Patient 1

In September 2002, a 6-year-old girl appeared for treatment with an infected mosquito bite on the ankle and chest lesions. The lesions developed while she was traveling with her mother and four siblings in Bangladesh. Her 12-year-old sister also had infected mosquito bites on her feet. Swab specimens, taken from the chest lesions and feet, were microbiologically cultured. Staphylococcus aureus, Streptococcus pyogenes, and toxigenic Corynebacterium diphtheriae var mitis were isolated from the specimens. The 6-year-old had received flucloxacillin for 5 days before the antimicrobial agent was changed to erythromycin. She had received three primary doses of diphtheria vaccine at birth, 5 months, and 9 months, and a booster vaccination in 2001. The 12- year-old was initially treated as a contact with 7 days of erythromycin; this treatment was extended to 14 days when the laboratory confirmed C. diphtheriae infection. She had received three primary diphtheria vaccine doses in 1994, but no booster. The children’s mother had received one dose of tetanus-diphtheria (Td) toxoid in July 2002, and their father, a household contact, had no immunization record.The remaining siblings had received at least three primary doses of diphtheria vaccine, and one had received a booster. Nose and throat swabs from all six members of the family, including the two patients, were negative for C. diphtheriae. The four contacts were given antimicrobial prophylaxis and completed immunization as appropriate. The two girls were kept home from school until their antibiotic regimen was completed and clearance swabs of the lesions taken 24 hours apart were confirmed as negative.

Ribotyping, a universal molecular typing method for bacteria based upon rRNA gene restriction pattern determination, was performed on the isolates from the two siblings. The ribotype patterns produced were indistinguishable from each other. The girls’ schools were asked for lists of all children who had been in contact with the two patients to establish their diphtheria immunization status as shown on the Child Health System (a population-based register of all children living in each locality, which includes information on vaccination status and other health indices). In addition, an information letter was sent to all parents.

Patient 2

In September 2002, an 8-year-old Somalian girl, who had been in the United Kingdom for 4 months, was hospitalized with lesions on her legs and scalp, a sore throat, but no fever. She had no history of diphtheria immunization. The swabs from the throat and lesions yielded toxigenic C. diphtheriae var mitis. The organism isolated from the throat was only identified because the microbiology department screened all throat swabs routinely for corynebacteria. S. aureus was also isolated from the skin lesions. She was treated with flucloxacillin and penicillin. The skin lesions had been swabbed before September but had not been examined for C. diphtheriae. The isolates from the throat swab and the lesion were genotyped, and the ribotype patterns that resulted were identical. Two adults and five unvaccinated siblings were identified as contacts. After screening, all were negative for C. diphtheriae and were offered vaccination.

Patient 3

At the end of October 2002, an 81-year-old man returned to England from Pakistan with an infected mosquito bite. Toxigenic C. diphtheriae var mitis was isolated from the lesion. The patient received diphtheria antitoxin and was treated with erythromycin and clarithromycin for 14 days. He had no history of diphtheria immunization. He had traveled alone to Pakistan. Twelve of his close contacts in the United Kingdom required microbiologic screening, although C. diphtheriae was not isolated from any. The contacts received erythromycin prophylaxis and were offered vaccine, except for two children who had already been vaccinated. Information also was sent to the patient’s contacts in Pakistan.