scholarly journals Genotyping and antimicrobial resistance in Escherichia coli from pig carcasses

2017 ◽  
Vol 37 (11) ◽  
pp. 1253-1260 ◽  
Author(s):  
Caroline Pissetti ◽  
Gabriela Orosco Werlang ◽  
Jalusa Deon Kich ◽  
Marisa Cardoso
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Resistance ◽  
Antimicrobial Agents ◽  
Commensal Bacteria ◽  
Pfge Analysis ◽  
Gene Detection ◽  
E Coli ◽  
Antimicrobial Resistance Profile ◽  
Resistant Strains ◽  
Pig Carcasses

ABSTRACT: The increasing antimicrobial resistance observed worldwide in bacteria isolated from human and animals is a matter of extreme concern and has led to the monitoring of antimicrobial resistance in pathogenic and commensal bacteria. The aim of this study was to evaluate the antimicrobial resistance profile of Escherichia coli isolated from pig carcasses and to assess the occurrence of relevant resistance genes. A total of 319 E. coli isolates were tested for antimicrobial susceptibility against different antimicrobial agents. Moreover, the presence of extended-spectrum β-lactamase (ESBL) and inducible ampC-β-lactamase producers was investigated. Eighteen multi-resistant strains were chosen for resistance gene detection and PFGE characterization. The study showed that resistance to antimicrobials is widespread in E. coli isolated from pig carcasses, since 86.2% of the strains were resistant to at least one antimicrobial and 71.5% displayed multi-resistance profiles. No ampC-producing isolates were detected and only one ESBL-producing E. coli was identified. Genes strA (n=15), floR (n=14), aac(3)IVa (n=13), tetB (n=13), sul2 (n=12), tetA (n=11), aph(3)Ia (n=8) and sul3 (n=5) were detected by PCR. PFGE analysis of these multi-resistant E. coli strains showed less than 80% similarity among them. We conclude that antimicrobial multi-resistant E. coli strains are common on pig carcasses and present highly diverse genotypes and resistance phenotypes and genotypes.

scholarly journals RESISTANCE TO FLUOROQUINOLONES IN ESCHERICHIA COLI FROM PIGS

2016 ◽  
Vol 8 (2) ◽  
pp. 103-112 ◽  
Author(s):  
Dalibor Todorović ◽  
Maja Velhner ◽  
Dragana Ljubojević ◽  
Marko Pajić ◽  
Dubravka Milanov
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Resistance ◽  
General Population ◽  
Digestive Tract ◽  
Food Production ◽  
Antimicrobial Agents ◽  
E Coli ◽  
Nearby Region ◽  
Pig Farms ◽  
Resistant Strains

The resistance of Escherichia coli (E. coli) to fluoroquinolones has become a serious issue on large pig farms worldwide, since these antimicrobial agents are widely used in the control of various diseases such as neonatal diarrhea, post weaning diarrhea, the edema disease as well as others. Being a frequent inhabitant of the digestive tract, E.coli is oft en exposed to antimicrobial agents, which are used to treat various infections. Uncontrolled application of fluoroquinolones has led to the emergence of resistant pathogenic strains as well as commensals. The spread of resistant strains is mostly found in animal and human food production chains, which are potentially huge threat for the general population. The resistance to fluoroquinolones may very oft en be combined with the resistance to other classes of antibiotics. Therefore, the use of fluoroquinolones for treating uncomplicated infections in pigs must be under strict control or completely banned. In this paper, we compared the results from available literature addressing the prevalence of antimicrobial resistance to fl uoroquinolones in E. coli strains both worldwide and in countries from the nearby region.

scholarly journals Susceptibility to antibiotics in escherichiae isolated in a multidisciplinary medical centre

2016 ◽  
Vol 65 (4) ◽  
pp. 83-89
Author(s):  
Nadezda S. Kozlova ◽  
Natalia E. Barantsevich ◽  
Elena P. Barantsevich
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Multidrug Resistance ◽  
Antimicrobial Resistance ◽  
Antimicrobial Agents ◽  
E Coli ◽  
Microdilution Method ◽  
Carbapenem Resistant ◽  
Resistant Strains ◽  
High Level

Relevance. Antimicrobial resistance in nosocomial strains currently presents a very important problem.  Aim of the study: Study of antibiotic resistance in Escherichia coli, isolated in a multidisciplinary centre.  Materials and Methods. Susceptibility of 151 E. coli strains to 15 antibiotics was studied by microdilution method. Results. The majority of the studied strains were resistant to antibiotics, including: ampicillin (57.0%), ciprofloxacin and moxifloxacin (42.4% each), III and IV generation cephalosporins (37.1% and 34.4%, respectively) and gentamycin (29.1%). The highest activity against E. coliwas shown for carbapenems (resistance to erthapenem – 2.6%, meropenem – 0.7%), in particular, for imipenem – no strains resistant to this drug were isolated. Resistance to amikacin and phosphomycin was low: 3.3% and 1.3% respectively. Wide diversity of antibiotic resistance spectra was revealed in studied strains, with a high level of multidrug resistance (48.0%). Conclusion. Study of susceptibility to antimicrobial agents in E. coli, isolated in a multidisciplinary centre, showed predominance of resistant strains with a high level of multidrug resistance. The appearance of carbapenem-resistant strains in a multidisciplinary centre presents a rising problem.

scholarly journals The level of antimicrobial resistance of sewage isolates is higher than that of river isolates in different Escherichia coli lineages

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Yoshitoshi Ogura ◽  
Takuya Ueda ◽  
Kei Nukazawa ◽  
Hayate Hiroki ◽  
Hui Xie ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Resistance ◽  
Resistance Genes ◽  
Antimicrobial Agents ◽  
Environmental Water ◽  
Resistant Bacteria ◽  
Whole Genome ◽  
E Coli ◽  
Antimicrobial Resistance Genes ◽  
Resistant Strains

Abstract The dissemination of antimicrobial-resistant bacteria in environmental water is an emerging concern in medical and industrial settings. Here, we analysed the antimicrobial resistance of Escherichia coli isolates from river water and sewage by the use of a combined experimental phenotypic and whole-genome-based genetic approach. Among the 283 tested strains, 52 were phenotypically resistant to one or more antimicrobial agents. The E. coli isolates from the river and sewage samples were phylogenetically indistinguishable, and the antimicrobial-resistant strains were dispersedly distributed in a whole-genome-based phylogenetic tree. The prevalence of antimicrobial-resistant strains as well as the number of antimicrobials to which they were resistant were higher in sewage samples than in river samples. Antimicrobial resistance genes were more frequently detected in strains from sewage samples than in those from river samples. We also found that 16 river isolates that were classified as Escherichia cryptic clade V were susceptible to all the antimicrobials tested and were negative for antimicrobial resistance genes. Our results suggest that E. coli strains may acquire antimicrobial resistance genes more frequently and/or antimicrobial-resistant E. coli strains may have higher rates of accumulation and positive selection in sewage than in rivers, irrespective of their phylogenetic distribution.

scholarly journals Impact of Feed Supplementation with Antimicrobial Agents on Growth Performance of Broiler Chickens, Clostridium perfringens and Enterococcus Counts, and Antibiotic Resistance Phenotypes and Distribution of Antimicrobial Resistance Determinants in Escherichia coli Isolates

2007 ◽  
Vol 73 (20) ◽  
pp. 6566-6576 ◽  
Author(s):  
Moussa S. Diarra ◽  
Fred G. Silversides ◽  
Fatoumata Diarrassouba ◽  
Jane Pritchard ◽  
Luke Masson ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Antimicrobial Resistance ◽  
Broiler Chickens ◽  
Antimicrobial Agents ◽  
Growth Promoters ◽  
Feed Supplementation ◽  
E Coli ◽  
Resistance Determinants ◽  
Class 1

ABSTRACT The effects of feed supplementation with the approved antimicrobial agents bambermycin, penicillin, salinomycin, and bacitracin or a combination of salinomycin plus bacitracin were evaluated for the incidence and distribution of antibiotic resistance in 197 commensal Escherichia coli isolates from broiler chickens over 35 days. All isolates showed some degree of multiple antibiotic resistance. Resistance to tetracycline (68.5%), amoxicillin (61.4%), ceftiofur (51.3%), spectinomycin (47.2%), and sulfonamides (42%) was most frequent. The levels of resistance to streptomycin, chloramphenicol, and gentamicin were 33.5, 35.5, and 25.3%, respectively. The overall resistance levels decreased from day 7 to day 35 (P < 0.001). Comparing treatments, the levels of resistance to ceftiofur, spectinomycin, and gentamicin (except for resistance to bacitracin treatment) were significantly higher in isolates from chickens receiving feed supplemented with salinomycin than from the other feeds (P < 0.001). Using a DNA microarray analysis capable of detecting commonly found antimicrobial resistance genes, we characterized 104 tetracycline-resistant E. coli isolates from 7- to 28-day-old chickens fed different growth promoters. Results showed a decrease in the incidence of isolates harboring tet(B), bla TEM, sulI, and aadA and class 1 integron from days 7 to 35 (P < 0.01). Of the 84 tetracycline-ceftiofur-resistant E. coli isolates, 76 (90.5%) were positive for bla CMY-2. The proportions of isolates positive for sulI, aadA, and integron class 1 were significantly higher in salinomycin-treated chickens than in the control or other treatment groups (P < 0.05). These data demonstrate that multiantibiotic-resistant E. coli isolates can be found in broiler chickens regardless of the antimicrobial growth promoters used. However, the phenotype and the distribution of resistance determinants in E. coli can be modulated by feed supplementation with some of the antimicrobial agents used in broiler chicken production.

scholarly journals Antimicrobial Resistance Profile of Escherichia coli Isolates from Different Clinical Samples in Abeokuta, Ogun State

2020 ◽  
pp. 12-18
Author(s):  
S. L. Owolabi ◽  
I. A. Azeez
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Resistance ◽  
Multiple Drug Resistance ◽  
Resistance Rate ◽  
Clinical Samples ◽  
Isolation And Identification ◽  
Resistance Profile ◽  
E Coli ◽  
Ogun State ◽  
Antimicrobial Resistance Profile

The alarming increase of antibiotic resistance of Escherichia coli has posed a great challenge in the public health sector. Thus, this microorganism is a leading cause of different human infections and it can be found in various environments. The aim of this study is to investigate the antimicrobial susceptibility patterns and the multiple antimicrobial resistance profile of Escherichia coli isolates obtained from some hospitals in Abeokuta, Ogun State, Nigeria. Isolates of E. coli were obtained from different clinical samples and were re-identified morphologically and biochemically. E. coli was isolated from 30% out of a total of 70 clinical samples analyzed for isolation and identification. The isolation rate of E. coli was highest in urine samples 10(47.6%) when compared to other clinical samples. There was significant increase in the resistance rate of E. coli to tetracycline (14.3%), ceftazidime (14.2%), and ampicillin (14.2%).Also, an increased sensitivity rate to augmentin (71.4%), ofloxacin (66.7%), cefuroxime (66.7%), ciprofloxacin (61.9%) and ceftazidime (61.9%) were observed. Furthermore, the overall multiple drug resistance rates obtained was 14(66.7%) and it was established that, multiple antimicrobial resistance of the E. coli isolates was plasmid mediated. E. coli isolates exhibited high resistance rate to multiple antimicrobial agents, however, its sensitivity to augmentin, ofloxacin, cefuroxime, ciprofloxacin and ceftazidime showed that these antimicrobials are still effective against E. coli infections in the study area.

scholarly journals Molecular characterisation of antimicrobial resistance and virulence genes in Escherichia coli strains isolated from diarrhoeic and healthy rabbits in Tunisia

2020 ◽  
Vol 28 (2) ◽  
pp. 81
Author(s):  
Raouia Ben Rhouma ◽  
Ahlem Jouini ◽  
Amira Klibi ◽  
Safa Hamrouni ◽  
Aziza Boubaker ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Resistance ◽  
Virulence Genes ◽  
Antimicrobial Agents ◽  
Antibiotic Resistance Genes ◽  
Virulence Gene ◽  
Diffusion Method ◽  
Class 1 Integron ◽  
E Coli ◽  
Class 1

The purpose of this study was to identify <em>Escherichia coli</em> isolates in diarrhoeic and healthy rabbits in Tunisia and characterise their virulence and antibiotic resistance genes. In the 2014-2015 period, 60 faecal samples from diarrhoeic and healthy rabbits were collected from different breeding farms in Tunisia. Susceptibility to 14 antimicrobial agents was tested by disc diffusion method and the mechanisms of gene resistance were evaluated using polymerase chain reaction and sequencing methods. Forty <em>E. coli</em> isolates were recovered in selective media. High frequency of resistance to tetracycline (95%) was detected, followed by different levels of resistance to sulphonamide (72.5%), streptomycin (62.5%), trimethoprim-sulfamethoxazole (60%), nalidixic acid (32.5%), ampicillin (37.5%) and ticarcillin (35%). <em>E. coli</em> strains were susceptible to cefotaxime, ceftazidime and imipenem. Different variants of bla<sub>TEM</sub>, <em>tet</em>, <em>sul</em> genes were detected in most of the strains resistant to ampicillin, tetracycline and sulphonamide, respectively. The presence of class 1 integron was studied in 29 sulphonamide-resistant <em>E. coli</em> strains from which 15 harboured class 1 integron with four different arrangements of gene cassettes, <em>dfrA17</em>+<em>aadA5</em> (n=9), <em>dfrA1</em> + <em>aadA1</em> (n=4), <em>dfrA12</em> + <em>addA2</em> (n=1), <em>dfrA12</em>+<em>orf</em>+<em>addA2</em> (n=1). The <em>qnrB</em> gene was detected in six strains out of 13 quinolone-resistant <em>E. coli</em> strains. Seventeen <em>E. coli</em> isolates from diarrhoeic rabbits harboured the enteropathogenic eae genes associated with different virulence genes tested (<em>fimA</em>, <em>cnf1</em>, <em>aer</em>), and affiliated to B2 (n=8) and D (n=9) phylogroups. Isolated <em>E. coli</em> strains from healthy rabbit were harbouring <em>fim A</em> and/or <em>cnf1</em> genes and affiliated to A and B1 phylogroups. This study showed that <em>E. coli</em> strains from the intestinal tract of rabbits are resistant to the widely prescribed antibiotics in medicine. Therefore, they constitute a reservoir of antimicrobial-resistant genes, which may play a significant role in the spread of antimicrobial resistance. In addition, the eae virulence gene seemed to be implicated in diarrhoea in breeder rabbits in Tunisia.

Antimicrobial Resistance and Association with Class 1 Integrons in Escherichia coli Isolated from Turkey Meat Products

2008 ◽  
Vol 71 (8) ◽  
pp. 1679-1684 ◽  
Author(s):  
M. L. KHAITSA ◽  
J. OLOYA ◽  
D. DOETKOTT ◽  
R. KEGODE
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Resistance ◽  
Antimicrobial Agents ◽  
Population Attributable Fraction ◽  
Meat Products ◽  
Resistance Mechanisms ◽  
E Coli ◽  
Class 1 Integrons ◽  
Turkey Meat ◽  
Class 1

The objective of this study was to quantify the role of class 1 integrons in antimicrobial resistance in Escherichia coli isolated from turkey meat products purchased from retail outlets in the Midwestern United States. Of 242 E. coli isolates, 41.3% (102 of 242) tested positive for class 1 integrons. A significant association was shown between presence of class 1 integrons in E. coli isolates and the resistance to tetracycline, ampicillin, streptomycin, gentamicin, sulfisoxazole, and trimethoprim-sulfamethoxazole. Attributable risk analysis revealed that for every 100 E. coli isolates carrying class 1 integrons, resistance was demonstrated for ampicillin (22%), gentamycin (48%), streptomycin (29%), sulfisoxazole (40%), trimethoprimsulfamethoxazole (7%), and tetracycline (26%). Non–integron-related antimicrobial resistance was demonstrated for ampicillin (65%), gentamycin (16.9%), streptomycin (42.1%), sulfisoxazole (35.8%), and tetracycline (49.7%). Population-attributable fraction analysis showed that class 1 integrons accounted for the following resistances: gentamycin, 71% (50 of 71), amoxicillin–clavulanic acid, 19.6% (6 of 33), nalidixic acid, 34% (7 of 21), streptomycin, 28% (30 of 107), sulfisoxazole, 38% (40 of 106), and tetracycline, 14%, (26 of 185). In conclusion, although class 1 integrons have been implicated in resistance to antimicrobial agents, other non–integron resistance mechanisms seem to play an important part.

scholarly journals Effect of Antimicrobial Dosage Regimen on Salmonella and Escherichia coli Isolates from Feeder Swine

2008 ◽  
Vol 74 (6) ◽  
pp. 1731-1739 ◽  
Author(s):  
Bruce A. Wagner ◽  
Barbara E. Straw ◽  
Paula J. Fedorka-Cray ◽  
David A. Dargatz
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Resistance ◽  
Commensal Bacteria ◽  
Antimicrobial Use ◽  
Control Analysis ◽  
Fecal Samples ◽  
E Coli ◽  
The Impact ◽  
Susceptibility And Resistance ◽  
Continuous Pulse

ABSTRACT A body of evidence exists that suggests that antimicrobial use in food animals leads to resistance in both pathogenic and commensal bacteria. This study focused on the impact of three different antimicrobial regimes (low-level continuous, pulse, and no antimicrobial) for two antimicrobials (chlortetracycline and tylosin) on the presence of Salmonella spp. and on the prevalence of antimicrobial resistance of both Salmonella spp. and nonspecific Escherichia coli in fecal samples from feeder swine. The prevalence of fecal samples positive for Salmonella spp. significantly decreased between the samples taken at feeder placement compared to samples taken when the animals were close to market weight. Differences in resistance of Salmonella spp. did not appear to be influenced by dosing treatment including the control. Analysis of antimicrobial resistance examining both susceptibility and resistance, as well as MIC outcomes, demonstrated that only resistance to cephalothin increased in E. coli under the pulse chlortetracycline treatment. These results suggest that the dosing regimes examined in this study did not lead to an increase in either the prevalence of Salmonella spp. or the prevalence of antimicrobial resistance in isolates of Salmonella spp. or E. coli.

Detection of Multiple-Antimicrobial Resistance and Characterization of the Implicated Genes in Escherichia coli Isolates from Foods of Animal Origin in Tunis

2009 ◽  
Vol 72 (5) ◽  
pp. 1082-1088 ◽  
Author(s):  
AHLEM JOUINI ◽  
KARIM BEN SLAMA ◽  
YOLANDA SÁENZ ◽  
NAOUEL KLIBI ◽  
DANIELA COSTA ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Resistance ◽  
Antimicrobial Agents ◽  
Food Samples ◽  
Animal Origin ◽  
E Coli ◽  
Antimicrobial Resistance Genes ◽  
Class 1 ◽  
Agar Dilution

Phenotypic and genotypic characterization of antimicrobial resistance was conducted for 98 Escherichia coli isolates recovered from 40 food samples of animal origin (poultry, sheep, beef, fish, and others) obtained in supermarkets and local butcheries in Tunis during 2004 and 2005. Susceptibility to 15 antimicrobial agents was tested by disk diffusion and agar dilution methods, the mechanisms of resistance were evaluated using PCR and sequencing methods, and the clonal relationship among isolates was evaluated using pulsed-field gel electrophoresis. High resistance was detected to tetracycline, sulphonamides, nalidixic acid, ampicillin, streptomycin, and trimethoprim-sulfamethoxazole (29 to 43% of isolates), but all isolates were susceptible to cefotaxime, ceftazidime, cefoxitin, azthreonam, and amikacin. One-third of the isolates had multiresistant phenotypes (resistance to at least five different families of antimicrobial agents). Different variants of blaTEM, tet, sul, dfrA, aadA, and aac(3) genes were detected in most of the strains resistant to ampicillin, tetracycline, sulphonamide, trimethoprim, streptomycin, and gentamicin, respectively. The presence of class 1 and class 2 integrons was studied in 15 sulphonamide-resistant unrelated E. coli strains, and 14 of these strains harbored class 1 integrons with five different arrangements of gene cassettes, and a class 2 integron with the dfrA1 + sat + aadA1 arrangement was found in one strain. This study revealed the high diversity of antimicrobial resistance genes, some of them included in integrons, in E. coli isolates of food origin.

scholarly journals Antimicrobial Resistance in ESBL-Producing Escherichia coli Isolated from Layer and Pig Farms in Thailand

2018 ◽  
Vol 46 (1) ◽  
pp. 8 ◽  
Author(s):  
Aniroot Nuangmek ◽  
Suvichai Rojanasthien ◽  
Suwit Chotinun ◽  
Panuwat Yamsakul ◽  
Pakpoom Tadee ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Resistance ◽  
Function Analysis ◽  
Commensal Bacteria ◽  
Farm Worker ◽  
Stagnant Water ◽  
E Coli ◽  
Pig Farms ◽  
Resistance Patterns ◽  
Pig Farm

Background: Study of drug resistance of commensal bacteria in both humans and animals can determine the scale of the drug resistance problem. Usage of antimicrobials to treat infections in humans and animals has generated extensive antimicrobial pressure not only on targeted pathogens but also on commensal bacteria. Commensal Escherichia coli appears to be the major reservoir for resistant genes implicated in the transmission of genetic traits from one bacterium to another. Antimicrobial resistance in Enterobacteriaceae has increased dramatically worldwide in the last decade. An increasing number of community-onset extended-spectrum beta-lactamase (ESBL)-producing bacterial infections, especially those caused by ESBL-producing E. coli, have been reported in many countries, including Thailand. Moreover, ESBL-producing E. coli have been widely detected in food-producing animals and the environment. The increased use of ESBLs in food animals is a serious public health problem. The objective of the study was to determine the prevalence and antimicrobial resistance pattern of ESBL-producing E. coli isolated from pigs, layers, farm workers and stagnant water, in order to increase awareness about antimicrobial usage on farms and to minimize the expansion of the antimicrobial resistance phenomenon in farm settings.Materials, Methods & Results: A total of 588 samples were collected from 107 pig farms and 89 layer farms in Chiang Mai–Lamphun and Chon Buri provinces during May 2015-April 2016. Double-disk diffusion method according to EUCAST (European Committee on Antimicrobial Susceptibility Testing) guidelines was used for detection. The results demonstrated that 36.7% (216/588) of samples were ESBL-producing E. coli-positive, including rectal swabs 74.8% (80/107), pig farm worker stool swabs 57.0% (61/107), stagnant water on pig farms 21.5% (23/107), healthy layer rectal swabs 6.7% (6/89) and layer farm worker stool swabs 51.7% (46/89). Most of the isolates were resistant against ampicillin (99.5%), followed by erythromycin (98.6%) and ceftriaxone (96.3%). All of them were classified as multidrug-resistant strains. Moreover, AMP-CRO-E-TE-C-SXT-CN was the most frequent phenotype pattern detected in animals, humans and the environment, followed by AMP-CRO-E-TE-C-SXT-NA-CN.Discussion: The present study offers clear evidence that the prevalence of ESBL-producing E. coli in healthy pigs is higher than in layers. One possible explanation is that a large amount and variety of antimicrobials are used on pig farms, resulting in a common and significant source of drug-resistant ESBL-producing E. coli. The lower incidence of ESBL-producing E. coli in samples from a pig farm environment than in samples of animal origin indicate that pigs are a reservoir of a reservoir for resistant bacteria and a source of environmental contamination. Antimicrobial resistance patterns of ESBLproducing E. coli detected in all sample types and study locations were quite similar. In almost all ESBL-producing E. coli isolates, resistance was shown against ampicillin, erythromycin, ceftriaxone, tetracycline and chloramphenicol. Moreover, multidrug resistance was found in all isolates of ESBL-producing E. coli. The differences in antimicrobial agent resistance patterns can be used to differentiate sources by employing analytical tools such as discriminant function analysis. A molecular typing protocol is recommended for use in a discriminant function analysis for pattern determination of pathogen spreading. However, genetic fingerprinting techniques for microbial source tracking are more expensive, and facilities with appropriate equipment and expertise are required.

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