Broad Spectrum Of Pathogenic Bacteria Research Articles

Characterization of feline-originated probiotics Lactobacillus rhamnosus CACC612 and Bifidobacterium animalis subsp. lactis CACC789 and evaluation of their host response

BackgroundProbiotics are beneficial for animal health and new potential probiotics need to be characterized for their prospective use in improving animal health. In this study, 32 bacterial strains were isolated from a Norwegian forest cat (castrated, 12 years old) and a Persian cat (castrated, 10 years old), which were privately owned and had indoor access.ResultsLactobacillus rhamnosus CACC612 (CACC612) and Bifidobacterium animalis subsp. lactis CACC789 (CACC789) were selected as potential probiotics; characterization of the two strains showed equivalent acid tolerance, similar cell adhesion rates on the HT-29 monolayer cell line, and superior bile tolerance compared to Lactobacillus rhamnosus GG (LGG). Subsequently, they exhibited inhibitory effects against a broad spectrum of pathogenic bacteria, including E. coli (KCTC 2617), Salmonella Derby (NCCP 12,238), Salmonella Enteritidis (NCCP 14,546), Salmonella Typhimurium (NCCP 10,328), Clostridium difficile JCM 1296T. From evaluating host effects, the viability of the feline macrophage cell line (Fcwf-4) increased with the treatment of CACC612 or CACC789 (P < 0.05). The induced expression of immune-related genes such as IFN-γ, IL1β, IL2, IL4, and TNF-α by immune stimulation was significantly attenuated by the treatment of CACC612 or CACC789 (P < 0.05). When 52 clinical factors of sera from 21 healthy cats were analyzed using partial least squares discriminant analysis (PLS-DA), the animals were obviously clustered before and after feeding with CACC612 or CACC789. In addition, hemoglobin and mean corpuscular hemoglobin concentration (MCHC) significantly increased after CACC612 feeding (P < 0.05).ConclusionsIn this study, feline-originated probiotics were newly characterized and their potentially probiotic effects were evaluated. These results contribute to our understanding of the functional effects of feline-derived probiotics and support their industrial applications.

The activation of carbon materials to control airborne pathogenic bacteria in the pig house by efficient adsorption

The presence of pathogenic bacteria at high levels in the air of concentrated animal production building aggravates cross transmission and impedes the biosafety of animal husbandry. Carbon material shows great potential in microbial adsorption to reduce the misuse of chemical disinfectants in livestock and poultry houses, but the complex environmental conditions and low efficiency in gas phase pose significant challenges to its practical implementation. A novel modified method of carbon felts, acidified and then ammoniated, was developed in simulated experiments. An intensive field study in a pig house was conducted to deploy carbon felts and adsorb airborne microorganisms efficiently. They had above 90% sterilizing activity against a broad spectrum of pathogenic bacteria in the laboratory. And the highest sterilization rate was 75.52% with operation of carbon felts in the pig house and could be maintained below 3 × 104 CFU m−3 for 18 d. Specifically, the relative abundance of several major pathogenic bacteria was significantly reduced in the air of pig house. Our research activates the antibacterial activity of carbon materials in the gas phase and further provides a promising strategy to improve animal health and welfare by purifying the air in livestock and poultry houses.

The penetration of human defensin 5 (HD5) through bacterial outer membrane: simulation studies.

Human α-defensin 5 (HD5) is one of cationic antimicrobial peptides which plays a crucial role in an innate immune system in human body. HD5 shows the killing activity against a broad spectrum of pathogenic bacteria by making a pore in a bacterial membrane and penetrating into a cytosol. Nonetheless, its pore-forming mechanisms remain unclear. Thus, in this work, the constant-velocity steered molecular dynamics (SMD) simulation was used to simulate the permeation of a dimeric HD5 into a gram-negative lipopolysaccharide (LPS) membrane model. Arginine-rich HD5 is found to strongly interact with a LPS surface. Upon arrival, arginines on HD5 interact with lipid A head groups (a top part of LPS) and then drag these charged moieties down into a hydrophobic core resulting in the formation of water-filled pore. Although all arginines are found to interact with a membrane, Arg13 and Arg32 appear to play a dominant role in the HD5 adsorption on a gram-negative membrane. Furthermore, one chain of a dimeric HD5 is required for HD5 adhesion. The interactions of arginine-lipid A head groups play a major role in adhering a cationic HD5 on a membrane surface and retarding a HD5 passage in the meantime.

Complete genome sequencing of Peyer\u2019s patches-derived Lactobacillus taiwanensis CLG01, a potential probiotic with antibacterial and immunomodulatory activity

BackgroundThe genus Lactobacillus is an important component of the gastrointestinal tract of human and animals and commonly considered as probiotic. L. taiwanensis has long been proposed to be a probiotic whereas understanding on this species is still in its infancy. Genomic information of L. taiwanensis is fairly limited. Extensive characterization of its beneficial traits is needed.ResultsA new strain CLG01 of L. taiwanensis was isolated from mouse Peyer’s patches. We established its probiotic profile through in vitro experiments. Complete genome of this strain was also sequenced and analyzed. L. taiwanensis CLG01 showed robust tolerance to acid and a degree of tolerance to bile salt with a promising antibacterial activity against a broad spectrum of pathogenic bacteria. In vitro treatment of mouse RAW 264.7 macrophage cells with heat-killed bacteria and bacterial supernatant of L. taiwanensis CLG01 resulted in enhancement of immune responses and upregulated expression of TNF-α and IL-6. The strain CLG01 also increased the IL-10 production of macrophages when co-treated with lipopolysaccharide (LPS). Complete genome of L. taiwanensis CLG01 contained a 1.89 Mb chromosome and two plasmids. Further genomic analysis revealed the presence of genes related to its resistance to different stresses and the beneficial effects mentioned above. Moreover, biosynthetic gene clusters (BGCs) encoding antimicrobial peptides, like bacteriocin, linear azol(in)e-containing peptide (LAP) and lanthipeptide, were also identified in the genome of L. taiwanensis CLG01.ConclusionsL. taiwanensis CLG01, isolated from mouse Peyer’s patches, is the first L. taiwanensis strain with both phenotypes and genotypes systematically studied. These preliminary data confirmed the role of L. taiwanensis CLG01 as a potential probiotic candidate with antibacterial and immunomodulatory activity, which provide insight for further investigation to this species.

Targeting Protein Folding: A Novel Approach for the Treatment of Pathogenic Bacteria.

Infectious diseases are a major cause of morbidity and mortality worldwide, exacerbated by increasing antibiotic resistance in many bacterial species. The development of drugs with new modes of action is essential. A leading strategy is antivirulence, with the aim to target bacterial proteins that are important in disease causation and progression but do not affect growth, resulting in reduced selective pressure for resistance. Immunophilins, a superfamily of peptidyl-prolyl cis-trans isomerase (PPIase) enzymes have been shown to be important for virulence in a broad-spectrum of pathogenic bacteria. This Perspective will provide an overview of the recent advances made in understanding the role of each immunophilin family, cyclophilins, FK506 binding proteins (FKBPs), and parvulins in bacteria. Inhibitor design and medicinal chemistry strategies for development of novel drugs against bacterial FKBPs will be discussed. Furthermore, drugs against human cyclophilins and parvulins will be reviewed in their current indication as antiviral and anticancer therapies.

Thermoflavimicrobium dichotomicum as a novel thermoalkaliphile for production of environmental and industrial enzymes

Thermoalkaliphilic actinomycetes enzymes have many important applications in many industrial, biotechnological and environmental aspects. So, the current study aimed to obtain the thermoalkali-enzymes producing actinomycetes. A novel thermoalkaliphilic actinomycete strain was isolated from Egyptian Siwa oasis and identified according to its morphological, physiological and biochemical characters as Thermoflavimicrobium dichotomicum. And then confirmed by phylogenetic analysis and the partial sequence was deposited in GenBank under accession number of KR011193 and name of Thermoflavimicrobium dichotomicum HwSw11. It could produce amylase, cellulase, lipase, pectinase and proteinase enzymes. Also, this strain exhibited anti-bacterial activities against P. aeruginosa and E. coli with inhibition zones of 14 and 20 mm, respectively. Consequently, it has antifungal activity against A. niger, A. flavus and Penicillium notatum with inhibition zones of 17, 14 and 14 mm, respectively. For that, it may be concluded that Thermoflavimicrobium dichotomicum HwSw11 as a novel thermoalkaliphile has a wide range of biological activities against a broad spectrum of pathogenic bacteria and fungi, in addition to produce many enzymes (amylase, cellulase, lipase, pectinase and proteinase). So, this isolate could be applied as manufactory for many industrial, biotechnological and environmental sectors.

Antibacterial activity of hinokitiol against both antibiotic-resistant and -susceptible pathogenic bacteria that predominate in the oral cavity and upper airways.

Hinokitiol, a component of the essential oil isolated from Cupressaceae, possesses antibacterial and antifungal activities and has been used in oral care products. In this study, the antibacterial activities of hinokitiol toward various oral, nasal and nasopharyngeal pathogenic bacteria, including Streptococcus mutans, Streptococcus sobrinus, Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Prevotella intermedia, Fusobacterium nucleatum, methicillin-resistant and -susceptible Staphylococcus aureus, antibiotic-resistant and -susceptible Streptococcus pneumoniae, and Streptococcus pyogenes were examined. Growth of all these bacterial strains was significantly inhibited by hinokitiol, minimal inhibitory concentrations of hinokitiol against S. mutans, S. sobrinus, P. gingivalis, P. intermedia, A. actinomycetemcomitans, F. nucleatum, methicillin-resistant S. aureus, methicillin-susceptible S. aureus, antibiotic-resistant S. pneumoniae isolates, antibiotic-susceptible S. pneumoniae, and S. pyogenes being 0.3, 1.0, 1.0, 30, 0.5, 50, 50, 30, 0.3-1.0, 0.5, and 0.3 μg/mL, respectively. Additionally, with the exception of P. gingivalis, hinokitiol exerted bactericidal effects against all bacterial strains 1 hr after exposure. Hinokitiol did not display any significant cytotoxicity toward the human gingival epithelial cell line Ca9-22, pharyngeal epithelial cell line Detroit 562, human umbilical vein endothelial cells, or human gingival fibroblasts, with the exception of treatment with 500 μg/mL hinokitiol, which decreased numbers of viable Ca9-22 cells and gingival fibroblasts by 13% and 12%, respectively. These results suggest that hinokitiol exhibits antibacterial activity against a broad spectrum of pathogenic bacteria and has low cytotoxicity towards human epithelial cells.

Surface-Engineered Starch Magnetic Microparticles for Highly Effective Separation of a Broad Range of Bacteria

Polymeric magnetic particles (PMPs) have become a powerful tool for the separation and concentration of microorganisms from a heterogeneous liquid matrix. The functionalization of PMPs with polycationic polymers, such as chitosan, provides an effective means of capturing a broad spectrum of pathogenic bacteria through the intrinsic nature of chitosan interacting with the surface components of bacteria. Here, we report a fairly simple approach for the preparation of starch magnetic microparticles (SMMPs) through molecular rearrangement of short-chain glucans (SCGs) produced by enzymatic debranching of waxy maize starch. The surfaces of SMMPs were readily functionalized with chitosan through electrostatic interaction and hydrogen bonding. The chitosan-functionalized SMMPs (CS@SMMPs) showed high capture efficiency (>90%) for both Gram-positive and Gram-negative bacteria. To further investigate the mechanisms of chitosan–bacteria interaction, we employed model bacteria with different surface compositions. The...

Quorum-sensing inhibitor potential of trans-anethole aganist Pseudomonas aeruginosa.

Quorum sensing (QS) is a cell-cell communication system used by a broad spectrum of pathogenic bacteria to control the expression of their virulence genes. The interruption of QS systems of pathogenic bacteria has been considered as a novel way to fight bacterial diseases. In this study, trans-anethole, the main component of anise (Pimpinella anisum) oil was examined for its QS inhibitor (QSI) potential in an attempt to identify novel QSI compound effective against opportunistic pathogen Pseudomonas aeruginosa. The preliminary screening of QSI capacity of trans-anethole was determined using a quorum-sensing inhibitor screen (QSIS) assay. The QSIS assay indicated that trans-anethole has QSI properties. QSI capacity of trans-anethole was further confirmed by lasB-gfp fussion assay and virulence factor assays. A sub-MIC of trans-anethole reduced the expression of lasB by 57%, elastase production by 59%, protease production by 56%, pyocyanin production by 95% and swarming motility by 68% without inhibiting growth of Pseudomonas aeruginosa PA01. Molecular docking and protein-ligand interaction studies were performed to understand the molecular mechanism underlying inhibitory activity of trans-anethole. The results of these analysis suggested that trans-anethole fits within the binding site of the LasR protein of P. aeruginosa. Trans-anethole has the potential to inhibit QS-regulated virulence factors in P. aeruginosa by binding to LasR protein, similar to its natural ligand N-(3-oxododecanoyl)-l-homoserine lactone. In this study, for the first time, it was demonstrated that trans-anethole has the potential to disrupt bacterial communication and can be developed as a novel QSI to combat with P. aeruginosa and other clinically significant pathogens.

Complete genome sequence of Bacillus velezensis 157 isolated from Eucommia ulmoides with pathogenic bacteria inhibiting and lignocellulolytic enzymes production by SSF.

Bacillus velezensis 157 was isolated from the bark of Eucommia ulmoides, and exhibited antagonistic activity against a broad spectrum of pathogenic bacteria and fungi. Moreover, B. velezensis 157 also showed various lignocellulolytic activities including cellulase, xylanase, α-amylase, and pectinase, which had the ability of using the agro-industrial waste (soybean meal, wheat bran, sugarcane bagasse, wheat straw, rice husk, maize flour and maize straw) under solid-state fermentation and obtained several industrially valuable enzymes. Soybean meal appeared to be the most efficient substrate for the single fermentation of B. velezensis 157. Highest yield of pectinase (19.15±2.66Ug-1), cellulase (46.69±1.19Ug-1) and amylase (2097.18±15.28Ug-1) was achieved on untreated soybean meal. Highest yield of xylanase (22.35±2.24Ug-1) was obtained on untreated wheat bran. Here, we report the complete genome sequence of the B. velezensis 157, composed of a circular 4,013,317bp chromosome with 3789 coding genes and a G+C content of 46.41%, one circular 8439bp plasmid and a G+C content of 40.32%. The genome contained a total of 8 candidate gene clusters (bacillaene, difficidin, macrolactin, butirosin, bacillibactin, bacilysin, fengycin and surfactin), and dedicates over 15.8% of the whole genome to synthesize secondary metabolite biosynthesis. In addition, the genes encoding enzymes involved in degradation of cellulose, xylan, lignin, starch, mannan, galactoside and arabinan were found in the B. velezensis 157 genome. Thus, the study of B. velezensis 157 broadened that B. velezensis can not only be used as biocontrol agents, but also has potentially a wide range of applications in lignocellulosic biomass conversion.

Isolation and Identification of a New Cold and Alkaline Tolerant Antibiotic Producing Streptomyces sp. From Soil

Background: The ever-increasing resistance of microorganisms to pathogens and our inability to control infectious diseases indicate the importance of conducting research to find new antibiotics. Objectives: The aim of the present research was to isolate, identify, and optimize a cold and pH resistant strain of Streptomyces with high antibiotic production capability. Methods: Soil samples were taken from the Telar forests of northern Iran, and the ACS52 strain was identified as a Streptomyces strain based on the morphological, biochemical, and 16S rRNA gene analysis. Antibacterial features of the obtained strain were studied against a wide range of Gram-positive and Gram-negative bacteria using the cross-culture method. In order to evaluate the antibacterial activity of culture product, two seed cultures and three fermentation media were examined. Finally, the effects of various factors such as the type of carbon and nitrogen sources, temperature, pH, and inoculation rate were investigated. Results: Streptomyces sp. ACS52 is a cold-resistant alkalophilic bacterium strain with antibacterial activity against a broad spectrum of pathogenic bacteria. The fermentation medium containing glycerol and ethyl acetate was suitable for the production and extraction of antibacterial compound, respectively. Glycerol and starch as the carbon source, soybean extract as the nitrogen source, temperature of 25°C, pH of 7, and inoculation rate of 10% were found to provide the optimal conditions for the antibacterial activity. Conclusions: The crude extract of Streptomyces sp. ACS52 had high antibacterial activity against a wide spectrum of bacteria and could be of interest due to its features such as ability to grow at low temperatures and alkaline pH levels.

Structural genomics for drug design against the pathogen Coxiella burnetii.

Coxiella burnetii is a highly infectious bacterium and potential agent of bioterrorism. However, it has not been studied as extensively as other biological agents, and very few of its proteins have been structurally characterized. To address this situation, we undertook a study of critical metabolic enzymes in C. burnetii that have great potential as drug targets. We used high-throughput techniques to produce novel crystal structures of 48 of these proteins. We selected one protein, C. burnetii dihydrofolate reductase (CbDHFR), for additional work to demonstrate the value of these structures for structure-based drug design. This enzyme's structure reveals a feature in the substrate binding groove that is different between CbDHFR and human dihydrofolate reductase (hDHFR). We then identified a compound by in silico screening that exploits this binding groove difference, and demonstrated that this compound inhibits CbDHFR with at least 25-fold greater potency than hDHFR. Since this binding groove feature is shared by many other prokaryotes, the compound identified could form the basis of a novel antibacterial agent effective against a broad spectrum of pathogenic bacteria.

Detection, identification, and occurrence of thiotetronic acids in drinking water from underground sources by electrospray ionization-high field asymmetric waveform ion mobility spectrometry-quadrupole time-of-flight-mass spectrometry.

This paper demonstrates that electrospray ionization (ESI) with differential ion mobility spectroscopy (FAIMS) and "soft" mass spectrometry (MS) provide unique analytical capabilities that led to the discovery of sulfur-containing polar congeners of thiotetronic acid (TA) in drinking water from underground sources in Canada and the United States. Polar TAs accumulate in underground aquifers and appear to be the most abundant class of organic compounds in bottled water but cannot be detected by conventional mass spectrometry methods. We show that normally stable TAs are converted into very reactive ions in ESI which have to be analyzed using special conditions in ESI-FAIMS-MS to avoid extensive dissociation and ion/molecule reactions. De novo identification of 10 TAs was accomplished by the comparative tandem mass spectrometry analysis of authentic TA derivatives from groundwater samples and synthetic TA analogues prepared for this study. We present highlights of gas phase ion chemistry of polar TAs to explain their unique properties and reactivity. TA derivatives were originally isolated from soil bacteria and are of interest in the pharmaceutical industry due to their potent activity against a broad spectrum of pathogenic bacteria and negligible toxicity to mammals. We suspect that TAs are natural disinfection agents protecting groundwater from bacterial contamination, but these compound undergo modifications or decompose during an ozonation water treatment.

Symbiotic association between hoopoes and antibiotic‐producing bacteria that live in their uropygial gland

Summary 1. It has been recently showed that one bacterial strain isolated from the uropygial gland of a nestling hoopoe Upupa epops produced antimicrobial peptides active against a broad spectrum of pathogenic bacteria. These bacteria might thus mediate antimicrobial properties of the uropygial secretions as a consequence of the symbiotic association with hoopoes. 2. We study antimicrobial properties of white (from males and non-breeding females) and brown (from nestlings and breeding females) uropygial gland secretions of hoopoes Upupa epops , as well as the association with the presence of bacteria living inside their uropygial gland. 3. We found that brown, but not white secretions contained bacteria and showed antimicrobial activity against the feather degrading bacterium Bacillus licheniformis . The antagonistic activity of bacterial colonies was mediated by antimicrobial peptides because protease inhibited antimicrobial properties. 4. All except one identified bacterium in aerobic cultures were of the genus Enterococcus , and the microscopic study of uropygial secretions and glands confirmed a high density of bacteria within the gland. 5. Furthermore, we studied potential benefits of antimicrobial peptides produced by symbiotic bacteria of hoopoes by adding protease to incubating nests. 6. The experiment increased bacterial growth and hatching failures in hoopoes but not in spotless starlings Sturnus unicolor , a species that does not harbour bacteria in its uropygial gland. 7. Thus, microbiological, anatomical and ecological results suggest a tight symbiotic interaction between bacteria that produce antibiotic substances and the hoopoes.

Improved diagnosis specificity in bone and joint infections using molecular techniques

The microbiological diagnosis of osteoarticular infections currently relies on microbiological cultures, to specifically target treatment. However, these conventional methods sometimes lack of sensitivity and of specificity to establish definitive diagnosis. This study was conducted to determine whether molecular method could improve bacterial bone and joint infection diagnosis. We evaluated the performance of nucleic acid extraction with the semi-automated NucliSens miniMAG instrument coupled to 16S rDNA sequencing on 76 samples collected from 51 patients with suspected infections: prosthetic-joint infection (15), spondylodiscitis (7) acute septic arthritis (11) and 18 controls. No pre-treatment of the sample was done before nucleic acid extraction. Classification in infected group required an accumulation of arguments. Our molecular method identified a broad spectrum of pathogenic bacteria including Staphylococcus aureus, Streptococcus pyogenes, Streptococcus agalactiae, Enterococcus faecalis, Salmonella enterica, Escherichia coli, Pseudomonas aeruginosa, and fastidious bacteria like Neisseria gonorrhoeae and Fusobacterium nucleatum. The overall PCR sensitivity was 73.3%: 53.8% for prosthetic-joint infections and 88.2% for infections without prostheses. The overall PCR specificity was 95.2%, whereas culture specificity was only 85.7%. The instrument was simple to use and provided nucleic acids free of PCR inhibitors and free of contamination by foreign bacterial DNA. Our study highlights the need for still improved molecular diagnostic sensitivity.

Photochemical treatment of platelet concentrates with amotosalen and long-wavelength ultraviolet light inactivates a broad spectrum of pathogenic bacteria.

Bacterial contamination of platelet (PLT) concentrates can result in transfusion-transmitted sepsis. A photochemical treatment (PCT) process with amotosalen HCl and long-wavelength ultraviolet light (UVA), which cross-links nucleic acids, was developed to inactivate bacteria and other pathogens in PLT concentrates. High titers of pathogenic aerobic and anaerobic Gram-positive bacteria (10 species), aerobic Gram-negative bacteria (7 species), and spirochetes (2 species) were added to single-donor PLT concentrates containing 3.0 x 10(11) to 6.0 x 10(11) PLTs in approximately 300 mL of 35 percent plasma and 65 percent PLT additive solution (InterSol, Baxter Healthcare) or saline. After PCT with 150 micro mol per L amotosalen and 3 J per cm(2) UVA, residual bacterial levels were detected by sensitive microbiologic methods. The level of inactivation of viable bacteria was expressed as log reduction. Log reduction of Gram-positive bacteria for Staphylococcus epidermidis was > 6.6; for Staphylococcus aureus, 6.6; for Streptococcus pyogenes, > 6.8; for Listeria monocytogenes, > 6.3; for Corynebacterium minutissimum, > 6.3; for Bacillus cereus (vegetative), > 5.5; for Lactobacillus sp., > 6.4; for Bifidobacterium adolescentis, > 6.0; for Propionibacterium acnes, > 6.2; and for Clostridium perfringens, > 6.5. Log reduction of Gram-negative bacteria for Escherichia coli was > 6.4; for Serratia marcescens, > 6.7; for Klebsiella pneumoniae, > 5.6; for Pseudomonas aeruginosa, 4.5; for Salmonella choleraesuis, > 6.2; for Yersinia enterocolitica, > 5.9; and for Enterobacter cloacae, 5.9. Log reduction of spirochetes for Treponema pallidum was 6.8 to 7.0, and for Borrelia burgdorferi, > 6.9. PCT inactivates high levels of a broad spectrum of pathogenic bacteria. The inactivation of bacteria in PLT concentrates offers the potential to prospectively prevent PLT-transfusion-associated bacteremia.

Oligosaccharides in Human Milk and Bacterial Colonization

Oligosaccharides in Human Milk and Bacterial Colonization

An Antimicrobial Activity of Cytolytic T Cells Mediated by Granulysin

Cytolytic T lymphocytes (CTLs) kill intracellular pathogens by a granule-dependent mechanism. Granulysin, a protein found in granules of CTLs, reduced the viability of a broad spectrum of pathogenic bacteria, fungi, and parasites in vitro. Granulysin directly killed extracellular Mycobacterium tuberculosis, altering the membrane integrity of the bacillus, and, in combination with perforin, decreased the viability of intracellular M. tuberculosis. The ability of CTLs to kill intracellular M. tuberculosis was dependent on the presence of granulysin in cytotoxic granules, defining a mechanism by which T cells directly contribute to immunity against intracellular pathogens.

The Effect of Trimethoprim on the Activity of Sulfonamides and Antibiotics in Experimental Infections

The evidence for in vivo potentiation of sulfonamides and antibiotics by trimethoprim (2,4-diamino-5-[3,4,5-trimethoxybenzyl]pyrimidine) is reviewed. The proportion of one part trimethoprim to five parts sulfamethoxazole provides substantially increased protection over that of either substance alone against a broad spectrum of pathogenic bacteria. The simultaneous administration of folinic acid or thymidine does not interfere with the potentiative properties of trimethoprim. In some instances, trimethoprim potentiates the in vivo antibacterial activity of antibiotics, but this effect is not consistent either for a particular antibiotic or for a specific organism.