Micrometer- and Nanometer-Sized Polymeric Light-Emitting Diodes

A method for the fabrication of micrometer-and submicrometer-sized polymeric light-emitting diodes is presented. Such diodes have a variety of applications. Light sources of dimensions around 100 nanometers are required for subwavelength, near-field optical microscopy. Another possible application is patterning on the micrometer and nanometer scale. The diodes have been made in the form of a sandwich structure, with the conductive polymer poly(3,4-ethylene-dioxythiophene) polymerized in the pores of commercially available microfiltration membranes defining the hole-injecting contacts, poly[3-(4-octylphenyl)-2,2;-bithiophene] as the light-emitting layer, and a thin film of calcium-aluminum as the electron injector.

A comparison of four assays detecting oxidizing species. Correlated reactivity of Fe(III)-quin2, but not Fe(III)-EDTA, with hydrogen peroxide

Quin2, a fluorescent calcium probe, has a low affinity for calcium in comparison to its affinities for transition metal ions. Chelation of ferric ion with quin2 strongly enhanced the formation of oxidizing species in the presence of bolus H2O2 as detected with four assays, electron spin resonance with the spin-trap DMPO, the deoxyribose assay, the DMSO assay, and plasmid DNA strand breakage. In comparison, Fe(III)-EDTA reacted with bolus H2O2 only as detected with electron spin resonance and deoxyribose assay, but not as detected with the two latter assays. The addition of reductants, like ascorbate or superoxide generated by hypoxanthine/xanthine oxidase, to Fe(III)-EDTA in the presence of H2O2 produced plasmid DNA strand breakage and strong reactivity in both the DMSO and the deoxyribose assays. Our findings suggest that the main oxidizing species produced in Fenton-type reactions is hydroxyl radical. However, the reaction between Fe(III)-EDTA and bolus H2O2 appears to be exceptional and dominated by a nonhydroxyl radical species.

Immunoglobulin E and G responses to pertussis toxin after booster immunization in relation to atopy, local reactions and aluminium content of the vaccines

The role of aluminium for IgG and IgE responses to pertussis toxin (PT), as well as for side effects, was investigated in 49 children with known atopy status. Primary immunization had been given with an adsorbed monocomponent or an adsorbed two-component acellular pertussis vaccine. The children were then randomized to receive a booster immunization with either aluminium-adsorbed or non-adsorbed, whole cell, pertussis vaccine. Both vaccines induced good IgG responses with the adsorbed vaccine giving higher post-booster levels (p < 0.05). The adsorbed vaccine was, however, associated with more local side effects (p < 0.05) and tended to induce higher PT-IgE responses than the non-adsorbed vaccine. Furthermore, individuals who had received the two-component vaccine as primary immunization had higher PT-IgE responses after the booster, compared with individuals initially receiving the monocomponent vaccine (p = 0.041). No correlation between PT-IgE and PT-IgG levels was seen in any of the groups. Total serum IgE levels correlated to PT IgE levels, particularly in children with atopy (r = 0.950, p < 0.001). The addition of aluminium to the pertussis vaccine, was, thus, associated with a stronger IgG antibody response, but tended also to induce a stronger IgE antibody response. The correlation between total IgE and PT-IgE, which was most prominent in children with atopy, indicates that the role of immunization for the development of allergy merits further studies.

The role of IgA determination by ELISA in the early serodiagnosis of Mycoplasma pneumoniae infection, in relation to IgG and mu-capture IgM methods

Enzyme-linked immunosorbent assay (ELISA) for IgA, IgG and IgM was evaluated with sera from 50 adult patients with pneumonia, selected on the basis of a positive complement fixation (CF) test for diagnosis of Mycoplasma pneumoniae infection and with sera from 105 healthy blood donors. The ELISA antigen for IgG and IgA was a sonicated suspension of M. pneumoniae solubilised by deoxycholate. For the IgM assay, the same antigen was directly conjugated to alkaline phosphatase and used in a mu-capture format. ELISA gave positive results with high or rising titres for one or several antibody classes in 47 (94%) patients. In two of the three ELISA-negative cases, the diagnosis of M. pneumoniae infection indicated by the CF test seemed unlikely on clinical grounds. Specific IgA antibodies was developed more regularly and more rapidly than IgM. IgA titres also started to decrease earlier than IgM or the late-peaking IgG response. Thus, the determination of IgA antibodies was found to be valuable for the early diagnosis of M. pneumoniae infection. The study also demonstrated that the determination of all three antibody classes is necessary to obtain an optimal level of serodiagnosis.

Adverse reactions after diphtheria-tetanus booster in 10-year-old schoolchildren in relation to the type of vaccine given for the primary vaccination

This prospective open study investigated adverse reactions in 527 schoolchildren to a diphtheria-tetanus (DT) booster given within a national vaccination programme at 10 years of age. Evaluation was based on those whose immunization records showed that they had received either three doses of an adsorbed DT vaccine (n = 388) or a non-adsorbed DT-pertussis vaccine (DTP) (n = 69) for primary series vaccination. No differences in systemic reactions to the booster between the two groups were observed. Local reactions were significantly (p < 0.001) more common 1 day after vaccination in children who had received DT for primary series vaccination: redness, 73% compared with 23%; swelling, 56% versus 15%; and itching, 47% versus 21%. One and 2 weeks after the booster, itching was still more pronounced in the group who had received DT for primary series vaccination (p < 0.001 and 0.014, respectively). The study indicates that there was a real basis for the increase in spontaneous notifications of local side-effects to the school DT booster in Sweden. The most likely cause for the increase seems to be the aluminium adjuvant in the vaccine given for primary vaccination, a late and unexpected consequence of a change in the infant immunization programme.

The role of aluminium for adverse reactions and immunogenicity of diphtheria-tetanus booster vaccine

In a randomized, double-blind clinical trial, 235 schoolchildren aged 10 years received either a regular, aluminium-adsorbed diphtheria-tetanus vaccine or the same vaccine in fluid form, in order to investigate if local side effects could be diminished by exclusion of aluminium. System reactions were rare and local reactions frequent in both groups but larger local reactions were even more pronounced in the non-adsorbed vaccine group. Antibody responses to both vaccines were excellent and even slightly higher to the non-adsorbed diphtheria-tetanus vaccine (p = 0.0135 and 0.0014 for anti-diphtheria and anti-tetanus, respectively). This study has shown that fluid diphtheria-tetanus vaccine does not solve the problem of extensive local side effects induced by the diphtheria-tetanus school booster. Alternative strategies, such as changes in vaccine composition, dosage and spacing, will have to be considered.

New roles for quin2: powerful transition-metal ion chelator that inhibits copper-, but potentiates iron-driven, Fenton-type reactions

The objective of this study was to investigate whether quin2, through its metal chelating properties, could affect copper- or iron-driven Fenton reactions. Chelation of ferric ion with quin2 uniformly strongly enhanced the formation of oxidizing species, detected with the DMSO and deoxyribose assays, both by H2O2 and a mixture of superoxide/hydrogen peroxide produced by hypoxanthine/xanthine oxidase. Fe(3+)-EDTA gave the same effects, but lacked reactivity with bolus H2O2 as detected with the DMSO assay. Whereas the formation of oxidizing species with Fe(3+)-EDTA and ferric ions alone were strongly inhibited by superoxide dismutase both in the bolus H2O2 and hypoxanthine/xanthine oxidase systems, such formation in the presence of Fe(3+)-quin2 either did not decrease or decreased only moderately. Fe(3+)-quin2 also strongly enhanced plasmid DNA strand breakage in the presence of H2O2. Our findings suggest that quin2 as chelator of ferric ion may be a more powerful enhancer of oxidant formation than other chelators so far tested. The formation of oxidizing species from copper ions and bolus H2O2 was found to be fundamentally dependent on the choice of buffer system. We could only detect significant amounts of oxidants in both assays in Hepes buffer, but not in the phosphate, cacodylate or unbuffered systems, which all gave low reactivity in the DMSO assay compared to the deoxyribose assay. Quin2 chelation of cupric ion effectively inhibited the formation of oxidants as well as plasmid DNA strand breakage.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of erythromycin treatment on antibody responses in pertussis

The effect of erythromycin treatment on antibody responses to Bordetella pertussis filamentous haemagglutinin (FHA) and pertussis toxin (PT) was investigated in convalescent blood samples from 105 children with pertussis. Erythromycin had been given to 59 children, median age 3.2 years (range 0.3-9.9) on median day 7 (range 11-14) after onset of disease while the remaining 46 children, age 3.45 (0.6-8.1) were untreated. No significant differences in IgG antibody concentration were noted to FHA by ELISA and to PT, neither by NT nor by ELISA, but a tendency towards lower median titers was seen to both antigens and by both type of assays in the erythromycin-treated group. Similarly, early erythromycin treatment i.e. within 7 days of onset of symptoms, did not influence significantly of the development of the antibody responses but tended to lead to lower titer levels. A significant response to PT and FHA was found in about 90% of blood samples, irrespective of treatment. All 56 children with culture-confirmed B. pertussis infection had a significant response to PT. The study has thus shown a slight but not significant effect of erythromycin treatment on antibody responses in pertussis.

Immune status and booster effects of low doses of tetanus toxoid in Swedish medical personnel

Of 102 medical staff at a Swedish hospital, 81% had tetanus antitoxin titres > or = 0.01 IU/ml in 1984-85. The unprotected individuals (antitoxin titre < 0.01 IU/ml) were all > 30 years of age. Of this group, one-third lacked a protective antibody level against tetanus toxin. Low booster doses of tetanus toxoid (0.75 or 1.9 Lf) were given to 66 vaccinees with a history of previous basic vaccination and no history of booster vaccination within the previous 5 years. The median titre increased from 0.26 IU/ml before to 3.3 IU/ml after vaccination. Low doses of tetanus toxoid may thus still provide an adequate immune response when given as a booster vaccination to individuals with a reliable history of basic immunization.

Immunoglobulin G antibodies to Pseudomonas aeruginosa lipopolysaccharides and exotoxin A in patients with cystic fibrosis or bacteremia

IgG antibodies to nine Pseudomonas aeruginosa lipopolysaccharides (LPS) and exotoxin A in sera from 11 patients with bacteremia and 51 patients with cystic fibrosis (CF) were analyzed. The methods used were enzyme immunoassay (EIA) and immunoblotting. Nine of the 11 bacteremic patients were infected with strains expressing an LPS serotype identical to one of the test antigens. In sera from six of these nine patients, antibody homologous to the serotype of the infecting strain was observed. An antibody response to heterologous Pseudomonas aeruginosa LPS antigens was observed in nine patients. Eight of the bacteremic patients mounted an antibody response to exotoxin A. Thirty-five CF patients chronically colonized with Pseudomonas aeruginosa possessed significantly higher levels of antibody to all of the test antigens than 16 patients with intermittent or no colonization (p < 0.001). For exotoxin A and serotype 3 the sensitivity was 91% and 94%, and the specificity 94% and 88% respectively. When the results for exotoxin A and serotype 3 were combined, the sensitivity was 91% while the specificity was 81%. The pronounced antibody response to heterologous LPS antigens, as measured by the EIA and immunoblot, suggests expression of a common antigen determinant. A simplified serological assay utilizing exotoxin A and serotype 3 as test antigens may be useful for detecting Pseudomonas aeruginosa infections in patients with CF and chronic colonization and in bacteremic patients from whom cultures are not available.

Helicobacter pylori in 205 consecutive endoscopy patients

The presence of Helicobacter pylori in the gastric, antral mucosa of 205 consecutive, unselected gastroscopy patients was investigated by 1-3 biopsies for urea broth test and culture, 1 biopsy for histological examination and 1 blood sample for serology by ELISA. Overall, 41% were positive for H. pylori by culture, 32% by urea broth test, 24% by histological staining and 67%, 56% and 49% for the 3 cut-off limits applied to serology. Culture and serology indicated the presence of H. pylori in 79-92% of the 14 cases with duodenal ulcer, in 59-82% of the 28 cases with gastric ulcers, in 45-71% of the 51 cases with endoscopic gastritis and in 33-69% of 13 cases with oesophagitis. In patients with histological antritis, H. pylori was identified by culture in 71% (60/84), by serology in 95%, 88% and 81% with the different cut-off limits. The sensitivity of serology ranged from 99-78% depending on the cut-off limits and the specificity from 78-100% against all parameters combined. These results suggest that serology is a useful screening method for the presence of H. pylori. Future antibiotic treatment studies are required to evaluate the clinical relevance of H. pylori in gastrointestinal disease and to investigate the possibility to monitor eradication by serology.

Serological correlates in whooping cough

Antibody concentrations to three Bordetella pertussis antigens in 94 predisease samples from women who, within a median of 220 days, developed culture-confirmed whooping cough were compared to antibodies in samples from matched controls. The median IgG antibody levels were significantly lower to all three antigens, pertussis toxin, filamentous haemagglutinin and lipopolysaccharide, in the predisease samples of cases as compared to non-cases (p values ranging from 0.0001 to 0.01). A significant difference in antibody distribution was, however, found only to pertussis toxin, measured either by ELISA or by a neutralization test (p values of 0.0004 and 0.007, respectively). The results could be interpreted as meaning that antibodies to the different antigens all participate in protection against disease but that antibodies to pertussis toxin play a major role.

Antibody prevalence and clinical manifestations of Lyme borreliosis and tick-borne encephalitis in Swedish orienteers

Antibody prevalence and clinical manifestations of Lyme borreliosis (LB) and tick-borne encephalitis (TBE) were studied in 362 orienteers from the county of Stockholm during a large relay race in October 1990. From all participating orienteers, a blood sample was collected and a questionnaire completed. Antibody activity to Borrelia burgdorferi was measured using a sonicated whole spirochete antigen in an ELISA, and to TBE virus (TBEV) by ELISA and haemagglutination inhibition (HI) test. A past history of LB was reported by 6% of the orienteers and antibodies to B. burgdorferi were found in 9%. Antibody reactivity to B. burgdorferi was found in 1-2% of the sera from 3 different control groups comprising 502 persons living in non-endemic areas. The corresponding value was 9% in sera from a fourth control group consisting of 150 persons living in the city of Stockholm. A past history of TBE was reported by 1 orienteer (0.3%) and detectable antibodies to TBEV in non-immunized individuals were found in 1%. No antibody activity to TBEV could be detected in sera from the control individuals living in the 3 non-endemic areas, but in 5% of the controls from Stockholm. In this study, there was no indication that frequent or severe manifestations of LB or TBE are common among orienteers in Sweden.

Clinical manifestations and antibody prevalence of Lyme borreliosis and tick-borne encephalitis in Sweden: a study in five endemic areas close to Stockholm

Five populations, including 903 individuals living in 5 different areas close to Stockholm, were studied with regard to clinical manifestations and antibody prevalence of Lyme borreliosis (LB) and tick-borne encephalitis (TBE). The study areas involved 4 groups of islands in the Baltic Sea and 1 island in Lake Mälaren. Serum samples from each individual were tested for antibody activity to Borrelia burgdorferi using a sonicated whole spirochete antigen in an ELISA, and to TBE-virus (TBEV) by ELISA and haemagglutination inhibition. A history of LB was reported by 1-21% and antibodies to Borrelia burgdorferi were found in 7-29% of the participants from the various areas. An increasing seroprevalence with age was seen. In sera from 3 different control groups, including 502 individuals living in non-endemic areas, antibodies to Borrelia burgdorferi were detected in 1-2% and from 1 control group including 150 individuals living in the city of Stockholm, in 9%. A history of TBE was reported by 0-6% of the individuals and in non-immunized individuals seropositivity was seen in 4-22%, depending on the area investigated. No antibody activity to TBEV could be detected in sera from persons in the 3 control groups living in non-endemic areas, whereas 5% of the controls from Stockholm were found to be positive. The prevalence rates of antibodies to TBEV in persons vaccinated against TBE were 40%, 53% and 79% after 1, 2 and 3 injections, respectively.

Mutagenic analysis of the promoter of the Streptomyces fradiae beta-lactamase-encoding gene

The Streptomyces fradiae beta-lactamase promoter (PblaF) was sequenced and characterized by promoter probing, primer extension, and exonuclease III-mediated deletions. The transcription start point (tsp) was the same in both S. lividans and S. fradiae. Oligodeoxyribonucleotide-directed random mutations and site-specific mutations were introduced in the promoter region. The effects of these mutations on transcription were assayed by an RNA colony hybridization method. This analysis identified cis-acting sequence determinants located similarly to the -10 and -35 regions of a typical Escherichia coli promoter. Also, a change in the distance between these regions from 19 to 17 bp drastically reduced promoter activity. PblaF was shown not to be recognized by sigma-whiG or by sigma-hrdA, hrdC, or hrdD. Sequence alignment of PblaF to sigma factor-classified Streptomyces promoters revealed little homology. Thus, PblaF is probably recognized by an as yet unidentified sigma factor.

Two-year survey of the incidence of Lyme borreliosis and tick-borne encephalitis in a high-risk population in Sweden

A survey was made over a two-year period (September 1987 to August 1989) of a population living in an area endemic for Lyme borreliosis and tick-borne encephalitis in Sweden. For each patient a blood sample was collected and a questionnaire completed annually. All sera were tested for an antibody response to Borrelia burgdorferi in an EIA using sonicated antigen and for an antibody response to the tick-borne encephalitis virus using an EIA and a haemagglutination inhibition test. Antibodies to Borrelia burgdorferi and tick-borne encephalitis virus were detected in 89 (25.7%) and 40 (11.6%) respectively of 346 samples collected in August 1987. In the first year of the study 14 of 303 subjects (4.6%) developed Lyme borreliosis and in the second year 9 of 277 subjects (3.2%). A significant increase in the antibody titre for Borrelia burgdorferi was seen in 14 of 303 (4.6%) subjects in the first year and 8 of 277 (2.9%) subjects in the second year. An earlier episode of Lyme borreliosis or an elevated antibody titre did not seem to protect against reinfection. One case of tick-borne encephalitis was seen each year. Seroconversion for tick-borne encephalitis virus was found in 3 of 258 (1.2%) subjects in the first year and 5 of 211 (2.4%) in the second year, excluding subjects who had undergone successful immunisation or had earlier been hospitalised for tick-borne encephalitis. The study thus demonstrated a high yearly incidence of tick-borne infections in a population at risk.

Evaluation of an improved DNA probe for diagnosis of pertussis

A Bordetella pertussis specific subclone, pRZ61, of a Bordetella genus-specific clone, pB23, was evaluated on nasopharyngeal aspirates of 179 patients with suspected pertussis. Hybridization was performed directly after spotting or after 1-3 days of preculture of the nylon membranes on solid culture medium. A direct comparison of the two probes was obtained by reprobing with the subclone the same membranes that had been hybridized with the parent probe. pRZ61 detected 50% of the serologically defined cases of pertussis, that is, had the same sensitivity as standard culture. Specificity as compared with serology was close to 100%. The increasing sensitivity and the corresponding decreasing specificity after preculture noted for pB23 was not seen with the subclone. The study showed that the improved probe represents a rapid diagnostic method in pertussis.

Impact of pertussis on the afflicted child and family

The effects of pertussis in an unimmunized population were investigated in 61 children consecutively identified by positive culture for Bordetella pertussis. Parents were interviewed twice, at a mean of 3 and 11 weeks after onset of symptoms. All children had a disease duration of more than 3 weeks. Behavioral changes were reported for 84% of the study children. Parents reported negative effects for themselves in 95% and for siblings in 63% of the families. The main problems were disturbance of night sleep, staying home from work and isolation of the family. Parental knowledge of the disease was generally good; a majority had few contacts with the medical services and coped with the disease themselves. Serious concerns for the child were reported by 51% of parents and fears for permanent sequelae by 10%. The attitude to pertussis vaccination was positive in 89% of cases at both interviews. The study has thus shown that pertussis in an unimmunized child population represents a heavy burden.

Specific immunoglobulin for treatment of whooping cough

Immunoglobulin treatment for whooping cough (pertussis) is widely believed to be ineffective although there are sound reasons for regarding the condition as a toxin-induced disease. We wondered whether the lack of success with pertussis immunoglobulins might be attributable to inadequate dose, so we designed a randomised, double-blind, placebo-controlled trial of two immunoglobulin preparations. The study was conducted at three Swedish hospitals. We enrolled 73 children aged less than 36 months who were admitted with a clinical diagnosis of whooping cough. On admission they were assigned to one of three groups: (a) monocomponent pertussis toxoid vaccine; (b) two-component acellular vaccine also containing filamentous haemagglutinin; or (c) 20% albumin solution (placebo). The immunoglobulins had a high antitoxin content and had been raised with acellular pertussis vaccines. Diagnosis of pertussis was confirmed by laboratory tests and the follow-up was completed in 67 children. The main study group consisted of 47 children with less than or equal to 14 days of disease before therapy. Duration of whoops post-treatment was 8.7 days (95% Cl 4.8, 12.6) in the 33 children receiving immunoglobulin vs 20.6 (95% Cl 11.9, 29.3) in the 14 receiving placebo (p = 0.0041). Mean number of whoops during the first week of follow-up was also significantly reduced (p = 0.0196). We found that early treatment was important, since the effect on duration of whoops was most pronounced when disease duration before treatment was less than or equal to 7 days. There were no significant differences between the two immunoglobulin preparations. High-dose specific pertussis immunoglobulin with a high antitoxin concentration has a beneficial effect in the treatment of whooping cough.

The melanophore aggregating response of isolated fish scales: a very rapid and sensitive diagnosis of whooping cough

Pertussis toxin (PT) has been found to block noradrenaline-induced pigment aggregation in fish melanophores, and, based on this, a rapid and highly sensitive assay for PT was developed. Some preliminary results have also indicated that it may be possible to detect PT-like activity in saliva samples from patients with clinically suspected pertussis. In the present study the diagnostic value of the fish melanophore method was evaluated in 70 patients suspected of having pertussis; culture, serology and physician diagnosis were used as reference methods. In 60 of the patients, pertussis was verified by at least one of the reference methods. The melanophore test showed PT-like activity in saliva samples from 58 of the patients. Three patients with reference-verified pertussis showed no PT-like activity in the test; among these, one patient had been immunized and had also been treated with erythromycin during 3 days immediately prior to visiting the hospital. The melanophore test has three major advantages: it allows detection of pertussis in the early and curable stage of the disease; it takes only 2 h to perform; and it requires no sophisticated equipment.

Lipase versus teichoic acid and alpha-toxin as antigen in an enzyme immunoassay for serological diagnosis of Staphylococcus aureus infections

Titres of IgG antibodies to Staphylococcus aureus lipase were analysed in 448 sera from patients suspected of having Staphylococcus aureus infections and the results compared to those for the routinely used staphylococcal antigens teichoic acid and alpha-toxin. The results indicated that determination of serum antibodies to lipase is a sensitive assay for serological diagnosis of staphylococcal infections and increased sensitivity may be achieved by selection of optimal antigen combinations.

Cumulative incidence of pertussis in an unvaccinated preschool cohort based on notifications, interview and serology

The cumulative incidence of pertussis at six years of age in the first unvaccinated cohort after cessation of immunisation in Sweden was investigated by serological methods and by a validation of the national epidemiological surveillance system by reports from the Child Health Centres (CHCs). In 312/385 (81%) eligible children, both an interview with the parents and a blood sample from the child could be obtained. The CHC reports yielded a cumulative incidence of 31%, whereas the serological assays found 54%. Of the cases reported by the parents to the CHCs, 89% were seropositives. In the additional cases of pertussis reported at the study interview, only 61% could be confirmed (p less than 0.001). Among children with reported severe cough not suspected to be pertussis, 46% were seropositive, distributed as 33% seropositives in cases with cough duration of less than 4 weeks and 69% for longer coughs (p less than 0.01). In the CHC reports, the parental diagnosis was found to have been confirmed in three-quarters of cases by medical personnel. The CHC reporting system was thus found to be reliable with an observed specificity of 93%, but sensitivity of only 52%. Thus, even this surveillance system, which yields the highest incidence rates, underestimates the incidence of the disease.

Bordetella pertussis adenylate cyclase activity in nasopharyngeal aspirates for rapid diagnosis of whooping cough in relation to culture and serology

Adenylate cyclase activity, measured in 201 nasopharyngeal aspirates from patients presenting with own or parental suspicion of whooping cough, was compared to diagnosis made by culture and by serology in the culture negative cases. The median amount of cyclic AMP in samples from culture negative patients (n = 145) was 0.60 pmoles which differed significantly (p less than 0.001) from the median value 3.28 in samples from culture positive patients (n = 56). The median value 0.70 pmoles of cyclic AMP in samples from culture negative patients who were positive by serology (n = 54) did not differ significantly from the value of 0.57 pmoles in samples from serology negative patients (n = 91). With a limit for positive cyclic AMP set at 2 pmoles, 45 samples were positive. The sensitivity of the assay was 66% (37/56) in culture positive patients while the specificity was 93% (85/91) in the serology negative patients. The positive predictive value for the c-AMP test was 82% (37/45) in relation to culture and 87% (39/45) in relation to culture and/or serology. The results confirmed that measurement of adenylate cyclase activity in nasopharyngeal aspirates by an 1-h incubation method can serve as an early and rapid diagnostic method of pertussis infection. The low sensitivity of the c-AMP assay in samples from serology positive but culture negative patients indicates however, that this assay will have to be supplemented by serology for a high diagnostic sensitivity in all cases of pertussis.

Diagnostic value of clinical and bacteriological findings in pertussis

Clinical and bacteriological findings in the diagnosis of pertussis were evaluated in 300 consecutive patients with parental or the patient's own suspicion of the disease. Serology was used as a reference method. Of the 285 (95%) patients fully sampled, 163 (57%) were diagnosed as having pertussis while the remaining 122 patients constituted the non-pertussis control group. The clinical and epidemiological data were collected at the first visit made on median day seven of illness. In this population of mainly unimmunised children, the highest predictive values were obtained for the physician's diagnosis of pertussis (100%) and for the physician's diagnosis of some other illness (93%). The only clinical symptom with a high predictive value for pertussis was the report of whoops (92%). Among epidemiological data the highest predictive value (90%) was obtained for reported household exposure in unimmunised children more than 1 year of age. Culture of Bordetella pertussis was found to have an overall 50% sensitivity. Isolation of other bacteria had no predictive value in the differential diagnosis of pertussis.

DNA hybridization for diagnosis of pertussis

The aim of the present study was to evaluate a mixed phase DNA hybridization assay for detection of Bordetella pertussis and Bordetella parapertussis in nasopharyngeal aspirates from patients with suspected pertussis. Among 179 consecutive patients with own or parental suspicion of pertussis, the diagnosis was confirmed in 103 patients by serology and in 52/103 (50%) cases also by culture. The remaining 76 patients served as nonpertussis controls. Direct hybridization was positive in 38% samples with serology as reference method, a non-significant difference to the 50% sensitivity for culture. Preculture of samples on membranes for 24, 48 and 72 h gave a significantly higher sensitivity only with 72 h preculture, 69% vs 50% (P = 0.007). The 72h preculture gave, however, also a significant decrease of specificity, 87% vs 100% for routine culture (P = 0.001) and is not a more rapid diagnostic method. The result shows that rapid diagnosis by DNA hybridization can be achieved in a large proportion of pertussis cases. The presence of smaller numbers of bacteria in samples only positive after preculture indicate that DNA hybridization could be a highly sensitive diagnostic method with further development of more rapid amplification systems.