PMC3320481_01
Sheep blood agar plates (A-E) and magnified sectors (a-e) after overnight incubation at 37 C showing different morphotypes of clonal isolates of the Staphylococcus lugdunensis strain recovered from blood cultures and the infected pocket of a patient with pacemaker infection. Plates A-D/a-d show S. lugdunensis colonies exhibiting the normal phenotype characterized by colonies of different diameter, ranging from 0.8 to 2.5 mm with creamy (A/a) or yellow (B-D/b-d) pigmentation and moderately heavy (B/b), weak (C-D/c-d), or absent (A/a) hemolysis; plate E/e shows the small-colony variant phenotype characterized by tiny (pinpoint), nonpigmented, and nonhemolytic colonies.
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F1
During a transient febrile episode, a blood culture was obtained that again yielded S. lugdunensis (Figure 1A). The results of subcultures on solid media suggested a mixed population of staphylococci, with at least 4 different colony morphologies (Figure 1B-E). The large hemolytic morphotype (Figure 1B) showed a profile consistent with S. lugdunensis, with positive results for ornithine decarboxylase, trehalose, and l-pyrrolidonyl-beta-naphthylamide. The S. lugdunensis isolate that grew as tiny (pinpoint), nonpigmented, and nonhemolytic colonies was shown to be a hemin-auxotrophic SCV (Figure 1E). The S. lugdunensis isolate (large colony morphotype) was susceptible to all antimicrobial agents in the VITEK GPS-P526 card test (bioMerieux) and did not produce beta-lactamase. The other morphotypes did not grow sufficiently to allow antimicrobial susceptibility testing with the VITEK system. API ID 32 Staph system (bioMerieux) identified all morphotypes as S. lugdunensis, which was later confirmed by 16S ribosomal RNA gene sequencing using the RIDOM entries. All isolates, including an additional S. lugdunensis blood isolate obtained in February 2003 that produced flat, white, and nonhemolytic colonies (Figure 1A), were compared by pulsed-field gel electrophoresis and found to be identical, although the colony morphology was different (Figure 2).
Fingerprint patterns for different Staphylococcus lugdunensis colony morphotypes, including small-colony variants (SCVs), after pulsed-field gel electrophoresis after digestion with SmaI, showing identical isolates. Lanes 1 and 7, 100-bp ladder; lane 2, blood isolate; lanes 3-5, colony variants; lane 6, SCVs of S. lugdunensis obtained from thrombotic material.
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F2
API ID 32 Staph system (bioMerieux) identified all morphotypes as S. lugdunensis, which was later confirmed by 16S ribosomal RNA gene sequencing using the RIDOM entries. All isolates, including an additional S. lugdunensis blood isolate obtained in February 2003 that produced flat, white, and nonhemolytic colonies (Figure 1A), were compared by pulsed-field gel electrophoresis and found to be identical, although the colony morphology was different (Figure 2).