Characterization of the Inlet Port Flow under Steady-State Conditions Using PIV and POD

The current study demonstrates an experimental investigation of the tumble flow structures using Particle Image Velocimetry (PIV) under steady-state conditions considering the central vertical tumble plane. The experiments were carried out on a four-valve, pent-roof Gasoline Direct Injection (GDI) engine head at different valve lifts and with a pressure difference of 150 mmH2O across the intake valves. Furthermore, the Proper Orthogonal Decomposition (POD) analytical technique was applied to PIV-measured velocity vector maps to characterize the flow structures at various valve lifts, and hence the different rig tumble values. The results show that at low valve lifts (1 to 5 mm), 48.9 to 46.6% of the flow energy is concentrated in the large (mode 1) eddies with only 8.4 to 11.46% in mode 2 and 7.2 to 7.5 in mode 3. At high valve lifts, it can be clearly seen that some of the energy in the large eddies of mode 1 is transferred to the smaller flow structures of modes 2 and 3. This can be clearly seen at valve lift 10 mm where the values of the flow energy were 40.6%, 17.3%, and 8.0% for modes 1, 2, and 3, respectively

Occurrence of Salmonella enterica and Escherichia coli in raw chicken and beef meat in northern Egypt and dissemination of their antibiotic resistance markers

Background The global incidence of foodborne infections and antibiotic resistance is recently increased and considered of public health concern. Currently, scarcely information is available on foodborne infections and ESBL associated with poultry and beef meat in Egypt. Methods In total, 180 chicken and beef meat samples as well as internal organs were collected from different districts in northern Egypt. The samples were investigated for the prevalence and antibiotic resistance of Salmonella enterica serovars and Escherichia coli. All isolates were investigated for harbouring class 1 and class 2 integrons. Results Out of 180 investigated samples 15 S. enterica (8.3%) and 21 E. coli (11.7%) were isolated and identified. S. enterica isolates were typed as 9 S. Typhimurium (60.0%), 3 S. Paratyphi A (20.0%), 2 S. Enteritidis (13.3%) and 1 S. Kentucky (6.7%). Twenty-one E. coli isolates were serotyped into O1, O18, O20, O78, O103, O119, O126, O145, O146 and O158. The phenotypic antibiotic resistance profiles of S. enterica serovars to ampicillin, cefotaxime, cefpodoxime, trimethoprim/sulphamethoxazole and tetracycline were 86.7, 80.0, 60.0, 53.3 and 40.0%, respectively. Isolated E. coli were resistant to tetracycline (80.9%), ampicillin (71.4%), streptomycin, trimethoprim/sulphamethoxazole (61.9% for each) and cefotaxime (33.3%). The dissemination of genes coding for ESBL and AmpC β-lactamase in S. enterica isolates included bla CTX-M (73.3%), bla TEM (73.3%) and bla CMY (13.3%). In E. coli isolates bla TEM, bla CTX-M and bla OXA were identified in 52.4, 42.9 and 14.3%, respectively. The plasmid-mediated quinolone resistance genes identified in S. enterica were qnrA (33.3%), qnrB (20.0%) and qnrS (6.7%) while qnrA and qnrB were detected in 33.3% of E. coli isolates. Class 1 integron was detected in 13.3% of S. enterica and in 14.3% of E. coli isolates. Class 2 integron as well as the colistin resistance gene mcr-1 was not found in any of E. coli or S. enterica isolates. Conclusions This study showed high prevalence of S. enterica and E. coli as foodborne pathogens in raw chicken and beef meat in Nile Delta, Egypt. The emergence of antimicrobial resistance in S. enterica and E. coli isolates is of public health concern in Egypt. Molecular biological investigation elucidated the presence of genes associated with antibiotic resistance as well as class 1 integron in S. enterica and E. coli

Epidemiological, molecular characterization and antibiotic resistance of Salmonella enterica serovars isolated from chicken farms in Egypt

Background Salmonella is one of major causes of foodborne outbreaks globally. This study was conducted to estimate the prevalence, typing and antibiotic susceptibilities of Salmonella enterica serovars isolated from 41 broiler chicken farms located in Kafr El-Sheikh Province in Northern Egypt during 2014–2015. The clinical signs and mortalities were observed. Results In total 615 clinical samples were collected from broiler flocks from different organs (liver, intestinal content and gall bladder). Salmonella infection was identified in 17 (41%) broiler chicken flocks and 67 Salmonella isolates were collected. Recovered isolates were serotyped as 58 (86.6%) S. enterica serovar Typhimurium, 6 (9%) S. enterica serovar Enteritidis and 3 (4.5%) were non- typable. The significant high mortality rate was observed only in 1-week-old chicks. sopE gene was detected in 92.5% of the isolates which indicating their ability to infect humans. All S. enterica serovar Enteritidis isolates were susceptible to all tested antimicrobials. The phenotypically resistant S. enterica serovar Typhimurium isolates against ampicillin, tetracycline, sulphamethoxazole and chloramphenicol were harbouring BlaTEM, (tetA and tetC), (sul1 and sul3) and (cat1 and floR), respectively. The sensitivity rate of S. enterica serovar Typhimurium to gentamycin, trimethoprim/sulphamethoxazole and streptomycin were 100, 94.8, 89.7%, respectively. The silent streptomycin antimicrobial cassettes were detected in all Salmonella serovars. A class one integron (dfrA12, orfF and aadA2) was identified in three of S. enterica serovar Typhimurium strains. Conclusions To the best of our knowledge, this study considered first report discussing the prevalence, genotyping, antibiotic susceptibility and public health significance of S. enterica serovars in broilers farms of different ages in Delta Egypt. Further studies are mandatory to verify the location of some resistance genes that are within or associated with the class one integron

Genomic insight into Campylobacter jejuni isolated from commercial turkey flocks in Germany using whole-genome sequencing analysis

Campylobacter (C.) jejuni is a zoonotic bacterium of public health significance. The present investigation was designed to assess the epidemiology and genetic heterogeneity of C. jejuni recovered from commercial turkey farms in Germany using whole-genome sequencing. The Illumina MiSeq® technology was used to sequence 66 C. jejuni isolates obtained between 2010 and 2011 from commercial meat turkey flocks located in ten German federal states. Phenotypic antimicrobial resistance was determined. Phylogeny, resistome, plasmidome and virulome profiles were analyzed using whole-genome sequencing data. Genetic resistance markers were identified with bioinformatics tools (AMRFinder, ResFinder, NCBI and ABRicate) and compared with the phenotypic antimicrobial resistance. The isolates were assigned to 28 different sequence types and 11 clonal complexes. The average pairwise single nucleotide-polymorphisms distance of 14,585 SNPs (range: 0–26,540 SNPs) revealed a high genetic distinction between the isolates. Thirteen virulence-associated genes were identified in C. jejuni isolates. Most of the isolates harbored the genes flaA (83.3%) and flaB (78.8%). The wlaN gene associated with the Guillain–Barré syndrome was detected in nine (13.6%) isolates. The genes for resistance to ampicillin (blaOXA), tetracycline [tet(O)], neomycin [aph(3')-IIIa], streptomycin (aadE) and streptothricin (sat4) were detected in isolated C. jejuni using WGS. A gene cluster comprising the genes sat4, aph(3′)-IIIa and aadE was present in six isolates. The single point mutation T86I in the housekeeping gene gyrA conferring resistance to quinolones was retrieved in 93.6% of phenotypically fluoroquinolone-resistant isolates. Five phenotypically erythromycin-susceptible isolates carried the mutation A103V in the gene for the ribosomal protein L22 inferring macrolide resistance. An assortment of 13 β-lactam resistance genes (blaOXA variants) was detected in 58 C. jejuni isolates. Out of 66 sequenced isolates, 28 (42.4%) carried plasmid-borne contigs. Six isolates harbored a pTet-like plasmid-borne contig which carries the tet(O) gene. This study emphasized the potential of whole-genome sequencing to ameliorate the routine surveillance of C. jejuni. Whole-genome sequencing can predict antimicrobial resistance with a high degree of accuracy. However, resistance gene databases need curation and updates to revoke inaccuracy when using WGS-based analysis pipelines for AMR detection

Evolution of Antibiotic Resistance of Coagulase-Negative Staphylococci Isolated from Healthy Turkeys in Egypt: First Report of Linezolid Resistance

Coagulase-negative staphylococci (CoNS) are gaining much attention as causative agents of serious nosocomial infections in humans. This study aimed to determine the prevalence and phenotypic antimicrobial resistance of CoNS as well as the presence of resistance-associated genes in CoNS isolated from turkey farms in Egypt. Two hundred and fifty cloacal swabs were collected from apparently healthy turkeys in Egypt. Suspected isolates were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The susceptibility testing of CoNS isolates against 20 antimicrobial agents was performed using the broth microdilution test. The presence of resistance-associated genes like mecA, vanA, blaZ, erm(A), erm(B), erm(C), aac-aphD, optrA, valS, and cfr was determined. Thirty-nine CoNS were identified. All isolates were phenotypically resistant to trimethoprim/sulfamethoxazole, penicillin, ampicillin, and tetracycline. The resistance rates to erythromycin, chloramphenicol, oxacillin, daptomycin, and tigecycline were 97.4%, 94.9%, 92.3%, 89.7%, and 87.2%, respectively. Thirty-one isolates were resistant to linezolid (79.5%). Low resistance rate was detected for both imipenem and vancomycin (12.8%). The erm(C) gene was identified in all erythromycin phenotypically resistant isolates, whereas two resistant isolates possessed three resistance-conferring genes erm(A), erm(B), and erm(C). The cfr and optrA genes were detected in 11 (35.5%) and 12 (38.7%) of the 31 linezolid-resistant isolates. The mecA, aac-aphD, and blaZ genes were identified in 22.2%, 41.9%, and 2.6% of phenotypically resistant isolates to oxacillin, gentamicin, and penicillin, respectively. This is the first study revealing the correlation between linezolid resistance and presence of cfr and optrA genes in CoNS isolates from Egypt, and it can help to improve knowledge about the linezolid resistance mechanism

Effect of Boost Pressure on the In-Cylinder Tumble-Motion of GDI Engine under Steady-State Conditions using Stereoscopic-PIV

This paper experimentally investigates the effect of boost pressure on the in-cylinder flow field under steady-state conditions using stereoscopic particle image velocimetry (Stereo-PIV) through increasing the pressure difference across the intake valves. The FEV steady-state flow bench was modified to provide an optical access into the cylinder region. The stereoscopic PIV measurements were carried out at various pressure differences viz., 300, 450, and 600 mmH2O across the intake valves of Gasoline Direct Injection (GDI) head for the mid cylinder vertical tumble-plane. Ensemble average velocity vectors were used to characterize the tumble flow structure and for the calculation of tumble ratio and average turbulent kinetic energy. Moreover, the Proper Orthogonal Decomposition (POD) technique was conducted on the PIV measured velocity vector maps to identify the most energetic structures generated at different valve lifts and pressure differences. The results of stereoscopic PIV measurements showed that the overall in-cylinder flow structures were mainly dependent on the valve lift irrespective of the applied pressure difference. However, the level of the turbulence kinetic energy increased as the boost pressure increased

Effect of boost pressure on the in-cylinder tumble- motion of GDI engine under steady-state conditions using Stereoscopic-PIV

This paper experimentally investigates the effect of boost pressure on the in-cylinder flow field under steady-state conditions using stereoscopic particle image velocimetry (Stereo-PIV) through increasing the pressure difference across the intake valves. The FEV steady-state flow bench was modified to provide an optical access into the cylinder region. The stereoscopic PIV measurements were carried out at various pressure differences viz., 300, 450, and 600 mmH2O across the intake valves of Gasoline Direct Injection (GDI) head for the mid cylinder vertical tumble-plane. Ensemble average velocity vectors were used to characterize the tumble flow structure and for the calculation of tumble ratio and average turbulent kinetic energy. Moreover, the Proper Orthogonal Decomposition (POD) technique was conducted on the PIV measured velocity vector maps to identify the most energetic structures generated at different valve lifts and pressure differences. The results of stereoscopic PIV measurements showed that the overall in-cylinder flow structures were mainly dependent on the valve lift irrespective of the applied pressure difference. However, the level of the turbulence kinetic energy increased as the boost pressure increased

Antimicrobial resistance of Campylobacter isolates from small scale and backyard chicken in Kenya

Background Thermophilic Campylobacter species are a major cause of bacterial foodborne diarrhoea in humans worldwide. Poultry and their products are the predominant source for human campylobacteriosis. Resistance of Campylobacter to antibiotics is increasing worldwide, but little is known about the antibiotic resistance in Campylobacter isolated from chicken in Kenya. In this study, 35 suspected Campylobacter strains isolated from faeces and cloacal swabs of chicken were tested for their susceptibility to seven antibiotics using a broth microdilution assay and molecular biological investigations. Results Overall, DNA of thermophilic Campylobacter was identified in 53 samples by PCR (34 C. jejuni, 18 C. coli and one mix of both species) but only 35 Campylobacter isolates (31 C. jejuni and 4 C. coli) could be re-cultivated after transportation to Germany. Isolates were tested for their susceptibility to antibiotics using a broth microdilution assay. Additionally, molecular biological detection of antibiotic resistance genes was carried out. C. jejuni isolates showed a high rate of resistance to nalidixic acid, tetracycline and ciprofloxacin of 77.4, 71.0 and 71.0 %, respectively. Low resistance (25.8 %) was detected for gentamicin and chloramphenicol. Multidrug resistance in C. jejuni could be detected in 19 (61.3 %) isolates. Resistance pattern of C. coli isolates was comparable. Resistance to ciprofloxacin was confirmed by MAMA–PCR and PCR–RFLP in all phenotypically resistant isolates. The tet(O) gene was detected only in 54.5 % of tetracycline resistant C. jejuni isolates. The tet(A) gene, which is also responsible for tetracycline resistance, was found in 90.3 % of C. jejuni and in all C. coli isolates. Thirteen phenotypically erythromycin-resistant isolates could not be characterised by using PCR–RFLP and MAMA–PCR. Conclusions To the best of our knowledge, this study is the first report about resistance to antibiotics in thermophilic Campylobacter originating from chicken in Kenya. Campylobacter spp. show a high level of resistance to ciprofloxacin, nalidixic acid and tetracycline but also a remarkable one to chloramphenicol and gentamicin and they are multidrug resistant. Resistance to antibiotics is a global public health concern. In Kenya, resistance surveillance needs further attention in the future. Efforts to establish at least a National Laboratory with facilities for performing phenotypic and genotypic characterization of thermophilic Campylobacter is highly recommended