Strain variation in Bacillus cereus biofilms and their susceptibility to extracellular matrix-degrading enzymes

Bacillus cereus is a foodborne pathogen and can form biofilms on food contact surfaces, which causes food hygiene problems. While it is necessary to understand strain-dependent variation to effectively control these biofilms, strain-to-strain variation in the structure of B. cereus biofilms is poorly understood. In this study, B. cereus strains from tatsoi (BC4, BC10, and BC72) and the ATCC 10987 reference strain were incubated at 30°C to form biofilms in the presence of the extracellular matrix-degrading enzymes DNase I, proteinase K, dispase II, cellulase, amyloglucosidase, and α-amylase to assess the susceptibility to these enzymes. The four strains exhibited four different patterns in terms of biofilm susceptibility to the enzymes as well as morphology of surface-attached biofilms or suspended cell aggregates. DNase I inhibited the biofilm formation of strains ATCC 10987 and BC4 but not of strains BC10 and BC72. This result suggests that some strains may not have extracellular DNA, or their extracellular DNA may be protected in their biofilms. In addition, the strains exhibited different patterns of susceptibility to protein- and carbohydrate-degrading enzymes. While other strains were resistant, strains ATCC 10987 and BC4 were susceptible to cellulase, suggesting that cellulose or its similar polysaccharides may exist and play an essential role in their biofilm formation. Our compositional and imaging analyses of strains ATCC 10987 and BC4 suggested that the physicochemical properties of their biofilms are distinct, as calculated by the carbohydrate to protein ratio. Taken together, our study suggests that the extracellular matrix of B. cereus biofilms may be highly diverse and provides insight into the diverse mechanisms of biofilm formation among B. cereus strains.

Metagenomic Analysis of Microbial Composition Revealed Cross-Contamination Pathway of Bacteria at a Foodservice Facility

Bacterial contamination of food-contact surfaces can be a potential risk factor for food quality and safety. To evaluate the spatial and temporal variations of the potential cross-contamination routes, we conducted a biogeographical assessment of bacteria in a foodservice facility based on the diversity of microflora on each surface. To this end, we performed high-throughput amplicon sequencing of 13 food-contact and non-food contact surfaces in a foodservice facility throughout a year. The results showed that Bacillus, Acinetobacter, Streptophyta, Enterobacter, Pseudomonas, Serratia, Enhydrobacter, Staphylococcus, Paracoccus, and Lysinibacillus were the dominant genera found on the kitchen surfaces of the foodservice facility. Depending on the season, changes in Firmicute/Proteobacteria ratios were observed, and the fan becomes the main source of outdoor air contamination. The microbial flow associated with spoilage was also observed throughout food preparation. Taken together, our results would be a powerful reference to hygiene managers for improvement of food processes.

Selective Binding and Elution of Aptamers for Pesticides Based on Sol-Gel-Coated Nanoporous Anodized Aluminum Oxide Membrane

Sol-gel-based mesopores allow the entry of target small molecules retained in their cavity and aptamers to bind to target molecules. Herein, sol-gel-based materials are applied to screen-selective aptamers for small molecules, such as pesticides. To enhance the efficiency of aptamer screening using a sol-gel, it is necessary to increase the binding surface. In this study, we applied the sol-gel to an anodized aluminum oxide (AAO) membrane, and the morphological features were observed via electron microscopy after spin coating. The binding and elution processes were conducted and confirmed by fluorescence microscopy and polymerase chain reaction. The sol-gel coating on the AAO membrane formed a hollow nanocolumn structure. A diazinon-binding aptamer was bound to the diazinon-containing sol-gel-coated AAO membrane, and the bound aptamer was effectively retrieved from the sol-gel matrix by thermal elution. As a proof of concept, a sol-gel-coated AAO disc was mounted on the edge of a pipette tip, and the feasibility of the prepared platform for the systematic evolution of ligands by exponential enrichment (SELEX) of the aptamer binding was also confirmed. The proposed approach will be applied to an automated SELEX cycle using an automated dispenser, such as a pipetting robot, in the near future.

Enzymatic Inactivation of Pathogenic and Nonpathogenic Bacteria in Biofilms in Combination with Chlorine

This study investigated the effects of enzyme application on biofilms of bacterial isolates from a cafeteria kitchen and foodborne pathogens and the susceptibility of Salmonella biofilms to proteinase K combined with chlorine treatment. For four isolates from a cafeteria kitchen ( Acinetobacter, Enterobacter, and Kocuria) and six strains of foodborne pathogens ( Salmonella enterica, Staphylococcus aureus, and Vibrio parahaemolyticus), the inhibitory effect of enzymes on biofilm formation at 25°C for 24 h or the degradative efficacy of enzymes on 24-h mature biofilm at 37°C for 1 h in tryptic soy broth (TSB) was examined in a polystyrene microtiter plate. The effect of enzymes was also evaluated on a subset of these strains in 20 times diluted TSB (1/20 TSB) at 25°C. The working concentrations of five enzymes were 1 U/100 μL for α-amylase, amyloglucosidase, cellulase, and DNase and 1 milli-Anson unit/100 μL for proteinase K. In addition, 24-h mature Salmonella Typhimurium biofilm on a stainless steel coupon was treated with proteinase K for 1 h at 25°C followed by 20 ppm of chlorine for 1 min at 25°C. The results showed that certain enzymes inhibited biofilm formation by the kitchen-originated bacteria; however, the enzymatic effect was diminished on the mature biofilms. Biofilm formation of V. parahaemolyticus was suppressed by all tested enzymes, whereas the mature biofilm was degraded by α-amylase, DNase I, and proteinase K. Proteinase K was effective in controlling Salmonella biofilms, whereas a strain-dependent variation was observed in S. aureus biofilms. In 1/20 TSB, Enterobacter cancerogenus and Kocuria varians were more susceptible to certain enzymes during biofilm formation than those in TSB, whereas the enzymatic effect was much decreased on 24-h mature biofilms, regardless of nutrient conditions. Furthermore, synergistic inactivation of Salmonella Typhimurium in biofilms was observed in the combined treatment of proteinase K followed by chlorine. Live/Dead assays also revealed a decrease in density and loss of membrane integrity in Salmonella Typhimurium biofilms exposed to the combined treatment. Therefore, certain enzymes can control biofilms of isolates residing in a cafeteria kitchen and foodborne pathogens. This study demonstrates the potential of enzymes for the sanitation of food processing environments and of proteinase K combined with chlorine to control Salmonella biofilms on food contact surfaces.

Role of eptC in Biofilm Formation by Campylobacter jejuni NCTC11168 on Polystyrene and Glass Surfaces

The complex roles of cell surface modification in the biofilm formation of Campylobacter jejuni, a major cause of worldwide foodborne diarrheal disease, are poorly understood. In a screen of mutants from random transposon mutagenesis, an insertional mutation in the eptC gene (cj0256) resulted in a significant decrease in C. jejuni NCTC11168 biofilm formation (<20%) on major food contact surfaces, such as polystyrene and borosilicate glass, when compared with wild-type cells (p < 0.05). In C. jejuni strain 81-176, the protein encoded by eptC modified cell surface structures, such as lipid A, the inner core of lipooligosaccharide, and the flagellar rod protein (FlgG), by attaching phosphoethanolamine. To assess the role of eptC in C. jejuni NCTC11168, adherence and motility tests were performed. In adhesion assays with glass surfaces, the eptC mutant exhibited a 0.77 log CFU/cm² decrease in adherence compared with wild-type cells during the initial 2 h of the assay (p < 0.05). These results support the hypothesis that the modification of cell surface structures by eptC affects the initial adherence in biofilm formation of C. jejuni NCTC11168. In motility tests, the eptC mutant demonstrated reduced motility when compared with wild-type cells, but wild-type cells with the transposon inserted in a gene irrelevant to biofilm formation (cj1111c) also exhibited decreased motility to a similar extent as the eptC mutant. This suggests that although eptC affects motility, it does not significantly affect biofilm formation. This study demonstrates that eptC is essential for initial adherence, and plays a significant role in the biofilm formation of C. jejuni NCTC11168.

A review of pedestrian fatalities in Singapore from 1990 to 1994

The authors reviewed 369 consecutive pedestrian fatalities, which occurred from 1990 to 1994. This represented 28.5% (range 23.3 to 37.2; 95% CI 26% to 31%) of all road accident autopsies during that time. The mean and median ages of this population were 51 (95% CI 48.63 to 53.37) and 54 years, respectively. There were 160 (43.3%) who were in the economically productive ages of 20 to 59 years. Of the 369 victims, 224 (60.7%) were males and 145 (39.3%) females, there being a preponderance of males across all age groups. Most of these accidents occurred during the hours of daylight and in conditions of good weather and visibility. It was estimated that pedestrian behaviour contributed, in part, to at least three-quarters of these fatalities. The majority of these pedestrians died from multiple injuries (181; 49.1%) and closed head injury (146; 39.6%). The vast majority of subjects (357; 96.7%) had injury severity scores (ISS) > or = 16. A total of 100 subjects (27.1%) died at the sites of the accidents. Of these, 99 had ISS > or = 16, with 31 having had ISS = 75 (maximum score). Similarly, all 55 deaths that occurred in the A & E departments were associated with ISS > or = 16, with 6 having ISS = 75. This would imply that most of the deaths that had occurred on site and at A & E departments were not unexpected. Interestingly, no pedestrian aged < or = 12 years had an ISS < or = 16, suggesting that they may be more vulnerable to serious or life-threatening injury than adults. There were 46 (12%) victims who had detectable levels of ethanol in their blood samples, of whom, 10 had ISS = 75. However, the difference between the latter proportion and that of the rest of the pedestrian population who had no alcohol detected in their blood samples (31/323), was only marginally significant (95% CI 0.002 to 0.245). There was a high prevalence of pre-existing and intercurrent diseases, such as ischaemic heart disease (58.8%), hypertensive heart disease (30.4%), chronic obstructive airways disease (47.4%), bronchopneumonia (18.2%) and evidence of systemic hypertension (40.7%). It is submitted that the existence of these underlying conditions should be anticipated, or suspected, in the management of injured pedestrians, particularly the elderly, as they may influence the outcome of their critical care.

Early vitrectomy and endolaser photocoagulation in patients with type I diabetes with severe vitreous hemorrhage

PURPOSE

To determine if adjunctive endolaser photocoagulation has further improved the outcome of early vitrectomy for severe vitreous hemorrhage in young patients with type I insulin-dependent diabetes.

METHOD

The authors reviewed clinical records and fundus photographs of all primary diabetic vitrectomies performed at the Yale Eye Center between July 1986 and June 1993. Only young patients with type I diabetes who underwent vitrectomy within 6 months of vitreous hemorrhage were included.

RESULTS

Of 197 vitrectomies for diabetic retinopathy, 12 eyes of ten patients met the Diabetic Retinopathy Vitrectomy Study Group criteria. Patients ranged in age from 24 to 29 years (mean, 27.3 years) and had 11 to 21 years (mean, 17.2 years) of history of diabetes. Preoperative visual acuity was 5/200 in seven eyes, 2/200 in three eyes, hand motions in one eye, and light perception in one eye. The duration of vitreous hemorrhage was approximately 1 month in two eyes, 1 to 3 months in five eyes, and 3 to 6 months in five eyes. Neovascularization was documented in 12/12 eyes. Preoperatively, all patients had received panretinal photocoagulation with 1937 to 5328 burns (mean, 4126). Postoperative follow-up ranged from 12 to 38 months (mean, 24.6 months). Best-corrected postoperative visual acuity was 20/40 or better in 7 eyes (58.33%) and 20/70 or better in 11 eyes (91.66%). Neovascularization involuted in 11/12 eyes and remained so till the last follow-up.

CONCLUSION

Patients with type I diabetes with severe vitreous hemorrhage benefit from early endolaser photocoagulation combined with current vitrectomy techniques. The authors' findings are consistent with those of the Diabetic Retinopathy Vitrectomy Study Group, and patients can expect both improved visual acuity and anatomic success.

A quantitative and qualitative assessment of the Solitaire Bifocal Contact Lens

We performed qualitative and quantitative assessments of contact lens performance at 1 and 6 months among 23 patients enrolled in the Solitaire Bifocal Contact Lens Study. Overall satisfaction and comfort at 6 months was rated good to excellent in 83% and 84% of patients, respectively. Daytime acuity at distance and near were rated very good to excellent in 75% and 83% of subjects. Quantitative measurements of distance and near acuities at 1 month revealed 83% and 88% of subjects, respectively, seeing better than or equal to 20/25 or J1. At 6 months there was a moderate decrease in the measured distance acuity. A disparity in glare disability was noted, with 53% of subjects indicating significant glare problems but only 21% of glare tested patients having acuities worse than 20/40. Attrition from the study was highest in the first month and was more common among first-time contact lens users. Overall, this segmented bifocal contact lens is well-tolerated and provides good distance and near vision for presbyopic patients.

Clinical evaluation of the anterior constant focus (ACF) annular bifocal contact lens

We evaluated the distance and near vision of 33 presbyopic patients who wore the Anterior Constant Focus (ACF) rigid gas permeable (RGP) bifocal lens. Twenty-seven patients (82%) wore the lenses for one year; the six patients who quit the study complained of unacceptable vision (four patients) and discomfort (two patients). Twenty-five patients (76%) obtained 20/25 or better distance vision, and 28 patients (85%) obtained J2 or better near vision. Contrast sensitivity was within normal limits in 24 of 33 (73%) patients. We feel the ACF lens provides good bifocal vision in a non-translating RGP design.

Current status of malaria in Malaysia

The Malaria Eradication Program was started in 1967 in Peninsular Malaysia. Since then and up to 1980, there was a reduction in the number of reported malaria cases from 160,385 in 1966 to 9,110 cases for Peninsular Malaysia. Although the concept of eradication has changed to one of control in the 1980, the anti-malaria activities have remained the same. However, additional supplementary activities such as the use of impregnated bednets, and the Primary Health Care approach, have been introduced in malarious and malaria-prone areas. Focal spraying activity is instituted in localities with outbreaks in both malaria-prone and non-malarious areas. Passive case detection has been maintained in all operational areas. In 1990, 50,500 cases of malaria were reported of which 69.7% (35,190) were from Sabah, 27.8% (14,066) from Peninsular Malaysia and 2.5% (1,244) from Sarawak. Until June 1991 a total of 18,306 cases were reported for the country. Plasmodium falciparum continues to be the predominant species, contributing to 69.6% of the parasites involved. The case fatality rate for 1990 was 0.09%. There were 43 deaths all of which were attributed to cerebral malaria. The problems faced in the prevention and control of malaria include problems associated with the opening of land for agriculture, mobility of the aborigines of Peninsular Malaysia (Orang Asli) and inaccessibility of malaria problem areas. There is need to ensure prompt investigation and complete treatment of cases especially in malarious areas. The promotion of community participation in control activities should be intensified. Primary Health Care should be continued and intensified in the malarious areas.(ABSTRACT TRUNCATED AT 250 WORDS)

Removal of viscoelastic materials after experimental cataract surgery in vitro

The one significant complication of viscoelastic materials is that they may cause postoperative intraocular pressure rise. We investigated the rate and ease of removal of various viscoelastics using the Miyake video technique. Five viscoelastics were investigated: sodium hyaluronate (Healon), Healon GV, chondroitin sulfatesodium hyaluronate (Viscoat), hydroxypropylmethylcellulose (Occucoat), and polyacrylamide (Orcolon). The viscoelastics were dyed with fluorescein and, after filling the capsular bag with a viscoelastic material, a posterior chamber intraocular lens (IOL) was implanted. The viscoelastic was then aspirated using an automated irrigation/aspiration device. Healon and Healon GV were completely removed within 20 to 25 seconds. Viscoat adhered to the lens capsule and to the posterior surface of the IOL and cooplete removal required approximately 3.5 minutes. Most Occucoat and Orcolon was aspirated within one minute; however, removal was completed only after three minutes. Removal of Healon and Healon GV was faster and more complete than removal of the other viscoelastics. Whether a small amount of viscoelastic left in the eye or trapped behind the IOL optic has any clinical significance has to be studied.

The elastic properties of the lens capsule in capsulorhexis

We investigated the ability of the anterior lens capsule to stretch and allow removal of lens substance and intraocular lens implantation through a continuous circular capsulorhexis. Capsulorhexis of various sizes (2.5 to 7.5 mm) were performed in 50 eyes obtained post mortem from 31 patients. The nucleus and cortex were removed by either phacoemulsification (35 eyes) or manual extracapsular cataract extraction (15 eyes). The opening of the capsule was then gradually enlarged, using a modified caliper with two pins attached to its tips, until the margins were torn. The capsule was torn when the circumference at the time of rupture was 1.6 times larger than the circumference of the original circular capsulectomy or 5.0 times larger than the diameter of the capsulectomy. Manual extraction of a lens nucleus with profile circumference (sagittal or anteroposterior) of 18.0 to 22.0 mm can be performed through a 5.5-mm opening and a 6.0- to 7.0-mm optic intraocular lens (profile circumference of 13.0 to 17.0 mm) can be implanted through a 4.5-mm capsulectomy.

An analysis of flexible anterior chamber lenses with special reference to the normalized rate of lens explantation

A survey of 1204 closed-loop anterior chamber intraocular lenses (AC-IOLs) and 310 open-loop AC-IOLs accessioned between November 1982 and January 1990 was conducted at the Center for Intraocular Lens Research. An analysis of complication rates was done after normalization of data with respect to market share totals. The results establish that an unacceptable complication rate is associated with the closed-loop design when compared with either the tripod or quadripod lens styles. Furthermore, the closed-loop designs, while comprising an estimated 45% of the total number of AC-IOLs estimated to be implanted in the United States (n = 674,000), were responsible for 80% of the AC-IOLs explanted after complications and accessioned at the authors' center. A rethinking of the extreme condemnation of all anterior chamber IOLs that has surfaced in recent years is warranted. This is particularly true with respect to indications for use of sutured posterior chamber (PC) IOLs as well as with regard to possible use of open-loop AC-IOLs in less-industrialized nations.

Preparation and study of human eyes obtained postmortem with the Miyake posterior photographic technique

A modification of the original Miyake technique of posterior photography of human eyes obtained postmortem is presented. A detailed description of globe preparation and equipment is described. Use of modern technology including a high magnification microscope system and video camera permits dynamic or realtime observations of tissue effects of various surgical procedures such as the cataract operation. This technique provides both a research and educational tool that can be used by ophthalmologists to improve the quality of surgery. Most important, it is an instructional tool that should reduce the "learning curve" that is inherent when modifying one's surgical technique.