Molecular spectroscopic study on the interaction of tetracyclines with serum albumins

A molecular spectroscopic investigation of the interaction between tetracyclines antibiotics and human serum albumin or bovine serum albumin was reported. The influences of some metal ions on the interaction were also studied. When tetracyclines drugs were added into the solution containing serum albumins, the fluorescence intensity of serum albumins decreased with the increasing of the drugs concentrations, which is due to the formation of new non-fluorescence complexes of drug-serum albumin. The tetracyclines acted as quenchers and quenched the fluorescence of the serum albumins. The binding constants and the number of the binding sites of the reaction of tetracyclines and serum albumins were obtained. The main sorts of acting force between the drugs and serum albumins were found and the action distances and the energy transfer efficiencies between donor-acceptor were calculated based on the Foster energy transference.

The complex formed between Tet repressor and tetracycline-Mg2+ reveals mechanism of antibiotic resistance

In recent years Gram-negative bacteria have developed several resistance mechanisms against the broad-spectrum antibiotic tetracycline (Tc). The most abundant mechanism involves a membrane-associated protein (TetA) that exports the antibiotic out of the bacterial cell before it can attach to the ribosomes and inhibit polypeptide elongation. The expression of the TetA protein is regulated by the Tet repressor (TetR). It occurs as a homodimer and binds with two alpha-helix-turn-alpha-helix motifs (HTH) to two tandemly orientated DNA operators, thereby blocking the expression of the associated genes, one encoding for TetA and the other for TetR. If Tc in complex with a divalent cation binds to TetR, a conformational change occurs and the induced TetR is then unable to bind to DNA. TetR of class D, TEtRD, was cocrystallized with tetracycline (7HTc) and Mg2+ in space group I4(1)22 and studied by X-ray diffraction. One TetRD monomer occupies the crystal asymmetric unit, and the dimer is formed by a crystallographic 2-fold rotation. The crystal structure was determined by multiple isomorphous replacement at 2.5 A resolution, and on this basis the structure of the nearly isomorphous complex with 7-chlorotetracycline, TetRD/(Mg 7CITc)+, has been refined to an R-factor of 18.3% using all reflections to 2.1 A resolution. TetRD folds into ten alpha-helices with connecting turns and loops. The N-terminal three alpha-helices of the repressor form the DNA-binding domain, including the HTH with an inverse orientation compared with HTH in other DNA-binding proteins. The distance of 39 A between the two recognition helices explains the inability of the induced TetR to bind to B-form DNA. The core of the protein is formed by helices alpha 5 to alpha 10. It is responsible for dimerization and contains, for each monomer, a binding pocket that accommodates Tc in the presence of a divalent cation. The structure of the TetRD/(Mg 7CITc)+ complex reveals the octahedral coordination of Mg2+ by Tc (chelating O-11, and O-12), His100 N epsilon and by three water molecules; in addition there is an extended network of hydrogen bonding and van der Waals interactions formed between 7CITc and TetR. The detailed view of the Tc-binding pocket and the interactions between the antibiotic and the repressor offers the first solid basis for rational tetracycline design, with the aim of circumventing resistance.

Antibiotic-mediated changes in the fecal microbiome of broiler chickens define the incidence of antibiotic resistance genes

BACKGROUND

Antimicrobial agents have been widely used in animal farms to prevent and treat animal diseases and to promote growth. Antimicrobial agents may change the bacterial community and enhance the resistome in animal feces. We used metagenome-wide analysis to investigate the changes in bacterial community, variations in antibiotic resistance genes (ARGs), and their bacterial hosts in the feces of broiler chickens over a full-treatment course of chlortetracycline at low and therapeutic dose levels.

RESULTS

The effects of chlortetracycline on resistome were dependent on the specific ARG subtypes and not simply the overall community-level ARGs. Therapeutic dose of chlortetracycline promoted the abundance of tetracycline resistance genes (tetA and tetW) and inhibited multidrug resistance genes (mdtA, mdtC, mdtK, ompR, and TolC). The therapeutic dose of chlortetracycline led to loss of Proteobacteria mainly due to the decrease of Escherichia/Shigella (from 72 to 58%). Inhibition of Escherichia by chlortetracycline was the primary reason for the decrease of genes resistant to multiple drugs in the therapeutic dose group. The ARG host Bifidobacterium were enriched due to tetW harbored by Bifidobacterium under chlortetracycline treatment. Escherichia was always the major host for multidrug resistance genes, whereas the primary host was changed from Escherichia to Klebsiella for aminoglycoside resistance genes with the treatment of therapeutic dose of chlortetracycline.

CONCLUSIONS

We provided the first metagenomic insights into antibiotic-mediated alteration of ARG-harboring bacterial hosts at community-wide level in chicken feces. These results indicated that the changes in the structure of antibiotic-induced feces microbial communities accompany changes in the abundance of bacterial hosts carrying specific ARGs in the feces microbiota. These findings will help to optimize therapeutic schemes for the effective treatment of antibiotic resistant pathogens in poultry farms. Resistome variations in faecal microbiome of chickens exposed to chlortetracycline.

Sperm-oviduct interaction: induction of capacitation and preferential binding of uncapacitated spermatozoa to oviductal epithelial cells in porcine species

After mating, inseminated spermatozoa are transported to the oviduct. They attach to and interact with oviductal epithelial cells (OEC). To investigate sperm-OEC interactions, we used chlortetracycline to study the capacitation status of boar spermatozoa in coculture with homologous OEC and cells of nonreproductive origin (LLC-PK1, porcine kidney epithelial cell line). Boar spermatozoa were cocultured with OEC and LLC-PK1 cells for 15, 60, 120, or 240 min. The proportion of capacitated spermatozoa in coculture with the isthmic and ampullar cells increased significantly (p < 0.05) during incubation. However, most spermatozoa in coculture with LLC-PK1 cells or blank (medium only) remained uncapacitated. In addition, preferential binding of uncapacitated, capacitated, or acrosome-reacted boar spermatozoa to OEC and the other cell type was investigated. Our approach was to vary the proportions of uncapacitated, capacitated, or acrosome-reacted boar spermatozoa in suspension using long preincubation and lysophosphatidylcholine treatment of semen prior to a very short incubation with OEC or LLC-PK1 cells. The results showed that the majority of spermatozoa that were bound to OEC or LLC-PK1 cells were uncapacitated and that a significant relationship existed between the relative proportion of uncapacitated spermatozoa in the control samples and those bound to LLC-PK1 cells (r2 = 0.43, p < 0.005). However, there was no correlation between the proportion of uncapacitated spermatozoa in the control samples and the proportion of those bound to isthmic or ampullar cells. In conclusion, the results clearly demonstrated the specific nature of the sperm-OEC interaction in the porcine species. This interaction is initiated by uncapacitated spermatozoa binding to OEC and is continued by the induction of capacitation in cocultured spermatozoa.

Tetracycline compounds with non-antimicrobial organ protective properties: possible mechanisms of action

Tetracyclines were developed as a result of the screening of soil samples for antibiotics. The first(t) of these compounds, chlortetracycline, was introduced in 1947. Tetracyclines were found to be highly effective against various pathogens including rickettsiae, as well as both gram-positive and gram-negative bacteria, thus becoming the first class of broad-spectrum antibiotics. Many other interesting properties, unrelated to their antibiotic activity, have been identified for tetracyclines which have led to widely divergent experimental and clinical uses. For example, tetracyclines are also an effective anti-malarial drug. Minocycline, which can readily cross cell membranes, is known to be a potent anti-apoptotic agent. Another tetracycline, doxycycline is known to exert anti-protease activities. Doxycycline can inhibit matrix metalloproteinases which contribute to tissue destruction activities in diseases such as periodontitis. A large body of literature has provided additional evidence for the "beneficial" actions of tetracyclines, including their ability to act as reactive oxygen species scavengers and anti-inflammatory agents. This review provides a summary of tetracycline's multiple mechanisms of action as a means to understand their beneficial effects.

Capacitation status and in vitro fertility of boar spermatozoa: effects of seminal plasma, cumulus-oocyte-complexes-conditioned medium and hyaluronan

In the present study, the effects of seminal plasma (SP), cumulus-oocyte-complexes (COCs) conditioned medium (CCM) and hyaluronan (HA) on functional changes and in vitro fertilizing ability of porcine spermatozoa were examined. In in vitro fertilization (IVF) experiments, 10% (v/v) of exogenous SP in the fertilization medium prevented sperm penetration (using fresh-extended and frozen-thawed ejaculated spermatozoa). Analysis of frozen-thawed CCM revealed a HA content to levels of 30 ng/mL per incubated COC. Presence of frozen-thawed CCM did not, however, prove effective to increase (furthermore decreasing) oocyte penetration in vitro, and neither did supplementation with exogenous HA at the same concentration as that present in the CCM (secreted by COCs). Analysis of sperm capacitation using the chlortetracycline (CTC) assay showed that frozen-thawed CCM had no elevating effect on 'B-pattern' spermatozoa (implying capacitation-like changes) and that addition of 10% (v/v) SP held spermatozoa in the 'F-pattern' (intact) status. Dose of 500 microg/mL HA and freshly prepared CCM increased, however, the frequency of capacitated spermatozoa (B-pattern) without resulting in increased rates of 'AR-pattern' (acrosome-reacted) spermatozoa, compared with controls. The present results confirm the decapacitating effect of SP and suggest capacitating actions of HA (dose-related) and CCM (freshly prepared) on boar spermatozoa in vitro. The unclear effects of frozen-thawed CCM and a low dose of HA on penetration rates of boar spermatozoa call for further researches of their function in vivo.

Effect of seminal plasma on capacitation and hyperactivation in human spermatozoa

While hyperactivated motility is known to be a concomitant of capacitation, and a prerequisite for fertilization, the specific interdependence of capacitation and hyperactivation in human spermatozoa has not been investigated. This study was designed to determine the effect of seminal plasma contamination on the expression of hyperactivated motility and the relationship between hyperactivation and capacitation, since seminal plasma contains decapacitation factor(s). Seminal plasma was obtained by centrifugation of aliquots of liquefied semen layered over 1.5 ml 40.5% Percoll and mixed with human tubal fluid (HTF) medium containing 30 mg/ml human serum albumin (HSA) (HTF) to a final concentration of 5% (v/v) seminal plasma (SP). Motile spermatozoa were isolated from the remainder of the semen by swim-up into either HTF or SP medium. Samples were taken from each treatment immediately post-harvest (0 h) and after 60 min at 37 degrees C (1 h) for hyperactivation and capacitation assessment. The treatments were then divided into two portions, centrifuged and resuspended in either HTF or SP, giving HTF control and SP control treatments and two crossover treatments, 1 h HTF then 1 h SP (H/SP) and 1 h SP then 1 h HTF (SP/H). All tubes were incubated for a further 60 min at 37 degrees C before aliquots were taken for hyperactivation and capacitation assessments. Hyperactivation was estimated using an IVOS v10.6t (Hamilton Thorne Research, Beverly, MA, USA) 60 Hz CASA instrument, and capacitation was estimated using the chlortetracycline (CTC) method. The presence of seminal plasma in the capacitation medium for 60-120 min post-swim-up inhibited the development of hyperactivated motility. This inhibition was reversible, and was not prevented by preincubation for 1 h in HTF medium. There was no difference in the CTC binding patterns between treatments at 2 h, indicating that the capacitation-associated membrane changes were not affected by the presence of a low concentration of seminal plasma. There was no correlation between percentage capacitated and percentage hyperactivated spermatozoa for any treatment. Since the proportions of hyperactivated spermatozoa and capacitated spermatozoa were not related, we conclude that the processes leading to hyperactivation and to the membrane changes associated with capacitation are not tightly interlinked and consider this finding to be due to hyperactivated motility being associated with flagellar movement, while the CTC assay assesses changes in the Ca2+ levels of the sperm head plasma membrane.

Antimicrobial use and resistance in swine waste treatment systems

Chlortetracycline and the macrolide tylosin were identified as commonly used antimicrobials for growth promotion and prophylaxis in swine production. Resistance to these antimicrobials was measured throughout the waste treatment processes at five swine farms by culture-based and molecular methods. Conventional farm samples had the highest levels of resistance with both culture-based and molecular methods and had similar levels of resistance despite differences in antimicrobial usage. The levels of resistance in organic farm samples, where no antimicrobials were used, were very low by a culture-based method targeting fecal streptococci. However, when the same samples were analyzed with a molecular method detecting methylation of a specific nucleotide in the 23S rRNA that results in resistance to macrolides, lincosamides, and streptogramin B (MLSB), an unexpectedly high level of resistant rRNA (approximately 50%) was observed, suggesting that the fecal streptococci were not an appropriate target group to evaluate resistance in the overall microbial community and that background levels of MLSB resistance may be substantial. All of the feed samples tested, including those from the organic farm, contained tetracycline resistance genes. Generally, the same tetracycline resistance genes and frequency of detection were found in the manure and lagoon samples for each commercial farm. The levels of tetracycline and MLSB resistance remained high throughout the waste treatment systems, suggesting that the potential impact of land application of treated wastes and waste treatment by-products on environmental levels of resistance should be investigated further.

Profiling Protein Arginine Deiminase 4 (PAD4): a novel screen to identify PAD4 inhibitors

Protein Arginine Deiminase 4 (PAD4) has emerged as a leading target for the development of a Rheumatoid Arthritis (RA) pharmaceutical. Herein, we describe the development of a novel screen for PAD4 inhibitors that is based on a PAD4-targeted Activity-Based Protein Profiling reagent, denoted Rhodamine-conjugated F-Amidine (RFA). This screen was validated by screening 10 Disease Modifying Anti-Rheumatic Drugs (DMARDs) and identified streptomycin, minocycline, and chlortetracycline as micromolar inhibitors of PAD4 activity.

Correlation of bacteria lipid composition with antibiotic resistance

The correlation of bacterial lipid composition with antibiotic resistance was investigated with particular emphasis on those organisms in which resistance may be related to membrane or envelope structure or function, as in resistance to tetracyclines and polymyxin. Chloroform-methanol-extractable lipids, phosphatidyl ethanolamine fractions, and both fatty acids of these lipid fractions and total fatty acids were studied by using thin-layer chromatography, gas chromatography, and infrared spectroscopy. Consistent quantitative differences were found between the fatty acid compositions of sensitive and resistant strains. Most notable was the fact that, in gram-negative organisms, resistant strains showed decreases in cyclopropane acids as compared with sensitive strains. These changes were found to be inherent in the strains and not due to growth stage or culture age. No significant qualitative differences were noted. In contrast, no such variation in fatty acid content was observed in penicillin-sensitive and resistant strains of gram-positive cocci. As significant alterations of fatty acid composition were noted in gram-negative strains resistant to antibiotics, we suggest that resistance is correlated to membrane or envelope lipid composition.

Changes in soil microbial community structure and function associated with degradation and resistance of carbendazim and chlortetracycline during repeated treatments

The degradation characteristics of carbendazim (CBD) and chlortetracycline (CTC) in individual and combined treatments, and dynamics of soil microbial structural and functional diversity as well as their potential relations were studied during three repeated treatments using different concentrations. The results showed that the degradation half-life of CBD at concentrations of 3mg/kg and 6mg/kg obviously increased, but that of CTC at levels of 1mg/kg and 10mg/kg decreased with increasing treatment frequency. Soil microbial activity and functional diversity displayed the suppression trend in CBD treatment and the suppression-recovery-stimulation trend in CTC and CBD+CTC treatments, which were consistent with the findings of decreased degradation rate of CBD and increased degradation rate of CTC. 16S amplicon sequencing analysis revealed five potentially dominant CTC-resistant microbial genera including Bacillus, Actinobacillus, Pseudomonas, Mycobacterium, and Corynebacterium, which may mainly carry major facilitator superfamily transporter protein, ribosomal protection protein, and other proteins encoded by tetA, tetB, tetC, tetH, tetL, tetM, tetO, tetV, tetW, tetX, tetZ, tet33, and tet39. These five dominant genera may jointly contribute to the elevated bacterial community resistance to CTC. Our findings provided a better understanding of microbial community structure and function changes in repeatedly treated soils with CBD and CTC.

Effect of lactoferrin on the growth performance, intestinal morphology, and expression of PR-39 and protegrin-1 genes in weaned piglets

A total of 90 weaned female pigs (Duroc x Landrace x Yorkshire) were used in a 15-d growth experiment to investigate the effect of lactoferrin on growth performance, intestinal morphology, and expression of PR-39 and protegrin-1 genes. The pigs were allocated on the basis of BW and litter to 3 dietary treatments in a randomized complete block design. There were 3 replicate pens per treatment, and the pigs were grouped with 10 pigs per pen. The dietary treatments were (1) basal diet; (2) basal diet + 20 mg of flavomycin/kg + 110 mg of aureomycin/kg; (3) basal diet + 1.0 g of lactoferrin/kg. Six pigs, randomly selected from each treatment (2 piglets/pen) were slaughtered for intestinal morphology and expression of PR-39 and protegrin-1 genes at the end of the experiment. Supplementation with lactoferrin improved growth performance; it increased ADG by 41.80% (P < 0.01) and efficiency of gain (G:F) by 17.20% (P < 0.05). Intestinal villus height was increased by 15.30% (P < 0.05), and crypt depth was decreased by 9.60% (P < 0.05). Supplemental lactoferrin increased the relative abundance of mRNA for PR-39 and protegrin-1 by 143% (P < 0.01) and 217% (P < 0.01), respectively. The use of lactoferrin as an additive to improve nonspecific immunity and strengthen host defenses would be good a method of defending weaned pigs from infections and weanling stress.

Is intracellular Ca2+ the trigger for oxygen radical production by polymorphonuclear leucocytes?

The aim of this paper is critically to evaluate the existing evidence for the role of intracellular Ca2+ in polymorphonuclear leucocyte (PMN) activation and in particular in oxygen radical production. Indirect experiments are based on the manipulation of extracellular Ca2+, measurement of 45Ca fluxes, employing pharmacological agents such as Ca2+-ionophores and intracellular Ca2+ antagonists and monitoring chlortetracycline fluorescence. Experiments of this type do not provide the necessary definitive evidence that an increase in intracellular Ca2+ is the trigger for PMN activation. Recent direct measurements of intracellular free Ca2+ using the Ca2+-activated photoprotein, obelin, and the Ca2+-sensitive fluorescent indicator, quin 2, have provided evidence for the existence of two distinct mechanisms of activation, one triggered by a rise in intracellular Ca2+ and the other independent of a rise in intracellular Ca2+. The source of the Ca2+ for the former mechanism is mainly extracellular but can also come from an intracellular Ca2+ store.

In vitro susceptibility of antibiotics against Vibrio spp. and Aeromonas spp. isolated from Penaeus monodon hatcheries and ponds

Susceptibility patterns to 16 different antibiotics were investigated against pathogenic Vibrio spp. and Aeromonas spp. isolated from shrimp culture hatcheries and ponds in India. Thirteen species of Vibrio (N = 90) and two species of Aeromonas (N = 7) isolates were tested by agar disk diffusion. The results show that 100% of the isolates were resistant to ampicillin, and that 43.2% and 47.4% were sensitive to chlortetracycline and erythromycin, respectively. Susceptibility patterns of another 160 isolates belonging to the genera Vibrio and Aeromonas obtained from the water samples of shrimp hatcheries and ponds were tested against six commonly used antibiotics. Results indicate that isolates from the hatcheries were more resistant to antimicrobials than isolates from the ponds. The minimum inhibitory concentrations of five antibiotics against the different Vibrio spp. and Aeromonas spp. were determined. Ciprofloxacin was found to be the most effective in controlling the isolates from hatcheries and ponds compared with the other antibiotics used in the study. Our results reveal that antibiotic-resistant bacteria are widespread in the shrimp culture hatcheries and ponds in India. Potential risk to human health was not addressed in this study and remains to be elucidated.

TRANSDUCTION OF RESISTANCE TO CHLORTETRACYCLINE AND NOVOBIOCIN IN STAPHYLOCOCCUS AUREUS

Pattee , P. A. (Ohio State University, Columbus) and J. N. Baldwin . Transduction of resistance to chlortetracycline and novobiocin in Staphylococcus aureus . J. Bacteriol. 82: 875–881. 1961.—Using phage 80 of the International Typing Series propagated on appropriate strains of Staphylococcus aureus , resistance to chlortetracycline and novobiocin and the capacity to produce penicillinase were transduced to a number of antibiotic-sensitive recipient strains of S. aureus . The frequency of transduction varied from 1 to 10 transductants per 10 7 phage particles employed. Lysogenization of the transductants by the transducing phage did not occur. Phages 29, 52A, 79, and 53 of the International Typing Series were also capable of transduction, while phages 42B and 81 were unable to participate under the conditions used. The recipient strains were either resistant or susceptible to lysis by the transducing phages, but this did not influence the transduction frequencies. Lysis of transductants susceptible to the transducing phages was inhibited by preparing the selective medium with brain heart infusion agar. Linked transductions were not detected. With few exceptions, all of the recipient strains were susceptible to lysis by phages of group I or phage 81 or both. Strains susceptible to lysis by phages of groups II and III, but resistant to lysis by phages of group I or phage 81, were not transduced.