Interference of raw milk autochthonous microbiota on the performance of conventional methodologies for Listeria monocytogenes and Salmonella spp. detection.
Pathogen detection in foods by reliable methodologies is very important to guarantee microbiological safety. However, peculiar characteristics of certain foods, such as autochthonous microbiota, can directly influence pathogen development and detection. With the objective of verifying the performance of the official analytical methodologies for the isolation of Listeria monocytogenes and Salmonella in milk, different concentrations of these pathogens were inoculated in raw milk treatments with different levels of mesophilic aerobes, and then submitted to the traditional isolation procedures for the inoculated pathogens. Listeria monocytogenes was inoculated at the range of 0.2-5.2 log CFU/mL in treatments with 1.8-8.2 log CFU/mL. Salmonella Enteritidis was inoculated at 0.9-3.9 log CFU/mL in treatments with 3.0-8.2logCFU/mL. The results indicated that recovery was not possible or was more difficult in the treatments with high counts of mesophilic aerobes and low levels of the pathogens, indicating interference of raw milk autochthonous microbiota. This interference was more evident for L. monocytogenes, once the pathogen recovery was not possible in treatments with mesophilic aerobes up to 4.0 log CFU/mL and inoculum under 2.0 log CFU/mL. For S. Enteritidis the interference appeared to be more non-specific.
Nero
Luís Augusto
LA
Universidade Federal de Viçosa, Departamento de Veterinária, Av. P.H. Rolfs s/n, Centro, 36570 000 Viçosa, MG, Brazil. nero@ufv.br
de Mattos
Marcos Rodrigues
MR
Barros
Márcia de Aguiar Ferreira
Mde A
Beloti
Vanerli
V
Franco
Bernadette Dora Gombossy de Melo
BD
D000818:Animals; D001419:Bacteria / Q000302:isolation & purification; D002417:Cattle; D015169:Colony Count, Microbial / Q000379:methods*; D008089:Listeria monocytogenes / Q000302:isolation & purification*; D008892:Milk / Q000382:microbiology*; D012475:Salmonella / Q000302:isolation & purification*; D012477:Salmonella enteritidis / Q000302:isolation & purification*