underlying risk factors on actual patient behavior during contact lens wear and care practices in two different clinical study populations.

METHODS

Established contact lens wearers (n = 281) completed an anonymous written questionnaire on presenting to their habitual eye care practitioner in the Dallas-Fort Worth metroplex. Data were analyzed and compared against a second study population, which comprised established contact lens wearers (n = 152) who were sequentially evaluated after their routine contact lens examination at the University of Texas Southwestern Medical Center at Dallas, TX (UTSW). All patients were questioned regarding his or her lens care practices and knowledge of complications and risk factors associated with contact lens wear.

RESULTS

Fifty-eight percent of patients in the general community could identify by name a complication associated with lens wear compared with 91% within the medical center. The most frequent complications reported were related to comfort and handling (72%, Dallas-Fort Worth) and infection (47%, UTSW). The majority of patients could correctly identify risk factors associated with lens-related complications; awareness for topping-off solutions, tap water exposure, and hygiene varied between groups. Overall, 85% of patients perceived themselves as compliant with their lens wear and care practices. Using a standard scoring model to determine actual compliance, 2% of patients demonstrated good compliance; however, only 0.4% of patients were fully compliant with contact lens wear and care practices.

CONCLUSIONS

The data reveal some study bias in complication and risk awareness between populations; however, despite this limitation, a significant proportion of patients exhibited actual non-compliant behavior despite acknowledged awareness of risk. Although most patients consider themselves to be complying with standard practitioner guidelines for lens wear and care practices, essentially all contact lens wearing patients exhibit behavioral non-compliance with resulting increased risk for significant complications.

Effect of combined chlorhexidine gluconate and neosporin on experimental keratitis with two pathogenic strains of Acanthamoeba

Acanthamoeba keratitis (AK) is a painful, sight-threatening, and difficult-to-treat corneal infection caused by the ubiquitous free-living amoebae Acanthamoeba species. The aim of the present study was to compare the severity of keratitis, caused by Acanthamoeba hatchetii and Acanthamoeba castellanii infections, and to assess the therapeutic effects of combined chlorhexidine (CHX) and Neosporin® treatment in rats. The rats were first divided into two groups, in which the eyes of the animals were infected with A. hatchetii or A. castellanii trophozoites. On day 5, all corneas were examined in order to determine the degree of infection (grade 0 to 3), and animals were divided into two new groups, treatment and infected control groups. The treatment was continued for 28 days, followed by excision and histological evaluation of the corneas. In conclusion, the clinical picture progressed more rapidly and severely in eyes infected by A. castellanii, while it was non-invasive and slower to progress with A. hatchetii. Moreover, eyes infected by A. hatchetii responded quicker and more positively to therapy, consistent with its clinical course, while a longer recovery was seen with A. castellanii. Histological examinations revealed the presence of A. castellanii and A. hatchetii trophozoites in the stroma of eyes of the treatment and control groups. As a result, our findings suggest that a combination of Neosporin with lower doses of CHX may be beneficial to treat patients with early diagnosis of AK.

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.

Potentially pathogenic free-living amoebae isolated from hospital wards with immunodeficient patients in Tehran, Iran

This study investigated the occurrence of free-living amoebae (FLA) in immunodeficiency wards of hospitals in Tehran, Iran. A total of 70 dust and biofilm samples from wards serving transplant, pediatric (malignancies), HIV, leukemia and oncology patients of five university hospitals were collected and examined for the presence of FLA using culturing and molecular approaches. Based on the morphology of the amoebae in plate cultures, primer sets were applied for molecular identification of Acanthamoeba, vahlkampfiid amoebae and Hartmannella. Out of 70 samples, 37 (52.9%) were positive for FLA. Acanthamoeba belonged to the T4 genotype was the most prevalent isolate. Presence of the T4 genotype on medical instruments, including an oxygen mask in an isolation room of an immunodeficiency pediatric ward, should be of concern for health authorities. Acanthamoeba T5 genotypes, Hartmannella vermiformis, and Vahlkampfia avara were also present. These results highlight a clear need for greater attention to improved disinfection, especially where susceptible patients, such as those who are immune-suppressed, are served. To our knowledge, this is the first report of these FLA in immunodeficiency wards in Iran, and also the first to identify Acanthamoeba T5, Hartmannella, and Vahlkampfia in moist habitats, such as biofilms, in this country.

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.

Susceptibility of Aedes aegypti (Diptera: Culicidae) to Acanthamoeba polyphaga (Sarcomastigophora: Acanthamoebidae)

To date there is no report on mosquitoes infected with free-living amoebae. For this reason, the aim of this study was to verify if Aedes aegypti could be susceptible to Acanthamoeba polyphaga under laboratory conditions, so trophozoites were offered as a unique food resource for larvae of first instar. The results show that those amoebae are able to infect and colonize the mosquito gut and could be re-isolated of all stages of the mosquito (larvae, pupae, and adults).

Soft contact lens disinfection solution efficacy: clinical Fusarium isolates vs. ATCC 36031

PURPOSE

To compare the disinfecting efficacy of five soft contact lens multipurpose disinfection solutions (MPDS) against Fusarium solani clinical isolates and the ISO standard ATCC 36031 strain.

METHODS

Three commercially available and two recalled MPDS were tested using the ISO/CD 14,729 stand-alone test for contact lens care products against 10 ocular isolates of F. solani and the ATCC 36031 strain. The effect of filtering the fungal suspension before incubating in MPDS was also tested. An average log reduction in colony forming units at the manufacturer's minimum recommended disinfection time was determined and compared with criteria for stand-alone disinfection products for each MPDS against each strain.

RESULTS

No difference between filtered and unfiltered fungal suspensions was observed for the ISO standard, whereas in one MPDS the representative clinical isolate showed significantly increased resistance when unfiltered. All but one solution met the stand-alone criteria of 1.0-log reduction of colony forming units against the recommended ISO standard strain ATCC 36031. However, there was wide variation in the ability of MPDS to meet the ISO disinfection criteria when tested against clinical isolates. Among the commercially available MPDS, the two polyquaternium-based solutions showed a higher disinfecting efficacy than the biguanide-based solution. The two recalled solutions showed a lower disinfecting efficacy than the polyquaternium-based solutions. Further, the clinical isolates were significantly more resistant to disinfection than was the recommended ISO strain.

CONCLUSIONS

The effect of filtering the fungal suspension to remove hyphae seems to be relevant in the clinical isolate tested, but not in the ISO strain. Clinical isolates were significantly more resistant to disinfection than the recommended ISO strain in the presence of both the commercially available and the recalled MPDS. The use of clinical isolates in stand-alone disinfection testing is indicated. Because there were significant differences in increased resistance exhibited by clinical isolates and in a mixed (unfiltered) culture the use of a single laboratory strain may be insufficient to provide assurance that the disinfection solution will be effective against clinical isolates.

Rapid identification of Acanthamoeba from contact lens case using loop-mediated isothermal amplification method

A method employing loop-mediated isothermal amplification (LAMP) of 18S ribosomal RNA gene was developed to detect Acanthamoeba in contact lens cases. A prevalence of 7% (10/150) was detected, with 100% sensitivity and 100% specificity when compared with the standard culture technique. Using visual inspection of turbidity a minimum of 10pg of Acanthamoeba DNA could be detected, 10 times more sensitive than quantitative PCR employing two of the LAMP primers. The production of LAMP amplicons was confirmed by gel-electrophoresis and ethidium bromide staining. The LAMP procedure takes less than 2h to perform and will be useful for incorporation into a point-of-care screening of suspected Acanthamoeba infection.