Molecular and Phenotypic Characterization of Pseudomonas spp. Isolated from Milk

Abstract

Putative Pseudomonas spp. isolated predominantly from raw and processed milk were characterized by automated ribotyping and by biochemical reactions. Isolates were biochemically profiled using the Biolog system and API 20 NE and by determining the production of proteases, lipases, and lecithinases for each isolate. Isolates grouped into five coherent clusters, predominated by the species P. putida (cluster A), P. fluorescens (cluster B), P. fragi (as identified by Biolog) or P. fluorescens (as identified by API 20 NE) (cluster C), P. fragi (as identified by Biolog) or P. putida (as identified by API 20 NE) (cluster D), and P. fluorescens (cluster E). Isolates within each cluster also displayed similar enzyme activities. Isolates in clusters A, C, and D were generally negative for all three enzyme activities; isolates in cluster B were predominantly positive for all three enzyme activities; and isolates in cluster E were negative for lecithinase but predominantly positive for protease and lipase activities. Thus, only isolates from clusters B and E produced enzyme activities associated with dairy product flavor defects. Thirty-eight ribogroups were differentiated among the 70 isolates. Ribotyping was highly discriminatory for dairy Pseudomonas isolates, with a Simpson's index of discrimination of 0.955. Isolates of the same ribotype were never classified into different clusters, and ribotypes within a given cluster generally showed similar ribotype patterns; thus, specific ribotype fragments may be useful markers for tracking the sources of pseudomonads in dairy production systems. Our results suggest that ribogroups are generally homogeneous with respect to nomenspecies and biovars, confirming the identification potential of ribotyping for Pseudomonas spp.Phenotypic microbiological techniques have proven useful for quantifying and describing bacteria causing fluid dairy product spoilage; however, precise location of the sources of these spoilage organisms in the processing environment or on the farm requires reliable, differential strain identification strategies. Currently available phenotypic speciation strategies for the most common dairy product spoilers, i.e., Pseudomonas spp. (26) and Bacillus spp., frequently yield inconclusive results.

Phenotypic and Genotypic Characterization of Some Pseudomonas sp. Associated with Burkholderia cepacia Isolated from Various Infected Fishes

“…Many studies have suggested that the phenotypic classification techniques are solely not adequate for identification of Pseudomonas sp., though, overall, the API 20NE was successful in the identification of all the four Pseudomonas strains that had been isolated from fish. That is in agreement with Wiedmann et al [52], who reported that API 20NE resulted in the proper identification of Pseudomonas isolates to the species level.…”

Qualidade microbiológica de leite cru refrigerado e isolamento de bactérias psicrotróficas proteolíticas

“…Dentre os isolados Gram-negativos (75,2%), 27% e 48% foram, respectivamente, Gram-negativos fermentadores e Gram-negativos não-fermentadores. A predominância do isolamento de bactérias Gram-negativas, observada nas amostras de leite cru refrigerado está de acordo com resultados de outras pesquisas, nas quais elas são consideradas como contaminantes mais freqüentes [11,15] 58%, 58% e 47% possuíam atividade de proteases, lipases e de lecitinase, respectivamente [43].…”

“…Bactérias do gênero Pseudomonas têm sido isoladas com maior freqüência do leite e de produtos lácteos refrigerados [11,13,14,15,43], embora não representem mais do que 10% da microbiota do leite cru recém-ordenhado [35]. Esse gênero inclui espécies que apresentam um tempo de geração curto, entre 0 °C e 7 °C, e uma temperatura mínima de crescimento baixa, de até -10 °C [35].…”

Investigation of proteolytic, lipolytic activities and antibiotics susceptibility of some Pseudomonas bacteria isolated from raw milks

“…Hose nozzles and milking equipment can become colonized by Pseudomonas. Also, API 20 NE provided good identification of dairy Pseudomonas isolates to the species level (14,15). In the present study, 15 Pseudomonas strains isolated from raw milk, identified by using API 20 NE and good identification was obtained.…”