MALDI-TOF mass spectrometry speciation of staphylococci and their discrimination from micrococci isolated from indoor air of schoolrooms

Abstract

The focus of our work is the identification of medically relevant staphylococci from the environment; these organisms are among the major opportunistic pathogens associated with human disease. Andersen sampling was performed in schoolrooms during the school year. Eleven of thirty six isolates (all Gram-positive tetrads) were identified as staphylococci and 23 were characterized as micrococci. MALDI-TOF MS profiling was used as the first stage in the classification followed by standard biochemical tests including API Staph profiling. The staphylococcal isolates were each speciated; coagulase positive (Staphylococcus aureus [3 strains]) and coagulase negative: Staphylococcus warneri (4 isolates), Staphylococcus hominis (2), Staphylococcus saprophyticus (1) and Staphylococcus cohnii (1). S. aureus is most commonly found in the human nares but is frequently isolated from skin. The other staphylococcal species are among those most commonly isolated from human skin. Micrococci were much more frequently isolated from indoor air than reported by others for clinical samples. It is suggested that, without discrimination from micrococci, misidentification of staphylococci would be common on air sampling.

Indoor Air Quality in Brazilian Universities

“…Investigators have previously noted the significant content of desquamated human skin cells in aerosols in occupied settings and the presence of bacteria including Staphylococcus , Propionibacteria , Corynebacteria , and enteric bacteria, which are typically ascribed to human microflora [30,31]. A survey in three university laboratories in Italy discovered that the most frequently observed bacteria were Staphylococcus , Bacillus , and Actinomyces [32]. The fungi most commonly found indoors were Alternaria spp., Aspergillus spp., and Cladosporium spp.…”

Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry: a Fundamental Shift in the Routine Practice of Clinical Microbiology

“…are able to be reliably identified by using the BioTyper software. In a study of environmental micrococci, isolates were identified correctly to the genus level, but no species-level identification could be reached due to limited entries in the database (94). It is likely that with the appropriate database, specieslevel discriminations could be made when necessary.…”

Identification of Staphylococcus saprophyticus isolated from patients with urinary tract infection using a simple set of biochemical tests correlating with 16S–23S interspace region molecular weight patterns

“…In these cases, ITR-PCR can be used to identify rare phenotypes and aberrant species. Although ITR-PCR has some limitations in the identification of certain closely related species (Fox et al, 2010), the S. saprophyticus isolates exhibited a unique band pattern. In addition, other species which are difficult to differentiate from S. saprophyticus by ITR-PCR, such as Staphylococcus chromogenes, Staphylococcus cohnii, Staphylococcus equorum, Staphylococcus gallinarum, Staphylococcus lentus, and Staphylococcus xylosus (Couto et al, 2001), were not detected in this study and are usually not associated with UTI in humans.…”