title: Survival of Brucella abortus aqpX mutant in fresh and ripened cheeses.
abstract: The objective of this work was to evaluate the survival of a Brucella abortus aqpX mutant during the elaboration and conservation of fresh and ripened cheeses at 4 °C and 24 °C. The pH values and water activity were monitored for each type of cheese. The fresh cheese was elaborated with raw milk inoculated with 6×10⁸ colony-forming units (CFU)/mL each of parental and mutant strain. Ripening cheeses were elaborated with both raw and pasteurized milk and inoculated with 12×10⁸ CFU/mL each of parental and mutant strains. In fresh cheese, survival was observed during elaboration and conservation for 7 days at 4 °C in mutant and parental strains. The number of survivors of the mutant strain was 10 times lower compared with the parental strain at pH 5 and a(w) of 0.930. In the cheese elaborated with raw milk and ripened at 24 °C, both strains survived until day 17 at pH 4.0 and a(w) of 0.89. However, when the cheese was elaborated with pasteurized milk, the parental strain survived until day 31 of ripening, and the mutant strain survived 24 days at pH 4 and a(w) of 0.886. The survival of the mutant strain showed a diminution of one logarithm during elaboration and ripening of cheese as compared with the parental strain. When the cheese was elaborated with raw milk and ripened at 4 °C, survival of the parental strain was 24 days, whereas the mutant strain survived only 17 days (pH 5 and a(w) 0.90). Regarding the cheese elaborated with pasteurized milk and maturated at 4 °C, both strains survived 31 days (pH 5 and a(w) 0.90), with the same survival diminution during elaboration and ripening. Our results show that in both types of cheese, the mutated aqpX strain survived 10 times less than the parental strain, which shows that the aqpX gene can be related to the survival of Brucella abortus in this type of cheese.
authors.affiliation: 1 Centro Universitario, Universidad Autónoma del Estado de México , Zumpango, Estado de México, México .
authors.forename: María Del Rosario
authors.initials: Mdel R
authors.lastname: Santiago-Rodríguez
authors.forename: Efrén
authors.initials: E
authors.lastname: Díaz-Aparicio
authors.forename: Beatriz
authors.initials: B
authors.lastname: Arellano-Reynoso
authors.forename: Juan M
authors.initials: JM
authors.lastname: García-Lobo
authors.forename: Miquel
authors.initials: M
authors.lastname: Gimeno
authors.forename: Erika G
authors.initials: EG
authors.lastname: Palomares-Reséndiz
authors.forename: Rigoberto
authors.initials: R
authors.lastname: Hernández-Castro
mesh_terms: D000818:Animals; D020346:Aquaporins / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics*; D002003:Brucella abortus / Q000254:growth & development* / Q000302:isolation & purification / Q000378:metabolism; D002006:Brucellosis / Q000453:epidemiology / Q000382:microbiology / Q000517:prevention & control; D002611:Cheese / Q000032:analysis / Q000382:microbiology*; D003080:Cold Temperature; D015169:Colony Count, Microbial; D004032:Diet / Q000208:ethnology; D005285:Fermentation; D061353:Food Storage; D005517:Foodborne Diseases / Q000453:epidemiology / Q000382:microbiology / Q000517:prevention & control; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008800:Mexico / Q000453:epidemiology; D050296:Microbial Viability; D008892:Milk / Q000737:chemistry / Q000382:microbiology; D009154:Mutation; D061352:Pasteurization; D012306:Risk; D014867:Water / Q000032:analysis
chemical_list: C480943:AqpX protein, Brucella abortus; D020346:Aquaporins; D001426:Bacterial Proteins; D014867:Water