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Updated: Jan 9, 2026
Capsular Serotyping of Streptococcus pneumoniae by Latex Agglutination
Published on: September 25, 2014
False positive results obtained with latex agglutination identification of Staphylococcus aureus caused by
Magdalena Kizerwetter-Świda1, Monika Garbowska2, Ilona Stefańska3
1Department of Preclinical Sciences, Institute of Veterinary Medicine, Warsaw University of Life Sciences-SGGW, Ciszewskiego Str. 8, 02-786, Warsaw, Poland. magdalena_kizerwetter_swida@sggw.edu.pl.
Abstract:
Reliable and rapid identification of Staphylococcus aureus constitutes a critical issue in food safety. A total of 180 meat samples were analysed, and 30 isolates that phenotypically matched S. aureus were obtained. All 30 isolates generated positive results in agglutination with the SlidexStaph test. The results of agglutination were verified with the matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF MS) method, S. aureus-specific PCR and sequencing of the 16 S rRNA genes. Among 30 isolates positive in the SlidexStaph test, 17 were finally identified as S. aureus, eight as Macrococcus caseolyticus, four as Mammaliicoccus fleurettii (previously Staphylococcus fleurettii), and one single isolate as Staphylococcus pseudintermedius. In this study, we have demonstrated for the first time false-positive results of the rapid identification based on S. aureus-specific agglutination obtained for M. fleurettii. Antimicrobial resistance testing revealed a considerable prevalence of multidrug resistance among M. caseolyticus (100%) and M. fleurettii (50%). This study highlights the possibility of obtaining false-positive results in agglutination tests with M. caseolyticus and M. fleurettii. Furthermore, the presence of multidrug-resistant M. caseolyticus and M. fleurettii in meat samples may contribute to the spread of microbial drug resistance and requires further investigation.
Insights
Rapid identification tests for Staphylococcus aureus in food can yield false positives. This study found that Macrococcus caseolyticus and Mammaliicoccus fleurettii can be misidentified, highlighting the need for confirmatory methods.
Area of Science:
- Food Safety
- Microbiology
- Diagnostic Testing
Background:
- Accurate identification of Staphylococcus aureus is crucial for food safety.
- Phenotypic methods are often used for initial screening of bacterial isolates.
Purpose of the Study:
- To evaluate the accuracy of a rapid agglutination test for Staphylococcus aureus identification.
- To investigate the prevalence of misidentified species and their antimicrobial resistance profiles.
Main Methods:
- Analysis of 180 meat samples yielded 30 suspected S. aureus isolates.
- Agglutination testing (SlidexStaph) followed by MALDI-TOF MS, PCR, and 16S rRNA gene sequencing.
- Antimicrobial resistance testing was performed on identified isolates.
Main Results:
- Out of 30 isolates, only 17 were confirmed as S. aureus.
- Eight isolates were identified as Macrococcus caseolyticus, four as Mammaliicoccus fleurettii, and one as Staphylococcus pseudintermedius.
- False-positive agglutination results were observed for M. fleurettii, and M. caseolyticus also showed potential for false positives.
Conclusions:
- The SlidexStaph agglutination test can produce false-positive results for M. fleurettii and potentially M. caseolyticus.
- High rates of multidrug resistance were found in M. caseolyticus (100%) and M. fleurettii (50%).
- The presence of multidrug-resistant non-aureus staphylococci in meat poses a risk for antimicrobial resistance spread.
