Unusual non-toxigenic Corynebacterium diphtheriae in homosexual men

Emergence of an invasive clone of nontoxigenic Corynebacterium diphtheriae in the urban poor population of Vancouver, Canada

Invasive disease due to Corynebacterium diphtheriae is rare in North America. Here we describe the emergence of a predominant clone of a nontoxigenic strain of C. diphtheriae in the impoverished population of Vancouver's downtown core. This clone has caused significant morbidity and contributed to at least two deaths. Over a 5-year period, seven cases of bacteremia due to C. diphtheriae were detected in patients admitted to Vancouver hospitals. Injection drug use, diabetes mellitus, skin colonization/infection with C. diphtheriae, and homelessness all appeared to be related to the development of bacteremia with the organism. Ribotyping of isolates recovered from blood culture revealed a predominant ribotype pattern that has not previously been reported in North America.

Nontoxigenic corynebacterium diphtheriae: an emerging pathogen in England and Wales?

Confirmed isolates of nontoxigenic Corynebacterium diphtheriae in England and Wales increased substantially from 1986 to 1994. Ribotyping of 121 isolates confirmed in 1995 showed that 90 were of a single strain isolated exclusively from the throat; none had previously been identified in toxigenic strains from U.K. or non-U.K. residents. The upward trend in nontoxigenic C. diphtheriae probably represented increased ascertainment, although dissemination of a particular strain or clone may have been a factor.

Nasopharyngeal flora in HIV seropositive men who have sex with men

OBJECTIVES

To assess, in men who were infected with the human immunodeficiency virus (HIV) and who identified themselves as having had sex with men; the nasopharyngeal prevalence of Neisseria gonorrhoeae, N meningitidis, Corynebacterium diphtheriae, and candida species; oral sexual behaviour; the relation between oral flora and oral sexual behavior.

METHOD

Nasopharyngeal swabs were taken from HIV seropositive men for culture. The men were also asked to complete a self administered questionnaire.

RESULTS

390 men were recruited; 286 (73.3%) provided nasopharyngeal samples and questionnaires; 41 (10.5%) provided nasopharyngeal samples only; 63 (16.2%) provided questionnaires only. From the 327 nasopharyngeal samples N meningitidis was cultured in 49 (15%) and candida species in 165 (50.5%). Cultures for N gonorrhoeae and C diphtheriae were all negative. Data from the 349 completed questionnaires indicated that 285 men were practising oro-penile sex, over 90% did not consistently use condoms; 150 men were practising oro-anal sex, one used dental dams. In those providing both nasopharyngeal samples and sexual behaviour data meningococcal carriage was identified in 40 (17.5%) of the 228 men practising receptive oro-penile sex, compared with one (2.3%) of the 43 non-practisers (p < 0.025); in 21 (20%) of the 105 men practising insertive oro-anal sex, compared with 17 (12.5%) of the 136 non-practisers (p = 0.12). No correlation was identified between yeast carriage and oro-genital sex.

CONCLUSION

Oro-genital sex, usually without barrier protection, is common among HIV infected men who have sex with men. It appears to be associated with increased meningococcal carriage but is autonomous to candida species isolation. Routine screening for nasopharyngeal N gonorrhoeae is not deemed necessary.

Apport des méthodes de typage dans l'étude des souches de Corynebacterium diphtheriae

Corynebacterium diphtheriae is the causative agent of Diphtheria. This bacteria circulates throughout the world. Recently, two outbreaks occurred in New independent states (Russia, Ukraine...) and Algeria. Routine technics permit to study the strains of Corynebacterium diphtheriae : biotype, antibiotype, toxin gene detection. However, molecular biological tests (ribotyping, and pulsed field gel electrophoresis) are necessary to characterize these strains in the space and the time. The studies with international laboratories exchanges are recents and have permitted first results concerning the molecular epidemiology of C. diphtheriae strains.

Non-toxigenic Corynebacterium diphtheriae biovar gravis: evidence for an invasive clone in a south-eastern Australian community

OBJECTIVE

To determine the prevalence and clonality of non-toxigenic Corynebacterium diphtheriae biovar gravis in a community with two cases of endocarditis caused by this organism.

SETTING

A Koorie (Aboriginal) community in Gippsland, eastern Victoria, in 1994.

METHODS

Nose and throat swabs were collected from 359 community contacts of the cases and cultured for C. diphtheriae. Strains isolated from the contacts were compared by pulsed-field gel electrophoresis (after digestion with Sma1, Not1 and Sfi1) with those from the invasive cases in the same community, another invasive case in Victoria, a cluster of invasive cases in New South Wales (NSW) (1990-1991), and other stored strains isolated from skin ulcers and sore throats.

RESULTS

Non-toxigenic strains of C. diphtheriae biovar gravis were isolated from throat swabs of five of the case contacts. Uniform DNA patterns were found for the two community cases, the other Victorian case, nine of ten isolates from NSW, and the five throat isolates from case contacts.

CONCLUSION

An invasive clone of C. diphtheriae biovar gravis appears to have been responsible for the three Victorian cases of endocarditis. It was also present among case contacts and responsible for previous invasive cases in NSW. Prophylactic treatment should be considered for clearly defined contacts in all instances where C. diphtheriae is isolated from a normally sterile site, regardless of the toxigenic nature of the strain.

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.

Pharyngeal flora in a sexually active population

During a 7-week period 1141 patients attending the Genitourinary Clinic at Charing Cross Hospital completed a brief questionnaire and had pharyngeal swabs cultured for Neisseria spp, beta-haemolytic streptococci, corynebacterium and yeasts. The study included 397 heterosexual men, 492 heterosexual women, 189 homosexuals, 41 lesbians and 22 bisexual men and women. Four hundred and sixty patients (40%) admitted oro-genital contact in the preceding 2 weeks. The meningococcal carriage rate was 11.6%. Homosexuals had the highest carriage 23.8% and heterosexual females the lowest 5.9%. Significant differences in carriage rates were found between homosexual and heterosexual men (P < 0.0001), heterosexual men and women (P < 0.005) and between lesbian and heterosexual women (P < 0.025). Recent oro-anal contact significantly increased meningococcal isolation (P < 0.001). A significant association between beta-haemolytic streptococci and concomitant meningococcal carriage was also found (P < 0.01). Sexual orientation and oro-genital contact influences both meningococcal and pharyngeal yeast isolation and should be considered when interpreting pharyngeal culture results.

Diphtheria: changing patterns in the developing world and the industrialized world

In the past, diphtheria was considered one of the most serious childhood diseases because it took a heavy toll in health and life among preschool-aged children. Prior to the widespread availability of diphtheria toxoid, nearly 70% of cases were in children younger than 15 years of age. In the industrialized countries, immunization against diphtheria became widespread in the 1940s and 1950s. This led to a marked decrease in the incidence of diphtheria. There was also a decrease in circulating toxigenic Corynebacterium diphtheriae organisms, resulting in less natural boosting of antibody levels. This had led to gaps in the immunity of the adult population. Since 1990, diphtheria has made a spectacular comeback in several European countries, with a high proportion of cases in adults. In developing countries, immunization of infants with diphtheria toxoid was introduced with the Expanded Programme on Immunization in the late 1970s. Coverage rose slowly to 46% in 1985 and 79% in 1992. Because the pool of immunized persons is not yet large, the process of maintaining immunity still operates through natural mechanisms, including frequent skin infections caused by C. diphtheriae. But recently, several developing countries where coverage has been high for 5-10 years have reported diphtheria outbreaks. These outbreaks have been characterized by high case fatality rates, a large proportion of patients with complications, and their occurrence in both young and older age groups. In all countries, priority should be given to efforts to reach at least 90% coverage with three doses of diphtheria toxoid in children below one year of age. In countries where diphtheria has been successfully controlled, immunity levels should be maintained by booster doses.