pertussis PCR assay

BACKGROUND

The FilmArray Respiratory Panel (RP) detects multiple pathogens, including Bordetella pertussis. The multiplex PCR system is appropriate for a core laboratory or point of care due to ease of use. The purpose of this study is to compare the analytical sensitivity of the FilmArray RP, which targets the promoter region of the B. pertussis toxin gene, with the Focus real-time PCR assay, which targets the insertion sequence IS481.

METHODS

Seventy-one specimens from patients aged 1 month to 18 years, which had tested positive for B. pertussis using the Focus assay, were analysed using the FilmArray RP.

RESULTS

Forty-six specimens were positive for B. pertussis by both the Focus and the FilmArray RP assays. Twenty-five specimens were negative for B. pertussis using the FilmArray RP assay, but positive using the Focus assay.

CONCLUSIONS

The FilmArray RP assays will detect approximately 1/3 less cases of B. pertussis than the Focus assay.

Immunity in mice to an intracerebral challenge of Bordetella pertussis

The survival rate of mice actively or passively immunized against intracerebral challenge with Bordetella pertussis, was independent of the size of challenge dose within the range of 20–2000 LD.

This unexpected result appears to be due to the anatomical peculiarities of the infected organ, in which circulating antibody does not pass the normal blood-brain barrier easily. The pertussis infection does not cause sufficient inflammation to induce a pathological increase in the permeability of the barrier until the number of living microbes in the brain reaches 10 to 10. Since this stage in the brain consistently occurs after 4–5 days, independently of the size of the inoculum within the range 20–2000 LD, the outcome of infection in the immunized animal depends solely on the degree of specific immunity.

In the non-immune mouse, the increase in permeability of the barrier persists until death. In the immunized mouse, the elimination of the infection leads to a restoration of the normal barrier at about the 6th day.

Experiments designed to determine the mechanism of the adjuvant activity of gram-negative organisms upon antibody production

The characteristics of Gram-negative organisms and some of the underlying reasons for their adjuvant action with diphtheria toxoid are described.

The adjuvant effect was shown by an earlier production of antitoxin, with a maintained differential advantage over controls, but with the usual decline in titre with passage of time. The adjuvant effect only occurred with a primary stimulus. There was no adsorption between toxoid and vaccine and mixture of the two was not necessary, but the vaccine had to be given simultaneously with or within 24 hr. following injection of the toxoid. There was evidence for believing that these adjuvants decreased the minimal stimulating dose of antigen and caused hyperplasia of antibody-producing cells. No direct link could be found between the characteristic stress symptoms caused by lipopolysaccharides and their ability to enhance antibody formation.

SODIUM SULPHOMETHYL DERIVATIVES OF POLYMYXINS

Variations in the treatment of polymyxin B and polymyxin E (colistin) with formaldehyde and sodium bisulphite produce sulphomethyl derivatives which differ quantitatively in acute toxicity and in antibacterial activities in vitro and in vivo. The acute intravenous LD50 values of some sixty samples of these derivatives range from six- to more than eighty-fold those of the parent antibiotics; the in vitro antibacterial activities range from 2 to 12% and the in vivo activities from 20 to 50% of those of the parent antibiotics, with the most toxic derivatives showing the highest activities. When short and prolonged incubation methods are used, assays of the derivatives in solutions of different ages and of blood collected from man and dog after intramuscular injection, show that the antibacterial activities of these sulphomethyl derivatives depend on reversion to the unsubstituted form, and that the differences in the activities are due to variations in stability. These conclusions are supported by comparison of these sulphomethyl derivatives with stable acetyl derivatives. The lower in vivo activity is due, at least partly, to the high renal excretion of the substituted form. Electrophoresis shows that the derivatives are composite, the components corresponding to mono- to pentasulphomethyl polymyxin. Pain at the injection site is the most troublesome side-effect of polymyxin therapy, and this is avoided with these derivatives. In rats injected with quantities some twenty-times the usual human dose, the derivatives cause transitory decrease in urinary output and transitory proteinuria. After intramuscular injection of these derivatives into dogs, no antibiotic is detectable in the cerebrospinal fluid and concentrations present in the bile are not significantly different from those after injection of the parent antibiotic. When injected intracisternally into these animals, derivatives are less toxic than the parent compounds. These studies show that acute intravenous toxicity is a useful index of therapeutic efficiency and that derivatives with intravenous LD50 values of about 100 mg/kg are the most satisfactory ones. Because activity depends on reversion to the parent antibiotic, the use of these derivatives for topical application is contraindicated.

STUDIES ON THE LYMPHOCYTOSIS INDUCED IN MICE BY BORDETELLA PERTUSSIS

1. Intravenous injection into mice of phase I Bordetella pertussis vaccine resulted in a striking hyperleucocytosis with a predominating lymphocytosis. Intraperitoneal inoculation was less effective, and subcutaneous administration was inactive. 2. Active immunization prevented the hyperleucocytosis; passive immunization was less effective. 3. Reticuloendothelial blockage reduced the effect of the vaccine. 4. Extirpation of the spleen or thymus did not alter the leucocyte response. 5. Histologic studies suggested that the increase in circulating lymphocytes resulted from release of cells from lymphoid organs, including the thymus.

STABILIZATION OF PERTUSSIS VACCINE IN THE PRESENCE OF BENZETHONIUM CHLORIDE

Olson, B. H. (Division of Laboratories, Michigan Department of Health, Lansing), Grace Eldering, and Bernice Graham. Stabilization of pertussis vaccine in the presence of benzethonium chloride. J. Bacteriol. 87:543-546. 1964.-Data are presented showing that pertussis vaccine preserved with benzethonium chloride (BC; Phemerol) was inactivated during storage. BC-preserved vaccine stored at 37 C showed no measurable mouse-protective potency at 16 weeks. That stored at 0 to 4 C lost approximately 80% of its potency within 1 year. Treatment of pertussis vaccines with aluminum, calcium, magnesium, choline, or dl-lysine before the addition of the BC prevented its uptake by the cells. Pertussis vaccines pretreated with 0.004 m Ca(++) or 0.0004 m Al(+++) retained 70% of the initial potency after 42 weeks of storage at 37 C. Similar vaccines showed no loss of protective antigens when stored for 1 year at 0 to 4 C.

ISOLATION OF HIGHLY POTENT TOXIN FROM BORDETELLA PERTUSSIS

Onoue, Kaoru (Kyushu University, Fukuoka, Japan), Masayasu Kitagawa, and Yuichi Yamamura. Chemical studies on cellular components of Bordetella pertussis. III. Isolation of highly potent toxin from Bordetella pertussis. J. Bacteriol. 86:648-655. 1963.-The thermolabile toxin of Bordetella pertussis was extracted at alkaline pH with 0.15 m saline from the disrupted cells. The toxin was purified successively by calcium phosphate gel treatment, ammonium sulfate fractionation, precipitation with potassium phosphate at alkaline pH, and finally by chromatography on a diethylaminoethyl cellulose column. Although the purified toxin still contained a small amount of agglutinin-absorbing activity, and inhomogeneity was detected by the agar gel diffusion test, the lethal and skin-necrotizing activities were much higher than those previously reported. The data obtained suggest that the toxin is proteinaceous.

AN AETIOLOGICAL STUDY OF RESPIRATORY INFECTION IN CHILDREN, EDINBURGH CITY HOSPITAL, 1961-1963

The findings are described of a combined clinical, bacteriological and virological study which included all children admitted to the City Hospital, Edinburgh, with acute respiratory infection and whooping cough during the winters 1961–62 and 1962–63. During the first winter 131 cases aged 0–12 years and in the second winter 133 aged 0–6 years were examined. The respiratory illnesses were divisible into upper respiratory tract infection, bronchitis, pneumonia, and whooping cough; many of the cases of whooping cough had respiratory complications with bronchitis or pneumonia.

Paired sera, a throat swab and a faecal specimen were taken from each child and investigated vircdogically. Over both winters the highest total virus isolation rate was found in the group suffering from upper respiratory disease. Approximately two-thirds of the total number of patients from whom virus was isolated and from whom both acute and convalescent sera were available gave a serological response to the homologous virus; the highest proportion of these patients occurred in the pneumonia and URTI groups. The groups of viruses associated with a fourfold or greater rise in antibodies occurred in the following proportions of the cases: myxovirus 9 %; adeno virus 7 %; entero virus 4 %; herpes simplex 3 %.

Bacterial pathogens were isolated from 37 % of patients in 1961–62 and from 49 % in 1962–63,Staph. pyogenesbeing the most common pathogen. Isolation of pneumococci was facilitated during the second year by the examination of a nasal swab. Pre-admission chemotherapy did not significantly alter the bacterial isolation rates. Agglutination studies were carried out on forty clinical cases of whooping cough admitted during the two winters and thirty-two showed significant stable titres toBordetella pertussis; only 9 (18 %) of these cases gave a history of prophylactic immunization.

A third of the patients had neither bacterial nor viral pathogens.

The findings in this survey illustrate the need for further intensive virological and bacteriological studies of acute respiratory infections in early childhood.

THE CONTENT OF ANTIGENS 1,2 AND 3 IN STRAINS OF BORDETELLA PERTUSSIS AND IN VACCINES

A comparison was made of the content of heat-labile antigens 1, 2 and 3 in strains of Bordetella pertussis isolated in Toronto, and the content of the same antigens in vaccines being used in that community. Antisera were prepared in rabbits and made monospecific by absorptions. Antigens were detected by slide agglutination tests. Of the 58 strains examined, 56 contained antigens 1 and 3 but no antigen 2 was detected. Nine of these strains were isolated from children who had received a full course of vaccination and had subsequently developed pertussis. All 10 vaccines examined contained antigen 1; two, possibly four, contained no antigen 2; and seven of the 10 vaccines were weak or deficient in antigen 3. This work suggests that improved protection might be attained by the use of vaccines containing adequate amounts of all three antigens.

THE MECHANISM OF ANAPHYLAXIS. II. THE ROLE OF 'MAST CELL SENSITIZING' ANTIBODY AND DELAYED HYPERSENSITIVITY IN RAT ANAPHYLAXIS

Both immediate and delayed cutaneous reactions were found to be present in rats actively sensitized by the injection of antigen plus Bordetella pertussis organisms. Delayed hypersensitivity preceded the appearance of `mast cell sensitizing' antibody (MCSAb) in those animals which were only fully susceptible to anaphylaxis when both delayed and immediate reactions had reached their maximum. Passive anaphylaxis with MCSAb was fatal only when transferred to actively sensitized rats at a time when the animals had delayed cutaneous reactions but were not yet fully susceptible to anaphylaxis. It is suggested that anaphylaxis in rats is due to an additive or synergistic effect between immediate and delayed hypersensitivities.

AN ELECTRON MICROSCOPIC STUDY OF EXPERIMENTAL ALLERGIC ENCEPHALOMYELITIS IN THE RAT

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