Chlortetracycline Residues Research Articles

Monitoring of Tetracycline Group Antibiotic Residues in Various Food Products of Animal Origin in the Turkish Market

The aim of this study was to detect the presence of antibiotic residues in foods of animal origin, including 42 pieces of chicken gizzard and 46 pieces of bovine kidney and 102 chicken eggs belonging to various brands. These samples were gathered from December 2020 to April 2021 in the Aegean province of Turkey. A sensitive, simple, rapid, experimentally convenient and cost effective RP-LC method with high recovery output was developed. The method was thoroughly validated for the optimized parameters and produced satisfactory results. The analysis of bovine offal by the developed RP-LC method showed the presence of oxytetracycline, tetracycline, and chlortetracycline residues in 14 (30.43%) kidney samples. Chlortetracycline was detected in 7 (16.67%) chicken gizzard samples. In addition, the analysis of chicken eggs revealed the presence of oxytetracycline and tetracycline residues in nine egg samples (8.82%). Since, the amount of antibiotic residues in these samples was below the detection limit, quantification could not be carried out. Only one (0.98%) of the 102 egg samples exceeded the MRL (267.1 mg/kg) for oxytetracycline concentration. According to the study's overall findings, it is recommended that tetracycline antibiotics should be regularly checked in a variety of foods made from animals because they were found in 32 out of 190 analysed samples. Tetracycline residues may pose dangers to human health, so it's important to conduct further research and more information should be given for both producers and consumers.

Mitigation effects and microbial mechanism of two ecological earthworms on the uptake of chlortetracycline and antibiotic resistance genes in lettuce

The contamination of greenhouse vegetable soils with antibiotics and antibiotic resistance genes (ARGs), caused by the application of livestock and poultry manure, is a prominent environmental problem. In this study, the effects of two ecological earthworms (endogeic Metaphire guillelmi and epigeic Eisenia fetida) on the accumulation and transfer of chlortetracycline (CTC) and ARGs in a soil–lettuce system were studied via pot experiments. The results revealed that earthworm application accelerated the removal of the CTC from the soil and lettuce roots and leaves, with the CTC content reducing by 11.7–22.8 %, 15.7–36.1 %, and 8.93–19.6 % compared with that of the control, respectively. Both earthworms significantly reduced the CTC uptake by lettuce roots from the soil (P < 0.05) but did not change the CTC transfer efficiency from the roots to leaves. The high-throughput quantitative PCR results showed that the relative abundance of ARGs in the soil and lettuce roots and leaves decreased by 22.4–27.0 %, 25.1–44.1 %, and 24.4–25.4 %, respectively, with the application of earthworms. Earthworm addition decreased the interspecific bacterial interactions and the relative abundance of mobile genetic elements (MGEs), which helped reduce the dissemination of ARGs. Furthermore, some indigenous soil antibiotic degraders (Pseudomonas, Flavobacterium, Sphingobium, and Microbacterium) were stimulated by the earthworms. The results of redundancy analysis indicated that the bacterial community composition, CTC residues, and MGEs were the main parameters affecting the distribution of ARGs, accounting for 91.1 % of the total distribution. In addition, the bacterial function prediction results showed that the addition of earthworms reduced the abundance of some pathogenic bacteria in the system. Overall, our findings imply that earthworm application can substantially reduce the accumulation and transmission risk of antibiotics and ARGs in soil–lettuce systems, providing a cost-effective soil bioremediation practice for addressing antibiotic and ARGs contamination to guarantee the safety of vegetables and human health.

Assessment of Tetracyclines Residues Contamination in Chicken Meat Samples of Algiers Slaughterhouses Level

Food contamination with antimicrobial residues may occur, entailing assessment and monitoring of the contamination level in edible tissue. In that way, 151 chicken meat samples were randomly collected from Algiers slaughterhouses. Otherwise, two analytical methods are validated for the simultaneous determination of oxytetracycline, tetracycline, doxycycline and chlortetracycline residues in edible chicken tissues, by liquid chromatography combined with mass spectrometry detection. Beforehand, an extraction step is performed. Indeed, acetonitrile is used as an extraction solvent for the qualitative method, and then the quantitative method is carried out after a preliminary extraction with an acidified EDTA-McIlvaine buffer, followed by a solid-phase extraction cleanup. Validation qualitative method results were satisfactory in terms of specificity (100%), sensivity, detection capability (CCß) and detection limit (LOD). Furthermore, validation results of the quantitative method was pertinent to the EU commission criteria. Thus, determination coefficient (r2) values were between de 0.91 to 0.98%, where the lowest values were observed for doxycycline. Trueness was between 85.5% and 104.8, expect for tetracycline (76.6% at 150µg/kg) and doxycycline (134.7% at 100µg/kg). As for intraday and interday precision, values respectively ranged between 12.5 and 26% and between 14 and 35%, except doxycycline for which precision values were higher. The methods have been successfully used for the identification, confirmation and quantification of tetracyclines in chicken muscle samples. Consequently, 25 samples were suspects in regard tetracyclines residues. The comparison of these samples with the QC at MRL (100µg/kg) revealed five samples needed a quantification. Thus, oxytetracycline, its epimer and doxycycline identified in samples were quantified. Indeed, all samples contained oxytetracycline and its epimer, doxycycline or both showed levels less than the decision limit (CCα).

Construction of ratiometric fluorescence sensor and test strip with smartphone based on dual-emission carbon dots for the specific detection of chlortetracycline.

Concerns about environmental and food contamination caused by chlortetracycline (CTC) residues have prompted people to explore efficient and convenient CTC monitoring platforms. However, the reported fluorescent probes generally fail to selectively detect CTC due to the structural similarity of tetracycline antibiotics. Herein, an intrinsic dual-emission carbon dots (D-CDs) ratiometric fluorescence sensor was prepared for highly sensitive and selective determination of CTC over other tetracyclines by one-step synthesis. The sensor exhibited a significant fluorescence enhancement at 425 nm after introducing CTC. The fluorescence "turn on" of the sensing system is due to aggregation-induced emission (AIE) phenomenon formed by hydrogen bonds and π conjugation promoting the specific recognition of CTC by D-CDs. The linear detection varied from 0.98 to 143.67 ng mL-1 with a low limit of detection (LOD) of 1.29 ng mL-1 (R2 = 0.998), which was lower than most reported in the literature. The D-CDs sensor was applied to detect CTC in spiked milk, blocked normal human serum, and fish samples with recoveries of 95.5-104.2% and relative standard deviations (RSDs) of 2.6%. Particularly, D-CDs based test papers with a smartphone were prepared for portable and visual detection of CTC by analyzing the various color changes of RGB of fluorescence color, with an LOD of 7.18 ng mL-1 (R2 = 0.9909). The fluorescence sensor designed in this work could be used as a rapid tool with high performance and selectivity for monitoring control in foods.

Investigation of tetracycline residues in poultry meat samples from Dhaka city by high-performance liquid chromatography

The objective of the study was to quantify tetracycline (TCs) i.e., oxytetracycline (OTC), tetracycline (TC) and chlortetracycline (CTC) residues in thirty poultry meat samples (n = 30) collected from the local market and super shop around the Dhaka University campus during May 2019 to January 2020. Three samples were collected from each of ten locations. All samples were extracted by Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method. Samples were analyzed by reversed-phase High-Performance Liquid Chromatograph equipped with Photo Diode Array Detector (LC-PDA) and a reported method was validated with good linear correlation coefficients of standards and matrix-matched calibration curves with r2=1.00, 0.99, 0.99 and r2= 0.99, 0.99,0.99 in the linearity range of 0-10 µg/kg for OTC, TC and CTC, respectively. The limit of detection (LOD) and limit of quantification (LOQ) for OTC, TC, and CTC were 1.05, 1.17, and 1.09 μg/kg and 3.15, 3.51 and 3.27 μg/kg, respectively. Accuracy that is expressed by the recovery percentages were calculated at two different concentrations (2.5 and 5 μg/kg) were 91 and 100%, 102 and 100%, and 106 and 100% for OTC, TC, and CTC, respectively. Intra-day (n=3) and inter-day (n=9, 3 days) precision data were under 10% for all sample matrixes. Standard deviations were calculated ±0.06, ±0.11 and ±0.03 and precision (expressed by RSD%) were found 5.57, 9.14 and 2.35%, respectively for OTC, TC and CTC. The HPLC-PDA method is affordable for screening of large number meat samples for residual antibiotics in biological matrices by any laboratories. The method is also cheaper in comparison with LC-MSMS. Analysis of real 30 poultry meat samples showed that the tetracyclines residues were below the quantification limit in all samples.

Chlortetracycline alters microbiota of gut or faeces in pigs and leads to accumulation and migration of antibiotic resistance genes

In this study, we investigated the effect of long-term use of chlortetracycline (CTC) on the gut microbiota composition and metabolism profiles in pigs, and the variation of antibiotic resistance genes (ARGs) and microbial communities in faeces and manure during aerobic composting (AC) and anaerobic digestion (AD). The pigs were fed the same basal diet supplemented with or without 75 mg/kg CTC, and fresh faeces of 30-, 60-, 90-, and 120-day-old pigs were collected from the CTC group. The results showed that CTC reduced the diversity of the gut microbiota significantly and changed its structure. Metabolomics analysis of intestinal contents revealed 23 differentially abundant metabolites, mainly organic acids, carbohydrates, and amino acids. Metabolic pathways, such as the TCA cycle, propionate metabolism, and pyruvate metabolism, were changed. From 30 to 120 days of age, the amount of CTC residues in faeces and the abundance of 3 tetracycline resistance genes increased significantly, and it was positively correlated with tetC, tetG, tetW, sul1 and intI2. CTC residue levels and ARGs abundance gradually decreased with fermentation time, and AC was better than AD at reducing ARGs abundance. The results suggest that in-feed CTC can reduce the diversity of the gut microbiota, change the structure, function and metabolism of the bacterial community, and increase the abundance of ARGs in faeces.

Determination of tetracycline, oxytetracycline and chlortetracycline residues in seafood products of Saudi Arabia using high performance liquid chromatography–Photo diode array detection

Residues of oxytetracycline, tetracycline and chlortetracycline in seafood products of Saudi Arabia were detected by using a simple, sensitive and rapid method via HPLC-PDA.The protein precipitation method that was used for sample extraction demonstrated high recoveries of OTC, TC and CTC. The limits of detection were 0.015 µg/g and 0.025,0.062 µg/g for all TCs in fish and shellfish, respectively. The limits of quantitation were 0.125 µg/g and 0.175 µg/g for all TCs in fish and shellfish, respectively. The method was precise and accurate since the RSD was less than 2%, while the % recovery was 95–105%. This study determined the occurrence of OTC, TC and CTC in seafood products that are sold in KSA’s markets. The overall occurrence of these three medications in 249 seafood products was 24%(n = 60), while 15%(n = 37) exceeded the MRL. Thus, our recommendations are to enhance the monitoring of food production prior to marketing and to educate people regarding the proper disposal of antibiotics.

Tetracycline Residues in Bovine Muscle and Liver Samples from Sicily (Southern Italy) by LC-MS/MS Method: A Six-Year Study.

We examined a total of 369 bovine liver and muscle samples for the detection of oxytetracycline (OTC), tetracycline (TC), chlortetracycline (CTC), and doxycycline (DOX) residues by implementation and validation of a LC-MS/MS method. The method showed good recovery values between 86% and 92% at three levels of concentrations. The linearity tests revealed r2 > 0.996 for all the tetracyclines examined. Furthermore, the Youden test revealed that the method was robust. Only 14.4% of the samples showed OTC and TC residues in a concentration range of 10.4–40.2 µg kg−1. No CTC and DOX residues were found in all the samples analyzed. Liver samples showed the highest average values (31.5 ± 20.6 and 21.8 ± 18.9 for OTC and TC, respectively). The results showed a low incidence of TCs in all the samples examined, in comparison with other studies reported in the literature. A significant decrease in TC residues frequency was found from 2013 (p < 0.05). This work reports for the first time epidemiological data on the presence of TC residues in liver and muscle samples of cattle farmed in Sicily (Southern Italy). The very low incidence of TC residues indicates a continuous improvement in farming techniques in Southern Italy, which is essential to ensure consumers’ protection.

Macleaya cordata helps improve the growth-promoting effect of chlortetracycline on broiler chickens.

Chlortetracycline (CTC), one kind of common antibiotic for prevention and treatment of various diseases, also exhibits good performance in accelerating the growth of livestock. Macleaya cordata, a traditional Chinese medicine, is usually used as a natural additive in livestock because of its anti-microbial, anti-fungal, anti-inflammatory, and pesticidal activity. In this work, we studied whether M. cordata helps regulate the growth-promoting effect of CTC on broiler chickens. It is demonstrated that M. cordata improves the growth-promoting effect of CTC on growth performance indices of broiler chickens, such as survival rate, daily weight, and feed to weight rate. M. cordata also delays the maximum of CTC residues in plasma. It may depend on the higher values of operational taxonomic unit (OTU) and the indices of α diversity driven by simultaneous use of CTC and M. cordata.

Rapid Detection on Chlortetracycline Residues in Honey by Surface-enhanced Raman Spectroscopy†

Rapid Detection on Chlortetracycline Residues in Honey by Surface-enhanced Raman Spectroscopy†

Probabilistic risk model to assess the potential for resistance selection following the use of anti-microbial medicated feed in pigs

ABSTRACTThe cross-contamination of non-medicated feed with residues of anti-microbials (AM) causes a public and animal health concern associated with the potential for selection and dissemination of resistance. To analyse the associated risks, a probabilistic model was built using @Risk® (Palisade Corporation®) to show the potential extent of the effect of cross-contaminated pig feed on resistance selection. The results of the model include estimations of the proportion of pigs per production stage with residues of doxycycline, chlortetracycline, sulfadiazine and trimethoprim in their intestinal contents, as a result of exposure to cross-contaminated feed with different carry-over levels, in Belgium. By using a semi-quantitative approach, these estimations were combined with experimental data on AM concentrations associated with potential for resistance-selection pressure. Based on this model, it is estimated that 7.76% (min = 1.67; max = 36.94) of sows, 4.23% (min = 1.01%; max = 18.78%) of piglets and 2.8% (min = 0.51%; max = 14.9%) of fatteners in Belgium have residues of doxycycline in their intestinal tract due to consumption of feed with at least 1% carry-over. These values were estimated to be almost triple for sulfadiazine, but substantially lower for chlortetracycline and trimethoprim. Doxycycline concentrations as low as 1 mg/L (corresponding to consumed feed with at least 1% carry-over) can select for resistant porcine commensal Escherichia coli in vitro and in vivo. Conclusions on this risk could not be drawn for other AM at this stage, due to the lack of data on concentrations associated with resistance development. However, since the possibility of resistance mechanisms (e.g. co-selection) occurring cannot be excluded, the results of this model highlight that the use of AM medicated feed should be minimised where possible. In case of medicated feed production, good practice should be followed thoroughly at all levels of production, distribution, storage and administration, with a special focus on the feed distributed to piglets and sows.

Determination of Chlortetracycline Residues, Antimicrobial Activity and Presence of Resistance Genes in Droppings of Experimentally Treated Broiler Chickens.

Tetracyclines are important antimicrobial drugs for poultry farming that are actively excreted via feces and urine. Droppings are one of the main components in broiler bedding, which is commonly used as an organic fertilizer. Therefore, bedding becomes an unintended carrier of antimicrobial residues into the environment and may pose a highly significant threat to public health. For this depletion study, 60 broiler chickens were treated with 20% chlortetracycline (CTC) under therapeutic conditions. Concentrations of CTC and 4-epi-CTC were then determined in their droppings. Additionally, this work also aimed to detect the antimicrobial activity of these droppings and the phenotypic susceptibility to tetracycline in E. coli isolates, as well as the presence of tet(A), tet(B), and tet(G) resistance genes. CTC and 4-epi-CTC concentrations that were found ranged from 179.5 to 665.8 µg/kg. Based on these data, the depletion time for chicken droppings was calculated and set at 69 days. All samples presented antimicrobial activity, and a resistance to tetracyclines was found in bacterial strains that were isolated from these samples. Resistance genes tet(A) and tet(B) were also found in these samples.

Qualitative and quantitative drug residue analyses: Chlortetracycline in white-tailed deer (Odocoileus virginianus) and supermarket meat by liquid chromatography tandem-mass spectrometry

Chlortetracycline is (CTC) is a tetracycline antibiotic which is being in the white-tailed deer industry to improve production and animal health. In this paper, we present a method for determining chlortetracycline residues in edible white-tailed deer tissues, using liquid chromatography with heated electrospray ionization and mass spectrometry detection.The procedure involved extraction with EDTA-McIlvaine buffer at pH 4.0, followed by solid-phase extraction cleanup using a hydrophilic-lipophilic balance (HLB) cartridge. The liquid chromatography analysis was performed with heated electrospray ionization and mass spectrometry detection. The limit of quantification for the method was 2.7 ng/g and limit of detection was 0.8 ng/g. The recovery values were >78.5% for muscle, 65.1% for kidney, 63.1% for liver. Mean tissue residue concentration of chlortetracycline and it's epimer, 4-epi chlortetracycline (4-epi-CTC) at 10-day withdrawal period for kidney, liver, muscle was 122.8, 44.7 and 26.7 ng/g, respectively. Chlortetracycline tissue residue concentration at 45-day withdrawal period for kidney, liver, muscle was 19.2, 28.9 and 10.7 ng/g, respectively. Mean tissue concentration of CTC was less than the established maximum residual limit (MRL) values for bovine tissues. We have validated and successfully applied this method in the qualitative and quantification of chlortetracycline in white-tailed deer tissue samples.

Detection of Chlortetracycline Residues in pork Using Silver Nanoparticle Surface-Enhanced Fluorescence of Eu(III)-Chlortetracycline Complexes

Chlortetracycline (CTC) can form a stable complex with europium ion (Eu(III)), and the surface-enhanced fluorescence with silver nanoparticles (AgNPs) will produce the strong fluorescence in solution phase. When emulsifier OP-10 is added into the above solution phase, the fluorescence intensity of the complex can be further enhanced. In this research, the above mechanism was applied to detect CTC residues in pork. The pH values of pork extract which were extracted by Na2EDTA-Mcllvainc buffer were adjusted by using sodium hydroxide (NaOH) solution, and different concentrations of CTC in pork extract were determined. AgNPs, Eu(III), pork extract containing CTC and emulsifier OP-10 were sequentially mixed, and the fluorescence spectra of the mixture were collected.The comparative experimental methods were used to analyze the effects of AgNPs addition, Eu(III) addition, emulsifier OP-10addition and reaction time on the fluorescence intensity. It is revealed that a good linearity was obtained between the fluorescence intensity of the mixture at 617 nm and the CTC concentrations (0.1~20 mg/L) in pork extract. The linear equation was Y=0.8560X+38.020, and the determination coefficient was 0.9380. The determination coefficient between the actual value and the predictive value for the prediction samples was 0.9960, and the root mean square error (RMSEP) was 1.7869 mg/L. The results showed the experimental method, in which AgNPs and emulsifier OP-10 were used to enhance the fluorescence of Eu(III) and CTC complexes, could meet the demands of the rapid detection of CTC residues in pork.

Residues of chlortetracycline, doxycycline and sulfadiazine-trimethoprim in intestinal content and feces of pigs due to cross-contamination of feed.

BackgroundCross-contamination of feed with low concentrations of antimicrobials can occur at production, transport and/or farm level. Concerns are rising about possible effects of this contaminated feed on resistance selection in the intestinal microbiota. Therefore, an experiment with pigs was set up, in which intestinal and fecal concentrations of chlortetracycline (CTC), doxycycline (DOX) and sulfadiazine-trimethoprim (SDZ-TRIM) were determined after administration of feed containing a 3 % carry-over level of these antimicrobials.ResultsThe poor oral bioavailability of tetracyclines resulted in rather high concentrations in cecal and colonic content and feces at steady-state conditions. A mean concentration of 10 mg/kg CTC and 4 mg/kg DOX in the feces was reached, which is higher than concentrations that were shown to cause resistance selection. On the other hand, lower mean levels of SDZ (0.7 mg/kg) and TRIM (< limit of detection of 0.016 mg/kg) were found in the feces, corresponding with the high oral bioavailability of SDZ and TRIM in pigs.ConclusionsThe relation between the oral bioavailability and intestinal concentrations of the tested antimicrobials, may be of help in assessing the risks of cross-contaminated feed. However, future research is needed to confirm our results and to evaluate the effects of these detected concentrations on resistance selection in the intestinal microbiota of pigs.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-016-0803-8) contains supplementary material, which is available to authorized users.

Development of an ELISA and Immunochromatographic Assay for Tetracycline, Oxytetracycline, and Chlortetracycline Residues in Milk and Honey Based on the Class-Specific Monoclonal Antibody

A sensitive class-specific monoclonal antibody against tetracyclines (TCs) was generated and used to develop an enzyme-linked immunosorbent assay (ELISA) and an immunochromatographic assay for TC, oxytetracycline (OTC), and chlortetracycline (CTC) detection in milk and honey samples. The dynamic range of detection for TC in ELISA was 0.26–2.00 μg L−1 with an IC50 of 0.72 μg L−1. The IC50 value of OTC and CTC was 3.2 and 6.4 μg L−1, respectively. The recovery of TC, OTC, and CTC in milk samples was 82–102, 91–105, and 90–101 %, respectively, and 88–101, 89–101, and 89–95 % in honey samples, respectively. In the immunochromatographic assay, the cutoff values for TC, OTC, and CTC were 15, 15, and 50 μg L−1 in milk, respectively, and 40, 40, and 40 μg L−1 in honey, respectively. The results revealed that ELISA and the immunochromatographic assay can be applied for the rapid and sensitive detection of TC, OTC, and CTC in milk and honey samples.

Tetracycline resistance genes persist in soil amended with cattle feces independently from chlortetracycline selection pressure

Antibiotic residues and antibiotic resistance genes originating from animal waste represent environmental pollutants with possible human health consequences. In this study, we addressed the question whether chlortetracycline (CTC) residues in soils can act as selective pressure enhancing the persistence of tetracycline (TC-r) resistance genes in grassland soils receiving cattle feces. We performed a soil microcosm experiment, using 3 grassland soils with different management history, which were incubated with feces from conventionally raised dairy cows. The microcosms included treatments with a low dose (0.2 mg kg−1), a high dose (100 mg kg−1) and no CTC. The presence and abundance of TC-r genes tet(O), tet(Q) and tet(W) and the intI1 gene coding for class 1 integrase were assessed with real-time PCR after 0, 14, 28, 56 and 86 d of incubation. The genes tet(Q) and intI1 persisted in all feces-containing treatments for at least 28 d, and tet(W) and tet(O) for at least 86 d, though they went close to limits of quantification after 14–28 d in most cases. The soil, but not the dose of CTC, significantly affected the gene persistence. Concluding, certain TC-r genes originating from cattle feces may persist in soil for several months independently from antibiotic selection pressure.

Determination of Tetracyclines Residues in Aquatic Products by HPLC

A sensitive method for simultaneously determining residues of oxytetracycline, tetracycline ,chlortetracycline and doxycycline in aquatic product was established by HPLC. Samples were extracted with Na2EDTA-Mcllvaine buffer solutions and centrifuged.The sample extracts were cleaned up by C18 solid-phase extraction cartridge and then were determined by UV detection at 355 nm.At fortification levels of 0.005~0.1 mg/kg, the average recoveries were of 75%~96% , The RSDs were of 1.02%~6.56%,Limit of detection was 0.002 mg /kg for oxytetracycline,tetracycline and doxycycline and 0.005 mg /kg for chlortetracycline.The sensitivity, accuracy and precision of this method were able to meet the requirements for pesticide residue analysis.

Microbial response to repeated treatments of manure containing sulfadiazine and chlortetracycline in soil

Substantive addition of antibiotic-contaminated manure to agricultural soil may lead to “persistent” residues of antibiotics and may affect soil health. Therefore, this study examines the effects of repeated manure treatments containing sulfadiazine (SDZ) and chlortetracycline (CTC) residues, both individually and combined, on the functional diversity and structure of soil microbial communities in the soils under laboratory conditions. The average well color development (AWCD), Simpson diversity index (1/D, dominant populations), Shannon-Wiener diversity index (H′, richness), and McIntosh diversity index (U, evenness) in the antibiotics-treated soils decreased in the first 60-day treatment and then gradually recovered or even exceeded the initial level in the unamended soils with increasing treatment frequency. A total of 11 specific bands in temperature gradient gel electrophoresis (TGGE) profiles were observed and sequence analyzed for five repeated treatments, and most of them belonged to the phyla Firmicutes, Actinobacteria, and Proteobacteria. These results indicate that repeated treatments of manure containing SDZ and CTC residues can alter soil microbial community structure, although they have a temporary suppression effect on soil microbial functional diversity.

Escherichia coli tetracycline efflux determinants in relation to tetracycline residues in chicken

ObjectiveTo screen for Escherichia coli (E. coli) resistant to tetracycline, followed by identification of tet efflux genes by polymerase chain reaction (PCR). In addition, detection of tetracycline residues in chicken livers and kidneys were conducted using high performance liquid chromatography-tandem quadrupole mass spectrometry (HPLC-MS-MS). MethodsStrains of E. coli were isolated from samples of chicken colon and screened for tetracycline resistance. Tetracycline genes conferring resistance (Tcr) were detected by polymerase chain reaction (PCR). Most of the isolates were resistant to tetracycline (97.9%). ResultsPCR analysis indicated that TcrE. coli R-plasmids contained tet(A), tet(B) and a combination of both efflux genes. None of the isolates contained other efflux tet genes tet (C, D, E and Y). High performance liquid chromatography-tandem quadrupole mass spectrometry (HPLC-MS-MS), a sensitive technique, was used to detect residues of chlortetracycline (CTC), oxytetracycline (OTC), doxycycline (DC) in chicken livers and kidneys. The samples containing tetracycline residues were at 0.13-0.65 pg/μL levels. ConclusionsTetracycline and other antibiotics are commonly used in the poultry and meat production industry for prevention of microbial infections. Multiple antibiotic resistant bacteria in Oman have increased to alarming levels, threatening public health, domestic and may have adverse effect on environment.