Diphtheria in the immunized with observations on a diphtheria-like disease associated with nontoxigenic strains of Corynebacterium diphtheriae

Serum antibodies to diphtheria-tetanus-pertussis vaccine components in Argentine children

The Argentine vaccination schedule against diphtheria, tetanus and pertussis (DTP) recommends three doses of DTP vaccine at 2, 4 and 6 months of age, two boosters at 18 months and 6 years, a booster dose of tetanus vaccine every 10 years and two doses during pregnancy. To evaluate the effect of this schedule, antibodies against pertussis toxin (PT) and filamentous hemagglutinin (FHA) and against tetanus and diphtheria toxoids were determined by ELISA in serum samples from children (1 month to 6 years) who received different doses of DPT vaccine: 0 dose (n = 50), 1 dose (n = 25), 2 doses (n = 25), 3 doses (n = 55), first and second booster (n = 25); 25 pregnant women and their offspring, and 45 adults. High antibody levels against PT (> 140 EU/ml) and FHA (> 80 EU/ml) were recorded in mothers and in the newborn. Antibody titers against PT increased with the number of doses given and decreased with time. Full protection against tetanus (titers > 0.1 IU/ml) was observed in the group of adults (0.37 IU/ml), in mothers (4.4 IU/ml) and their newborn offspring (5.5 IU/ml), and in children after receiving the second dose of DTP vaccine (1.86 IU/ml). The immune status for diphtheria was far lower, as most of the groups lacked adequate protection. After the third dose of DTP vaccine, only 78% of the children had antibody titers above the protective level (0.1 IU/ml). Since antibody levels considered to provide full protection were only achieved after the first booster dose of DTP vaccine, the primary three-dose schedule seems to be insufficient to confer adequate immunity in all vaccinees. Because of the high proportion of non-protected adults, a booster dose of Td vaccine should be considered for this group.

The return of Corynebacterium diphtheriae: the rise of non-toxigenic strains

With the decline in incidence of diphtheria in Europe and the USA, many laboratories no longer routinely culture throat swabs for Corynebacterium diphtheriae. However, there is an outbreak of infection with toxigenic strains in Russia and most adults do not have protective levels of antibody. Non-toxigenic strains are known to cause local disease and lysogenic conversion probably occurs in vivo as well as in vitro. Non-toxigenic C. diphtheriae var. gravis, formerly quite rare, has been isolated with increasing frequency in the UK over the last five years. During prospective screening at one Sexually Transmitted Disease Clinic, six (1%) of 578 homosexual men were found to harbour the organism in the throat, four of them with clinical pharyngitis. Only one of 1696 heterosexual men and women were found to be carriers. Seven cases of endocarditis due to this organism were reported in a single year in Sydney, Australia and non-toxigenic C. diphtheriae var. mitis has caused four cases of endocarditis in Switzerland. Non-toxigenic strains are responsible for pharyngitis and occasional invasive disease and should be treated. Routine screening of throat swabs should not be abandoned.

Vaccine immunity to diphtheria: a 20-year follow-up study

A cohort of close to 70 children born in 1967-68 was followed for estimations of serum antitoxin levels against diphtheria. During the first 3-year-period after vaccination the mean level declined from 0.05 international units (IU) to 0.03. From the year before to the year after the booster of 0.5 LF of toxoid was given at the age of 8 years, the mean level raised from 0.01 to 0.06 IU. At 18 years the mean was again down to 0.01. Between 18 and 23 years of age a difference between the sexes was seen (higher levels in men). The explanation of this phenomenon must be the extra booster given to those young men who have done their compulsory military service.

Immunity and immunization of children against diphtheria in Sweden

The level of immunity to diphtheria and the effect of vaccination with different doses of diphtheria toxoid was investigated. The 457 study children, 6, 10 and 16 years of age, had as infants received routine primary vaccination with three doses of diphtheria-tetanus-toxoid or diphtheria-tetanus-pertussis vaccine, and the 16 year-olds also had received a booster dose of tetanus with a small dose of diphtheria at the age of ten. Prior to the study booster, 15% of the 6-year-olds had antitoxin levels against diphtheria less than 0.01 IU/ml, the given minimum level for protection. Of the 10-year-olds, 48% had titres less than 0.01 IU/ml, while the corresponding figure for the 16-year-olds was 24%. After a booster injection of 0.1, 0.25 or 0.5 ml of diphtheria-tetanus vaccine, more than 97% of the children showed titre levels greater than or equal to 0.1 IU/ml, while levels of greater than or equal to 1 IU/ml, indicating titres sufficient for long-term protection, were attained by 23-96%. Systemic reactions were few and moderate. Local reactions were of little clinical significance. In a group of 5-years-olds given diphtheria-tetanus primary vaccinations over wider intervals, only 1.4% had antitoxin titres less than 0.01 IU/ml. The results show a need for serologic monitoring of vaccination programmes.

Adverse reactions and immunogenicity in adults to regular and increased dosage of diphtheria vaccine

Booster doses of 3 Lf or 7.5 Lf of a regular diphtheria vaccine were given to 200 previously immunized adult volunteers. The toxoid was prepared from toxin with a purity of 2100 Lf/mg protein nitrogen and adsorbed to aluminium phosphate. Systemic reactions were rare and no severe symptoms were observed. Local reactions occurred in 40-50% of the vaccinees, but in only 7.5% were they of clinical significance, i.e. an area of redness/swelling greater than 5 cm. The two doses did not cause significant differences in reaction rates, and the 7.5 Lf dose elicited a better antitoxin response. Thus, a dose of 7.5 Lf diphtheria toxoid of similar purity can safely be given to adults in vaccines.

Antitoxin antibody levels and the outcome of illness during an outbreak of diphtheria among alcoholics

During an outbreak of diphtheria among alcoholics in Göteborg, Sweden, a study was made of the diphtheria-antitoxin antibodies in serum samples from 8 clinical cases and 36 carriers of toxin-producing Corynebacterium diphtheriae. 33/36 carriers were antibody-positive and had antitoxin titres greater than 0.01 IU/ml, a level which is regarded as relative protective, while only 1/8 clinical cases had such a titre. This patient presented a mild illness with no complications. The results of the study of this outbreak stress the importance of maintaining adequate antibody levels against diphtheria in highly developed societies.

Non-toxigenic Corynebacterium diphtheriae in a boarding school

A non-toxigenic strain of Corynebacterium diphtheriae var. gravis was isolated from 31 boys during an outbreak of sore throats at a boarding school of 15 staff and 134 pupils. Despite the non-toxigenicity of the strain involved, conventional isolation procedures were observed and all boys at the school were treated with antibiotics. Restrictions on the school were only relaxed when no further carriers were detected. The rationale of such management of an episode involving a non-toxigenic strain is discussed.

Diphtheria toxin: mode of action and structure

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Corynebacterium diphtheriae and its relatives

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Problems concerning the prophylaxis, pathogenesis and therapy of diphtheria

The first part of this article on the prophylaxis, pathogenesis and therapy of diphtheria is devoted to an epidemiological survey of the results achieved with active immunization against the disease. From these results it can be concluded that active immunization has been largely responsible for the decrease in the morbidity and mortality rates which has taken place in the past half-century.In the second part, the authors deal at length with problems relating to the pathogenesis and therapy of the disease, discussing such subjects as the different types of diphtheria bacteria, the significance of non-virulent strains, the action of bacteriophages, the plurality of diphtheria toxin, the use of antibacterial sera, and the importance of the "avidity" of antitoxic sera.Finally, taking into consideration the data presented in the preceding parts, the authors put forward their views as to the cause of diphtheria, the measures which should be taken to control it, and the most satisfactory form of therapy.