To determine the timing of symptoms and oocyst excretion after the acquisition of cryptosporidium infection, we used a screening parasitologic stool examination to identify patients and then contacted them for the collection of retrospective histories and follow-up stool specimens. The study included 68 otherwise healthy patients with an identifiable source and time of infection. All 68 had diarrhea, 61 had abdominal pain, most also had other gastrointestinal symptoms, 33 had fever, and all recovered spontaneously. Among the 50 patients who submitted follow-up stool samples, more than 90 percent of the 610 symptomatic days and of the 136 oocyst-positive stools occurred between days 7 and 28 of infection, the mean incubation period was 7.2 days (range, 1 to 12), and the mean duration of illness was 12.2 days (range, 2 to 26). During the oocyst-excretion period cryptosporidium was detected in 90 percent of Ziehl-Neelsen-stained fecal concentrates. The end of oocyst excretion could be accurately determined in 26 patients; 19 (73 percent) had positive stools after the cessation of symptoms for a mean period of 6.9 days (range, 1 to 15). Fourteen patients were studied for two or more months, and in three of them asymptomatic episodes of oocyst excretion were detected up to two months after clinical recovery. We conclude that many cases of symptomatic cryptosporidiosis occur among immunocompetent patients, some of whom may excrete oocysts even when they have become asymptomatic. Conversely, infected symptomatic patients may occasionally have intermittently negative stools.

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The complement system is a first-line defence mechanism against parasites. All parasites causing deep infections and getting into contact with human plasma must, in one way or another, avoid the destructive effect of this powerful defence system. Several specific strategies of complement resistance of parasites have been reported, and this rather large spectrum of regulatory mechanisms covers the whole cascade of complement activation. Analysis of the known and elucidation of the yet unknown mechanisms will probably help in the development of new therapeutic and preventive approaches to control the different parasitic diseases. This paper will review the complement resistance mechanisms reported and their utilization by various parasites.

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A 51-year-old renal transplant patient, whose spleen had been removed 11 years ago, was admitted to hospital for elective surgery, which was cancelled as she developed spiking fever and nonproductive cough and her general condition deteriorated. After 2 weeks, leishmaniasis was unexpectedly diagnosed from a bronchoalveolar lavage specimen, which had been subjected to parasitological examination under the suspicion of pneumocystosis. Isoenzyme typing identified the parasite as Leishmania infantum. The patient had visited Malaga, Spain, twice a year, the last trip taking place 1 month before admission. Specific treatment was followed by rapid recovery without relapse during 1.5 years. Splenectomy and immunosuppressive medication obscured the clinical suspicion of leishmaniasis. The case is a reminder of the interstitial pneumonitis in leishmaniasis and emphasizes the value of broad-spectrum methods detecting a variety of parasites.

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We studied the bacteria in consecutive peritonsillar abscesses using semiquantitation of the primary culture findings and correlated the results to clinical parameters. Puncture-aspirated pus from 42 abscesses yielded 133 isolates. Group A streptococci were isolated 10 times and, unlike other bacteria, were isolated 4 times in pure culture; other beta-hemolytic streptococci were found in 8 abscesses, and anaerobes were found in 28. The infections were polymicrobial, with two to seven bacteria in 83%. Anaerobes were more abundant than nonanaerobes; members of the genera Streptococcus, Bacteroides, Peptostreptococcus, and Fusobacterium were the most important quantitatively, considering both frequency and abundance. In patients with ongoing antibiotic treatment, nonanaerobes (but not anaerobes) were less abundant than in untreated patients. The abundance of obligate anaerobes (specifically cocci and gram-positive rods) correlated to the severity of illness as defined by fever and short duration before hospitalization. With other groups of bacteria, no such correlation was found. The correlation was not explained by a difference between the antibiotic-treated and the untreated patients. The results indicate the value of the semiquantitation of culture data and the frequency and pathogenic significance of obligate anaerobes in peritonsillar abscesses.