Pestilence, Plague and Pandemics: A Troubled History.

Humankind has lived with the danger of endemic, epidemic and pandemic disease for thousands of years. The effects of these outbreaks have often devastated human populations. Sixteen pandemic events causing an estimated 147 million deaths have occurred since the eighth century, The Black Death and the influenza pandemic of 1918-1920 probably having the greatest impact. Animal populations, both wild and domestic, have similarly suffered devastating outbreaks of disease which, on occasions, have translated into serious effects on human health. The deliberate or accidental introduction of animals into virgin areas has given rise to unforeseen disease events occasionally leading to extinction. Similarly, human intent or negligence and the vagaries of nature itself has resulted in ill health and loss of life. This paper describes the history of pandemics, epidemics and disasters, and the attempts to bring them under control.

A SHORT HISTORY OF OCCUPATIONAL DISEASE: 2. ASBESTOS, CHEMICALS, RADIUM AND BEYOND.

Historically, the weighing out and manipulation of dangerous chemicals frequently occurred without adequate protection from inhalation or accidental ingestion. The use of gloves, eye protection using goggles, masks or visors was scant. From Canary Girls and chimney sweeps to miners, stone cutters and silo fillers, these are classic exemplars of the subtle (and in some cases not so subtle) effects that substances, environments and practices can have on individual health.

A SHORT HISTORY OF OCCUPATIONAL DISEASE: 1. LABORATORY-ACQUIRED INFECTIONS.

Laboratory-acquired infections are as old as laboratories themselves. As soon as the culture of microorganisms was introduced, so too was their transfer to laboratory workers. It is only in relatively recent history that such infections have been fully understood, and methods of spread and their prevention or avoidance developed. This paper endeavours to provide an overview of the history of laboratory-acquired infection and the steps taken, particularly in the UK, for its prevention.

A SHORT HISTORY OF OCCUPATIONAL DISEASE: 3. LEISURE CAN MAKE YOU SICK.

The risk of infection associated with occupations can, and does, extend to certain leisure and sports activities. Generally, such pastimes are regarded as important for human health and mental wellbeing. However, infections may, rarely, be acquired during leisure activities that include water sports and water-related relaxation, and certain sports.

Comparative evaluation of the VITEK 2 Advanced Expert System (AES) in five UK hospitals.

OBJECTIVES: We carried out an evaluation of VITEK 2 in five UK laboratories, comparing results with 'gold standard' agar-dilution MIC data, assessing its ability to recognize resistant phenotypes and comparing results with those generated by routine antimicrobial susceptibility testing methods. METHODS: Laboratories tested a collection of 82 strains selected on the basis of their challenging and characterized resistance mechanisms. RESULTS: In comparison with the reference MIC method, VITEK 2 gave an essential agreement of 304/315 (enterococci), 1619/1674 (staphylococci) and 2937/3074 (Gram-negative bacilli): overall 96.0% agreement. Corresponding category (SIR) agreements with VITEK 2 were 247/252, 1496/1561 and 2478/2626 (overall 95.1%). Using five routine methodologies, category agreements ranged from 58/63 to 45/45; 222/232 to 174/174, and 333/372 to 250/259 for the three organism groups with an overall agreement of 95.0%. In contrast to VITEK 2 Advanced Expert System (AES), routine microbiology laboratories did not attempt to detect resistance mechanisms for every antibiotic studied. VITEK 2 AES detected all 19 resistance mechanisms in enterococci: where applicable, routine methods detected 14, 10 and 10. Of 30 resistance mechanisms in staphylococci, VITEK 2 AES detected 25 compared with 23, 20, 17 and 18 detected by routine methods. Finally, of 44 resistance mechanisms in Gram-negative bacilli, VITEK 2 AES detected 30 compared with 30, 23, 15 and 10 detected by routine methods. CONCLUSIONS: VITEK 2 performed susceptibility tests accurately and the AES detected and interpreted resistance mechanisms appropriately. Heavy inocula in a liquid medium possibly favour better expression of certain resistance determinants. Although certain routine microbiology methods performed adequately, VITEK 2 AES offers a rapid, standardized method suited to laboratories lacking experience of resistance mechanisms and/or those not testing an appropriate number, or range, of antibiotics to detect resistance phenotypes.

Evaluation of the oxoid dryspot streptococcal grouping kit for grouping beta-hemolytic streptococci.

The latex agglutination kits that are widely used for grouping of beta-hemolytic streptococci in clinical laboratories use liquid latex suspensions. The Oxoid Dryspot kit (Oxoid Ltd., Basingstoke, Hampshire, United Kingdom) uses predispensed latex dried onto reaction cards or cardboard strips. All streptococci of groups A (85 strains), B (87 strains), C (30 strains), D (38 strains), F (23 strains), and G (65 strains) were correctly grouped by using these reagents. The Oxoid Dryspot Streptococcal Grouping kit is a reliable method for grouping of the beta-hemolytic streptococci encountered in clinical laboratories.

Use of rapid dipstick tests to exclude urinary tract infection in children.

Children presenting with symptoms attributable to urinary tract infection (UTI) are not uncommonly referred to paediatric departments for assessment. The aim of this study was to evaluate the use of rapid dipstick tests in the diagnosis of urinary tract infection in children. Urine was collected from 375 children admitted to a general paediatric ward, in whom UTI was a possibility on clinical grounds. Of these, 124 were less than one year old. Urine was tested with a dipstick for the presence of nitrite and leucocyte esterase. Bacterial culture and examination for white cells, red cells and other formed elements were performed. The results of the dipstick tests, microscopy and culture were correlated with the clinical details. Combination of a negative dipstick test for nitrite and leucocyte esterase showed a negative predictive value for UTI of 96.9% and a specificity of 98.7%. In children less than a year old these values were 96.7% and 99.2% respectively. The leucocyte esterase strip test showed a negative predictive value for pyuria of 94.3% with a specificity of 86.9%. In children less than a year old these values were 93.1% and 84.4% respectively. The use of dipsticks for the detection of urinary nitrate and leucocyte esterase in daily clinical practice is recommended. In children, the absence of both nitrite and leucocyte esterase in urine indicates that UTI is unlikely; however, positive dipstick tests for nitrite and/or leucocyte esterase are not specific indicators of UTI, and should not be used in place of laboratory examination. The dipstick method is most likely to be useful as a screening test to exclude UTI in children, but may be less suitable for infants. It should not be used to diagnose urinary tract infection.

Potential for gene transfer among enterococci from a single patient and the possibility of confounding typing results.

The results of typing methods used in a study of the epidemiology of enterococci in burn patients showed inconsistencies. The possibility that these inconsistencies were the result of gene acquisition or loss was investigated by using 12 isolates of Enterococcus faecalis from a single patient. In vivo and in vitro exchange and loss of genes were observed. The study showed that the typing results for isolates from this patient can be modified by known and demonstrated genetic elements; as a result, the isolates could be divided into between three and seven strains. In the present study, the SmaI digestion patterns gave the most consistent results, correctly identifying the transconjugants as indistinguishable from recipient strain 196R.

Evaluation of a modified nitrous acid extraction latex agglutination kit for grouping beta-hemolytic streptococci and enterococci.

The rapid and accurate identification of the Lancefield group of beta-hemolytic streptococci and enterococci is an important procedure in clinical laboratories. Latex agglutination techniques are more rapid and technically less demanding than traditional extraction-precipitation methods. Prolex (Pro-Lab Diagnostics, Richmond Hill, Ontario, Canada) is a latex agglutination kit which contains modified nitrous acid reagents to extract antigens and can be used to detect group D antigen in streptococci and enterococci, as well as group A, B, C, F, and G antigens. A total of 302 strains of streptococci and enterococci were tested with this kit. All streptococci of groups A (41 strains), B (39 strains), C (35 strains), D (3 strains), F (10 strains), and G (48 strains) were correctly grouped, as were 125 (97%) of 129 strains of enterococci. Prolex is a reliable method for grouping the beta-hemolytic streptococci and enterococci most frequently encountered in clinical laboratories.

Direct detection of groups A, C and G streptococci in clinical specimens by a trivalent colour test.

A simple trivalent colour test, developed for the rapid detection and identification of streptococci belonging to Lancefield groups A, C and G, was evaluated for sensitivity and specificity with cultures and when directly used with wound and throat swabs. In tests performed on cultures, all of 94 group A, 78 group C and 94 group G cultures were correctly identified. In direct tests on wound swabs, 49 of 52 group A, 17 of 19 group C and 48 of 51 group G streptococci were detected and correctly identified; no false positives were observed. With throat swabs from pharyngitis patients 34 of 36 group A, 3 of 6 group C and 5 of 8 group G streptococci gave positive results. Almost 10% of these swabs gave false positive reactions with the group C component of the test system. Samples taken from uninfected individuals indicated that the false positives were probably associated with blood group A. The test system gives rapid and reliable results with streptococcal cultures, but when directly applied to clinical samples the results must be interpreted with caution, particularly if the patient's blood group is not known.

Novel color test for rapid detection of group A streptococci.

A novel color test for the rapid detection of group A streptococci has been developed. The test, designed to be suitable for use in clinical laboratories as well as by less experienced personnel, incorporates the simplicity of latex tests with a color change to indicate the presence of group A streptococcal antigen. The test, which takes 5 min, was evaluated with 646 throat swabs, with a 15.6% incidence of group A streptococci; for swabs which yielded 10 or more group A streptococcal colonies in cultures, the sensitivity was 96.8%, and the specificity was 99.1%. In addition, the color test was 100% sensitive and specific when used to detect group A streptococcal antigen in beta-hemolytic colonies from culture plates.

Analysis of an outbreak of staphylococcal scalded skin syndrome: strategies for typing 'non-typable' strains.

Thirteen newborn babies were studied during an outbreak of scalded skin syndrome. Staphylococci isolated from seven babies were non-typable using the international set of typing phages; the remainder were of phage group II. In only one instance was there transmission of phage group II strains other than within families. However, 'heat treatment' and plasmid profiles of the non-typable strains showed that five of the seven babies were infected by strains which were indistinguishable. These five strains were more closely related to phage III staphylococci than to phage group II. The identity of the epidermolytic toxin has not been established.

The enrichment and early detection of Streptococcus pyogenes in skin lesions, using colistin, oxolinic acid, Todd Hewitt broth and latex agglutination.

An improved selective broth, colistin, oxolinic acid, Todd Hewitt broth (COTHB) for the isolation of Streptococcus pyogenes and other streptococci from swabs is described. Staphylococci, coryneforms and Gram negative organisms are inhibited in COTHB inoculated with swabs from skin lesions. Streptococcus pyogenes could be detected by a fluorescent antibody method and by the Streptex and Phadebact streptococcal grouping methods after 6 and 24 h incubation. Other streptococci of groups B, C and G, were also detected. Streptex was the most sensitive and specific method for the detection of streptococci of groups A, B, C, and G in this broth. The method detected 78% of these streptococci in COTHB after 6 h incubation and 93% after 24 h incubation. Of the Strep. pyogenes isolated, 82% were detected in the broth by the Streptex method.

Early detection of streptococci in swabs by latex agglutination before culture.

A commercial streptococcal grouping system was used to demonstrate streptococcal antigen in swabs before culture. The method detected 81% of the streptococci of groups A, B, C, and G subsequently isolated in culture. The method offers a sensitive and specific method for the early detection of beta-hemolytic streptococci.

Colistin-oxolinic acid-blood agar: a new selective medium for streptococci.

The development and evaluation of a new selective medium (colistin-oxolinic acid-blood agar) for streptococci is described. Streptococci of medical and veterinary importance grew well on the medium. Gram-negative organisms, staphylococci. Bacillus spp., and coryneforms are all inhibited. It was concluded that the medium is valuable for the isolation of streptococci in pure culture from mixed flora and has advantages over other media previously described. Increased isolation rates were obtained together with earlier identification of the isolated strains.