Cutaneous Corynebacterium diphtheriae: A traveller's disease?

A Canadian soldier incurred a nonhealing traumatic skin ulcer while on duty in Somalia. The diagnosis of localized cutaneous diphtheria was confirmed by isolation of a toxigenic strain of Corynebacterium diphtheriae from the ulcer. The patient was placed in isolation and treated with erythromycin and penicillin for 10 days without antitoxin. He was released when two consecutive daily cultures were negative. Public health officials evaluated his wife, two children and close contacts for carriage, but no carriers or secondary cases were identified. Cutaneous diphtheria as a diagnostic and management patient problem and potential public health problem are discussed.


CASE PRES EN TA TION
A 35-year-old pre vi ously healthy in fan try man pre sented with a his tory of hav ing been cut on his right shin by a gar bage can in So ma lia. The pa tient was seen by the medi cal staff in So ma lia and treated with clox a cil lin pro phy lac ti cally. On presen ta tion in Can ada two weeks later, he had a red, in flamed, punched out wound of the right shin ap proxi mately 1 cm in diame ter, with a yel low exu date. The wound was swabbed and pa tient started on oral trimethoprim-sulfamethoxazole. Toxigenic C diph the riae, bio type mi tis and Staphy lo coc cus au reus were iso lated from the wound cul ture.
The pa tient was re called and placed on con tact iso la tion in ac cor dance with pub lic health and in-hospital pro to col (4). Throat and nose swabs were taken and wound swabs were re peated. The pa tient was given peni cil lin G 1.2 MU in tra muscu larly and then eryth ro my cin 500 mg four times a day by mouth for 10 days. He was con sid ered fully im mu nized against diph the ria toxin. Wound dress ings were changed daily, and no topi cal an ti bi ot ics were ap plied. The wound was crusty but not healed when the course of an ti bi ot ics was completed. The pa tient re mained on con tact iso la tion un til cultures from the nose, throat and wound, taken on two oc ca sions 24 h af ter ces sa tion of an ti mi cro bial ther apy, were re ported as nega tive (4). Signs and symp toms of myo car di tis or neu ri tis did not ap pear. No diph the ria an ti toxin was ad minis tered. Cul tures were re peated 14 days af ter dis con tinua tion of an ti bi ot ics to rule out mi cro bio logi cal re lapse; no C diph theriae ba cilli were found.
The pa tient and his five-year-old daugh ter were up to date for diph the ria im mu ni za tion, but his wife and four-month-old child were given diph the ria toxoid boost ers. Throat swabs were taken from the im me di ate fam ily and they were started on pro phy lac tic an ti bi ot ics. Con tact trac ing was con ducted. Cul tures from all fam ily and other con tacts were nega tive.

DIS CUS SION
C diph the riae is a nonspo ru lat ing, un en cap su lated, pleomor phic Gram-positive ba cil lus (5). In the trop ics and subtropi cal cli mates cu ta ne ous diph the ria in fec tions pre vail over res pi ra tory in fec tions. En demic skin diph the ria ap pears to be re spon si ble for ac qui si tion of im mu nity in the trop ics (6). From 1921 to 1924 in fec tions due to C diph the riae have been de scribed from in di gent ur ban resi dents in Brit ish Co lum bia (7).
Cu ta ne ous diph the ria is highly con ta gious, more so than res pi ra tory diph the ria (8). Cu ta ne ous sites of C diph theriae have been shown to con tami nate the en vi ron ment and induce hu man in fec tions more ef fi ciently than pha ryn geal in fec tions (9,10). It has been shown that C diph the riae can sur vive in floor dust for at least 14 weeks (11). Com pli ca tions of C diph the riae in fec tions may af fect nerves (prin ci pally motor), the heart and kid neys (12).
Clini cal sus pi cion of cu ta ne ous diph the ria de pends on epide mi ol ogi cal and mor pho logi cal fea tures. De fini tive di ag no sis of co ry ne bac te rium in fec tions de pend on cul tur ing of or ganisms. When any case of diph the ria is di ag nosed, con trol meas ures should in clude a search for cu ta ne ous C diph the -riae (10). Be sides iso la tion and strict bed rest, the only specific treat ment of co ry ne bacte rium in fec tions is the ad mini stra tion of an ti toxin to C diph the riae (13).
An ti bi ot ics do not al ter the course, in ci dence of com pli cations or out come of the in fec tion (12). How ever, an ti bi ot ics are bene fi cial be cause they elimi nate the car rier state, ter mi nate toxin pro duc tion and ame lio rate lo cal in fec tions (5). In light of the ab sence of toxic symp toms such as myo car di tis and polyneu ri tis, and be cause the pa tient was up to date for im mu niza tion, he was not given an ti toxin af ter a lo cal in fec tious dis ease spe cial ist was con sulted. The risk of com pli ca tions is much lower in im mu nized pa tients. Po ten tial sys temic com plica tions of cu ta ne ous diph the ria must be weighed against poten tial ad verse ef fects of an ti toxin treat ment (14). Spon ta ne ous heal ing of the wound takes six to 12 weeks, but cases last ing one year have been ob served (8).
Al though cu ta ne ous diph the ria is only a medi cal cu ri os ity in North Amer ica, pri mary care phy si cians and spe cial ists should place C diph the riae on their dif fer en tial di ag no sis of a pa tient who pres ents with a non heal ing punched out ul cer with slightly ele vated mar gin and a his tory of re cent travel to the trop ics. Swab bing of the le sion is es sen tial. If di ag no sis is con firmed by cul ture, the pa tient should be placed on con tact iso la tion and given an ti bi ot ics; oral eryth ro my cin or peni cil lin G in tra mus cu larly are the an ti bi ot ics of choice (4). The pa tient should be moni tored for toxic com pli ca tions, es pe cially myocar di tis and poly neu ri tis. Elec tro car dio gram and neu ro logi cal ex ami na tions should be per formed. Toxi genic C diph the riae is a ma jor pub lic health haz ard, and the pa tient with C diph theriae can be a res er voir for an epi demic (10). Therefore, no ti fi ca tion of pub lic health authori ties is es sen tial.