In multipolar vertebrate neurons, action potentials (APs) initiate close to the soma, at the axonal initial segment. Invertebrate neurons are typically unipolar with dendrites integrating directly into the axon. Where APs are initiated in the axons of invertebrate neurons is unclear. Voltage-gated sodium (NaV) channels are a functional hallmark of the axonal initial segment in vertebrates. We used an intronic Minos-Mediated Integration Cassette to determine the endogenous gene expression and subcellular localization of the sole NaV channel in both male and female Drosophila, para. Despite being the only NaV channel in the fly, we show that only 23 ± 1% of neurons in the embryonic and larval CNS express para, while in the adult CNS para is broadly expressed. We generated a single-cell transcriptomic atlas of the whole third instar larval brain to identify para expressing neurons and show that it positively correlates with markers of differentiated, actively firing neurons. Therefore, only 23 ± 1% of larval neurons may be capable of firing NaV-dependent APs. We then show that Para is enriched in an axonal segment, distal to the site of dendritic integration into the axon, which we named the distal axonal segment (DAS). The DAS is present in multiple neuron classes in both the third instar larval and adult CNS. Whole cell patch clamp electrophysiological recordings of adult CNS fly neurons are consistent with the interpretation that Nav-dependent APs originate in the DAS. Identification of the distal NaV localization in fly neurons will enable more accurate interpretation of electrophysiological recordings in invertebrates. SIGNIFICANCE STATEMENT The site of action potential (AP) initiation in invertebrates is unknown. We tagged the sole voltage-gated sodium (NaV) channel in the fly, para, and identified that Para is enriched at a distal axonal segment. The distal axonal segment is located distal to where dendrites impinge on axons and is the likely site of AP initiation. Understanding where APs are initiated improves our ability to model neuronal activity and our interpretation of electrophysiological data. Additionally, para is only expressed in 23 ± 1% of third instar larval neurons but is broadly expressed in adults. Single-cell RNA sequencing of the third instar larval brain shows that para expression correlates with the expression of active, differentiated neuronal markers. Therefore, only 23 ± 1% of third instar larval neurons may be able to actively fire NaV-dependent APs.

AIMS To determine the quantitative relation between the major risk factors for microbial keratitis of previous ocular surface disease and contact lens wear and central and peripheral infiltration, often associated with ulceration, in order to establish a rational chemotherapeutic management algorithm. METHODS Data from 55 patients were collected over a 10 month period. All cases of presumed microbial keratitis where corneal scrapes had been subjected to microbiological examination were included. Risk factor data and laboratory outcome were recorded. Antimicrobial regimens used to treat each patient were documented. RESULTS 57 episodes of presumed microbial keratitis were identified from 55 patients, 24 male and 31 female. There were 30 central infiltrates and 27 peripheral infiltrates of which 28 were culture positive (73% of central infiltrates, 22% of peripheral infiltrates). 26 patients had worn contact lenses of whom 12 had culture positive scrapes (9/14 for central infiltrates, 3/12 for peripheral infiltrates). 31 patients had an ocular surface disease of whom five previous herpes simplex virus keratitis patients developed secondary bacterial infection. Anterior chamber activity and an infiltrate size ⩾ 4 mm2 were more common with culture positive central infiltrates than peripheral infiltrates (χ2 test = 11.98, p<0.001). CONCLUSIONS Predisposing factors for “presumed” microbial keratitis, either central or peripheral, were: ocular surface disease (26/57 = 45.6%), contact lens wear (26/57 = 45.6%), and previous trauma (5/57 = 8.8%). Larger ulceration (⩾4 mm2) with inflammation was more often associated with positive culture results for central infiltration. None of these four variables (contact lens wear, ocular surface disease, ulcer size, anterior chamber activity) were of intrinsic value in predicting if a peripheral infiltrate would yield identifiable micro-organisms. Successful management of presumed microbial keratitis is aided by a logical approach to therapy, with the use of a defined algorithm of first and second line broad spectrum antimicrobials, for application at each stage of the investigative and treatment process considering central and peripheral infiltration separately.

PURPOSE:Acanthamoeba was isolated from the cornea of a soft contact lens wearer who had keratitis. The protozoan was also isolated from the contact lens storage case and the domestic water supply used to clean the case. Using morphologic features, all three isolates were identified tentatively as A. griffini, a species not previously associated with keratitis. Complete small subunit ribosomal RNA gene (18S rDNA) sequence analysis was used to characterize further the three isolates.METHODS:18S rDNA was polymerase chain reaction-amplified from whole cell DNA derived from amoebal lysates. The genes were cloned and sequenced. Complete sequences of approximately 2800 base pairs were obtained from each culture and compared wih those stored in a data base for homologous Acantamoeba sequences.RESULTS:The isolates were unequivocally identified as A. griffini both by comparison of the gene sequence available for the type strain of the species and the presence of a unique group I intron located within the small subunit rDNA. Sequences obtained for the three isolates were identical, indicating that they were the same strain.CONCLUSIONS:The first direct connection between human disease and A. griffini is reported from a case of Acanthamoeba keratitis. The type strain of this species was isolated from a marine environment, but the disease-causing strain ws isolated from a domestic water supply. The DNA sequences obtained confirmed unequivocally the epidemiologic association between a keratitis-causing strain of Acanthamoeba, the contact lens storage case, and the domestic water supply.

A prospective, randomised, double blind, partial crossover, placebo controlled trial has been conducted to compare the performance of topical fusidic acid gel (Fucithalmic) and oral oxytetracycline as treatment for symptomatic chronic blepharitis. Treatment success was judged both by a reduction in symptoms and clinical examination before and after therapy. Seventy five per cent of patients with blepharitis and associated rosacea were symptomatically improved by fusidic acid gel and 50% by oxytetracycline, but fewer (35%) appeared to benefit from the combination. Patients with chronic blepharitis of other aetiologies did not respond to fusidic acid gel but 25% did benefit from oxytetracycline and 30% from the combination. Our results demonstrate the need to investigate patients with blepharitis for concomitant rosacea as they respond well to targeted therapy.

Necrotizing fasciitis is a rare, but life-threatening emergency. We report a case history of necrotizing fasciitis in a previously healthy woman. A review of the literature suggests that this is the first report of necrotizing fasciitis complicating total hip replacement surgery.

SUMMARYThis study evaluated the epidemiology ofPseudomonas aeruginosakeratitis in contact lens (CL) wearers; the relationships between CL storage case contamination and CL hygiene practice and between CL hygiene and the development of keratitis. Sixteen CL wearers with keratitis were compared with 44 asymptomatic controls. Lens hygiene practice was assessed and CL care materials, domestic water sites and endogenous sites were evaluated microbiologically. Poor CL hygiene was not associated withPs. aeruginosakeratitis. There was an association between keratitis and bacterial contamination of the CL and storage case (P < 0·0005). Lens and storage case contamination were not significantly associated with poor hygiene. No domestic or endogenous source forPs. aeruginosawas found. Causative organisms may be derived from other sources, but CLs and CL storage cases provide a favourable environment forPs. aeruginosacolonization. Changing the CL care environment to one less favourable forPs. aeruginosamay help to eliminate this problem.

Surveillance for Legionella presents infection control personnel with a complex task. Regular bacteriological monitoring of water supplies has still not led to eradication of legionnaires' disease. More sensitive detection methods, novel engineering practice, targeting of compromised people and awareness of its natural history involving biofilms and amoebae may permit the elimination of Legionella from man-made water systems.

Microbial keratitis can occur in association with contact lens wear. The absolute risk of infection is low but may be enhanced as a consequence of increased exposure to potentially pathogenic microbes in a hospital setting. There is variation in risk depending on type of lens worn and its modality of use. Extended-wear lenses carry the greatest risk. Pseudomonas aeruginosa and Acanthamoeba are causes of potentially devastating ocular infections in contact lens wearers. The risk of these infections could be reduced by fastidious hygiene practice. Hydrogen peroxide disinfection is recommended when a storage case is included in the care regimen. This should be cleaned thoroughly and dried prior to disinfection and never exposed to tap water. Daily wear of one-day 'disposable' soft contact lenses or use of rigid gas permeable lenses is recommended for hospital staff. Contact lenses should be removed immediately and discarded or disinfected if the eye becomes contaminated and/or use of an eyewash is required.

many vulnerable workers in such enterprises. There is little evidence that voluntary action by employers protects the health ofworkers in deregulated workplaces or activities. Information collected before the passage ofthe 1974 Health and Safety at Work etc Act showed the abysmal failure of self regulation and voluntarism to protect employees' health and safety in the workplace. In 1983 the House of Lords Select Committee on Occupational and Hygiene Services documented their failure specifically to affect occupational illhealth. Without regulations, no progress has been made on implementing the committee's specific recommendations for improving health services in the workplace.17 Market forces have a sad and unsuccessful history in maintaining health and safety in the workplace: Adam Smith believed that hazardous work would be done only by workers who, in the marketplace, would expect high wages for dangerous tasks. The wage costs for hazardous industries would be so high that companies would devise ways of reducing the hazards and hence lower wages could be introduced without health and safety regulations adversely affecting the companies. But in Britain (as elsewhere) many hazardous industries employ mainly low paid and vulnerable workers. The European Union has stimulated considerable activity in health and safety with a series of important directives. These may be unevenly implemented throughout the union, but many people in Britain have welcomed them because they provide clear and in some instances new approaches and standards on neglected hazards. It now seems that the government wants to push health and safety back to basics and restore Victorian values and Victorian accident rates and rates of ill health with its proposals. This could create more conflict with the European Union, which has already begun proceedings against Britain this year for failing to implement some of last year's health and safety directives.'0 We should oppose sweatshop thinking on occupational health and call for the maintenance of existing occupational health controls at the very least. What is needed is the retention of effective health and safety laws, restoration of the Health and Safety Commission's budget, expansion of the field inspectorate of the Health and Safety Executive, more information on health and safety in the workplace, and support for small and medium sized businesses. The very opposite ofthis has happened or is about to happen.

SUMMARYThe investigation, epidemiology, and effectiveness of control procedures during an outbreak of Legionnaires' disease involving three immunosuppressed patients are described. The source of infection appeared to be a network of fire hydrant spurs connected directly to the incoming hospital mains water supply. Removal of these hydrants considerably reduced, but failed to eliminate, contamination of water storage facilities. As an emergency control procedure the incoming mains water was chlorinated continuously. Additional modifications to improve temperature regulation and reduce stagnation also failed to eliminate the legionellae.A perspex test-rig was constructed to model the pre-existing hospital water supply and storage system. This showed that through the hydraulic mechanism known as ‘temperature buoyancy’, contaminated water could be efficiently and quickly exchanged between a stagnant spur pipe and its mains supply. Contamination of hospital storage tanks from such sources has not previously been considered a risk factor for Legionnaires' disease. We recommend that hospital water storage tanks are supplied by a dedicated mains pipe without spurs.

Legionella pneumophila released from their intracellular location within trophozoites of Acanthamoeba castellanii , grew only on the ‘tail’ of a streaked inoculum; this observation was suggestive of bacterial growth inhibition by a factor or factors derived from the amoebae. Similar lysates have, in the past, been found by others to contain Legionella which were non-cultivatable on a laboratory agar but could infect guinea pigs. This inhibition was confirmed using lysates from stimulated amoebae on a lawn of growing bacteria and shown to be due to the production of hydrogen peroxide. This inhibitory effect could be reversed with catalase which should be added to amoebal lysates which are being cultured in the laboratory for Legionella .

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