In vitro antibacterial activity of laboratory grown culture of Spirulina platensis

The hexane, ethyl acetate, dichloromethane, methanol extracts and spent media (extracellular substances) were tested in vitro for their antibacterial activity for which one Gram-positive bacterium (Staphylococcus aureus) and four Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, and Klebsiella pneumoniae) were used as test organisms. The methanol extract showed more potent activity than other organic extracts, spent medium of the culture exhibited little activity against E. coli only. No inhibitory effect was found against Klebsiella pneumoniae.The broth microdilution assay gave minimum inhibitory concentrations (MIC) values ranging from 1 to 512 μg/ml. The MIC of methanol extract against S. aureus and E. coli were 128 μg/ml and 256 μg/ml, respectively.     

Growth inhibition by glucose oxidase system of enterotoxic Escherichia coli and Salmonella derby: in vitro studies

The antibacterial effect of different glucose oxidase (GOX)/glucose combinations was studied on two food-poisoning organisms, enterotoxic Escherichia coli PM 015 and Salmonella derby BP 177. Growth of E. coli in nutrient broth (NB) was clearly inhibited by 4.0 mg/ml glucose after 24 h when combined with 2.0 U/ml GOX and after 48 h when combined with 0.5 or 1.0 U/ml GOX. Salmonella derby was more resistant than E. coli, but showed clear growth inhibition only after 48 h when inoculated in tubes where 2 mg glucose/ml and 2 U GOX/ml (or 4 mg glucose/ml and 1 U GOX/ml) were combined. In order to understand if the enzyme effect on microbial growth can be attributed to hydrogen peroxide or to pH decrease as a result of the production of gluconic acid, catalase (CAT) was added to GOX/glucose system. Since CAT decomposes H₂O₂ to H₂O and O₂, the antibacterial effect was ascribed to a pH decrease as a result of gluconic acid in the system.     

Differential effects of catecholamines on in vitro growth of pathogenic bacteria

Supplementation of minimal medium inoculated with bacterial cultures with norepinephrine, epinephrine, dopamine, or isoproterenol resulted in marked increases in growth compared to controls. Norepinephrine and dopamine had the greatest enhancing effects on growth of cultures of Pseudomonas aeruginosa and Klebsiella pneumoniae, while epinephrine and isoproterenol also enhanced growth to a lesser extent. The growth of Escherichia coli in the presence of norepinephrine was greater than growth in the presence of the three other neurochemicals used in the study. Growth of Staphylococcus aureus was also enhanced in the presence of norepinephrine, but not to the same degree as was the growth of gram negative bacteria. Addition of culture supernatants from E. coli cultures that had been grown in the presence of norepinephrine was able to enhance the growth of K. pneumoniae. Addition of the culture supernatant fluid culture from E. coli cultures that had been grown in the presence of norepinephrine did not enhance growth of P. aeruginosa or S. aureus. Culture supernatant fluids from bacteria other than E. coli grown in the presence of norepinephrine were not able to enhance the growth of any bacteria tested. The results suggest that catecholamines can enhance growth of pathogenic bacteria, which may contribute to development of pathogenesis; however, there is no uniform effect of catecholamines on bacterial growth.     

Antibacterial action of a heat-stable form of L-amino acid oxidase isolated from king cobra (Ophiophagus hannah) venom

The major l-amino acid oxidase (LAAO, EC 1.4.3.2) of king cobra (Ophiophagus hannah) venom is known to be an unusual form of snake venom LAAO as it possesses unique structural features and unusual thermal stability. The antibacterial effects of king cobra venom LAAO were tested against several strains of clinical isolates including Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli using broth microdilution assay. For comparison, the antibacterial effects of several antibiotics (cefotaxime, kanamycin, tetracycline, vancomycin and penicillin) were also examined using the same conditions. King cobra venom LAAO was very effective in inhibiting the two Gram-positive bacteria (S. aureus and S. epidermidis) tested, with minimum inhibitory concentration (MIC) of 0.78μg/mL (0.006μM) and 1.56μg/mL (0.012μM) against S. aureus and S. epidermidis, respectively. The MICs are comparable to the MICs of the antibiotics tested, on a weight basis. However, the LAAO was only moderately effective against three Gram-negative bacteria tested (P. aeruginosa, K. pneumoniae and E. coli), with MIC ranges from 25 to 50μg/mL (0.2-0.4μM). Catalase at the concentration of 1mg/mL abolished the antibacterial effect of LAAO, indicating that the antibacterial effect of the enzyme involves generation of hydrogen peroxide. Binding studies indicated that king cobra venom LAAO binds strongly to the Gram-positive S. aureus and S. epidermidis, but less strongly to the Gram-negative E. coli and P. aeruginosa, indicating that specific binding to bacteria is important for the potent antibacterial activity of the enzyme.     

Synthesis and antimicrobial activity of small cationic amphipathic aminobenzamide marine natural product mimics and evaluation of relevance against clinical isolates including ESBL–CARBA producing multi-resistant bacteria

A library of small aminobenzamide derivatives was synthesised to explore a cationic amphipathic motif found in marine natural antimicrobials. The most potent compound E23 displayed minimal inhibitory concentrations (MICs) of 0.5–2 μg/ml against several Gram-positive bacterial strains, including methicillin resistant Staphylococcus epidermidis (MRSE). E23 was also potent against 275 clinical isolates including Staphylococcus aureus, Enterococcus spp., Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae, as well as methicillin-resistant S. aureus (MRSA), vancomycin-resistant enterococci (VRE), and ESBL–CARBA producing multi-resistant Gram-negative bacteria. The study demonstrates how structural motifs found in marine natural antimicrobials can be a valuable source for making novel antimicrobial lead-compounds.     

Studies on antimicrobial activity, in vitro, of Physalis angulata L. (Solanaceae) fraction and physalin B bringing out the importance of assay determination

Complex physalin metabolites present in the capsules of the fruit of Physalis angulata L. have been isolated and submitted to a series of assays of antimicrobial activity against Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 29213, S. aureus ATCC 25923, S. aureus ATCC 6538P, Neisseria gonorrhoeae ATCC 49226, Escherichia coli ATCC 8739; E. coli ATCC 25922, Candida albicans ATCC 10231 applying different methodologies such as: bioautography, dilution broth, dilution agar, and agar diffusion techniques. A mixture of physalins (pool) containing physalins B, D, F, G inhibit S. aureus ATCC 29213, S. aureus ATCC 25923, S. aureus ATCC 6538P, and N. gonorrhoeae ATCC 49226 at a concentration of 200 mg/microl, using agar dilution assays. The mixture was inactive against P. aeruginosa ATCC27853, E. coli ATCC 8739; E. coli ATCC 25922, C. albicans ATCC 10231 when applying bioautography assays. Physalin B (200 microg/ml) by the agar diffusion assay inhibited S. aureus ATCC 6538P by +/- 85%; and may be considered responsible for the antimicrobial activity.     

Growth kinetics of coliform bacteria under conditions relevant to drinking water distribution systems.

The growth of environmental and clinical coliform bacteria under conditions typical of drinking water distribution systems was examined. Four coliforms (Klebsiella pneumoniae, Escherichia coli, Enterobacter aerogenes, and Enterobacter cloacae) were isolated from an operating drinking water system for study; an enterotoxigenic E. coli strain and clinical isolates of K. pneumoniae and E. coli were also used. All but one of the coliforms tested were capable of growth in unsupplemented mineral salts medium; the environmental isolates had greater specific growth rates than did the clinical isolates. This trend was maintained when the organisms were grown with low levels (less than 1 mg liter-1) of yeast extract. The environmental K. pneumoniae isolate had a greater yield, higher specific growth rates, and a lower Ks value than the other organisms. The environmental E. coli and the enterotoxigenic E. coli strains had comparable yield, growth rate, and Ks values to those of the environmental K. pneumoniae strain, and all three showed significantly more successful growth than the clinical isolates. The environmental coliforms also grew well at low temperatures on low concentrations of yeast extract. Unsupplemented distribution water from the collaborating utility supported the growth of the environmental isolates. Growth of the K. pneumoniae water isolate was stimulated by the addition of autoclaved biofilm but not by tubercle material. These findings indicate that growth of environmental coliforms is possible under the conditions found in operating municipal drinking water systems and that these bacteria could be used in tests to determine assimilable organic carbon in potable water.     

Enhancing Effect of Alkalinization of the Medium on the Activity of Erythromycin Against Gram-negative Bacteria

The antibacterial activity of erythromycin was markedly enhanced by alkalinization of the culture medium or urine within the clinical range (pH 6.0 to 8.2). This effect was demonstrated against recent isolates of Escherichia coli, Klebsiella pneumoniae, Enterobacter sp., and Pseudomonas aeruginosa, as well as against Staphylococcus aureus and Streptococcus faecalis. The urine of normal volunteers was made alkaline by ingestion of sodium bicarbonate or acetazolamide (Diamox) during administration of 1.0 g of erythromycin every 8 hr; such urine was capable of inhibiting E. coli and K. pneumoniae even when diluted up to (in one instance) 128 times with broth of the same pH as the urine. Undiluted urine of the same subjects, without alkalinization, was seldom capable of inhibiting these organisms. The range of pH (6.6 to 8.6) over which the antibacterial effect was enhanced coincided with that over which there was decreasing ionization of a basic group.     

Growth kinetics of coliform bacteria under conditions relevant to drinking water distribution systems.

The growth of environmental and clinical coliform bacteria under conditions typical of drinking water distribution systems was examined. Four coliforms (Klebsiella pneumoniae, Escherichia coli, Enterobacter aerogenes, and Enterobacter cloacae) were isolated from an operating drinking water system for study; an enterotoxigenic E. coli strain and clinical isolates of K. pneumoniae and E. coli were also used. All but one of the coliforms tested were capable of growth in unsupplemented mineral salts medium; the environmental isolates had greater specific growth rates than did the clinical isolates. This trend was maintained when the organisms were grown with low levels (less than 1 mg liter-1) of yeast extract. The environmental K. pneumoniae isolate had a greater yield, higher specific growth rates, and a lower Ks value than the other organisms. The environmental E. coli and the enterotoxigenic E. coli strains had comparable yield, growth rate, and Ks values to those of the environmental K. pneumoniae strain, and all three showed significantly more successful growth than the clinical isolates. The environmental coliforms also grew well at low temperatures on low concentrations of yeast extract. Unsupplemented distribution water from the collaborating utility supported the growth of the environmental isolates. Growth of the K. pneumoniae water isolate was stimulated by the addition of autoclaved biofilm but not by tubercle material. These findings indicate that growth of environmental coliforms is possible under the conditions found in operating municipal drinking water systems and that these bacteria could be used in tests to determine assimilable organic carbon in potable water.     

Antibiotic susceptibility and genotype patterns of Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa isolated from urinary tract infected patients

Thirty nine isolates of Escherichia coli, twenty two isolates of Klebsiella pneumoniae and sixteen isolates of Pseudomonas aeruginosa isolated from urinary tract infected patients were analyzed by antimicrobial susceptibility typing and random amplified polymorphic DNA (RAPD)-PCR. Antibiotic susceptibility testing was carried out by microdilution and E Test methods. From the antibiotic susceptibility, ten patterns were recorded (four for E. coli, three for K. pneumoniae and three for P. aeruginosa respectively). Furthermore, genotyping showed seventeen RAPD patterns (seven for E. coli, five for K. pneumoniae and five for P. aeruginosa respectively). In this study, differentiation of strains of E. coli, K. pneumoniae and P. aeruginosa from nosocomial infection was possible with the use of RAPD.     

Confirmation of Escherichia coli and its distinction from Klebsiella species by gas and indole formation at 44 and 44.5 degrees C

AIMS: In the enumeration of coliform bacteria, confirmation of Escherichia coli has been based upon gas and indole production at the elevated incubation temperature. The test for gas production has recently been questioned. The aim of this study was to investigate the impact of gas production test on the reliability of confirmation of E. coli. METHODS AND RESULTS: The impact of several media on growth, gas and/or indole formation was tested at 44 and 44.5 degrees C using 547 environmental isolates. These were mainly E. coli, Klebsiella pneumoniae, K. oxytoca and Enterobacter cloacae strains. Another set of 250 faecal and environmental klebsiellae were tested for their maximum temperature for growth (Tmax) and for gas formation. Escherichia coli and even K. pneumoniae grew well in all the media, but gas production was more dependent on the medium used. Growth of the mainly gas negative Ent. cloacae and K. oxytoca strains was still more sensitive to the medium and incubation conditions. Tryptophan salt broth was the most productive medium for the indole test, followed by lauryl tryptose mannitole and tryptone mannitol ricinoleate broth (TRM). Tmax of K. oxytoca was clearly lower than Tmax of K. pneumoniae but a rather high fraction of its isolates produced indole at 44.5 degrees C. CONCLUSIONS: False-positive E. coli confirmation is possible if gas production is not tested for and the confirmation is based on indole test only. SIGNIFICANCE AND IMPACT OF THE STUDY: Erroneous positive results on routine analysis for E. coli can occur.     

Production of Bacteriocin ST33LD, Produced by Leuconostoc mesenteroides subsp. mesenteroides, as Recorded in the Presence of Different Medium Components

Summary Bacteriocin ST33LD, produced by Leuconostoc mesenteroides subsp. mesenteroides, is approximately 2.7 kDa in size and inhibits Enterococcus faecalis, Escherichia coli, Lactobacillus casei and Pseudomonas aeruginosa. Good growth was recorded in the presence of 10% (w/v) soy milk or 10% (w/v) molasses, but there was no bacteriocin production. Growth in MRS broth adjusted to pH 4.5 yielded low bacteriocin levels (800 AU/ml). However, the same medium adjusted to pH 5.0, 5.5 and 6.5, respectively, yielded 3200 AU/ml. Tween 80 decreased bacteriocin production by more than 50%. Growth in the presence of tryptone yielded maximal activity (12,800 AU/ml), whereas different combinations of tryptone, meat extract and yeast extract produced activity levels of 1600 AU/ml and less. Growth in the presence of 2.0% (w/v) sucrose, or maltose, yielded much higher levels of bacteriocin activity (12,800 AU/ml) compared to growth in the presence of 2.0% (w/v) glucose or lactose (6400 AU/ml). Lower yields were also recorded in the presence of fructose and mannose. KH₂PO₄ at 10.0% (w/v) stimulated bacteriocin production. Glycerol concentrations of 0.5% (w/v) and higher (up to 5.0%, w/v) repressed bacteriocin production by 50%. The addition of cyanocobalamin, thiamine and L-ascorbic acid to MRS broth (1.0 ppm) yielded 12,800 AU/ml bacteriocin, whereas the addition of DL-6,8-thioctic acid yielded only 6 400 AU/ml.     

Chemical composition and antimicrobial activity of <Emphasis Type="Italic">Thymus pannonicus</Emphasis> All. (<Emphasis Type="Italic">Lamiaceae</Emphasis>) essential oil

This paper presents the results of a study on chemical composition and antimicrobial activity of Thymus pannonicus All. (Lamiaceae) essential oil from Vojvodina province (north of Serbia). The investigated oil was hydrodistilled from a flowering plant and analysed by GC and GC-MS. Fifty-three constituents were identified (>97% of total oil), with geranial (41.42%, w/w) and neral (29.61%, w/w) as the most prominent. The antimicrobial activity of the oil was evaluated using agar disc diffusion and broth microdilution method against Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa, Escherichia coli, two strains of Klebsiella pneumoniae and two strains of Candida albicans. The essential oil exhibited antimicrobial activity to varying degrees against all tested strains. The maximum activity of T. Pannonicus oil was observed against E. coli, S. aureus and both tested strains of C. Albicans (MIC = 50 μ/ml, each). Moderate activity was observed against P. aeruginosa and one of the tested strains of K. Pneumoniae (MIC = 200 μ/ml), while E. faecalis and the other strain of K. Pneumoniae expressed a higher degree of resistance (MIC > 200 μ/ml). This study confirms that essential oil of T. pannonicus possesses remarkable in vitro antimicrobial activity against several medicinally important pathogens. This is attributable to lemon-scented citral, a mixture of geranial and neral, which has well-documented antimicrobial activity against a range of bacteria and fungi.     

Antibacterial activity of ethanolic and aqueous extracts of Acacia aroma Gill. ex Hook et Arn

The purpose of the present study was to investigate the antibacterial activity of seven ethanolic extracts and three aqueous extracts from various parts (leaves, stems and flowers) of A. aroma against 163 strains of antibiotic multi-resistant bacteria. The disc diffusion assay was performed to evaluate antibacterial activity of the A. aroma crude extracts, against several Gram-positive bacteria (E. faecalis, S. aureus, coagulase-negative stahylococci, S. pyogenes, S. agalactiae, S. aureus ATCC 29213, E. faecalis ATCC 29212) and Gram-negative bacteria (E. coli., K. pneumoniae, P. mirabilis, E. cloacae, S. marcescens, M morganii, A. baumannii, P. aeruginosa, S. maltophilia, E. coli ATCC 35218, P. aeruginosa ATCC 27853, E. coli ATCC 25922). All ethanolic extracts showed activity against gram-positive bacteria. Among all obtained extracts, only leaf and flower fluid extracts showed activity against Gram-negative bacteria. Based on this bioassay, leaf fluid extracts tended to be the most potent, followed by flower fluid extracts. Minimal inhibitory concentration (MIC) values of extracts and antibiotics were comparatively determined by agar and broth dilution methods. Both extracts were active against S. aureus, coagulase-negative stahylococci, E. faecalis and E. faecium and all tested Gram-negative bacteria with MIC values from 0.067 to 0.308 mg/ml. In this study the minimal bactericidal concentration (MBC) values were identical or twice as high than the corresponding MIC for leaf extracts and four or eight times higher than MIC values for flower extracts. This may indicate a bactericidal effect. Stored extracts have similar antibacterial activity as recently obtained extracts. The A. aroma extracts of leaves and flowers may be useful as antibacterial agents against Gram- negative and Gram-positive antibiotic multi-resistant microorganisms.     

BAMP-28 Antimicrobial Peptide Against Different MALDI Biotype of Carbapenam Resistant Enterobacteriaceae

Worldwide emergence of Carbapenam resistance in Enterobacteriaceae (CRE) are increasing globally and becoming a severe public health issue. Infections caused by CRE have limited treatment options and have been associated with high mortality rates. Due to their unique mode of action, antimicrobial peptides are novel alternatives to traditional antibiotics for tackling the issue of bacterial multidrug resistance. An easy, rapid and accurate detection of 72 clinically CRE isolates using a MALDI–TOF MS was additionally developed. The CRE isolates belonging to 33 Carbapenam-resistant Klebsiella pneumoniae, 17 Carbapenam-resistant Escherichia coli, 16 Carbapenam-resistant Enterobacter cloacae and 6 Carbapenam-resistant Citrobacter freundii carrying blaNDM-1 were definitely discriminated from reference genotype strain by MALDI–TOF MS. This rapid, accurate, and reproducible peptide signature profiling technology could have new implications in laboratory-based high-throughput differentiation of extensive libraries of Carbapenam resistant Enterobacteriaceae. Antibacterial activity of 9 short novel peptides against these CRE isolates were investigated. Although neither synthetic peptides induced significant hemolysis, or showed cytotoxic on Vero cell, only BAMP-28 peptide inhibited growth of K. pneumoniae, E. coli, C. freundii and E. cloacae with MIC₅₀ of 18–40, 20–40, 16–25 and 18–36 µM, respectively. In conclusion, MALDI–TOF MS can be used to screen for Carbapenam resistance in K. pneumoniae, E. coli, E. cloacae and C. freundii. Interestingly, BMAP-28 peptide had acceptable effect on Carbapenam resistant Enterobacteriaceae including K. pneumoniae, E. coli, C. freundii and E. Cloacae isolates with less toxicity.

     

Production of staphylococcal enterotoxin in mixed cultures

Two Staphylococcus aureus strains were grown in brain-heart infusion (BHI) broth and a meat medium with Bacillus cereus, Streptococcus faecalis, Escherichia coli, and Pseudomonas aeruginosa. Both S. aureus strains grew well and produced enterotoxin in the presence of S. faecalis in BHI broth; however, enterotoxin production was observable in the meat medium only when the S. aureus inoculum was greater than the S. faecalis inoculum. S. aureus FRI-100 grown with B. cereus produced enterotoxin in both media only when the S. aureus inoculum was much higher than the B. cereus inoculum (10 versus 10(4) CFU), whereas S. aureus FRI-196E produced enterotoxin in both media at all inoculum combinations except in the meat medium, when the inocula of the two organisms were the same. S. aureus grown with E. coli in BHI broth produced enterotoxin at all inoculum combinations except when the E. coli inoculum was greater than the S. aureus inoculum; however, in the meat medium, enterotoxin was produced only when the S. aureus inoculum was much greater than the E. coli inoculum (10 versus 10(4) CFU), S. aureus FRI-100 grown with P. aeruginosa in either medium produced enterotoxin only when the S. aureus inoculum was much greater than the P. aeruginosa inoculum (10 versus 10(3) or 10(4) CFU). It can be concluded from these results that enterotoxin production is unlikely in mixed cultures unless the staphylococci outnumber the other contaminating organisms.     

Production of staphylococcal enterotoxin in mixed cultures.

Two Staphylococcus aureus strains were grown in brain-heart infusion (BHI) broth and a meat medium with Bacillus cereus, Streptococcus faecalis, Escherichia coli, and Pseudomonas aeruginosa. Both S. aureus strains grew well and produced enterotoxin in the presence of S. faecalis in BHI broth; however, enterotoxin production was observable in the meat medium only when the S. aureus inoculum was greater than the S. faecalis inoculum. S. aureus FRI-100 grown with B. cereus produced enterotoxin in both media only when the S. aureus inoculum was much higher than the B. cereus inoculum (10 versus 10(4) CFU), whereas S. aureus FRI-196E produced enterotoxin in both media at all inoculum combinations except in the meat medium, when the inocula of the two organisms were the same. S. aureus grown with E. coli in BHI broth produced enterotoxin at all inoculum combinations except when the E. coli inoculum was greater than the S. aureus inoculum; however, in the meat medium, enterotoxin was produced only when the S. aureus inoculum was much greater than the E. coli inoculum (10 versus 10(4) CFU), S. aureus FRI-100 grown with P. aeruginosa in either medium produced enterotoxin only when the S. aureus inoculum was much greater than the P. aeruginosa inoculum (10 versus 10(3) or 10(4) CFU). It can be concluded from these results that enterotoxin production is unlikely in mixed cultures unless the staphylococci outnumber the other contaminating organisms.     

Antimicrobial activity of organic extracts isolated from Aplysina fistularis (Demospongiae: Aplysinidae)

Organic extracts of the sponge Aplysina fistularis (Pallas 1766) were tested for antimicrobial activity against Gram positive bacteria (Staphylococcus aureus) and Gram negative bacteria (Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa). The minimal inhibitory concentration (MIC) and toxic activity of extract were determined. Susceptibility trials of organic fractions obtained by VLC: Hexane, EtOAc and CHCl3 showed that EtOAc fraction has antibacterial activity against E. coli, while CHCl3 fraction inhibited E. coli and S. aureus growth. The later refractioning of EtOAc fraction and the biodirected assays showed that fractions F12 and F13 of EtOAc/Hex and EtOAc F14 were bioactive against Gram positive and Gram negative bacteria. Only EtOAc/MeOH Sf2 from subfractionig of EtOAc F14 produced inhibition for E. coli and S. aureus. In Sf2 EtOAc/MeOH, MIC was moderate for S. aureus (MIC > 256 g/ml). F4 CHCl3/MeOH produced a high inhibition in S. aureus (MIC = 0.125 g/ml) and for E. coli (MIC > 16 g/ml). F10 CHCl3/MeOH showed a moderate activity against S. aureus (MIC > 128 g/ml) and low activity against E. coli (MIC = 512 g/ml). F10 CHCL3/MeOH did no present toxic activity against Artemia salina. The fractiorts F4 CHCL3/MeOH and Sf2 EtOAc/MeOH were toxic for this organism when the concentration was higher than 100 microg/ml. LC50 in both cases was 548.4 and 243.4 microg/ml respectively. Secondary metabolites of medium polarity obtained from A. fistularis have a wide spectrum of anti bacterial activity. Toxicity analysis suggests that only F10 CHCL3/MeOH has potential as an antimicrobial agent for clinical use.     

Addition of a surfactant to tryptic soy broth allows growth of a lactic acid bacteria food antimicrobial, Escherichia coli O157:H7, and Salmonella enterica

Aims: This study aimed to determine the survival and growth of Escherichia coli O157:H7 and Salmonella enterica subsp. enterica in a medium supporting the growth of a Lactic Acid Bacteria (LAB) food antimicrobial culture. Methods and Results: Foodborne pathogens and LAB were cultured individually in tryptic soy broth (TSB), tryptic soy broth supplemented with one g l^?1 Tween 80^® (TSB‐T80), and de Man, Rogosa and Sharpe (MRS) broth. Growth of E. coli O157:H7 and Salmonella was similar in TSB and TSB‐T80 but was significantly less in MRS. Conversely, LAB growth was similar in MRS and TSB‐T80 but was significantly less in TSB. Conclusions: Supplementation of TSB with Tween 80^® allows growth of LAB to levels similar to that observed with MRS but does not inhibit the growth of E. coli O157:H7 and Salmonella. We present the formulation of a medium useful in studies useful for evaluating competitive inhibition of foodborne pathogens by LAB in vitro. Significance and Impact of the Study: This study reports the utility of TSB‐T80 for the completion of in vitro competitive inhibition assays incorporating a Lactic Acid Bacteria food safety culture.     

Escherichia coli physiology in Luria-Bertani broth

Luria-Bertani broth supports Escherichia coli growth to an optical density at 600 nm (OD₆₀₀) of 7. Surprisingly, however, steady-state growth ceases at an OD₆₀₀ of 0.3, when the growth rate slows down and cell mass decreases. Growth stops for lack of a utilizable carbon source. The carbon sources for E. coli in Luria-Bertani broth are catabolizable amino acids, not sugars.