Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “BACTERIOCINS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
PubMed2006

Bacteriocin activity by Lactobacillus curvatus CWBI-B28 to inactivate Listeria monocytogenes in cold-smoked salmon during 4 degrees C storage.

The inhibition effectiveness of a bacteriocin produced by Lactobacillus curvatus CWBI-B28 against Listeria monocytogenes was investigated in cold-smoked salmon during storage at 4 degrees C. Three bacteriocin-based strategies for the control of L. monocytogenes in foods (i.e., producing bacteriocin in situ, spraying with partially purified bacteriocin, and packaging in bacteriocin-coated plastic film), plus a newly developed method that uses cell-adsorbed bacteriocin (i.e., a suspension of producer cells on which maximum bacteriocin has been immobilized by pH adjustments), were assessed. Although all the approaches inactivated L. monocytogenes in cold-smoked salmon, various efficacy levels were observed. The behavior of L. monocytogenes was similar in samples treated with either partially purified bacteriocin or in situ bacteriocin production. In both of these cases, the counts of the pathogen declined to below the detectable limit of 0.7 log CFU/cm2 within the first week, but a approximately 0.95- and 1.3-log increase, respectively, occurred after day 14. The bioactive packaging film resulted in a slower inactivation of the pathogen but prevented any subsequent increase in the CFU throughout 22 days of storage at 4 degrees C. Application of the cell-adsorbed bacteriocin was shown to be the most effective means, as it resulted in a complete inactivation of the pathogen within 3 days, and no increase in Listeria counts occurred up to 22 days.

Animals↗
PubMed2001

Bacteriocins: safe, natural antimicrobials for food preservation.

Bacteriocins are antibacterial proteins produced by bacteria that kill or inhibit the growth of other bacteria. Many lactic acid bacteria (LAB) produce a high diversity of different bacteriocins. Though these bacteriocins are produced by LAB found in numerous fermented and non-fermented foods, nisin is currently the only bacteriocin widely used as a food preservative. Many bacteriocins have been characterized biochemically and genetically, and though there is a basic understanding of their structure-function, biosynthesis, and mode of action, many aspects of these compounds are still unknown. This article gives an overview of bacteriocin applications, and differentiates bacteriocins from antibiotics. A comparison of the synthesis. mode of action, resistance and safety of the two types of molecules is covered. Toxicity data exist for only a few bacteriocins, but research and their long-time intentional use strongly suggest that bacteriocins can be safely used.

Anti-Bacterial Agents↗
PubMed2003

The stimulating effect of a harsh environment on the bacteriocin activity by Enterococcus faecium RZS C5 and dependency on the environmental stress factor used.

Bacteriocin production by Enterococcus faecium RZS C5 occurs in a growth-associated way but is generally switched off in the very early growth phase. The influence of environmental stress on the bacteriocin production kinetics by E. faecium RZS C5 was analysed at a controlled temperature of 35 degrees C and constant pH 6.5. The effect of environmental stress on bacteriocin production was depending on the type of stress applied. Oxidative stress did not interfere with cell growth or bacteriocin activity. In contrast, salt stress decreased both the cell growth and the specific bacteriocin production. Nevertheless, moderate levels of sodium chloride improved bacteriocin activity because they increased the biomass concentration at which bacteriocin production was switched off. Environmental stress due to limitations in sugar or complex nutrients did not affect the early shut-off mechanism or the specific bacteriocin production. However, bacteriocin stability decreased or increased at low levels of sugar or complex nutrients, respectively.

Bacteriocins↗
PubMed2002

Influence of growth conditions on the production of a nisin-like bacteriocin by Lactococcus lactis subsp. lactis A164 isolated from kimchi.

The influence of growth parameters on the fermentative production of a nisin-like bacteriocin by Lactococcus lactis subsp. lactis A164 isolated from kimchi was studied. The bacteriocin production was greatly affected by carbon and nitrogen sources. Strain A164 produced at least 4-fold greater bacteriocin in M17 broth supplemented with lactose than other carbon sources. The amount of 3% yeast extract was found to be the optimal organic nitrogen source. While the maximum biomass was obtained at 37 degrees C, the optimal temperature for the bacteriocin production was 30 degrees C. The bacteriocin production was also affected by pH of the culture broth. The optimal pH for growth and bacteriocin production was 6.0. Although the cell growth at pH 6.0 was nearly the same level at pH 5.5 and 6.5, the greater bacteriocin activity was observed at pH 6.0. Exponential growth took place only during an initial period of the cultivation, and then linear growth was observed. Linear growth rates increased from 0.160 g(DCW) x l(-1) x h(-1) to 0.245 g(DCW) x l(-1) x h(-1) with increases in lactose concentrations from 0.5 to 3.0%. Maximum biomass was also increased from 1.88 g(DCW) x l(-1) to 4.29 g(DCW) x l(-1). However, increase in lactose concentration did not prolong the active growth phase. After 20 h cultivation, cell growth stopped regardless of lactose concentration. Production of the bacteriocin showed primary metabolic kinetics. However, bacteriocin yield based on cell mass increased greatly during the late growth phase. A maximum activity of 131x10(3) AU x ml(-1) was obtained at early stationary growth phase (20 h) during the batch fermentation in M17L broth (3.0% lactose) at 30 degrees C and pH 6.0.

Bacteriocins↗
PubMedDate not supplied

Potential of bacteriocin-producing lactic acid bacteria for improvements in food safety and quality.

Lactic acid bacteria (LAB) have been used for centuries in the fermentation of a variety of dairy products. The preservative ability of LAB in foods is attributed to the production of anti-microbial metabolites including organic acids and bacteriocins. Bacteriocins generally exert their anti-microbial action by interfering with the cell wall or the membrane of target organisms, either by inhibiting cell wall biosynthesis or causing pore formation, subsequently resulting in death. The incorporation of bacteriocins as a biopreservative ingredient into model food systems has been studied extensively and has been shown to be effective in the control of pathogenic and spoilage microorganisms. However, a more practical and economic option of incorporating bacteriocins into foods can be the direct addition of bacteriocin-producing cultures into food. This paper presents an overview of the potential for using bacteriocin-producing LAB in foods for the improvement of the safety and quality of the final product. It describes the different genera of LAB with potential as biopreservatives, and presents an up-to-date classification system for the bacteriocins they produce. While the problems associated with the use of some bacteriocin-producing cultures in certain foods are elucidated, so also are the situations in which incorporation of the bacteriocin-producer into model food systems have been shown to be very effective.

Bacteria↗
PubMed2002

Proteolysis in Hispánico cheese manufactured using a mesophilic starter, a thermophilic starter, and bacteriocin-producing Lactococcus lactis subsp. lactis INIA 415 adjunct culture.

Lactococcus lactis subsp. lactis INIA 415, a strain harboring the structural genes of bacteriocins nisin Z and lacticin 481, was used as adjunct culture in the manufacture of Hispánico cheese with a mesophilic starter and a thermophilic starter of high aminopeptidase activity. Addition of the bacteriocin producer promoted early lysis of mesophilic and thermophilic starter bacteria. Extracellular aminopeptidase activity in 7-day-old cheese made using mesophilic and thermophilic starters plus bacteriocin producer was 3.0-fold the level reached in cheese made without the bacteriocin producer. Proteolysis in cheese made with mesophilic and thermophilic starters plus bacteriocin-producing adjunct culture after 25 days of ripening was 1.5-fold the level reached in cheese made without the bacteriocin producer, and the level of total free amino acids was 2.9-fold the level found in cheese made without the bacteriocin producer. Cheese made with mesophilic and thermophilic starters plus bacteriocin producer received the highest scores for flavor quality and flavor intensity and reached in 25 days the flavor intensity score of a 75-day-old cheese made without the bacteriocin producer.

Amino Acids↗
PubMed2002

Production of class II bacteriocins by lactic acid bacteria; an example of biological warfare and communication.

Lactic acid bacteria (LAB) fight competing Gram-positive microorganisms by secreting anti-microbial peptides called bacteriocins. Peptide bacteriocins are usually divided into lantibiotics (class I) and non-lantibiotics (class II), the latter being the main topic of this review. During the past decade many of these bacteriocins have been isolated and characterized, and elements of the genetic mechanisms behind bacteriocin production have been unravelled. Bacteriocins often have a narrow inhibitory spectrum, and are normally most active towards closely related bacteria likely to occur in the same ecological niche. Lactic acid bacteria seem to compensate for these narrow inhibitory spectra by producing several bacteriocins belonging to different classes and having different inhibitory spectra. The latter may also help in counteracting the possible development of resistance mechanisms in target organisms. In many strains, bacteriocin production is controlled in a cell-density dependent manner, using a secreted peptide-pheromone for quorum-sensing. The sensing of its own growth, which is likely to be comparable to that of related species, enables the producing organism to switch on bacteriocin production at times when competition for nutrients is likely to become more severe. Although today a lot is known about LAB bacteriocins and the regulation of their production, several fundamental questions remain to be solved. These include questions regarding mechanisms of immunity and resistance, as well as the molecular basis of target-cell specificity.

Amino Acid Sequence↗
PubMed2002

Widespread distribution of the bacteriocin-producing lactic acid cocci in Miso-paste products.

AIMS: A survey was conducted on the ecological distribution of bacteriocin-producing lactic acid bacteria in Miso-pastes, a typical fermented food in Japan. METHODS AND RESULTS Nine Miso-pastes were sampled for isolation of bacteriocin-producers. Almost all isolated enterococcal strains produced bacteriocins but no isolated tetragenococci did so. The bacteriocin-producing isolates were divided into nine groups by phenotypic tests. As the phenotypic characters were highly diverse, these strains could not be identified to species level on the basis of their phenotypes. The nine representative strains from each group were identified by 16S rRNA analysis. These bacteriocin-producers with one exception (Lactococcus sp.) were identified as strains of the Enterococcus faecium 'species group'. The bacteriocins of the nine strains were classified into five types according to their antibacterial spectral patterns and their SDS-PAGE profiles. The bacteriocins inhibited undesirable bacteria in Miso-pastes, such as Bacillus subtilis, but did not inhibit the useful Tetragenococcus halophila. CONCLUSIONS: The bacteriocin-producing lactic acid cocci were widespread at high frequencies in Miso-pastes. They were considered to play an important role in preventing the growth of undesirable bacteria. SIGNIFICANCE AND IMPACT OF THE STUDY: This study suggests that bacteriocin-producers act effectively as safe biopreservatives and may contribute to the biopreservation in Miso-pastes.

Bacteriocins↗
PubMed2002

Antagonistic interactions amongst bacteriocin-producing enteric bacteria in dual species biofilms.

AIMS: The objective of this study was to investigate the antagonistic interactions between bacteriocin-producing enteric bacteria in dual species biofilms and the interspecies interactions correlated with sensitivity to biocides. METHODS AND RESULTS: When compared with their single species counterparts, the dual species biofilms formed by bacteriocin-producing strains exhibited a decrease in biofilm size and an increase in sensitivity to the antimicrobial agents hypochlorite, triclosan and benzalkonium chloride. The five dual species biofilms studied all resulted in biofilms containing a mixture of the two strains. This was attributed to the spatial distribution of cells within the biofilm, with each strain forming its own microcolonies. The production of a bacteriocin also gave a strain a competitive advantage when interacting with a bacteriocin-sensitive strain within a biofilm, both in gaining a foothold in a new environment and in preventing the colonization of a potential competitor into a pre-established biofilm. CONCLUSIONS: It was concluded that bacteriocins might be used specifically for interacting with competing strains within a biofilm, as opposed to a planktonic, environment. SIGNIFICANCE AND IMPACT OF THE STUDY: Unlike planktonically grown bacteriocin-producing populations, where one strain will always be out-competed, bacteriocin-producing and bacteriocin-sensitive strains can coexist in biofilm communities, clearly demonstrating major differences between biofilm and planktonic competition. This paper highlights the importance of bacteriocin production in the development of biofilm communities.

Animals↗
PubMed2001

Bacteriocin susceptibility of Gardnerella vaginalis and its relationship to biotype, genotype, and metronidazole susceptibility.

OBJECTIVE: Our purpose was to investigate the bacteriocin susceptibility of Gardnerella vaginalis and its relationship to biotype, genotype, and resistance to metronidazole. STUDY DESIGN: Bacteriocin susceptibility of 36 G vaginalis clinical isolates was tested against a vaginal strain of Lactobacillus acidophilus by a growth-inhibition method. The relationship to biotype, genotype, and resistance to metronidazole were analyzed by the chi2 test and Fisher exact test. RESULTS: Eight G vaginalis strains (22%) were bacteriocin-resistant. Biotypes 5 and 7 were found to be the most frequent among these resistant strains. Eight (42%) of the 19 isolates classified as biotype 5, 6, or 7 were bacteriocin-resistant compared with none of the isolates that were classified as other biotypes (P <.01). Biotype 5 was found in higher prevalence among the isolates resistant to bacteriocin (62%) than among the susceptible isolates (14%) (P =.01). Genotype B was found more frequently among the bacteriocin-resistant strains, but this finding was not statistically significant (P =.71). Seven (88%) bacteriocin-resistant strains were also resistant to metronidazole. CONCLUSION: An association between biotype and an increased resistance to bacteriocin was found. The ability of G vaginalis to resist the antibacterial activity of Lactobacillus bacteriocin may be a pivotal factor in understanding bacterial vaginosis.

Anti-Bacterial Agents↗
PubMed2006

Bacteriocins reduce Campylobacter colonization and alter gut morphology in turkey poults.

Campylobacter is a leading cause of food-borne illness in the United States. Recent evidence has demonstrated that bacteriocins produced by Bacillus circulans and Paenibacillus polymyxa reduce cecal Campylobacter colonization in broiler chickens infected with Campylobacter jejuni. As Campylobacter coli is the most prevalent Campylobacter isolate recovered in turkeys, the objectives of the present study were to evaluate the efficacy of these bacteriocins against C. coli colonization and their influence on the gastrointestinal architecture of young turkeys. In 3 separate trials, a total of 135 day-of-hatch poults (n = 45/trial) were orally challenged on d 3 with approximately 10(6) cfu of a mixture of 3 C. coli isolates. Immediately before bacteriocin treatment (d 10), cecal Campylobacter concentrations averaged 1.1 x 10(7) cfu/ g of cecal contents (n = 15/trial). On d 10 to 12 posthatch, 2 bacteriocin treatment groups were given free access to feed supplemented with purified, microencapsulated bacteriocins, whereas the positive control treatment group had access to untreated feed (n = 10/treatment group per trial). At the end of the 3-d dosing period, ceca and duodenal loops were collected for analysis. In each of the 3 separate trials, treatment with bacteriocin eliminated detectable ceca Campylobacter concentrations (detection limit, 1 x 10(2) cfu/g of cecal contents) vs. controls (1.0 x 106 cfu of Campylobacter/g of cecal contents). Duodenum crypt depth and goblet cell numbers were also reduced in turkeys treated with either bacteriocin vs. controls (P < 0.05). The dynamic reduction in crypt depth and goblet cell density in turkeys dosed with bacteriocin may provide clues to how bacteriocins inhibit enteric Campylobacter.

Animal Feed↗
PubMed1997

Selection and fitness in bacteriocin-producing bacteria.

Bacteriocins are proteinaceous anticompetitor molecules produced by bacteria against closely related species. A number of theoretical models have been used to explain experimental data that indicate high polymorphisms among bacteriocins and a frequency-dependent nature of selection for bacteriocin-producing strains. The majority of these experimental data were, however, obtained from investigations into the colicin group of bacteriocins produced by Gram-negative bacteria. The conclusions drawn from these models have been extrapolated to other bacteriocins and allelopathic compounds in general. Examination of more recent experimental investigations into the bacteriocins of Gram-positive bacteria indicate a lower degree of polymorphism and a less frequency dependent mode of selection among these strains them among the colicin-producing strains. Here we examine these contradictions in the light of the assumptions and conclusions of the theoretical models and reported data. We show that fitness costs as indicated by decreased relative maximum growth rate associated with bacteriocin production may be much lower in many cases than is assumed in the present models. A lower fitness cost associated with bacteriocin production adequately explains the newer data from Gram-positive bacteria cited here, and indicates that extrapolation of existing models to all bacteriocins and other allelopathic compounds is not appropriate.

Bacteriocins↗
PubMed1992

Purification and amino acid sequence of a bacteriocin produced by Pediococcus acidilactici.

A bacteriocin produced by Pediococcus acidilactici has been purified to homogeneity by a rapid and simple four-step purification procedure which includes ammonium sulphate precipitation, chromatography with a cation-exchanger and Octyl Sepharose, and reverse-phase chromatography. The purification resulted in an approximately 80,000-fold increase in the specific activity and about a 6-fold increase in the total activity. The amino acid composition and sequencing data indicated that the bacteriocin contained 43-44 amino acid residues. The predicted M(r) and isolectric point of the bacteriocin are about 4600 and 8.6, respectively. Comparing the amino acid sequence of this bacteriocin with the sequences of leucocin A-UAL 187, sakacin P and curvacin A (bacteriocins produced by Leuconostoc gelidum, Lactobacillus sake and Lactobacillus curvatus, respectively) revealed that all four bacteriocins had in their N-terminal region the sequence Tyr-Gly-Asn-Gly-Val-Xaa-Cys, indicating that this concensus sequence is of fundamental importance for this group of bacteriocins. The bacteriocin from P. acidilactici and sakacin P were very similar, having at least 25 common amino acid residues. The sequence similarity was greatest in the N-terminal half of the molecules--17 of the first 19 residues were common--indicating the fundamental importance of this region. Leucocin A-UAL 187 and curvacin A had, respectively, at least 16 and 13 amino acid residues in common with the bacteriocin from P. acidilactici.

Amino Acid Sequence↗
PubMed2002

Comparative studies of immunity proteins of pediocin-like bacteriocins.

Genes encoding pediocin-like bacteriocins are usually co-transcribed with a gene encoding a cognate immunity protein. To investigate the functionality and specificity of immunity proteins, immunity genes belonging to the bacteriocins curvacin A, enterocin A, enterocin P, leucocin A, pediocin PA-1 and sakacin P, as well as a putative immunity gene, orfY, were expressed in three bacteriocin-sensitive lactic acid bacteria (Lactobacillus sake, Carnobacterium piscicola and Enterococcus faecalis). The transformed indicator strains, each containing one of the immunity genes, were tested for sensitivity towards seven different purified bacteriocins (curvacin A, enterocin A, enterocin P, leucocin A, leucocin C, pediocin PA-1 and sakacin P). Cross-immunity was observed almost exclusively in situations where either the bacteriocins or the immunity proteins belonged to the same sequence-based subgroup. In a few cases, the functionality of immunity proteins was strain-dependent; e.g. the leucocin A immunity gene provided immunity to enterocin A, pediocin PA-1 and leucocin A in Ent. faecalis, whereas in the other two indicators, this gene provided immunity to leucocin A only. The orfY gene, which is transcribed without a cognate bacteriocin, was shown to encode a functional immunity protein that expands the bacteriocin resistance of the strain possessing this gene. The results show that the bacteriocin sensitivity of a lactic acid bacterium strain can depend on (1) the presence of immunity genes in connection with its own bacteriocin production, (2) the presence of extra immunity genes and (3) more general properties of the strain such as the membrane composition or the presence of receptors.

Amino Acid Sequence↗
PubMed1981

Effects of a bacteriocin from Mycobacterium smegmatis on BALB/3T3 and simian virus 40-transformed BALB/c mouse cells.

The effects of a bacteriocin from Mycobacterium smegmatis ATCC 14468 on simian virus 40-transformed BALB/c mouse cells (mKS-A TU-7 cells) and nontransformed BALB/3T3 cells originating from the BALB/c mouse strain were studied. The percentage of nigrosin-unstained (viable) cells in the bacteriocin-treated mKS-A TU-7 cells decreased time-dependently with an increase in the bacteriocin activity. There was a time-dependent decrease in the bacteriocin activity after treatment with the cell membrane preparation from mKS-A TU-7 cells. There was no apparent effect of the bacteriocin on the viability of nontransformed BALB/3T3 cells. Wheat germ agglutinin blocked the toxic effect of bacteriocin on mKS-A TU-7 cells. These results indicate that the higher sensitivity and binding capacity of the tumor cells to the bacteriocin is probably due to the presence of a large amount of N-acetyl-glucosamine or closely related sugar residues with a high affinity for bacteriocin, as compared with normal cells. The bacteriocin produced morphological alterations and inhibition of synthesis of ribonucleic acid, deoxyribonucleic acid and protein in the transformed but not in the nontransformed cells.

Animals↗
PubMed2005

Durancin L28-1A, a new bacteriocin from Enterococcus durans L28-1, isolated from soil.

AIMS: To isolate, characterize and identify bacteriocins from lactic acid bacteria in soil. METHODS AND RESULTS: Thirty-four acid-producing bacteria were isolated from 87 soil samples. Antibacterial activities were detected, and one strain, L28-1 produced a bacteriocin that was active against some Gram-positive bacteria. L28-1 was identified as Enterococcus durans by 16S rDNA sequence analysis and API50CHL. This bacteriocin did not lose its activity after autoclaving (121 degrees C for 15 min), but was inactivated by protease K. The bacteriocin was purified by hydrophobic column chromatography, and Sep-Pak C(18). Tricine sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the partially purified bacteriocin contained numerous protein bands. Two bands that displayed antibacterial activities were c. 3.4 and 2.5 kDa in size. In this work, the 3.4-kDa bacteriocin was analysed with N-terminal amino acid and DNA sequencing and matrix-assisted laser desorption ionization-time of flight mass spectrometry analysis. The results indicated that the 3.4-kDa bacteriocin of Ent. durans L28-1 is a new natural enterocin variant. CONCLUSIONS: Enterococcus durans L28-1 produced a new bacteriocin. SIGNIFICANCE AND IMPACT OF THE STUDY: This study reports a novel bacteriocin that is produced by Ent. durans that has potential for use as a food preservative.

Amino Acid Sequence↗
PubMed2006

Bac 32, a novel bacteriocin widely disseminated among clinical isolates of Enterococcus faecium.

A total of 636 vancomycin-resistant Enterococcus faecium (VRE) isolates that had been obtained between 1994 and 1999 from the Medical School Hospital of the University of Michigan, Ann Arbor, were tested for bacteriocin production. Two hundred seventy-seven (44%) of the strains were bacteriocinogenic; and 193 of these exhibited activity against Enterococcus faecium, Enterococcus hirae, and Enterococcus durans. Strain VRE200 harbors the highly efficient conjugative gentamicin resistance plasmid pG200 (70 kb) and bacteriocin plasmid pTI1 (12.5 kb). The bacteriocin encoded on pTI1 was designated bacteriocin 32 (Bac 32). Bacteriocin 32 was active against E. faecium, E. hirae, and E. durans but showed no activity against Listeria monocytogenes. The Bac 32 genetic locus consists of a bacteriocin gene (bacA) and an immunity gene (bacB). Neither of these genes showed significant homology to any known bacteriocin determinants. The deduced bacA product is 89 amino acids in length, with a putative signal peptide of 19 amino acids at the N terminus. The bacB gene encodes a deduced 55-amino-acid protein without a signal sequence. One hundred eighty-nine strains (97.9%) of the 193 strains with activity against the 3 test enterococcal strains gave rise to the expected specific PCR product with a primer specific for bacA, indicating that there is a high incidence of Bac 32 production among VRE clinical isolates. Data from Southern analyses of plasmid DNA from 189 of the Bac 32-producing strains with a plasmid pTI1-specific probe suggested that 137 (72.5%) of the strains harbored a pTI1-type plasmid. Bac 32 or Bac 32-type bacteriocin activity and the determinant genes were also identified in 22 (39.3%) of a total of 56 vancomycin-sensitive E. faecium clinical isolates, which suggests that this bacteriocin is widely disseminated among E. faecium strains.

Amino Acid Sequence↗
PubMed1972

Epidemiological differentiation of Serratia marcescens: typing by bacteriocin sensitivity.

Strains of Serratia marcescens were compared and differentiated by a new method. Bacteriocin lysates were prepared from mitomycin-induced S. marcescens and added to lawns of test strains. From 100 bacteriocin producers, 12 were chosen with the aid of computer analysis as the most useful in differentiation. Uniform drops of the 12 standard bacteriocins were added simultaneously with a bacteriocin-bacteriophage dropper to each strain to be typed. All 93 strains of S. marcescens tested were typable and were differentiated into 79 different sensitivity patterns. One pattern had three strains, 12 patterns had two strains each, and 66 patterns had only one strain. The bacteriocins also inhibited Shigella, Klebsiella, and Enterobacter, but no other Enterobacteriaceae. Bacteriocin sensitivity was less stable as an epidemiological marker than bacteriocin production. Several colonial mutants had sensitivity patterns different from the wild types, but most mutants were identical. In three different instances when cross-infection had been shown by other methods, bacteriocin sensitivity also gave the correct epidemiological results. Until the significance and frequency of genetic variations are known, a more stable epidemiological technique should be used in conjunction with bacteriocin sensitivity.

Bacteriocins↗