Double-disk Test Research Articles

Isolation of Escherichia coli and Klebsiella pneumoniae strains producing extended spectrum β-lactamases from dog urine of the Metropolitan Area of the Aburrá Valley Antioquia-Colombia

Escherichia coli and Klebsiella pneumoniae are the most common pathogens causing urinary tract infections in humans and animals. Close contact between humans and companion animals can facilitate the spread of multidrugresistant pathogens between both species. Objective: To characterize extended-spectrum β-lactamases (ESBL) -producing E. coli and K. pneumoniae isolated from dogs with urinary tract infections in the metropolitan area of Valle del Aburrá (Antioquia, Colombia). Methods: Three-hundred seventy-one urine samples collected from March 2018 to March 2019 in a veterinary clinical laboratory were analyzed. E. coli and K. pneumoniae isolates were detected in chromogenic agar and identified by biochemical tests. Susceptibility testing was performed by disc diffusion and ESBL production was evaluated by the double disk test in all isolates. MIC determination of ESBL-positive isolates were performed on the automated VITEK®2 system. Multiple PCR was used for the detection of CTX-M beta-lactamases (group 1, 2, 9 and 8/25), SHV, TEM and AmpC of plasmid origin in ESBL-positive isolates. Results: In total 22 out 371 isolates were positive for ESBL production by double disc test, 11 E. coli (ESBL-Ec) and 11 K. pneumoniae (ESBL-Kp). The multiple PCR detected CTX-M group 1 in the 22 ESBL-positive isolates. Multi-drug resistance was observed in all ESBL-producing isolates Conclusions: A high frequency of antibiotic multi-resistance was found in ESBL-Ec and ESBL-Kp. The main ESBL detected was CTX-M group 1, which also prevails in human isolates.

Molecular detection of extended spectrum ?-lactamase producing Klebsiella pneumoniae from wild deer

Abstract. Riwu KHP, Rantam FA, Effendi MH, Khairullah AR, Widodo A, Kurniawan SC, Ugbo EN. 2022. Molecular detection of extended spectrum ?-lactamase producing Klebsiella pneumoniae from wild deer. Biodiversitas 23: 4256-4262. Antimicrobial resistance (AMR) has become a severe threat worldwide and its remote cause remains unclear in most parts due to the global emergence of new resistance mechanisms by microorganisms. This research aimed to identify the presence of extended-spectrum ?-lactamase (ESBL) Klebsiella pneumoniae from wild deer feces in several places in East Java and East Nusa Tenggara. This study used 129 fresh feces samples collected from wild deer and analyzed for the presence of K. pneumoniae using standard microbiological techniques. An antibiotic sensitivity test was performed using Kirby-Bauer Disc Diffusion Method. The isolates were confirmed to the ESBL producer by double disk test and ESBL genes were identified by PCR. Nine samples (6.98%) were K. pneumoniae positive out of the 129 wild deer fresh feces. Among the nine K. pneumoniae isolates studied 3 (33.33%) were multidrug resistant, East Java (1 isolate) and East Nusa Tenggara (2 isolates). All the multidrug-resistant K. pneumoniae isolates were ESBL positive and also harbored blaTEM gene. The presence of MDR, and ESBL-producing K. pneumoniae isolates was confirmed in wild deer and this explained that wild deer should be considered a source of transmission of MDR and ESBL to public health.

STUDY OF MAGNITUDE OF UTI CAUSED BY ESBL-PRODUCING ESCHERICHIA COLI AND ASSOCIATED RISK FACTORS

Objective: Globally, urinary tract infections (UTIs) caused by Escherichia coli that produce extended-spectrum lactamase (ESBL) have become more common. Our study determined the magnitude of UTI occurring due to ESBL-producing E. coli and associated risk factors. Different methods for their phenotypic detection were also compared. Methods: Uropathogenic E. coli isolated in significant numbers were assayed microbiologically. E. coli isolates (n=247) that were found significant in number tested for ESBL production using three different phenotypic methods: Phenotypic combined disk diffusion test (PCDDT), double-disk approximation test (DDAT), and E-test for ESBL production. An antibiotic susceptibility test was performed for different antibiotics. Various risk factors associated with UTIs were correlated with ESBL- and non-ESBL-producing E. coli. Results: We found that diabetes mellitus type 2 was the most common risk factor for UTI caused due to ESBL-producing E. coli (25%). Pregnant females and patients having recurrent UTI showed less positivity for ESBL production. DDAT detected 32 ESBL-positive isolates and PCDDT detected 37 positive isolates. E-test was taken as the gold standard for ESBL detection which detected 49 isolates as ESBL producers. The highest sensitivity (71.2%) and specificity (75%) were shown by PCDDT. Conclusion: According to the study conducted, it was concluded that PCDDT was the most reliable and economic method for phenotypic detection of ESBL.

Phenotypic and molecular characterization of extended-spectrum β-lactamase/AmpC- and carbapenemase-producing Klebsiella pneumoniae in Iran.

The objective of the current study is to evaluate the phenotypic and molecular characterization of ESBL/AmpC- and carbapenemase-producing K. pneumoniae isolates in Iran. From October 2018 until the end of April 2020, different clinical samples were collected and K. pneumoniae isolates were identified using conventional biochemical tests and PCR assay. Antibiotic susceptibility pattern was determined using the Kirby-Bauer disk diffusion method. Modified Hedge Test (MHT) was applied to the identification of carbapenemase-producing K. pneumoniae. ESBL and AmpC-producing K. pneumoniae were detected using Double Disc Test (DDT) and Disc Potentiation Test (DPT), respectively. The presence of carbapenemase, ESBL, and AmpC encoding genes was screened by Polymerase Chain Reaction (PCR) assay. A total of 100 K. pneumoniae isolates were collected. K. pneumoniae isolates had the highest resistance rate to cefazolin (66%) and cefotaxime (66%). Meropenem and amikacin with sensitivity rates of 76% and 69% were the most effective antimicrobial agents on K. pneumoniae isolates. It was found that 12 (12%), 27 (27%), and 9 (9%) K. pneumoniae isolates were positive in MHT, DDT, and DPT tests, respectively. Among the carbapenemase-encoding genes, blaOXA-48 (24%) and blaIMP (13%) genes had the highest frequency, while blaKPC and blaGIM genes were not detected among K. pneumoniae isolates. blaTEM (48%) and blaCMY (8%) genes had the highest frequency among ESBL and AmpC β-lactamase-encoding genes, respectively. It is vital to adopt effective control strategies for K. pneumoniae infections and ensure rapid identification of antibiotic resistance profile.

Food Is Reservoir of MDR Salmonella: Prevalence of ESBLs Profiles and Resistance Genes in Strains Isolated from Food.

Salmonella spp. are among the most frequent causes of foodborne diseases, and the increasing occurrence of MDR strains is an additional cause for concern. In the three-year period 2019–2021, we collected Salmonella spp. strains isolated from different food categories analysed in the context of Regulation (EC) No 2073/2005 in order to assess their antibiotic susceptibility profiles and ESBL production. To determine the susceptibility profiles and identify MDR strains, we used the Kirby–Bauer method to test 17 antibiotics. Double-disc and PCR testing then allowed us to assess the production of ESBLs and the presence of beta-lactamase resistance genes. Phenotypic tests showed that 36 out of 67 strains were MDR and 52.7% of these were ESBL producers. Finally, molecular investigations conducted on ESBL-producing strains revealed the presence of blaSHV, blaCTX-M and blaTEM genes. Our results confirmed the prevalence of S. Infantis, an MDR strain and ESBL producer, in chicken meat. This suggests that further research on the prevalence of antibiotic resistance genes (ARGs) in foodborne strains is needed, especially from a One Health perspective.

Diffusion of OXA-48 carbapenemase among urinary isolates of Klebsiella pneumoniae in non-hospitalized elderly patients

BackgroundRecently, a dramatic increase of Klebsiella pneumoniae positive for OXA-48 β-lactamases was observed first in the hospital setting and later in the long-term care facilities (LTCFs) and community in the Zagreb County, particularly, in urinary isolates. The aim of the study was to analyse the epidemiology and the mechanisms of antibiotic resistance of OXA-48 carbapenemase producing K. pneumoniae strains isolated from urine of non-hospitalized elderly patients.ResultsThe isolates were classified into two groups: one originated from the LTCFs and the other from the community. Extended-spectrum β-lactamases (ESBLs) were detected by double disk-synergy (DDST) and combined disk tests in 55% of the isolates (51/92). The ESBL-positive isolates exhibited resistance to expanded-spectrum cephalosporins (ESC) and in majority of cases to gentamicin. LTCFs isolates showed a significantly lower rate of additional ESBLs and consequential resistance to ESC and a lower gentamicin resistance rate compared to the community isolates, similarly to hospital isolates in Zagreb, pointing out to the possible transmission from hospitals.ESBL production was associated with group 1 of CTX-M or SHV-12 β-lactamases. Ertapenem resistance was transferable from only 12 isolates. blaOXA-48 genes were carried by IncL plasmid in 42 isolates. In addition IncFII and IncFIB were identified in 18 and 2 isolates, respectively. Two new sequence types were reported: ST4870 and ST4781.ConclusionsThis study showed eruptive and extensive diffusion of OXA-48 carbapenemase to LTCFs and community population in Zagreb County, particularly affecting patients with UTIs and urinary catheters. On the basis of susceptibility testing, β-lactamase production, conjugation experiments, MLST and plasmid characterization it can be concluded that there was horizontal gene transfer between unrelated isolates, responsible for epidemic spread of OXA-48 carbapenemase in the LTCFs and the community The rapid spread of OXA-48 producing K. pneumoniae points out to the shortcomings in the infection control measures.

Molecular characterization of NDM-1-producing Pseudomonas aeruginosa isolates from hospitalized patients in Iran

BackgroundThe emergence of carbapenem-resistant Pseudomonas aeruginosa is one of the most important challenges in a healthcare setting. The aim of this study is double-locus sequence typing (DLST) typing of blaNDM-1 positive P. aeruginosa isolates.MethodsTwenty-nine blaNDM-1 positive isolates were collected during three years of study from different cities in Iran. Modified hodge test (MHT), double-disk synergy test (DDST) and double-disk potentiation test (DDPT) was performed for detection of carbapenemase and metallo-beta-lactamase (MBL) producing blaNDM-1 positive P. aeruginosa isolates. The antibiotic resistance genes were considered by PCR method. Clonal relationship of blaNDM-1 positive was also characterized using DLST method.ResultsAntibiotic susceptibility pattern showed that all isolates were resistant to imipenem and ertapenem. DDST and DDPT revealed that 15/29 (51.8%) and 26 (89.7%) of blaNDM-1 positive isolates were MBL producing isolates, respectively. The presence of blaOXA-10,blaVIM-2, blaIMP-1 and blaSPM genes were detected in 86.2%, 41.4%, 34.5% and 3.5% isolates, respectively. DLST typing results revealed the main cluster were DLST 25-11 with 13 infected or colonized patients.ConclusionsThe presence of blaNDM-1 gene with other MBLs encoding genes in P. aeruginosa is a potential challenge in the treatment of microorganism infections. DLST showed partial diversity among 29 blaNDM-1 positive isolates.

The effect of environmental factors on the abundance of cefotaxime-resistant Escherichia coli in Sunter River

The water quality of the Sunter River in Jakarta was classified as heavily polluted due to activities around the river, both domestic and non-domestic. As one of the environmental parameters for water quality, the presence of Escherichia coli (E. coli) is normally found any natural environment, and under certain conditions it can become resistant to antimicrobials due to genetic mutations. The mutated E. coli produces Extended Spectrum Beta-Lactamase (ESBL) enzymes and has a higher survival ability in antibiotic-contaminated river water, thus potentially endangering public health. This study was aimed to evaluate the effect of environmental factors on the abundance of ESBL producing E. coli and their resistance to antibiotic cefotaxime. Sampling was conducted in six locations representing the upstreams and the downstreams of Sunter River, following the Global Surveillance guidelines. E. coli strains were isolated using Tryptone Bile X-glucuronide (TBX) agar medium (with and without the addition of cefotaxime 4μg/ml) and the antibiotic sensitivity test of ESBL E. coli was conducted by performing a double-disk test. The results showed that the highest average abundance of ESBL E. coli was found in the sample taken from Sindang Station (904.24 x 104 colony per unit (CFU) / 100 mL) and the lowest was from Sunter Station (1,58 x 104 CFU / 100 mL). The results of the Bivariate Pearson correlation analysis showed that temperature, pH, and salinity were negatively correlated with the abundance of ESBL-producing E. coli bacteria.

Study on the effect of rotational speed on the polygonisation formation mechanism, microstructure and property evolution of D2 wheel steel

The D2 wheel steel rolling wear experiment was carried out on a double-disc wear test machine. By observing the polygonisation wear of the sample surface, measuring the vibration frequency, and analyzing sample microstructure and properties, the effects of rotational speed on the polygonisation formation mechanism, microstructure and property evolution of a D2 wheel steel were studied within a certain speed range. The results indicated that polygonisation wear was the result of the coupling of vibration and wear. The dominant vibration frequency (f) was constant at the three rotational speeds studied, and was equal to the product of the rotational speed (ω) and polygonisation order (K), that is, f=160Kω. When the number of rolling cycles was the same, the sample surface became subject to more times vibration and impact as the rotational speed decreased. This increased the intensity of the wear, and the polygonisation wear began to occur faster. Conversely, the polygonisation wear caused the vibration and impact load to increase, and the coupling effect of wear and vibration increased, further aggravating the polygonisation wear. After polygonisation wear occurred, the degree of crest oxidation wear was reduced in relation to the decreasing rotational speed. The degree of trough fatigue wear was also aggravated, causing the polygonisation wear gap to become larger, while the mass wearing quantity increased significantly given the same number of rolling cycles. The thickness of the obvious plastic deformation layer, the microstructure refinement, and the change in hardness of the surface layer all increased with the intensification of polygonisation wear.

Molecular Epidemiology of AmpC-Producing Klebsiella Pneumoniae Isolated from Perioperative Patients in a Tertiary Hospital

Background: Extended-spectrum cephalosporin-resistant organisms are the sources of AmpC- type β-lactamase isolates. AmpC-producing Klebsiella pneumoniae isolates are a major challenge in clinics due to their high rate of antibiotic resistance. This study aimed to detect AmpC β-lactamases in K. pneumoniae isolated from hospitalized patients with a surgical history. Materials and Methods: This cross-sectional study was performed on 120 urine catheter samples. After antibiotic susceptibility testing, plasmid-mediated AmpC was detected by double-disc plus combined disc test (DCDT) and three-dimensional extract test (TDET). The genotypic detection of plasmid-mediated AmpC was carried out using multiplex-polymerase chain reaction (PCR). Results: Of 120 samples, 60 (50%) instances of K. pneumoniae were isolated. The highest and lowest resistance rates were related to cefotaxime (CTX) (50%) and ciprofloxacin (CIP) (23.3%), respectively. 18.3% (n: 11) K. pneumoniae showed an AmpC phenotype in DCDT and TDET tests. AmpC genotyping showed that the prevalence of CIT, DHA, EBC, and ACC genotypes were 47.1%, 35.3%, 29.5%, and 23.6%, respectively. MOX and FOX genotypes were not identified in the isolates of interest. Conclusion: AmpC β-lactamase identification tests should be considered a routine microbiology workup for gram-negative microorganisms. Multiplex-PCR can identify the plasmid AmpC genotypes.

PREVALENCE OF ANTIMICROBIAL RESISTANCE AND MOLECULAR CHARACTERIZATION OF CARBAPENEMASE ENCODING GENE IN ESCHERICHIA COLI ISOLATES IN HOSPITAL OF HUE UNIVERSITY OF MEDICINE AND PHARMACY

Background: Currently, the existence of Extended-spectrum beta-lactamases (ESBL) and carbapenemase genes as well as genetic diversity has led to the rapid spread of resistance between E. coli species and the emergence of bacteria with pan-resistance. Objectives: To investigate the prevalence of antimicrobial resistance, prevalence of ESBL-producing E. coli, and carbapenemase-coding gene in E. coli isolates at Hospital of Hue University of Medicine and Pharmacy. Materials and method: The susceptibility to 13 antimicrobials of 246 E. coli isolates was detemined by the Kirby-Bauer method. ESBL-producing potential E. coli isolates were confirmed phenotypic by the Double Disc Synergy Test (DDST) and Combination Disc Test (CDT). Using multiplex PCR to detect genes encoding carbapenemase belonging to class B (Metallo β-lactamase), class D (oxacillinase), and blaKPC gene. Sequencing of carbapenemase genes were used to identify carbapenemase variants. Results: 91.46% of E. coli strains were identified as multidrug-resistant; most of them resistant to penicillins, fluoroquinolone, sulfonamide; high frequency of resistance to 3rd generation cephalosporin, chloramphenicol, gentamycin. The high isolation rate of ESBL-producing E. coli (50%) was detected. The resistance to carbapenems was largely mediated by the expression of acquired carbapenemases: blaKPC-2, blaNDM-4, and blaOXA-48. This study first reported blaNDM-4-harboring E. coli isolates in Vietnam. Conclusion: The high prevalence of multidrug-resistant and ESBL-producing E. coli, as well as the coexistence of ESBLs and carbapenemase genes, could seriously limit options for clinical treatment.

Green tea extract-mediated augmentation of imipenem antibacterial activity against Enterobacter cloacae clinical isolates

The emergence of pathogenic bacteria with β-lactam antibiotics-resistant profile has threatened the continued use of such antibiotics in the future. This research was conducted to investigate the antimicrobial activity of green tea ethanol extract (GTE) and its ability to improve the antibacterial action of several β-lactam antibiotics against Enterobacter cloacae clinical isolates. The simplicia of green tea was extracted by sonication for 30 minutes using 50% ethanol solvent, and the total phenolic content of the GTE was subsequently determined. Next, the GTE used in testing against two clinical isolates of E. cloacae was obtained from the Pathology Laboratory of Wahidin Sudiro Husodo Hospital in Makassar. The sensitivity of bacteria to GTE was confirmed using the agar diffusion method, the Vitek® rapid method, and the double-disk synergistic test. Antibacterial activity of antibiotics, GTE, and combination of antibiotics with GTE were then tested against clinical isolates of E. cloacae using the checkerboard microdilution assay. The results showed that GTE contained 51.64 ± 0.21 % measured as gallic acid equivalent and 37.95 + 5.17 % Epigallocatechin gallate (EGCG). The confirmatory test results indicated that one clinical isolate of E. cloacae (code 13/04) was resistant to amoxicillin-clavulanate but did not produce an extended-spectrum β-lactamase (ESBL). Another clinical E. cloacae isolate (code 275B/06) was indicated to produce ESBL and demonstrated to yield resistance to amoxicillin-clavulanate and cefotaxime. The minimum inhibitory concentration of GTE against the two clinical isolates of E. cloacae was >8000 ppm (8 mg/ml). In conclusion, GTE could not increase the antibacterial activity of amoxicillin and cefotaxime, but it was sufficient to improve the activity of imipenem against the tested isolates of E. cloacae .

Phenotypic and molecular characterization of multidrug-resistant extended-spectrum beta-lactamase-producing Salmonella prevalent in raw chicken meat vended in Nigerian markets

Abstract In Nigeria, there is still a scarcity of data on the recovery of multidrug-resistant ESBL-producing Salmonella in chicken meat. Hence this study characterized the probable multidrug-resistant extended-spectrum beta-lactamase-producing Salmonella prevalent in chilled raw chicken meat vended in Nigerian markets. Detection of Salmonella was performed by meat rinse centrifugation-plating technique. Presumptive Salmonella colonies were identified by phenotypic and 16S rRNA gene sequencing. The confirmed Salmonella isolates were tested for multidrug resistance by the Kirby Bauer disc diffusion test. Detection and confirmation of extended-spectrum beta-lactamase (ESBL) phenotypes were performed by double disc synergy and combination disc tests. PCR and DNA sequencing of the ESBL-encoding genes (bla SHV, bla TEM, and bla CTX-M) were also performed. The conserved and three-dimensional (3D) domains in ESBLs were respectively characterized by the reverse position-specific BLAST (RPS-BLAST) and Cn3D modeling tool. Of the 229 presumptive Salmonella isolates examined, 52 isolates were confirmed as Salmonella species, 46 isolates were multidrug-resistant and 41 isolates confirmed as multidrug-resistant ESBL-producing Salmonella species. The main serotypes were Salmonella enterica subsp. enterica serovar Typhimurium (35/52; 67.31%) and Salmonella enterica subsp. enterica serovar Enteritidis (17/52; 32.69%). Overall, the prevalence of chilled raw chicken meat contaminated with Salmonella was estimated at 0.17 (40/240). This value of prevalence exceeded the limits (≤ 0.1) set by the Meat Industry Guide, United Kingdom. All CTX-M, TEM, and SHV beta-lactamases produced by the Salmonella isolates were confirmed by RPS-BLAST and Cn3D modeling tool as serine-based hydrolases that consisted of two 3D domains with unique ligands such as sodium ion, formic acid, and glycerol. This study showed that multidrug-resistant ESBL-producing Salmonella was widespread in raw chicken meat vended in Nigerian markets. Thus, there is a need for relevant regulatory agencies to enforce safety.

Determination of Capsular Serotypes, Antibiotic Susceptibility Pattern, and Molecular Mechanism of Erythromycin Resistance among Clinical Isolates of Group B Streptococcus in Isfahan, Iran.

Background:Documented streptococcal resistance to erythromycin has recently been raised. The aim of this study is to identify the molecular mechanism of erythromycin resistance among group B Streptococcus (GBS) strains and to correlate with the clinical origin of strains.Materials and Methods:A total number of 134 colonizing (n = 36), invasive (n = 36), noninvasive (n = 46), and asymptomatic (n = 16) GBS isolates were characterized by the detection of dltS gene, capsular serotyping, antibiotic susceptibility profiles using disc diffusion method, and screening of the ermB, ermTR, and mefA resistance genes.Results:The distribution of capsular serotypes was as follow: serotype III (24.6%), Ia (21.6%), V (17.9%), Ib (14.9%), II (8.9%), IV (8.9%), VI (1.5%), and VII (1.5%). From 134 GBS isolates, 51 (38%) isolates were resistant to erythromycin. The constitutive macrolide lincosamide streptogrmin B (MLSB) was the most common resistance phenotype (62.7%), followed by inducible MLSB (27.4%) and M phenotype (9.8%). Erythromycin resistance rate was higher among asymptomatic GBS strains (13/16, 81.2%). Serotype III was the most prevalent type among resistant isolates (41.1%). The ermB gene highly distributed among resistant strains (64.7%), followed by ermTR (21.5%) and mefA (9.8%). The ermB gene was related to constitutive MLSB phenotype (84.3%, P < 0.05) and serotypes III (61.9%), Ib (87.5%), and V (83.3%). All M phenotype strains harbored mefA gene and were in association with serotype Ia (90%).Conclusion:The current study suggests that ribosomal modification with erm genes is the main mechanism of erythromycin resistance. Because of relatively high prevalence of erythromycin resistance, double disc test highly recommended for GBS disease treatment and intrapartum prophylaxis among penicillin intolerant patients in our region.

The Epidemiological Pattern and Risk Factor of ESBL (Extended Spectrum Β-Lactamase) Producing Enterobacteriaceae in Gut Bacterial Flora of Dairy Cows and People Surrounding in Rural Area, Indonesia

Livestock would be a risk factor of resistant bacteria that impact on human health. Rural area with farms as major economic source has become a risk of the spread of the ESBL producing Enterobacteriaceae The aim of the study was to explore the distribution and risk factor of ESBL (extended-spectrum β-lactamase) producing Enterobacteriaceae in the gut bacterial flora of dairy cows and people surrounding farming area. Total of 204 fecal swab samples were collected, 102 from dairy cows and 102 from farmers. Samples were sub-cultured by streaking on MacConkey agar supplemented with 2 mg/L cefotaxime. The growing colonies were confirmed of the ESBL producer by Modified Double Disk Test (M-DDST) and identification of Enterobacteriaceae by biochemical test. ESBL genes were identified by PCR. ESBL producing bacteria were found 13.7% in dairy cows and 34.3% in farmers. ESBL producing Enterobacteriaceae in dairy cows were 6.9% and in farmers of 33.3%. Statistical analysis showed: Distribution of ESBL producing Enterobacteriaceae strain were insignificant among dairy cows and farmers while blaTEM distribution was significantly different (p= 0,035) and use of antibiotic was identified as a risk factor of colonization of ESBL producing Enterobacteriaceae in farmers (p= 0,007). Farmers had suspected as the source of ESBL producing Enterobacteriaceae based on higher prevalence. Further education of appropriate use of antibiotic need to enhance to control risk factor and prevent the colonization of ESBL producing Enterobacteriaceae

Study on Wear Properties of J11 Wheel Steel with Nonuniform Microstructure

In actual wheel–rail systems, a nonuniform microstructure of the wheel and rail materials is a serious problem. A double-disk rolling wear test device was used to study the influence of the nonuniform microstructure on the wear properties of wheel materials in the present study. The results show that the microstructure of the sample 1 includes proeutectoid ferrite, pearlite, and upper bainite, which is a nonuniform microstructure. By contrast, the microstructure of sample 2 contains only proeutectoid ferrite and pearlite. During wear tests, with the increasing number of test cycles, the weight loss of the sample 1 is consistently larger than that of the sample 2. A similar trend is observed with respect to deformation of the plastic layer. For the sample 1, fatigue cracks mainly propagate along the interface between the upper bainite and pearlite, leading to rapid wear failure; the main wear mechanism changes from spalling to fatigue with the increasing number of cycles. For the sample 2, the main wear mechanism changes from adhesive wear to fatigue wear with increasing number of cycles.

Molecular diversity of Extended‐spectrum β‐lactamase‐producing Escherichia coli from vultures in Canary Islands

Antimicrobial resistance among isolates from wild animals is increasingly reported. Extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae, and particularly Escherichia coli, have spread worldwide as one of the most common multidrug-resistant organisms. The aim of this study was to determine the carriage rate of ESBL-producing E. coli isolates and their genetic characteristics in wild vultures from the Canary Islands. Faecal samples were collected from 22 apparently healthy free-ranging (wild) vulture chicks from Lanzarote and Fuerteventura (Canary Islands) during July 2019. They were seeded in MacConkey agar supplemented with cefotaxime (2 μg ml-1 ). Colonies with typical morphology of E. coli were identified by MALDI-TOF-MS. Antimicrobial susceptibility was done by disk diffusion. Phenotypic detection of ESBL was performed by double-disk tests. The presence of blaCTX-M , blaSHV , blaTEM , blaKPC and blaOXA-48 genes, as well as mcr-1 (colistin resistance), tetA/tetB and int1 gene, was tested by PCR/sequencing. Phylogenetic groups and multilocus sequence typing (MLST) were determined by PCR/sequencing. ESBL-producing E. coli isolates were detected in 5/22 tested animals (22.7%), and all isolates (one/animal) carried blaCTX-M genes: blaCTX-M-15 (n = 3) and blaCTX-M-55 (n = 2). ESBL-positive isolates were ascribed to phylogenetic group D (two isolates), B1 (two isolates) and A (one isolate), and five sequence types were detected (ST/phylogenetic-group/ESBL): ST515/B1/CTX-M-15, ST1290/A/CTX-M-15, ST38/D/CTX-M-15, ST457/D/CTX-M-55 and ST6448/B1 /CTX-M-55; this suggests a genetic diversity among these isolates. Three CTX-M-15-producing isolates contained the blaTEM gene and one the tetA gene. To our knowledge, this appears to be the first report of ESBL-producing E. coli in vulture chicks from the Canary Islands.

Characteristics of Extended-Spectrum β-Lactamase-Producing Escherichia coli From Dogs and Cats Admitted to a Veterinary Teaching Hospital in Taipei, Taiwan From 2014 to 2017.

Extended-spectrum β-lactamases (ESBLs) are enzymes that mediate resistance to newer β-lactam antibiotics, including extended-spectrum cephalosporins and monobactams. The production of ESBL is primarily plasmid mediated, and such plasmids often comprise the genes that encode resistance to other classes of antimicrobials, such as aminoglycosides and fluoroquinolones. Therefore, ESBL-producing microorganisms leave clinicians with limited therapeutic options in both human and veterinary medicine. Compared with human medicine, information regarding ESBL-producing microorganisms is limited in veterinary medicine. We screened for ESBL-producing Escherichia coli in dogs and cats admitted to National Taiwan University Veterinary Hospital, Taipei, from 2014 to 2017 and further analyzed the genotypes and phylogenetic traits of these ESBL producers. Double disk tests specified by the Clinical and Laboratory Standards Institute were performed on 283 E. coli isolates and revealed a total of 65 E. coli (54 from dogs and 11 from cats) with the ESBL phenotype (22.8%). blaCTX−M−1 group and blaCTX−M−2group were the most commonly identified ESBL gene groups. blaCTX−M−55 was the main ESBL gene within the blaCTX−M−1group, whereas the blaCTX−M−2group contained only blaCTX−M−124. The ESBL-producing E. coli were all resistant to ampicillin. The resistance rate to ceftiofur, doxycycline, enrofloxacin, and ciprofloxacin was 93.8, 73.8, 80, and 78.5%, respectively. Of the antibiotics tested, greater sensitivity to imipenem and gentamicin was noted. Multilocus sequence typing indicated that ST457, ST131, and ST648 were the most common sequence types. Our study identified eight ST131/O25b isolates, which is a global zoonotic clone of public health concern. The major ESBL genes of these clones were blaCTX−M−174 and blaCTX−M−194. Because companion animals such as dogs and cats are in close contact with humans, the characterization of ESBL producers originating from them is crucial from the perspective of both public health and veterinary medicine.

Características clínicas y microbiológicas de infecciones por Klebsiella pneumoniae productora de carbapenemasa MBL, tipo NDM, Hospital Geriátrico San Isidro Labrador EsSalud, 2018

Objective: To determine the clinical and microbiological characteristics of seven (7) cases of New Delhi MBL (NDM)producing Klebsiella pneumoniae nosocomial infections at the Hospital Geriatrico San Isidro Labrador (HG SIL) from February to May 2018. Materials and methods: A descriptive and retrospective study conducted in elderly people with urinary infections, pneumonia, sacral ulcers and surgical wound infection who received multiple non-protocolized antibiotic therapy. The methods used to detect MBLs in the Klebsiella pneumoniae isolates that showed decreased sensitivity to carbapenems were the phenylboronic acid-based (PBA) and ethylenediaminetetraacetic acid-based (EDTA) double disk tests. The identification of the NDM gene was performed by polymerase chain reaction at the Instituto Nacional de Salud. Results: In total, the seven cases were positive for the NDM gene and resistant to meropenem, which confirmed the epidemic outbreak. Mortality accounted for 28.6 % (2 of 7 patients) of the cases. However, due to the presence of comorbidities in all cases, the attributable mortality could not be determined. Conclusions: Labs have a key initial role for detecting and classifying the carbapenemases and the measures of comprehensive control of infections. The aforementioned cases are the first ones reported in our healthcare network.

Emerge of NDM-1-Producing Multidrug-Resistant Pseudomonas aeruginosa and Co-harboring of Carbapenemase Genes in South of Iran

New Delhi metallo-beta-lactamase-1 (NDM-1) is one of the most important emerging antibiotic resistance. Co-harboring three or four carbapenemases is rare and only a few reports exist in the literature. We described the characteristics of the large epidemic outbreaks and reports co-producing blaNDM-1 with the other carbapenemase genes in P. aeruginosa isolates. This present cross-sectional research was conducted on 369 P. aeruginosa isolates obtained from burn and general hospitals within years 2013 to 2016. Beta-lactamase classes A, B and D genes were identified by PCR method. Modified hodge test (MHT), double-disk potentiation tests (DDPT) and double disk synergy test (DDST) were performed for detection carbapenemase and metallo beta-lactamase (MBL) production of blaNDM-1 positive P. aeruginos isolates. From 236 carbapenem-resistant P. aeruginosa (CRPA), 116 isolates have had MBL genes and twenty-nine isolates were found positive for blaNDM-1 . In CRPA isolates, blaIMP-1 , blaVIM-2 and blaOXA-10 were identified in 27.5%, 21.1% and 32.2% of isolates respectively, while co-producing blaNDM-1 , blaIMP-1 , blaOXA-10 , co-producing blaNDM-1 , blaVIM-2 , blaOXA-10 and co-producing blaIMP-1 , blaVIM-2 were determined in 11 (4.6%), 8 (3.4%) and 27 (11.4%) of isolates respectively. The finding of this co-existence of multiple carbapenemase resistance genes is threating for public health. Dipicolinic acid is a superior MBL inhibitor in DDPT antique than EDTA in DDST method for the detection of MBL-blaNDM-1 producing P. aeruginosa.