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.

Effect of multipurpose solutions against Acinetobacter carrying QAC genes.

PURPOSE: Acinetobacter has low virulence but causes infections in subjects with reduced immunity. It has been reported in ocular infections including those of patients using contact lenses. Treatment is difficult because Acinetobacter is frequently multidrug resistant. Antibiotic-resistant strains frequently also harbor genes for antiseptic resistance (quaternary ammonium compound [QAC]) genes. Because Acinetobacter is part of the normal flora, it may contaminate contact lens and accessories. This study aims to investigate carriage rates of QAC genes in household and clinical isolates of Acinetobacter and to determine the effectiveness of two multipurpose solutions (MPSs) for soft lenses against organisms carrying QAC genes. METHODS: DNA was extracted from 11 bathroom isolates and 15 clinical isolates and amplified by polymerase chain reaction to determine the presence of qacEΔ1. Gene-positive and gene-negative control strains were used to challenge the two MPSs, and minimum inhibitory concentrations (MICs) of these organisms to benzalkonium chloride and chlorhexidine gluconate were determined. RESULTS: More than 90% of isolates carried qacEΔ1. The MICs of clinical isolates were higher than those of isolates of bathrooms. Both MPSs were able to produce a 3-log reduction in the numbers of all isolates. CONCLUSIONS: Although most isolates carried qacEΔ1 and elevated MICs to benzalkonium chloride and chlorhexidine gluconate were observed, all were susceptible to both MPSs tested. However, if there were to be poor compliance with care procedures, it is probable that such organisms could survive in the presence of diluted or expired solutions.

High levels of Staphylococcus aureus contamination in Chinese-style roast pork.

Chinese roasted pork has been implicated as a major source of food poisoning caused by Staphylococcus aureus. Establishing the source, either as contaminants from raw meat or from food handlers, could facilitate drafting more appropriate guidelines for better prevention of food poisoning. To determine the rate and source of staphylococcal contamination, roasted pork purchased from 50 sui-mei shops in Hong Kong was sampled for presence of S. aureus by enrichment and subsequent culture. Isolates were characterized for methicillin sensitivity, spa type, and presence of Panton-Valentine leukocidin (PVL) and staphylococcal enterotoxins (SEs). Methicillin-resistant isolates were confirmed by presence of mecA and SCCmec type and sensitivity to vancomycin investigated. S. aureus was isolated from 25 (50%) samples, with 3 yielding two colony types. Of the 28 isolates, 3 were resistant to cefoxitin, but only 2 were mecA positive and belonged to SCCmec type V. The mecA negative isolate also lacked mecC, but had a penicillin minimum inhibitory concentration of 10 mg/L. A livestock-associated spa type (t034) was only observed in one methicillin-sensitive strain, all other isolates appearing to be of human origin, with 30% belonging to t189. One isolate was PVL positive and five carried genes for classical SEs. The high rate of staphylococcal contamination observed was probably associated with food handlers, as the strains belonged to spa types previously reported in clinical and nasal carriage isolates. The presence of enterotoxins in 18% of isolates confirms the risk of food poisoning associated with this product and emphasizes the need for improved guidelines for handling after preparation. Use of refrigerated display areas should be considered.

Isolation of methicillin-resistant Staphylococcus aureus (MRSA) from retail meats in Hong Kong.

OBJECTIVES: The presence of methicillin-resistant Staphylococcus aureus (MRSA) on meat purchased from retail outlets may allow its spread to households and represents a risk for colonization and possibly infection of consumers. Improved isolation methods have indicated that more than 10% of samples are positive. We aimed to determine rates of MRSA contamination of meat samples, including comparison of fresh and frozen samples. We characterized isolates and determined their antibiotic susceptibility. METHODS: Samples of raw meats commonly consumed in Hong Kong were investigated for MRSA contamination using a double-enrichment isolation method. Isolates were characterized by antibiotic susceptibility testing, presence of mecA, SCCmec type, staphylococcal enterotoxins, Panton-Valentin leukocidin (PVL), and spa type. Differences in rates of MRSA contamination between meat types, rearing method, locations, sources, and fresh or frozen storage were compared. RESULTS: MRSA was recovered from 21.9% of pork samples (78/355), 6.8% chicken (31/455), and 4.4% of beef (17/380). Isolation was considerably higher from fresh pork (47%) than frozen (0.6%), whereas contamination rates in fresh (6%) and frozen (7%) chicken were similar. All strains were multidrug resistant. All contaminated fresh pork and most frozen chicken originated from China. Most isolates belonged to CC9, being SCCmec IVb and spa type t899 or closely related spa types, but one chicken sample yielded ST398. Five strains carried spa types associated with human isolates. The egc enterotoxin group was present in the majority of isolates, but PVL in only three from chicken. CONCLUSIONS: The predominance of t899 in isolates indicates that the primary source of contamination may be pig carcasses, previously demonstrated to frequently harbor CC9-positive MRSA in Hong Kong and China. The high rates of meat contamination suggest that improvements in food safety and personal hygiene guidelines may be advisable to reduce risk of spread of these MRSA strains in the community.

Comparison of contamination rates of designs of rigid contact lens cases.

PURPOSE: To compare the rates of bacterial contamination in cylindrical and flat contact lens cases of orthokeratology (ortho-k) users and to investigate their preference of lens case design based on ease of use and handling. METHODS: Twenty-four children receiving ortho-k treatment were recruited. Each subject was given one cylindrical and one flat lens case, of which one side (50% right, 50% left) was sealed to prevent usage. Subjects were instructed to either rinse the case with water and air dry or rinse with multipurpose solution (MPS) and refill with MPS for storage after lens removal. After 1 month, cases were collected for culture, which was performed on the screw top, inner surface of cases, and also the holder for cylindrical cases. Each subject/parent completed a questionnaire about preference of case design. RESULTS: No significant differences in rates of surfaces contaminated were found between cleaning methods. Overall, 30% of both inner surfaces and screw tops of the cases yielded potentially pathogenic organisms, with significantly higher numbers present on both the inner surfaces (p = 0.003) and the screw tops of the flat cases (p = 0.001). Contamination of the inner surfaces with only normal flora occurred exclusively in the flat cases, but the screw tops of both case types frequently yielded only normal flora. Cylindrical case holder contamination was similar to the inner surface. There was a strong preference (75%) for the cylindrical cases, with subjects/parents citing ease of use and cleaning, good appearance and transparency, and reduced amount of MPS used. CONCLUSIONS: Although correct lens case care remains the most important factor in reducing contamination of the case, use of the cylindrical case design, preferred by the majority of subjects/parents, significantly reduced contamination in ortho-k subjects. The method used for cleaning the lens case had no effect on the rates of contamination in this study.

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.

Spiral gradient endpoint susceptibility testing: a fresh look at a neglected technique.

OBJECTIVES: Increasing antibiotic resistance and interest in matching antibiotic therapy with pharmacokinetic/pharmacodynamic characteristics of isolates has led to increasing demands for determination of MICs. This can lead to increased costs for the laboratory. The spiral gradient endpoint (SGE) technique, a low-cost method of MIC determination, was developed some years ago. Although the technique showed good correlation with reference methods, it was not widely employed, mainly due to the introduction of alternative methods. We have revisited this technique and evaluated it for the determination of MICs for fastidious organisms. METHODS: The SGE method was first optimized for fastidious organisms using Haemophilus influenzae. Intra-batch and inter-batch reproducibility was determined for H. influenzae, Streptococcus pneumoniae, Moraxella catarrhalis and Neisseria gonorrhoeae. The method was then evaluated by comparison of MICs for clinical isolates of these organisms determined by SGE with those determined with the reference method. RESULTS: Optimization of the technique resulted in a method with excellent reproducibility for all organisms tested [SD 0.10-0.337; coefficient of variation (CV) 8.59%-18.66%]. These SDs/CVs were lower than those of the reference methods (0.27-2.34; 31.0%-63.8%). There was excellent correlation of the MICs with the reference methods (0.908-0.930) and insignificant differences in numbers of strains in each resistance category, with no tendency for SGE to produce higher or lower MICs than the reference method (P > 0.05). CONCLUSIONS: SGE was shown to be reproducible and produced results that correlated well with standard techniques for fastidious organisms. The method offers a rapid, flexible, cost-effective alternative for smaller laboratories and for routine use in developing countries.

Rapid detection of vancomycin-non-susceptible Staphylococcus aureus using the spiral gradient endpoint technique.

OBJECTIVES: Several methods have been introduced for detection of vancomycin-non-susceptible Staphylococcus aureus [heterogeneous vancomycin-intermediate S. aureus (hVISA) and vancomycin-intermediate S. aureus (VISA)]. However, the limitations of these methods can delay appropriate therapy for the patient. This study evaluated the spiral gradient endpoint (SGE) technique for detection of hVISA/VISA. METHODS: The SGE method was evaluated for intra-batch, inter-batch and inter-observer reproducibility in comparison with MICs determined by agar dilution. Three media, Mueller-Hinton agar, brain heart infusion agar and brain heart infusion agar with 5% glucose, were evaluated. The SGE method was compared with agar dilution for correlation of MIC and susceptibility category using control strains, clinical isolates and induced vancomycin-non-susceptible strains. RESULTS: The SGE method had good reproducibility and there was excellent correlation of MICs generated by SGE using brain heart infusion agar with those by agar dilution (r(2) =0.950), with no difference in resistance categories generated by the two methods. All VISA isolates were correctly identified and the method allowed easy identification of hVISA by means of the trailing endpoint. CONCLUSIONS: SGE offers a simple, rapid and cost-effective alternative method for the detection of hVISA/VISA for the routine laboratory. Early recognition of vancomycin-non-susceptible strains can allow the change to appropriate antibiotics, resulting in potentially better patient outcomes.

Categorisation of myopia progression by change in refractive error and axial elongation and their impact on benefit of myopia control using orthokeratology.

AIMS: To compare the value of pre-treatment axial elongation (AE) and changes in refractive sphere (M change) for predicting the success in orthokeratology (ortho-k), in order to better identify suitable candidates for myopia control. METHODS: This study further analysed the data of 66 subjects receiving 7-month ortho-k treatment, following a 7-month observation period, during which single-vision spectacles were worn. Rate of myopia progression was determined by AE and M change and subjects categorised as slow, moderate, or rapid progressors based on these changes. Outcomes of myopia control, based on the AE reduction after ortho-k, were classified as 'ineffectual', 'clinically insignificant', or 'beneficial'. RESULTS: Of the 20 subjects, initially categorised as slow by AE and, of whom 95% were similarly categorised by M change, none benefitted from ortho-k. In contrast, of the 22 subjects with moderate AE, 77% and 23% displaying slow and moderate M change, respectively, the majority (73%) benefitted from ortho-k lens wear. The 24 subjects with rapid AE were poorly identified by M change, with only 21% correctly categorised. The vast majority of rapid progressors showed significant benefit after ortho-k. CONCLUSION: Progression of AE is a good indicator of subsequent success of ortho-k treatment. Delaying commencement of therapy is prudent for children with slow progression as results indicate that they would be unlikely to benefit from this intervention. As change in refractive error frequently underestimates rapid progression of AE, its value for identifying appropriate candidates for myopia control is poor.

Regional differences in temporal incidence of Clostridium difficile infection: a systematic review and meta-analysis.

BACKGROUND: Previous decades have witnessed a change in the epidemiology of Clostridium difficile infections. This study aimed to determine temporal trends in the incidence of C difficile infection across geographic regions. METHODS: An initial search of the relevant literature was conducted from date inception to October 2018 without language restriction. We estimated the pooled incidences using logit transformation, weighted by inverse variance. The Joinpoint Regression Analysis Program was used to explore its temporal trend. RESULTS: Globally, the estimated incidence of C difficile infection increased from 6.60 per 10,000 patient-days in 1997 to 13.8 per 10,000 patient-days in 2004. Thereafter, a significant downward trend was observed, at -8.75% annually until 2015. From 2005 to 2015, the incidences in most European countries decreased at a rate between 1.97% and 4.11% per annum, except in France, where an increasing incidence was observed (ß = 0.16; P < .001). The incidences have stabilized in North America over the same period; however, in Asia, the incidence increased significantly from 2006 to 2014 (annualized percentage change = 14.4%; P < .001). The increase was greatest in Western Asian countries, including Turkey and Israel (ß > 0.10; P < .004). CONCLUSIONS: This study revealed rapid changes in the incidence of C difficile infection. This meta-analysis should inform the allocation of resources for controlling C difficile infection and future surveillance efforts in countries where epidemiologic information on C difficile infection remains sparse.

Do multipurpose solutions damage porcine corneal epithelial cells?

PURPOSE: To determine and compare the cytotoxic effects on porcine corneal epithelial cells of commercially available multipurpose solutions (MPS) using fluorescein staining and flow cytometry (FCM). METHODS: Effects of exposure time of 10 s to 10 min of MPS containing polyquaternium-1 (MPS-A), polyaminopropyl biguanide (MPS-B), and polyhexanide (MPS-C), on porcine corneal epithelial cells were determined. Cell viability and membrane integrity were assessed by Annexin V-FITC/7-AAD staining and FCM. In further trials, whole corneas were immersed in MPS and control (buffered saline), and corneal fluorescein staining assessed before FCM analysis. RESULTS: Significantly higher percentages of 7-AAD-stained cells (early necrosis) were observed at all exposure times for MPS-A than for other solutions and control (p < 0.05). Exposure time in MPS-A and 7-AAD-stained cell proportions showed significant correlation (r = 0.9957; p < 0.0001). Significantly more cells dual-stained with Annexin V-FITC/7-AAD (late necrosis) after 5 min MPS-A exposure (11.8 +/- 1.1%), compared with 1.2 +/- 0.9% (MPS-B), 0.9 +/- 0.5% (MPS-C), and 1.8 +/- 0.2% (control). However, only 10 min exposure resulted in significant increases in fluorescein grades (p < 0.001), with median grade 0.75 for MPS-A, and 0.50 for the other MPS. CONCLUSIONS: MPS exposure, especially MPS-A, affected the viability and integrity of porcine corneal epithelial cells. Furthermore, our results confirmed that fluorescein staining correlates poorly with cytotoxicity. As fluorescein staining lacks sensitivity to determine cytotoxic effects of ophthalmic solutions, more objective and sensitive assessment methods such as differential staining and FCM should be developed.

Pre-treatment observation of axial elongation for evidence-based selection of children in Hong Kong for myopia control.

PURPOSE: This study aimed to develop evidence-based guidelines for identifying suitable subjects for myopia control using orthokeratology (ortho-k). METHODS: Changes in axial elongation (AE) in the worse eyes of 66 myopic children (myopia between -0.75 and -4.50 D and astigmatism <2.00D, and aged 6 to <16 years old) who wore single-vision spectacles for seven months before switching to orthokeratology treatment for another seven months were observed. RESULTS: AE during ortho-k lens wear was affected by age and rate of progression during spectacle wear. The percentage of subjects with rapid, moderate, and slow AE (equivalent annual myopia progression; rapid: ≥1.00D; moderate: 0.50D to <1.00D; slow: <0.50D) during spectacle wear was 36.3%, 33.3% and 30.3%, respectively. Rapid progression was most common in subjects aged less than nine, but 25% of subjects aged 9 to <13 and 12.5% aged 13 to <16 also demonstrated rapid progression. All subjects with rapid AE during spectacle wear achieved a significant reduction in eye elongation with ortho-k lens wear. Guidelines for patient selection was proposed based on the initial age and history of myopia progression. CONCLUSIONS: Myopia control is indicated for children at risk of developing high myopia. The suggested guidelines can help practitioners to identify children for whom the benefits outweigh the risks of serious adverse events.

Microbiological evaluation of different hand drying methods for removing bacteria from washed hands.

Proper drying of hands after washing is an integral part of hand hygiene. An experimental study on 30 subjects using multiple comparisons of six hand drying methods including 1) drying on own clothes, 2) drying with one paper towel, 3) drying with two paper towels, 4) drying with a warm air dryer while holding hands stationary for 20 s, 5) drying with a warm air dryer while hand rubbing for 20 s, and 6) drying with a jet air dryer until complete dryness was achieved. It aimed to determine the effectiveness of different hand drying methods for removing bacteria from washed hands, so as to identify the optimum method using minimum resources. Our study demonstrated that the use of jet air dryers is the best method to eliminate bacteria on hands, whereas drying hands on one's own clothes is the least effective. Drying hands in a stationary position could remove more bacteria than rubbing hands when using a warm air dryer for 20 s, which mimics people's usual hand-drying practice. No significant difference in bacteria reduction was detected between the use of one or two paper towels for hand drying; therefore, using fewer resources is recommended to maintain environmental sustainability.

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.

Reliability of N95 respirators for respiratory protection before, during, and after nursing procedures.

BACKGROUND: The adequate fit of an N95 respirator is important for health care workers to reduce the transmission of airborne infectious diseases in the clinical setting. This study aimed to evaluate whether adequately sealed N95 respirators may provide consistent protection for the wearer while performing nursing procedures. METHODS: Participants were a group of nursing students (N = 120). The best fitting respirator for these participants was identified from the 3 common models, 1860, 1860S, and 1870+ (3M), using the quantitative fit test (QNFT) method. Participants performed nursing procedures for 10-minute periods while wearing a backpack containing the portable aerosol spectrometers throughout the assessment to detect air particles inside the respirator. RESULTS: The average fit factor of the best fitting respirator worn by the participants dropped significantly after nursing procedures (184.85 vs 134.71) as detected by the QNFT. In addition, significant differences in particle concentration of different sizes (>0.3, >0.4, >1.0, and >4.0 µm) inside the respirator were detected by the portable aerosol spectrometers before, during, and after nursing procedures. CONCLUSIONS: Body movements during nursing procedures may increase the risk of face seal leakage. Further research, including the development of prototype devices for better respirator fit, is necessary to improve respiratory protection of users.

Awareness of tick-borne disease and compliance with using tick preventive products of dog owners in Hong Kong.

Tick-borne disease in dogs is common in South-east Asia and includes babesiosis and ehrlichiosis. These diseases can be largely prevented by compliant use of tick preventive products. This study investigated knowledge of ticks and tick-borne disease and use of tick preventive agents by a large sample of dog owners in Hong Kong. A total of 492 valid questionnaires were completed by owners attending veterinary practices, approached by researchers at common dog-walking areas, or targeted via local social media sites for pet owners. A high proportion of respondents were aware of tick-borne disease (79%) and this correlated well with use of preventive products. However, 18% of owners did not use any protection, mainly due to lack of knowledge of the risk of disease. Targeted advice stressing the importance of tick protection use and frequent follow-up at veterinary clinics could help reduce the risk of tick-borne disease. It would be beneficial if veterinarians provided training of frontline staff at the clinics to ensure they provide essential information to clients in an easily understandable format.

Does the presence of QAC genes in staphylococci affect the efficacy of disinfecting solutions used by orthokeratology lens wearers?

BACKGROUND/AIM: There has been increasing evidence of the emergence of antiseptic resistance mediated by quaternary ammonium compound (QAC) resistance genes, which may reduce the efficacy of disinfection. Although the presence of QAC-positive staphylococci has been shown to be elevated in contact lens wearers, the efficacy of multipurpose solutions (MPS) against such isolates has not been determined. This study investigated the efficacy of four MPS for rigid gas permeable (RGP) lenses against staphylococci-harbouring QAC genes. METHODS: Ability to reduce viability by three or more log reductions of four MPS for RGP lenses was tested against 60 disinfectant-resistant gene-positive staphylococci, comprising 38 coagulase-negative staphylococci (CNS) (17 ITALIC! qacA/B, 7 ITALIC! smr, 5 ITALIC! qacH, 9 habouring two or more genes) and 22 ITALIC! Staphylococcus aureus (16 ITALIC! qacA/B, 4 ITALIC! smr, 2 ITALIC! qacA/B+ ITALIC! smr)). 60 gene-negative isolates of staphylococci (30 CNS and 30 ITALIC! S aureus) were used as controls. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of these four MPS were determined. RESULTS: Although there was some variation between solutions, all failed to achieve a 3-log reduction in some ITALIC! S aureus and CNS isolates. Strains harbouring disinfectant-resistant genes were significantly less likely to be reduced by 3 logs by three of the solutions. Overall, the MIC and MBC of the four MPS against gene-positive clinical isolates were significantly higher than those of gene-negative isolates. CONCLUSION: The efficacy of MPS solutions for RGP lenses against staphylococci varied. The presence of disinfectant-resistance genes significantly adversely affected disinfecting capacity of RGP solutions.

Effects of Lead Phytochemicals of Radix Scutellariae on Acanthamoeba.

Purpose: Acanthamoeba keratitis (AK), which is associated with noncompliant use of contact lenses, remains difficult to treat due to delayed diagnosis and paucity of therapeutic agents. Although improvements in activity against Acanthamoeba infection have been achieved in disinfecting solutions for soft contact lenses, such modifications have not been extended to those for special rigid gas permeable (RGP) contact lenses, which are increasingly used for myopia control in children. Phytochemicals present in herbs used for traditional Chinese medicine may be effective as therapeutic or preventive agents. The purpose of this study was to investigate amoebicidal properties of lead phytochemicals of Radix scutellariae alone and in combination with multipurpose (disinfecting) solutions (MPS) for RGP lenses. Methods: Viability of Acanthamoeba castellani and A. polyphaga trophozoites was determined following exposure to four phytochemicals: baicalin, baicalein, wogonoside, and oroxylin A and both alone and in combination with four RGP MPS, using a modified stand-alone technique. Results: As individual agents, wogonoside and oroxylin A showed highest activity against A. castellani and A. polyphaga trophozoites, respectively. For both organisms, the combination of baicalein and oroxylin A was superior. Effectiveness of MPS alone did not exceed 0.27 log reduction, but addition of combined baicalein and oroxylin A resulted in 0.92 and 0.64 log reductions of A. castellani and A. polyphaga, respectively. Conclusions: The combination of baicalein and oroxylin A enhanced the activity of MPS for RGP contact lenses against trophozoites of two pathogens, A. castellani, and A. polyphaga, and offers a potential therapeutic and/or preventative agent for AK.

Tracking sources of Staphylococcus aureus hand contamination in food handlers by spa typing.

We aimed to identify the source of Staphylococcus aureus contaminating hands of food handlers. Nasal samples and direct fingertip imprints were collected on 2 occasions from food handlers and characterized to determine likely sources of hand contamination. Most hand contamination was attributable to nasal isolates of persistently colonized coworkers who had presumably contaminated the environment. Regular handwashing should be supplemented by effective environmental disinfection.

Detection of methicillin-resistant Staphylococcus aureus using a gold nanoparticle-based colourimetric polymerase chain reaction assay.

We report the use of gold nanoparticles (Au NPs) for direct colourimetric polymerase chain reaction (PCR) detection of methicillin-resistant Staphylococcus aureus (MRSA) in clinical specimens. The colourimetric assay comprised of 2 Au NP probes functionalized with Staphylococcus aureus 23S rRNA- and mecA-specific oligonucleotides. In this study, 72 clinical samples were tested, which included positive blood culture (n=23), urine (n=8), respiratory samples (n=23), as well as wound swabs, pus and body fluid (n=18). Results were recorded qualitatively by direct visual examination and quantitatively by UV-vis spectrophotometry. Using conventional bacterial culture as the gold standard, the sensitivity, specificity, positive predictive value and negative predictive value of this colourimetric assay were 97.14%, 91.89%, 91.89% and 97.14%, respectively, which were comparable to that of commercial real-time PCR assays with a lower cost per reaction. Our assay also showed good agreement with bacterial culture (κ=0.889). The overall detection limit was 500 ng target amplicon, which was comparable to or better than other similar Au NP biosensors. Interestingly, our data revealed the possible relationship between Au NP probe-target hybridization site and assay performance, which might provide hints for design of the Au NP biosensors for nucleic acid detection. To conclude, our study was the first report on the use of Au NP colourimetric assay for direct detection of MRSA in various types of clinical specimens. Further evaluation of the assay is needed in large-scale trials which can also allow for some modifications to streamline the procedures for routine use.