Community-acquired bacteremic Achromobacter xylosoxidans type IIIa pneumonia in a patient with idiopathic IgM deficiency.

A man was hospitalized with bacteremic Achromobacter xylosoxidans type IIIa pneumonia. The authors are aware of no previously reported similar infections caused by this bacterium. A clinical cure was achieved with a combination of carbenicillin and kanamycin therapy. Microtiter susceptibility testing revealed that carbenicillin was the antibiotic to which A. xylosoxidans IIIa was most sensitive (minimal inhibitory concentration, 1.6 microgram/ml) and that synergy between carbenicillin and kanamycin existed. During the patient's hospitalization, deficiency of IgM (21 mg/dl) was found. Specific serum activity against A. xylosoxidans IIIa was detected by the agglutination method. Specific anti-A. xylosoxidans IIIa IgG, but not IgM, was detected by indirect immunofluorescence. It appears that a defect in immunologic recognition of A. xylosoxidans IIIa as an invasive bacterium, a defect in synthesis of specific IgM, or both, contributed to this patient's infection.