Effects of low concentrations of antibiotics on Escherichia coli adhesion

Pharmacokinetics of oral chlortetracycline in nonpregnant adult ewes

The objectives of this study were to determine plasma concentrations and pharmacokinetic parameters of feed-grade chlortetracycline (CTC) in sheep after oral administration of 80 or 500 mg/head daily, divided into two equal doses given at 12-h intervals for 8 days. These are the approved, and commonly used but unapproved, feed additive doses, respectively, in the United States for the prevention of ovine infectious abortion. Blood samples were collected just prior to dosing at 0, 12, 24, 72, 96, and 192 h, as well as 4, 8, 12, 24, and 36 h after the last dose, and noncompartmental pharmacokinetic analysis was performed to estimate elimination half-life and area under the plasma concentration-time curve (AUC). Mean observed maximum CTC concentrations (Cmax ) were 20.0 ng/mL (80 mg dose) and 101 ng/mL (500 mg dose). Mean apparent elimination half-life was 18 h (80 mg dose) and 20 h (500 mg dose). Although published data do not exist to estimate plasma CTC concentrations necessary for the prevention of ovine infectious abortion, concentrations reached in our study suggest that either the FDA-approved and FDA-unapproved dosages are not high enough or that the pharmacodynamic parameter relating preventive dose to pathogen minimum inhibitory concentrations is yet to be determined.

Effect of the herbicide 2,4-dichlorophenoxyacetic acid on uropathogenic Escherichia coli virulence factors

The effects of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D)-widely used in the world and mainly excreted by the renal route in exposed humans-were studied on the virulence and surface characteristics of an uropathogenic Escherichia coli strain. When the urine was supplemented with 2,4-D in vitro, the compound significantly reduced the bacterial fimbriation assayed by hemagglutination and surface protein quantification. Protein values decreased from 0.24 mg/g dw to 0.05 or 0.12 mg/g dw by 1 or 0.1 mM 2,4-D treatment, respectively. The effects in vivo were studied in groups of mice challenged intra-urethra with E. coli and exposed by the oral route with three different 2,4-D doses (2.6, 25 or 70 mg/kg bw) during 22 days. Depending on the dose used, the herbicide significantly decreased or removed bacterial cells in mice bladder and kidneys; except in the group treated with the highest dose from the 9th day of treatment. The histological studies showed mononuclear cell infiltration at low doses, and toxic damage in the renal parenchyma at prolonged exposure with higher doses, up to tisular necrosis in the 70 mg/kg bw group after 9 days of treatment. Our investigations performed in an experimental model suggest that short time 2,4-D exposure at low doses could act in prevention of UTI stimulating leukocytic migration and decreasing bacterial fimbriation. On the contrary, high doses and long-term exposure enhanced renal damage resulting in infection recurrence.

[Prevention of reinfection by L-methionine in patients with recurrent urinary tract infection]

PROBLEM

A great variety of different antimicrobial chemotherapeutics is available for the treatment of urinary tract infections. Influencing the course of chronic diseases is a problem because recurrent diseases may result in disturbances of renal and bladder functions as well as in irreversible damages of the renal parenchyma. The present investigations are expected to clarify whether an effective prevention of reinfection in patients with chronically recurrent urinary tract infection is possible by a regular administration of L-methionine (Acimethin).

PATIENTS AND METHODS

33 female patients were included in the examinations. Following acute disease, 23 females (aged: 47.4 +/- 13.3 years) were treated with 3 x 1 tablet of Acimethin (L-methionine) daily over a period of 26 months. Ten female patients (aged: 47.4 +/- 12.2 years) taking 1 tablet of Nevigramon (nalidixic acid) three times daily over 21.6 months served as a control group. Before starting treatment and in the middle of the therapy period control examinations were performed and following the last drug administration so as to assess the therapeutic result.

RESULTS

No acute infection occurred during L-methionine treatment. All parameters of inflammation (leucocyte count, C-reactive protein, blood sedimentation rate, alpha 2-globulin concentration) were in the normal range; no impairment of renal function was observed. Although L-methionine, i.e. nalidixic acid, did not yield any significant changes in the range of bacteria, the adherence of uropathogenic microorganisms to the cells of the urinary tract was reduced. Before L-methionine treatment, the average load of the uroepithelial cells was 95.9 +/- 73.6 bacteria per cell. When the observation period was completed, 51.2 +/- 56.4 bacteria per cell were registered (p < 0.03). During nalidixic acid treatment, the rate of adherence was reduced from 74.0 +/- 88.4 to 34.4 +/- 37.8 bacteria per cell (p < 0.25). During L-methionine treatment, no Escherichia coli strains that are able to produce hemolysin or to form aerobactine were found. Among agents adhering to uroepithelial cells, however, an increase in their ability to produce mannose-resistant hemagglutination was conspicuous.

CONCLUSION

L-methionine is suitable to prevent reinfection with chronic urinary tract infection. The therapeutic result is essentially due to its influence on bacterial cytoadherence. In contrast to the established recommendations concerning the prevention of reinfection by the use of antibiotics and sulphonamides selecting resistant strains during long-term treatment, nothing is known about the development of resistance to L-methionine.

Preservative-mediated changes of the surface properties of Escherichia coli

The effectiveness of two commonly used preservatives, sodium benzoate and potassium disulfite, was evaluated in terms of their bactericidal activity and capacity to induce changes in the surface properties of Escherichia coli isolated from commercial food preserves. Preservative treatment over a five-week test period resulted in controlling the multiplication of these organisms and causing a decline in cell-surface hydrophobicity, hemagglutinating ability and adherence capacity to rat intestinal cells of E. coli isolates. A loss in motility was also exhibited.

The role of the pharmaceutical animal health industry in post-marketing surveillance of resistance

The pharmaceutical animal health industry must be committed to the total life cycle of products, i.e. during both the pre- and post-marketing period. Support of antibacterial agents during the postmarketing period is not restricted to maintaining a well-established distribution and promotion system. Care has to be taken continuously to maintain and/or improve the quality, safety (for user, target animal and environment) and clinical efficacy. The pharmaceutical industry contributes to this by: 1. Introducing antibacterials in different animal species for the most effective disease condition only and by ensuring the veterinary profession is informed about relevant findings on: a. the mechanism of action; b. pharmacodynamic properties; c. pharmacokinetic properties (plasma, target tissue); d. clinical efficacy data and in vitro sensitivity data; e. valid species-specific MIC breakpoints; f. precise dose and treatment regime. 2. Updating on a regular basis on: a. new findings on the mechanism of action (in vitro and in vivo); b. the optimal use program in the light of changes in animal husbandry, farm management and epidemiology on national and international level; c. adjustment of species-specific MIC breakpoints when necessary. 3. Providing continuous information in collaboration with animal health laboratories about: a. clinical field surveillance for efficacy (national, international); b. in vitro sensitivity/resistance surveillance (national, international); c. use of in vitro data to support prediction of in vivo efficacy. Surveillance of resistance, in vitro, is therefore part of a package of information needed on a routine basis by the pharmaceutical industry to allow the best possible use of antibacterials and to minimize induction of resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in adherence of respiratory pathogens to HEp-2 cells induced by subinhibitory concentrations of sparfloxacin, ciprofloxacin, and trimethoprim

Preincubation with subinhibitory concentrations of sparfloxacin, ciprofloxacin, and trimethoprim decreased the adherence of the respiratory pathogens Klebsiella pneumoniae, Haemophilus influenzae, and Moraxella (Branhamella) catarrhalis to human larynx carcinoma HEp-2 cells. Subinhibitory concentrations of sparfloxacin did not change the adherence of Pseudomonas aeruginosa or Streptococcus pneumoniae 15.62, but adhesion of S. pneumoniae 15.42 was significantly enhanced by subinhibitory antimicrobial concentrations.

Virulence factors in Escherichia coli urinary tract infection

Uropathogenic strains of Escherichia coli are characterized by the expression of distinctive bacterial properties, products, or structures referred to as virulence factors because they help the organism overcome host defenses and colonize or invade the urinary tract. Virulence factors of recognized importance in the pathogenesis of urinary tract infection (UTI) include adhesins (P fimbriae, certain other mannose-resistant adhesins, and type 1 fimbriae), the aerobactin system, hemolysin, K capsule, and resistance to serum killing. This review summarizes the virtual explosion of information regarding the epidemiology, biochemistry, mechanisms of action, and genetic basis of these urovirulence factors that has occurred in the past decade and identifies areas in need of further study. Virulence factor expression is more common among certain genetically related groups of E. coli which constitute virulent clones within the larger E. coli population. In general, the more virulence factors a strain expresses, the more severe an infection it is able to cause. Certain virulence factors specifically favor the development of pyelonephritis, others favor cystitis, and others favor asymptomatic bacteriuria. The currently defined virulence factors clearly contribute to the virulence of wild-type strains but are usually insufficient in themselves to transform an avirulent organism into a pathogen, demonstrating that other as-yet-undefined virulence properties await discovery. Virulence factor testing is a useful epidemiological and research tool but as yet has no defined clinical role. Immunological and biochemical anti-virulence factor interventions are effective in animal models of UTI and hold promise for the prevention of UTI in humans.

Mutations in cloned Escherichia coli P fimbriae genes that makes fimbriae-production resistant to suppression by trimethoprim

The effect of sublethal concentrations of trimethoprim on the expression of P fimbriae was tested in Escherichia coli HB101 recombinant strains. Fimbriation was inhibited at trimethoprim concentrations down to at least 1/64 of the minimal inhibitory concentration. However, the expression of the P fimbrillin by recombinant plasmids containing deletions in front of the fimbrillin gene did not respond to the inhibitory effect of trimethoprim indicating that trimethoprim may act at the level of gene regulation.

Quantitation of effects of subinhibitory concentrations of trimethoprim on P fimbria expression and in vitro adhesiveness of uropathogenic Escherichia coli

The ability to adhere to and colonize urogenital mucosa is an important virulence attribute of uropathogenic Escherichia coli. This adherence, which appears to be mediated by P fimbriae, may be affected by antibiotics or other agents that affect fimbrial expression. We describe here an enzyme immunofiltration assay to quantitate fimbriation and the application of that technique to measurement of the effects of sublethal doses of trimethoprim on P fimbrial expression. Effects on P fimbriation correlated with effects on the adherence of treated bacteria to cultured T24 bladder carcinoma epithelial cells; i.e., trimethoprim treatment decreased both P fimbriation and bacterial adherence. It was possible to quantitate effects on P fimbriation when type 1 fimbriae were also present. The enzyme immunofiltration assay may be useful for studies on the role of fimbriae in the pathogenesis of bacterial infections, and it may facilitate identification of antimicrobial agents that interfere with bacterial adherence to mucosal surfaces.

The sugar-specific adhesion/deadhesion apparatus of the marine bacterium Vibrio furnissii is a sensorium that continuously monitors nutrient levels in the environment

Our earlier studies on cell adhesion to immobilized carbohydrates are extended here to a marine bacterium, Vibrio furnissii. Apparently one lectin mediates the binding of these cells to glycosides of N-acetylglucosamine, mannose, and glucose covalently linked to Agarose beads. Kinetic studies show that protein synthesis is required for initiating and for maintaining adhesion to the glycosides. Furthermore, a pro- mutant binds to GlcNAc-beads at Pro concentrations insufficient to support cell growth. Expression of the functional lectin therefore predominates under conditions of limiting protein synthesis. Thus, cells adhere to the sugars in an environment compatible with protein synthesis, and deadhere when depleted of any required nutrient, presumably to migrate to a more favorable locale. The adhesion-deadhesion apparatus thereby permits constant monitoring of the surrounding environment, comprising a "nutrient sensorium".

Trimethoprim used for selective decontamination of the digestive tract in rats: possible route of excretion

Selective elimination of Enterobacteriaceae species from the digestive tract of rats has been accomplished by oral treatment with trimethoprim (235 mg/kg body weight/day) within 6 days. In the present study it was investigated whether this elimination was mainly due to antimicrobial activity of trimethoprim excreted with the gastrointestinal mucus or mainly by non-absorbed trimethoprim in the lumen contents. By means of whole gut irrigation (WGI) the lumen contents were washed out, followed by mucosa-associated flora. The concentration of the mucosa-associated Enterobacteriaceae remained at least 10(1)/ml as measured in the last samples of rectal effluent during WGI in untreated rats. During trimethoprim treatment, however, the amount of mucosa-associated Enterobacteriaceae had decreased significantly more (p less than 0.05) compared with the Enterobacteriaceae present in the lumen contents of the gastrointestinal tract (photospectrometrically measured by the color of the rectal effluent). No difference was observed in the concentration of mucosa-associated enterococci in the rectal effluent of trimethoprim treated and untreated rats. It is concluded that orally administered trimethoprim may be predominantly active against Enterobacteriaceae associated with the mucous blanket.

Induction of inflammatory mediators from human polymorphonuclear granulocytes and rat mast cells by haemolysin-positive and -negative E. coli strains with different adhesins

We investigated the role of various E. coli strains that expressed different adhesins and/or generated haemolysin with regard to the induction of inflammatory mediators, e.g. histamine release from rat mast cells as well as the chemiluminescence response and the release of lipoxygenase transformation products from human polymorphonuclear neutrophils. Our data show that the degree of haemagglutination did not parallel the induction of the chemiluminescence response. Haemolysin-negative bacteria with different adhesins induced more 5-hydroxyeicosatetraenoic acid as compared to haemolysin-positive bacteria, which generated more leukotriene B4 as compared to 5-hydroxyeicosatetraenoic acid. Among the leukotrienes, more leukotriene B4 as compared to leukotriene C4 was released from peripheral leucocytes. Studies with rat mast cells showed that histamine release was dependent on the haemolysin activity expressed by washed bacteria or present within the bacterial culture supernatant. Histamine release was markedly diminished when haemolysin activity decayed. Several haemolysin-negative bacteria with defined adhesins also released histamine, suggesting that, in addition to haemolysin, other factors contribute to mediator release. Thus, various properties of bacteria (e.g. adhesins, haemolysin) may participate to varying degrees in the induction of inflammatory mediators, e.g. oxygen radicals, lipoxygenase transformation products, leucotrienes and histamine.

[Effect of subinhibitory concentrations of penicillin on antigens of group G streptococci]

O efeito de concentrações subinibitórias de penicilina sobre a produção do antígeno grupo-específico e da hialuronidase extracelular foi avaliado em uma amostra de estreptococo pertencente ao grupo G de Lancefield. Em todas as concentrações uma maior quantidade de antígeno grupo-específico foi extraída das células e a atividade específica de hialuronidase se mostrou aumentada em até 1400% nos sobrenadantes das culturas. O maior aumento na expressão de ambos os antígenos foi observado em 1/2 da CMI.

Pseudomonas aeruginosa virulence factors: modifications by sub-inhibitory concentrations of carbenicillin or gentamicin

A virulent strain of Pseudomonas aeruginosa was assayed for adhesion to HEp-2 cells, production of toxin A, and production of elastase, in the presence of sub-inhibitory concentrations of carbenicillin and gentamicin. Both antibiotics, assayed in a concentration of 1:12 of their minimum bactericidal concentration (MBC), inhibited the production of toxin A. Gentamicin at this concentration totally abolished the production of elastase, whereas carbenicillin had little or no effect on this factor. Both antibiotics inhibited the bacterial adhesion, but in different ways. While gentamicin had a strong activity of slow onset, carbenicillin had a transitory activity of rapid onset, with return towards normal values after 90 min incubation.

Adhesion of Gardnerella vaginalis to vaginal epithelial cells: variables affecting adhesion and inhibition by metronidazole

Variables affecting the adherence of Gardnerella vaginalis to human vaginal epithelial cells were examined in vitro. Adherence depended on pH, with maximum attachment occurring between pH 5 and pH 6. Preincubation of the bacteria at 56 degrees C for 30 minutes and ultraviolet irradiation resulted in a noticeable decrease in adherence. In contrast, adherence was not altered by preincubating the epithelial cells under these conditions. Periodate oxidation of the vaginal cells caused an appreciable reduction in subsequent adherence of G vaginalis. None of the 19 single carbohydrates tested inhibited adherence completely. Metronidazole at subinhibitory concentrations for G vaginalis, appreciably reduced the adhesive capacity of G vaginalis, whereas subinhibitory concentrations of ampicillin did not.

Effects of antimetabolites on the adhesion of an estuarine Vibrio sp. to polystyrene

The effect of various metabolic inhibitors and antibiotics on the adhesion of an estuarine bacterium, Vibrio proteolytica, to polystyrene was investigated. Cells were either exposed to the substratum and the antimetabolite simultaneously or grown in the presence of a 25% MIC and presented the substratum in the absence of the antimetabolite. Based on the response elicited, these inhibitors could be divided into three classes: (i) those that had little or no effect on adhesion (fluorodeoxyuridine and nalidixic acid); (ii) those that only inhibited adhesion after growth at the 25% MIC (ampicillin, oxacillin, and streptomycin); and (iii) those that inhibited attachment when administered simultaneously with the substratum (azide, dinitrophenol, chloramphenicol, puromycin, azauridine, rifampin, p-chloromercuribenzoate, and cephalothin). Cells killed by heating, Formalin, or mercuric chloride treatment were also less adhesive than viable cells. Collectively, these results indicate that (i) physiologically active cells are more adhesive than dead or physiologically impaired cells, (ii) impairment of cell wall synthesis by beta-lactam antibiotics renders cells less adhesive, and (iii) energy production and protein synthesis (including transcription) are both involved in some aspect of the adhesion process, whereas DNA synthesis is not.

Increased phagocytosis and killing of Escherichia coli treated with subinhibitory concentrations of cefamandole and gentamicin in isolated rat livers

Our purpose was to study whether treatment of Escherichia coli with subinhibitory concentrations of either cefamandole or gentamicin could change bacterial susceptibility to the serum bactericidal effect and to the phagocytic and killing activity of the rat liver reticuloendothelial system. Bacteria were grown overnight with 1/5 or 1/10 of the MIC of each antibiotic. At one-fifth of the MIC, cefamandole induced filamentous elongated bacteria whose viability was decreased by 75%. The susceptibility of control and antibiotic-treated bacteria to serum was tested by measuring the survival of organisms exposed to different concentrations of rat serum in vitro. Susceptibility of bacteria to hepatic macrophage activity was tested by following the hepatic clearance of bacteria after they were added to the perfusate of the isolated rat liver. E. coli treated with subinhibitory concentrations of cefamandole or gentamicin appeared somewhat more resistant to the lytic activity of serum at a concentration of 4%, but not at 20%. Bacteria treated with 1/5 or 1/10 of the MIC of cefamandole or with 1/5 of the MIC of gentamicin were significantly more susceptible to phagocytosis and to the bactericidal activity of liver macrophages. Cefamandole appeared more potent than gentamicin in inducing these effects. The results suggest that subinhibitory levels of antibiotics may alter bacterial cell surface (cefamandole) or may impair the expression of antiphagocytic material (gentamicin), thus favoring phagocytosis and killing by macrophages. Our study provides evidence that antibiotics at subinhibitory concentrations may cooperate with host defence mechanisms against bacterial infections.

Adhesion of Proteus species to various cell types

Pathogenic and saprophytic Proteus strains from the urine of patients with urinary tract infections and healthy adults respectively were evaluated with regard to their ability to adhere in vitro to homologous cells (uroepithelial cells from urinary sediment and cultured WISH cells) and heterologous cells (RK-13 and MDCK cells). The effect on attachment of pretreating bacteria with subinhibitory concentrations of piperacillin and sagamicin was also determined for one sensitive and one resistant strain. Fifty percent of the pathogenic Proteus strains demonstrated good adherence to human urinary epithelial cells, whereas saprophytic strains did not adhere. There was a lower rate of attachment to culture cells. Piperacillin and sagamicin in subinhibitory concentrations caused a decrease in the attachment of the sensitive Proteus strain.

Effect of subminimal inhibitory concentrations of antimicrobial agents on the piliation and adherence of Neisseria meningitidis

Neisseria meningitidis is known to be highly resistant to lincomycin (minimum inhibitory concentration greater than 32 micrograms/ml). However, during studies on meningococcal piliation, we noticed a significant reduction in the number of pili after cultivation on lincomycin-containing selective media. This observation was followed up by in vitro and in vivo studies on the relation between lincomycin and meningococcal adherence to human epithelial cells. We found a remarkable decrease in in vitro piliation and adherence after exposure to lincomycin at concentrations as low as 0.05 micrograms/ml. By giving four healthy meningococcal carriers lincomycin orally for 3 to 6 days, the possible in vivo effect of lincomycin was studied. A marked decrease in the meningococcal counts of the pharyngeal secretion was observed. One person completely lost his meningococcal strain during the observation period.

The effect of antibiotics on mannose-resistant haemagglutination by K88- and K99-positive Escherichia coli strains

Five E. coli strains carrying K99 antigen isolated from the intestines of calves which had succumbed to diarrhoea and six K88-positive strains isolated from fatal cases of diarrhoea in piglets were examined for their mannose-resistant haemagglutination (MRHA) capacity against pig erythrocytes. The bovine strains showed a geometric mean MRHA-titre of 1/18 and the porcine strains one of 1/45. Similar experiments were carried out after addition of the following antibiotics in doubling dilutions: ampicillin, chloramphenicol, colistin, dihydrostreptomycin, gentamicin, neomycin, polymyxin B and oxytetracycline. Colistin and polymyxin B had a marked concentration-dependent inhibitory effect on MRHA. Neomycin and gentamicin also inhibited MRHA but to a lesser degree. Chloramphenicol, dihydrostreptomycin and oxytetracycline showed no effect. With ampicillin, a trend was found for the ratio values to be inversely proportional to the concentration. This suggests that this antibiotic has an enhancing effect on the haemagglutination.