Arcanobacterium haemolyticum, clinical, diagnostic and therapeutic aspects

Sammanfattning: In an 18-month period all throat cultures in our laboratory were examined for Arcanobacterium haemolyticum and clinical information was obtained. The great majority of the patients suffered from pharyngitis or tonsillitis, accompanied by a rash in 46% of cases. One third of the patients had a history of recurrent tonsillitis. Three types of exanthema was described, scarlatiniform, urticarial and erythema multiforme. Ten percent of the patients had exanthema without throat symptoms. After penicillin therapy, the patients still harbored the bacterium, whereas erythromycin eradicated it from the pharynx. A. haemolyticum was found to be tolerant (i.e. normal MICs but high MBCs) to penicillin, using 4 different test methods, a finding which is consistent with the persistence of A. haemolyticum in the pharynx after penicillin treatment. Owing to its eradicating capability and low MIC values, erythromycin is the drug of choice for treating A. haemolyticum pharyngitis. Other antibiotics with favorable MIC values were roxithromycin, clarithromycin, azithromycin, clindamycin, doxycycline, and fucidic acid. In Western blot studies 7 of 8 patients manifested an antibody rise in convalescent sera, as compared to their acute sera, and 19 single convalescent sera from A. haemolyticum patients showed a highly significant difference in antibodies, as compared to sera of matched healthy control persons (p<0.005). Antibodies to proteins with molecular masses of 80, 60 and 30 k were most common. Due to pronounced hemolysis, A. haemolyticum is most easily isolated on human blood agar plates, if the investigator is unfamiliar with the morphology. One hundred strains with typical morphology, a typical Gram-stained smear, and inhibition of S. aureus ß-hemolysin, proved to be biochemically homogenous, indicating that these criteria were satisfactory for identifying A. haemolyticum in the clinical microbiology laboratory.