Detection of Dientamoeba fragilis by culture.

Symptoms associated with Dientamoeba fragilis include diarrhoea, abdominal pain, nausea, vomiting, epigastric pain and weight loss. A possible link between D. fragilis and irritable bowel syndrome (IBS)-like symptoms has been reported, and therefore the presence of this parasite should be excluded before making a diagnosis of IBS. Over a six-month period, 976 faecal samples were submitted to NPHS Microbiology Aberystwyth for routine microbiological analysis. All samples were also cultured for parasites using Robinson's xenic medium. Trichrome staining was undertaken whenever practicable, but many stools had insufficient material. D. fragilis was isolated from 25 (2.6%) patients, whereas Cryptosporidium spp. was detected in 16 (1.6%) patients. D. fragilis was only detected in nine (1.3%) out of 685 specimens stained with trichrome, although four of the 25 culture-positive stools had insufficient sample for staining. Parasite culture proved to be less laborious than trichrome staining and dramatically increased D. fragilis detection rate.

Incidence of Blastocystis hominis in faecal samples submitted for routine microbiological analysis.

Over a one-year period, 1390 faecal samples were submitted to Aberystwyth Public Health Laboratory for routine microbiological examination. All were stained using a commercial trichrome method. Blastocystis hominis was detected in 96 (6.9%), making it the most common parasite found in the study. Of the B. hominis-positive specimens, 73% were missed on direct microscopy. Molecular typing of B. hominis has revealed extensive genetic diversity in morphologically identical strains and thus detection by microscopy alone may not be sufficient to confirm the role of this organism in human disease.

Cat-scratch disease: epidemiology, aetiology and treatment.

Cat-scratch disease (CSD) is a clinical syndrome that usually presents as a self-limiting lymphadenopathy associated with a cat scratch or bite. Commonly affecting children and young adults, it has a worldwide distribution. In temperate climates, higher rates are reported in the autumn and winter, which can be attributed to the seasonal breeding of the domestic cat. The organism responsible was identified in 1983, having eluded detection for 50 years. Initially, Afipia felis was thought to be the cause; however, subsequent study failed to confirm a link. During the 1990s, it was demonstrated conclusively that Rochalimaea henselae, later reclassified as Bartonella henselae, was the cause of CSD. B. henselae has been isolated from bacteraemic cats, with transmission among cats thought to be via the cat flea. Although other Bartonella species are transmitted by arthropod vectors, it is unlikely that the cat flea is involved directly in human infection, but plays a role in amplifying the reservoir. B. henselae is difficult to culture, and either serology or the polymerase chain reaction are considered to be the best methods of detection. Genetic variation occurs amongst B. henselae strains, perhaps explaining the inconsistency of some diagnostic techniques. A separate serogroup (Marseilles) has been reported in a seronegative patient with CSD, and B. clarridgeiae has the potential to cause the disease. Atypical presentation is seen in up to 25% of cases, and manifests itself as ocular involvement, encephalopathy, granulomatous hepatitis, hepatosplenic infection, endocarditis and osteomyelitis. The majority of CSD cases resolve spontaneously and do not require antibiotic treatment. In complicated CSD, treatment with trimethoprim-sulphamethoxazole, ciprofloxacin or azithromycin is recommended, with gentamicin being reserved for the severely ill patient.

Atypical outbreak of caprine cryptosporidiosis in the Sultanate of Oman.

An outbreak of cryptosporidiosis occurred in goats ranging in age from two days to adult, on a well-managed closed farm. None of the other animals on the farm, including sheep, cows and buffalo, were affected. Morbidity approached 100 per cent in goats less than six months of age. Despite intensive supportive care, 238 goats died, ranging in age from two days to over one year. Cryptosporidia were detected in large numbers in the intestinal contents of dead animals and in faecal smears of animals with diarrhoea. Massive numbers of the organisms were also demonstrated histopathologically and by electronmicroscopy, and no other significant pathogens were detected. The outbreak was unique in terms of the extreme virulence of the organism, its apparent species-specificity, and the shedding of the organism by animals over four weeks of age.

Pneumocystis carinii infection in human immunodeficiency virus-positive patients.

Pneumocystis carinii is a ubiquitous, atypical unicellular fungus. P. carinii pneumonia (PCP) is responsible for considerable morbidity and mortality in acquired immune deficiency syndrome (AIDS) patients, and is the leading complication in advanced human immunodeficiency virus (HIV) infection. Many different host (mammal)-specific species of Pneumocystis exist, but the life-cycle is not understood fully. Human strains are designated as P. carinii f. sp. (special form) hominis (at least 59 different types). P. carinii is spread via the airborne route. Disease is most frequently caused by fresh exposure to a source of P. carinii, rather than by reactivation of latent infection. Asymptomatic carriage among healthy persons may occur. PCP occurs in HIV-infected patients when the CD4+ count falls below a certain threshold; organisms multiply and gradually fill the alveoli. Symptoms, which include a mildly productive cough, progressive dyspnoea and fever, may persist for months prior to diagnosis. Without treatment, progressive respiratory insufficiency invariably ends in death. Pulmonary specimens may be obtained by procedures of varying sensitivity and risk. Diagnosis is usually confirmed by detection of stained organisms; however, staining procedures vary in sensitivity and ease of use. Robust polymerase chain reaction (PCR) protocols with good predictive results may be useful in the future. Therapy falls into two categories: for acute primary infections and for prophylaxis. A confirmed diagnosis ensures that patients do not receive potentially toxic medication (adverse drug reactions can occur). Prophylaxis can dramatically reduce the frequency of PCP in HIV patients, and its more widespread use should lead to a decline in the incidence of PCP in the future.

Dientamoeba fragilis: the unflagellated human flagellate.

Dientamoeba fragilis is a pathogenic protozoan parasite with a world-wide distribution. Although originally described as an amoeboid organism, it has been reclassified as a flagellate, on the basis of a number of electron microscopic and immunological findings. Except for its lack of a flagellum, D. fragilis closely resembles Histomonas and Trichomonas. Interestingly, a resistant cyst stage has not been demonstrated and it is unlikely that its trophozoites can survive successfully outside the human host. As a consequence of its higher than anticipated coincidence of infection with Enterobius vermicularis, transmission may occur via ova of this pinworm. D. fragilis infection may be acute or chronic, and has been reported in both children and adults. The most common clinical symptoms include abdominal pain, persistent diarrhoea, loss of appetite, weight loss and flatulence. Occasionally, eosinophilia, urticaria and pruritus have been described. Demonstration of the characteristic nuclear structure of D. fragilis, needed for a definitive diagnosis, cannot be achieved in unstained faecal material; therefore, permanently stained smears are essential. Treatment is recommended in symptomatic cases, and iodoquinol, tetracycline and metronidazole have been used successfully.

Incidence of Dientamoeba fragilis in faecal samples submitted for routine microbiological analysis.

Over a six-month period, 857 faecal samples were submitted to the Department of Microbiology and Immunology at Sultan Qaboos University Hospital in Oman, for routine microbiological examination. All samples were stained using the Gomori trichrome method. Trophozoites of Dientamoeba fragilis were detected in 41 (5.1%) patients, making it the most common enteropathogen found in the study. Of the patients with pure D. fragilis infection, 83% had abdominal pain, the duration of which varied from one month to two years. The use of permanently stained smears allowed detection of D. fragilis for the first time in the Sultanate of Oman.

Microsporidial infections in humans: current practice and developments in laboratory diagnosis.

Microsporidia are small, intracellular parasites that infect a wide range of hosts, including vertebrates, invertebrates and fish. They were discovered more than a century ago. The first well documented human case, however, was not reported until 100 years later. Since the first case of intestinal microsporidiosis was reported in 1985, numerous cases of microsporidiosis have been reported in immunocompromised patients, especially those in the later stages of human immunodeficiency virus (HIV) infection. Microsporidia also have been described in various other clinical conditions, including keratoconjunctivitis, sinusitis, peritonitis and myositis. The numbers of cases reported have risen dramatically since 1985, which can be explained partly by the acquired immune deficiency syndrome (AIDS) pandemic and partly by increased laboratory awareness. Some studies have shown that up to 50% of selected AIDS patients are infected with microsporidia. Diagnosis depended initially on the use of invasive techniques, namely histological examination of biopsy material. Since then, however, there have been important advances in the detection of microsporidial spores in clinical samples. Recent developments in the diagnosis of microsporidiosis are described, including light microscopy staining methods, fluorescent staining, electron microscopy and molecular techniques.

Serial concentrations of C-reactive protein as an indicator of urinary tract infection in patients with spinal injury.

C-reactive protein (CRP) was measured serially in 16 patients with an acute spinal injury. Twelve episodes of acute urinary tract infection (UTI) occurred during the study period. These were all associated with an increased concentration of CRP greater than 50 mg/l, which returned to normal after successful treatment. Thirteen episodes of asymptomatic bacteriuria associated with increased concentrations of CRP greater than 20 mg/l occurred, indicating tissue damage. More commonly, significant bacteriuria was associated with normal concentrations of CRP, and presumably, simple colonisation of the urinary tract, which, we suggest, does not require treatment with antibiotics. Serial measurement of CRP in patients with spinal injury may help distinguish between urinary tract colonisation and infection and be useful in monitoring the response to the treatment of clinical UTI.