Heat-Resistant Psychrotrophic Bacteria Isolated from Pasteurized Milk

Washam, C. J.; Olson, H. C.; Vedamuthu, E. R.

doi:10.4315/0362-028x-40.2.101

Cited by 51 publications

(13 citation statements)

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“…1b). The presence of high aerobic plate counts in pasteurized milk can be attributed to cross-contamination, however, the issue of some thermoduric microorganisms which are reported to resist heat treatment in food cannot be ignored (Washam et al, 1977). There were 21 % of the pasteurized milk samples which were positive for ALP.…”

Section: Figmentioning

confidence: 94%

Characterization of Escherichia coli and other Enterobacteriaceae in producer-distributor bulk milk

Ntuli

Njage

Buys

2016

Journal of Dairy Science

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INTERPRETIVE SUMMARYCharacterization of E. coli and other Enterobacteriaceae in producer-distributor bulk milk, Ntuli, The direct sale of milk from producer-distributor (PD) to consumers is a common practice in many countries. We characterized E. coli and other Enterobacteriaceae in PD bulk milk sold at retail points in South Africa (SA). The study highlighted that there is a potential risk of transferring drug resistant pathogenic E. coli to consumers through the food chain.Information obtained from the study will be used to model the risk of pathogenic E. coli in PD milk and the proposal of most potentially effective mitigation efforts towards enhancing food security. ABSTRACTThe current study was undertaken to characterize Escherichia coli and other Enterobacteriaceae in raw and pasteurized producer-distributor bulk milk (PDBM). A total of 258 samples were collected from purchase points in 8 provinces in South Africa. The samples were tested for 1 antibiotic residues, phosphatase, total aerobic bacteria, coliforms and E. coli counts. Matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was used for identification of isolates. E. coli isolates were characterized for virulence factors, antimicrobial resistance, serotypes and presumptive E. coli O157:H7. Antibiotic residues and alkaline phosphatase were detected in 2 % (n=258) and 21 % (n=104) of the samples respectively. A total of 729 isolates belonging to 21 genera and 59 species were identified. E. coli, Enterobacter cloacae, Klebsiella oxytoca and Raoultella ornithinolytica were the most abundant species. Spoilage Enterobacteriaceae species exceeded 50 % of the total isolates. E. coli was detected and isolated from 36 % of the milk samples. Thirty one E. coli isolates harbored virulence genes stx1/stx2 and 38 % (n=121) were presumptive O157:H7. Prevalence of samples with presumptive shigatoxin producing E. coli (STEC) was 10 %. Antimicrobial resistant E. coli isolates were detected in 70 % of the milk samples with 36 % of stx1/stx2 positive E. coli showing multi-drug resistance. Information obtained from the study will be used for modelling the public health risk posed by milkborne pathogens in PDBM, which in many cases is consumed by the poor and vulnerable population.

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Section: Figmentioning

confidence: 94%

Characterization of Escherichia coli and other Enterobacteriaceae in producer-distributor bulk milk

Ntuli

Njage

Buys

2016

Journal of Dairy Science

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“…The genus Microbacterium, which showed both lipolytic and proteolytic activity, was ubiquitous in raw milk samples in the present study. Species of Microbacterium are known to be thermoduric, namely, they can survive pasteurization processes (34). Thus, Microbacterium monitoring in raw milk can be used as an indicator of milk quality.…”

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confidence: 99%

Culturable Psychrotrophic Bacterial Communities in Raw Milk and Their Proteolytic and Lipolytic Traits

Hantsis-Zacharov

Halpern

2007

Appl Environ Microbiol

272

189

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During cold storage after milk collection, psychrotrophic bacterial populations dominate the microflora, and their extracellular enzymes, mainly proteases and lipases, contribute to the spoilage of dairy products. The diversity, dynamics, and enzymatic traits of culturable psychrotrophs in raw milk from four farms were investigated over a 10-month period. About 20% of the isolates were found to be novel species, indicating that there is still much to be learned about culturable psychrotrophs in raw milk. The psychrotrophic isolates were identified and classified in seven classes. Three classes were predominant, with high species richness (18 to 21 species per class) in different seasons of the year: Gammaproteobacteria in spring and winter, Bacilli in summer, and Actinobacteria in autumn. The four minor classes were Alphaproteobacteria, Betaproteobacteria, Flavobacteria, and Sphingobacteria. The dominant classes were found in all four dairies, although every dairy had its own unique "bacterial profile." Most but not all bacterial isolates had either lipolytic or both lipolytic and proteolytic activities. Only a few isolates showed proteolytic activity alone. The dominant genera, Pseudomonas and Acinetobacter (Gammaproteobacteria), showed mainly lipolytic activity, Microbacterium (Actinobacteria) was highly lipolytic and proteolytic, and the lactic acid bacteria (Lactococcus and Leuconostoc) displayed very minor enzymatic ability. Hence, the composition of psychrotrophic bacterial flora in raw milk has an important role in the determination of milk quality. Monitoring the dominant psychrotrophic species responsible for the production of heat-stable proteolytic and lipolytic enzymes offers a sensitive and efficient tool for maintaining better milk quality in the milk industry.

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“…The collective tanks presented equal frequency of cocci and bacilli (17.8 %) as can be seen in Figure 1. According to Muir (1990), the proteolytic activity of Gram positive microorganisms is low; however, some authors attribute changes in taste and quality of dairy products to the genus Bacillus (MUIR, 1996;SORHAUNG;STEPANIAK, 1997;WASHAM;OLSON;VEDAMUTHU, 1977). Andrade, Ajao and Zottola (1998) reported that Enterococcus faecium is the most abundant species detected in pasteurized refrigerated milk.…”

Section: Physicochemical Analysesmentioning

confidence: 99%

Refrigerated raw milk quality of a processing plant in the north of Parana after the implementation of changes imposed by NI 62 of 2011

et al. 2012

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This study aimed to compare the microbiological and physicochemical quality of raw milk from individual and collective tanks, identify the psychrotrophic microbiota of refrigerated raw milk and verify compliance with current legislation. The enumeration of proteolytic and lipolytic psychrotrophs, as well as, populations of mesophilic aerobes, total coliforms, E. coli and enterobacteria was carried out. The psychrotrophic microbiota was characterized by morpho-tinctorial tests. Determination of fat content, protein, lactose, total solids, titratable acidity, cryoscopic index and somatic cells count (SCC) were also conducted. The average counts of mesophilic aerobes did not met the minimum quality requirements; however, the average results of SCC and the physicochemical parameters were in accordance with Brazilian legislation. The psychrotrophs counts were on average 90% of the total count of mesophilic aerobes, with psychrotrophic population of less than 6 log CFU/ml. A high percentage of proteolytic and lipolytic psychrotrophs in relation to psychrotrophs total counts was found. Considering the two weeks testing, there was a significant difference (P> 0.05) between milk samples from collective and individual tanks only for total coliforms and for protein and lactose contents. Although the predominant psychrotrophic microbiota was Gram negative bacilli, but Gram positive bacteria were also found. Thus, the population of mesophilic aerobes in disagreement with the legislation and the high counts of psychrotrophic and Gram negative population in milk are indicative that yet, there are problems in the sanitary-hygienic production, storage and transportation of refrigerated raw milk produced in the region studied. Therefore, there is a gap between the practices recommended by legislation and the actions really found in the Brazilian milk production chain. ResumoEste estudo teve como objetivo comparar a qualidade microbiológica e físico-química de leite cru proveniente de tanques individuais e coletivos, identificar a microbiota psicrotrófica do leite cru refrigerado e verificar o cumprimento da legislação vigente para este alimento. Realizou-se a contagem da microbiota de psicrotróficos, proteolíticos, lipolíticos, aeróbios mesófilos, coliformes totais, E. coli e enterobactérias. A microbiota psicrotrófica foi caracterizada através de testes morfotintoriais. Análises dos teores de gordura, proteína, lactose, sólidos totais, acidez titulável, índice crioscópico e contagem de células somáticas (CCS) também foram realizados. As contagens médias de aeróbios mesófilos não atenderam aos requisitos mínimos de qualidade, já os resultados médios de CCS e os parâmetros físico-químicos estudados estavam de acordo com a legislação vigente. A contagem de psicrotróficos foi, em média, 90% da contagem total de aeróbios mesófilos, com contagens de psicrotróficos menores que 6 log UFC/ml. Foi encontrada alta porcentagem de proteolíticos e lipolíticos em relação à contagem total de psicrotróficos. Considerando as duas semanas...

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Heat-Resistant Psychrotrophic Bacteria Isolated from Pasteurized Milk

Cited by 51 publications

References 0 publications

Characterization of Escherichia coli and other Enterobacteriaceae in producer-distributor bulk milk

Characterization of Escherichia coli and other Enterobacteriaceae in producer-distributor bulk milk

Culturable Psychrotrophic Bacterial Communities in Raw Milk and Their Proteolytic and Lipolytic Traits

Refrigerated raw milk quality of a processing plant in the north of Parana after the implementation of changes imposed by NI 62 of 2011

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