Evaluation of a commercial latex agglutination assay for serological diagnosis of leptospirosis

Leptospirosis is a febrile zoonosis of worldwide distribution. A latex agglutination assay was evaluated in two studies, the first using a panel of well-characterized sera from patients with leptospirosis and from patients with other disease states and the second, a prospective hospital-based study, evaluating sera from 186 consecutive patients admitted to hospital with acute febrile illness. The confirmed leptospirosis serum panel included paired acute- and convalescent-phase specimens from 40 cases, of which 34 gave positive latex tests (case sensitivity, 85%; 95% confidence interval [95% CI], 70 to 94%). The other diseases represented in the panel of 112 specimens from nonleptospirosis patients included autoimmune diseases, brucellosis, dengue, melioidosis, malaria, syphilis, toxoplasmosis, viral hepatitis, and a number of other viral infections. The specificity of latex agglutination using this panel was 81% (95% CI, 73 to 87%). Among the patients with acute febrile illness, there were 25 cases of leptospirosis and 161 patients with other diagnoses. The sensitivity and specificity of latex agglutination in this group were 88% (95% CI, 72 to 97%) and 98% (95% CI, 95 to 100%), respectively. In this evaluation, the two distinct groups of specimens gave similar results for sensitivity, but specificity was different in each study. The sensitivity and specificity observed for the hospital study were similar to those obtained in evaluations of other rapid tests in the same population. The results of this study suggest that multiple evaluations of new diagnostic assays should be performed, because performance characteristics may vary in different populations.

Leptospirosis among patients presenting with dengue-like illness in Puerto Rico

Leptospirosis is difficult to distinguish from dengue fever without laboratory confirmation. Sporadic cases/clusters of leptospirosis occur in Puerto Rico, but surveillance is passive and laboratory confirmation is rare. We tested for leptospirosis using an IgM ELISA on sera testing negative for dengue virus IgM antibody and conducted a case-control study assessing risk factors for leptospirosis, comparing clinical/laboratory findings between leptospirosis (case-patients) and dengue patients (controls). Among 730 dengue-negative sera, 36 (5%) were positive for leptospirosis. We performed post mortem testing for leptospirosis on 12 available specimens from suspected dengue-related fatalities; 10 (83%) tested positive. Among these 10 fatal cases, pulmonary hemorrhage and renal failure were the most common causes of death. We enrolled 42 case-patients and 84 controls. Jaundice, elevated BUN, hyperbilirubinemia, anemia, and leukocytosis were associated with leptospirosis (p < .01 for all). Male sex, walking in puddles, rural habitation, and owning horses were independently associated with leptospirosis. Epidemiological, clinical, and laboratory criteria may help distinguish leptospirosis from dengue and identify patients who would benefit from early antibiotic treatment.

Leptospirosis mimicking acute cholecystitis among athletes participating in a triathlon

Leptospirosis, a disease acquired by exposure to contaminated water, is characterized by fever accompanied by various symptoms, including abdominal pain. An acute febrile illness occurred in athletes who participated in an Illinois triathlon in which the swimming event took place in a freshwater lake. Of 876 athletes, 120 sought medical care and 22 were hospitalized. Two of the athletes had their gallbladders removed because of abdominal pain and clinical suspicion of acute cholecystitis. We applied an immunohistochemical test for leptospirosis to these gallbladders and demonstrated bacterial antigens staining (granular and filamentous patterns) around blood vessels of the serosa and muscle layer. Rare intact bacteria were seen in 1 case. These results show that leptospirosis can mimic the clinical symptoms of acute cholecystitis. If a cholecystectomy is performed in febrile patients with suspicious environmental or animal exposure, pathologic studies for leptospirosis on formalin-fixed, paraffin-embedded tissues may be of great value.

Asymptomatic infection and risk factors for leptospirosis in Nicaragua

As part of an investigation of a 1995 outbreak of leptospirosis in Nicaragua, a cross-sectional serologic survey was conducted in the town of El Sauce. Of 566 persons, 85 (15%) were positive for IgM anti-Leptospira antibodies, indicating recent leptospirosis infection. Asymptomatic leptospirosis infection was common, with only 25 (29.4%) of the 85 seropositive inhabitants reporting a febrile illness in the 2 months before the survey. Multivariable analysis revealed that having an indoor water source remained independently protective against leptospirosis. Gathering wood was independently associated with infection. These findings suggest that asymptomatic infection with Leptospira is common in endemic areas of Leptospira transmission. Improvement in water sanitation and behavioral modifications to reduce environmental exposure may reduce the risk of leptospirosis in endemic regions.

Analysis of the 1998 outbreak of leptospirosis in Missouri in humans exposed to infected swine

OBJECTIVE

To determine the extent of leptospirosis in persons exposed to infected swine, confirm the source of disease, define risk factors for infection, and identify means for preventing additional infections during an outbreak in Missouri in 1998.

DESIGN

Cross-sectional study.

SAMPLE POPULATION

240 people and 1,700 pigs.

PROCEDURE

An epidemiologic investigation was conducted of people exposed to infected pigs from the University of Missouri-Columbia swine herd. The investigation included review of health of the pigs, a cross-sectional study of the people handling the pigs, serologic testing of human and porcine sera, and risk-factor analysis for leptospirosis within the human population.

RESULTS

Serologic testing of samples collected at the time of the investigation indicated that 59% of the pigs had titers to leptospires, denoting exposure. Of the 240 people in the exposed study population, 163 (68%) were interviewed, and of these, 110 (67%) submitted a blood sample. Nine (8%) cases of leptospirosis were confirmed by serologic testing. Risk factors associated with leptospirosis included smoking (odds ratio [OR], 14.4; 95% confidence interval [CI], 1.39 to 137.74) and drinking beverages (OR, 5.1; 95% CI, 1.04 to 24.30) while working with infected pigs. Washing hands after work was protective (OR, 0.2; 95% CI, 0.03 to 0.81).

CONCLUSIONS AND CLINICAL RELEVANCE

Leptospirosis is a risk for swine producers and slaughterhouse workers, and may be prevented through appropriate hygiene, sanitation, and animal husbandry. It is essential to educate people working with animals or animal tissues about measures for reducing the risk of exposure to zoonotic pathogens.

Evaluation of the indirect hemagglutination assay for diagnosis of acute leptospirosis in Hawaii

Timely diagnosis of leptospirosis is important to ensure a favorable clinical outcome. The definitive serologic assay, the microscopic agglutination test (MAT), requires paired sera and is not useful for guiding early clinical management. The only screening test approved for use in the United States, the indirect hemagglutination assay (IHA), has not undergone extensive field evaluation. To assess the performance of the leptospirosis IHA in Hawaii, serum from patients evaluated for leptospirosis between 1992 and 1997 were tested with the IHA at the Hawaii State Laboratories Division and with the MAT at the Centers for Disease Control and Prevention. Leptospirosis was considered confirmed by a fourfold rise in MAT titer and/or a positive culture. A total of 92 (41%) of 226 specimens from 114 persons with confirmed leptospirosis were found positive by IHA. Only 18 (15%) of 119 specimens obtained within 14 days of onset were IHA positive, compared to 74 (69%) of 107 specimens collected more than 14 days after onset (P <0.001). Repeat testing ultimately resulted in 78 (68%) of the confirmed cases having at least one specimen found positive by IHA. Thirteen different presumptive infecting serogroups were identified among 251 specimens with an MAT titer of >/=200 and obtained from persons with confirmed or probable leptospirosis. Fifty (68%) of 73 specimens with Icterohaemorrhagiae as the presumptive infecting serogroup were found positive by IHA, compared to 44 (47%) of 93 specimens with Australis as the presumptive infecting serogroup (P, 0.01). The IHA test was positive for 3 (1%) of 236 specimens from 154 persons without leptospirosis. The sensitivity of the leptospirosis IHA in Hawaii was substantially below figures reported previously, particularly early in the course of illness, limiting its usefulness for diagnosing acute infection. Since the presumptive infecting serogroup affected IHA results and the prevalence of serovars varies with geography, the performance of the IHA should be assessed locally. More sensitive leptospirosis screening tests are needed in Hawaii.

International multicenter evaluation of the clinical utility of a dipstick assay for detection of Leptospira-specific immunoglobulin M antibodies in human serum specimens

We performed a multicenter evaluation of a robust and easily performed dipstick assay for the serodiagnosis of human leptospirosis. The assay is aimed at the detection of Leptospira-specific immunoglobulin M (IgM) antibodies. The study involved 2,665 serum samples collected from 2,057 patients with suspected leptospirosis in 12 countries on five continents with different levels of endemicity and different surveillance systems. The patients were grouped as laboratory-confirmed leptospirosis case patients and noncase patients based on the results of culturing and the microscopic agglutination test. Paired samples from 27.7% of the subjects were tested. Of the 485 case patients, 87.4% had a positive dipstick result for one or more samples. Of the 1,513 noncase patients, only 7.2% had a positive result. Whereas most (88.4%) of the positive samples from the case patients showed moderate to strong (2+ to 4+) staining in the dipstick assay, most (68.1%) of the positive samples from the noncase patients showed weak (1+) staining. The sensitivity of the dipstick assay increased from 60.1% for acute-phase serum samples to 87.4% for convalescent-phase samples. The specificities for these two groups of samples were 94.1 and 92.7%, respectively. The dipstick assay detected a broad variety of serogroups. The results of the dipstick assay were concordant (observed agreement, 93.2%; kappa value, 0.76) with the results of an enzyme-linked immunosorbent assay for the detection of specific IgM antibodies, a test which is often used in the laboratory diagnosis of current or recent leptospirosis. This study demonstrated that this easily performed dipstick assay is a valuable and useful test for the quick screening for leptospirosis; has a wide applicability in different countries with different degrees of endemicity; can be used at all levels of the health care system, including the field; and will be useful for detecting and monitoring outbreaks of leptospirosis.

Increase of leptospirosis in dengue-negative patients after a hurricane in Puerto Rico in 1996 [correction of 1966]

Leptospirosis has rarely been reported in Puerto Rico, although in the period from 1948 to 1952, 208 cases of leptospirosis and an island-wide seroprevalence of antibody to Leptospira of 14% were documented. In Puerto Rico in October 1996, following rainfall and a period of flooding generated by Hurricane Hortense, serum specimens of 4 patients with suspected dengue fever that were negative for dengue tested positive for Leptospira-specific IgM antibodies in a dipstick assay. Subsequently, we used an island-wide dengue laboratory-based surveillance system to determine the increase in leptospirosis after hurricane-generated floods. All anti-dengue IgM-negative patients (n = 142) with disease onset from August 8 to October 6, 1996 from prehurricane and posthurricane groups were investigated for leptospirosis. Laboratory-confirmed leptospirosis cases were defined as microscopic agglutination test titers > or = 1 :400 to 1 or more serovars, or positive immunohistochemistry in autopsy tissues. Four (6%) of 72 prehurricane and 17 (24%) of 70 posthurricane patients had laboratory-confirmed cases of leptospirosis (relative risk [RR] = 4.4, 95% confidence interval [CI] = 1.6-12.4). The mean age of case-patients was 34 years (range = 13-64). Eighteen (86%) of 21 confirmed case-patients were males, including one patient who died (31 years old). Patients were located in 18 (38%) of 48 municipalities that submitted serum samples. Clinical features significantly associated with leptospirosis were eye pain (RR = 1.5, 95% CI = 1.3-1.9), joint pain (RR = 1.4, 95% CI = 1.1-1.6), diarrhea (RR = 1.7, 95% CI = 1.2-2.5), and jaundice (RR = 3.3, 95% CI = 1.5-7.2). This study demonstrates the utility of a dengue laboratory-based surveillance system for the detection of an increase of leptospirosis, which most likely would have gone unrecognized. Leptospirosis is treatable with antibacterial agents; knowledge of this diagnosis may significantly reduce morbidity and mortality.

Epidemic leptospirosis associated with pulmonary hemorrhage-Nicaragua, 1995

In October 1995, epidemic "hemorrhagic fever," without jaundice or renal manifestations, was reported in rural Nicaragua following heavy flooding; 2259 residents were evaluated for nonmalarial febrile illnesses (cumulative incidence, 6.1%) and 15 (0.7%) died with pulmonary hemorrhage. A case-control study found that case-patients were more likely than controls to have ever walked in creeks (matched odds ratio [MOR], 15.0; 95% confidence interval [CI], 1.7-132.3), have household rodents (MOR, 10.4; 95% CI, 1.1-97.1), or own dogs with titers >/=400 to Leptospira species (MOR, 23.4; 95% CI, 3.6-infinity). Twenty-six of 51 case-patients had serologic or postmortem evidence of acute leptospirosis. Leptospira species were isolated from case-patients and potential animal reservoirs. This leptospirosis epidemic likely resulted from exposure to flood waters contaminated by urine from infected animals, particularly dogs. Leptospirosis should be included in the differential diagnosis for nonmalarial febrile illness, particularly during periods of flooding or when pulmonary hemorrhage occurs.

Comparison of two rapid latex agglutination tests for detection of cryptococcal capsular polysaccharide

The Murex Cryptococcus Test was compared with the Cryptococcal Antigen Latex Agglutination System (CALAS) for detecting cryptococcal polysaccharide in 173 cerebrospinal fluid (CSF) specimens and 117 serum samples with 99% and 97% concordance, respectively. Eighteen CSF samples and 17 serum samples were positive in both assays, and 249 were negative. The sensitivity and specificity of the Murex relative to the CALAS were 90% and 100%, respectively, for CSF, and 81% and 100%, respectively, for serum. Six discrepancies were arbitrated by retesting, using a third analytic method, review of other laboratory and clinical data, or both. The reaction in 1 CSF specimen was considered false positive by the CALAS, and the reactions in 2 serum samples were false negatives by the Murex. For 3 patients with previous cryptococcal meningitis but no active disease, only the CALAS detected antigen, suggesting that the Murex has less analytic sensitivity in this context. Titer differences dictate that direct comparisons between the 2 tests are not feasible. There were no false-positive reactions in limited testing with either method using specimens from patients with concurrent noncryptococcal infections or in rheumatoid factor-positive serum samples. Infections caused by Cryptococcus neoformans serotypes A or AD were detected equally by both assays. Based on our study, we have elected to continue to use the CALAS for routine testing for cryptococcal antigen.

Immunochemical analysis of the H and M glycoproteins from Histoplasma capsulatum

The H and M antigens of Histoplasma capsulatum are glycoproteins, and both possess epitopes found on the C antigen, a cross-reactive galactomannan shared by the major genera of systemic dimorphic fungi. We modified the H and M glycoproteins by chemical and enzymatic digestion to determine the relative contributions of the carbohydrate and protein moieties to the immunological reactivities and the apparent molecular weights of these antigens. Endoglycosidases with known action patterns were used to determine the nature of the glycopeptide bonds in the H and M antigens. The effects of these treatments were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, lectin binding, and enzyme-linked immunoelectrotransfer blots probed with polyclonal and monoclonal antibodies (MAbs). Oxidation with 100 mM periodate destroyed the common fungal epitope recognized by MAb CA1-CB4 and nearly all of the concanavalin A-binding sites on both the H and M antigens; it also caused the molecular mass of the M antigen to shift from 94 to 88 kDa. Treatment of samples with O-glycanase had little, if any, effect on the H and M glycoproteins. On the other hand, treatments with endo-beta-N-acetylglucosaminidase H, and particularly peptide N-glycoproteins F (PNGase F), produced pronounced shifts in the M(r) but did not completely eliminate concanavalin A- or MAb CA1-CB4-binding sites. PNGase F treatment caused the molecular mass of the H antigen to shift from 116 to 94 kDa and that of the M antigen to shift from 94 to 74 kDa. The susceptibilities of the H and M glycoproteins to endo-N-acetyl-beta-D-glucosaminidases suggest that their glycosidic moieties are N linked.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of histoplasmin M antigen chemical and enzymatic deglycosylation on cross-reactivity in the enzyme-linked immunoelectrotransfer blot method

The enzyme-linked immunoelectrotransfer blot (EITB) method was evaluated as a suitable method for detecting antibodies against M antigen of Histoplasma capsulatum by use of both glycosylated and deglycosylated M protein of histoplasmin (HMIN). Sera from patients with histoplasmosis, paracoccidioidomycosis, blastomycosis, coccidioidomycosis, and aspergillosis were tested by the EITB with glycosylated M protein of HMIN. This assay demonstrated 100% sensitivity with histoplasmosis serum samples, all of which reacted with the 94-kDa glycoprotein (M antigen). Although the EITB is highly sensitive, it is not specific for histoplasmosis when glycosylated M protein is used as an antigen. A total of 81% of paracoccidioidomycosis, 25% of blastomycosis, 33% of coccidioidomycosis, 73% of aspergillosis, and 16% of tuberculosis serum samples cross-reacted with M protein of HMIN and yielded patterns indistinguishable from those obtained with histoplasmosis serum samples. The EITB reactions with both untreated M antigen and M antigen altered by periodate oxidation or by deglycosylation with endoglycosidases were compared. Cross-reactions with heterologous sera in the EITB could be attributed to periodate-sensitive carbohydrate epitopes, as reflected by the increase in the test specificity from 46.1 to 91.2% after periodate treatment of M protein. The EITB for the detection of antibodies to M antigen is a potential diagnostic test for histoplasmosis, provided that periodate-treated M protein is used as an antigen.

Multilocus enzyme typing of Cryptococcus neoformans

Multilocus enzyme electrophoresis was adapted for subtyping Cryptococcus neoformans. The two cryptococcal varieties were clearly distinguishable. Isolates of the C. neoformans var. neoformans were sorted according to serotype and were sorted into four to five subtypes within each serotype. Nearly no two isolates of the C. neoformans var. gattii displayed the same enzyme electrophoretic type. This method may be a useful adjunct to current methods for classification and epidemiologic studies of cryptococci.

Purification and characterization of the extracellular aspartyl proteinase of Candida albicans: removal of extraneous proteins and cell wall mannoprotein and evidence for lack of glycosylation

Aspartyl proteinase (AP) is an extracellular enzyme of Candida albicans implicated as a pathogenic factor. Previous reports on the purification and characterization of AP suggested that a single DEAE-Sephadex chromatographic step was sufficient for the removal of extraneous proteins and that the final product was glycosylated. We purified AP using a chromatographic series consisting of DEAE-Sephadex A25, Sephadex G75 and rechromatography on DEAE-Sephadex A25. Use of DEAE-Sephadex alone did not remove extraneous proteins and removed little contaminating mannoprotein (MP). The addition of a Sephadex G75 column to the purification scheme removed the majority of contaminating MP and proteins. The final DEAE-Sephadex A25 chromatographic step resulted in (a) removal of detectable extraneous proteins, (b) removal of immunologically detectable MP by dot blot and Western blot enzyme immunoassay, (c) loss of periodic acid-silver stain positivity, and (d) a high AP yield (1295 U l-1) and specific activity (1749 U mg-1). We conclude that a single DEAE-Sephadex A25 purification step is insufficient to remove extraneous proteins and MP, which could interfere with the production of AP-specific antibodies and the dissection of moieties responsible for immune reactivity. Reports of periodic acid-Schiff or anthrone positivity of AP preparations may reflect the presence of extraneous MP, which can be removed by the chromatographic series we describe.

Heterogeneity of the purified extracellular aspartyl proteinase from Candida albicans: characterization with monoclonal antibodies and N-terminal amino acid sequence analysis

Three dominant proteins (41, 48, and 49 kDa) were detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in purified preparations of the extracellular aspartyl proteinase (AP) of Candida albicans. All three proteins bound to the specific carboxyl proteinase ligand, pepstatin A, and were associated with maximum AP activity. The N-terminal amino acid sequence for the 48- and 49-kDa proteins matched that reported by others for AP, whereas the sequence for the 41-kDa protein was unique and was not homologous to any known protein. Time course studies demonstrated the simultaneous presence of all three proteins, supporting evidence that the 41- and 48-kDa proteins were not breakdown products of AP. Previous studies did not detect carbohydrate in SDS-polyacrylamide gels of purified AP preparations stained with periodic acid and silver, making glycosylation an unlikely explanation for the observed differences in the molecular masses of the proteins. Some monoclonal antibodies directed against the 49-kDa protein reacted with the 41- and 48-kDa proteins, indicating cross-reactive epitopes. Other monoclonal antibodies, however, reacted only with the 49-kDa protein. We conclude that three pepstatin A-binding proteins occur in purified AP preparations: two have the same amino acid N terminus as that reported for AP, whereas the third has a unique sequence. All three proteins should be considered when undertaking studies to determine the role of AP in candidal pathogenesis or when preparing specific antibodies for antigen capture assays.

Atmospheric water vapor absorption at 1.3 microm

Absolute absorption cross sections for water vapor and water vapor/air mixtures were measured in a frequency range encompassing that of the chemically pumped atomic iodine laser. Measurements were made with a temperature-controlled multipass absorption cell and a high-resolution Fourier transform spectrometer. The measurements covered a broad range of water vapor and air pressures. Several techniques of data analysis were used, and the absorption cross section of 2 kPa of water vapor in an atmosphere of air was determined to be 1.1 +/- 0.2 x 10(-24) cm(2) . In this paper, an expression is derived which allows estimation of the absorption cross section for any pressure of water vapor and air.

Monoclonal antibodies against Candida tropicalis mannan: antigen detection by enzyme immunoassay and immunofluorescence

Three strains of mice were immunized with Candida tropicalis cell walls, and antibodies against mannan were detected by indirect enzyme immunoassay (EIA) in 3 of 9 BALB/c mice, 4 of 11 C57BL/6 mice, and 4 of 8 CFW mice. Responding mice produced immunoglobulin M (IgM), but IgG was not detected in their sera. Fusion of the high-responder BALB/c mouse with a plasmacytoma cell line resulted in 41 clones secreting antimannan monoclonal antibodies (MAbs). Four clones selected for propagation included one IgM and one IgG MAb that reacted with mannans of Candida albicans serotypes A and B and of C. tropicalis and two IgM MAbs specific for an epitope only in the mannans of C. albicans serotype A and C. tropicalis. One of the IgM MAbs, CB6, was an effective substitute for rabbit antibodies in the double-antibody sandwich EIA to detect antigenemia produced in rabbits infected with C. albicans A or C. tropicalis. It could function either as the peroxidase-conjugated indicator antibody or as the capture antibody. Two MAbs, CB6 (C. tropicalis and C. albicans A specific) and AC3 (C. tropicalis and C. albicans A and B specific), functioned in place of polyclonal antisera in the serotyping of C. albicans by immunofluorescence. There was 95.8% agreement in the results of serotyping using MAbs as reagents compared with rabbit antisera. Competitive inhibition in EIA between CB6 and monospecific antisera against C. albicans factors 1, 4, and 6 indicated that CB6 binds to an epitope which is probably factor 6. Serologic similarity between factor 4 and the binding site of MAb AC3 was also determined.

Monoclonal antibodies against the M-protein and carbohydrate antigens of histoplasmin characterized by the enzyme-linked immunoelectrotransfer blot method

Monoclonal antibodies (MAbs) of two different specificities were produced by immunizing mice with the semipurified M antigen of histoplasmin. One type, from clone CB4, was an immunoglobulin M that precipitated a polysaccharide present in histoplasmin and also formed immunoprecipitates with a cross-reactive polysaccharide present in extracts of Blastomyces dermatitidis and Coccidioides immitis. The second type of MAb, from clone EC2, was an immunoglobulin G that reacted in the enzyme-linked immunoelectrotransfer blot (EITB) assay with a doublet of proteins with an apparent molecular size of 70 to 75 kilodaltons. This molecule is proposed as the authentic M protein antigen that is recognized by M antibodies in sera from mice and rabbits immunized with Histoplasma capsulatum and from persons with histoplasmosis. The M factor also occurs in an abundant disulfide-bridged dimer which has a molecular size of 150 kilodaltons and is nonimmunoreactive under the conditions of sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

Absolute measurements of absorption at the iodine-laser frequency in atmospheric gases

The absorption cross sections at the chemical-iodine-laser frequency for methane and carbon dioxide in an atmosphere of dry air were determined with a photoacoustic cell to be (8 +/- 2) x 10(-24) and (5.4 +/- 0.4) x 10(-25) cm(2), respectively. A multipass absorption cell and a Fourier-transform spectrometer were used to obtain a cyclopropane absorption cross section of (3.47 +/- 0.02) x 10(-24) cm(2) at 14 076 cm(-1) for the photoacoustic-cell calibration.

Relative hydrophobicities of Actinomyces viscosus and Actinomyces naeslundii strains and their adsorption to saliva-treated hydroxyapatite

The present study examined 42 strains of Actinomyces spp. to determine whether adsorption to saliva-treated hydroxyapatite (SHA) of the selected strains of this prominent group of dental-plaque bacteria correlated with hydrophobicity. The relative hydrophobicity of the strains was determined by their adsorption to hydrophobic gels (i.e., phenyl-Sepharose) and their aggregation in ammonium sulfate. Within serogroups the relative hydrophobicity for the strains was similar. The relative adsorption of strains to SHA was also similar within the respective serogroups. Strains which were relatively hydrophobic, as judged by their binding to the hydrophobic gel and aggregation in low concentrations of ammonium sulfate, adsorbed well to SHA. Strains which adsorbed poorly to SHA were relatively hydrophilic since they did not bind well to the hydrophobic gel and were only aggregated in relatively high concentrations of ammonium sulfate. Tween 80, a nonionic detergent known to inhibit hydrophobic interactions, blocked binding of cells to the hydrophobic gel, suggesting that hydrophobic interactions had been inhibited. However, Tween 80 exhibited no influence on the adsorption of cells to SHA. Thus, although there was a strong statistical correlation between the relative hydrophobicity of a strain and its adsorption to SHA, the data were consistent with the view that other interactions, such as ionic bonds and interactions between complimentary macromolecules, are involved in adsorption of the Actinomyces strains to SHA.

Serotyping Cryptococcus neoformans by immunofluorescence

Four serotypes of Cryptococcus neoformans designated A, B, C, and D are currently recognized. Although an agglutination test is most often used to serotype C. neoformans in cultures, this test is not appropriate for typing the fungus in fixed tissues. A study to prepare fluorescent-antibody reagents for typing C. neoformans in cultures and to determine whether they can be used to type this fungus in fixed tissues was carried out. Antisera to one strain belonging to each of the four serotypes were prepared in rabbits by intravenous injection of whole Formalin-killed cryptococci. Each antiserum was labeled with fluorescein isothiocyanate and then adsorbed with cells of each of the heterologous serotypes. The adsorbed conjugates were then tested against six serotype A isolates and five isolates of each of the other three serotypes. Labeled serotype A or D antiserum adsorbed with either B or C cells stained the A and D, but not the B or C, isolates. Labeled serotype B antiserum adsorbed with A cells stained the B and C, but not the A or D, isolates. Labeled A antiserum absorbed with D cells differentiated A from D; labeled C antiserum absorbed with B cells differentiated C from B. Of the 21 test isolates, 17 could be serotyped in paraffin sections of tissues of experimentally infected mice.

One Mars Year: Viking Lander Imaging Observations

Throughout the complete Mars year during which they have been on the planet, the imaging systems aboard the two Viking landers have documented a variety of surface changes. Surface condensates, consisting of both solid H(2)O and CO(2), formed at the Viking 2 lander site during the winter. Additional observations suggest that surface erosion rates due to dust redistribution may be substantially less than those predicted on the basis of pre-Viking observations. The Viking 1 lander will continue to acquire and transmit a predetermined sequence of imaging and meteorology data as long as it is operative.