Biomedical subjects

C Hill

Publications and source records attributed to C Hill.

At least 55 records · Page 3Linked to original sources

PubMed2001

Renal proximal tubule function is preserved in Cftr(tm2cam) deltaF508 cystic fibrosis mice.

1. Changes in proximal tubule function have been reported in cystic fibrosis patients. The aim of this study was to investigate proximal tubule function in the Cftr(tm2cam)deltaF508 cystic fibrosis (CF) mouse model. A range of techniques were used including renal clearance studies, in situ microperfusion, RT-PCR and whole-cell patch clamping. 2. Renal Na(+) clearance was similar in wild-type (1.4 +/- 0.3 microl min(-1), number of animals, N = 12) and CF mice (1.6 +/- 0.4 microl min(-1), N = 7) under control conditions. Acute extracellular volume expansion resulted in significant natriuresis in wild-type (7.0 +/- 0.8 microl min(-1), N = 8) and CF mice (9.3 +/- 1.4 microl min(-1), N = 9); no difference between genotypes was observed. 3. In situ microperfusion revealed that fluid absorptive rate (Jv) was similar under control conditions between wild-type (2.2 +/- 0.4 nl mm(-1) min(-1), n = 10) and CF mice (1.9 +/- 0.3 nl mm(-1) min(-1), n = 11). Addition of a forskolin-dibutyryl cAMP (db-cAMP) cocktail to the perfusate caused no significant change in Jv in either wild-type (2.6 +/- 0.7 nl mm(-1) min(-1), n = 10) or Cftr(tm2cam)deltaF508 mice (2.0 +/- 0.5 nl mm(-1) min(-1), n = 10). 4. CFTR expression was confirmed in samples of outer cortex using RT-PCR. However, no evidence for functional CFTR was obtained when outer cortical cells were stimulated with protein kinase A or forskolin-db-cAMP using whole-cell patch clamping. 5. In conclusion, no functional deficit in proximal tubule function was found in Cftr(tm2cam)deltaF508 mice. This may be a consequence of a lack of whole-cell cAMP-dependent Cl(-) conductance in mouse proximal tubule cells.

Animals↗

PubMed2001

Pre-inoculation enrichment procedure enhances the performance of bacteriocinogenic Lactococcus lactis meat starter culture.

Sodium nitrite and sodium chloride may inhibit growth and bacteriocinogenesis of protective starter cultures. To reduce sensitivity of a lacticin 3147-producing starter culture to nitrite, prior to production of salami, Lactococcus lactis DPC 4275 was placed in a number of pre-inoculation treatments, containing (a) 1% glucose, (b) 2.5 ppm manganese (Mn), (c) 250 ppm magnesium (Mg), (d) 2.5 ppm manganese + 250 ppm magnesium (Mn + Mg), and held at ambient temperature for 30 min and 4 degrees C for 2 h. The growth, pH reduction, and bacteriocin production was monitored in beaker sausage over a period of 10 days at 28 degrees C, corresponding to typical salami production time, and compared to untreated starter culture. The effect of 1% tryptone and inoculum level on growth and bacteriocin production was also determined. Challenge tests were performed using Listeria innocua DPC 1770 and Staphylococcus aureus MMPR3 as target strains. All treatments gave a significantly higher (P < 0.05) initial starter level than the untreated starter. Beaker sausage inoculated with either low (10(7)) or high (10(9)) levels of starter culture, treated with Mn + Mg reached significantly (P < 0.05) higher levels by day 10 than other treatments. Trends indicate that Mn + Mg also gave best pH reduction in sausage containing the low-level starter culture, sausage and significantly lower (P < 0.05) values for sausage produced with higher inoculum. Bacteriocin production was also higher in starter culture treated with Mn, or glucose. Pre-treatment with Mg gave a 2-fold increase in bacteriocin, the addition of Mn augmenting this increase further. The incorporation of tryptone gave no additional effect. In beaker sausage, both L. innocua and S. aureus populations showed significant reductions (P < 0.05) in the presence of the bacteriocinogenic strain compared to a non-bacteriocinogenic control strain.

Antibiosis↗

PubMed2001

Molecular detection and sequencing of "Norwalk-like viruses" in outbreaks and sporadic cases of gastroenteritis in Ireland.

Norwalk-like viruses (NLVs) are now established as the most important causative agents of epidemic gastroenteritis worldwide. The overall objective of this study was to determine the molecular epidemiology of Irish NLV isolates for the first time by obtaining sequence data from specimens originating from outbreaks and sporadic cases of gastroenteritis. Eight samples from sporadic cases of gastroenteritis and nine isolates from separate NLV outbreaks were examined. Of the sporadic isolates, six were shown to be genogroup 2 (G2) by RT-PCR, while two were G1. All of the outbreak isolates were G2. All isolates were partially sequenced within a highly conserved region of ORF1 (RNA-dependent RNA polymerase gene). Sequence data were aligned and a dendogram was constructed. The results indicated that the majority of G2 isolates were seen to cluster with Bristol and Lordsdale virus, while the two G1 specimens were related most closely to Southampton virus. Further downstream sequence analysis of a number of the isolates confirmed this result. It is concluded that the majority of NLV isolates circulating in Ireland belong to the Bristol/Lordsdale clade.

Base Sequence↗

PubMed2001

Angiotensin converting enzyme inhibitor suppresses glomerular transforming growth factor beta receptor expression in experimental diabetes in rats.

AIMS/HYPOTHESIS: Activation of the renal transforming growth factor beta (TGF-beta) axis has been suggested to play a part in the development of diabetic nephropathy by a direct stimulatory effect of hyperglycaemia or through the activation of the renin-angiotensin system. Our aim was to evaluate the involvement of the renin-angiotensin system by examining the effects of ACE-inhibition on intrarenal changes in all three TGF-beta isoforms and receptors in experimental diabetes in vivo. METHODS: Immunocytochemistry, western blotting and ribonuclease protection assays were carried out for each TGF-beta isoform and receptor on kidney from non-diabetic and streptozotocin-diabetic rats after treatment with the ACE inhibitor, enalapril, for 30 days. RESULTS: Enalapril partially prevented the renal hypertrophy and fully prevented the increase in urinary albumin excretion rate in diabetic animals. The glomerular TGF-beta Type II Receptor mRNA and protein concentrations increased over 30 days in untreated diabetic animals compared with non-diabetic controls, while enalapril-treated diabetic animals showed a normalisation of TGF-beta Type II Receptor mRNA and protein. CONCLUSION/INTERPRETATION: The ACE-inhibition had pronounced inhibitory effects on the increased expression of the glomerular TGF-beta Type II Receptor in the diabetic kidney required for intracellular signalling through this growth factor axis. This suggests a new mechanism of action of the ACE-inhibition in regulating the development of diabetic nephropathy.

Albuminuria↗

PubMed2001

Clinical morbidity in pediatric dialysis patients: data from the Network 1 Clinical Indicators Project.

The Health Care Financing Administration (HCFA) has gathered clinical data on end stage renal disease (ESRD) patients since 1994, but details are only available on patients >/=18 years. In this report, we present morbidity data collected prospectively over 12 months from all children (1-18 years) maintained on either hemodialysis (HD) or peritoneal dialysis (PD) within the six-state New England area. During this year, 17 observations were recorded on 14 HD patients (age 13.4+/- 11.3 years) and 36 observations were made on 25 PD patients (age 11.5+/-4.8 years; mean +/- SD). These patients were generally highly functional, attending school at least part time in nearly all cases. Dialysis adequacy index (DAI), defined as the delivered KT/V divided by DOQI guideline values, indicated that patients were well dialyzed (HD 1.41+/-0.1 and PD 1.10+/-0.1; mean +/- SE). When all dialysis patients were grouped and analyzed, the DAI did not correlate with number of hospitalizations, degree of anemia, serum albumin, or type of dialysis. The number of hospitalizations were greater the younger the patient (P<0.01). The need for antihypertensive medications was higher in the children maintained on HD (94%) compared to children on PD (58%) (P<0.01). Lastly, while serum ferritin did not correlate with serum iron, hematocrit or Epo dosage, it was inversely related to serum albumin (P<0.03). We conclude that, in children, (1) exceeding suggested dialysis adequacy may not improve patient morbidity, (2) the need for antihypertensive medications appears greater in children maintained on HD, and (3) inflammation may play a role in determining serum albumin independent of nutrition.

Adolescent↗

PubMed2001

Meta-analyses of randomised clinical trials in oncology.

A meta-analysis is a quantitative synthesis of randomised clinical trials, used to evaluate moderate treatment effects in oncology. It is complementary to large-scale trials. We describes the principles, methods, and limits of meta-analyses. The gold standard for a meta-analysis is to obtain individual patient data directly from each principal investigator, but this is time-consuming and costly. The main steps of a meta-analysis using individual patient data are described. Multidisciplinary collaboration is needed for clinical insight and critical review of the data and results. Meta-analysis should include an evaluation of the trial quality, a quantification of the overall treatment effect, a study of the variations seen in this effect between trials, and pre-planned exploratory analyses to identify groups of patients who may benefit more from the treatment. Statistical methods are explained using real working examples. Since literature-based meta-analysis can lead to seriously biased assessments, meta-analyses of individual patient data should be undertaken systematically when long-term follow-up is needed, when a detailed analysis is important, or when the literature-based meta-analyses are not in agreement. The main factors which influence the quality of a meta-analysis are discussed.

Data Interpretation, Statistical↗

PubMed2001

Pharmacodynamics of tandem high-dose melphalan with peripheral blood stem cell transplantation in children with neuroblastoma and medulloblastoma.

Repeated high-dose (HD) chemotherapy with peripheral blood stem cell (PBSC) transplantation is a new modality aimed at increasing both the dose and its intensity in the treatment of chemosensitive tumours. The aim of this study was to evaluate the tolerance, pharmacokinetics (PK) and pharmacodynamics (PD) of HD single-agent melphalan administered over two consecutive courses (C1 and C2) in children. Twenty-one patients (10 girls) with a median age of 4.1 years (range 8 months-14 years) were entered into this study. Five had metastatic neuroblastoma (NB) and 16 a cerebral primitive neuroectodermal tumour (PNET). Melphalan was given at a dose of 100 mg/m(2) every 21 days. PBSCs were infused at a median number of 2.98 x 10(6) CD34(+) cells/kg. Forty courses, ie 21 C1 and 19 C2, were administered. Both courses were well tolerated. The median duration of ANC < 500/microl was 7 and 6 days after C1 and C2, respectively. Platelet recovery (not mandatory to continue the HD strategy) was achieved in 52% of courses. GI toxicity was mild to moderate. The melphalan AUC ranged from 177 to 475 microg small middle dotmin/ml (no difference between C1 and C2). Prolonged neutropenia was associated with a young age (P < 0.001) and a low amount of CFU-GM (P = 0.002). A long time to platelet recovery was associated with a high AUC (P = 0.004) and a young age (P = 0.02). Grade 1 or 2 GI toxicity was associated with a high AUC (P = 0.015). Partial remission was observed in 11/14 patients with measurable cerebral PNET. In conclusion, tandem HD melphalan is feasible and safe in children, and achieved a high response rate in cerebral PNET. The observed PK-PD relationships may help us design PK-guided outpatient treatment.

Adolescent↗

PubMed2001

Early response to chemotherapy as a prognostic factor in childhood acute lymphoblastic leukaemia: a methodological review.

Published studies of the prognostic value of the early response to induction treatment in childhood acute lymphoblastic leukaemia (ALL) were analysed. Three criteria were used to judge the early treatment response: persistence of peripheral blasts (PPB) or of bone marrow blasts (PBMB) during induction therapy and minimal residual disease (MRD) after completion of induction therapy. Studies with more than 50 patients, published between 1980 and 2000, were reviewed. Among 13 659 distinct articles published on ALL, we identified only 43 applicable studies. Within- and between-laboratory variations were evaluated in only one study. Treatment modalities differed among, and sometimes within, studies. The cut-off points used in the statistical analyses were never discussed, and in many studies appeared to be selected after multiple tests. The proportion of missing data was > 30% in almost all studies of MRD, as a result of technical difficulties and not missing samples. PPB and PBMB were associated with shorter survival in, respectively, 13 out of 14 and 15 out of 16 studies. Detection of MRD was associated with poor outcome in 12 of the 13 studies. Because none of the parameters used to measure the early response to induction therapy for childhood ALL have been properly assessed as prognostic factors, we conclude that they should be considered only as candidate prognostic indicators pending more thorough studies.

Bone Marrow↗

PubMed2001

Regulation of immunity to the two-component lantibiotic, lacticin 3147, by the transcriptional repressor LtnR.

Lacticin 3147 is a membrane-active, two-component lantibiotic produced by Lactococcus lactis ssp. lactis DPC3147. In this study, the promoters of the lacticin 3147 gene cluster were mapped to the intergenic region between ltnR and ltnA1 (the genes encoding the regulatory protein LtnR and the first structural gene, LtnA1), and Northern analyses revealed that the biosynthetic and immunity genes are divergently transcribed in two operons, ltnA1A2M1TM2D and ltnRIFE respectively. Although the promoter controlling biosynthesis (Pbac) appears to be constitutive, characterization of a downstream beta-galactosidase (beta-gal) fusion beyond an intragenic stem-loop structure in ltnM1 confirmed that this putative transcriptional attenuator allows limited readthrough to the downstream biosynthetic genes, thus maintaining the correct stoichiometry between structural peptides and biosynthetic machinery. The promoter of the ltnRIFE operon (Pimm) was shown to be regulated by the transcriptional repressor LtnR. A mutant with a truncated ltnR gene exhibited a hyperimmune phenotype, whereas overexpression of ltnR resulted in cells with increased sensitivity to lacticin 3147. Gel mobility shift analysis indicated that LtnR binds to the Pimm promoter region, and fusion of this promoter to the beta-gal gene of pAK80 revealed that expression from Pimm is significantly reduced in the presence of LtnR. Thus, we have demonstrated that lacticin 3147 uses a regulatory mechanism not previously identified in lantibiotic systems.

Anti-Bacterial Agents↗

PubMed2001

A glutamate decarboxylase system protects Listeria monocytogenes in gastric fluid.

We observed that glutamate greatly enhances the survival of Listeria monocytogenes in gastric fluid, a phenomenon that is directly linked to glutamate decarboxylase activity (GAD). Glutamate-mediated acid tolerance has been associated in other intestinal genera with the GAD system, in which glutamate is internalized and converted to gamma-aminobutyrate (consuming an intracellular proton) that is subsequently exchanged for another extracellular glutamate via a membrane-located antiporter. Molecular analysis of L. monocytogenes LO28 revealed the presence of two glutamate decarboxylase homologues, designated gadA and gadB, that are differentially expressed. The gadB gene is co-transcribed in tandem with an upstream gene, gadC, which encodes a potential glutamate/gamma-aminobutyrate antiporter. Expression of this transcript is upregulated in response to mild acid stress (pH 5.5). In contrast, expression of the monocistronic gadA message was weaker and was not induced by mild acid treatment. Non-polar deletion mutations resulted in a dramatic decrease in the level of GAD activity and a concomitant decrease in acid resistance in the order LO28 > DeltagadA > DeltagadB = DeltagadC > DeltagadAB for both stationary and logarithmic phase cultures. The exquisite sensitivity of the DeltagadAB mutant to ex vivo porcine and synthetic human gastric fluid demonstrates a clear role for the GAD system in facilitating survival of the organism in the stomach after ingestion and in other low-pH environments. Furthermore, variations in levels of GAD activity between different strains of L. monocytogenes correlate significantly with levels of tolerance to gastric fluid. Sensitive strains, which include the sequenced L. monocytogenes EGD, exhibit reduced levels of GAD activity. It is clear from this study that expression of GAD by L. monocytogenes strains is an absolute requirement for survival in the stomach environment.

Amino Acid Sequence↗

PubMed2001

Heterologous expression of lacticin 3147 in Enterococcus faecalis: comparison of biological activity with cytolysin.

Lacticin 3147 is a broad-spectrum, two-component, lanthionine-containing bacteriocin produced by Lactococcus lactis DPC3147 which has widespread food and biomedical applications as a natural antimicrobial. Other two-component lantibiotics described to date include cytolysin and staphylococcin C55. Interestingly, cytolysin, produced by Enterococcus faecalis, has an associated haemolytic activity. The objective of this study was to compare the biological activity of lacticin 3147 with cytolysin. The lacticin 3147-encoding determinants were heterologously expressed in Ent. faecalis FA2-2, a plasmid-free strain, to generate Ent. faecalis pOM02, thereby facilitating a direct comparison with Ent. faecalis FA2-2.pAD1, a cytolysin producer. Both heterologously expressed lacticin 3147 and cytolysin exhibited a broad spectrum of activity against bacterial targets. Furthermore, enterococci expressing active lacticin 3147 did not exhibit a haemolytic activity against equine blood cells. The results thus indicate that the lacticin 3147 biosynthetic machinery can be heterologously expressed in an enterococcal background resulting in the production of the bacteriocin with no detectable haemolytic activity.

Amino Acid Sequence↗

PubMed2001

Evaluation of a spray-dried lacticin 3147 powder for the control of Listeria monocytogenes and Bacillus cereus in a range of food systems.

AIMS: The potential of a powdered preparation of the bacteriocin, lacticin 3147, was investigated for the inhibition of Listeria monocytogenes and Bacillus cereus. METHODS AND RESULTS: A 10% solution of reconstituted demineralized whey powder was fermented with Lactococcus lactis DPC3147 for the generation of a lacticin 3147 containing powdered product. A 99.9% reduction in L. monocytogenes numbers occurred in the presence of the lacticin 3147 powder within 2 h in natural yogurt, and an 85% reduction was observed in cottage cheese within the same time frame. Counts of B. cereus were reduced by 80% in soup, in the presence of 1% (w/w) lacticin 3147 powder, within 3 h. CONCLUSIONS: A powdered preparation of lacticin 3147 was effective for the control of Listeria and Bacillus in natural yogurt, cottage cheese and soup. SIGNIFICANCE AND IMPACT OF THE STUDY: The bioactive lacticin 3147 powder may find broad applications for control of Gram-positive pathogens/spoilage bacteria in a range of foods.

Bacillus cereus↗

PubMed2001

Lantibiotics: structure, biosynthesis and mode of action.

The lantibiotics are a group of ribosomally synthesised, post-translationally modified peptides containing unusual amino acids, such as dehydrated and lanthionine residues. This group of bacteriocins has attracted much attention in recent years due to the success of the well characterised lantibiotic, nisin, as a food preservative. Numerous other lantibiotics have since been identified and can be divided into two groups on the basis of their structures, designated type-A and type-B. To date, many of these lantibiotics have undergone extensive characterisation resulting in an advanced understanding of them at both the structural and mechanistic level. This review outlines some of the more recent developments in the biochemistry, genetics and mechanism of action of these peptides.

Alanine↗

PubMed2001

Mutations in the listerial proB gene leading to proline overproduction: effects on salt tolerance and murine infection.

The observed sensitivity of Listeria monocytogenes to the toxic proline analogue L-azetidine-2-carboxylic acid (AZ) suggested that proline synthesis in Listeria may be regulated by feedback inhibition of gamma-glutamyl kinase (GK), the first enzyme of the proline biosynthesis pathway, encoded by the proB gene. Taking advantage of the Epicurian coli mutator strain XL1-Red, we performed random mutagenesis of the recently described proBA operon and generated three independent mutations in the listerial proB homologue, leading to proline overproduction and salt tolerance when expressed in an E. coli (DeltaproBA) background. While each of the mutations (located within a conserved 26-amino-acid region of GK) was shown to confer AZ resistance (AZ(r)) on an L. monocytogenes proBA mutant, listerial transformants failed to exhibit the salt-tolerant phenotype observed in E. coli. Since proline accumulation has previously been linked to the virulence potential of a number of pathogenic bacteria, we analyzed the effect of proline overproduction on Listeria pathogenesis. However, our results suggest that as previously described for proline auxotrophy, proline hyperproduction has no apparent impact on the virulence potential of Listeria.

Amino Acid Sequence↗

PubMed2001

Naturally occurring lactococcal plasmid pAH90 links bacteriophage resistance and mobility functions to a food-grade selectable marker.

The bacteriophage resistance plasmid pAH90 (26,490 bp) is a natural cointegrate plasmid formed via homologous recombination between the type I restriction-modification specificity determinants (hsdS) of two smaller lactococcal plasmids, pAH33 (6,159 bp) and pAH82 (20,331 bp), giving rise to a bacteriophage-insensitive mutant following phage challenge (D. O'Sullivan, D. P. Twomey, A. Coffey, C. Hill, G. F. Fitzgerald, and R. P. Ross, Mol. Microbiol. 36:866-876; 2000). In this communication we provide evidence that the recombination event is favored by phage infection. The entire nucleotide sequence of plasmid pAH90 was determined and found to contain 24 open reading frames (ORFs) responsible for phenotypes which include restriction-modification, phage adsorption inhibition, plasmid replication, cadmium resistance, cobalt transport, and conjugative mobilization. The cadmium resistance property, encoded by the cadA gene, which has an associated regulatory gene (cadC), is of particular interest, as it facilitated the selection of pAH90 in other phage-sensitive lactococci after electroporation. In addition, we report the identification of a group II self-splicing intron bounded by two exons which have the capacity to encode a relaxase implicated in conjugation in gram-positive bacteria. The functionality of this intron was evident by demonstrating splicing in vivo. Given that pAH90 encodes potent phage defense systems which act at different stages in the phage lytic cycle, the linkage of these with a food-grade selectable marker on a replicon that can be mobilized among lactococci has significant potential for natural strain improvement for industrial dairy fermentations which are susceptible to phage inhibition.

Bacterial Proteins↗

PubMed2001

Identification and disruption of the proBA locus in Listeria monocytogenes: role of proline biosynthesis in salt tolerance and murine infection.

Intracellular accumulation of the amino acid proline has previously been linked to the salt tolerance and virulence potential of a number of bacteria. Taking advantage of the proBA mutant Escherichia coli CSH26, we identified a listerial proBA operon coding for enzymes functionally similar to the glutamyl kinase (GK) and glutamylphosphate reductase (GPR) enzyme complex which catalyzes the first and second steps of proline biosynthesis in E. coli. The first gene of the operon, proB, is predicted to encode GK, a 276-residue protein with a calculated molecular mass of 30.03 kDa and pl of 5.2. Distal to the promoter and overlapping the 3' end of proB by 17 bp is proA, which encodes GPR, a 415-residue protein with a calculated molecular mass of 45.50 kDa (pl 5.3). Using this information, we created a chromosomal deletion mutant by allelic exchange which is auxotrophic for proline. This mutant was used to assess the contribution of proline anabolism to osmotolerance and virulence. While inactivation of proBA had no significant effect on virulence in mouse assays (either perorally or intraperitoneally), growth at low (2 to 4% NaCl) and high (>6% NaCl) salt concentrations in complex media was significantly reduced in the absence of efficient proline synthesis. We conclude that while proline biosynthesis plays little, if any, role in the intracellular life cycle and infectious nature of Listeria monocytogenes, it can play an important role in survival in osmolyte-depleted environments of elevated osmolarity.

Aldehyde Oxidoreductases↗

PubMed2001

Analysis of the role of OpuC, an osmolyte transport system, in salt tolerance and virulence potential of Listeria monocytogenes.

The success of Listeria monocytogenes as a food-borne pathogen owes much to its ability to survive a variety of stresses, both in the external environment prior to ingestion and subsequently within the animal host. Growth at high salt concentrations and low temperatures is attributed mainly to the accumulation of organic solutes such as glycine betaine and carnitine. We utilized a novel system for generating chromosomal mutations (based on a lactococcal pWVO1-derived Ori(+) RepA(-) vector, pORI19) to identify a listerial OpuC homologue. Mutating the operon in two strains of L. monocytogenes revealed significant strain variation in the observed activity of OpuC. Radiolabeled osmolyte uptake studies, together with growth experiments in defined media, linked OpuC to carnitine and glycine betaine uptake in Listeria. We also investigated the role of OpuC in contributing to the growth and survival of Listeria in an animal (murine) model of infection. Altering OpuC resulted in a significant reduction in the ability of Listeria to colonize the upper small intestine and cause subsequent systemic infection following peroral inoculation.

ATP-Binding Cassette Transporters↗

PubMed2001

Strategy for manipulation of cheese flora using combinations of lacticin 3147-producing and -resistant cultures.

The aim of the present study was to develop adjunct strains which can grow in the presence of bacteriocin produced by lacticin 3147-producing starters in fermented products such as cheese. A Lactobacillus paracasei subsp. paracasei strain (DPC5336) was isolated from a well-flavored, commercial cheddar cheese and exposed to increasing concentrations (up to 4,100 arbitrary units [AU]/ml) of lantibiotic lacticin 3147. This approach generated a stable, more-resistant variant of the isolate (DPC5337), which was 32 times less sensitive to lacticin 3147 than DPC5336. The performance of DPC5336 was compared to that of DPC5337 as adjunct cultures in two separate trials using either Lactococcus lactis DPC3147 (a natural producer) or L. lactis DPC4275 (a lacticin 3147-producing transconjugant) as the starter. These lacticin 3147-producing starters were previously shown to control adventitious nonstarter lactic acid bacteria in cheddar cheese. Lacticin 3147 was produced and remained stable during ripening, with levels of either 1,280 or 640 AU/g detected after 6 months of ripening. The more-resistant adjunct culture survived and grew in the presence of the bacteriocin in each trial, reaching levels of 10(7) CFU/g during ripening, in contrast to the sensitive strain, which was present at levels 100- to 1,000-fold lower. Furthermore, randomly amplified polymorphic DNA-PCR was employed to demonstrate that the resistant adjunct strain comprised the dominant microflora in the test cheeses during ripening.

Bacterial Proteins↗