Comprehensive Notes: Molecular Characterization & Antimicrobial Resistance of Urinary Escherichia coli in 20 Chinese Hospitals (JCM 2011)

Background & Rationale

• Pathogen importance: Escherichia coli (E. coli) is a critical pathogen, particularly in urinary tract infections (UTIs).

  • It accounts for approximately $90\%$ of community-acquired UTIs and about $50\%$ of nosocomial (hospital-acquired) UTIs.

  • First-line therapies worldwide commonly include $\beta$-lactams, especially cephalosporins, and quinolones due to their historical efficacy and broad-spectrum activity.

• Resistance concerns: The rise of antimicrobial resistance poses a significant challenge.

  • Quinolone resistance has traditionally been associated with mutations in the quinolone resistance-determining regions (QRDR) of DNA gyrase and topoisomerase IV, leading to target modification, along with decreased membrane permeability and increased efflux pump activity that expel the drug from the bacterial cell.

  • Increasingly, plasmid-mediated quinolone resistance (PMQR) genes are being reported, which confer low-level resistance that can facilitate the selection of high-level QRDR mutations.

  • Cephalosporin resistance is primarily mediated by the production of $\beta$-lactamases, enzymes that hydrolyze the $\beta$-lactam ring of the antibiotic, rendering it inactive.

    • Key $\beta$-lactamase types include Extended-Spectrum $\beta$-Lactamases (ESBLs), notably CTX-M enzymes, and AmpC $\beta$-lactamases.

    • These resistance genes are frequently located on conjugative plasmids, which are mobile genetic elements capable of rapid dissemination among different bacterial species and strains, contributing to wide and fast spread of resistance.

  • Previous reports from China have indicated a very high prevalence of CTX-M type ESBLs (e.g., CTX-M-14 and CTX-M-15), but lacked comprehensive large-scale studies incorporating phylogroup analysis, plasmid characterization, and direct comparisons between community-acquired and hospital-acquired isolates.

Study Objectives

• To thoroughly characterise urinary E. coli isolates from mainland China with respect to several key aspects:

  • Antimicrobial susceptibility: Determine resistance profiles against a panel of clinically relevant antibiotics.

  • Phylogenetic group distribution: Identify the prevalence of major E. coli phylogroups (A, B1, B2, D), which can provide insights into their pathogenicity and origin.

  • Presence of PMQR genes: Screen for plasmid-mediated quinolone resistance genes to understand their contribution to fluoroquinolone resistance.

  • Prevalence and diversity of extended-spectrum cephalosporinases (ESCs = ESBLs + AmpC): Identify and characterise the specific types and distribution of enzymes mediating resistance to third- and fourth-generation cephalosporins.

  • Clonal relatedness (PFGE) & multilocus sequence typing (MLST): Assess the genetic diversity and clonal spread of resistant isolates using pulsed-field gel electrophoresis (PFGE) for macro-restriction patterns and MLST for sequence-based typing of housekeeping genes.

  • Plasmid vehicles: Characterise the physical properties (size and replicon type) of plasmids carrying bla~CTX-M-14~/15 genes to understand their mobility and epidemiology.

  • Compare community- vs hospital-acquired isolates: Analyze and contrast the resistance patterns, genetic characteristics, and plasmid types between isolates from these two distinct settings to identify differences or common trends.

Sample Collection

• A total of $945$ clinical E. coli isolates were collected as part of the MOHNARIN (Monitoring of Highly-Resistant Nosocomial and Community-Acquired Organisms in China) network between January $2007$ and March $2008$. These isolates included diverse clinical sources.

• From this larger collection, a specific subset of $305$ isolates associated with UTIs were identified. After further screening for viability and quality, $222$ unique isolates were deemed suitable and included in the final study for comprehensive analysis.

• The sample collection demonstrated broad geographical representation across China:

  • Isolates were sourced from $20$ tertiary hospitals located in $15$ provinces and $4$ municipalities, effectively spanning all six major geographical districts of China.

  • Specific hospital contributions included (but were not limited to): Beijing University First Hospital ($n=12$), Ruijin Hospital, Shanghai ($n=10$), China-Japan Friendship Hospital ($n=10$), Sichuan University Huaxi Hospital ($n=11$), Beijing Chaoyang Hospital ($n=12$), and Xinjiang Medical University ($n=10$), among others.

• Infection origin classification was meticulously performed based on admission time to differentiate between settings:

  • Community-acquired: $95$ isolates were classified as community-acquired, meaning they were collected within $48$ hours of patient admission to a healthcare facility, suggesting infection onset outside the hospital environment.

  • Hospital-acquired: $39$ isolates were identified as hospital-acquired, indicating they were collected more than $48$ hours after patient admission, pointing to an infection acquired within the nosocomial setting.

  • Onset unknown: $88$ isolates had an unclear or indeterminate onset time, preventing their definitive classification into either community or hospital-acquired categories.

Methods Overview

• Antimicrobial testing: Minimum Inhibitory Concentrations (MICs) were determined using the agar serial dilution method, strictly following the guidelines set by the Clinical and Laboratory Standards Institute (CLSI M100-S20). E. coli ATCC $25922$ was used as the quality control (QC) strain to ensure accuracy and reproducibility of results.

  • A comprehensive panel of $17$ antimicrobial agents was tested, covering various classes: Amoxicillin-Clavulanic Acid (AMC), Piperacillin (PIP), Piperacillin-Tazobactam (TZP), Cefazolin (CFZ), Cefuroxime (CXM), Cefoxitin (CRR), Cefoperazone (CFP), Ceftriaxone (CRO), Ceftazidime (CAZ), Ceftazidime/Avibactam (CPD), Cefepime (FEP), Moxalactam (MOX), Gentamicin (GEN), Amikacin (AMK), Imipenem (IMP), Ciprofloxacin (CIP), Levofloxacin (LVF), and Moxifloxacin (MXF).

  • European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints were specifically applied for MXF susceptibility interpretation: susceptible ($\le 0.5\,\mu g/mL$) and resistant ($\ge 1\,\mu g/mL$).

  • A confirmatory ESC phenotypic test was performed on $28$ selected isolates (16 of which were bla~CTX-M~-negative and 12 contained only bla~TEM-1b~) to verify ESBL production visually.

• Phylogrouping: E. coli phylogroups (A, B1, B2, D, or NT for non-typable) were determined using the Clermont quadruplex multiplex PCR method, which amplifies specific genetic markers: chuA, yjaA, and TSPE4.C2, allowing for rapid and accurate assignment.

• Gene detection:

  • PMQR genes: Isolates were screened for a range of plasmid-mediated quinolone resistance genes including qnrA, qnrB, qnrC, qnrD, qnrS, qepA, and aac(6')-Ib-cr.

  • Cephalosporinase genes: PCR was used to detect specific $\beta$-lactamase genes. bla~CTX~ (for CTX-M type ESBLs) and bla~TEM~ were screened in $138$ isolates that showed non-susceptibility to Ceftriaxone (CRO) or Cefepime (FEP). bla~CMY-1/2~ (for AmpC $\beta$-lactamases) was screened in $9$ isolates resistant to Cefoxitin (CXM).

  • AmpC promoter sequencing: For isolates suspected of AmpC over-expression, the promoter region of the chromosomal ampC gene was sequenced to identify mutations associated with increased AmpC production.

• Microarray: The Identibac Amr-ve array, a microarray-based rapid $\beta$-lactamase gene screening platform, was employed on $5$ representative strains to confirm the presence and identity of resistance genes, specifically bla~CTX-M~ and bla~TEM~ families.

• PFGE: Pulsed-field gel electrophoresis (PFGE) was used for assessing clonal relatedness. Genomic DNA was digested with the restriction enzyme XbaI, and fragments were separated using a Chef DR-III system with conditions optimized for E. coli (pulse times ranging from 2.2 to 54.2 seconds over 19 hours). Salmonella Braenderup H9812 was used as a molecular size marker. Cluster analysis was performed using Dice coefficients with unweighted pair group method with arithmetic mean (UPGMA), applying similarity cut-offs of $85\%$ and $69\%$ to define clusters.

• Plasmid work:

  • Transformation: Plasmids carrying bla~CTX-M~ genes were transformed into electrocompetent E. coli GeneHog (DH10B) recipient strain to isolate and characterise the specific resistance plasmids. Transformants were selected on agar plates containing Cefotaxime (CTX) at $2\,\mu g/mL$.

  • S1-PFGE: Plasmid sizes were determined using S1 nuclease digestion followed by PFGE (S1-PFGE), allowing for the migration and estimation of large plasmid sizes, typically ranging from $\approx 10$ to $137\,\text{kb}$.

  • PCR-based replicon typing (PBRT): Plasmid incompatibility (Inc) groups were determined by PBRT, targeting common plasmid replicon types such as IncFrepB, IncI1, IncN, IncFIA/B, IncB/O, IncQ, repA1, among others, to understand plasmid epidemiology.

  • Southern probing: For characterising smaller plasmids or confirming gene location, Southern blot hybridization was performed, particularly for isolates A012 and B233, using specific gene probes.

• MLST: Multilocus sequence typing (MLST) was performed on $13$ selected phylogroup B2 CTX-M positive isolates to determine their specific sequence types (STs). This method involved sequencing seven housekeeping genes: adk (adenylate kinase), fumC (fumarate hydratase), gyrB (DNA gyrase B), icd (isocitrate dehydrogenase), mdh (malate dehydrogenase), purA (adenylosuccinate synthase), and recA (recombinase A). Allele profiles were then used to assign STs.

• Statistics: Statistical analysis was conducted using SPSS version $16.0$. The chi-square test or Fisher’s exact test (when expected cell counts were low) were applied to compare the distributions of antimicrobial resistance, resistance genes, and replicon types between different groups (e.g., community vs. hospital-acquired isolates). A $P$-value less than $0.05$ (P<0.05) was considered statistically significant.

Results

Antimicrobial Susceptibility

• Universal susceptibility: All isolates in the study demonstrated universal susceptibility (0% resistance) to Imipenem (IMP), indicating its continued efficacy against these strains during the study period.

• Very low resistance: Resistance rates were remarkably low for Tazobactam-Piperacillin (TZP) at $\approx 0.45\%$, Moxalactam (MOX) at $\approx 1\%$, and Amikacin (AMK) at $\approx 7\%$. These agents maintained high effectiveness.

• Moderate resistance: Moderate resistance rates were observed for Cefepime (FEP) at $14\%$ and Amoxicillin-Clavulanic Acid (AMC) at $25\%$. While not excessively high, these figures suggest a growing concern for empirical use.

• High resistance (>46\%$%): A significant and concerning level of resistance was found for several crucial antibiotic classes:

  • Fluoroquinolones: Resistance was exceptionally high, with Moxifloxacin (MXF) at 85\%$, Ciprofloxacin (CIP) at$75\%$, and Levofloxacin (LVF) at$71\%$. This widespread resistance severely limits their utility for empirical therapy.</p></li><li><p><strong>Cephalosporins, Piperacillin, and Gentamicin</strong>: High resistance rates were also documented for various cephalosporins: Piperacillin (PIP)$73\%$, Cefazolin (CFZ)$68\%$, Cefuroxime (CXM)$67\%$, Cefoxitin (CRR)$69\%$, Cefoperazone (CFP)$57\%$, Ceftriaxone (CRO)$46\%$, Ceftazidime (CAZ)$67\%$, and Ceftazidime/Avibactam (CPD)$69\%$. Gentamicin (GEN) resistance was also high at$63\%$. These values highlight a broad spectrum of resistance affecting multiple frontline agents.</p></li></ul></li><li><p><strong>Community vs hospital comparison</strong>: Notably, no statistically significant differences in resistance rates were observed between community-acquired and hospital-acquired isolates across any of the tested antimicrobial agents ($P>0.05$for all comparisons). This finding indicates that high resistance levels are widespread and equally prevalent in both settings, suggesting a pervasive resistance problem rather than being confined to healthcare environments.</p></li><li><p><strong>ESC phenotypic confirmation</strong>: Out of$28$isolates specifically re-tested phenotypically for ESC production,$9$were confirmed as resistant or intermediately resistant to Cefuroxime (CXM), indicating likely ESBL presence. The remaining$19$isolates were sensitive, suggesting no ESBL production, which correlates with the genotypic results.</p></li></ul><h5 id="beebf3d0-f2fb-485f-bbd8-763f5f80dd41" data-toc-id="beebf3d0-f2fb-485f-bbd8-763f5f80dd41" collapsed="false" seolevelmigrated="true">Phylogenetic Distribution</h5><ul><li><p><strong>Overall distribution ($n=222$)</strong>:</p><ul><li><p><strong>Group D</strong> was the most common phylogroup, accounting for$54\%$of all isolates. This group often includes highly pathogenic strains and is frequently associated with UTIs.</p></li><li><p><strong>Group B2</strong>, commonly recognized for its uro-pathogenic strains (UPECs), represented$19\%$. While less prevalent than group D in this study, it remains a significant contributor.</p></li><li><p><strong>Group A</strong> was found in$12\%$of isolates, and <strong>Group B1</strong> in$8\%$. These groups typically include commensal E. coli but can also cause infections. A minority ($6\%$) of isolates were non-typable (NT).</p></li></ul></li><li><p><strong>Community vs hospital comparison (no significant differences)</strong>:</p><ul><li><p>While overall distributions were similar, <strong>Group D</strong> showed a slightly higher prevalence in hospital-acquired isolates ($62\%$) compared to community-acquired isolates ($49\%$, though this difference was not statistically significant). This subtle trend might suggest a greater propensity for D group strains to cause nosocomial infections.</p></li><li><p>Conversely, <strong>Group B2</strong> was more frequently observed in community-acquired isolates ($27\%$) compared to hospital-acquired ones ($10\%$), consistent with its known association with community-onset UTIs, albeit without statistical significance in this specific comparison.</p></li></ul></li><li><p><strong>CTX-M linkage with phylogroups</strong>:</p><ul><li><p><em>bla</em>~CTX-M-14~ was predominantly found in isolates belonging to phylogroup D ($57\%$) and phylogroup B2 ($10\%$), indicating its significant association with these major uropathogenic lineages.</p></li><li><p><em>bla</em>~CTX-M-15~ was also chiefly detected in phylogroup D ($40\%$) and notably in phylogroup A ($25\%$), suggesting its presence in a broader range of E. coli lineages, including those often considered commensal but capable of causing infection.</p></li></ul></li></ul><h5 id="45765584-271a-48db-9a20-897858a6340f" data-toc-id="45765584-271a-48db-9a20-897858a6340f" collapsed="false" seolevelmigrated="true">Resistance Gene Findings</h5><ul><li><p><strong>PMQR genes in entire collection ($n=222$)</strong>:</p><ul><li><p><em>qnrS1</em> was detected in$4$isolates.</p></li><li><p><em>qepA</em> was found in$4$isolates.</p></li><li><p><em>aac(6')-Ib-cr</em> was the most prevalent PMQR gene, identified in$16$isolates. This gene can acetylate aminoglycosides and also modify quinolones, contributing to low-level quinolone resistance.</p></li></ul></li><li><p><strong>Extended-spectrum cephalosporinases (ESCs) among$138$ESC-suspects</strong>:</p><ul><li><p><em>bla</em>~CTX-M~ positive: A high proportion,$110$isolates ($80\%$), were positive for <em>bla</em>~CTX-M~ genes, confirming the dominance of this ESBL family.</p></li><li><p><strong>CTX-M subtypes</strong>: The most common variants were CTX-M-14 ($70$isolates,$71\%$) and CTX-M-15 ($24$isolates,$24\%$), consistent with their global prevalence. Other less common but significant subtypes included CTX-M-3 ($8$), CTX-M-65 ($3$), CTX-M-79 ($2$), CTX-M-27 ($2$), and CTX-M-22 ($1$).</p></li><li><p><em>bla</em>~TEM~ was detected in$79$isolates. Among these, <em>bla</em>~TEM-1b~ was the predominant variant, a common narrow-spectrum$\beta$-lactamase often found alongside ESBLs.</p></li><li><p><strong>AmpC</strong>: <em>bla</em>~CMY-2~, an acquired AmpC$\beta$-lactamase gene, was detected in$3$isolates. Additionally, chromosomal <em>ampC</em> promoter mutations were identified in$7$out of$9$Cefuroxime (CXM)-nonsusceptible isolates. These mutations (specifically at positions$-88, -82, -76, -58, -42, -32, -26, -22, -18, -1, +1$relative to the transcription start) lead to the overexpression of the intrinsic chromosomal AmpC enzyme, contributing to resistance against cephalosporins.</p></li></ul></li><li><p><em>bla</em>~CTX-M~ geography: <em>bla</em>~CTX-M~ genes were widely distributed and found in isolates from all six Chinese districts, indicating broad dissemination across the country. Furthermore, there was no statistically significant difference in the prevalence of CTX-M-14 (<em>P=0.428</em>) or CTX-M-15 (<em>P=0.699</em>) between community-acquired and hospital-acquired isolates, reinforcing the notion of widespread community and hospital dissemination.</p></li></ul><h5 id="41018b9a-4e6b-4d60-843d-b01a9a78b0ac" data-toc-id="41018b9a-4e6b-4d60-843d-b01a9a78b0ac" collapsed="false" seolevelmigrated="true">Microarray Confirmation</h5><ul><li><p>The microarray analysis independently confirmed the findings from PCR-based gene detection. The most common$\beta$-lactamase families identified were the <em>bla</em>~CTX-M-9~ group (which was specifically confirmed as CTX-M-14) and <em>bla</em>~TEM-1~, showing 100$69\%$similarity</strong>: Using a$69\%$similarity cut-off, which represents relatively distant clonal relationships, the$43$isolates formed$7$distinct clusters and$10$singletons. This still points to considerable genetic diversity.</p></li><li><p><strong>High diversity at$85\%$similarity</strong>: When a stricter$85\%$similarity cut-off was applied (indicating closely related strains), very high diversity was observed across both hospital and community isolates. This strong clonal heterogeneity reinforces the idea that resistance spread is mainly attributable to the horizontal transfer of resistance genes, often on mobile genetic elements like plasmids, rather than the vertical expansion of a limited number of successful E. coli clones.</p></li></ul><h5 id="d6f232b4-72b0-42e6-9188-ef14922911ee" data-toc-id="d6f232b4-72b0-42e6-9188-ef14922911ee" collapsed="false" seolevelmigrated="true">Plasmid Analysis (38 transformants with single CTX-M plasmid)</h5><ul><li><p><strong>Size range</strong>: Isolated plasmids carrying CTX-M genes varied significantly in size, ranging from approximately$10$to$137\,\text{kb}$. This wide range suggests diverse plasmid backbones capable of carrying these resistance determinants.</p></li><li><p><strong>Replicon types detected</strong>: A variety of plasmid incompatibility (Inc) groups were identified, demonstrating a broad plasmid ecology involved in CTX-M dissemination:</p><ul><li><p><strong>IncFrepB</strong>: The most common replicon type, detected in$17$plasmids. These plasmids are often large, conjugative, and associated with multidrug resistance.</p></li><li><p><strong>IncI1</strong>: Also highly prevalent, found in$15$plasmids. IncI1 plasmids are known for their role in disseminating ESBLs, particularly CTX-M enzymes, globally.</p></li><li><p>Other replicon types present included IncN, IncFIA, IncFIB, IncB/O, IncQ, and <em>repA1</em>, indicating the involvement of multiple plasmid families.</p></li><li><p><strong>Multireplicon plasmids</strong>: A notable finding was the presence of plasmids carrying multiple replicon types, indicating complex plasmid architectures and potential for increased stability and host range. Examples include:</p><ul><li><p>IncFrepB + IncFIB</p></li><li><p>IncFrepB + IncI1</p></li><li><p>IncI1 + IncFIB</p></li><li><p>One <em>bla</em>~CTX-M-14~ plasmid specifically exhibited a triple replicon combination of IncFrepB + IncFIA + IncFIB, highlighting a sophisticated mechanism for resistance gene carriage.</p></li></ul></li></ul></li><li><p><strong>Untypeable plasmids</strong>:$2$plasmids could not be assigned to any known replicon type using the PBRT method, suggesting the presence of novel or less common plasmid backbones.</p></li><li><p><strong>No significant associations</strong>: There was no statistically significant association observed between specific replicon types and CTX-M subtypes (e.g., IncFrepB being exclusively linked to CTX-M-14). Similarly, the prevalence of specific replicon types did not significantly differ between community-acquired and hospital-acquired settings, underscoring the widespread distribution of these mobile genetic elements across different epidemiological contexts.</p></li></ul><h5 id="df6d1cd7-0e39-4f38-a1ae-a5e86e014a2c" data-toc-id="df6d1cd7-0e39-4f38-a1ae-a5e86e014a2c" collapsed="false" seolevelmigrated="true">MLST (13 phylogroup B2 CTX-M isolates)</h5><ul><li><p><strong>ST131 detection</strong>: The globally disseminated and highly successful sequence type ST131 was detected in a significant proportion of phylogroup B2 CTX-M isolates:</p><ul><li><p>All$3$CTX-M-15 positive B2 isolates belonged to ST131.</p></li><li><p>$6$out of$10$CTX-M-14 positive B2 isolates also belonged to ST131.<br>This confirms the strong association of ST131 with the spread of <em>bla</em>~CTX-M~ resistance, particularly CTX-M-15, in pathogenic E. coli.</p></li></ul></li><li><p><strong>Other sequence types</strong>: Besides ST131, other sequence types identified included ST73 complex ($2$isolates), ST127 ($1$isolate), and ST10 complex ($1 isolate). These STs also represent successful pathogenic or commensal lineages with potential for resistance. The presence of multiple STs, even within the B2 phylogroup, supports the overall finding of high clonal heterogeneity despite the prominence of ST131.

  Discussion & Interpretation

  • Alarmingly high resistance to cephalosporins and fluoroquinolones: The study reveals critically high levels of resistance to key empirical agents like cephalosporins and fluoroquinolones in both community and hospital settings in China. This widespread resistance suggests that empirical use of these antibiotics for UTIs in China should be urgently reconsidered, as they are likely to fail in a majority of cases. This calls for a shift towards alternative therapies or rapid susceptibility testing.

  • CTX-M diversity: The detection of not only the globally dominant CTX-M-14 and CTX-M-15 but also rarer variants such as CTX-M-22, CTX-M-27, CTX-M-65, and CTX-M-79 is significant. Some of these rarer subtypes have previously been linked to Chinese food animals, raising the possibility of zoonotic transmission or food-borne reservoirs contributing to human UTIs. This highlights the importance of a One Health approach.

  • Phylogroup findings: The dominance of phylogroup D and the notable presence of groups A and B1, alongside phylogroup B2, suggest that UTIs in China are caused by a mix of highly virulent uropathogenic lineages (e.g., certain D and B2 strains) and potentially generalist or commensal/animal-linked strains (more common in A and B1). This broad genetic background of E. coli causing UTIs complicates understanding and control measures, as both specific pathogens and more widespread commensal strains contribute to the resistance burden.

  • ST131 dissemination: The finding of ST131, a globally recognized multidrug-resistant (MDR) clone, further confirms its successful spread and significant role in MDR UTIs within China. However, the concurrent PFGE analysis showing overall high clonal heterogeneity (i.e., many different E. coli strains) among the resistant isolates indicates that the high resistance prevalence is primarily plasmid-driven rather than solely due to the expansion of a few highly successful ST131 lineages. This implies that plasmids are efficiently transferring resistance genes across diverse E. coli clones.

  • Plasmid ecology: The wide variety of observed plasmid replicon types (e.g., IncFrepB, IncI1) and the frequent occurrence of multireplicon structures are critical. This indicates ongoing plasmid evolution and adaptation under antimicrobial selective pressure, allowing these mobile genetic elements to persist, acquire multiple resistance genes, and disseminate widely. Such complex plasmid ecology complicates control efforts, as resistance can be horizontally transferred between different bacterial strains and species.

  • Community reservoir: The comparable resistance and genetic patterns between community and hospital settings is a crucial finding. This similarity suggests a long-standing and widespread dissemination of resistant E. coli and their associated resistance genes in the general population, not just within healthcare facilities. Consequently, interventions must comprehensively target not only hospitals but also the community and potentially even the food animal sectors to effectively curb the spread of resistance.

  Practical & Policy Implications

  • Review empirical UTI treatment guidelines in China: Given the alarmingly high resistance rates to commonly used antibiotics, it is imperative to promptly revise and update national and local empirical UTI treatment guidelines. Consideration should be given to agents with preserved activity, such as Imipenem (\text{IMP}$), Piperacillin-Tazobactam ($\text{TZP}$), and Moxalactam ($\text{MOX}$$), as indicated by this dataset's susceptibility rates. This implies a need for more restricted use of fluoroquinolones and certain cephalosporins.

  • Strengthen antimicrobial stewardship: Comprehensive antimicrobial stewardship programs are crucial, not only in hospitals but also, and critically, in outpatient and community settings where a significant proportion of antibiotic prescribing occurs. These programs should focus on promoting appropriate prescribing, reducing unnecessary consumption, and educating both healthcare providers and the public.

  • Integrated surveillance (One Health): Surveillance efforts should adopt a holistic 'One Health' approach, integrating data collection and analysis from human clinical isolates (hospital and community), animal populations (especially food animals), and the food supply chain. This integrated surveillance is essential to effectively track the movement and evolution of resistance plasmids and clonal lineages across different ecological niches and identify potential cross-sectoral transmission.

  • Infection control: Enhanced infection control measures are warranted. This includes routine screening for CTX-M producers, particularly within high-risk populations or settings, and implementing strict contact precautions where feasible to prevent the spread of these resistant bacteria among patients. Improved hygiene practices in both clinical and community settings are also vital.

  • Research: Continued research is necessary to monitor the evolution of multireplicon plasmids, understand their mechanisms of persistence and dissemination, and evaluate the fitness cost associated with carriage of these resistance elements. Furthermore, studies on the transmission dynamics of resistant strains and plasmids between humans, animals, and the environment are vital to inform future control strategies.

  Ethical & Philosophical Notes

  • Collective responsibility: The findings profoundly highlight a collective responsibility in the global fight against antimicrobial resistance. Inappropriate antimicrobial use, whether in human healthcare (e.g., over-prescription, non-adherence), agriculture (e.g., growth promotion, prophylactic use), or through community self-medication, propagates resistance. This resistance in turn threatens the effectiveness of antibiotics for everyone, underscoring that individual actions have widespread public health consequences.

  • Equity issues: The comparable high resistance rates observed in both rural and urban regions and across different settings (community vs. hospital) raise significant equity issues. It suggests that a pervasive resistance problem affects broad populations equally, regardless of geographical location or access to specialized healthcare. This necessitates that public health measures and interventions designed to combat antimicrobial resistance must be comprehensive and capable of reaching and benefiting diverse and broad populations, ensuring