Actinobaculum schaalii infections: clinical relevance, identification and antibiotic susceptibility

Abstract number: 1134_04_181

Reinhard M., Prag J., Kemp M., Andresen K., Klemmensen B., Højlyng N., Sørensen S.H., Christensen J.J.

Objectives:  

Genus Actinobaculum is an example of clinical important organisms that recently have been separated from a large group of poorly-defined Gram-positive rods. We here describe the clinical pictures and bacteriologic characteristics in 9 cases of Actinobaculum schaalii infections.

Methods:  

Data were collected from the clinical records. Eight strains of A. schaalii were available for phenotypic and molecular characterization. From one patient presence of DNA from A. schalii was demonstrated in pus from kidney cysts, but without bacterial growth. The strains were characterized by conventional methods, API Coryne and API Rapid ID 32A. For molecular analysis, DNA was extracted from strains and analysed by real-time PCR of part of the 16SrRNA gene (526-bp fragment). Amplicons produced were DNA sequenced and a BLAST search in the NCBI GenBank was done. Obtained results were compared.

Results:  

Nine strains of A. schaalii were identified in three Danish departments of clinical microbiology. Six strains of A. schaalii were from one department of clinical microbiology covering 230,000 persons and collected over a period of six months. Except for one case the urinary tract was suspected as the focus of the infection. These eight patients were elderly and predisposed to urinary tract infections (UTI) because of either urinary tract or neurological diseases. A. schaalii was isolated from the blood in three cases, from the urine in six cases, from kidney cysts in one case and from an intradural abscess in one case. All patients received antibiotics and recovered from their infection. The strains were identified with 16S rRNA gene sequence analysis, but identification with the API Coryne and the Rapid ID32A test systems is also possible although the numerical codes are not yet registered in the manufacturer's database. The isolates were susceptible to a wide range of antibiotics, including b-lactam agents and showed little inter-isolate variability.

Conclusion:  

A. schaalii causes UTI and search for it is especially relevant in cases of unexplained pyuria, especially when there is divergence between the microscopic findings and the growth results under aerobic conditions. Samples, then, should be cultured on appropriate media and incubated in an anaerobic atmosphere. A. schaalii is easily overlooked as isolation of the organism requires 24 to 48 h of incubation in an anaerobic or CO₂ enriched atmosphere and even then is easily disregarded as a contaminant.