Detection of acylated homoserine lactones in gram-negative proteolytic psychrotrophic bacteria isolated from cooled raw milk

Food Control ◽  
2007 ◽  
Vol 18 (10) ◽  
pp. 1322-1327 ◽  
Author(s):  
Uelinton Manoel Pinto ◽  
Eliseth de Souza Viana ◽  
Maurilio Lopes Martins ◽  
Maria Cristina Dantas Vanetti
Keyword(s):  
Raw Milk ◽  
Gram Negative ◽  
Homoserine Lactones ◽  
Psychrotrophic Bacteria ◽  
Acylated Homoserine Lactones

Heat-Stable Proteases from Psychrotrophs in Milk

1980 ◽  
Vol 43 (3) ◽  
pp. 197-200 ◽  
Author(s):  
A. GEBRE-EGZIABHER ◽  
E. S. HUMBERT ◽  
G. BLANKENAGEL
Keyword(s):  
Molecular Weight ◽  
Gel Electrophoresis ◽  
Dairy Products ◽  
Raw Milk ◽  
Gram Negative ◽  
Psychrotrophic Bacteria ◽  
Heat Resistant ◽  
Heat Stable ◽  
Single Enzyme

Twelve gram-negative psychrotrophic bacteria producing heat-resistant proteases that hydrolyzed casein were isolated from refrigerated raw milk. All were pseudomonads and the enzymes of the six most proteolytic cultures were examined further. The proteases were partially purified, and gel electrophoresis indicated that only a single enzyme was present in the preparation. The molecular weight of most of the proteases was approximately 45,000. All six enzymes retained some activity after being heated at 121 C for 10 min and casein was hydrolyzed at pH levels found in normal milk and many cultured dairy products. Although proteolysis was highest at about 40 C, considerable activity was evident at refrigeration temperatures.

Adherence of psychrotrophic bacteria to dairy equipment surfaces

1992 ◽  
Vol 59 (3) ◽  
pp. 381-388 ◽  
Author(s):  
Beatriz Suárez ◽  
Carlos M. Ferreirós ◽  
Maria-Teresa Criado
Keyword(s):  
Raw Milk ◽  
Surface Hydrophobicity ◽  
Bacterial Adherence ◽  
Gram Negative Bacteria ◽  
Relevant Factor ◽  
Gram Negative ◽  
Bacterial Surface ◽  
Psychrotrophic Bacteria ◽  
Gram Positive Bacteria ◽  
Dairy Equipment

SummaryPsychrotrophic bacteria isolated from raw milk were tested for their ability to adhere to steel, two types of rubber, and glass, materials employed in the construction of milking equipment. The adherence assays were carried out by exposure of the materials to radioactively labelled bacteria in both a buffering solution (Ringer's) and milk. The degree of adherence of Gram-positive bacteria was lower (P< 0·001) than that of Gram-negative bacteria. Glass was the material least prone to bacterial adherence (P< 0·001); there were no significant differences between the other three materials. Milk was found to inhibit adhesion significantly (P< 0·05), this inhibition being more evident with the most adherent bacteria. There was no statistically significant correlation between bacterial surface hydrophobicity and adherence. Our results suggest that intrinsic bacterial adherence cannot be considered a relevant factor in the contamination of milking equipment.

scholarly journals Identification of the contaminating psychrotrophic bacteria in refrigerated bulked raw milk and the assessment of their deteriorating potential

2022 ◽  
Vol 43 (2) ◽  
pp. 739-750
Author(s):  
Patricia Rodrigues Condé ◽  
◽  
Cláudia Lúcia de Oliveira Pinto ◽  
Scarlet Ohana Gandra ◽  
Renata Cristina Almeida Bianchini Campos ◽  
...  
Keyword(s):  
Culture Media ◽  
Raw Milk ◽  
Culture Collection ◽  
Economic Losses ◽  
Prevention Measures ◽  
Multivariate Statistical ◽  
Gram Negative ◽  
Psychrotrophic Bacteria ◽  
Components Analysis ◽  
Specific Culture

This work aimed to characterize, identify, and determine the deteriorating potential of the contaminating psychrotrophic bacteria in refrigerated raw milk. Samples were submitted to serial dilutions and plated in specific culture media to form a bacterial culture collection. The isolates were characterized for their morphology and biochemical characteristics. The deteriorating potential of the isolates was determined according to the proteolytic, lipolytic and lecithinase activities at 4.0 ºC, 6.5 ºC, and 25.0 ºC. The results obtained for deterioration potential were assessed by the multivariate statistical method and by the principal components analysis (PCA). A total of 159 isolates were characterized, and of these, 46 strongly proteolytic Gram-negative isolates were selected for identification using the API 20 NE kit. The predominant bacteria were Gram-negative and oxidase and catalase positive, with a predominance of bacteria of the genus Pseudomonas. Using PCA, it was shown that the bacteria with the greatest deterioration potential were lecithinase producers, and that, in the autumn, proteolytic bacteria predominated at 4.0 ºC. Of the 46 isolates identified, more than 80% belonged to the species Pseudomonas fluorescens. Thus, attention should be given to the importance of implementing microbial contamination prevention measures in the bulking process, since, even under refrigeration, psychrotrophic bacteria multiply and produce enzymes that deteriorate lipids and proteins, with consequent quality losses of the milk and its derivatives, yield losses in the production of dairy products, and economic losses.

scholarly journals Biofilms on Indwelling Urethral Catheters Produce Quorum-Sensing Signal Molecules In Situ and In Vitro

1998 ◽  
Vol 64 (9) ◽  
pp. 3486-3490 ◽  
Author(s):  
David J. Stickler ◽  
Nicola S. Morris ◽  
Robert J. C. McLean ◽  
Clay Fuqua
Keyword(s):  
Quorum Sensing ◽  
Signal Molecules ◽  
Gram Negative Bacteria ◽  
Feeding Assay ◽  
Gram Negative ◽  
Homoserine Lactones ◽  
Acylated Homoserine Lactones

ABSTRACT Acylated homoserine lactones (AHLs) are chemical signals that mediate population density-dependent (quorum-sensing) gene expression in numerous gram-negative bacteria. In this study, gram-negative bacilli isolated from catheters were screened for AHL production by a cross-feeding assay utilizing an AHL-responsive Agrobacterium tumefaciens reporter strain. Positive reactions were obtained from 14 isolates of Pseudomonas aeruginosa; negative or weakly positive reactions were recorded for isolates of five other species. P. aeruginosa biofilms were then produced on catheters in a physical model of the bladder. Sections of colonized all-silicone catheters gave positive reactions for the quorum-sensing signal molecules as did sections that had been cleaned of biofilm and autoclaved. Control sections of unused catheters were negative in the tests. Sections from four of nine catheters that had been freshly removed from patients gave positive reactions for AHLs. Cleaned autoclaved sections of three of these catheters also gave strongly positive reactions for AHLs. These results demonstrate that AHLs are produced by biofilms as they develop on the catheters both in vitro in the model and in vivo in the patient’s bladder. They represent the first demonstration of AHL production by biofilms in a clinical setting.

scholarly journals Quorum sensing signal molecules (acylated homoserine lactones) in Gram-negative fish pathogenic bacteria

2005 ◽  
Vol 65 ◽  
pp. 43-52 ◽  
Author(s):  
JB Bruhn ◽  
I Dalsgaard ◽  
KF Nielsen ◽  
C Buchholtz ◽  
JL Larsen ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Pathogenic Bacteria ◽  
Signal Molecules ◽  
Gram Negative ◽  
Homoserine Lactones ◽  
Acylated Homoserine Lactones

Genetic diversity of Gram-negative, proteolytic, psychrotrophic bacteria isolated from refrigerated raw milk

2006 ◽  
Vol 111 (2) ◽  
pp. 144-148 ◽  
Author(s):  
Maurilio L. Martins ◽  
Claudia L.O. Pinto ◽  
Rodrigo B. Rocha ◽  
Elza F. de Araújo ◽  
Maria C.D. Vanetti
Keyword(s):  
Genetic Diversity ◽  
Raw Milk ◽  
Gram Negative ◽  
Psychrotrophic Bacteria

PCR BASED DETECTION OF GRAM NEGATIVE PSYCHROTROPHIC BACTERIA IN COWS RAW MILK

2016 ◽  
Vol 15 (1) ◽  
pp. 161-180
Author(s):  
Amjed A. Alrazakkazal ◽  
Fawziah A. Abdullah
Keyword(s):  
Raw Milk ◽  
Gram Negative ◽  
Psychrotrophic Bacteria

Development of a PCR method for detecting proteolytic psychrotrophic bacteria in raw milk

2013 ◽  
Vol 29 (1) ◽  
pp. 8-14 ◽  
Author(s):  
Solimar Gonçalves Machado ◽  
Denise Mara Soares Bazzolli ◽  
Maria Cristina Dantas Vanetti
Keyword(s):  
Raw Milk ◽  
Psychrotrophic Bacteria ◽  
Pcr Method

scholarly journals Whole-Genome Sequencing of Gram-Negative Bacteria Isolated From Bovine Mastitis and Raw Milk: The First Emergence of Colistin mcr-10 and Fosfomycin fosA5 Resistance Genes in Klebsiella pneumoniae in Middle East

2021 ◽  
Vol 12 ◽  
Author(s):  
Yasmine H. Tartor ◽  
Norhan K. Abd El-Aziz ◽  
Rasha M. A. Gharieb ◽  
Hend M. El Damaty ◽  
Shymaa Enany ◽  
...  
Keyword(s):  
Antimicrobial Resistance ◽  
Klebsiella Pneumoniae ◽  
Genome Sequencing ◽  
Bovine Milk ◽  
Bovine Mastitis ◽  
Raw Milk ◽  
Whole Genome ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
E Coli

Antimicrobial resistance is a major concern in the dairy industry. This study investigated the prevalence, antimicrobial resistance phenotypes, and genome sequencing of Gram-negative bacteria isolated from clinical (n = 350) and subclinical (n = 95) bovine mastitis, and raw unpasteurized milk (n = 125). Klebsiella pneumoniae, Aeromonas hydrophila, Enterobacter cloacae (100% each), Escherichia coli (87.78%), and Proteus mirabilis (69.7%) were the most prevalent multidrug-resistant (MDR) species. Extensive drug-resistance (XDR) phenotype was found in P. mirabilis (30.30%) and E. coli (3.33%) isolates. Ten isolates (four E. coli, three Klebsiella species and three P. mirabilis) that displayed the highest multiple antibiotic resistance (MAR) indices (0.54–0.83), were exposed to whole-genome sequencing (WGS). Two multilocus sequence types (MLST): ST2165 and ST7624 were identified among the sequenced E. coli isolates. Three E. coli isolates (two from clinical mastitis and one from raw milk) belonging to ST2165 showed similar profile of plasmid replicon types: IncFIA, IncFIB, IncFII, and IncQ1 with an exception to an isolate that contained IncR, whereas E. coli ST7624 showed a different plasmid profile including IncHI2, IncHI2A, IncI1α, and IncFII replicon types. ResFinder findings revealed the presence of plasmid-mediated colistin mcr-10 and fosfomycin fosA5 resistance genes in a K. pneumoniae (K1) isolate from bovine milk. Sequence analysis of the reconstructed mcr-10 plasmid from WGS of K1 isolate, showed that mcr-10 gene was bracketed by xerC and insertion sequence IS26 on an IncFIB plasmid. Phylogenetic analysis revealed that K1 isolate existed in a clade including mcr-10-harboring isolates from human and environment with different STs and countries [United Kingdom (ST788), Australia (ST323), Malawi (ST2144), Myanmar (ST705), and Laos (ST2355)]. This study reports the first emergence of K. pneumoniae co-harboring mcr-10 and fosA5 genes from bovine milk in the Middle East, which constitutes a public health threat and heralds the penetration of the last-resort antibiotics. Hence, prudent use of antibiotics in both humans and animals and antimicrobial surveillance plans are urgently required.

Sign in / Sign up

Export Citation Format

Share Document