Non-toxigenic Corynebacterium diphtheriae in military personnel

Non-toxigenic Corynebacterium diphtheriae: two cases and review of the literature

Non-toxigenic Corynebacterium diphtheriae infections are being reported with increasing frequency. We present two cases of C. diphtheriae endocarditis requiring early valve replacement. Both cases were complicated by cerebral embolic phenomena and pseudoaneurysm formation in lower limb arterial vessels. Non-toxigenic C. diphtheriae septicaemia must be excluded when 'diphtheroids' are isolated from blood cultures.

Characterization of bacteriophages from tox-containing, non-toxigenic isolates of Corynebacterium diphtheriae

Non-toxigenic strains of Corynebacterium diphtheriae continue to cause disease within immunized populations. A subset of these corynebacteria carry the diphtheria toxin gene but in a cryptic form. To determine whether such strains might contribute to the re-emergence of functional toxin genes, the phages and tox mutations within three clone types were examined. tox-containing, beta-related phages were isolated from two of the strain types. The third isolate appeared to harbour a defective prophage. One of the tox- phages encoded truncated, yet enzymatically-active, forms of diphtheria toxin, suggesting that it had sustained a point mutation within the latter half of its toxin gene. In contrast, the other mutant phage did not elicit the production of either a cross-reacting material or an ADP-ribosylating activity. Complementation tests employing a series of double lysogens confirmed that the mutations responsible for the non-toxigenic phenotype of all of the phages were cis dominant. Given these findings, it is reasonable to hypothesize that tox+ genes can arise within human populations by either homologous recombination between two distinct tox- phages or spontaneous reversion within a single mutant allele.

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.

Arcanobacterium haemolyticum and streptococcal pharyngitis in army conscripts

Arcanobacterium haemolyticum was found in 1.4% and beta-haemolytic streptococci in 23% of throat cultures from army conscripts with sore throat (n = 498). 38% of the beta-haemolytic streptococci were of group A. Patients culture-positive for A. haemolyticum or beta-haemolytic streptococci had pharyngeal exudate, cervical lymphadenopathy and ear ache significantly more often--but cough less often--than culture-negative patients. The pharyngeal colonization rate of healthy conscripts (n = 232) by A. haemolyticum was 0.4% and by beta-haemolytic streptococci, 6.5%.