scholarly journals Optical Screening for Rapid Antimicrobial Susceptibility Testing and for Observation of Phenotypic Diversity among Strains of the Genetically Clonal Species Bacillus anthracis

2017 ◽  
Vol 55 (3) ◽  
pp. 959-970 ◽  
Author(s):  
Heather P. McLaughlin ◽  
Amy S. Gargis ◽  
Pierre Michel ◽  
David Sue ◽  
Linda M. Weigel
Keyword(s):  
Antimicrobial Resistance ◽  
Bacillus Anthracis ◽  
Antimicrobial Susceptibility ◽  
Antimicrobial Agents ◽  
Phenotypic Diversity ◽  
New Technology ◽  
Time Lapse ◽  
Growth Characteristics ◽  
Content Type ◽  
Broth Microdilution Method

ABSTRACTDuring high-impact events involvingBacillus anthracis, such as the Amerithrax incident of 2001 or the anthrax outbreaks in Russia and Sweden in 2016, critical decisions to reduce morbidity and mortality include rapid selection and distribution of effective antimicrobial agents for treatment and postexposure prophylaxis. Detection of antimicrobial resistance currently relies on a conventional broth microdilution method that requires a 16- to 20-h incubation time forB. anthracis. Advances in high-resolution optical screening offer a new technology to more rapidly evaluate antimicrobial susceptibility and to simultaneously assess the growth characteristics of an isolate. Herein, we describe a new method developed and evaluated as a rapid antimicrobial susceptibility test forB. anthracis. This method is based on automated digital time-lapse microscopy to observe the growth and morphological effects of relevant antibiotics with an optical screening instrument, the oCelloScope.B. anthracisstrains were monitored over time in the presence or absence of penicillin, ciprofloxacin, or doxycycline. Susceptibility to each antibiotic was determined in ≤4 h, 75 to 80% less than the time required for conventional methods. Time-lapse video imaging compiled from the optical screening images revealed unexpected differences in growth characteristics among strains ofB. anthracis, which is considered to be a clonal organism. This technology provides a new approach for rapidly detecting phenotypic antimicrobial resistance and for documenting growth attributes that may be beneficial in the further characterization of individual strains.

Antimicrobial Resistance in Campylobacter jejuni from Broilers and Broiler House Environments in Norway

2007 ◽  
Vol 70 (3) ◽  
pp. 736-738 ◽  
Author(s):  
M. NORSTRÖM ◽  
G. JOHNSEN ◽  
M. HOFSHAGEN ◽  
H. THARALDSEN ◽  
H. KRUSE
Keyword(s):  
Antimicrobial Resistance ◽  
Campylobacter Jejuni ◽  
Antimicrobial Susceptibility ◽  
Antimicrobial Agents ◽  
Monitoring Program ◽  
Outdoor Environment ◽  
Susceptibility Data ◽  
Microdilution Method ◽  
Broth Microdilution Method ◽  
Broiler House

Antimicrobial susceptibility in Campylobacter jejuni collected from the environment outside four broiler houses (n = 63) and from the environment inside these broiler houses (including broiler droppings) (n = 36) from May to September 2004 was studied and compared with isolates from Norwegian broilers analyzed within the frame of the Norwegian monitoring program of antimicrobial resistance in feed, food, and animals (NORM-VET) in 2004 (n = 75). The MICs of oxytetracycline, ampicillin, erythromycin, gentamicin, enrofloxacin, and nalidixic acid were obtained by the broth microdilution method VetMIC. The present study, which to our knowledge is the first Norwegian study on the occurrence of antimicrobial resistance in Campylobacter spp. from the environment of broiler houses, revealed a very low occurrence of antimicrobial resistance in C. jejuni from the broilers and broiler house environments studied. All isolates originating from the four broiler houses studied were susceptible to all the antimicrobial agents tested, except for one isolate from the outdoor environment (courtyard soil), which was resistant to oxytetracycline (MIC, 8 mg/liter). For the isolates from broilers (NORM-VET), low prevalences of resistance to oxytetracycline (1.3%) and ampicillin (4%) were observed. No quinolone resistance was observed. The results for the broiler isolates are in agreement with the earlier findings of a very low prevalence of resistance in Campylobacter from broilers in Norway, which reflects the low usage of antimicrobials in Norwegian broiler production. Furthermore, the present data are in accordance with antimicrobial susceptibility data for C. jejuni from domestically acquired human cases.

scholarly journals Prevalence, genetic characterization, and antimicrobial resistance of Salmonella isolated from meat goats in the Northeastern region of Thailand

2021 ◽  
Vol 19 (3) ◽  
pp. 363-378
Author(s):  
Wattanasak Chamlakhorn ◽  
◽  
Patchara Phuektes ◽  
Seri Khang-Air ◽  
Sunpetch Angkititrakul ◽  
...  
Keyword(s):  
Antimicrobial Resistance ◽  
Antimicrobial Susceptibility ◽  
Antimicrobial Agents ◽  
Genetic Characterization ◽  
Genotypic Diversity ◽  
Resistance Pattern ◽  
Chromosomal Dna ◽  
Northeastern Region ◽  
Meat Goats ◽  
Broth Microdilution Method

This study aimed to determine the prevalence, genotypic diversity, and antimicrobial resistance pattern of Salmonella isolated from meat goats in the Northeastern region of Thailand. A total of 1,014 rectal swabs were collected from 30 meat goat farms during April to November, 2018. Salmonella was isolated and identified according to the International Organization for Standardization protocol (ISO-6579:2002/AMD:2017) and serotyped using a slide agglutination test following the Kauffmann-White scheme. An antimicrobial susceptibility test to determine minimal inhibitory concentration (MIC) of 12 antimicrobial agents was performed using a broth microdilution method following the CLSI protocol (2017). Pulsed-field gel electrophoresis (PFGE) of XbaI digested chromosomal DNA was used to determine genotypic diversity of the isolates. The overall prevalence of Salmonella in the meat goats was 1.28%. A total of 13 Salmonella isolates recovered from the meat goats belonged to 4 serovars includings. Weltevreden (n=4), S. Bovismorbificans (n=4), S. Paratyphi B (n=4), and S. Stanley (n=1). Antimicrobial susceptibility testing revealed 2 antibiogram patternS. Eleven Salmonella isolates were susceptible to all antimicrobial agents tested, except sulfamethoxazole, and the other 2 isolates were susceptible to all antimicrobials. Genetic characterization of 13 Salmonella isolates by PFGE revealed 9 PFGE patterns that were grouped into 4 major clusters, A, B, C and D, with an 80% similarity value. This study revealed a low prevalence of Salmonella in meat goats in the Northeastern region of Thailand. Salmonella isolates were susceptible to most antimicrobials tested, with a very high proportion of resistance to sulfamethoxazole being observed.

scholarly journals Prevalence of Antimicrobial Resistance among Clinical Isolates of Bacteroides fragilis Group in Canada in 2010-2011: CANWARD Surveillance Study

2011 ◽  
Vol 56 (3) ◽  
pp. 1247-1252 ◽  
Author(s):  
James A. Karlowsky ◽  
Andrew J. Walkty ◽  
Heather J. Adam ◽  
Melanie R. Baxter ◽  
Daryl J. Hoban ◽  
...  
Keyword(s):  
Antimicrobial Agents ◽  
Bacteroides Fragilis ◽  
Clinical Isolates ◽  
Surveillance Study ◽  
Content Type ◽  
Microdilution Method ◽  
Broth Microdilution Method ◽  
Amoxicillin Clavulanate ◽  
Bacteroides Fragilis Group ◽  
Bacteroides Ovatus

ABSTRACTClinical isolates of theBacteroides fragilisgroup (n= 387) were collected from patients attending nine Canadian hospitals in 2010-2011 and tested for susceptibility to 10 antimicrobial agents using the Clinical and Laboratory Standards Institute (CLSI) broth microdilution method.B. fragilis(59.9%),Bacteroides ovatus(16.3%), andBacteroides thetaiotaomicron(12.7%) accounted for ∼90% of isolates collected. Overall rates of percent susceptibility were as follows: 99.7%, metronidazole; 99.5%, piperacillin-tazobactam; 99.2%, imipenem; 97.7%, ertapenem; 92.0%, doripenem; 87.3%, amoxicillin-clavulanate; 80.9%, tigecycline; 65.9%, cefoxitin; 55.6%, moxifloxacin; and 52.2%, clindamycin. Percent susceptibility to cefoxitin, clindamycin, and moxifloxacin was lowest forB. thetaiotaomicron(n= 49, 24.5%),Parabacteroides distasonis/P. merdae(n= 11, 9.1%), andB. ovatus(n= 63, 31.8%), respectively. One isolate (B. thetaiotaomicron) was resistant to metronidazole, and two isolates (bothB. fragilis) were resistant to both piperacillin-tazobactam and imipenem. Since the last published surveillance study describing Canadian isolates ofB. fragilisgroup almost 20 years ago (A.-M. Bourgault et al., Antimicrob. Agents Chemother. 36:343–347, 1992), rates of resistance have increased for amoxicillin-clavulanate, from 0.8% (1992) to 6.2% (2010-2011), and for clindamycin, from 9% (1992) to 34.1% (2010-2011).

scholarly journals Antimicrobial Susceptibility to Azithromycin among Salmonella enterica Isolates from the United States

2011 ◽  
Vol 55 (9) ◽  
pp. 3985-3989 ◽  
Author(s):  
Maria Sjölund-Karlsson ◽  
Kevin Joyce ◽  
Karen Blickenstaff ◽  
Takiyah Ball ◽  
Jovita Haro ◽  
...  
Keyword(s):  
United States ◽  
Antimicrobial Susceptibility ◽  
Salmonella Enterica ◽  
Antimicrobial Agents ◽  
The United States ◽  
Outcome Data ◽  
Content Type ◽  
Susceptibility Data ◽  
Retail Meat ◽  
Clinical Breakpoints

ABSTRACTDue to emerging resistance to traditional antimicrobial agents, such as ampicillin, trimethoprim-sulfamethoxazole, and chloramphenicol, azithromycin is increasingly used for the treatment of invasiveSalmonellainfections. In the present study, 696 isolates of non-TyphiSalmonellacollected from humans, food animals, and retail meats in the United States were investigated for antimicrobial susceptibility to azithromycin. Seventy-twoSalmonella entericaserotype Typhi isolates from humans were also tested. For each isolate, MICs of azithromycin and 15 other antimicrobial agents were determined by broth microdilution. Among the non-TyphiSalmonellaisolates, azithromycin MICs among human isolates ranged from 1 to 32 μg/ml, whereas the MICs among the animal and retail meat isolates ranged from 2 to 16 μg/ml and 4 to 16 μg/ml, respectively. AmongSalmonellaserotype Typhi isolates, the azithromycin MICs ranged from 4 to 16 μg/ml. The highest MIC observed in the present study was 32 μg/ml, and it was detected in three human isolates belonging to serotypes Kentucky, Montevideo, and Paratyphi A. Based on our findings, we propose an epidemiological cutoff value (ECOFF) for wild-typeSalmonellaof ≤16 μg/ml of azithromycin. The susceptibility data provided could be used in combination with clinical outcome data to determine tentative clinical breakpoints for azithromycin andSalmonella enterica.

scholarly journals Antimicrobial Susceptibility of 260Clostridium botulinumType A, B, Ba, and Bf Strains and a NeurotoxigenicClostridium baratiiType F Strain Isolated from California Infant Botulism Patients

2018 ◽  
Vol 62 (12) ◽  
Author(s):  
Jason R. Barash ◽  
Joe B. Castles ◽  
Stephen S. Arnon
Keyword(s):  
Antimicrobial Susceptibility ◽  
Large Bowel ◽  
Botulinum Neurotoxin ◽  
Antimicrobial Agents ◽  
Infectious Complications ◽  
Suspected Sepsis ◽  
Content Type ◽  
Infant Botulism ◽  
Susceptibility Study ◽  
Almost All

ABSTRACTInfant botulism is an infectious intestinal toxemia that results from colonization of the infant large bowel byClostridium botulinum(or rarely, by neurotoxigenicClostridium baratiiorClostridium butyricum), with subsequent intraintestinal production and absorption of botulinum neurotoxin that then produces flaccid paralysis. The disease is often initially misdiagnosed as suspected sepsis or meningitis, diagnoses that require prompt empirical antimicrobial therapy. Antibiotics may also be needed to treat infectious complications of infant botulism, such as pneumonia or urinary tract infection. Clinical evidence suggests (see case report below) that broad-spectrum antibiotics that are eliminated by biliary excretion may cause progression of the patient’s paralysis by lysingC. botulinumvegetative cells in the large bowel lumen, thereby increasing the amount of botulinum neurotoxin available for absorption. The purpose of this antimicrobial susceptibility study was to identify an antimicrobial agent with little or no activity againstC. botulinumthat could be used to treat infant botulism patients initially diagnosed with suspected sepsis or meningitis, or who acquired secondary infections, without lysingC. botulinum. Testing of 12 antimicrobial agents indicated that almost all California infant botulism patient isolates are susceptible to most clinically utilized antibiotics and are also susceptible to newer antibiotics not previously tested against large numbers ofC. botulinumpatient isolates. No antibiotic with little or no activity againstC. botulinumwas identified. These findings reinforce the importance of promptly treating infant botulism patients with human botulism immune globulin (BIG-IV [BabyBIG]).

Difference in drug susceptibility distribution and clinical characteristics between Mycobacterium avium and Mycobacterium intracellulare lung diseases in Shanghai, China

2021 ◽  
Vol 70 (5) ◽  
Author(s):  
Weiping Wang ◽  
Jinghui Yang ◽  
Xiaocui Wu ◽  
Baoshan Wan ◽  
Hongxiu Wang ◽  
...  
Keyword(s):  
Mycobacterium Avium ◽  
Antimicrobial Susceptibility ◽  
Type Species ◽  
Clinical Characteristics ◽  
Radiographic Findings ◽  
Content Type ◽  
Mycobacterium Intracellulare ◽  
Link Type ◽  
Broth Microdilution Method ◽  
Significant Difference

Introduction. Mycobacterium avium complex (MAC) has been reported as the most common aetiology of lung disease involving nontuberculous mycobacteria. Hypothesis. Antimicrobial susceptibility and clinical characteristics may differ between Mycobacterium avium and Mycobacterium intracellulare . Aim. We aimed to evaluate the differences in antimicrobial susceptibility profiles between two major MAC species ( Mycobacterium avium and Mycobacterium intracellulare ) from patients with pulmonary infections and to provide epidemiologic data with minimum inhibitory concentration (MIC) distributions. Methodology. Between January 2019 and May 2020, 45 M. avium and 242 M . intracellulare isolates were obtained from Shanghai Pulmonary Hospital. The demographic and clinical characteristics of patients were obtained from their medical records. The MICs of 13 antimicrobials were determined for the MAC isolates using commercial Sensititre SLOWMYCO MIC plates and the broth microdilution method, as recommended by the Clinical and Laboratory Standards Institute (CLSI; Standards M24-A2). MIC50 and MIC90 values were derived from the MIC distributions. Results. M. intracellulare had higher resistance rates than M. avium for most tested antimicrobials except clarithromycin, ethambutol, and ciprofloxacin. Clarithromycin was the most effective antimicrobial against both the M. avium (88.89 %) and M. intracellulare (91.32 %) isolates, with no significant difference between the species (P=0.601). The MIC90 of clarithromycin was higher for M. avium (32 µg ml−1) than M. intracellulare (8 µg ml−1). The MIC50 of rifabutin was more than four times higher for M. intracellulare (1 µg ml−1) than M. avium (≤0.25 µg ml−1). The percentages of patients aged >60 years and patients with sputum, cough, and cavitary lesions were significantly higher than among patients with M. intracellulare infection than M. avium infections. Conclusions. The pulmonary disease caused by distinct MAC species had different antimicrobial susceptibility, symptoms, and radiographic findings.

scholarly journals Characterization of Multidrug Resistance Patterns of Emerging Salmonella enterica Serovar Rissen along the Food Chain in China

Antibiotics ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 660
Author(s):  
Xuebin Xu ◽  
Silpak Biswas ◽  
Guimin Gu ◽  
Mohammed Elbediwi ◽  
Yan Li ◽  
...  
Keyword(s):  
Antimicrobial Resistance ◽  
Foodborne Pathogens ◽  
Food Chain ◽  
Salmonella Enterica ◽  
Antimicrobial Agents ◽  
Animal Husbandry ◽  
Multidrug Resistant ◽  
Salmonella Spp ◽  
Broth Microdilution Method ◽  
Resistance Patterns

Salmonella spp. are recognized as important foodborne pathogens globally. Salmonella enterica serovar Rissen is one of the important Salmonella serovars linked with swine products in numerous countries and can transmit to humans by food chain contamination. Worldwide emerging S. Rissen is considered as one of the most common pathogens to cause human salmonellosis. The objective of this study was to determine the antimicrobial resistance properties and patterns of Salmonella Rissen isolates obtained from humans, animals, animal-derived food products, and the environment in China. Between 2016 and 2019, a total of 311 S. Rissen isolates from different provinces or province-level cities in China were included here. Bacterial isolates were characterized by serotyping and antimicrobial susceptibility testing. Minimum inhibitory concentration (MIC) values of 14 clinically relevant antimicrobials were obtained by broth microdilution method. S. Rissen isolates from humans were found dominant (67%; 208/311). S. Rissen isolates obtained from human patients were mostly found with diarrhea. Other S. Rissen isolates were acquired from food (22%; 69/311), animals (8%; 25/311), and the environment (3%; 9/311). Most of the isolates were resistant to tetracycline, trimethoprim-sulfamethoxazole, chloramphenicol, streptomycin, sulfisoxazole, and ampicillin. The S. Rissen isolates showed susceptibility against ceftriaxone, ceftiofur, gentamicin, nalidixic acid, ciprofloxacin, and azithromycin. In total, 92% of the S. Rissen isolates were multidrug-resistant and ASSuT (27%), ACT (25%), ACSSuT (22%), ACSSuTAmc (11%), and ACSSuTFox (7%) patterns were among the most prevalent antibiotic resistance patterns found in this study. The widespread dissemination of antimicrobial resistance could have emerged from misuse of antimicrobial agents in animal husbandry in China. These findings could be useful for rational antimicrobial usage against Salmonella Rissen infections.

scholarly journals Analysis of Whole-Genome Sequences for the Prediction of Penicillin Resistance and β-Lactamase Activity inBacillus anthracis

mSystems ◽  
2018 ◽  
Vol 3 (6) ◽  
Author(s):  
A. S. Gargis ◽  
H. P. McLaughlin ◽  
A. B. Conley ◽  
C. Lascols ◽  
P. A. Michel ◽  
...  
Keyword(s):  
Sequence Analysis ◽  
Antimicrobial Susceptibility ◽  
Sigma Factor ◽  
Antimicrobial Agents ◽  
Susceptibility Testing ◽  
Antimicrobial Susceptibility Testing ◽  
Penicillin Resistance ◽  
Whole Genome ◽  
Activity Levels ◽  
Content Type

ABSTRACTPenicillin (PEN) is a low-cost option for anthrax treatment, but naturally occurring resistance has been reported. β-Lactamase expression (bla1,bla2) inBacillus anthracisis regulated by a sigma factor (SigP) and its cognate anti-sigma factor (RsiP). Mutations leading to truncation of RsiP were previously described as a basis for PEN resistance. Here, we analyze whole-genome sequencing (WGS) data and compare the chromosomalsigP-bla1regions from 374B. anthracisstrains to determine the frequency of mutations, identify mutations associated with PEN resistance, and evaluate the usefulness of WGS for predicting PEN resistance. Few (3.5%) strains contained at least 1 of 11 different mutations insigP,rsiP, orbla1.Nine of these mutations have not been previously associated with PEN resistance. Four strains showed PEN resistance (PEN-R) by conventional broth microdilution, including 1 strain with a novel frameshift inrsiP. One strain that carries the samersiPframeshift mutation as that found previously in a PEN-R strain showed a PEN-susceptible (PEN-S) phenotype and exhibited decreasedbla1andbla2transcription. An unexpectedly small colony size, a reduced growth rate, and undetectable β-lactamase activity levels (culture supernatant and cell lysate) were observed in this PEN-S strain. Sequence analysis revealed mutations in genes associated with growth defects that may contribute to this phenotype. WhileB. anthracisrsiPmutations cannot be exclusively used to predict resistance, four of the five strains withrsiPmutations were PEN-R. Therefore, theB. anthracissigP-bla1region is a useful locus for WGS-based PEN resistance prediction, but phenotypic testing remains essential.IMPORTANCEDetermination of antimicrobial susceptibility ofB. anthracisis essential for the appropriate distribution of antimicrobial agents for postexposure prophylaxis (PEP) and treatment of anthrax. Analysis of WGS data allows for the rapid detection of mutations in antimicrobial resistance (AMR) genes in an isolate, but the presence of a mutation in an AMR gene does not always accurately predict resistance. As mutations in the anti-sigma factor RsiP have been previously associated with high-level penicillin resistance in a limited number of strains, we investigated WGS assemblies from 374 strains to determine the frequency of mutations and performed functional antimicrobial susceptibility testing. Of the five strains that contained mutations inrsiP, only four were PEN-R by functional antimicrobial susceptibility testing. We conclude that while sequence analysis of this region is useful for AMR prediction inB. anthracis, genetic analysis should not be used exclusively and phenotypic susceptibility testing remains essential.

scholarly journals In Vitro Activity of Eravacycline against Gram-Positive Bacteria Isolated in Clinical Laboratories Worldwide from 2013 to 2017

2019 ◽  
Vol 64 (3) ◽  
Author(s):  
Ian Morrissey ◽  
Stephen Hawser ◽  
Sibylle H. Lob ◽  
James A. Karlowsky ◽  
Matteo Bassetti ◽  
...  
Keyword(s):  
Antimicrobial Agents ◽  
Clinical Isolates ◽  
Gram Positive ◽  
Content Type ◽  
Gram Positive Bacteria ◽  
Microdilution Method ◽  
Clinical Laboratories ◽  
Broth Microdilution Method ◽  
Doubling Dilution

ABSTRACT Eravacycline is a novel, fully synthetic fluorocycline antibiotic being developed for the treatment of serious infections, including those caused by resistant Gram-positive pathogens. Here, we evaluated the in vitro activities of eravacycline and comparator antimicrobial agents against a recent global collection of frequently encountered clinical isolates of Gram-positive bacteria. The CLSI broth microdilution method was used to determine in vitro MIC data for isolates of Enterococcus spp. (n = 2,807), Staphylococcus spp. (n = 4,331), and Streptococcus spp. (n = 3,373) isolated primarily from respiratory, intra-abdominal, urinary, and skin specimens by clinical laboratories in 37 countries on three continents from 2013 to 2017. Susceptibilities were interpreted using both CLSI and EUCAST breakpoints. There were no substantive differences (a >1-doubling-dilution increase or decrease) in eravacycline MIC90 values for different species/organism groups over time or by region. Eravacycline showed MIC50 and MIC90 results of 0.06 and 0.12 μg/ml, respectively, when tested against Staphylococcus aureus, regardless of methicillin susceptibility. The MIC90 values of eravacycline for Staphylococcus epidermidis and Staphylococcus haemolyticus were equal (0.5 μg/ml). The eravacycline MIC90s for Enterococcus faecalis and Enterococcus faecium were 0.06 μg/ml and were within 1 doubling dilution regardless of the vancomycin susceptibility profile. Eravacycline exhibited MIC90 results of ≤0.06 μg/ml when tested against Streptococcus pneumoniae and beta-hemolytic and viridans group streptococcal isolates. In this surveillance study, eravacycline demonstrated potent in vitro activity against frequently isolated clinical isolates of Gram-positive bacteria (Enterococcus, Staphylococcus, and Streptococcus spp.), including isolates collected over a 5-year period (2013 to 2017), underscoring its potential benefit in the treatment of infections caused by common Gram-positive pathogens.

scholarly journals Prevalence of Cefotaxime-Resistant Escherichia coli Isolates from Healthy Cattle and Sheep in Northern Spain: Phenotypic and Genome-Based Characterization of Antimicrobial Susceptibility

2020 ◽  
Vol 86 (15) ◽  
Author(s):  
Maitane Tello ◽  
Medelin Ocejo ◽  
Beatriz Oporto ◽  
Ana Hurtado
Keyword(s):  
Antimicrobial Resistance ◽  
Resistance Genes ◽  
Antimicrobial Susceptibility ◽  
Basque Country ◽  
Northern Spain ◽  
Content Type ◽  
E Coli ◽  
Extended Spectrum ◽  
Cattle Herds ◽  
Cattle And Sheep

ABSTRACT In order to estimate herd-level prevalence of extended-spectrum β-lactamase/AmpC β-lactamase (ESBL/AmpC)- and carbapenemase-producing commensal Escherichia coli in ruminants in the Basque Country (northern Spain), a cross-sectional survey was conducted in 2014 to 2016 in 300 herds using selective isolation. ESBL-/AmpC-producing E. coli was isolated in 32.9% of dairy cattle herds, 9.6% of beef cattle herds, and 7.0% of sheep flocks. No carbapenemase-producing E. coli was isolated. Phenotypic antimicrobial susceptibility determined by broth microdilution using EUCAST epidemiological cutoff values identified widespread coresistance to extended-spectrum cephalosporins and other antimicrobials (110/135 isolates), particularly tetracycline, sulfamethoxazole, trimethoprim, and ciprofloxacin. All isolates were susceptible to tigecycline, imipenem, meropenem, and colistin. The genomes of 66 isolates were sequenced using an Illumina NovaSeq 6000 and screened for antimicrobial resistance determinants against ResFinder and PointFinder. The plasmid/chromosomal locations of resistance genes were predicted with PlasFlow, and plasmid replicons were identified using PlasmidFinder. Fifty-two acquired resistance genes and point mutations in another four genes that coded for resistance to 11 antimicrobial classes were identified. Fifty-five genomes carried ESBL-encoding genes, blaCTX-M-14 being the most common, and 11 carried determinants of the AmpC phenotype, mostly the blaCMY-2 gene. Additionally, genes coding for β-lactamases of the CTX-M group 9 were detected as well as the sporadic presence of blaSHV-12, blaCMY-4, and a point mutation in the ampC promoter. Only a bovine isolate coharbored more than one ESBL/AmpC genetic determinant (blaCTX-M-14 and a mutation in the ampC promoter), confirming its ESBL- and AmpC β-lactamase-producing phenotype. Most ESBL/AmpC genes were located in IncI1 plasmids, which also carried a great variety of other antimicrobial resistance genes. IMPORTANCE Extended-spectrum β-lactamase (ESBL)- and AmpC β-lactamase (AmpC)-producing E. coli isolates have emerged in recent years as some of the fastest spreading antimicrobial resistance determinants in humans and food-producing animals, becoming a concern for animal and public health. This study provided insight into the prevalence of cefotaxime-resistant E. coli in cattle and sheep in the Basque Country and the associated genetic determinants of antimicrobial resistance. These constituted an important contribution to the limited repository of such data for cattle in the region and for sheep worldwide. Antimicrobial susceptibility testing by phenotypic and molecular methods is key in surveillance programs to enhance early detection of resistance development, monitor resistance trends, and provide guidance to clinicians in selecting the adequate therapy.

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