A paediatric case of lymphadenitis by toxigenic Corynebacterium ulcerans

Case presentation: A 6-year-old Japanese girl who had been vaccinated using diphtheria toxoid presented with fever and swelling in the left neck. Ultrasonography showed cervical lymphadenitis with cellulitis. C. ulcerans was isolated from the drainage specimen. The infection was cured with erythromycin administration. Her anti-diphtheria toxoid antibody level was at an adequate level for diphtheria prevention on admission and was significantly increased 3 weeks later. Zoonotic infection was considered likely, because a family cat had shown rhinitis and skin ulcers prior to symptom onset in the child.


Introduction
Corynebacterium ulcerans was first isolated from the throat of a patient with respiratory diphtheria-like illness in 1926 (Gilbert & Stewart, 1926).C. ulcerans produces diphtheria toxin and causes various symptoms such as classic respiratory Corynebacterium diphtheria-like symptoms, dermatitis and lymphadenitis.Respiratory diphtheria-like illness is a serious disease characterized by pseudomembrane formation and frequent cardiac or neurological sequelae.This condition requires urgent treatment with diphtheria antitoxin and antibiotics.On the other hand, lymphadenitis by C. ulcerans is curable by antibiotics and drainage (Urakawa et al., 2013).C. ulcerans is a zoonotic agent that infects humans drinking unpasteurized milk or in close contact with infected dogs, cats or various other animal species (Vandentorren et al., 2014).Thirteen cases of adult C. ulcerans infection have been reported in Japan (Yoshimura et al., 2014).To the best of our knowledge, this case represents the first report of paediatric C. ulcerans in Japan.

Case report
A 6-year-old Japanese girl was admitted to our hospital with a 2-day history of fever and swelling of the left neck.Her past medical history was unremarkable, and she had no history of travel to a foreign country.She had received routine diphtheria vaccinations four times over 5 years prior to this illness.
Physical examination revealed an axillary temperature of 38.4 uC and a painful erythematous mass in the left neck.No scratches were evident.The mass was approximately 5|2 cm in size and hard.The pharynx appeared normal.Blood examination showed: white blood cell count, 12 400 ml 21 ; neutrophils, 73 %; lymphocytes, 17 %; and C-reactive protein, 2.3 mg dl 21 .Ultrasonography showed lymphadenitis with cellulitis (Fig. 1).
Fever subsided the next day after starting administration of sulbactam/ampicillin, but the mass enlarged and became extremely tender.On hospital day 4, needle drainage was performed.Culture of the drained pus revealed Grampositive bacilli.After drainage, the painful mass gradually reduced in size.On hospital day 6, the patient was discharged with administration of oral sultamicillin.Four days later, the left neck mass recurred.Needle drainage was again performed, but no organisms were cultured.C. ulcerans was isolated from the initial sample at this time.Antimicrobial susceptibility testing showed that the strain was susceptible to ampicillin, penicillin G, erythromycin and minocycline.We treated the patient with oral azithromycin for 3 days, followed by erythromycin for 10 days.At follow-up after 1 month, the mass had completely disappeared and did not recur.The isolates were identified as toxigenic C. ulcerans by biochemical differentiation as follows.Biotyping was performed using the API CORYNE system (SYSMEX bioMe ´rieux).Diphtheria toxin production was confirmed by a modified Elek test (Engler et al., 1997) and Vero cell cytotoxicity tests (Miyamura et al., 1974).The antidiphtheria toxoid antibody level was 0.757 IU ml 21 at onset, increasing to 6.05 IU ml 21 after 3 weeks.
The family cat had shown eye discharge, sneezing and skin ulcers before the onset of symptoms in the patient.Unfortunately, C. ulcerans was not able to be grown from swabs of the bulbar conjunctiva, pharynx or skin of the domestic cat, probably because antibiotics had been administered prior to specimen collection.
All other members of the patient's immediate family had been immunized with diphtheria toxoid vaccine (DT) four times and showed no symptoms.Cultures of throat swab specimens from family members all showed negative results.DT was provided for the patient's mother, because her anti-diphtheria toxoid antibody level was significantly below the protective level of w0.1 IU ml 21 .

Discussion
Reports of C. ulcerans infection have markedly increased in recent years (Wagner et al., 2012).Most cases have involved older adults who were not up to date with immunization against C. diphtheriae.Paediatric cases of C. ulcerans infection are extremely rare, because children generally receive a routine series of DT injections.To the best of our knowledge, only four paediatric cases of C. ulcerans have been described in the literature (Table 1).Unfortunately, detailed descriptions about immunization histories and levels of anti-diphtheria toxoid antibody have been lacking (Hart, 1984;Pers, 1987;Kisely et al., 1994;Public Health England, 2000).Illness occurred in our patient despite the presence of what was considered an adequately protective level of anti-diphtheria toxoid antibody (w0.1 U ml 21 ), although symptoms were mild and pseudomembrane formation was not observed.C. ulcerans initially infects the throat, and the colonized bacteria subsequently produce diphtheria toxin and form a pseudomembrane that causes serious dyspnoea.Acquired anti-diphtheria toxoid antibody might be helpful in preventing formation of the pseudomembrane but may not prevent invasion through cervical lymphadenitis from the throat via the blood or lymphangion to allow early colonization by C. ulcerans.Furthermore, we have suggested the possibility of a partial immunity response due to differences between the DT produced by C. diphtheriae and some C. ulcerans strains (Sing et al., 2005).
We should consider C. ulcerans as prevalent among animals (Katsukawa et al., 2012;Hirai-Yuki et al., 2013).It has been reported previously by Shimono et al. (2012) that surveillance of cats in Tokushima Prefecture, where the patient lives, found C. ulcerans colonizing 4.2 %, and anti-diphtheria toxin antibody was present in 10.5 % of cats.We recommend that pet owners wash their hands after touching animals, and wear a mask and gloves if the animal shows signs of illness.In conclusion, we suggest that, while DT immunization might be effective in preventing severe respiratory disease caused by C. ulcerans, lymphadenitis may occur in children despite DT vaccination and having protective antibody titres because DT vaccination does not prevent colonization by corynebacteria.Close contact with sick animals should be avoided whenever possible.

Fig. 1 .
Fig. 1.Ultrasonography showing an unclear boundary and hypoechoic lymph with a maximal size of 967 mm.Blood flow is observed in the lymph nodes.The surrounding subcutaneous tissue appears hyperechoic.

Table 1 .
Paediatric cases of C. ulcerans infection