A cutaneous crisis, a toxic tropical pathogen and a public health alert

(Aotea News, August 2010)

Mark Jones
Clinical Microbiologist

The Illness

In October 2009, a 44-year-old Samoan man returned from Samoa after receiving a traditional tattoo to commemorate the death of his wife. A few days later, the tattoo wound became infected.

His GP submitted a swab for culture and prescribed a course of Erythromycin but this was not taken.

The wound deteriorated and the patient developed signs of sepsis with a cardiac arrhythmia. He was admitted to Hutt Hospital and received intravenous antibiotics and intense monitoring in ICU.

He was discharged after five days to complete antibiotics at home. His wounds had healed well but there will likely be residual scarring.

The cause of infection

A gram stain of the swab showed pus cells, Gram-positive cocci and many Gram-positive rods arranged in palisades and “Chinese letter” configurations — an appearance typical of “tropical ulcer”. Culture yielded heavy growths of Staphylococcus aureus, Corynebacteriumdiphtheriae (var gravis) and normal skin flora — the classical isolates from “tropical ulcer”.

The “diphtheria bacillus” was referred to ESR for urgent testing for the presence of the diphtheria toxin gene by PCR.

This was positive, confirming the diagnosis of toxigenic cutaneous diphtheria in this patient — an exceedingly rare event in New Zealand with the significant public health implication of an impending outbreak of pharyngeal diphtheria in susceptible contacts.

Public Health response

Despite cutaneous diphtheria not being a notifiable disease in New Zealand, this case was urgently referred for Public Health appraisal and epidemiological assessment.

We decided to embark on urgent screening of contacts — mainly close family members and health care contacts of the index case.

A total of 27 contacts were screened for C. diphtheriae carriage through nasal and throat swabbing onto “Tinsdale’s medium” on which C. diphtheriae grows as black colonies.

The only isolate was obtained from a young, close family member who had developed an infected lesion on her arm, confirming contact transmission had occurred with a second case of toxigenic cutaneous diphtheria. She was withdrawn from school, treated with oral Erythromycin and made an uneventful recovery.

Some contacts were given prophylaxis with either Erythromycin or Penicillin G. All contacts who had not received a diphtheria vaccine booster in the last five years were given a diphtheria vaccine. No secondary cases of pharyngeal diphtheria have been identified.

Lessons learned

Humans are the only known reservoir for diphtheria and contact with an infected person or fomites is the usual means of transmission.

The index case likely acquired the organism from contaminated tattoo instruments at the time his tattoo was performed but he did not develop symptoms until several days after arriving back in New Zealand.

Rapid air travel has redefined the borders of what are traditional tropical diseases.

Cutaneous diphtheria is rare outside the tropics and toxigenic strains are exceedingly rare in New Zealand, but it is the diphtheria toxin which probably caused the arrhythmia and cardiac toxicity in this patient’s early illness.

An early Public Health response is vital to prevent secondary transmission. Vaccination offers the best protection, especially when epidemics occur.

Finally, careful evaluation by the GP and good communication with the laboratory is essential in order to decide how to process specimens and to interpret the significance of the cultures.

In this case, being told the patient had been tattooed in Samoa provided us with the vital clue as to what to look for in the bacterial cultures.