Prevalence of Cryptosporidium parvum infection in children along the Texas-Mexico border and associated risk factors.

We examined the epidemiology of Cryptosporidium parvum in children aged 6 months to 13 years living in 1) colonias along the border (n = 105), 2) a clinic in an urban border community (n = 65), and 3) clinics in a large urban nonborder area (n = 109). Serum IgG and IgA anticryptosporidial antibodies were measured by enzyme-linked immunosorbent assay (ELISA). Overall, 70.2% (196/279) of subjects had detectable C. parvum antibodies. Prevalence rates were higher (93/105 [89%]) in the colonias and urban border community (53/65 [82%]) compared to the urban nonborder community (50/109 [46%]). Within colonias, independent risk factors for C. parvum infection included consumption of municipal water instead of bottled water, older age, and lower household income. Children living along the Texas-Mexico border have a higher rate of infection with C. parvum compared to children living in a large nonborder urban area. Within colonias, C. parvum infection was associated with source of water supply, age, and socioeconomic status.

Experimental cryptosporidiosis in adult and neonatal rabbits.

Neonatal and adult New Zealand White rabbits were infected experimentally with Cryptosporidium parvum. No histologic evidence of infection was found in adult rabbits. However, increased levels of anti-cryptosporidial serum IgG were present, and multiple antigens were detected by serum on immunoblots. In neonates, variably severe, transient infection was present from Days 3 to 21 postinoculation. Serum IgG was initially elevated, decreased until Day 10 postinoculation, then progressively increased for the remainder of the study. A prominent 15 kilodalton antigen was detected on immunoblots using serum obtained on Days 14 until 28 postinoculation. Neonate anti-cryptosporidial fecal IgA were slightly elevated on Days 14 and 21 postinoculation.

Protozoal colonization of the intestinal tract in institutionalized Romanian children.

To determine the prevalence of intestinal parasitic infections in 92 Romanian children institutionalized at Colentina Hospital (Bucharest, Romania) and at the Dystrophic Center (Vidra, Romania), medical charts were reviewed and complete physical examinations were performed. The nutritional status of each child was evaluated, and their sera were tested for the presence of antibodies to human immunodeficiency virus (HIV) and Cryptosporidium. Fecal samples were collected in 10% formalin and examined by an immunofluorescent assay and by trichrome staining for intestinal parasites. At least one protozoan was identified in 77% of the fecal specimens examined. Giardia lamblia (72% of cases), Cryptosporidium parvum (12%), and Entamoeba coli (4%) were the only parasites identified. Stepwise logistic regression revealed that the only factors predictive of giardia colonization were normal nutritional status (P < .01) and HIV seropositivity (P < .02), while cryptosporidium colonization was only associated with where the children lived (P < .01). Seventy-three percent of the children had IgA and/or IgG antibodies to Cryptosporidium in their sera. The presence of these antibodies was strongly associated with the severity of symptoms present in the HIV-infected children (P < .01). Protozoal colonization of the intestinal tract is common in institutionalized Romanian children and may play a role in causing morbidity and mortality in this high-risk group of children.

A Cryptosporidium parvum genomic region encoding hemolytic activity.

Successful parasitization by Cryptosporidium parvum requires multiple disruptions in both host and protozoan cell membranes as cryptosporidial sporozoites invade intestinal epithelial cells and subsequently develop into asexual and sexual life stages. To identify cryptosporidial proteins which may play a role in these membrane alterations, hemolytic activity was used as a marker to screen a C. parvum genomic expression library. A stable hemolytic clone (H4) containing a 5.5-kb cryptosporidial genomic fragment was identified. The hemolytic activity encoded on H4 was mapped to a 1-kb region that contained a complete 690-bp open reading frame (hemA) ending in a common stop codon. A 21-kDa plasmid-encoded recombinant protein was expressed in maxicells containing H4. Subclones of H4 which contained only a portion of hemA did not induce hemolysis on blood agar or promote expression of the recombinant protein in maxicells. Reverse transcriptase-mediated PCR analysis of total RNA isolated from excysted sporozoites and the intestines of infected adult mice with severe combined immunodeficiency demonstrated that hemA is actively transcribed during the cryptosporidial life cycle.

Frequency of unrecognized Bordetella pertussis infections in adults.

To investigate the frequency of unrecognized Bordetella pertussis infections in adults, we performed IgA and IgG ELISA antibody studies with four B. pertussis antigens--i.e., lymphocytosis-promoting factor, filamentous hemagglutinin, pertactin, and fimbriae-2--in 51 health care workers from whom six consecutive yearly serum samples (from 1984 to 1989) were available. Overall, 90% of the subjects had a significant increase in antibody (IgA or IgG) to one or more antigens between 2 consecutive years during the 5-year study period; 55% of subjects had evidence of two infections, 17% had three infections, and 4% had four infections. Infections occurred in all study years, with the following rates: 1984-1985, 32%; 1985-1986, 24%; 1986-1987, 40%; 1987-1988, 29%; and 1988-1989, 43% (P = .12). Some antibody rises may have been due to responses to cross-reacting antigens (Bordetella parapertussis, nontypable Haemophilus influenzae), but overall these data suggest that B. pertussis infections in adults are common, endemic, and usually unrecognized.

Enteral human serum immunoglobulin treatment of cryptosporidiosis in mice with severe combined immunodeficiency.

The anti-cryptosporidial immunoglobulin G antibodies in two commercially available human serum immunoglobulin (HSIG) products were quantified and characterized. The mean level of Cryptosporidium parvum-specific immunoglobulin G in HSIG was eightfold higher than the antibody level found in the sera of three immunocompetent individuals convalescing from cryptosporidiosis. However, HSIG products displayed no reactivity to cryptosporidial antigens in immunoblot analyses, while convalescent-phase sera demonstrated characteristic banding patterns. When HSIG was given to newborn severe combined immunodeficiency (scid) mice before and shortly after experimental infection, a decreased intensity of infection was observed in the intestines of the mice compared with that of control mice. However, there was no difference in mortality or histopathologic findings in the intestines of HSIG-treated and control mice when treatment was not started until 22 days of age. These results indicate that HSIG may be beneficial when given prophylactically; however, HSIG cannot eradicate cryptosporidia from mucosal surfaces in an established infection.

Inability of interferon-gamma and aminoguanidine to alter Cryptosporidium parvum infection in mice with severe combined immunodeficiency.

Severe combined immunodeficiency (scid) mice have been useful in identifying specific host defense systems responsible for containing and eradicating Cryptosporidium parvum infection. Adult scid mice were given C. parvum oocysts and treated weekly with monoclonal antimurine interferon-gamma (anti-IFN-gamma). Anti-IFN-gamma-treated mice had more cryptosporidia seen in the intestines and had more severe morphologic changes associated with disease than control mice. To assess the mechanism of this effect, infected adult BALB/c and scid mice were treated with the nitric oxide synthase inhibitor, aminoguanidine. Infection in aminoguanidine-treated mice was not significantly different from that in control mice. Next, the effects of pharmacologic doses of IFN-gamma (10,000 IU) on the course of cryptosporidiosis in newborn scid mice were evaluated. IFN-gamma did not reverse the initial susceptibility of neonatal scid mice to cryptosporidiosis and continued treatment with IFN-gamma (10,000 IU weekly) did not alter survival. We conclude that IFN-gamma does not exert its anticryptosporidial effect by stimulation of nitric oxide production. Deficient IFN-gamma production by neonatal lymphocytes does not appear to be responsible for the increased severity of infection observed in neonatal animals. Also, IFN-gamma may not be useful in treating immunocompromised patients with cryptosporidiosis.

Seroprevalence of cryptosporidial antibodies during infancy, childhood, and adolescence.

Cryptosporidium parvum causes mild to moderately severe diarrhea in immunocompetent individuals. Cryptosporidial antibodies in the sera of 803 children seen at Children's Hospital of Oklahoma were measured by means of an ELISA. Thirteen percent of children younger than 5 years of age were seropositive for antibodies to C. parvum. The seropositivity rate for children who attended day-care facilities was higher than that for those who did not. In addition, children in this age group with a history of recent diarrhea were seropositive at a higher rate than were children without diarrhea. Thirty-eight percent of children (5-13 years of age) and 58% of adolescents (14-21 years of age) were seropositive for antibodies to C. parvum. Blacks and Native Americans in these age groups had higher seropositivity rates than did White non-Hispanics. There were no differences in seropositivity rates between sexes or between residents of the largest urban counties in Oklahoma and residents of the more rural counties. Exposure to C. parvum during childhood is common in Oklahoma. Socioeconomic factors may play a role in early exposure to this protozoal pathogen.

Rhodococcus equi infections of humans. 12 cases and a review of the literature.

Increased recognition of Rhodococcus equi as a human pathogen has occurred since 1983, when the first review article summarized the world's literature of 12 cases. In this article, we present 12 cases from the University of Oklahoma Health Sciences Center and review 60 from the literature. Most cases occur in immunocompromised hosts and present as chronic cavitary pneumonias. Associated extrapulmonary disease is seen at diagnosis in 7% of patients with pneumonia, and relapse occurs at extrapulmonary sites in 13%, often without reappearance of pulmonary disease. Relapse may follow a course of antimicrobial therapy that is too brief, but can also occur during treatment. Infections also occur in the gastrointestinal tract, causing enteritis and regional adenitis with abscesses. Contaminated wounds may become infected. Isolated bacteremias may be a manifestation of latent infection recurring during a period of immune suppression. A common feature of human R. equi infection is delay in diagnosis. The insidious course of disease contributes to delay, as does failure to identify the organism. R. equi is easily cultured on nonselective media but commonly mistaken for a diphtheroid or occasionally for a mycobacterium based on acid-fast appearance. Form and duration of treatment are closely related to host immune status. Immunocompromised patients require prolonged or indefinite therapy with multiple antibiotics. Infections in immunocompetent hosts are easily treated with short courses of single agents. Infections related to contaminated wounds are treated primarily by irrigation and debridement. Infections in immunocompromised hosts are increasing in frequency largely due the AIDS epidemic. Infections in immunocompetent hosts, reported rarely before this series, may be underdiagnosed, perhaps because R. equi resembles common commensals and has limited virulence in this population. This report demonstrates that R. equi infections, including community-acquired pneumonias, occur in immunocompetent hosts.

Effect of abrogation of natural killer cell activity on the course of candidiasis induced by intraperitoneal administration and gastrointestinal candidiasis in mice with severe combined immunodeficiency.

Candida albicans CFU per gram of tissue recovered from livers, spleens, and kidneys of 12 severe combined immunodeficiency (scid) and 12 BALB/c mice 5 days after intraperitoneal (i.p.) administration of 10(7) C. albicans cells were not significantly different. Nine scid mice given normal rabbit serum (NRS) as a control and eight scid mice given anti-asialo-GM1 (alpha-ASGM1) had C. albicans CFU per gram recovered from livers and spleens 1 week after i.p. administration of C. albicans that were not significantly different, despite virtual elimination of natural killer (NK) cell activity in mice treated with alpha-ASGM1. At 2 weeks after i.p. administration, despite significantly increased NK cell activity in eight infected NRS-treated scid mice and virtual elimination of NK cell activity by alpha-ASGM1 treatment of eight scid mice, C. albicans CFU per gram recovered from livers and kidneys were not significantly different. At 2 weeks after intragastric administration of 2 x 10(6) C. albicans cells, eight NRS- and eight alpha-ASGM1-treated scid mice had identical proportions colonized with C. albicans and similar C. albicans CFU per gram recovered from feces. There was no evidence of hematogenous dissemination in either group. Similar results were seen 1 week after intragastric administration of 10(7) C. albicans cells. We conclude that NK cell activity is increased by i.p. administration of C. albicans in scid mice, but nontheless, abrogation of NK cell activity is not associated with enhanced susceptibility to candidiasis induced by i.p. administration and also is not associated with enhanced susceptibility to gastrointestinal colonization or hematogenous dissemination after intragastric administration of C. albicans.

Cryptosporidium parvum infection after abrogation of natural killer cell activity in normal and severe combined immunodeficiency mice.

The role of natural killer (NK) cell activity in adult mice with severe combined immunodeficiency (scid mice) infected with Cryptosporidium parvum oocytes was evaluated. Adult BALB/c and scid mice were inoculated intragastrically with 10(6) C. parvum oocysts after the administration of anti-asialo-GM1 or control normal rabbit serum. Groups of animals were evaluated for splenic NK cell activity and examined histopathologically at 2, 4, and 6 wk postinfection. Virtual elimination of splenic NK cell activity by anti-asialo-GM1 treatment was demonstrated. Nonetheless, no differences in the occurrence of illness, death, or histopathologic evidence of infection were observed between anti-asialo-GM1-treated and control-treated BALB/c or scid mice. We conclude that NK cell activity, at least as measured in the spleen, does not play a significant role in murine host defense of cryptosporidial infection, even in the absence of functional B and T cells.

Septicemia and meningitis caused by Helicobacter cinaedi in a neonate.

Helicobacter cinaedi has been most frequently isolated from rectal swabs of homosexual men with proctocolitis. The microorganism is a normal intestinal inhabitant of hamsters. We report a case of septicemia and meningitis by H. cinaedi in a neonate whose mother cared for pet hamsters during the first two trimesters of her pregnancy. The isolate was detected after 3 days of incubation in a Bact/Alert pediatric blood culture vial and an enrichment broth culture of the cerebrospinal fluid. H. cinaedi should be added to the list of unusual fastidious organisms that cause sepsis and meningitis in the newborn.

Bovine humoral immune response to Cryptosporidium parvum.

Cryptosporidiosis is a diarrheal disease predominantly affecting cattle and humans. Sera from experimentally infected calves and calves of various ages with no histories of exposure were evaluated for immunoglobulin G to Cryptosporidium parvum. An age-associated increase in immunoglobulin G was present in experimental calves and in calves with no histories of infection from 1 to 3, but not > 3, months of age.

Severe mycoplasma pneumonia in young children with Down syndrome.

Three young children with Down syndrome developed fever, cough, wheezing, irritability, and tachypnea. They had bilateral infiltrates on their chest radiographs and developed respiratory distress, which required their hospitalization. Laboratory studies suggested that the children had mycoplasma pneumonia. These children may have experienced severe mycoplasma infections early in life because of their Down syndrome-associated immune abnormalities. When young children with Down syndrome develop pneumonia, physicians should consider Mycoplasma pneumoniae as the possible etiologic agent.

Relapsing pneumococcal bacteremia in immunocompromised patients.

Relapse of Streptococcus pneumoniae bacteremia after appropriate therapy is thought to be rare, even in immunocompromised patients. We describe three immunodeficient patients who experienced repeated episodes of pneumococcal bacteremia within 8 weeks after receiving appropriate therapy. Serotyping and DNA fingerprinting of respective isolates strongly suggested that each patient's bacteremic relapse was caused by the same pneumococcal strain. Relapsing and recurrent infections with an identical pneumococcal strain, especially in immunodeficient individuals, may be more common than is generally appreciated.