Chemotherapy of experimental lactational mastitis in mice]

More severe mastitis on infection with Proteus was shown on a standardized model of experimental lactation mastitis of mice caused by Staphylococcus, Proteus and their mixture. Significant differences in the morphological pictures of the staphylococcal and Proteus mastitis were noted. A pronounced effect was observed with the use of kanamycin in combination with fuzidin in treatment of experimental mastitis of various etiology.     

Experimental studies on the ecological role of antibiotic production in bacteria

Summary Genetically well-characterized strains of antibiotic-producing soil bacteria (Streptomyces griseus andStreptomyces coelicolor) were used to examine the ecological role of antibiotic production. Streptomycetes were competed against sensitive and resistantBacillus subtilis, another soil bacterium, on surface (agar) culture. The ecological role of antibiotics was examined in three levels of competition. (1) Capacity of antibiotics to allow invasion of producing organisms (B. subtilis established and streptomycetes added later). (2) Capacity of antibiotics to mediate competition between established populations (B. subtilis and streptomycetes co-inoculated). (3) Capacity of antibiotics to prevent invasion by competitors (streptomycetes established andB. subtilis added later). Antibiotic production was found to play a significant role in preventing the invasion of competitors in these experiments. Antibiotic production did not improve the ability of producers to invade a population of sensitive cells nor did it play a strong role in mediating competition between established populations. Antibiotic production also selected for antibiotic-resistant bacteria among invading competitors.     

The role of lactic acid bacteria in colon cancer prevention: mechanistic considerations

Colorectal cancer is one of the most important causes of cancer morbidity and mortality in Western countries. While a myriad of healthful effects have been attributed to the probiotic lactic acid bacteria, perhaps the most controversial remains that of anticancer activity. It should be pointed out already at this point that there is no direct experimental evidence for cancer suppression in humans as a result of consumption of lactic cultures in fermented or unfermented dairy products. However, there is a wealth of indirect evidence, based largely on laboratory studies, in the literature. The precise mechanisms by which lactic acid bacteria may inhibit colon cancer are presently unknown. However, such mechanisms might include: enhancing the host's immune response; binding and degrading potential carcinogens; quantitative and/or qualitative alterations in the intestinal microflora incriminated in producing putative carcinogen(s) and promoters (e.g. bile acid-degrading bacteria); producing antitumorigenic or antimutagenic compounds in the colon; alteration of the metabolic activities of intestinal microflora; alteration of physicochemical conditions in the colon; effects on physiology of the host. These potential mechanisms are discussed in the present paper.     

Lipoquinones of some bacteria and mycoplasmas,with considerations on their functional significance

In a comparative study the lipoquinones of some chemoorganotrophic, facultatively aerobic bacteria, and representative Acholeplasma, Mycoplasma, Spiroplasma, and Thermoplasma strains were investigated. The quinones were partly purified by preparative thin layer chromatography of lipid extracts, and characterized by their difference spectra (reduced minus oxidized) and R_f values. Respiring bacteria expectedly contained benzoquinones and/or naphthoquinones in micromolar concentrations whereas some aerotolerant, cytochrome-less, gram-positive bacteria were found to contain menaquinones in nanomolar concentrations, or even no quinones; only Streptococcus faecalis, an organism supposed to use a rudimentary, flavin-terminated respiratory chain system produced desmethyl menaquinone in amounts ranging between high and low quinone contents. Among the mycoplasmas investigated, only Thermoplasma acidophilum was found to be capable of synthesizing quinones (MK-7) in the micromolar order of magnitude indicating a respiratory electron transport system. The presence of energetically useful respiratory chain systems in Acholeplasma, Mycoplasma, and Spiroplasma is questioned since these organisms contain quinones (MK-4) in nanomolar concentrations, or no quinones, depending on the presence of exogeneous MK-6 in the growth medium. The possible metabolic role of menaquinones present in low amounts, as well as the role of NADH oxidase systems more or less tightly bound to the cytoplasmic membrane with the mycoplasmas deserves further investigation.     

Multiresistant Gram-negative bacteria: the role of high-risk clones in the dissemination of antibiotic resistance

Multilocus sequence typing reveals that many bacterial species have a clonal structure and that some clones are widespread. This underlying phylogeny was not revealed by pulsed-field gel electrophoresis, a method better suited to short-term outbreak investigation. Some global clones are multiresistant and it is easy to assume that these have disseminated from single foci. Such conclusions need caution, however, unless there is a clear epidemiological trail, as with KPC carbapenemase-positive Klebsiella pneumoniae ST258 from Greece to northwest Europe. Elsewhere, established clones may have repeatedly and independently acquired resistance. Thus, the global ST131 Escherichia coli clone most often has CTX-M-15 extended-spectrum β-lactamase (ESBL), but also occurs without ESBLs and as a host of many other ESBL types. We explore this interaction of clone and resistance for E. coli, K. pneumoniae, Acinetobacter baumannii- a species where three global lineages dominate--and Pseudomonas aeruginosa, which shows clonal diversity, but includes the relatively 'tight' serotype O12/Burst Group 4 cluster that has proved adept at acquiring resistances--from PSE-1 to VIM-1 β-lactamases--for over 20 years. In summary, 'high-risk clones' play a major role in the spread of resistance, with the risk lying in their tenacity--deriving from poorly understood survival traits--and a flexible ability to accumulate and switch resistance, rather than to constant resistance batteries.     

Digestion of bacteria and the role of midgut lysozyme in some insect larvae.

1. Lysozyme is absent from tissues other than the midgut in the drug-feeding larvae of Musca domestica (Diptera, Cyclorrhapha, Muscidae) and in the fruit-feeding larvae of Anastrepha fraterculus (Diptera, Cyclorrhapha, Tephritidae), whereas in the detritus-feeding larvae of Trichosia pubescens (Diptera, Nematocera, Sciaridae) lysozyme is only found in the hemolymph and in the fat body. 2. A. fraterculus larvae have a midgut region with a luminal pH of 3.4, and display a pepstatin-inhibited acid proteolytic activity which has a spec. act. (7.2 U/mg protein) similar to that of M. domestica. 3. The midgut lysozyme from M. domestica and A. fraterculus is more active (high ionic strength) at pH 3.5 than at pH 6.0, the contrary being true for a midgut chitinase. 4. The results suggest that the adaptations to digest bacteria in insects are similar to those in vertebrate foregut fermenters, and that these characteristics were probably present in the Cyclorrhapha ancestor, but not in the Diptera ancestor.     

A survivor of breast cancer with immunity to MUC-1 mucin, and lactational mastitis

 The human mucin, MUC-1, is a transmembrane glycoprotein that is produced by both normal an malignant epithelium. The MUC-1 produced by malignant epithelium is underglycosylated, which leads to the expression by tumors of novel T and B cell epitopes on the mucin polypeptide core. Similar underglycosylation occurs in the lactating breast. In this report, we describe a long-term survivor of breast cancer whose tumor strongly expressed the T- and B-cell-stimulatory epitopes. Five years after presenting with the tumor, the patient had her first pregnancy, at which time she developed fulminant lymphocytic mastitis. We demonstrate that the lactating breast produced mucin expressing the same “tumor-specific” epitopes as the original cancer. The patient had circulating anti-mucin antibodies of both the IgM and IgG isotypes (these are not found in normal controls), and mucin-specific cytotoxic T lymphocytes in the peripheral blood. Limiting  –  dilution analysis for mucin  –  specific cytotoxic T lymphocytes in three different experiments yielded frequencies of 1 in 3086, 1 in 673, and 1 in 583, compared to approximately 1 in 10⁶ in normal controls. The patient remains clinically free of carcinoma after 5 additional years of follow-up. We propose that the original tumor primed the patient’s immune response against the mucin epitopes, and that the re-expression of these epitopes on the lactating breast evoked a secondary immune response. It is tempting to speculate that the vigor of her anti-mucin immunity may have helped protect this patient against recurrent tumor. Received: 12 February 1996 / Accepted: 5 November 1996     

The role of combichem in antibiotic discovery

Combinatorial chemistry (combichem) has had a significant impact on the discovery of new antibiotics. Most of the successes have come from the use of small libraries to explore a specific pharmacophore. However, large diverse libraries are more appropriate when identifying hits by screening specific bacterial or fungal targets. Combichem has been used to optimize new azole and oxazolidinone leads. An entirely new class of antibiotics, inhibitors of bacterial peptidyl-deformylase, has been discovered by combining mechanism-based drug design and combichem. These compounds are active in vivo. The impact of combichem on discovery projects that aim to develop new antibiotics for the treatment of infectious diseases is discussed.     

The activity of some antibiotic combinations onSalmonella

Summary The effects of some antibiotics acting alone or in combination upon 72 strains of variousSalmonella species were investigated usingElek andHilson’s variant ofLederberg’s replica technique. Chloramphenicol and tetracycline were found to act mainly bacteriostatically; streptomycin and neomycin varied in their action from bacteriostatic for some strains to bactericidal for other ones. The action of polymyxin B appeared to be more especially bactericidal. But for a few exceptions no interaction was found between the combinations streptomycin-chloramphenicol and streptomycin-tetracycline. The pair neomycin-chloramphenicol was often antagonistic; neomycin-polymyxin B, on the other hand, prevailingly synergistic. Under the conditions of experimentation a pronounced synergism was noticed between polymyxin B and chloramphenicol. The prospects of the latter synergistic combination as a possibly more radical means of combatingSalmonella infections are shortly discussed. With the technical assistance of MissM. J. Wisse.     

The role of antibiotics and antibiotic resistance in nature

Investigations of antibiotic resistance from an environmental prospective shed new light on a problem that was traditionally confined to a subset of clinically relevant antibiotic‐resistant bacterial pathogens. It is clear that the environmental microbiota, even in apparently antibiotic‐free environments, possess an enormous number and diversity of antibiotic resistance genes, some of which are very similar to the genes circulating in pathogenic microbiota. It is difficult to explain the role of antibiotics and antibiotic resistance in natural environments from an anthropocentric point of view, which is focused on clinical aspects such as the efficiency of antibiotics in clearing infections and pathogens that are resistant to antibiotic treatment. A broader overview of the role of antibiotics and antibiotic resistance in nature from the evolutionary and ecological prospective suggests that antibiotics have evolved as another way of intra‐ and inter‐domain communication in various ecosystems. This signalling by non‐clinical concentrations of antibiotics in the environment results in adaptive phenotypic and genotypic responses of microbiota and other members of the community. Understanding the complex picture of evolution and ecology of antibiotics and antibiotic resistance may help to understand the processes leading to the emergence and dissemination of antibiotic resistance and also help to control it, at least in relation to the newer antibiotics now entering clinical practice.     

The use of real-time PCR for quantitative determination of some propionic bacteria inhabiting the human skin

A test system has been developed for determination of propionic bacterial species inhabiting the human skin. This system developed in the real time PCR format is applicable for quantitative determination and also detection of genomes of the following Propionibacterium species: P. acnes, P. granulosum, and P. avidum. This system was used for analysis of wash samples from the skin of 17 pentathlon sportsmen and 16 students. All three species of propionic bacteria were found in all skin wash samples. However, contamination with P. acnes was two times higher in the control group than in the group of pentathlon sportsmen.     

Changes in the phase variant spectra in the populations of lactic acid bacteria under antibiotic treatment

Effect of the antibiotics kanamycin and ampicillin on the growth and phase variation of the populations of four strains of lactic acid bacteria (Lactobacillus sp. M76AT, L. casei MB, Enterococcus faecium M, and E. faecium M3185) was studied. The presence of antibiotics in the medium resulted in a dose-dependent decrease in viable cell numbers and in partial or complete substitution of the dominant S variant with the minor Sm and Sb variants. The variants differed in colony morphology, as well as in some physiological, biochemical, biotechnological, and probiotic characteristics. The Sm type variants of all strains exhibited the highest resistance to antibiotics. High production of exopolysaccharides was found in Sb variants of lactobacilli and in S variants of enterococci. The highest antibacterial activity was found in Sm variants of lactobacilli, especially in Lactobacillus sp. M76AT. The latter is biotechnologically the most promising strain, since all variants fermented milk yielding the products with uniformly pronounced functional and organoleptic properties. These patterns are of importance for the understanding of the mechanisms of antibiotic resistance and for selection of the variants with desired properties, as well as for quality control of the lactic acid bacteria starter cultures.     

The role of staphylococci in the occurrence, development and chronicity of lactation mastitis

The investigation results obtained by the authors and the data of literature on the role of the biological properties of staphylococci in the pathogenesis, development and chronization of acute suppurative lactation mastitis are generalized. The concept of lactation mastitis as a monoetiological disease caused solely by bacteria of the genus Staphylococcus is substantiated. The importance of the individual properties of staphylococci at different stages of the pathogenesis of lactation mastitis, as well as their role in ensuring the resistance of the infective agent to the protective mechanisms of the body and in the chronization of the suppurative process, is considered. The data on the use of a number of biological properties of staphylococci as markers for the prognostication of the course of lactation mastitis are presented and their prognosticating effect at different tactics of surgical treatment is evaluated.     

Effect of timing of first clinical mastitis occurrence on lactational and reproductive performance of Holstein dairy cows

Objectives of this study were to determine the influence of timing of first clinical mastitis case occurrence on lactational and reproductive performance in high producing lactating dairy cows during the first 320 days in milk (DIM). Holstein cows, 1001, from two commercial dairy farms in California were retrospectively divided into four treatment groups according to timing of first clinical mastitis case caused by environmental pathogens: control with no recorded clinical cases of mastitis (C; n=501); first clinical mastitis prior to first postpartum AI (MG1; n=250); first clinical mastitis between first postpartum AI and pregnancy diagnosis (MG2; n=147); and first clinical mastitis after diagnosed pregnant (MG3; n=103). Clinical cases of mastitis were identified at every milking by the herd personnel based on abnormal milk or swelling of the mammary gland. A fore sample of milk was aseptically collected from every clinical case for microbiological culture. Mastitis decreased yields of milk, 3.5% fat-corrected milk, and milk components, but the effect was only observed for MG1 and MG2. Cows in the control group had lower linear somatic cell count (SCC) score throughout the lactation. Culling was increased by mastitis, and cows in the mastitis groups left the study earlier than controls. Conception rate at first postpartum AI and pregnancy rate at the end of the study were both decreased by mastitis prior to or after first AI, and MG1 and MG2 cows had extended days open. Furthermore, cows experiencing mastitis during lactation had a higher incidence of abortions. The negative effects of mastitis on reproduction were observed regardless of clinical case being caused by either Gram positive or negative bacteria. Mastitis either prior to or after first postpartum AI impairs lactation performance, increases culling, and decreases reproductive efficiency in high producing Holstein dairy cows.