RESUMO
Recent food listeriosis outbreaks confirm that more faithful isolation and identification methods for Listeria monocytogenes or other potentially pathogen microorganisms are required. Furthermore, the human and animal reservoir role in the ecology of this disease must be established. Listeria spp. in the vizcacha intestinal content was determined by two isolation procedures, starting from 10 g of homogenized samples in 40 ml of PBS. I)0.1 ml was stripped on phenylethanol agar, selective agar for Listeria and acryflavin ceftazidin agar, then incubated at 37 degrees C for 48 h, suspected colonies were identified by preliminary tests (Gram, hemolysis, catalase, esculin hydrolisis and motility at 22 degrees C) and confirmatory tests (indol, methyl red, Voges Proskauer, nitrate and carbohydrate fermentation) (Table 1). Antibiotic susceptibility, protein profile by PAGE and pathogenic power in mice were determined. II) The remaining homogenate was incubated at 4 degrees C in 100 ml of Donnelly and Baigent enrichment broth, weekly or monthly with subcultures until 30 days or 6-8 months, respectively. The subcultures were followed up as in I). A L. seeligeri strain, susceptible to antibiotics suggested for L. monocytogenes and exhibiting resistance to some second and third generation cephalosporins, was isolated (Table 2). The protein profile of both species was coincident, but L. seeligeri was not virulent for mice. The finding of L. seeligeri in an animal (4.0%) used as human feeding source is of interest due to its potential pathogen power.
Assuntos
Ceco/microbiologia , Listeria/isolamento & purificação , Nephropidae/microbiologia , Animais , Listeria/efeitos dos fármacos , Testes de Sensibilidade MicrobianaRESUMO
Recent food listeriosis outbreaks confirm that more faithful isolation and identification methods for Listeria monocytogenes or other potentially pathogen microorganisms are required. Furthermore, the human and animal reservoir role in the ecology of this disease must be established. Listeria spp. in the vizcacha intestinal content was determined by two isolation procedures, starting from 10 g of homogenized samples in 40 ml of PBS. I)0.1 ml was stripped on phenylethanol agar, selective agar for Listeria and acryflavin ceftazidin agar, then incubated at 37 degrees C for 48 h, suspected colonies were identified by preliminary tests (Gram, hemolysis, catalase, esculin hydrolisis and motility at 22 degrees C) and confirmatory tests (indol, methyl red, Voges Proskauer, nitrate and carbohydrate fermentation) (Table 1). Antibiotic susceptibility, protein profile by PAGE and pathogenic power in mice were determined. II) The remaining homogenate was incubated at 4 degrees C in 100 ml of Donnelly and Baigent enrichment broth, weekly or monthly with subcultures until 30 days or 6-8 months, respectively. The subcultures were followed up as in I). A L. seeligeri strain, susceptible to antibiotics suggested for L. monocytogenes and exhibiting resistance to some second and third generation cephalosporins, was isolated (Table 2). The protein profile of both species was coincident, but L. seeligeri was not virulent for mice. The finding of L. seeligeri in an animal (4.0
) used as human feeding source is of interest due to its potential pathogen power.
RESUMO
Recent food listeriosis outbreaks confirm that more faithful isolation and identification methods for Listeria monocytogenes or other potentially pathogen microorganisms are required. Furthermore, the human and animal reservoir role in the ecology of this disease must be established. Listeria spp. in the vizcacha intestinal content was determined by two isolation procedures, starting from 10 g of homogenized samples in 40 ml of PBS. I)0.1 ml was stripped on phenylethanol agar, selective agar for Listeria and acryflavin ceftazidin agar, then incubated at 37 degrees C for 48 h, suspected colonies were identified by preliminary tests (Gram, hemolysis, catalase, esculin hydrolisis and motility at 22 degrees C) and confirmatory tests (indol, methyl red, Voges Proskauer, nitrate and carbohydrate fermentation) (Table 1). Antibiotic susceptibility, protein profile by PAGE and pathogenic power in mice were determined. II) The remaining homogenate was incubated at 4 degrees C in 100 ml of Donnelly and Baigent enrichment broth, weekly or monthly with subcultures until 30 days or 6-8 months, respectively. The subcultures were followed up as in I). A L. seeligeri strain, susceptible to antibiotics suggested for L. monocytogenes and exhibiting resistance to some second and third generation cephalosporins, was isolated (Table 2). The protein profile of both species was coincident, but L. seeligeri was not virulent for mice. The finding of L. seeligeri in an animal (4.0
) used as human feeding source is of interest due to its potential pathogen power.
RESUMO
Jones and Seeliger with the endorsement of the International Committee on Systematic Bacteriology, Subcommittee on the Taxonomy of Listeria, are considering to replace L. monocytogenes ATCC 15313 as prototype strain of species because of the lack of hemolytic activity in conventional agar blood media. We demonstrate in this work that ATCC 15313 strain is able to induce hemolysis in conventional media under microaerophilic conditions and also has a definite hemolytic activity when supernatants of a 24 hs growth in brain heart infusion plus 0.5% dextrose were activated with 2-mercaptoethanol (Table 3). Thirteen strains previously identified as L. monocytogenes were studied. Nine of them are compatible with the identification of L. monocytogenes, all show hemolytic activity under microaerophilic conditions, ATCC 15313 does nos show hemolysis on surface test but induces hemolysis, as other nine strains do, when activated by 2-mercaptoethanol. It is interesting to reinforce the need to perform all the different test to analyze hemolytic activity as a basis for presumptive L. monocytogenes identification. The absence of demonstrable hemolysis using all proposed test is an important factor to be taken into account for Listeria identification.
Assuntos
Proteínas Hemolisinas/análise , Listeria monocytogenes/classificação , Mercaptoetanol , Meios de Cultura , Listeria monocytogenes/análiseRESUMO
Jones and Seeliger with the endorsement of the International Committee on Systematic Bacteriology, Subcommittee on the Taxonomy of Listeria, are considering to replace L. monocytogenes ATCC 15313 as prototype strain of species because of the lack of hemolytic activity in conventional agar blood media. We demonstrate in this work that ATCC 15313 strain is able to induce hemolysis in conventional media under microaerophilic conditions and also has a definite hemolytic activity when supernatants of a 24 hs growth in brain heart infusion plus 0.5
dextrose were activated with 2-mercaptoethanol (Table 3). Thirteen strains previously identified as L. monocytogenes were studied. Nine of them are compatible with the identification of L. monocytogenes, all show hemolytic activity under microaerophilic conditions, ATCC 15313 does nos show hemolysis on surface test but induces hemolysis, as other nine strains do, when activated by 2-mercaptoethanol. It is interesting to reinforce the need to perform all the different test to analyze hemolytic activity as a basis for presumptive L. monocytogenes identification. The absence of demonstrable hemolysis using all proposed test is an important factor to be taken into account for Listeria identification.