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Updated: Aug 10, 2026

Identification of Rare Bacterial Pathogens by 16S rRNA Gene Sequencing and MALDI-TOF MS
Published on: July 11, 2016
Identification of biochemically atypical Staphylococcus aureus clinical isolates with three automated identification
Yoshikazu Ishii1, Jimena Alba1, Chikako Maehara2
1Department of Microbiology and Infectious Diseases, Toho University School of Medicine, 5-21-16 Omori-nishi, Ota-ku, Tokyo 1438540, Japan.
Abstract:
Between January and April 2002, a total of 271 strains of Staphylococcus aureus were isolated from clinical specimens at Toho University Omori Hospital, Japan, including 201 (74.2 %) which were identified as meticillin-resistant S. aureus (MRSA). However, 34 (12.5 %) were biochemically atypical, because they did not produce acid on mannitol salt agar or did not agglutinate in Staphaurex testing but were categorized as MRSA by PCR analysis and by antibiotic susceptibility. Three automatic identification systems, AutoScan-4 (Dade Behring), BD Phoenix (Becton Dickinson) and Vitek 2 (bioMérieux), were evaluated by testing these atypical S. aureus isolates. The AutoScan-4 and Phoenix systems identified all 34 isolates as S. aureus. Without additional tests such as Staphaurex, observation of colony pigment and haemolysins on sheep blood agar, Vitek 2 identified only 16 isolates (47.1 %) as S. aureus with good or better confidence levels and misidentified one of the remaining isolates as Staphylococcus chromogenes. This study shows that it is possible to identify these physiologically atypical S. aureus isolates correctly by using the Phoenix and AutoScan-4 fully automatic identification systems.
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