Pathogenomes of Shiga Toxin Positive and Negative Escherichia coli O157:H7 Strains TT12A and TT12B: Comprehensive Phylogenomic Analysis Using Closed Genomes.

Shiga toxin-producing Escherichia coli are zoonotic pathogens that cause food-borne human disease. Among these, the O157:H7 serotype has evolved from an enteropathogenic O55:H7 ancestor through the displacement of the somatic gene cluster and recurrent toxigenic conversion by Shiga toxin-converting bacteriophages. However, atypical strains that lack the Shiga toxin, the characteristic virulence hallmark, are circulating in this lineage. For this study, we analyzed the pathogenome and virulence inventories of the stx+ strain, TT12A, isolated from a patient with hemorrhagic colitis, and its respective co-isolated stx- strain, TT12B. Sequencing the genomes to closure proved critical to the cataloguing of subtle strain differentiating sequence and structural polymorphisms at a high-level of phylogenetic accuracy and resolution. Phylogenomic profiling revealed SNP and MLST profiles similar to the near clonal outbreak isolates. Their prophage inventories, however, were notably different. The attenuated atypical non-shigatoxigenic status of TT12B is explained by the absence of both the ΦStx1a- and ΦStx2a-prophages carried by TT12A, and we also recorded further alterations in the non-Stx prophage complement. Phenotypic characterization indicated that culture growth was directly impacted by the strains' distinct lytic phage complement. Altogether, our phylogenomic and phenotypic analyses show that these intimately related isogenic strains are on divergent Stx(+/stx-) evolutionary paths.

Pathogenomes and virulence profiles of representative big six non-O157 serogroup Shiga toxin-producing Escherichia coli.

Shiga toxin (Stx)-producing Escherichia coli (STEC) of non-O157:H7 serotypes are responsible for global and widespread human food-borne disease. Among these serogroups, O26, O45, O103, O111, O121, and O145 account for the majority of clinical infections and are colloquially referred to as the "Big Six." The "Big Six" strain panel we sequenced and analyzed in this study are reference type cultures comprised of six strains representing each of the non-O157 STEC serogroups curated and distributed by the American Type Culture Collection (ATCC) as a resource to the research community under panel number ATCC MP-9. The application of long- and short-read hybrid sequencing yielded closed chromosomes and a total of 14 plasmids of diverse functions. Through high-resolution comparative phylogenomics, we cataloged the shared and strain-specific virulence and resistance gene content and established the close relationship of serogroup O26 and O103 strains featuring flagellar H-type 11. Virulence phenotyping revealed statistically significant differences in the Stx-production capabilities that we found to be correlated to the strain's individual stx-status. Among the carried Stx1a, Stx2a, and Stx2d phages, the Stx2a phage is by far the most responsive upon RecA-mediated phage mobilization, and in consequence, stx2a + isolates produced the highest-level of toxin in this panel. The availability of high-quality closed genomes for this "Big Six" reference set, including carried plasmids, along with the recorded genomic virulence profiles and Stx-production phenotypes will provide a valuable foundation to further explore the plasticity in evolutionary trajectories in these emerging non-O157 STEC lineages, which are major culprits of human food-borne disease.

Modular Knee Arthrodesis as Definitive Treatment for Periprosthetic Infection, Bone Loss, and Failure of the Extensor Mechanism After Total Knee Arthroplasty.

Background: Periprosthetic joint infection (PJI) after total knee arthroplasty (TKA) can result in bone and soft-tissue loss, leg length discrepancies, and dysfunctional extensor mechanisms. While above-knee amputation (AKA) is an established salvage treatment, modular knee arthrodesis (MKA) is a viable option that provides rigid stability and maintains leg length even in patients with severe bone and soft-tissue loss. We sought to report the outcomes of patients with an MKA as the definitive treatment. Methods: We retrospectively reviewed 8 patients implanted with an MKA at 2 institutions between 2016 and 2022. The mean age was 69.63 years, and 50.0% of patients were women. All patients were indicated for conversion to an MKA as the definitive treatment in the setting of treated chronic PJI after TKA, severe bone loss, and failure of the extensor mechanism not amenable to repair. Medical records and radiographs were reviewed. Results: No patients required incision and drainage or exchange of their MKA for PJI at mean 2-year follow-up. One patient required 2 revisions for mechanical failure of his implant at 5.0 and 6.4 years postoperatively. Conclusions: MKA is a viable permanent alternative to AKA for patients with treated chronic PJI and dysfunctional extensor mechanism after TKA. The procedure restores leg lengths in the setting of severe bone and soft-tissue loss, therefore allowing patients to ambulate independently. Still, surgeons should be aware of the potential for mechanical failure requiring revision.

Genomic and Phenotypic Characterization of Shiga Toxin-Producing Escherichia albertii Strains Isolated from Wild Birds in a Major Agricultural Region in California.

Escherichia albertii is an emerging foodborne pathogen. To better understand the pathogenesis and health risk of this pathogen, comparative genomics and phenotypic characterization were applied to assess the pathogenicity potential of E. albertii strains isolated from wild birds in a major agricultural region in California. Shiga toxin genes stx2f were present in all avian strains. Pangenome analyses of 20 complete genomes revealed a total of 11,249 genes, of which nearly 80% were accessory genes. Both core gene-based phylogenetic and accessory gene-based relatedness analyses consistently grouped the three stx2f-positive clinical strains with the five avian strains carrying ST7971. Among the three Stx2f-converting prophage integration sites identified, ssrA was the most common one. Besides the locus of enterocyte effacement and type three secretion system, the high pathogenicity island, OI-122, and type six secretion systems were identified. Substantial strain variation in virulence gene repertoire, Shiga toxin production, and cytotoxicity were revealed. Six avian strains exhibited significantly higher cytotoxicity than that of stx2f-positive E. coli, and three of them exhibited a comparable level of cytotoxicity with that of enterohemorrhagic E. coli outbreak strains, suggesting that wild birds could serve as a reservoir of E. albertii strains with great potential to cause severe diseases in humans.

The Reverse Fragility Index: Interpreting the Current Literature on Long-Term Survivorship of Computer-Navigated Versus Conventional TKA: A Systematic Review and Cross-Sectional Study of Randomized Controlled Trials.

BACKGROUND: Despite the most recent American Academy of Orthopaedic Surgeons clinical practice guideline making a "strong" recommendation against the use of intraoperative navigation in total knee arthroplasty (TKA), its use is increasing. We utilized the concept of the reverse fragility index (RFI) to assess the strength of neutrality of the randomized controlled trials (RCTs) comparing the long-term survivorship of computer-navigated and conventional TKA. METHODS: A systematic review was performed including all RCTs through August 3, 2021, comparing the long-term outcomes of computer-navigated and conventional TKA. Randomized trials with mean follow-up of >8 years and survivorship with revision as the end point were included. The RFI quantifies the strength of a study's neutrality by calculating the minimum number of events necessary to flip the result from nonsignificant to significant. The RFI at a threshold of p < 0.05 was calculated for each study reporting nonsignificant results. The reverse fragility quotient (RFQ) was calculated by dividing the RFI by the study sample size. RESULTS: Ten clinical trials with 2,518 patients and 38 all-cause revisions were analyzed. All 10 studies reported nonsignificant results. The median RFI at the p < 0.05 threshold was 4, meaning that a median of 4 events would be needed to change the results from nonsignificant to significant. The median RFQ was 0.029, indicating that the nonsignificance of the results was contingent on only 2.9 events per 100 participants. The median loss to follow-up was 27 patients. In all studies, the number of patients lost to follow-up was greater than the RFI. CONCLUSIONS: The equipoise in long-term survivorship between computer-navigated and conventional TKA rests on fragile studies, as their statistical nonsignificance could be reversed by changing the outcome status of only a handful of patients--a number that was always smaller than the number lost to follow-up. Routine reporting of the RFI in trials with nonsignificant findings may provide readers with a measure of confidence in the neutrality of the results. LEVEL OF EVIDENCE: Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Escherichia coli O157:H7 tir 255 T > A allele strains differ in chromosomal and plasmid composition.

Shiga toxin-producing Escherichia coli (STEC) O157:H7 strains with the T allele in the translocated intimin receptor polymorphism (tir) 255 A > T gene associate with human disease more than strains with an A allele; however, the allele is not thought to be the direct cause of this difference. We sequenced a diverse set of STEC O157:H7 strains (26% A allele, 74% T allele) to identify linked differences that might underlie disease association. The average chromosome and pO157 plasmid size and gene content were significantly greater within the tir 255 A allele strains. Eighteen coding sequences were unique to tir 255 A allele chromosomes, and three were unique to tir 255 T allele chromosomes. There also were non-pO157 plasmids that were unique to each tir 255 allele variant. The overall average number of prophages did not differ between tir 255 allele strains; however, there were different types between the strains. Genomic and mobile element variation linked to the tir 255 polymorphism may account for the increased frequency of the T allele isolates in human disease.

Whole genome sequencing of Moraxella bovis strains from North America reveals two genotypes with different genetic determinants.

BACKGROUND: Moraxella bovis and Moraxella bovoculi both associate with infectious bovine keratoconjunctivitis (IBK), an economically significant and painful ocular disease that affects cattle worldwide. There are two genotypes of M. bovoculi (genotypes 1 and 2) that differ in their gene content and potential virulence factors, although neither have been experimentally shown to cause IBK. M. bovis is a causative IBK agent, however, not all strains carry a complete assortment of known virulence factors. The goals of this study were to determine the population structure and depth of M. bovis genomic diversity, and to compare core and accessory genes and predicted outer membrane protein profiles both within and between M. bovis and M. bovoculi. RESULTS: Phylogenetic trees and bioinformatic analyses of 36 M. bovis chromosomes sequenced in this study and additional available chromosomes of M. bovis and both genotype 1 and 2 M. bovoculi, showed there are two genotypes (1 and 2) of M. bovis. The two M. bovis genotypes share a core of 2015 genes, with 121 and 186 genes specific to genotype 1 and 2, respectively. The two genotypes differ by their chromosome size and prophage content, encoded protein variants of the virulence factor hemolysin, and by their affiliation with different plasmids. Eight plasmid types were identified in this study, with types 1 and 6 observed in 88 and 56% of genotype 2 strains, respectively, and absent from genotype 1 strains. Only type 1 plasmids contained one or two gene copies encoding filamentous haemagglutinin-like proteins potentially involved with adhesion. A core of 1403 genes was shared between the genotype 1 and 2 strains of both M. bovis and M. bovoculi, which encoded a total of nine predicted outer membrane proteins. CONCLUSIONS: There are two genotypes of M. bovis that differ in both chromosome content and plasmid profiles and thus may not equally associate with IBK. Immunological reagents specifically targeting select genotypes of M. bovis, or all genotypes of M. bovis and M. bovoculi together could be designed from the outer membrane proteins identified in this study.

Comparative Genomics of Escherichia coli Serotype O55:H7 Using Complete Closed Genomes.

Escherichia coli O55:H7 is a human foodborne pathogen and is recognized as the progenitor strain of E. coli O157:H7. While this strain is important from a food safety and genomic evolution standpoint, much of the genomic diversity of E. coli O55:H7 has been demonstrated using draft genomes. Here, we combine the four publicly available E. coli O55:H7 closed genomes with six newly sequenced closed genomes to provide context to this strain's genomic diversity. We found significant diversity within the 10 E. coli O55:H7 strains that belonged to three different sequence types. The prophage content was about 10% of the genome, with three prophages common to all strains and seven unique to one strain. Overall, there were 492 insertion sequences identified within the six new sequence strains, with each strain on average containing 75 insertions (range 55 to 114). A total of 31 plasmids were identified between all isolates (range 1 to 6), with one plasmid (pO55) having an identical phylogenetic tree as the chromosome. The release and comparison of these closed genomes provides new insight into E. coli O55:H7 diversity and its ability to cause disease in humans.

Continuous Femoral Nerve Block Reduces the Need for Manipulation Following Total Knee Arthroplasty.

Peripheral nerve blocks improve both pain control and functional outcomes following total knee arthroplasty (TKA). However, few studies have examined the effects of different peripheral nerve block protocols on postoperative range of motion. The present study assessed the impact of a single-shot femoral nerve block (SFNB) versus continuous femoral nerve block (CFNB) on postoperative range of motion and the need for subsequent manipulation following TKA. Methods: We retrospective reviewed patient charts to identify patients who had undergone primary elective unilateral TKA by 2 surgeons at a high-volume orthopaedic specialty hospital over a 3-year period. A total of 1,091 patients received either SFNB or CFNB and were included in the data analysis. Identical surgical techniques, postoperative oral analgesic regimens, and rehabilitation protocols were used for all patients. Patients with <90° of flexion at 6 weeks postoperatively underwent closed manipulation under anesthesia (MUA). Results: Overall, 608 patients (55.7%) received CFNB and 483 patients (44.3%) received SFNB. Overall, 94 patients (8.6%) required postoperative manipulation for stiffness, including 36 (5.9%) in the CFNB group and 58 (12%) in the SFNB group. The 50% reduction in the need for manipulation in the CFNB group was independent of primary surgeon (p > 0.05). No significant differences were observed between the groups in terms of postoperative range of motion, either at the time of discharge or at 6 weeks postoperatively. A history of knee surgery, decreased preoperative range of motion, and decreased range of motion at the time of discharge were significantly associated with the need for further MUA (p = 0.0002, p < 0.0001, and p < 0.0001, respectively). Conclusions: Despite similar final postoperative range of motion between patients in both groups, our results suggest that CFNB may be superior to SFNB for reducing the need for postoperative manipulation after primary TKA. Furthermore, a history of ipsilateral knee surgery, decreased preoperative range of motion, and decreased range of motion at the time of discharge were identified as independent risk factors for postoperative stiffness requiring MUA after primary TKA. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Whole-genome sequencing analysis of Shiga toxin-producing Escherichia coli O22:H8 isolated from cattle prediction pathogenesis and colonization factors and position in STEC universe phylogeny.

Shiga toxin-producing Escherichia coli (STEC) is a foodborne pathogen capable of causing illness in humans. In a previous study, our group showed that a STEC isolate belonging to O22:H8 serotype (strain 154) can interfere with STEC O157:H7 colonization both in vitro and in vivo. Using whole-genome sequencing and genomic comparative, we predicted a subset of genes acquired by O22:H8 strain 154 through horizontal gene transfer that might be responsible for the phenotype previously described by our group. Among them were identified genes related to the pathogenesis of non-LEE (locus of enterocyte effacement) STEC, specific metabolic processes, antibiotic resistance and genes encoding for the T6SS-1 that is related to inter-bacterial competition. In addition, we showed that this strain carries stx1c and stx2dact, a mucus-inducible variant. The results obtained in this study provide insights into STEC genomic plasticity and the importance of genomic islands in the adaptation and pathogenesis of this pathogen.

Rates of evolutionary change of resident Escherichia coli O157:H7 differ within the same ecological niche.

BACKGROUND: Shiga toxin-producing Escherichia coli (STEC) O157:H7 is a pathogen known to reside in cattle feedlots. This retrospective study examined 181 STEC O157:H7 strains collected over 23 years from a closed-system feedlot. All strains were subjected to short-read sequencing, with a subset of 36 also subjected to long-read sequencing. RESULTS: Over 96% of the strains fell into four phylogenetically distinct clades. Clade membership was associated with multiple factors including stx composition and the alleles of a well-characterized polymorphism (tir 255 T > A). Small plasmids (2.7 to 40 kb) were found to be primarily clade specific. Within each clade, chromosomal rearrangements were observed along with a core phageome and clade specific phages. Across both core and mobile elements of the genome, multiple SNP alleles were in complete linkage disequilibrium across all strains within specific clades. Clade evolutionary rates varied between 0.9 and 2.8 SNP/genome/year with two tir A allele clades having the lowest evolutionary rates. Investigation into possible causes of the differing rates was not conclusive but revealed a synonymous based mutation in the DNA polymerase III of the fastest evolving clade. Phylogenetic trees generated through our bioinformatic pipeline versus the NCBI's pathogen detection project were similar, with the two tir A allele clades matching individual NCBI SNP clusters, and the two tir T allele clades assigned to multiple closely-related SNP clusters. CONCLUSIONS: In one ecological niche, a diverse STEC O157:H7 population exhibited different rates of evolution that associated with SNP alleles in linkage disequilibrium in the core genome and mobile elements, including tir 255 T > A.

Reducing Narcotic Usage With 0.5% Bupivacaine Periarticular Injections in Total Knee Arthroplasty.

BACKGROUND: Periarticular injections (PAIs) and adductor canal blocks (ACBs) are widely accepted pain management strategies for total knee arthroplasty (TKA); however, the optimal anesthetic concentration to provide adequate pain relief while avoiding toxicity remains controversial. The purpose of this study is to evaluate the efficacy of different anesthetic concentrations for PAI alone and in combination with ACB. METHODS: This retrospective cohort study of patients undergoing primary TKAs between January 2019 and November 2020 included 3 groups: 0.25% PAI (50 cc of 0.25% bupivacaine PAI diluted with 50 cc of saline and ketorolac), 0.5% PAI (50 cc of 0.5% bupivacaine with 50 cc of saline and ketorolac), and PAI + ACB (ultrasound-guided preoperative anesthesiologist-administered ACB and 0.25% PAI). RESULTS: In total, 368 TKAs were analyzed (123 0.25%, 132 0.5%, and 113 PAI + ACB). Total overall hospital narcotic usage in oral morphine equivalents (OME) was significantly lower for the 0.5% group (120.09 vs 165.26 and 175.75) compared to the 0.25% and PAI + ACB groups, respectively (P < .0001). Cumulative OME for the first 3 shifts was also lower for 0.5% (68.7 vs 83.7 and 76.4) compared to the 0.25% and PAI + ACB groups, respectively (P = .030). Total postoperative narcotics in OME were significantly lower for 0.5% (617.9 vs 825.2 and 1047.6) than 0.25% and PAI + ACB, respectively (P = .0003). Number of prescriptions within 6 weeks postoperatively were also significantly lower for 0.5% (1.7) than 0.25% (2.1) and PAI + ACB (2.4) (P = .0003). CONCLUSION: Patients receiving 0.5% PAI had lower narcotic usage compared to 0.25% PAI or PAI + ACB. ACB may be eliminated without compromising pain control if the dose of local anesthetic in the PAI is sufficiently high.

Reduction in Interfacility Transfer Response Time after Implementation of an AutoLaunch Protocol.

Background: Interfacility transfers (IFTs) are an essential component of healthcare systems to allow movement of patients between facilities. It is essential to limit any delays in patients receiving the care they require at the receiving facility. The primary objective of this study was to assess whether IFT response time was reduced after implementation of an AutoLaunch protocol, in which an ambulance is dispatched to the sending facility prior to acceptance of the patient by the receiving facility. The secondary objective was to describe the frequency and amount of time ambulances had to stage outside the sending facility in situations where the ambulance arrived prior to the patient being accepted by the receiving facility. Methods: This was a retrospective pre-post analysis of patients undergoing IFT for services not available at the sending facility between October 1, 2018 and September 30, 2019, with the AutoLaunch protocol being implemented on March 25, 2019. IFT response time was defined as the time the transfer request was initially made to the time the ambulance arrived at the sending facility. Dispatch call logs and transport records were analyzed before and after implementation of the AutoLaunch protocol to assess for a difference in IFT response time as well as frequency and amount of time ambulances had to stage. Results: Of 1,881 IFTs analyzed, 885 (47.0%) were completed under the traditional protocol and 996 (53.0%) were completed under the AutoLaunch protocol. The median IFT response time under the traditional protocol was 27.5 minutes (interquartile range (IQR): 17.9, 43.3), compared with 19.9 minutes (IQR: 12.8, 28.2) under the AutoLaunch protocol (p < 0.01), representing a 27.6% reduction in response time, or 7.6 minutes saved. Of the 996 AutoLaunch transfers, there were 215 incidents (21.6%) in which the IFT ambulance had to stage, and the median staging time was 10.1 minutes (IQR: 4.9, 24.2). Conclusions: Implementation of our AutoLaunch protocol resulted in a significant reduction in ambulance response time for interfacility transfers. Further studies are needed to assess whether the reduction in response time is associated with improved patient outcomes for certain conditions.

Genome structural variation in Escherichia coli O157:H7.

The human zoonotic pathogen Escherichia coli O157:H7 is defined by its extensive prophage repertoire including those that encode Shiga toxin, the factor responsible for inducing life-threatening pathology in humans. As well as introducing genes that can contribute to the virulence of a strain, prophage can enable the generation of large-chromosomal rearrangements (LCRs) by homologous recombination. This work examines the types and frequencies of LCRs across the major lineages of the O157:H7 serotype. We demonstrate that LCRs are a major source of genomic variation across all lineages of E. coli O157:H7 and by using both optical mapping and Oxford Nanopore long-read sequencing prove that LCRs are generated in laboratory cultures started from a single colony and that these variants can be recovered from colonized cattle. LCRs are biased towards the terminus region of the genome and are bounded by specific prophages that share large regions of sequence homology associated with the recombinational activity. RNA transcriptional profiling and phenotyping of specific structural variants indicated that important virulence phenotypes such as Shiga-toxin production, type-3 secretion and motility can be affected by LCRs. In summary, E. coli O157:H7 has acquired multiple prophage regions over time that act to continually produce structural variants of the genome. These findings raise important questions about the significance of this prophage-mediated genome contingency to enhance adaptability between environments.

Genomic analysis of shiga toxin-containing Escherichia coli O157:H7 isolated from Argentinean cattle.

Cattle are the main reservoir of Enterohemorrhagic Escherichia coli (EHEC), with O157:H7 the distinctive serotype. EHEC is the main causative agent of a severe systemic disease, Hemolytic Uremic Syndrome (HUS). Argentina has the highest pediatric HUS incidence worldwide with 12-14 cases per 100,000 children. Herein, we assessed the genomes of EHEC O157:H7 isolates recovered from cattle in the humid Pampas of Argentina. According to phylogenetic studies, EHEC O157 can be divided into clades. Clade 8 strains that were classified as hypervirulent. Most of the strains of this clade have a Shiga toxin stx2a-stx2c genotype. To better understand the molecular bases related to virulence, pathogenicity and evolution of EHEC O157:H7, we performed a comparative genomic analysis of these isolates through whole genome sequencing. The isolates classified as clade 8 (four strains) and clade 6 (four strains) contained 13 to 16 lambdoid prophages per genome, and the observed variability of prophages was analysed. An inter strain comparison show that while some prophages are highly related and can be grouped into families, other are unique. Prophages encoding for stx2a were highly diverse, while those encoding for stx2c were conserved. A cluster of genes exclusively found in clade 8 contained 13 genes that mostly encoded for DNA binding proteins. In the studied strains, polymorphisms in Q antiterminator, the Q-stx2A intergenic region and the O and P γ alleles of prophage replication proteins are associated with different levels of Stx2a production. As expected, all strains had the pO157 plasmid that was highly conserved, although one strain displayed a transposon interruption in the protease EspP gene. This genomic analysis may contribute to the understanding of the genetic basis of the hypervirulence of EHEC O157:H7 strains circulating in Argentine cattle. This work aligns with other studies of O157 strain variation in other populations that shows key differences in Stx2a-encoding prophages.

Characterisation of Early Positive mcr-1 Resistance Gene and Plasmidome in Escherichia coli Pathogenic Strains Associated with Variable Phylogroups under Colistin Selection.

An antibiotic susceptibility monitoring programme was conducted from 2004 to 2010, resulting in a collection of 143 Escherichia coli cultured from bovine faecal samples (diarrhoea) and milk-aliquots (mastitis). The isolates were subjected to whole-genome sequencing and were distributed in phylogroups A, B1, B2, C, D, E, and G with no correlation for particular genotypes with pathotypes. In fact, the population structure showed that the strains belonging to the different phylogroups matched broadly to ST complexes; however, the isolates are randomly associated with the diseases, highlighting the necessity to investigate the virulence factors more accurately in order to identify the mechanisms by which they cause disease. The antimicrobial resistance was assessed phenotypically, confirming the genomic prediction on three isolates that were resistant to colistin, although one isolate was positive for the presence of the gene mcr-1 but susceptible to colistin. To further characterise the genomic context, the four strains were sequenced by using a single-molecule long read approach. Genetic analyses indicated that these four isolates harboured complex and diverse plasmids encoding not only antibiotic resistant genes (including mcr-1 and bla) but also virulence genes (siderophore, ColV, T4SS). A detailed description of the plasmids of these four E. coli strains, which are linked to bovine mastitis and diarrhoea, is presented for the first time along with the characterisation of the predicted antibiotic resistance genes. The study highlighted the diversity of incompatibility types encoding complex antibiotic resistance elements such as Tn6330, ISEcp1, Tn6029, and IS5075. The mcr-1 resistance determinant was identified in IncHI2 plasmids pCFS3273-1 and pCFS3292-1, thus providing some of the earliest examples of mcr-1 reported in Europe, and these sequences may be a representative of the early mcr-1 plasmidome characterisation in the EU/EEA.

Complete Closed Genome Sequence of the Extremely Heat-Resistant Strain Escherichia coli AW1.7.

Escherichia coli isolate AW1.7 is an extremely heat-resistant bacterium and has been widely used as a reference strain in extreme heat resistance studies for almost a decade. Here, we report its complete closed genome sequence.

Locus of Heat Resistance (LHR) in Meat-Borne Escherichia coli: Screening and Genetic Characterization.

Microbial resistance to processing treatments poses a food safety concern, as treatment tolerant pathogens can emerge. Occasional foodborne outbreaks caused by pathogenic Escherichia coli have led to human and economic losses. Therefore, this study screened for the extreme heat resistance (XHR) phenotype as well as one known genetic marker, the locus of heat resistance (LHR), in 4,123 E. coli isolates from diverse meat animals at different processing stages. The prevalences of XHR and LHR among the meat-borne E. coli were found to be 10.3% and 11.4%, respectively, with 19% agreement between the two. Finished meat products showed the highest LHR prevalence (24.3%) compared to other processing stages (0 to 0.6%). None of the LHR+E. coli in this study would be considered pathogens based on screening for virulence genes. Four high-quality genomes were generated by whole-genome sequencing of representative LHR+ isolates. Nine horizontally acquired LHRs were identified and characterized, four plasmid-borne and five chromosomal. Nine newly identified LHRs belong to ClpK1 LHR or ClpK2 LHR variants sharing 61 to 68% nucleotide sequence identity, while one LHR appears to be a hybrid. Our observations suggest positive correlation between the number of LHR regions present in isolates and the extent of heat resistance. The isolate exhibiting the highest degree of heat resistance possessed four LHRs belonging to three different variant groups. Maintenance of as many as four LHRs in a single genome emphasizes the benefits of the LHR in bacterial physiology and stress response.IMPORTANCE Currently, a "multiple-hurdle" approach based on a combination of different antimicrobial interventions, including heat, is being utilized during meat processing to control the burden of spoilage and pathogenic bacteria. Our recent study (M. Guragain, G. E. Smith, D. A. King, and J. M. Bosilevac, J Food Prot 83:1438-1443, 2020, https://doi.org/10.4315/JFP-20-103) suggests that U.S. beef cattle harbor Escherichia coli that possess the locus of heat resistance (LHR). LHR seemingly contributes to the global stress tolerance in bacteria and hence poses a food safety concern. Therefore, it is important to understand the distribution of the LHRs among meat-borne bacteria identified at different stages of different meat processing systems. Complete genome sequencing and comparative analysis of selected heat-resistant bacteria provide a clearer understanding of stress and heat resistance mechanisms. Further, sequencing data may offer a platform to gain further insights into the genetic background that provides optimal bacterial tolerance against heat and other processing treatments.

Range of Motion at Discharge Predicts Need for Manipulation following Total Knee Arthroplasty.

Stiffness following total knee arthroplasty (TKA) is a common complication that can result in unsatisfactory outcomes. Manipulation under anesthesia (MUA) has been widely employed to treat this problem. It is uncertain whether an association exists between range of motion (ROM) at discharge and need for MUA following primary TKA.A retrospective review of an institutional joint registry identified cases of primary TKA performed by three surgeons at a single institution over a 22-month period. A logistic regression model was used to examine the association between ROM at discharge and subsequent MUA controlling for confounding variables related to patient demographics and perioperative details. Of the 1,546 cases identified, 113 (7.3%) cases underwent subsequent MUA. As discharge ROM increased, manipulation rates decreased. Patients with discharge flexion <65 degrees were more likely to undergo MUA than those with flexion >90 degrees (odds ratio [OR] = 17.57, 95% confidence interval [CI] [7.97, 38.73], p < 0.0001). The largest differential in odds of MUA was observed between the <65 degrees at discharge group (OR = 17.57) and the 65 ≤ 75 degrees at discharge group (OR = 7.89). At discharge ROM of 80 ≤ 90 degrees of flexion, patients had more than a twofold increase in odds of MUA relative to those in the >90 degrees group (OR = 2.22, 95% CI [1.20, 4.10], p = 0.011). The results of this study suggest that there is an association between lower ROM at discharge and greater risk of MUA post primary TKA. Counseling patients in regard to discharge ROM and associated risk of MUA may optimize gains in ROM during recovery.

Anthropometric Measures of the Posterior Condyles: Gender Differences and Correlation to Implant Sizing.

There is abundant data concerning morphological dimensions of the distal femur, particularly in women, which has led to redesign of the femoral component in total knee arthroplasty (TKA). Clinical experience reveals existing asymmetry of the femoral posterior condyles, yet current implant designs have a symmetrical femoral component. The objectives of this study were to analyze the dimensions of posterior condylar bone resection from a group of patients undergoing TKA and correlate the measurements to one prosthetic system. We retrospectively reviewed single surgeon morphological data from the posterior condyles of 105 knees during TKA. The study included 54 males and 51 females. Measurement of the posterior condylar bones was performed with a standard metric metal ruler by one investigator. Known dimensions of a single type of implant design were compared with the resection data. The average difference of posterior medial and lateral condylar width was 5.7 and 5.3 mm in males and females, respectively. The average host posterolateral condylar bone was 5.4 mm less than the trial implant across five sizes in both males and females. Results suggest that the dimension of the posterior lateral condyle is much smaller than the dimension of the implant in both groups of patients. Dimension of the posterior medial is close to dimension of the implant. Overhang of the component posterolaterally can create soft tissue irritation and result in postoperative pain and decreased range of motion. Our results increase awareness of the dimensions of the native posterolateral condyle and may influence future design of femoral implants used in total knee arthroplasty.