Effects of caprylic acid and triacylglycerols of both caprylic and capric acid in rabbits experimentally infected with enteropathogenic Escherichia coli O103

The Protective Effect of Octanoic Acid on Sepsis: A Review

Sepsis, a systemic inflammation that occurs in response to a bacterial infection, is a significant medical challenge. Research conducted over the past decade has indicated strong associations among a patient's nutritional status, the composition of their gut microbiome, and the risk, severity, and prognosis of sepsis. Octanoic acid (OA) plays a vital role in combating sepsis and has a protective effect on both animal models and human patients. In this discussion, the potential protective mechanisms of OA in sepsis, focusing on its regulation of the inflammatory response, immune system, oxidative stress, gastrointestinal microbiome and barrier function, metabolic disorders and malnutrition, as well as organ dysfunction are explored. A comprehensive understanding of the mechanisms by which OA act may pave the way for new preventive and therapeutic approaches to sepsis.

Processing and characterization of antimicrobial bioplastic films based on green microalgae Scenedesmus obliquus extract-loaded polyurethane

The green microalga Scenedesmus obliquus, isolated from the Egyptian environment, was used for the synthesis of bio-based plastic materials. Polyurethane (PU) was blended with different proportions (0%, 10%, 20%, and 40%) of chloroform extract to form bioplastic films. The bioplastic films were characterized using water vapor transmission rate measurements and scanning electron microscopy (SEM). The WVTR of pure PU was 193.37 g/m2. day, while the values of algae/PU films were 129.74, 122.56, and 99.75 g/m2.day. S. obliquus reported having Palmitic, which possesses antimicrobial activity and acts as an effective antimicrobial agent in the synthesized bioplastic films. Antimicrobial activity of the algal extract and the synthesized bioplastic films were tested against two Gram-positive bacteria; Staphylococcus aureus, Enterococcus faecalis, two Gram-negative bacteria; Escherichia coli, Pseudomonas aeruginosa, and Candida albicans as a model for fungi. The results indicated that S. obliquus extract exhibited a clear antimicrobial activity against all tested microbes. The antimicrobial rate of bioplastic films containing 40% of the extract reached 100% after 2 h of contact with E. coli and E. faecalis. In conclusion, this study offers a promising future for the use of biodegradable antimicrobial bioplastic films as an affordable and environmentally friendly alternative to plastics in many applications.

Preliminary evaluation of fenugreek (Trigonella foenum-graecum) seed gum as a potential prebiotic for growing rabbits in Tunisia: effects on in vivo faecal digestibility and in vitro fermentation

<p>This study aims to determine the effect of dietary inclusion of fenugreek seed gum (FSG), rich in galactomannans, on nutrient apparent digestibility and caecal environment, as well as on <em>in vitro</em> caecal fermentation of Tunisian growing rabbits. Three experimental diets were formulated, including 0, 0.25 and 0.5% of FSG (FSG0, FSG0.25 and FSG0.5, respectively) for the <em>in vivo</em> trial and 0, 0.125, 0.25, 0.5 and 100% of FSG (FSG0, FSG0125, FSG0.25, FSG0.5 and FSG100, respectively) for the <em>in vitro</em> trial. In the <em>in vivo</em> trial, 45 weaned rabbits 31 d old (15 per treatment) were housed in individual cages until 94 d of age. Apparent digestibility coefficients were determined at two ages, from 38 to 41 and from 56 to 59 d old, and caecal traits were recorded after slaughtering. In the <em>in vitro</em> trial, the five experimental diets were incubated with a rabbit caecal inoculum. Gas production was measured and modelled until 72 h and the fermentation traits were measured. Apparent faecal digestibility coefficients of main nutrients and main caecal environment traits were not significantly affected by the dietary inclusion of FSG (<em>P</em>&gt;0.05). However, animals fed with FSG showed lower caecal pH (–0.15; <em>P</em>&lt;0.05) values. Regarding the in vitro fermentation, FSG100 increased asymptotic gas production (+11.25, <em>P</em>&lt;0.001), sharpness of the switching characteristic of the profile (+1.98, <em>P</em>&lt;0.001) and the maximum substrate degradation rate (RM) (+0.188, <em>P</em>&lt;0.001), but decreasing the time after incubation at which half of the asymptotic amount of gas has been formed (–5.86, <em>P</em>&lt;0.001) and at which RM occurs (–4.53, <em>P</em>&lt;0.01). Likewise, FSG100 significantly decreased caecal pH (–1.035, <em>P</em>&lt;0.001), lactic acid (–9.51, <em>P</em>&lt;0.069) and N-NH₃ concentrations (–12.81, <em>P</em>&lt;0.001). Meanwhile, it increased the total volatile fatty acids (VFA) production (+43.15, <em>P</em>&lt;0.001). Gradual dietary inclusion of FSG from 0 to 0.5% only significantly increased total VFA production in the caecum (+100 mmol/L per percentage point of FSG inclusion; <em>P</em>&lt;0.05). In conclusion, FSG is highly and rapidly in vitro fermented by rabbit caecal bacteria. However, dietary inclusion of FSG up to 0.5%, might be insufficient to affect the apparent digestibility and fermentation profile of growing rabbits to a great extent.</p>

Fatty Acids from Hermetia illucens Larvae Fat Inhibit the Proliferation and Growth of Actual Phytopathogens

The rapid increase of plant diseases caused by bacterial phytopathogens calls for an urgent search for new antibacterials. Antimicrobial compounds of natural origin stand up as frontiers in the attempts of the antibiotic overuse replacement. With this in mind, the Hermetia illucens (H. illucens) larvae have recently gained attention as a promising approach to fulfill this need. This study aimed to isolate the active constituents of H. illucens larvae fat and to estimate its antimicrobial capacity. We discovered the best composition of extracting solution retaining the pronounced antimicrobial activity of the extract. Using gas chromatography-mass spectrometry (GC-MS), we identified the unique natural array of fatty acids as the major constituents of the acidified water-methanol extract (AWME) as having new antimicrobial potency. In standard turbidimetric assay, the minimum inhibitory concentration (MIC) of the AWME was 0.78 mg/mL after 24 h of incubation for all five tested phytopathogenic bacteria strains: Pantoea agglomerans, Xanthomonas campestris, Pectobacterium carotovorum subsp. carotovorum, Pectobacterium atrosepticum, and Dickeya solani. The minimum bactericidal concentration (MBC) ranged from 0.78 to 1.56 mg/mL against all tested strains after 24 h of incubation. The inhibition zone size of AWME (INZ) at 50 mg/mL concentration was in the range 12.2 ± 0.56 to 19.0 ± 0.28 mm, while zone size for the positive control (penicillin-streptomycin) (5000 IU/mL-5000 µg/mL) was in the scale of 20.63 ± 0.53 to 24.0 ± 0.35 mm as revealed by standard disk diffusion assay. For the first time, our findings indicated the substantial antibacterial potential of AWME of H. illucens larvae fat against these actual phytopathogens, thus paving the way for further research to determine the mechanism of action in crop protection.

Longitudinal Associations of the Cystic Fibrosis Airway Microbiome and Volatile Metabolites: A Case Study

The identification of 16S rDNA biomarkers from respiratory samples to describe the continuum of clinical disease states within persons having cystic fibrosis (CF) has remained elusive. We sought to combine 16S, metagenomics, and metabolomics data to describe multiple transitions between clinical disease states in 14 samples collected over a 12-month period in a single person with CF. We hypothesized that each clinical disease state would have a unique combination of bacterial genera and volatile metabolites as a potential signature that could be utilized as a biomarker of clinical disease state. Taxonomy identified by 16S sequencing corroborated clinical culture results, with the majority of the 109 PCR amplicons belonging to the bacteria grown in clinical cultures (Escherichia coli and Staphylococcus aureus). While alpha diversity measures fluctuated across disease states, no significant trends were present. Principle coordinates analysis showed that treatment samples trended toward a different community composition than baseline and exacerbation samples. This was driven by the phylum Bacteroidetes (less abundant in treatment, log₂ fold difference -3.29, p = 0.015) and the genus Stenotrophomonas (more abundant in treatment, log₂ fold difference 6.26, p = 0.003). Across all sputum samples, 466 distinct volatile metabolites were identified with total intensity varying across clinical disease state. Baseline and exacerbation samples were rather uniform in chemical composition and similar to one another, while treatment samples were highly variable and differed from the other two disease states. When utilizing a combination of the microbiome and metabolome data, we observed associations between samples dominated Staphylococcus and Escherichia and higher relative abundances of alcohols, while samples dominated by Achromobacter correlated with a metabolomics shift toward more oxidized volatiles. However, the microbiome and metabolome data were not tightly correlated; examining both the metagenomics and metabolomics allows for more context to examine changes across clinical disease states. In our study, combining the sputum microbiome and metabolome data revealed stability in the sputum composition through the first exacerbation and treatment episode, and into the second exacerbation. However, the second treatment ushered in a prolonged period of instability, which after three additional exacerbations and treatments culminated in a new lung microbiome and metabolome.

Application of Pontentilla anserine, Polygonum aviculare and Rumex crispus Mixture Extracts in a Rabbit Model with Experimentally Induced E. coli Infection

The study evaluated the anti-colibacteriosis efficacy of herbs in experimental infection by rabbit pathogenic strain of E. coli O103 eae+. It also studied the effects of herbal mixture added to feed or water on blood parameters. This animal model was used since some E. coli strains pathogenic for rabbits are similar to the strains that are pathogenic to humans. The components of herbal extracts were Rumex crispus, Pontentilla anserine, and Polygonum aviculare. Supplementation was carried out in water (ExpW group) or feed (ExpF group), and four weeks later the animals were infected with the E. coli O103 eae+ strain. The administration of herbs increased the mean concentration of total protein and serum albumin (p < 0.01) without causing disturbances of electrolyte and acid-base balance. The highest total antioxidant capacity (TAS) value (p < 0.01) was observed in the ExpF group. The administration of a mixture of herbs and feed caused more reduction in the number of E. coli in cecum than supplementation into water after an experimental infection. The herbs applied in rabbits did not harm the secretory functions of liver, electrolyte, and acid-base balance of the blood. The application of the tested herbal mixtures can control the activity of the intestinal microbial community.

Orally administered Lactobacillus casei exhibited several probiotic properties in artificially suckling rabbits

Objective

Lactobacilli in rabbit intestine is rare and its function in rabbit gut health is not fully understood. The present study aimed to evaluate in vivo the probiotic potential of Lactobacillus casei for suckling rabbits.

Methods

Two healthy 5-day-old suckling rabbits with similar weights from each of 12 New Zealand White litters were selected and disturbed to control group and treatment group. All rabbits were artificially fed. The treatment group had been supplemented with live Lactobacillus casei in the milk from the beginning of the trial to 13 days of age. At 15 days of age, healthy paired rabbits were slaughtered to collect intestinal samples.

Results

i) Oral administration of Lactobacillus casei significantly increased the proportion of Lactobacilli in the total intestinal bacteria (p<0.01) and obviously reduced that of Escherichia-Shigella (p<0.01); ii) treatment increased the length of vermiform appendix (p<0.05); iii) a higher percentage of degranulated paneth cells was observed in the duodenum and jejunum when rabbits administered with Lactobacillus casei (p<0.01); and iv) the expression of toll-like receptor 9, lysozyme (LYZ), and defensin-7-like (DEFEN) in the duodenum and jejunum was stimulated by supplemented Lactobacillus casei (p<0.05).

Conclusion

Orally administered Lactobacillus casei could increase the abundance of intestinal Lactobacilli, decrease the relative abundance of intestinal Escherichia-Shigella, promote the growth of appendix vermiform, stimulate the degranulation of paneth cells and induce the expression of DEFEN and LYS. The results of the present study implied that Lactobacillus casei exhibited probiotic potential for suckling rabbits.

Antibacterial Free Fatty Acids and Monoglycerides: Biological Activities, Experimental Testing, and Therapeutic Applications

Antimicrobial lipids such as fatty acids and monoglycerides are promising antibacterial agents that destabilize bacterial cell membranes, causing a wide range of direct and indirect inhibitory effects. The goal of this review is to introduce the latest experimental approaches for characterizing how antimicrobial lipids destabilize phospholipid membranes within the broader scope of introducing current knowledge about the biological activities of antimicrobial lipids, testing strategies, and applications for treating bacterial infections. To this end, a general background on antimicrobial lipids, including structural classification, is provided along with a detailed description of their targeting spectrum and currently understood antibacterial mechanisms. Building on this knowledge, different experimental approaches to characterize antimicrobial lipids are presented, including cell-based biological and model membrane-based biophysical measurement techniques. Particular emphasis is placed on drawing out how biological and biophysical approaches complement one another and can yield mechanistic insights into how the physicochemical properties of antimicrobial lipids influence molecular self-assembly and concentration-dependent interactions with model phospholipid and bacterial cell membranes. Examples of possible therapeutic applications are briefly introduced to highlight the potential significance of antimicrobial lipids for human health and medicine, and to motivate the importance of employing orthogonal measurement strategies to characterize the activity profile of antimicrobial lipids.

Antibacterial Free Fatty Acids and Monoglycerides: Biological Activities, Experimental Testing, and Therapeutic Applications

Antimicrobial lipids such as fatty acids and monoglycerides are promising antibacterial agents that destabilize bacterial cell membranes, causing a wide range of direct and indirect inhibitory effects. The goal of this review is to introduce the latest experimental approaches for characterizing how antimicrobial lipids destabilize phospholipid membranes within the broader scope of introducing current knowledge about the biological activities of antimicrobial lipids, testing strategies, and applications for treating bacterial infections. To this end, a general background on antimicrobial lipids, including structural classification, is provided along with a detailed description of their targeting spectrum and currently understood antibacterial mechanisms. Building on this knowledge, different experimental approaches to characterize antimicrobial lipids are presented, including cell-based biological and model membrane-based biophysical measurement techniques. Particular emphasis is placed on drawing out how biological and biophysical approaches complement one another and can yield mechanistic insights into how the physicochemical properties of antimicrobial lipids influence molecular self-assembly and concentration-dependent interactions with model phospholipid and bacterial cell membranes. Examples of possible therapeutic applications are briefly introduced to highlight the potential significance of antimicrobial lipids for human health and medicine, and to motivate the importance of employing orthogonal measurement strategies to characterize the activity profile of antimicrobial lipids.

Sodium Octanoate Modulates the Innate Immune Response of Bovine Mammary Epithelial Cells through the TLR2/P38/JNK/ERK1/2 Pathway: Implications during Staphylococcus aureus Internalization

Bovine mammary epithelial cells (bMECs) contribute to mammary gland defense against invading pathogens, such as Staphylococcus aureus (intracellular facultative), which is recognized by TLR2. In a previous report, we showed that sodium octanoate [NaO, a medium chain fatty acid (C8)] induces (0.25 mM) or inhibits (1 mM) S. aureus internalization into bMECs and differentially regulates the innate immune response (IIR). However, the molecular mechanisms have not been described, which was the aim of this study. The results showed that α5β1 integrin membrane abundance (MA) was increased in 0.25 mM NaO-treated cells, but TLR2 or CD36 MA was not modified. When these receptors were blocked individually, 0.25 mM NaO-increased S. aureus internalization was notably reduced. Interestingly, in this condition, the IIR of the bMECs was impaired because MAPK (p38, JNK, and ERK1/2) phosphorylation and the activation of transcription factors related to these pathways were decreased. In addition, the 1 mM NaO treatment induced TLR2 MA, but neither the integrin nor CD36 MA was modified. The reduction in S. aureus internalization induced by 1 mM NaO was increased further when TLR2 was blocked. In addition, the phosphorylation levels of the MAPKs increased, and 13 transcriptional factors related to the IIR were slightly activated (CBF, CDP, c-Myb, AP-1, Ets-1/Pea-3, FAST-1, GAS/ISRE, AP-2, NFAT-1, OCT-1, RAR/DR-5, RXR/DR-1, and Stat-3). Moreover, the 1 mM NaO treatment up-regulated gene expression of IL-8 and RANTES and secretion of IL-1β. Notably, when 1 mM NaO-treated bMECs were challenged with S. aureus, the gene expression of IL-8 and IL-10 increased, while IL-1β secretion was reduced. In conclusion, our results showed that α5β1 integrin, TLR2 and CD36 are involved in 0.25 mM NaO-increased S. aureus internalization in bMECs. In addition, 1 mM NaO activates bMECs via the TLR2 signaling pathways (p38, JNK, and ERK1/2), which improves IIR before S. aureus invasion. Additionally, NaO (1 mM) might exert anti-inflammatory effects after bacterial internalization.

Kinetic Behavior of Escherichia coli on Various Cheeses under Constant and Dynamic Temperature

In this study, we developed kinetic models to predict the growth of pathogenic Escherichia coli on cheeses during storage at constant and changing temperatures. A five-strain mixture of pathogenic E. coli was inoculated onto natural cheeses (Brie and Camembert) and processed cheeses (sliced Mozzarella and sliced Cheddar) at 3 to 4 log CFU/g. The inoculated cheeses were stored at 4, 10, 15, 25, and 30°C for 1 to 320 h, with a different storage time being used for each temperature. Total bacteria and E. coli cells were enumerated on tryptic soy agar and MacConkey sorbitol agar, respectively. E. coli growth data were fitted to the Baranyi model to calculate the maximum specific growth rate (μ max; log CFU/g/h), lag phase duration (LPD; h), lower asymptote (log CFU/g), and upper asymptote (log CFU/g). The kinetic parameters were then analyzed as a function of storage temperature, using the square root model, polynomial equation, and linear equation. A dynamic model was also developed for varying temperature. The model performance was evaluated against observed data, and the root mean square error (RMSE) was calculated. At 4°C, E. coli cell growth was not observed on any cheese. However, E. coli growth was observed at 10°C to 30°C with a μ max of 0.01 to 1.03 log CFU/g/h, depending on the cheese. The μ max values increased as temperature increased, while LPD values decreased, and μ max and LPD values were different among the four types of cheese. The developed models showed adequate performance (RMSE = 0.176-0.337), indicating that these models should be useful for describing the growth kinetics of E. coli on various cheeses.

Effects of sodium octanoate on innate immune response of mammary epithelial cells during Staphylococcus aureus internalization

Bovine mammary epithelial cells (bMECs) are capable of initiating an innate immune response to invading bacteria. Short chain fatty acids can reduce Staphylococcus aureus internalization into bMEC, but it has not been evaluated if octanoic acid (sodium octanoate, NaO), a medium chain fatty acid (MCFA), has similar effects. In this study we determined the effect of NaO on S. aureus internalization into bMEC and on the modulation of innate immune elements. NaO (0.25–2 mM) did not affect S. aureus growth and bMEC viability, but it differentially modulated bacterial internalization into bMEC, which was induced at 0.25–0.5 mM (~60%) but inhibited at 1-2 mM (~40%). Also, bMEC showed a basal expression of all the innate immune genes evaluated, which were induced by S. aureus. NaO induced BNBD4, LAP, and BNBD10 mRNA expression, but BNBD5 and TNF-α were inhibited. Additionally, the pretreatment of bMEC with NaO inhibited the mRNA expression induction generated by bacteria which coincides with the increase in internalization; only TAP and BNDB10 showed an increase in their expression; it coincides with the greatest effect on the reduction of bacterial internalization. In conclusion, NaO exerts a dual effect on S. aureus internalization in bMEC and modulates elements of innate immune response.

Selection and characterization of cellulose-deficient derivates of shiga toxin-producing Escherichia coli

Shiga toxin-producing Escherichia coli (STEC) is known to have several defense mechanisms, one of which is the production of extracellular substances including cellulose. The goal of this study was to prepare pairs of STEC cultures for use in future studies designed to address the role of cellulose in protecting the cells of STEC for survival under adverse environmental conditions. Cells of STEC deficient in cellulose production were separated from cellulose-proficient wild-type cells. The identities of the two types of cells were confirmed using serotyping and pulsed-field gel electrophoresis (PFGE). Selected growth characteristics of the two types of cells were determined using three phenotype microarray plates, PM9, PM10, and PM11. The cellulose-deficient and cellulose-proficient cells in each STEC pair shared the same serotype and PFGE profile. The deficiency in cellulose production did not significantly (P > 0.05) affect the growth characteristics of STEC cells under 191 of the 210 tested growth conditions. Significant differences in growth between the two types of cells were observed only in the presence of two antibiotics, a short chain fatty acid, and high concentrations of osmolytes, as well as under extreme acidic and alkaline pH. These results suggest that deficiency in cellulose production did not alter the serological property, PFGE profile, and growth characteristics of selected STEC strains under optimal growth conditions. The STEC strains and their cellulose-deficient derivates could be useful for studying the role of cellulose in protecting the cells of STEC for survival under adverse environmental conditions.

Caprylic Acid reduces enteric campylobacter colonization in market-aged broiler chickens but does not appear to alter cecal microbial populations

Campylobacter is a leading cause of foodborne illness in the United States, and epidemiological evidence indicates poultry products to be a significant source of human Campylobacter infections. Caprylic acid, an eight-carbon medium-chain fatty acid, reduces Campylobacter colonization in chickens. How caprylic acid reduces Campylobacter carriage may be related to changes in intestinal microflora. To evaluate this possibility, cecal microbial populations were evaluated with denaturing gradient gel electrophoresis from market-age broiler chickens fed caprylic acid. In the first trial, chicks (n = 40 per trial) were assigned to four treatment groups (n = 10 birds per treatment group): positive controls (Campylobacter, no caprylic acid), with or without a 12-h feed withdrawal before slaughter; and 0.7% caprylic acid supplemented in feed for the last 3 days of the trial, with or without a 12-h feed withdrawal before slaughter. Treatments were similar for trial 2, except caprylic acid was supplemented for the last 7 days of the trial. At age 14 days, chicks were orally challenged with Campylobacter jejuni, and on day 42, ceca were collected for denaturing gradient gel electrophoresis and Campylobacter analysis. Caprylic acid supplemented for 3 or 7 days at 0.7% reduced Campylobacter compared with the positive controls, except for the 7-day treatment with a 12-h feed withdrawal period. Denaturing gradient gel electrophoresis profiles of the cecal content showed very limited differences in microbial populations. The results of this study indicate that caprylic acid's ability to reduce Campylobacter does not appear to be due to changes in cecal microflora.

Changes in the bacterial population of the caecum and stomach of the rabbit in response to addition of dietary caprylic acid

The effect of caprylic acid, either in its pure form, or as Akomed R, on the microbial community of the stomach and caecum of farmed rabbits was investigated. This fatty acid, which is often added to the diet of farmed rabbits to reduce mortality rates was shown to reduce the number of coliforms isolated from both the stomach and the caecum. Moreover, it led to a reduction in the total number of anaerobic bacteria isolated from the caecum, but not for those isolated from the stomach. Its mode of action remains unclear, but here it is shown by use of both DGGE and TRFLP analysis that these changes are not confined to one specific group of bacteria, but rather affects a number of species.

Antibacterial free fatty acids: activities, mechanisms of action and biotechnological potential

Amongst the diverse and potent biological activities of free fatty acids (FFAs) is the ability to kill or inhibit the growth of bacteria. The antibacterial properties of FFAs are used by many organisms to defend against parasitic or pathogenic bacteria. Whilst their antibacterial mode of action is still poorly understood, the prime target of FFA action is the cell membrane, where FFAs disrupt the electron transport chain and oxidative phosphorylation. Besides interfering with cellular energy production, FFA action may also result from the inhibition of enzyme activity, impairment of nutrient uptake, generation of peroxidation and auto-oxidation degradation products or direct lysis of bacterial cells. Their broad spectrum of activity, non-specific mode of action and safety makes them attractive as antibacterial agents for various applications in medicine, agriculture and food preservation, especially where the use of conventional antibiotics is undesirable or prohibited. Moreover, the evolution of inducible FFA-resistant phenotypes is less problematic than with conventional antibiotics. The potential for commercial or biomedical exploitation of antibacterial FFAs, especially for those from natural sources, is discussed.

Inhibitory activity of rabbit milk and medium-chain fatty acids against enteropathogenic Escherichia coli O128

Colibacillosis represents a major cause of diarrhea in young rabbits. In order to elucidate protective effect of milk, in vitro and in vivo experiments were carried out. In the in vitro experiment, rabbit milk treated with lipase significantly decreased the number of viable cells in cultures of Escherichia coli, O128 serotype, from 10.3 to 6.2-7.3log(10)/(cfuml). The lipase effect was the same with heat-treated (100 degrees C/10min) and raw milk. Raw milk without lipase decreased the number of E. coli only marginally. In the in vivo experiment, weaned rabbits received feed contaminated with the same bacterium. The course of the infection was moderate, only 2 out of 36 infected rabbits died. Seven days after inoculation, caprylic acid at 5g/kg feed and triacylglycerols of caprylic and capric acid at 10g/kg feed decreased faecal output of E. coli from 10.2log(10)/(cfug) to 5.8 and 6.1log(10)/(cfug), respectively. The number of E. coli in faeces of non-infected rabbits averaged 4.0log(10)/(cfug). The growth of infected rabbits was slow for 2 weeks after infection. In the third week a compensatory growth was apparent. At the end of the experiment, average body weights of rabbits receiving caprylic acid and those of non-infected rabbits were not significantly different. It can be concluded that (i) lipids rather than proteins seem to be responsible for the antimicrobial activity of rabbit milk; and (ii) this activity was lipase-dependent. Caprylic acid or oils with high a concentration of it may be used as feed supplements for weanlings.