Antibacterial activities of coagulase-negative staphylococci from bovine teat apex skin and their inhibitory effect on mastitis-related pathogens

Aims: To explore antibacterial activities of coagulase-negative staphylococci (CoNS) from teat apices of dairy cows towards mastitis-causing pathogens. Methods and Results: Of 254 CoNS, 38 displayed bacteriocin-like activity after a first screening. Seven of these strains displayed activity against at least one mastitis-related pathogen (Streptococcus uberis, Streptococcus dysgalactiae and Staphylococcus aureus). Staphylococcus chromogenes L217 displayed the strongest inhibitory effect, being active against all tested mastitis-related pathogens and most tested CoNS. Based on cation exchange and reversed-phase chromatography, in addition to N-terminal Edman degradation and PCR, the antibacterial peptide was identified as a nukacin-type bacteriocin and named nukacin L217. Although staphylococcal bacteriocins are generally found in the cell-free supernatants of liquid cultures, Staph.chromogenes L217 only led to detectable activity when grown on agar medium. Conclusions: Bacteriocin-like activities are not uncommon among CoNS from teat apices and may inhibit mastitis-causing pathogens, as found for nukacin L217 production by Staph.chromogenes L217. Significance and Impact of the Study Nukacin L217 is the first identified bacteriocin of the species Staph.chromogenes and displays unusual production kinetics, that is, requiring surface growth of its producer. The fact that nukacins are produced by different CoNS species suggests a role in the teat skin ecosystem

Linoleate isomerase activity occurs in lactic acid bacteria strains and is affected by pH and temperature

Aims: To investigate the ability of lactic acid bacteria (LAB) to convert linoleic acid (LA) and a-linolenic acid (alpha-LNA) to conjugated linoleic acid (CLA) and conjugated linolenic acid (CLNA), respectively. To assess pH and temperature influences on CLA and CLNA production by Lactobacillus sakei LMG 13558. Methods and Results: A screening of 48 LAB yielded one Lactobacillus curvatus, five Lactobacillus plantarum and four Lact. sakei strains displaying linoleate isomerase (LAI) activity. CLNA conversion percentages varied largely (1-60%). CLA conversion, occurring in three strains, was lower (2-5%). The LAI gene sequences of the ten LAI-positive strains shared 75-99% identity with the LAI gene sequence of a Lact. plantarum AS1.555. At pH 6.2, CLA and CLNA production by Lact. sakei LMG 13558 was higher at 30 degrees C than at 20 and 25 degrees C. At pH 5.5 (30 degrees C) or 37 degrees C (pH 6.2), LA was not converted and a-LNA only slightly converted. Conclusions: LAB show strain-dependent LAI activity. Production of CLA and CLNA is affected by pH and temperature, as shown for Lact. sakei LMG 13558. Significance and Impact of the Study: Several LAB produce CLA and/or CLNA, as shown for Lact. sakei and Lact. curvatus for the first time. These findings offer potential for the manufacturing of fermented functional foods

Unraveling the microbiota of teat apices of clinically healthy lactating dairy cows, with special emphasis on coagulase-negative staphylococci

Swab samples (n = 72) obtained from the teat apex of lactating dairy cows without visual signs of inflammation (n = 18) were gathered on 2 well-managed Flemish dairy herds (herds 1 and 2) during the same month to assess the bacterial diversity of teat apices before milking. A combination of both culture-dependent [plating and (GTG)(5)-PCR fingerprinting of the colonies] and culture-independent [denaturing gradient gel electrophoresis (PCR-DGGE)] techniques indicated that the teat apices contain a wide diversity of bacterial genera. Despite a low bacterial load, 20 bacterial genera of 3 phyla (Actinobacteria, Firmicutes, and Proteobacteria) were present. The most prevalent bacteria were the coagulase-negative staphylococci (CNS), encompassing a total of 15 species, which were identified to the species level using a combination of (GTG)(5)-PCR fingerprinting, gene sequencing (16S ribosomal RNA and rpoB genes), and a novel PCR-DGGE technique based on the tuf-PCR amplicon. Overall bacterial diversity did not differ significantly between the herds or between noninfected and subclinically infected quarters in herd 1. In herd 1, borderline significant lower CNS species diversity was found on teat apices of noninfected quarters compared with subclinically infected quarters. The most prevalent CNS species were Staphylococcus haemolyticus and Staphylococcus eguorum in both herds and Staphylococcus carnosus in herd 2

Control of bioflavour and safety in fermented sausages: first results of a European project

Four types of fermented sausages were prepared: two using Northern technology (Norway and Belgium) and two using Medi- terranean technology (Belgium and Italy). Mediterranean sausages showed higher pH values and highest residual amounts of myosin and actin. Free fatty acid concentrations re¯ected the nature of the raw material, rather than the ripening period. Italian sausages contained the highest amounts of hexanal. Norwegian sausages contained the highest amounts of both free fatty acids and free amino acids. Putrescine concentration could be related to initial contamination of raw materials. Mediterranean sausages were characterised by a ``pop corn'' odour, identi®ed as 2-acetyl-1-pyrroline. Proteolytic activity of pork Triceps brachii was found to be related to animal sex. Staphylococci and lactic acid bacteria were investigated. Leucine metabolism involving aldehyde production was found to be strain speci®c and very sensitive to pH and the presence of nitrite. Bacteria showed anti-oxidant activity, enhanced by the presence of manganese. Bacteriocin production by L. casei CTC 494 was studied and results incorporated into a mathema- tical model

Control of bioflavour and safety in fermented sausages: first results of a European project.

Four types of fermented sausages were prepared: two using Northern technology (Norway and Belgium) and two using Mediterranean technology (Belgium and Italy). Mediterranean sausages showed higher pH values and highest residual amounts of myosin and actin. Free fatty acid concentrations reflected the nature of the raw material, rather than the ripening period. Italian sausages contained the highest amounts of hexanal. Norwegian sausages contained the highest amounts of both free fatty acids and free amino acids. Putrescine concentration could be related to initial contamination of raw materials. Mediterranean sausages were characterised by a 'pop corn' odour, identified as 2-acetyl-1-pyrroline. Proteolytic activity of pork Triceps brachii was found to be related to animal sex. Staphylococci and lactic acid bacteria were investigated. Leucine metabolism involving aldehyde production was found to be strain specific and very sensitive to pH and the presence of nitrite. Bacteria showed anti-oxidant activity, enhanced by the presence of manganese. Bacteriocin production by L. casei CTC 494 was studied and results incorporated into a mathematical model. (C) 2000 Elsevier Science Ltd