N2 Gas Flushing Alleviates the Loss of Bacterial Diversity and Inhibits Psychrotrophic Pseudomonas during the Cold Storage of Bovine Raw Milk

Gschwendtner, Silvia; Alatossava, Tapani; Kublik, Susanne; Fuka, Mirna Mrkonjić; Schloter, Michael; Munsch-Alatossava, Patricia

doi:10.1371/journal.pone.0146015

Cited by 29 publications

(39 citation statements)

References 59 publications

(70 reference statements)

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“…At the moment of the sampling, raw milk temperature was 4 °C: its microbiological analyses revealed the presence of a high population (ca., 5.4 log cfu/ml) of Pseudomonas spp., which increased of almost two log units during the refrigeration of milk at 7 °C reaching about 7.04 log cfu/ml after 48 hr (Figure ). Such finding is in agreement with literature, since storage at low temperatures for long times may favor the proliferation of these gram negative psychrotrophic bacteria so that they could become the dominant nonlactic microbial population of milk (Gschwendtner et al, ). Pseudomonas spp.…”

Section: Resultssupporting

confidence: 93%

“…Pseudomonas spp. are ubiquitous bacteria well known as frequent agents of spoilage of raw and thermized milk (Gschwendtner et al, ; McPhee & Griffiths, ). Their pigments or extracellular enzymes such as lipases, proteases, and thermostable lecithinase are not inactivated by the thermal sanitization of milk, and therefore, may spoilage the milk and lower its nutritional value even when the relevant vegetative cells have been inactivated (Gschwendtner et al, ).…”

Section: Resultsmentioning

confidence: 99%

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Effect of refrigeration and probiotic adjunct on pathogenic and spoilage microorganisms in raw milk for direct human consumption

Faggiano

Chieffi

Logrieco

et al. 2017

J Food Process Preserv

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We analyzed the microbiological quality and safety of raw milk from vending machine and assessed the evolution of its microbiota during the refrigeration at 7 °C. We also monitored the survival of E. coli O157:H7 strain artificially added to the raw milk during the refrigeration and investigated the possibility to use the probiotic Lactobacillus rhamnosus GG strain to control pathogenic and spoilage bacteria in raw milk. Total aerobic mesophilic microbiota of raw milk exceeded the limit allowed by the current European legislation and increased of about two log units after 48 hr of refrigeration at 7 °C. The spiked E. coli O157:H7 strain multiplied slowly in the refrigerated raw milk increasing of about 1 log unit, whereas the probiotic strain was able to slightly lower the populations of Pseudomonas spp., Listeria spp. and Staphylococcus aureus but was unable to inhibit the growth of E. coli O157:H7. Practical applications This study allowed us to confirm the microbiological threat associated to the direct consumption of raw milk. Ad hoc strategies to improve the overall microbiological quality of raw milk from vending machines within the whole chain (from farm to consumption) are needed. A protective and probiotic adjunct able to control spoilage and pathogenic bacteria in raw milk with an adequate microbiological quality (at least compliant with the current legislation) may be a valuable mitigation strategy, but probiotic strains more effective than L. rhamnosus GG should be used.

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Section: Resultssupporting

confidence: 93%

Section: Resultsmentioning

confidence: 99%

Effect of refrigeration and probiotic adjunct on pathogenic and spoilage microorganisms in raw milk for direct human consumption

Faggiano

Chieffi

Logrieco

et al. 2017

J Food Process Preserv

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“…The point that N 2 gas alleviated the loss of bacterial diversity during cold storage was already highlighted by the NGS approach (Gschwendtner et al, 2016); we hypothesize that by better preserving bacterial diversity during cold storage, the N 2 gas flushing may better prevent the occurrence of a “favorable to a few” niche and consequently better prevent the rise of antibiotic multi-resistance in raw milk.…”

Section: Discussionmentioning

confidence: 63%

N2 Gas Flushing Limits the Rise of Antibiotic-Resistant Bacteria in Bovine Raw Milk during Cold Storage

et al. 2017

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Antibiotic resistance has been noted to be a major and increasing human health issue. Cold storage of raw milk promotes the thriving of psychrotrophic/psychrotolerant bacteria, which are well known for their ability to produce enzymes that are frequently heat stable. However, these bacteria also carry antibiotic resistance (AR) features. In places, where no cold chain facilities are available and despite existing recommendations numerous adulterants, including antibiotics, are added to raw milk. Previously, N2 gas flushing showed real potential for hindering bacterial growth in raw milk at a storage temperature ranging from 6 to 25°C. Here, the ability of N2 gas (N) to tackle antibiotic- resistant bacteria was tested and compared to that of the activated lactoperoxidase system (HT) for three raw milk samples that were stored at 6°C for 7 days. To that end, the mesophiles and psychrotrophs that were resistant to gentamycin (G), ceftazidime (Ce), levofloxacin (L), and trimethoprim-sulfamethoxazole (TS) were enumerated. For the log10 ratio (which is defined as the bacterial counts from a certain condition divided by the counts on the corresponding control), classical Analyses of Variance (ANOVA) was performed, followed by a mean comparison with the Ryan-Einot-Gabriel-Welsch multiple range test (REGWQ). If the storage “time” factor was the major determinant of the recorded effects, cold storage alone or in combination with HT or with N promoted a sample-dependent response in consideration of the AR levels. The efficiency of N in limiting the increase in AR was highest for fresh raw milk and was judged to be equivalent to that of HT for one sample and superior to that of HT for the two other samples; moreover, compared to HT, N seemed to favor a more diverse community at 6°C that was less heavily loaded with antibiotic multi-resistance features. Our results imply that N2 gas flushing could strengthen cold storage of raw milk by tackling the bacterial spoilage potential while simultaneously hindering the increase of bacteria carrying antibiotic resistance/multi-resistance features.

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“…Furthermore, the adoption of systems using continuos N 2 gas-flushing of raw milk can reduce Pseudomonas spp. growth (Gschwendtner et al 2016).…”

Section: Resultsmentioning

confidence: 99%

Pseudomonas spp.: contamination sources in bulk tanks of dairy farms

Vidal

Netto²,

Vaz

et al. 2017

Pesq. Vet. Bras.

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RESUMO.-[Pseudomonas spp.: fontes de contaminação em tanques de expansão em fazendas leiteiras.] Este estudo se propôs a isolar Pseudomonas spp. durante o processo de ordenha em dez fazendas com sistemas manuais e mecanizados, durante as estações seca e chuvosa, além de avaliar a homologia do DNA e seus padrões de distribuição entre os isolados, a fim de se determinar as principais fontes de contaminação do leite. Cento e sessenta e sete isolados de Pseudomonas spp. foram obtidos a partir de amostras de água, mãos de ordenhadores, tetos, teteiras, tanques de resfriamento e leite cru armazenado, sendo 85 e 82 pontos de amostragem em fazendas com sistemas de ordenha manual e mecânico, respectivamente. Diferença estatisticamente significativa foi encontrada entre os isolados observados entre a superfície dos tetos antes e após o pré-dipping (p=0,02), mas nenhuma diferença foi encontrada entre sistemas de ordenha ou estações (p>0,05 This study focused on isolating Pseudomonas spp. during milking process in ten dairy farms with manual and mechanical milking systems during dry and rainy seasons, and evaluating DNA homology and patterns of distribution between isolates, in order to identify main sources of milk contamination by Pseudomonas spp. A total of 167 isolates of Pseudomonas spp. were obtained from water, milkers' hands, cows' teats, teat cups, cooling tanks and raw milk. Bacteria of Pseudomonas spp. genus were isolated from 85 and 82 sampling points in dairy farms with manual and mechanical milking system, respectively. A significant difference (p=0.02) on Pseudomonas spp. isolation was observed among samples of surface of cows' teats before and after pre-dipping, but no significant difference (p>0.05) was observed among milking systems or seasons. The possibility of the same Pseudomonas spp. patterns are distributed in different farms and seasons using Amplified Fragment Length Polymorphism (AFLP) technique was demonstrated. Milkers' hands, surface of cows' teats, teat cups and cooling tanks were associated with raw milk contamination with Pseudomonas spp. on farms with manual and mechanical milking system, showing that regardless of the type of milking system and season, proper hygiene procedures of equipment, utensils and workers' hands are essential to avoid contamination of the milk and, therefore, improve milk quality.

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N2 Gas Flushing Alleviates the Loss of Bacterial Diversity and Inhibits Psychrotrophic Pseudomonas during the Cold Storage of Bovine Raw Milk

Cited by 29 publications

References 59 publications

Effect of refrigeration and probiotic adjunct on pathogenic and spoilage microorganisms in raw milk for direct human consumption

Effect of refrigeration and probiotic adjunct on pathogenic and spoilage microorganisms in raw milk for direct human consumption

N2 Gas Flushing Limits the Rise of Antibiotic-Resistant Bacteria in Bovine Raw Milk during Cold Storage

Pseudomonas spp.: contamination sources in bulk tanks of dairy farms

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