Detection of dengue infection in patients investigated for leptospirosis in Barbados.
(41/1654)
The annual incidence of leptospirosis in Barbados is approximately 13 severe cases/100,000. The peak incidence occurs in October to December of each year, coinciding with the months of heaviest rainfall. During the second half of 1995, an epidemic of dengue type 1 infection produced almost 1,000 laboratory-confirmed cases. During the same period, leptospirosis mortality was twice the average, suggesting that some cases of leptospirosis were being misdiagnosed and treated inappropriately. Sera from patients investigated for dengue or leptospirosis were analyzed retrospectively to determine the extent of misdiagnosis. During 1995 and 1996, 31 of 139 and 29 of 93 patients, respectively, were confirmed as having leptospirosis. Sera from the remaining leptospirosis-negative patients were tested for IgM antibodies to dengue virus. During 1995 and 1996, 48 of 108 patients and 21 of 64 patients, respectively, were found to have dengue. In 1997, sera from all patients investigated for leptospirosis were also tested prospectively for IgM antibodies to dengue: 38 of 92 leptospirosis-negative patients (41%) were dengue IgM-positive, while 2 of 25 leptospirosis cases also had serologic evidence suggesting acute dengue infection. A second large outbreak of dengue caused by serotype 2 occurred in 1997. During the 1995 and 1997 dengue epidemics in Barbados, dengue cases outnumbered leptospirosis cases investigated in the leptospirosis diagnostic protocol. During 1997, patients investigated but negative for dengue were also tested for anti-leptospiral IgM: 7.3% (19 of 262) were IgM-positive. Substantial misdiagnosis of both dengue and leptospirosis can occur and greater public awareness and clinical suspicion of the similar presentations of these two diseases are necessary. (+info)
Effects of adjuvants on the immune response of staphylococcal alpha toxin and capsular polysaccharide (CPS) in rabbit.
(42/1654)
This study was performed to isolate a vaccine strain of S. aureus from clinical or subclinical mastitis and to choose the most optimal adjuvant for immune response of alpha toxin and capsular polysaccharide (CPS) of field strain. Of thirty strains of S. aureus isolated from milk of clinical or subclinical mastitis, V112 strain isolated from milk of gangrenous mastitis was used in this vaccine. Twenty one of rabbits were allocated into 5 groups based on adjuvants and immunized twice every 2 weeks for 8 weeks. This vaccine was composed of alpha toxin (10 hemolytic units) and formalinized whole cells (1 x 10(11) cells/ml. Five rabbits received PBS solution as a control group. The highest antibody titers against alpha toxin and CPS were observed in dextran sulfate- and aluminium hydroxide-adjuvant group at 8 weeks after immunization, respectively. These results of the study showed that one adjuvant could not induce strong and long-term immune response of alpha toxin and CPS antigens. Therefore, the use of combined adjuvants in subunit vaccine may be useful and feasible. (+info)
Salmonella typhi VI antigen co-agglutination test for the rapid diagnosis of typhoid fever.
(43/1654)
A slide Co-agglutination test for the detection of Salmonella typhi Vi antigen in blood was evaluated for its efficiency in rapid diagnosis of Typhoid fever. The results were compared with conventional methods like Blood culture and Widal test. The test showed a sensitivity of 86.67% and specificity of 88.83% when compared with blood culture positivity or Widal titre above 160. This is a useful rapid diagnostic test for the early diagnosis of Typhoid fever. (+info)
Assessment of the long-term shedding pattern of Salmonella serovar choleraesuis following experimental infection of neonatal piglets.
(44/1654)
In the United States, swine salmonellosis is most often attributed to infections by Salmonella serovar choleraesuis. As a host-adapted pathogen rarely found in nonswine sources, S. choleraesuis is thought to be spread primarily via horizontal transmission, with carrier animals playing an important role. Little has been reported regarding infection of neonatal piglets, particularly regarding their potential to become carriers. Evidence reported herein demonstrates that piglets experimentally infected by S. choleraesuis at 2 days of age were capable of shedding the pathogen for up to 85 days postinfection, at which time the study was concluded. This study also presents findings supporting the use of GN-Hajna as a preenrichment medium for the isolation of S. choleraesuis. (+info)
Rapid serotyping of groups A, B, and C meningococci by rocket-line immunoelectrophoresis and co-agglutination.
(45/1654)
Rocket-line immunoelectrophoresis (R-LIE) with antigen containing intermediate gel, and co-agglutination utilising protein A-containing staphylococci coated with specific antibodies, were adapted for serotyping the prototypes of group B meningococci. Both were found to have the same specificity as agar gel double diffusion (AGDD) but they were more sensitive and more rapid than AGDD. R-LIE required, like AGDD, the extraction of relatively large quantities of bacteria, while the co-agglutination method, performed as a slide agglutination tests with results within a few minutes and no need of special equipment, required only a small amount of heated whole meningococcal cells. Meningococcal strains of serogroups B, C, and A from patients with carriers were serotyped and the results with all three methods were in agreement. (+info)
emm and sof gene sequence variation in relation to serological typing of opacity-factor-positive group A streptococci.
(46/1654)
Approximately 40-60% of group A streptococcal (GAS) isolates are capable of opacifying sera, due to the expression of the sof (serum opacity factor) gene. The emm (M protein gene) and sof 5' sequences were obtained from a diverse set of GAS reference strains and clinical isolates, and correlated with M serotyping and anti-opacity-factor testing results. Attempts to amplify sof from strains with M serotypes or emm types historically associated with the opacity-factor-negative phenotype were negative, except for emm12 strains, which were found to contain a highly conserved sof sequence. There was a strong correlation of certain M serotypes with specific emm sequences regardless of strain background, and likewise a strong association of specific anti-opacity-factor (AOF) types to sof gene sequence types. In several examples, M type identity, or partial identity shared between strains with differing emm types, was correlated with short, highly conserved 5' emm sequences likely to encode M-type-specific epitopes. Additionally, each of three pairs of historically distinct M type reference strains found to share the same 5' emm sequence, were also found to share M serotype specificity. Based upon sof sequence comparisons between strains of the same and of differing AOF types, an approximately 450 residue domain was determined likely to contain key epitopes required for AOF type specificity. Analysis of two Sof sequences that were not highly homologous, yet shared a common AOF type, further implicated a 107 aa portion of this 450-residue domain in putatively containing AOF-specific epitopes. Taken together, the serological data suggest that AOF-specific epitopes for all Sof proteins may reside within a region corresponding to this 107-residue sequence. The presence of specific, hypervariable emm/sof pairs within multiple isolates appears likely to be a reliable indicator of their overall genetic relatedness, and to be very useful for accurate subtyping of GAS isolates by an approach that has relevance to decades of past M-type-based epidemiological data. (+info)
Plasmodium falciparum-infected erythrocytes: agglutination by diverse Kenyan plasma is associated with severe disease and young host age.
(47/1654)
The variant surface antigens (VSAs) of Plasmodium falciparum-infected red blood cells are potentially important targets of naturally acquired immunity to malaria. Natural infections induce agglutinating antibodies specific to the VSA variants expressed by the infecting parasites. Previously, when different parasite isolates were tested against a panel of heterologous plasma from Kenyan children, the proportion of plasma that agglutinated the parasites (the agglutination frequency [AF]) was highly variable among isolates, suggesting the existence of rare and prevalent variants. Here, the AF of 115 isolates from Kenyan children were compared. The results show that the AF of isolates causing severe malaria were significantly higher than those of isolates causing mild malaria; and AF decreased significantly with the increasing age of the infected child. We propose that parasites causing severe disease tend to express a subset of VSA variants that are preferentially associated with infections of children with low immunity. (+info)
Reactivity to p52 and CM2 recombinant proteins in primary human cytomegalovirus infection with a microparticle agglutination assay.
(48/1654)
We evaluated the reactivities of sera against p52 and CM2 recombinant antigens of human cytomegalovirus (HCMV), coated on microparticles, for the differentiation of primary HCMV infection from an established infection. Two different test formats of the CMV Multiplex Copalis assay were evaluated. The 214 serum samples tested were immunoglobulin M (IgM) positive or equivocal by our reference assay. Reactivities against p52 and CM2 antigens were tested for sera from 37 patients with a well-documented seroconversion within the preceding 3 months (119 serum specimens), 31 patients known to have had a seroconversion at least 8 months earlier (31 serum specimens), and 57 patients without a documented seroconversion (64 serum specimens). The assay had a sensitivity for the detection of a primary infection of 70 or 86% by the first test format and a sensitivity of 88 or 94% by the second test format, according to the criteria used to indicate a primary infection by this test. A good correlation of the results of the assay with our in-house avidity index was found. The specificity of the assay warrants further evaluation. With IgM-positive sera, the assay was not sufficiently specific to make a distinction between a primary infection and an established infection. (+info)