Abstract
A hemin-requiring Pseudomonas aeruginosa small-colony variant (SCV) was isolated from the blood of a patient with double pneumonia. The isolate was capable of growing on both blood and chocolate agar plates but not on MacConkey agar plates without blood. Furthermore, the isolate failed to grow on triple-sugar iron agars. The microscopic morphology of the isolate was similar to that of Haemophilus species. When examined the auxotrophy using X-factor (hemin)- and V-factor (NAD)-impregnated discs on the Mueller-Hinton agar plate, the isolate grew only around the X-factor (hemin)-impregnated disc. However, when using the VITEK2 system, the isolate was identified as Acinetobacter lwoffii. The isolate was finally identified as P. aeruginosa by 16S rRNA gene sequencing and MALDI-TOF MS analysis. SCV phenotypes are related to persistent and recurrent infections. Moreover, it is difficult to identify SCVs because of their atypical colony morphology and altered biochemical profile. The accurate identification of SCVs is important for effective antimicrobial treatment. To the best of our knowledge, this is the first clinical isolation of a hemin-dependent P. aeruginosa SCV.
