TRACING OF LABORATORY CONTAMINATION: QUALITY CONTROL APPROACH

471

tiny inoculum, part of which must have been washed out with soap and water. In experiments in rabbits, 4 x 10’ parasites were required to cause a mild, occasional parasitaemia in 14 days. Our case suggests that T gambiense has a high affinity for human tissues. Department of Haematology, College of Medical Sciences, University of Calabar, Calabar, Nigeria

A. O. EMERIBE

INTERFERON AND MYALGIC ENCEPHALOMYELITIS

SIR,- Lymphokines including interferon may be the mediators of the fatigue in myalgic encephalomyelitis or postinfection fatigue syndrome (PIFS), perhaps after secondary release to a low grade persistent intracellular infection.1,2 McDonald et al,3noting the neuropsychiatric symptoms and fatigue commonly reported in patients who receive recombinant alpha-interferon, were reminded of the clinical features of the postviral syndromes. Studies of the interferon system in patients with this disorder have been equivocal. Circulating interferon was not found in a small sample of patients thought to have such a syndrome secondary to chronic Epstein-Barr virus infection.’ However, increased levels of 2’-5’-oligo-adenylate synthetase, a cellular enzyme specifically induced by interferon, have been demonstrated in such patients.4,5 We examined the sera of patients with PIFS and control subjects for circulating gammainterferon (IFN-&ggr;) and also measured the serum levels of neopterin, an intermediate in the synthetic pathway of biopterin and a reliable marker of IFN-y activity.6 These mediators were chosen because IFN-y is the major cytokine released by T cells after viral or other intracellular infection; neopterin is preferentially induced by IFN-y rather than by other cytokines.6 52 consecutive patients (35 females) who fulfilled 6ur diagnostic criteria for PIFS2 entered the study. All had been persistently symptomatic for at least 6 months (range 6-180). 20 healthy adults (11 females) were the controls. Serum IFN-y levels were measured with a solid-phase radioimmunoassay (Centocor, USA), and neopterin levels were measured by radioimmunoassay with a double-antibody technique (Henning, Berlin). IFN-y was undetectable in the serum of 39 of the patients (75%) and in 8 of the controls (40%). Low levels of interferon were found in the remaining samples (below 1-2 U/ml). There was no significant difference between patients and controls. Mean serum neopterin values in the patients were similar to those of the controls: 10-2 (8-6) nmol/1. The results indicate that subjects with PIFS do not have an increased serum IFN-y level. This does not exclude the possibility of a local increase of IFN-y or other lymphokines at specific sites in the central nervous system in such patients. IFN-y has a short serum half-life and may therefore become undetectable in serum samples despite ongoing or local interferon activity in vivo. Furthermore in patients with PIFS a local cell-mediated (T cell) immune response to intracellular pathogens in muscle and/or neural cells may elicit local interferon activity without producing a detectable change in serum interferon or neopterin levels. Measurement of these and other mediators in cerebrospinal fluid or other sites in the central nervous system of patients with PIFS may shed light on the pathogenesis of this disorder. 8

0 (SD 4-1) vs

Department of Immunology, University of New South Wales, Prince Henry Hospital, Sydney, Australia

ANDREW LLOYD DAVID ABI HANNA DENIS WAKEFIELD

1. Wakefield D, Lloyd A. Pathophysiology of myalgic encephalitis. Lancet 1987; ii: 918-19 2 Lloyd AR, Wakefield D, Dwyer J. The post-infection fatigue syndrome Fact or fiction? Aust NZ J Med (in press). 3. McDonald EM, Mann AH, Thomas HC. Interferons and mediators of psychiatric morbidity. an investigation in a trial of recombinant &agr;-interferon in hepatitis-B carriers Lancet 1987; ii: 1175-78. 4 Straus S, Tosato G, Armstrong G, et al. Persisting illness and fatigue m adults with evidence of Epstein-Barr virus infection. Ann Intern Med 1985; 102: 7-16 5 Morag A, Tobi M, Ravid Z, Revel M, Schattner A. Increased (2’-5’-oligo-A synthetase activity m patients with prolonged illness associated with serological evidence of persistent Epstein-Barr virus infection. Lancet 1982, i 744. 6 Huber C, Batchelor JR, Fuchs D, et al. Immune response-associated production of neopterin. J Exp Med 1984; 160: 310-16.

CAPTOPRIL IN PATIENTS WITH ILEUS

SIR,-Dr Flynn and colleagues report (Jan 23, p 173) the use of intravenous captopril in patients with postoperative ileus. The sublingual route might have been appropriate in this situation. We have given 25 mg captopril sublingually to eight salt-replete, supine healthy male volunteers. All reported complete dissolution of the tablet within 10 min. In venous blood sampled 55 min after the dose plasma renin activity rose from 0-99 (SEM 0-17) to 6-91 (2-10)

indicating angiotensin-converting-enzyme ng/ml/h (p<0001), inhibition. Sublingual captopril may be a simple and effective administration. Department of Pharmacology

pharmacologically

and Clinical Pharmacology, Ninewells Hospital, Dundee DD1 9SY

alternative

to

intravenous

JOHN J. MCMURRAY ALLAN D. STRUTHERS

"BLIND" LABORATORY ANALYSIS

SIR,-In studies reported in The Lancet specimens have often been collected from groups of patients and controls and sent to a laboratory for tests. The results may show that, for instance, markers of a certain virus infection are significantly more common in patients than in controls, and it is inferred that the virus is the cause of the patients’ disease. What is frequently not revealed is whether the laboratory workers knew which specimens came from patients and which from controls and, if they did not, how this was concealed from them. Many virological tests depend on appearances in tissue culture and microscopy, and the extent to which investigations are pursued often depends on an early subjective decision about these appearances. Admittedly, it is possible to read tests objectively by machines such as ELISA readers, but even then choices such as how often to repeat a test have to be made. Whatever the investigation, therefore, it is preferable that patient and control specimens be mixed and coded so that the laboratory deals with them "blind". Researchers who fail to do "blind" laboratory analysis weaken the impact and validity of their findings unnecessarily. Virus Reference Laboratory, Central Public Health Laboratory, London NW9 5HT

PHILIP P. MORTIMER

TRACING OF LABORATORY CONTAMINATION: QUALITY CONTROL APPROACH

SIR,-Beaumont1 found blood on various surfaces in the suggested that the contamination resulted from a breakdown in good work-practices. Most probably this was after indiscriminate touching of surfaces with contaminated gloves. We have found widespread contamination with serum and failure of basic hygiene practices after the introduction of simulated patients’ samples containing tracers into a routine clinical chemistry laboratory. The samples were horse serum containing spores of Bacillus subtilis variety globigii (NCTC 10073, Microbial Technology Laboratory, Porton Down, Wiltshire), 108 colony-forming units per ml, and 0-1% ’Uvitex NFW’, a liquid optical brightener (Hughes and Hughes, Romford, Essex). Fluorescence from the brightener was detected under ultraviolet light and affected surfaces were swabbed, plated onto nutrient agar, and then incubated

necropsy room and

aerobically at 37°C for published elsewhere.

16 h. More details of the

technique will be

Fluorescence with tracer spores was detected on gloves, equipment, and bench surfaces that had been used to handle the test sera.

In

some

instances, the smeared pattern of fluorescence,

together with a positive culture, suggested inadequate attempts to deal with a spill. In the laboratory that was studied, samples from patients infected with hepatitis B virus and human immunodeficiency virus are occasionally handled. This double-tracer technique can be used to make staff more aware of the potential infection hazards posed by contaminated surfaces. Moreover, the photographs of areas where both tracers are detected will help to reinforce the impact of training

472 sessions and will enable comparisons to be made. Accordingly we are planning the regular introduction of tracer-samples to assess the quality of laboratory hygiene practices in a similar way to the quality control samples that are used to assess analytical performance. Supplies Technology Division, NHS Procurement Directorate, 14 Russell Square, London WC1B 5EP Department of Biochemistry, St Stephen’s Hospital, London 1. Beaumont LR. The detection of blood

D. A. KENNEDY

J. F. STEVENS

nonporous environmental surfaces: an approach for assessing factors contributing to the risk of occupational exposure to blood in the autopsy suite. Infection Control 1987; 8: 424-26. on

OPPORTUNISTIC PNEUMONIA CAUSED BY LEGIONELLA BOZEMANII

SIR,- The most well-known species of the genus Legionella are L pneumophila and L micdadei (the Pittsburgh agent). We describe here three cases of pneumonia in immunosuppressed patients due to L bozemanii, a little known species with only one clinical case previously reported in Europe.! Our diagnoses were made by culture of bronchoalveolar lavage fluid and pleural aspirates and would not otherwise have been made. L pneumophila infection is usually diagnosed serologically or by a fluorescence assay on bronchial secretions. Neither test will detect L bozemanii and since it is not usual to culture for Legionella spp, which are fastidious organisms, L bozemanii (or indeed other Legionella spp) may often be missed as a cause of pneumonia in immunocompromised

patients. Case 1 (F, 44; heart transplant recipient, admitted in congestive cardiac failure; on immunosuppression with cyclosporin, azathioprine, and prednisolone).-She responded to diuretics and dopamine but 7 days after admission became pyrexial with a recurrence of pleural effusion. Blood cultures, viral titres, and. a serological atypical pneumonia screen (including L pneumophila were negative. After an emergency re-transplantation severe pyrexia developed. Culture of preoperative pleural and peritoneal aspirates grew L bozemanii but by the time erythromycin and rifampicin could be started disseminated intravascular coagulation had developed, and the patient died. Case 2 (F, 60: Wegener’s granulomatosis).-She presented with a 10 day history of dry cough, pleuritic chest pain, breathlessness, and fever. She was on cyclophosphamide and prednisolone. A chest X-ray revealed right basal shadowing and consolidation in the right lower lobe. Blood cultures and serological tests for atypical pneumonias were negative. Bronchoscopy and bronchoalveolar lavage were done but no pathogens (including Pneumocystis carinii) were seen in stained smear preparations. Culture of bronchial washings grew L bozemanii after 3 days’ incubation. The patient responded rapidly to erthromycin and rifampicin. Case 3 (M, 48; heart transplant recipient on cyclosporin, azathioprine, and prednisolone).-A rejection had been managed by methylprednisolone and antithymocyte globulin. On the 33rd postoperative day he became pyrexial and a right pleural effusion was noted. Blood cultures and serological tests for atypical pneumonias were negative. The pleural fluid contained numerous polymorphs but no organisms were seen on stained smear preparations. Culture of pleural fluid was initially negative but bronchoalveolar washings yielded a moderate growth of Haemophilus influenzae and he was treated with ampicillin. The washings were negative both for common viruses and for P carinii. The patient felt increasingly unwell, with abdominal pain and an acute polyarthropathy. After 3 days’ incubation L bozemanii was isolated from the pleural aspirate and ciprofloxacin was given, followed by rapid resolution of the pleural effusion. L bozemanii was subsequently cultured from the bronchial washings. L bozemanii was first isolated from guineapigs inoculated with material from the lungs of a diver who had died of extensive bronchopneumonia.2 Of eleven published culture-positive cases of pneumonia due to L bozemanii nine have been in In five cases infection was thought contamination of a hospital water supply.3 Our three cases were in two wards in the same hospital block over an 8 month

immunocompromised patients. to

be due

to

L bozemanii has been associated with water, 1,3and we have isolated L bozemanii from water outlets within the building. Further environmental studies are in progress. The clinical findings in our patients included, besides the pneumonia, hyponatraemia (two), abnormal hepatic function (one), acute polyarthropathy and abdominal pain (one), pleural effusion (two), and radiological evidence of cavitation (one) but none of these features are specifiç4 and they are not helpful in predicting the causative organism. However, two patients recovered rapidly with appropriate antibiotics, emphasising the importance of correctly identifying the organism responsible. We identified L bozemanii only because we routinely culture all bronchoalveolar lavage and pleural aspirate specimens from immunocompromised patients for both Mycoplasma and Legionella spp. We would have missed the diagnosis had we relied on serological or direct fluorescent antibody testing. A specific culture appropriate for Legionella Spp5 should be included in the investigation of opportunistic pneumonia.

period.

We thank Mr J. Taylor, Public Health Laboratory, Newcastle upon Tyne, for the serological testing.

Regional Cardiothoracic Unit and Department of Microbiology, Freeman Hospital, Newcastle upon Tyne NE7 7DN

C. R. SWINBURN F. K. GOULD P. A. CORRIS T. L. HOOPER N. J. ODOM R. FREEMAN C. G. A. MCGREGOR

RG, Psavol G, Newnham RS. Pneumonia due to Legionella bozemanii. first report of a case in Europe. J Infect 1984; 8: 251-55. 2. Bozeman FM, Humphries JW, Campbell JM. A new agroup of rickettsia-like agents recovered from guinea pigs. Acta Virol 1986; 12: 87-93. 3. Parry MF, Stampleman L, Hutchinson JH, et al. Waterborne Legionella bozemanii and nosocomial penumonia in immunosuppressed patients. Ann Intern Med 1985; 103: 205-10. 4. Woodhead MA, MacFarlane JT. Comparative clinical and laboratory features of legionella with pneumococcal and mycoplasma pneumonias. BrJ Dis Chest 1987, 81: 113-39. 5. Edelstein PH. Improved semi-selective media for the isolation of Legionella pneumophila from contaminated clinical and environmental specimens. J Clin Microbiol 1981; 14: 298-303 1. Mitchell

LISTERIOSIS AND FOOD-BORNE TRANSMISSION

SIR,-Dr McLauchlin and colleagues (Jan 23, p 177) highlight the increase in cases of listeriosis in Britain and the possibility that the origin of geographical clusters may be foodborne. Two large outbreaks associated with the consumption of soft cheese contaminated with Listeria monocytogenes in the United States1 and Switzerland2 have caused concern worldwide, and various cheeses and other dairy products, not incriminated in illness but yielding the organism, have been removed from sale in the United States and Australia, and in several European countries. Isolation of L monocytogenes from soft cheeses3-5 prompted us to do a similar study between March and December, 1987, on a wide variety of cheeses purchased from shops, supermarkets, and delicatessens in England. A full report will appear elsewhere. In most of the positive samples shown in the table, levels of L monocytogenes were below 102/g, but 9 of the 12 positive French cheeses contained between 10’ and 105/g. Although little is known about either the infectious dose of L monocytogenes or other events leading to infection, we believe that such high levels should be regarded as unacceptable in a ready-to-eat food that is usually stored at 4°C, a temperature at which the organism can multiply. L monocytogenes was also isolated at low levels from 60 of 100 raw chickens from various retail outlets and we are concerned about the possibility of cross-contamination to other foods. The examination of a wide range of foods including cured and fermented meats, raw salad vegetables, and seafoods is now in progress. Results from these and other surveys together with the development of new typing schemes should help to assess the contribution of contaminated food to the epidemiology of listeriosis. To our knowledge, the cheese and raw chickens examined in the above surveys were not implicated in illness during 1987. Nevertheless, the Department of Health and Social Security organised recently a meeting with trade federations and the