Effect Of Chlortetracycline Research Articles

Effects of Chlortetracycline on the Growth of Eggplant and Associated Rhizosphere Bacterial Communities

The widespread use of tetracycline antibiotics in the poultry and cattle sectors endangers both human health and the terrestrial ecosystem. Chlortetracyclines (CTCs), in particular, have been proven to affect soil microorganisms in addition to plants in the terrestrial ecosystem. In order to assess the effects of CTC on soil properties, eggplant growth, and soil microorganisms, a potted experiment was carried out in this study. CTC significantly reduced the levels of ammonium nitrogen (NH4+–N) and nitrite nitrogen (NO2−–N) in soil. Meanwhile, the eggplant’s growth was clearly hampered. CTC dramatically and dose-dependently lowered the fluorescence parameters except the quantum yield of non-regulated energy dissipation (ΦNO). Rhodoplanes and Cupriavidus, which were involved in N cycle, were enriched by 10 mg/kg CTC, according to results about different microorganisms at the genus level. Flavisolibacter was reduced by 10 and 50 mg/kg CTC, while Methylosinus and Actinocorallia were enriched by 250 mg/kg CTC. Redundancy analysis highlighted the profound impact of CTC on the soil microbial community, where strong correlations were observed with soil potential of hydrogen (pH), nitrate nitrogen (NO3−–N), and NO2−–N. These findings demonstrated the interdependence between the microbial community and soil characteristics, with CTC primarily affecting the microbes responsible for nitrogen cycling. Consequently, chlortetracycline poses potential hazards to both eggplant plants and the soil microbes in eggplant cultivation soil.

The effects of chlortetracycline on anaerobic digestion of chicken manure and the role of extracellular polymeric substances

In this study, the process stability and the protective role of extracellular polymeric substances (EPS) were evaluated during the anaerobic digestion (AD) of chicken manure (CM) suffering chlortetracycline (CTC) concentrations from 0 mg/L to 100 mg/L in a continuous stirred tank reactor (CSTR) operated for 270 days. Results showed that during the phases with low levels of CTC (0, 1.25, and 2.5 mg/L), the volume biogas production rate increased from 0.77 ± 0.01 L/(L·d) to 1.15 ± 0.02 L/(L·d) with an obvious decrease in the concentration of VFAs from 2.57 ± 0.07 g/L to 1.17 ± 0.08 g/L. The reactor remained stable with continued operation as the CTC in the CM spiked to 5 mg/L and 10 mg/L, respectively. During the phases with high levels of CTC (25, 50, and 100 mg/L), despite a reduction in biogas production of 18%, 43% and 56%, respectively, compared to the steady stage, the reactor finally could maintain the inhibition-steady stage. This stage was characterized by steady biogas production along with accumulating VFAs and ammonia nitrogen, which increased the inhibition thresholds of CTC on the AD of CM. An appreciable increase in EPS was identified. Spectral analysis results showed the fluorescence of protein-like in EPS was quenched with increasing dosages of CTC. The quenching constant (Kq) induced by CTC for tyrosine was found to be 3.969 × 1012 (R2 = 0.942), implying that the increased CTC prompt anaerobic microbes excrete more EPS to protect themselves from the CTC toxins by the formation of the complex tyrosine-CTC. This protection led to a decrease in the biodegraded CTC from 61.6 to 40.9%, and an increase in the adsorbed CTC on EPS in sludge from 35 to 56.1%. The results indicated that the absorbed CTC on EPS may pose a risk to the soil ecosystem due to the agriculture utilization of the biogas residue.

Effects of chlortetracycline on growth performance and intestinal functions in weaned piglets.

Weaning stress can cause serious damage to piglet's health. Chlortetracycline (CTC) is widely used to ameliorate weaning stress and prevent infectious diseases in weaned piglets. However, antibiotics as growth promoters have to be limited because of increased antimicrobial resistance. In this study, we evaluated the effects of CTC on growth performance and intestinal functions in order to provide evidence for seeking antibiotic substitutes in weaned piglets. A total of 20 weaned piglets were fed a basal diet or a diet supplemented with 75mg/kg CTC. CTC decreased the crypt depth and increased the ratio of villus height to crypt depth, whilst failing to affect growth performance and serum biochemical parameters and cytokines. 16S rRNA sequencing suggested that CTC supplementation had no effect on the diversity and composition of colonic microbiota. We speculated that gut microbiota is no longer sensitive to a low concentration of CTC due to the long-term use and low bioavailability of CTC in weaned piglets.

Effect of chlortetracycline on the growth and intracellular components of Spirulina platensis and its biodegradation pathway

Chlortetracycline (CTC) usually presents in livestock wastewater with oxytetracycline (OTC), causing damage to human health and ecosystems. It’s urgent to seek low-cost and ecofriendly technology for antibiotics removal. In this study, effects of CTC and CTC + OTC (CTC:OTC= 1:1, g/g) on Spirulina platensis have been investigated. EC50 value of CTC for S. platensis was 8.76 mg/L at 96 h and risk quotient value in wastewater was 15.85. Inhibition of CTC on S. platensis gradually enhanced with increase of CTC, but CTC + OTC below 1.0 mg/L didn’t harm the growth of microalgae. Chlorophyll-a (Chl-a) and carotenoid content showed a parabolic trend with extension of time at CTC group. Chl-a synthesis gradually decreased with increase of CTC + OTC stress. High concentrations of CTC and CTC + OTC showed obvious inhibition on phycocyanin production. Polyunsaturated fatty acids (PUFA) and saturated fatty acids (SFA) contents peaked at 1.0 mg/L CTC, corresponding to the minimum of superoxide dismutase (SOD) activity in S. platensis. SFA and PUFA contents decreased when CTC + OTC content was above 2.0 mg/L. CTC and CTC + OTC (both over 2.0 mg/L) stimulated production of dissolved extracellular organic matters in S. platensis. Removal efficiency of CTC by S. platensis was about 98.63–99.95% and its biodegradation pathways were hydroxylation and side-chain breakdown.

PSVIII-13 Evaluation of the effect of chlortetracycline on ruminal microbiome of ruminant against a background of plant extract

Abstract The limited use of antibiotics stimulates the search for alternatives or ways to reduce antibiotic resistance in order to prevent diseases and increase the productivity of ruminants. The aim of this study was to evaluate the effect of Quercus cortex (QC) extract (0.5 ml/kg body weight) together with chlortetracycline (Ch) (20%, 10 g/head/day) on cattle ruminal microbiome against the background of control (C), extract of QC and Ch. They were added separately as a substrate to the diets of bulls with rumen fistula (dairy breed, 12-months, diet - 80% hay, 20% grain feed, within 20 days). Microflora was analyzed using highly efficient sequencing of 16S rRNA gene (Illumina). QC was prepared by purification, grinding (1–2 mm), extraction in a water bath (30 min, 70 ° C). The taxonomic composition of ruminal microbiocenosis in control animals was represented by Bacteria and Fungi domains — 82.1 and 17.9%; QC - 99.8 and 0.2% was not classified; Ch - 10.4 and 89.6%; QC + Ch - 95.2 and 4.8%. Feeding with QC + Ch led to a decrease in phylums Bacteroidetes (P ≤ 0.05), Firmicutes (P ≤ 0.05), Proteobacteria compared to C. An increase in bacteria of Bacteroidia class (by 42.9% (P ≤ 0.05)) due to the species Prevotella and a decrease in the class of Gammaproteobacteria (by 6.9%) were registered. The species composition was characterized by a decrease in bacteria of Lactobacillus, Faecalibacterium, Escherichia, Fibrobacter genera. Ch group characterized by a decrease Fungi Ascomycota (P ≤ 0.05) and an increase in Chytridiomycota (P ≤ 0.05) and were not identified in QC and QC + Ch. Thus, this study highlights the potential use of plant extracts as an additional feed supplement, which can reduce the negative effects of chlortetracycline on the development of gram-positive bacteria and Fungi. This research was performed with financial support from the RSF (16-16-10048).

Influence of chlortetracycline as an antibiotic residue on nitrous oxide emissions from wastewater treatment

Strengthening the removal of antibiotics in wastewater treatment plants is a research focus, but whether antibiotics affect nitrous oxide (N2O) emissions from wastewater treatment remains to be determined. In this study, the effect of chlortetracycline (CTC) on N2O emissions in anaerobic/oxic/anoxic sequential batch reactors was investigated. Experimental results show that CTC promotes N2O emissions during biological nutrient removal. The addition of 0.1 mg/L CTC increased the N2O emission factor by 41.4% compared to the control. Mechanism exploration shows that CTC stimulates the release of extracellular polymeric substance (EPS) and binds to it, the generated EPS-CTC conjugates hinder or expand the mass transfer channel, which intensifies the electronic competition between oxidoreductases and the substrate competition between microorganisms, resulting in incomplete denitrification and nitrite accumulation, thereby increasing N2O emissions.

Chlortetracycline inhibits seed germination and seedling growth in Brassica campestris by disrupting H2O2 signaling

Antibiotics have been identified as a new type of environmental contaminant because of their increased use in farm animal production systems. Those drugs that animals are not absorbed mostly are excreted in the feces and urine and contaminates soils. However, the effects of antibiotics on crop plants are still largely unknown. In this study, we determined the effects of chlortetracycline (CTC), a veterinary drug released into the agricultural field by grazing animals or through manure application, on the growth and physiology of Brassica campestris seedlings. Differently from animals, Brassica campestris seedlings have accumulated 5–10-fold higher CTC during cultivation rather than excretion. Morphologically, CTC delays seed germination and inhibits seedling growth such as shortening primary root length and decreasing chlorophyll level. At the molecular level, CTC accumulation in plants downregulated the expression of superoxide dismutase (SOD) genes and decreased the production of hydrogen peroxide (H2O2). Since H2O2 is one of the signaling components involved in the regulation of root growth, exogenous application of H2O2 partially restored the growth and physiology of CTC-treated seedlings. These results suggest that application of CTC-containing manure or compost to soil delays seed germination and inhibits plant growth.

Effects of chlortetracycline alone or in combination with direct fed microbials on nursery pig growth performance and antimicrobial resistance of fecal Escherichia coli.

A total of 300 nursery pigs (initially 5.9 ± 0.05 kg BW) were used in a 42-d growth trial to evaluate the effects of feeding a therapeutic level of chlortetracycline (CTC) with or without direct fed microbials (DFM) on growth performance and antimicrobial resistance (AMR) of fecal Escherichia coli. CTC is a broad-spectrum in-feed antibiotic commonly used in the swine industry. Weaned pigs (~21 d of age) were allotted to pens based on initial BW and fed a common starter diet for 4 d. Pens were then blocked by BW and allotted to dietary treatments in a completely randomized block design. Dietary treatments were arranged in a 2 × 3 factorial consisting of combinations of CTC (none vs. 400 mg/kg from days 0 to 42) and DFM (0 vs. 0.05% DFM 1 vs. 0.05% DFM 2). Fecal samples were collected from three randomly selected pigs from each pen on days 0, 21, and 42 for E. coli isolation and AMR determination. Overall, pigs fed diets containing CTC had improved (P < 0.001) ADG, ADFI, and BW compared to those not fed CTC with no evidence for any effect of either DFM 1 or DFM 2. Regardless of CTC, inclusion of DFM 2 in diets improved (P < 0.05) ADFI from days 0 to 14 and on day 14 BW compared to diets that did not include DFM 2. The addition of CTC with or without DFMs to nursery pig diets increased (P < 0.05) the probability of AMR to tetracycline and ceftiofur of fecal E. coli isolates, but this resistance generally decreased (P < 0.05) over time. A decrease (P < 0.05) in AMR to ampicillin and tetracycline (TET) throughout the trial was observed, while resistance to ceftriaxone decreased (P < 0.020) from days 0 to 21 and increased from days 21 to 42 amongst dietary treatments regardless of CTC or DFM inclusion in the diet. A CTC × DFM × day interaction (P < 0.015) was observed for streptomycin, whereby from days 21 to 42 AMR increased in diets containing either CTC or DFM 1 alone, but the combination decreased resistance. There was no evidence for any effect of DFMs on AMR of fecal E. coli isolates to any other antibiotics evaluated. In conclusion, therapeutic levels of added CTC with or without DFM inclusion improved nursery pig performance, but increased AMR of fecal E. coli isolates to TET and ceftiofur. A moderate improvement in intake and day 14 BW was observed when DFM 2 was included in the diet with or without CTC, but, except for streptomycin, there was no evidence that added dietary DFMs affected resistance of fecal E. coli to antibiotics.

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

BackgroundAntimicrobial 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.ResultsThe 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.ConclusionsWe 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.Graphical abstractResistome variations in faecal microbiome of chickens exposed to chlortetracycline

Effects of chlortetracycline on the fate of multi-antibiotic resistance genes and the microbial community during swine manure composting.

Excessive use of antibiotics in breeding industry leads to accumulation of antibiotic residuals and antibiotic resistance genes (ARGs) in environment from improperly treated livestock excrements. Four commonly used veterinary antibiotics including chlortetracycline (CTC), sulfamerazine (SMZ), enrofloxacin (ENR) and erythromycin (ERY) were monitored in the swine manure composting. Co-resistance and cross-resistance effects among relative ARGs, correlations between ARGs and bacterial community under multiple antibiotics residual during the composting were investigated in this research. With CTC addition up to 20mg/kg, more than 99% of CTC removal was achieved after composting, and most of the other antibiotics can be thoroughly removed as well. The variations in ARGs during the composting were strongly correlated to the compositions of the microbial community, Bacteroides and Sporosarcina were main ARGs carriers in the thermophlic phase. Clostridium Ⅺ, Clostridium sensu stricto, and Pseudoxanthomonas, might spread ARGs in cooling and maturing stage. Most of the tested ARGs in swine manure can be effectively reduced through composting, thus makes the compost products safe for soil fertilization.

Antibiotic degradation and microbial community structures during acidification and methanogenesis of swine manure containing chlortetracycline or oxytetracycline

Anaerobic digestion (AD) has been applied to animal manure stabilization, and antibiotics is frequently found in animal manure. However, antibiotic degradation and microbial community structures during two-stage AD (acidification and methanogenesis) remain poorly understood. This experiments on two-stage anaerobic swine manure digesters were performed to investigate the degradation mechanisms and effects of chlortetracycline (CTC) and oxytetracycline (OTC) on microbial community structures. Results showed that acidification and methanogenesis showed good degradation performance for manure containing CTC and OTC at 60 and 40 mg/kg·TS, respectively. CTC and OTC were degraded by 59.8% and 41.3% in the acidogenic stage and by 76.3% and 78.3% in the methanogenic stage, respectively. CTC and OTC negatively affected bacterial community in methanogenic and acidogenic stages, respectively. They also adversely influenced the archaeal species in the methanogenic stage. Two-stage AD was proposed to treat manure containing antibiotics and to reduce the negative effects of antibiotics on AD.

Impact of chlortetracycline and sulfapyridine antibiotics on soil enzyme activities

Abstract Pharmaceutical antibiotics are frequently used in the livestock and poultry industries to control infectious diseases. Due to the lack of proper guidance for use, the majority of administrated antibiotics and their metabolites are excreted to the soil environment through urine and feces. In the present study, we used chlortetracycline and sulfapyridine antibiotics to screen out their effects on dehydrogenase, alkaline phosphatase and urease activity. Factorial experiments were conducted with different concentrations of antibiotic (0, 10, 25 and 100 mg kg−1 of soil) mixed with soil samples, and the enzyme activity was measured at intervals of 1, 4 and 21 days. The results show that the chlortetracycline and sulfapyridine antibiotics negatively affect the dehydrogenase activity, but the effect of sulfapyridine decreases with time of incubation. Indeed, sulfapyridine antibiotic significantly affect the alkaline phosphatase activity for the entire three-time interval, while chlortetracycline seems to inhibit its activity within 1 and 4 days of incubation. The effects of chlortetracycline and sulfapyridine antibiotics on urease activity appear similar, as they both significantly affect the urease activity on day 1 of incubation. The present study concludes that chlortetracycline and sulfapyridine antibiotics have harmful effects on soil microbes, with the extent of effects varying with the duration of incubation and the type of antibiotics used.

Effects of chlortetracycline, Cu and their combination on the performance and microbial community dynamics in swine manure anaerobic digestion

Swine manure was typical for the combined pollution of heavy metals and antibiotics. The effects of widely used veterinary antibiotic chlortetracycline (CTC), Cu and their combination on swine manure anaerobic digestion performance and microbial community have never been investigated. Thus, four 2L anaerobic digestion reactors were established including reactor A (control), B (CTC spiked by 0.5g/kg dry weight, dw), C (Cu spiked by 5g/kg dw) and D (combination of CTC, 0.5g/kg dw, and Cu, 5g/kg dw), and dynamics of bacterial and archaeal community structure was investigated using high throughput sequencing method. Results showed that addition of CTC and Cu separately could increase the total biogas production by 21.6% and 15.8%, respectively, while combination of CTC and Cu severely inhibited anaerobic digestion (by 30.3%). Furthermore, corresponding to different stages and reactors, four kinds of microbes including bacteria and archaea were described in detail, and the effects of CTC, Cu and their combination mainly occurred at hydrolysis and acidification phases. The addition of Cu alone changed the dynamics of archaeal community significantly. It was genus Methanomassiliicoccus that dominated at the active methane production for A, B and D, while it was genus Methanobrevibacter and Methanoculleus for C.

Effects of chlortetracycline and copper on tetracyclines and copper resistance genes and microbial community during swine manure anaerobic digestion

As antibiotic and heavy metals are over used in the livestock industry, animal manure is a reservoir of antibiotic resistance genes (ARGs). Anaerobic digestion has been reported to have the potential to reduce ARGs. However, few studies investigated whether reduction of ARGs would be affected by different external pressures including antibiotics and heavy metals during anaerobic digestion. The purpose of this study was thus to investigate effects of both chlortetracycline (CTC) and Cu on reduction of ARGs, heavy metal resistance genes (HMRGs) and mobile genetic elements (MGEs) during the swine manure anaerobic digestion. The results showed that the predominant ARGs (tetO, tetW, tetX, tetL) could be effectively reduced (approximately 1.00 log copies/g TS) through mesophilic anaerobic digestion. Microbial community evolution was the main driver. It was interesting that Treponema might indicate the termination of anaerobic digestion and compete with ARGs host bacteria. Addition of CTC, Cu and CTC+Cu affected microbial community change and hindered removal of ARGs, especially, CTC+Cu seriously affected Treponema and ARGs during anaerobic digestion.

Performance evaluation and microbial community of a sequencing batch biofilm reactor (SBBR) treating mariculture wastewater at different chlortetracycline concentrations

The effects of chlortetracycline (CTC) on the performance, microbial activity, extracellular polymeric substances (EPS) and microbial community of a sequencing batch biofilm reactor (SBBR) were investigated in treating mariculture wastewater. Low CTC concentration (less than 6 mg/L) had no obvious effect on the SBBR performance, whereas high CTC concentration could inhibit the chemical oxygen demand (COD) and nitrogen removal of the SBBR. The microbial activity of the biofilm in the SBBR decreased with the increase of CTC concentration from 0 to 35 mg/L. The protein (PN) contents were always higher than the PS contents in both loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS) at different CTC concentrations. The chemical compositions of LB-EPS and TB-EPS had obvious variations with the increase of CTC concentration from 0 to 35 mg/L. The high-throughput sequencing revealed the effects of CTC on the microbial communities of the biofilm at phylum, class and genus level. The relative abundances of some genera displayed a decreasing tendency with the increase of CTC concentration from 0 to 35 mg/L, such as Nitrospira, Paracoccus, Hyphomicrobium, Azospirillum. However, the relative abundances of the genera Flavobacterium, Aequorivita, Buchnera, Azonexus and Thioalbus increased with the increase of CTC concentration.

Extensive Literature Search on the ‘Effects of Copper intake levels in the gut microbiota profile of target animals, in particular piglets’

Extensive Literature Search on the ‘Effects of Copper intake levels in the gut microbiota profile of target animals, in particular piglets’

Protein Specter of Carp’s Blood Plasma under Impact of Chlortetracycline

The paper deals with effects of chlortetracycline on the fractional composition of carp plasma proteins. Chlortetracycline of concentration 1.1 mg/l had no effect, and 3.15 and 6.30 mg/l reduced content of proteins with molecular mass of 340–450 kDa and more, and promoted appearance of additional protein with molecular mass 140–200 and 70–90 kDa.

Effects of chlortetracycline and copper supplementation on the prevalence, distribution, and quantity of antimicrobial resistance genes in the fecal metagenome of weaned pigs

Use of in-feed antibiotics such as chlortetracycline (CTC) in food animals is fiercely debated as a cause of antimicrobial resistance in human pathogens; as a result, alternatives to antibiotics such as heavy metals have been proposed. We used a total community DNA approach to experimentally investigate the effects of CTC and copper supplementation on the presence and quantity of antimicrobial resistance elements in the gut microbial ecology of pigs. Total community DNA was extracted from 569 fecal samples collected weekly over a 6-week period from groups of 5 pigs housed in 32 pens that were randomized to receive either control, CTC, copper, or copper plus CTC regimens. Qualitative and quantitative PCR were used to detect the presence of 14 tetracycline resistance (tet) genes and to quantify gene copies of tetA, tetB, blaCMY-2 (a 3rd generation cephalosporin resistance gene), and pcoD (a copper resistance gene), respectively. The detection of tetA and tetB decreased over the subsequent sampling periods, whereas the prevalence of tetC and tetP increased. CTC and copper plus CTC supplementation increased both the prevalence and gene copy numbers of tetA, while decreasing both the prevalence and gene copies of tetB. In summary, tet gene presence was initially very diverse in the gut bacterial community of weaned pigs; thereafter, copper and CTC supplementation differentially impacted the prevalence and quantity of the various tetracycline, ceftiofur and copper resistance genes resulting in a less diverse gene population.

Effects of chlortetracycline on soil microbial communities: Comparisons of enzyme activities to the functional diversity via Biolog EcoPlates™

Veterinary antibiotics (VAs) can enter agricultural soil by the application of animal excrements. However, the response of soil microorganisms to VAs is not well understood. Therefore, a 45-day microcosm experiment was conducted to ascertain the impact of chlortetracycline (CTC) on soil microbial communities. In this study, CTC was applied to soil samples with no previous antibiotic-containing manure application history at three concentrations of 1, 10, and 100 mg/kg soil. Soil samples were taken after 1, 6, 12 and 45 day(s) of incubation to determine the dissipation of CTC using HPLC. Meanwhile, to investigate the effect of CTC on microorganisms, microbial activities in the cultivable and the actual community were determined using Biolog EcoPlates™ and enzyme activities, respectively. It was demonstrated that CTC dissipated faster at lower spiking levels. At the end of the experiment, no CTC could be extracted in all treatments, except for C100. The enzyme activities were enhanced on the first day and then were significantly inhibited by CTC for up to 45 days. This inhibition was especially true for activities of dehydrogenase and urease, whereas phosphatase activities were slightly affected. The results demonstrated that CTC contamination could pose a selective pressure on soil microorganisms, despite its rapid decline in the extractable concentration. However, community-level physiological profiles (CLPP) that were assessed using Biolog EcoPlates™ displayed different susceptibilities to the addition of CTC: it responded rapidly to CTC-amendment and were improved strongly by CTC on the first day, whereas no effect was detected thereafter. It was suggested that the Biolog EcoPlates method was more suitable for short-term toxicity tests than for the relatively long-term effects of pollutants on microbial communities.

Effects of chlortetracycline and copper supplementation on antimicrobial resistance of fecal Escherichia coli from weaned pigs

Feed-grade chlortetracycline (CTC) and copper are both widely utilized in U.S. pig production. Cluster randomized experiment was conducted to evaluate the effects of CTC and copper supplementation in weaned pigs on antimicrobial resistance (AMR) among fecal Escherichia coli. Four treatment groups: control, copper, CTC, or copper plus CTC were randomly allocated to 32 pens with five pigs per pen. Fecal samples were collected weekly from three pigs per pen for six weeks. Two E. coli isolates per fecal sample were tested for phenotypic and genotypic resistance against antibiotics and copper. Data were analyzed with multilevel mixed effects logistic regression, multivariate probit analysis and discrete time survival analysis. CTC-supplementation was significantly (99% [95% CI=98–100%]) associated with increased tetracycline resistance compared to the control group (95% [95% CI=94–97%]). Copper supplementation was associated with decreased resistance to most of the antibiotics tested, including cephalosporins, over the treatment period. Overall, 91% of the E. coli isolates were multidrug resistant (MDR) (resistant to ≥3 antimicrobial classes). tetA and blaCMY-2 genes were positively associated (P<0.05) with MDR categorization, while tetB and pcoD were negatively associated with MDR. tetA and blaCMY-2 were positively associated with each other and in turn, these were negatively associated with both tetB and pcoD genes; which were also positively associated with one another. Copper minimum inhibitory concentration was not affected by copper supplementation or by pcoD gene carriage. CTC supplementation was significantly associated with increased susceptibilities of E. coli to copper (HR=7 [95% CI=2.5–19.5]) during treatment period. In conclusion, E. coli isolates from the nursery pigs exhibited high levels of antibiotic resistance, with diverse multi-resistant phenotypic profiles. The roles of copper supplementation in pig production, and pco-mediated copper resistance among E. coli in particular, need to be further explored since a strong negative association of pco with both tetA and blaCMY-2 points to opportunities for selecting a more innocuous resistance profile.