Heat-resistant and biofilm-forming Escherichia coli in pasteurized milk from Brazil.

Escherichia coli harboring a transmissible locus of stress tolerance (tLST) and the ability to form biofilms represent a serious risk in dairy production. Thus, we aimed to evaluate the microbiological quality of pasteurized milk from two dairy producers in Mato Grosso, Brazil, with a focus on determining the possible presence of E. coli with heat resistance (60 °C/6 min), biofilm-forming potential phenotypes and genotypes, and antimicrobial susceptibility. For this, fifty pasteurized milk samples from producers named A and B were obtained for 5 weeks to investigate the presence of Enterobacteriaceae members, coliforms, and E. coli. For heat resistance, E. coli isolates were exposed to a water bath at 60 °C for 0 and 6 min. In antibiogram analysis, eight antibiotics belonging to six antimicrobial classes were analyzed. The potential to form biofilms was quantified at 570 nm, and curli expression by Congo Red was analyzed. To determine the genotypic profile, we performed PCR for the tLST and rpoS genes, and pulsed-field gel electrophoresis (PFGE) was used to investigate the clonal profile of the isolates. Thus, producer A presented unsatisfactory microbiological conditions regarding Enterobacteriaceae and coliforms for weeks 4 and 5, while all samples analyzed for producer B were contaminated at above-the-limit levels established by national and international legislation. These unsatisfactory conditions enabled us to isolate 31 E. coli from both producers (7 isolates from producer A and 24 isolates from producer B). In this way, 6 E. coli isolates (5 from producer A and 1 from producer B) were highly heat resistant. However, although only 6 E. coli showed a highly heat-resistant profile, 97% (30/31) of all E. coli were tLST-positive. In contrast, all isolates were sensitive to all antimicrobials tested. In addition, moderate or weak biofilm potential was verified in 51.6% (16/31), and the expression of curli and presence of rpoS was not always related to this biofilm potential. Therefore, the results emphasize the spreading of heat-resistant E. coli with tLST in both producers and indicate the biofilm as a possible source of contamination during milk pasteurization. However, the possibility of E. coli producing biofilm and surviving pasteurization temperatures cannot be ruled out, and this should be investigated.

Genomic features and heat resistance profiles of Escherichia coli isolated from Brazilian beef.

AIMS: Characterize Escherichia coli and E. coli -producing (STEC) isolates from Brazilian beef to determine heat resistance and the presence of the transmissible locus of stress tolerance (tLST). METHODS AND RESULTS: Twenty-two STEC previously isolated from beef and characterized as STEC by PCR were subjected to different heat survival challenges (60°C and 71°C). Furthermore, the three tLST-positive isolates and one tLST-negative isolate by PCR were selected for WGS analysis. Phenotypic results indicated that 3/22 (13.64%) were heat resistant, 12/22 (54.54%) were moderately resistant, and 7/22 (31.82%) were sensitive to heat treatments. WGS analyses showed that three isolates with heat resistance showed tLST with up to 80% and 42% of similarity by BLAST analysis, with the major tLST genes being responsible for the homeostasis module. However, WGS showed the absence of stx genes associated with tLST-positive isolates, albeit with virulence and resistance genes found in extraintestinal pathogenic E. coli (ExPEC). CONCLUSION: Our findings demonstrate the presence of heat-resistant E. coli as well as confirm some tLST genes in E. coli isolated from Brazilian beef.

Listeria monocytogenes and Pseudomonas spp. Distribution in a Processing Facility of Spotted Sorubim (Pseudoplatystoma corruscans) in Brazil.

ABSTRACT: The ecology of Listeria monocytogenes and Pseudomonas spp. during the slaughtering of spotted sorubim (Pseudoplatystoma corruscans) in a fish processing facility was assessed. Fish samples (n = 28) were obtained in different points of slaughtering (A, arrival; B, washing; C, gutting; and D, cooling) and subjected to detection of L. monocytogenes and enumeration of Pseudomonas spp. High frequencies of Listeria spp. (17 of 28 to 22 of 28) and L. monocytogenes (6 of 28 to 9 of 28) were identified in all slaughtering points but were not significantly different (P ≥ 0.05). All L. monocytogenes isolates (n = 33) were identified as belonging to serogroup IVb (serotype 4b) and subjected to macrorestriction with ApaI and AscI. The results indicated a continuous entry of L. monocytogenes in the facility, as well as a temporary persistence of a specific pulsotype. Pseudomonas spp. counts significantly decreased between points A and D (P < 0.05), but the mean counts in the end products (D) remained higher than 3 log CFU/g, suggesting the potential for fast spoilage. The obtained results show that L. monocytogenes and Pseudomonas spp. are widely distributed during spotted sorubim slaughtering, indicating the need for proper hygienic procedures to control these bacteria in the processing facility.