Intestinal health of broilers challenged with Eimeria spp. using functional oil blends in two physical forms with or without anticoccidials

This study aimed to assess the impact of a commercial blend of functional oils, specifically cashew nutshell liquid and castor oil (FO), in two physical forms (solid: P; liquid: S), in comparison to a combination of virginiamycin and anticoccidials on the gut health of broilers challenged with coccidiosis. A total of 1760 1-day-old male chicks were randomly distributed in a study design with eight treatments. The treatments included: a control group (without additive), OFS_0.75_kg/t (FO spray), OFP_1.0_kg/t (FO powder), OFP_1.5_kg/t (FO liquid spray), Sal (anticoccidials), Sal_Vir (virginiamycin and anticoccidials), Sal_OFS_0.5_ kg/t (anticoccidials plus FO spray), and Sal_OFP_1.0_kg/t (anticoccidials plus FO powder). All birds were challenged with Eimeria spp. at 14 days. The physical form of FO did not affect performance and intestinal health parameters. At 42 days, broilers from the control and OFS_0.75 treatments were the lightest, while those from the Sal_Vir and Sal_OFP_1.0 treatments were the heaviest (P < 0.05). FO reduced the presence of Clostridium perfringens. The individual phytogenic additives did not prevent weight loss in birds challenged with Eimeria, but they mitigated the effects of the infection by modulating the intestinal microbiota. A synergistic effect was observed between the FO and anticoccidials, yielding satisfactory results in substituting virginiamycin.

Dissemination of Quinupristin-Dalfopristin and Linezolid resistance genes among hospital environmental and healthy volunteer fecal isolates of Enterococcus faecalis and Enterococcus faecium

BACKGROUND

Streptogramins and linezolid are important in the treatment of infections caused by vancomycin-resistant enterococci.

PURPOSE

Then, we aimed to evaluate the resistance rates against these drugs and the prevalence of genes involved in hospital environmental and fecal normal-flora isolates of Enterococcus faecalis and Enterococcus faecium.

METHODS AND RESULTS

The strains were isolated from the stool samples and hospital environments by culturing on M-Enterococcus (ME) agar, and identified by phenotypic and genotypic microbiological tests. The disk agar diffusion method was used to identify the antimicrobial susceptibility pattern of the isolates. The genomic DNA extraction was done by the alkaline lysis method, and the PCR test was used to detect the resistance genes. A total of 145 enterococci isolates were taken, from which 84 (57.9%) isolates were detected as E. faecalis and 61 (42.06%) isolates were E. faecium. Moreover, 70 (83.33), 4 (4.76%), 1 (1.19%), and 40 (47.61%) isolates of E. faecalis and 20 (32.78%), 1 (1.63%), 4 (6.55%), and 26 (42.62%) E. faecium isolates were resistant against quinupristin-dalfopristin, linezolid, vancomycin, and erythromycin, respectively. Also, 112 (77.24%), 50 (34.48%), 39 (26.89%), 27 (18.62%), 19 (13.1%), 4 (2.75%), and 1 (0.68%) isolates were contained LsaA, vatD, vgbB, vatE, cfr, lsaE and optrA genes, respectively. None of the isolates carried the vgbA gene.

CONCLUSIONS

High-level streptogramin resistance rate and high prevalence of resistance genes in enterococci isolated from the stool of healthy persons and the hospital environment indicates the importance of possible transmission of resistance genes from these isolates to clinical ones.

Monensin associated or not with virginiamycin or functional oil for feedlot beef cattle

The objective of this study was to evaluate diets containing monensin (MON) associated or not with virginiamycin (VM) or functional oil based on cashew nut shell and castor beans (FO_cc) for beef cattle in feedlots on nutritional (intake and digestibility) and productive parameters. A total of 1410 non-castrated Nellore cattle were selected, with an average age of 18 months and with an initial mean body weight (BW) of 305 ± 41.52 kg. The diet showed a roughage to concentrate ratio of 23:77, with the supply of corn silage as a source of roughage. The following additive inclusions in the diet were evaluated: (1) MON: 27 mg MON/kg dry matter (DM); (2) MON + VM: 22 mg MON/kg DM + 19 mg VM/kg DM; and (3) MON + FO_cc: 22 mg MON/kg DM + 500 mg FO_cc/kg DM. Statistical analyses were obtained through a linear model using initial BW and days of feedlot as covariables and comparisons between treatments using mutually orthogonal linear contrasts with a 5% significance level. The association or not of MON with VM or FO_cc does not affect any of the nutritional and productive parameters evaluated. Animals that receive diets with MON + VM have higher average daily gain and feed efficiency (FE) than those that receive MON + FO_cc without showing differences in nutritional parameters. The supply of MON associated with VM or FO_cc does not increase intake and productive performance and, consequently, efficiency of feedlot beef cattle. However, in the case of use associated with MON, the VM provides greater performance than FO_cc without changing food intake.

New bisanthraquinone antibiotics and semi-synthetic derivatives with potent activity against clinical Staphylococcus aureus and Enterococcus faecium isolates

The escalation of antibiotic resistance among Gram-positive pathogens presents increasing treatment challenges and requires the development of innovative therapeutic agents. Here, we present the antimicrobial properties of structurally unusual bisanthraquinone metabolites produced by a marine streptomycete and four semi-synthetic derivatives. Biological activities were measured against clinically derived isolates of vancomycin-resistant Enterococcus faecium (VRE), and methicillin-susceptible, methicillin-resistant, and tetracycline-resistant Staphylococcus aureus (MSSA, MRSA, and TRSA, respectively). The most potent antibiotic displayed MIC(50) values of 0.11, 0.23, and 0.90microM against a panel (n=25 each) of clinical MSSA, MRSA, and VRE, respectively, and was determined to be bactericidal by time-kill analysis.

The precautionary principle in times of intermingled uncertainty and risk: some regulatory complexities

This article explores the use of the precautionary principle in situations of intermingled uncertainty and risk. It analyses how the so-called uncertainty paradox works out by examining the Pfizer case. It reveals regulatory complexities that result from contradictions in precautionary thinking. In conclusion, a plea is made for embedment of uncertainty information, while stressing the need to rethink regulatory reform in the broader sense.

Implications of multiple antimicrobial-resistant enterococci associated with the poultry environment

Poultry are increasingly being associated with carriage of multiresistant organisms that may cause disease in humans. Among these organisms are the enterococci, not regarded as a common cause of hospital-acquired infections. The use of antimicrobials for growth promotion in poultry production envronments may facilitate the dissemination of resistance to Enterococcus spp. that have the potential to be clinically significant. To assess descriptively the degree of multiresistant enterococci in the poultry environment of the Delmarva (Delaware-Maryland-Virginia) East Coast region of the USA, litter samples from regional commercial poultry houses and transport container swabs from processing facilities were cultured for Enterococcus spp. Using a microtiter plate adaptation of a conventional biochemical screen, the predominant species identfied were E. faecalis (61.2%), E. faecium (18.6%) and E. gallinarum (2.4%). Resistance to the cephalosporin, macrolide and tetracycline classes of antimicrobials was uniform with broader resistance to penicillin and derivatives present in a majority of E. faecium isolates. High-level streptomycin resistance was evident in close to 30% of all isolates with a majority of E. faecalis variants possessing resistance. High-level gentamicin resistance was detected at a low frequency (2.6%) only within the E. faecalis group with resistance to low-level gentamicin levels present in a majority of both the E. faecalis group and subsets of E. faecium. No unexpected vancomycin resistance was detected. Of particular interest was resistance to the streptogramin quinupristin-dalfopristin (Q-D or Synercid), which was present in 70.4% of E. faecium and E. faecium variants.

Assays to detect and characterize synthetic agents that inhibit the ErmC methyltransferase

High throughput chemical file screening with an enzymatic assay to detect inhibitors of the ErmC methyltransferase enzyme from macrolide-lincosamide-streptogramin B (MLSB) resistant pathogenic bacteria identified low molecular weight compounds that had IC50S (50% inhibitory concentration) in the nMolar to microMolar range. These same inhibitors were assessed in vitro for their capacity to inhibit the liver enzyme, cathechol-O-methyltransferase and the prokaryotic enzyme, EcoRI methylase. Selective inhibitors of the ErmC methyltransferase were tested in tertiary assays to determine their minimal inhibitory concentrations (MICs), as single agents and in combination with the macrolide, azithromycin, against strains of pathogenic bacteria expressing MLSB-resistance. Compounds that were active in vitro, alone or in combination with azithromycin, against strains of macrolide-resistant pathogens were tested in a mouse model of infection using an MLSB-resistant strain of Staphylococcus aureus or a macrolide-susceptible strain of Streptococcus pyogenes.

Comparative in vitro activities of pristinamycin and other antimicrobial agents against genital pathogens

The MICs of pristinamycin for genital pathogens were compared with those of ampicillin, tetracycline, erythromycin, and ciprofloxacin. Pristinamycin was active against all the strains studied. Because of this activity and its lack of toxicity, pristinamycin might be a valuable therapeutic agent for treating major sexually transmitted diseases.

In vitro susceptibilities of Rickettsia rickettsii and Rickettsia conorii to roxithromycin and pristinamycin

In vitro susceptibilities of Rickettsia rickettsii and Rickettsia conorii to roxithromycin, pristinamycin, and the pristinamycin compounds, P1 and P2, were determined by a dye uptake assay and a plaque assay. The MICs were 1 microgram/ml for roxithromycin, 2 micrograms/ml for pristinamycin, greater than 256 micrograms/ml for P1, and 2 micrograms/ml for P2. Compounds P1 and P2 did not share synergetic activity. The toxicity of each compound was determined by a dye uptake assay. Toxic concentrations were 128 micrograms/ml for roxithromycin, 32 micrograms/ml for pristinamycin, greater than 256 micrograms/ml for P1, and 32 micrograms/ml for P2. Roxithromycin and pristinamycin could be useful in the treatment of Rocky Mountain spotted fever and Mediterranean spotted fever.

Resistance of two strains of Streptococcus pneumoniae to pristinamycin associated with 16-membered macrolides

Two strains of Streptococcus pneumoniae isolated from haemocultures show a phenotype resistance which has never been described within this species. This a is a dissociation between resistance and sensitivity within the macrolides group, associated with global resistance as regards pristinamycin (SA + SB).

In-vitro activity of pristinamycin and its components against gram-negative anaerobic bacilli and Gardnerella vaginalis

The comparative in-vitro activities of pristinamycin, its components pristinamycins I and IIA, erythromycin, clindamycin and metronidazole were studied against 174 clinical isolates of Gram-negative anaerobic bacilli and 24 strains of Gardnerella vaginalis. Susceptibilities were determined with an agar-dilution method. Against Bacteroides and Fusobacterium, pristinamycin was slightly less active than both clindamycin and metronidazole and more active than erythromycin. Against G. vaginalis, the activity of pristinamycin was similar to that of clindamycin and slightly inferior to that of erythromycin. Both pristinamycins I and IIA alone were generally inactive against the strains tested. Additionally, MICs for the B. fragilis group determined by a broth microdilution technique were one to two log2 lower than MICs obtained by agar-dilution. The bactericidal activity of pristinamycin and clindamycin was moderate and varied according to the strains tested. The chequerboard broth microdilution test against 20 strains of the B. fragilis group confirmed the synergy between pristinamycins I and IIA at every PI/PIIA ratio. Along with the activity against Neisseria gonorrhoeae, Chlamydia trachomatis, Mycoplasma and both aerobic and anaerobic Gram-positive bacteria, our results suggest that pristinamycin could be an effective drug in the treatment of gynaecological infections.

Comparative in vitro activities of pristinamycin, its components, and other antimicrobial agents against anaerobic bacteria

Using an agar dilution technique, we compared the activities of pristinamycin and its components PIA and PIIA with those of penicillin G, cefoxitin, chloramphenicol, metronidazole, and clindamycin against 200 strains of anaerobic bacteria isolated from suppurative lesions. The antimicrobial activity of pristinamycin was similar to that of chloramphenicol. On the basis of these results and because of its antistaphylococcal and antistreptococcal activities and its absence of toxicity, pristinamycin might be a valuable therapeutic agent for treating mixed aerobic-anaerobic cutaneous infections.

[Corynebacterium group D2. Clinical study, biochemical identification and antibiotic sensitivity]

The comparative study of 44 isolates of Corynebacterium group D2, from urine, most frequently, shows the pathogenic role of these bacteria in urinary tract infection, with or without urinary stones. These microorganisms have an opportunistic behaviour in other non-urinary sites, and become pathogen in immunosuppressed conditions. The rapid tests as urease, glucose acidification, nitrate reductase, associated with multiple resistance to antibiotics (beta-lactams and aminosides) identify easily Corynebacterium group D2, from 48 h cultures under CO2 conditions. The results of MIC determination of 10 antibiotics, show the high activity (100% sensitivity) of vancomycin and pristinamycin, with MIC modes, respectively, 0.5 and 0.03 mg/l. These antibiotics are the most useful for the treatment of non-urinary infections. Among quinolones, the most active agents are ciprofloxacin and ofloxacin (MIC modes: 4 and 2 mg/l), so these antimicrobials could be used for the treatment of urinary tract infections caused by Corynebacterium group D2.

In-vitro susceptibility of oral streptococci to pristinamycin

The inhibitory activity of pristinamycin against oral streptococci was compared with that of amoxycillin, erythromycin and vancomycin. Minimum inhibitory concentrations (MICs) of pristinamycin ranged from 0.03-1 mg/l (mode 0.25 mg/l), similar to those for amoxycillin. Erythromycin had a mode MIC of 0.06 mg/l and vancomycin, the least active, 1 mg/l. However, in killing curve experiments to compare the bactericidal activities of pristinamycin and erythromycin against several strains of oral streptococci, pristinamycin was substantially more active, consistently producing a rapid decrease in viable count during the first few hours of incubation. Pristinamycin may prove to be of value for the prophylaxis of post-dental extraction bacteraemia.

Irreversible binding of pristinamycin IIA (streptogramin A) to ribosomes explains its "lasting damage" effect

In vitro and in vivo studies are presented to test the hypothesis that the synergistic action of the pristinamycins is not due to a catalytic effect of pristinamycin IIA (PIIA) on the bacterial ribosome. We demonstrate that there is a proportionality between the quantity of PIIA bound on the ribosome and pristinamycin IA (PIA) retained by it. Moreover in vitro and in vivo experiments correlated to biological effects (growth and protein synthesis) demonstrate that pristinamycin IIA is tightly bound on 70S ribosome, which satisfactory explains the so called "lasting damage effect".

Comparative efficacy of pefloxacin and six other antimicrobial agents on Staphylococcus aureus experimental abscesses

Pefloxacin (Pef) is a new quinolone which has been shown to have good in-vitro activity against Staphylococcus aureus, and to reach high tissue concentrations. Its efficacy was compared to that of 2 quinolone derivatives, norfloxacin (Nor) and ciprofloxacin (Cip) and to that of methicillin (Meth), cephalothin (Cep), pristinamycin (Pri) and vancomycin (Van), in an experimental model of S. aureus abscesses. Mice challenged with an intramuscular thigh injection of a calibrated inoculum developed local abscesses. Three S. aureus strains (with different antibiotic resistance profiles (Pase-, Pase+, MethR)) were used. In this model, the antibiotics showing the best ED50 following oral administration, against all three strains were Pef greater than Cip greater than Pri greater than Nor, by subcutaneous administration for the Pase- strain Pef = Cip greater than Cep greater than Van; for the Pase+ strain Pef = Cip greater than Van greater than Meth and for the Pase+ MethR strain: Pef = Cip greater than Van greater than Cep. These data indicate that pefloxacin and ciprofloxacin are highly active in vivo against various strains of S. aureus, and appear to be more potent than norfloxacin, vancomycin, cephalothin and methicillin.

Autoradiography of tissue distribution of the IIA constituent of the pristinamycins

The tissue distribution of a radioactive analogue of the IIA constituent of the pristinamycins was studied in female mice by autoradiography. Examination of slides and photographs discloses the presence of the antibiotic on the skin and in the bone marrow only a short time after injection. Elimination of the antibiotic is quick and is mainly through the digestive tract.

The in-vitro activity of pristinamycin against Haemophilus influenzae and Neisseria meningitidis

The in-vitro activity of erythromycin, oleandomycin, spiramycin, josamycin and pristinamycin was tested by a plate-dilution method against strains of Haemophilus influenzae and Neisseria meningitidis. Pristinamycin was the most active product tested with minimal inhibitory concentrations (MIC) ranging between 0.5 and 4 mg/l for H. influenzae (modal value 1 mg/l) and between 0.03 and 0.12 mg/l for N. meningitidis (modal value 0.06 mg/l).

[Water-soluble derivatives of factor IA of pristinamycins. Interaction with the bacterial ribosome]

The IA component of pristinamycins is a depsipeptide with a bacteriostatic effect on Gram positive bacteria. IA is made bactericidal by association with the IIA component of pristinamycins. Use of IA is limited because of its poor solubility in water. For this reason several water soluble IA derivatives have been synthesized. As for IA, these derivatives are fluorescent, a property used to study the binding of each compound to bacterial ribosomes of Escherichia coli (G-) and Staphylococcus aureus (G+). Two different techniques were used: direct study of fluorescence of the ribosome-antibiotic complex, and study of polarization of the fluorescence of the antibiotic bound to its receptor site. In addition to determination of binding parameters, these techniques can evaluate molecular synergy between pristinamycin IA (PIA) derivatives and pristinamycin IIA (PIIA) derivatives. MICs for the tested molecules correlate strongly with their binding parameters.

Pristinamycin accumulation by Staphylococcus aureus

Pristinamycins IA and IIA (PIA and PIIA) accumulation by Staphylococcus aureus has been studied with two hydrogenated analogs, (H2)PIA and (H2)PIIA. Rapid accumulation of both antibiotics at 37 degrees C is observed and internal concentrations can reach up to 58-fold the external concentration; this accumulation cannot be reduced by either metabolic inhibitors or tetracycline. The synergistic activity of pristinamycins IA and IIA is not observed at the bacterial accumulation level. We propose that pristinamycins enter into bacteria by a passive diffusion process and that the internal concentration is maintained by binding of the antibiotic to the bacterial ribosomes.

In vitro activity of pristinamycin against methicillin-resistant Staphylococcus aureus

An agar dilution technique was used to determine the MIC of pristinamycin for 124 clinical isolates of methicillin-resistant Staphylococcus aureus. All were inhibited by less than or equal to 0.5 mg/1, quite similar to the sensitivity of a number of methicillin-sensitive strains. MICs obtained using a microdilution method were also comparable. Antagonism was seen with the combination of pristinamycin and erythromycin.

Patricin A: A further model for cooperative effects of the Pro ring conformation and backbone

Although the main characteristics of the parent virginiamycin S conformation i.e. a bend of type VI (Lewis, P.N., Momamy, F.A. and Scheraga, H.A. (1973) Biochim. Biophys. Acta 303, 211--229) formed by the Pro-N-MePhe-X-PhGly sequence is still present in patricin A, the substitution of X = pipecolic acid by proline in the latter results in a destabilization of the tertiary structure of the depsipeptide, since two isomeric states of a peptidic bond appear in C2HC13 solution. Addition of +/- 30% (v:v) (C2H3)2SO totally shifts this equilibrium in favor of the major parent isomer. These results completely fit with what is known up to now on the occurrence and structure of turns (Chou and Fasman (1977) J. Mol. Biol. 115,135--175).

The conformation of allohydroxy- and deoxyvirginiamycin S

The experimental results of 1H- and 13C-NMR studies of allohydroxy-, and of deoxyvirginiamycin S strongly confirm the conformation that was proposed earlier for the parent virginiamycin S (Anteunis, Callens and Tavernier (1975) Eur. J. Biochem. 58, 259--268). The changing nature of dipole-induced dipole interaction is responsible for the specific gradually increasing libration of the N-MePhe side chain along the series virginiamycin S, allohydroxy-, deoxyvirginiamycin S. Previous methods for the estimation of rotameric populations around the alpha, beta bonds are critically evaluated and compared to the present results obtained from interpretation of geminal 2J (beta) coupling constants.

Staphylococcal micrococcins. III. Antibacterial and therapeutic properties

Micrococcin M, micrococcin M1 and eight micrococcin M derivatives, and two peptide antibiotics produced by micrococci and staphylococci were investigated for their antibacterial activity and therapeutic value. These antibiotics appeared to act solely on Gram-positive bacteria, especially on staphylococci and streptococci, in quite low concentrations in vitro and exerting both bacteriostatic and bactericidal effects. Gram-negative bacteria were virtually not susceptible. Resistance to micrococcins developed very rapidly, due to existence of numerous primarily resistant cells in sensitive populations. Complete cross-resistance resulted from acquiring resistance to one of the micrococcin antibiotics. Therapeutic effects are poor, as micrococcins are not absorbed from the injection site or from the intestinal tract after peroral administration. Importance of micrococcins in nature may be high, especially when ecology of normal bacterial flora and carriage of staphylococci and streptococci are concerned.