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Communication

The Nosocomial Transmission of Carbapenem-Resistant Gram-Negative Bacteria in a Hospital in Baoding City, China

by
Shengnan Liao
1,†,
Wei Su
2,†,
Tianjiao Li
1,
Zeyang Li
3,
Zihan Pei
3,
Jie Zhang
1 and
Wenjuan Yin
1,*
1
Key Laboratory of Pathogenesis Mechanism and Control of Inflammatory-Autoimmune Diseases of Hebei Province, College of Basic Medical Science, Hebei University, Baoding 071002, China
2
Laboratory of Affiliated Hospital of Hebei University, Baoding 071000, China
3
School of Clinical Medicine, Hebei University, Baoding 071002, China
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this article.
Microbiol. Res. 2025, 16(7), 147; https://doi.org/10.3390/microbiolres16070147
Submission received: 19 May 2025 / Revised: 16 June 2025 / Accepted: 19 June 2025 / Published: 2 July 2025
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Abstract

Background: The global rise of multidrug-resistant Gram-negative bacteria, particularly non-fermenting species and carbapenemase-producing Enterobacteriaceae, poses a significant challenge to hospital infection control. Methods: In this study, a total of 89 Acinetobacter spp. isolates, 14 Pseudomonas aeruginosa, and 14 carbapenem-resistant Enterobacteriaceae isolates were collected from patients in a tertiary hospital. Whole-genome sequencing and antimicrobial susceptibility testing were conducted. Resistance mechanisms and evolutionary relationships were analyzed using phylogenetic analysis and genetic context mapping. Results: Among the non-fermenting isolates, A. baumannii exhibited high resistance to carbapenems, clustering into distinct clonal groups enriched with genes associated with biofilm formation and virulence genes. P. aeruginosa isolates harbored fewer resistance genes but carried notable mutations in the efflux pump systems and the oprD gene. In Enterobacteriaceae, four blaNDM alleles were identified within a conservative structural sequence, while blaKPC-2 was located in a non-Tn4401 structure flanked by IS481- and IS1182-like insertion sequences. Phylogenetic analysis revealed that blaNDM-positive E. coli strains were closely related to susceptible lineages, indicating horizontal gene transfer. Conversely, K. pneumoniae isolates harboring blaKPC-2 formed a tight clonal cluster, suggesting clonal expansion. Conclusions: The study reveals distinct transmission patterns between resistance genes: horizontal dissemination of blaNDM and clonal expansion of blaKPC-2 in K. pneumoniae. These findings emphasize the need for resistance-gene-specific genomic surveillance and infection control strategies to prevent further nosocomial dissemination.

1. Introduction

Multidrug-resistant (MDR) pathogens have emerged as a critical global threat and are under intensive surveillance in clinical settings. Of particular concern are the ESKAPE pathogens, which include Enterococcus faecium (E), Staphylococcus aureus (S), Klebsiella pneumoniae (K), Acinetobacter baumannii (A), Pseudomonas aeruginosa (P), and Enterobacter species (E). The ESKAPE strains are the predominant opportunistic pathogens responsible for nosocomial infections. These organisms are capable of causing infections in various anatomical sites such as the respiratory tract, gastrointestinal tract, and urinary tract [1]. ESKAPE pathogens exhibit a strong propensity to acquire resistance to a wide range of antibiotics, especially those considered last-resort options like carbapenems and polymyxins [2].
Among these, A. baumannii and P. aeruginosa are non-glucose-fermenting Gram-negative bacilli [3,4,5]. Notably, MDR A. baumannii (MRAB) and MDR P. aeruginosa (MRPA) have emerged as significant threats due to the limited therapeutic options available [6,7,8]. Surveillance of resistance trends in these bacteria is of the utmost importance. In recent years, carbapenem resistance among non-fermenting Gram-negative bacilli (CR-NF) has been gradually increasing worldwide [9,10,11,12]. According to CHINET (http://www.chinets.com/Data/AntibioticDrugFast, accessed on 1 June 2022) surveillance data, the proportion of A. baumannii strains resistant to carbapenemases rose rapidly from <40% in 2005 to >70% in 2021, respectively [13].
In A. baumannii, resistance is primarily driven by the OXA-23 oxacillinase, which hydrolyzes carbapenemase. Similarly, P. aeruginosa is increasingly harboring extended-spectrum β-lactamases (ESBLs) and carbapenemase (especially metallo-β-lactamase) genes, contributing to nosocomial infection rates that reach nearly 50% in some areas [9]. The prevalence of MDR non-fermenting Gram-negative bacilli (MDR-NF) has also become a serious concern to clinical patients, particularly if they are aging or are immune-deficient in intensive care units (ICUs). Reflecting this clinical importance, the World Health Organization (WHO) has designated carbapenem-resistant A. baumannii and P. aeruginosa as priority pathogens for the research and development of new antimicrobials [14].
Other MDR-NFs, such as Stenotrophomonas maltophilia and Burkholderia spp, possess chromosomally encoded carbapenemases, and the genes that carry these are not easily transferred horizontally among organisms [14]. Besides carbapenems, tigecycline and polymyxins are often considered last-resort agents for treating Gram-negative infections. Tigecycline resistance commonly arises from the acquisition of tet(X) genes, mutations, and the inhibition of ribosomal-binding sites and it is active through efflux pumps [15]. Due to the presence of the MexXY-OprM efflux pump, P. aeruginosa is intrinsically resistant to tigecyclines [16]. The mechanism of polymyxin resistance in non-fermenting Gram-negative bacteria is mainly mediated by the two-component regulatory system, and some strains carry the transferable polymyxin resistance gene mcr [17,18,19,20].
Carbapenem-resistant Enterobacteriaceae (CRE) also represent a major public health concern, particularly in healthcare settings, where they are associated with high morbidity and mortality rates [21]. These pathogens commonly carry horizontally transferable carbapenem resistance genes, which inactivate carbapenem antibiotics through the production of carbapenemases. Among the most clinically important carbapenemases are blaNDM and blaKPC-2, both of which have disseminated globally [22,23]. Since first being reported in 2008, the blaNDM gene has expanded into more than 30 allelic variants, which are widely detected in E. coli, K. pneumoniae, and E. cloacae and are often embedded in composite transposons or integrons flanked by insertion sequences such as ISAba125, which enhance its mobility and facilitate interspecies gene transfer [24]. In parallel, blaKPC-2, originally identified in K. pneumoniae, has become endemic in regions such as China, South America, and parts of Europe. Typically embedded within the Tn4401 transposon, recent studies have also described non-Tn4401 platforms, indicating structural diversity in the genetic context of this resistance gene [25,26].
The co-circulation of blaNDM and blaKPC in clinical isolates has significantly limited treatment options, leading to the increased use of toxic alternatives such as polymyxins and tigecycline. Consequently, a deeper understanding of the genetic backgrounds and dissemination mechanisms of these resistance determinants are crucial for designing effective control strategies and guiding antimicrobial stewardship efforts.
This study was conducted from 2020 to 2024 at a teaching hospital in Baoding, Hebei province, and involved the collection of MDR non-fermenting Gram-negative bacilli (MDNF) and Enterobacteriaceae carrying horizontally transferable carbapenem resistance genes. The findings of this study will provide valuable insights for the development of effective strategies aimed at controlling and reducing untreatable infections in clinical settings.

2. Materials and Methods

2.1. Collection of Clinical Isolates, Species Identification, and Antimicrobial Susceptibility Testing

Clinical isolates were collected from the microbiology laboratory of the Affiliated Hospital of Hebei University from 2020 to 2024. They were identified using a BD Phoenix-100 Microbiology System (Becton Dickinson & Company, Franklin Lakes, NJ, USA). This system determined the bacterial genus and assessed its resistance profiles against a wide spectrum of antibiotics, including carbapenems, cephalosporins, β-lactams, aminoglycosides, quinolones, tetracyclines, sulfonamides, phosphomycin, nitrofurans, chloramphenicol, and polymyxin. Antimicrobial susceptibility interpretations were conducted in accordance with the guidelines issued by the Clinical & Laboratory Standards Institute (CLSI). Strain information is visualized via a Sankey diagram.

2.2. Whole-Genome Sequencing

For genomic DNA, representative bacterial strains were selected and subjected to extraction using a TIANGEN Genomic DNA Purification Kit (TIANGEN, Beijing, China). Whole-genome sequencing was carried out using the Illumina NovaSeq platform, generating 150 bp paired-end reads. The sequencing data for each bacterial strain exceeded 500 Mb. Short reads were de novo assembled using SPAdes 3.15.4 (https://github.com/ablab/spades, accessed on 1 June 2022). yielding draft genome assemblies for downstream analyses.

2.3. Molecular Characterization

Antibiotic resistance genes, virulence factors, mobile genetic elements, and bacterial MLST (Multi-Locus Sequence Typing) were analyzed using SRST2 (https://hpc.nih.gov/apps/srst2.html), VFDB (http://www.mgc.ac.cn/VFs/, Version 2024), and the Center for Genomic Epidemiology (http://www.genomicepidemiology.org/services/index.html, ResFinder Version 4.7.2). Genome annotations were performed using Rapid Annotation using Subsystem Technology (https://rast.nmpdr.org/, Version 2.0). The Clustal W 2.1 (https://www.genome.jp/tools-bin/clustalw) was used to align the amino acid sequences of OprD in A. pittii, and GeneDoc 2.7.0 (https://github.com/karlnicholas/GeneDoc) was used to visualize the alignment results. The BLAST Ring Image Generator (BRIG-0.95) (http://sourceforge.net/projects/brig/) was used to map the comparative genomic circular map of MDR A. baumannii and P. aeruginosa. Easyfig (https://github.com/mjsull/Easyfig/releases/tag/2.2.5) was used to visualize the sequence alignment differences in the blaNDM and blaKPC genetic environment. The access dates for all websites fall within the period of June to July 2024.

2.4. Phylogenetic Analyses

A core single-nucleotide polymorphism (SNP)-based phylogenetic tree was constructed using 18 assembled A. baumannii genomes, including 14 MDR strains and 4 susceptible controls. Parsnp v2.0.0 and iTOL V7 (https://itol.embl.de/) were used to generate and visualize the phylogenetic tree, respectively. Similar analyses were carried out for carbapenem-resistant Enterobacteriaceae, specifically blaNDM-positive E. coli and blaKPC-2-positive K. pneumonia isolates.

2.5. Induction of Polymyxin-Resistant A. baumannii

To induce polymyxin resistance, clinical isolates of A. baumannii were first revived on Luria–Bertani (LB) agar without antibiotics. A single colony was then inoculated into LB broth and grown to the logarithmic phase. The cultured A. baumannii was directly plated onto LB agar containing 10 μg/mL of polymyxin sulfate to select for polymyxin-resistant variants. Polymyxin resistance phenotype was confirmed using the E-test method. To investigate potential lipid A structural alterations, lipid A was isolated and further identified using Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) [27]. MALDI-TOF MS analysis was performed on a 4800 Proteomics Analyzer (Applied Biosystems, Foster City, CA, USA) using the reflectron mode.

3. Results and Discussion

3.1. Epidemiological Feature of MDR Non-Fermenting Gram-Negative Bacteria

A total of 89 isolates of Acinetobacter spp. and 14 isolates of P. aeruginosa were obtained. Among the A. baumannii strains, 46 exhibited resistance to carbapenemase (details listed in Table S1). Among the P. aeruginosa isolates, 12 displayed multidrug resistance, including 2 strains resistant to tigecycline. Samples were collected from various hospital departments; most A. baumannii isolates were collected from the intensive care unit (ICU). Although fewer P. aeruginosa strains were recovered, they were distributed in multiple departments, including the ICU, Neurological Critical Care (NCC), Hepatobiliary Surgery (HPB Surgery), and the nephrology department. The majority of the isolates were obtained from sputum samples (Figure 1A and Table S1). A subset non-fermenting Gram-negative bacteria demonstrated intrinsic resistance to carbapenems. Compared to meropenem and imipenem, a slightly higher resistance rate was observed for ertapenem (Figure 1B and Table S2). In A. baumannii, only WE1575 and WE2259 exhibited such resistance phenotypes. Resistance rates to piperacillin/tazobactam, amikacin, and tobramycin were below 70%. However, the resistance rates for other antibiotics exceeded this value, with levofloxacin, ampicillin/sulbactam, and ceftazidime showing resistance rates higher than 80%.

3.2. Antibiotic Resistance, Virulence, and Adaptive Evolution in A. baumannii

Both MDR and susceptible strains were further elucidated to investigate their resistance mechanisms. Core-genome SNP phylogeny revealed distinct clustering between the MDR and susceptible strains (Figure 2A). Comparative genome analyses revealed a consistent gene profile across MDR strains, except for aac(6’)-Ib3 and qacE. Notably, three strains (WE1499, WE2086, and WE1502), as well as WE2259 and WE1800, exhibited identical antibiotic resistance gene profiles. These two branches originated from the HPB Surgery unit and ICU, within approximately 10 days of each other. Consistent resistance phenotype among other isolates from these departments further support this hypothesis (Tables S1 and S2).
WGS furthermore revealed the presence of virulence factors associated with adherence, biofilm formation, immune evasion, iron uptake, serum resistance, and other pathogenic mechanisms (Table S3). Specifically, genes such as adeFGH, csuA/BABCDE, bfmR/S, and pgaABCD were identified as essential components for the robust biofilm development in A. baumannii. Interestingly, the strains WE1499, WE2086, and WE1502 lacked genes associated with biofilm formation, making these three strains sensitive to antibiotics such as ceftriaxone and ciprofloxacin.
BRIG-based genome comparisons (Figure 2B) confirmed high chromosomal sequence similarity between A. baumannii and the reference gene A85 (NZ_JACSSO000000000.1). Compared with the reference strains, the missing parts mainly included some metal resistance genes and phage-derived sequences. Despite general susceptibility to polymyxin (MIC < 0.5 µg/mL), polymyxin induction experiments revealed that 13% of the isolates acquired high-level resistance (MIC > 32 µg/mL) (Figure S1A). MALDI-TOF MS analysis of lipid A structures before and after polymyxin exposure showed disappearance of typical lipid peaks at m/z 1727.9145 and m/z 1911.0336, confirming structural alterations associated with resistance (Figure S1B).

3.3. Resistance Mechanisms of Multidrug-Resistant P. aeruginosa

Compared with other MDR bacteria, carbapenem-resistant P. aeruginosa carried fewer resistance genes and mobile genetic elements (Figure 3A). The P. aeruginosa strains WA8909 and WA8934 showed tigacycline resistance, likely due to overexpression of efflux systems such as MexXY-OprM, MexAB-OprM, and MexCD-OprJ [28]. Only WE4311 and WE4334 showed sensitivity to carbapenems. Seven strains, including WE1938, showed resistance characteristics typical of P. aeruginosa, as they are sensitive to antibiotics, except for imipenem, meropenem, and ertapenem. Through a comparative analysis of the whole genomes, we found that WE1938 and other sources of P. aeruginosa had similar chromosome structures and carried the same antibiotic resistance genes. WE1938 was classified as ST1025 and carried β-lactam (blaPAO, blaOXA-488), aminoglycoside (aph(3’)-IIb), chloramphenicol (catB7), fosfomycin (fosA), and ciprofloxacin (crpP) resistance genes. Despite this, the strains were still sensitive to ciprofloxacin and harbored MexAB-OprM and MexXY-OprM efflux pump, as well as the regulator genes mexR, nalC, nalD, and nfxB.
Comparative analysis of the oprD gene from isolate WE1983 revealed multiple deletions and mutations relative to the reference strain PAO1 (Figure 3B). Additionally, P. aeruginosa isolates carried genes related to bacterial motility and initial attachment, as well as the flagella and type IV pili biosynthesis and twitching motility (Table S3). WE1938 also possessed type III and type VI secretion systems, which transport virulence factors.

3.4. Genetic Context and Phylogenetic Characteristics of Carbapenem-Resistant Isolates Carrying blaNDM and blaKPC-2 Genes

Transferable carbapenem resistance genes, such as blaNDM and blaKPC, were detected in various carbapenem-resistant isolates collected from the hospital. Among the isolates—including E. coli, Enterobacter hormaechei, Klebsiella grimontii, P. aeruginosa, and A. pittii—four blaNDM alleles (blaNDM-1, blaNDM-4, blaNDM-5, and blaNDM-13) were identified. Notably, blaNDM-1 was consistently detected in non-fermenting isolates, and its genetic context was highly conserved and shared with multiple Enterobacteriaceae (Figure S2A). Within the Acinetobacter calcoaceticus–A. baumannii (Acb) complex, A. pittii isolate WA9063 (ST207) harbored blaNDM-1, with a conserved flanking region consisting of a truncated ISAba123 insertion sequence, and a conserved gene cassette (ble–trpF–dsbD–cutA–groES–groL–ISCR27) (Figure S2B).
Structural mapping revealed that these alleles were embedded within composite transposons flanked by IS30-like and IS91 family transposase elements, forming a flexible mobile module (Figure 4A). In contrast, all carbapenem-resistant K. pneumoniae isolates in this study harbored the blaKPC-2 gene within a highly conserved genetic environment. Unlike the classical Tn4401 arrangement, blaKPC-2 was found to reside within a non-Tn4401 composite structure. Notably, an IS481-like element was located upstream in the same orientation as blaKPC-2, while an IS1182-like element was inserted downstream in the opposite orientation (Figure 4B). The flanking regions of these structures were highly consistent across the isolates.
Phylogenetic analyses were performed on carbapenem-resistant and susceptible isolates. Maximum likelihood phylogenetic analysis revealed that blaNDM-positive E. coli isolates clustered closely with E. coli strains lacking the gene, indicating a potential risk of gene dissemination (Figure 4C), while blaKPC-2-positive K. pneumoniae strains formed a tight phylogenetic cluster, hinting at clonal expansion from a common ancestor (Figure 4D).

4. Discussion

The rising prevalence of carbapenem-resistant Gram-negative bacteria, including non-fermenters like A. baumannii and P. aeruginosa, as well as Enterobacteriaceae harboring mobile resistance genes such as blaNDM and blaKPC, poses a severe threat to clinical treatment and infection control [29,30]. Their resistance to “last-resort” antibiotics like carbapenems, polymyxin, or tigecycline, coupled with their high mobility and clonal dissemination of resistance determinants, highlights the urgent need for enhanced molecular surveillance and containment strategies in healthcare settings [31].
Whole-genome sequencing revealed phylogenetic clustering of MDR A. baumannii strains with highly similar resistance gene profiles, indicating likely nosocomial transmission, particularly in high-risk units such as the ICU and HPB Surgery [32,33]. Environmental persistence and transient colonization of healthcare workers may contribute to intra-hospital dissemination. The ability of A. baumannii to form biofilms further enhances its resistance and survival in clinical environments. Interestingly, certain strains (e.g., WE1499, WE2086, WE1502) lacked biofilm-related genes and exhibited increased antibiotic sensitivity, suggesting potential therapeutic targets. Moreover, in vitro polymyxin exposure revealed that even drugs of last resort could become ineffective under selective pressure, supported by lipid A modifications detected via MALDI-TOF MS [34].
In comparison, P. aeruginosa harbored fewer acquired resistance genes but relied heavily on intrinsic mechanisms, such as reduced membrane permeability and multidrug efflux pumps [35]. Mutations in the oprD porin gene were associated with decreased carbapenem susceptibility [36]. Virulence systems, including type III and VI secretion systems, flagella, pili, and siderophores such as pyoverdine, contribute to immune evasion, colonization, and biofilm development, compounding the challenge of treatment [37].
From a genomic perspective, comparative analyses of the carbapenemase genes blaNDM and blaKPC-2 revealed stark contrasts in their mobility and epidemiological behavior [21,23,38]. blaNDM was detected in a variety of hosts, including Enterobacteriaceae and non-fermenters, and embedded within mobile modules flanked by transposase elements, confirming its high transposition potential and inter-species transferability. The co-localization with conserved resistance-associated cassettes (bleMBL–trpF, etc.) further demonstrates its modularity and horizontal dissemination capacity [39,40]. The blaKPC-2 gene is typically located within the Tn4401 transposon bracketed by ISKpn6 and ISKpn7 elements, which are classical components associated with blaKPC-2 dissemination. However, in this study, blaKPC-2 was found exclusively in K. pneumoniae, located in a non-Tn4401 composite structure flanked by IS481-like and IS1182-like elements [41,42]. The consistent structural context and tight phylogenetic clustering of these strains suggest clonal transmission rather than frequent horizontal acquisition. Such structural variants of blaKPC-2 are increasingly reported in Asia and South America, pointing to region-specific dissemination pathways.
Together, these findings highlight two fundamentally different evolutionary strategies: blaNDM exhibits broad host plasticity and modular genetic architecture, requiring surveillance focused on mobile genetic elements; blaKPC-2, by contrast, spreads clonally within specific lineages, making clonal interruption a more viable control measure. Integrating resistance profiling with phylogenetic and structural data is therefore essential to tailor infection control efforts and limit the spread of MDR pathogens in healthcare settings.

5. Conclusions

This study highlights the alarming prevalence and complex epidemiology of MDR non-fermenting Gram-negative bacteria and carbapenemase-producing Enterobacteriaceae in nosocomial settings. Whole-genome and phylogenetic analyses revealed that blaNDM exhibits high genetic plasticity, disseminating across diverse species via mobile elements, while blaKPC-2 is predominantly clonally transmitted in K. pneumoniae through a non-Tn4401 composite structure. The widespread resistance, including to last-resort agents like tigecycline and polymyxin, emphasizes the urgent need for tailored molecular surveillance and targeted infection control strategies to prevent intra-hospital transmission.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/microbiolres16070147/s1, Figure S1: polymyxin-sensitive A. baumannii obtained a high polymyxin resistance phenotype after antibiotic induction, and further MALDI-TOF MS analysis showed lipid A deletion; Figure S2: (A) Analysis of the genetic background of the blaNDM-1 gene and the transmission of the blaNDM-1 gene structure among different bacteria. (B) Using BRIG to compare the chromosome sequences of A. pittii. Table S1: Strain information and antibiotic resistance characteristics of A. baumannii, A. pittii, and P. aeruginosa. Table S2: Resistant phenotype of multidrug-resistant A. baumannii. Table S3: The virulence gene carried by A. baumannii, A. pittii, and P. aeruginosa.

Author Contributions

W.Y., S.L., and W.S. contributed to the study conception and design. Material preparation, data collection, and analysis were performed by S.L., T.L., Z.L., and Z.P. The first draft of the manuscript was written by W.Y., J.Z., and W.S. All authors have read and agreed to the published version of the manuscript.

Funding

This research was supported by the Natural Science Foundation of Hebei Province, grant number H2024201044; Project of Hebei Education Department, grant number QN2021022; and The Medical Scientific Research of Hebei Health Commission, grant number 20231560.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data are provided in the article and Supplementary Materials. Genome assemblies can be accessed through the BioProject under project accession number: Acinetobacter baumannii, PRJNA1071068; Acinetobacter pittii, PRJNA1070990; Pseudomonas aeruginosa, PRJNA1070994.

Acknowledgments

We are very grateful to the Affiliated Hospital of Hebei University for providing the strains needed for the study.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. (A) The Sankey diagram displays strain information and antibiotic resistance characteristics of multidrug-resistant P. aeruginosa, A. pittii, and A. baumannii. (B) Antimicrobial susceptibility profiles of non-fermenting Gram-negative bacteria isolates. Note. Emergency Department: ED; intensive care unit: ICU; Integrated Traditional Chinese and Western Medicine Department: ITCM; Neurocritical Care Department: NCC; nephrology department: Neph; Pulmonary and Critical Care Medicine: PCCM; Rheumatology and Immunology Department: Rheum/Immuno Dept; Hepatobiliary and Pancreatic Surgery: HBP; Orthopedics Department: Ortho; Gastrointestinal Surgery Department: GI Surg.
Figure 1. (A) The Sankey diagram displays strain information and antibiotic resistance characteristics of multidrug-resistant P. aeruginosa, A. pittii, and A. baumannii. (B) Antimicrobial susceptibility profiles of non-fermenting Gram-negative bacteria isolates. Note. Emergency Department: ED; intensive care unit: ICU; Integrated Traditional Chinese and Western Medicine Department: ITCM; Neurocritical Care Department: NCC; nephrology department: Neph; Pulmonary and Critical Care Medicine: PCCM; Rheumatology and Immunology Department: Rheum/Immuno Dept; Hepatobiliary and Pancreatic Surgery: HBP; Orthopedics Department: Ortho; Gastrointestinal Surgery Department: GI Surg.
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Figure 2. (A) Comparison of multidrug-resistant and susceptible A. baumannii by evolutionary analysis of the core genome; (B) using BRIG to compare the chromosome sequences of multidrug-resistant A. baumannii.
Figure 2. (A) Comparison of multidrug-resistant and susceptible A. baumannii by evolutionary analysis of the core genome; (B) using BRIG to compare the chromosome sequences of multidrug-resistant A. baumannii.
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Figure 3. (A) Using BRIG to compare the chromosome sequences of multidrug-resistant P. aeruginosa. (B) Alignment of the amino acid sequences of OprD porin from reference strain PAO1 with WE1938.
Figure 3. (A) Using BRIG to compare the chromosome sequences of multidrug-resistant P. aeruginosa. (B) Alignment of the amino acid sequences of OprD porin from reference strain PAO1 with WE1938.
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Figure 4. (A) Analysis of the genetic background of bacteria carrying the blaNDM gene; (B) analysis of the genetic background of bacteria carrying the blaKPC-2 gene; (C,D) comparison of multidrug-resistant and -susceptible E. coli and K. pneumoniae by evolutionary anFalysis of the core genome.
Figure 4. (A) Analysis of the genetic background of bacteria carrying the blaNDM gene; (B) analysis of the genetic background of bacteria carrying the blaKPC-2 gene; (C,D) comparison of multidrug-resistant and -susceptible E. coli and K. pneumoniae by evolutionary anFalysis of the core genome.
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MDPI and ACS Style

Liao, S.; Su, W.; Li, T.; Li, Z.; Pei, Z.; Zhang, J.; Yin, W. The Nosocomial Transmission of Carbapenem-Resistant Gram-Negative Bacteria in a Hospital in Baoding City, China. Microbiol. Res. 2025, 16, 147. https://doi.org/10.3390/microbiolres16070147

AMA Style

Liao S, Su W, Li T, Li Z, Pei Z, Zhang J, Yin W. The Nosocomial Transmission of Carbapenem-Resistant Gram-Negative Bacteria in a Hospital in Baoding City, China. Microbiology Research. 2025; 16(7):147. https://doi.org/10.3390/microbiolres16070147

Chicago/Turabian Style

Liao, Shengnan, Wei Su, Tianjiao Li, Zeyang Li, Zihan Pei, Jie Zhang, and Wenjuan Yin. 2025. "The Nosocomial Transmission of Carbapenem-Resistant Gram-Negative Bacteria in a Hospital in Baoding City, China" Microbiology Research 16, no. 7: 147. https://doi.org/10.3390/microbiolres16070147

APA Style

Liao, S., Su, W., Li, T., Li, Z., Pei, Z., Zhang, J., & Yin, W. (2025). The Nosocomial Transmission of Carbapenem-Resistant Gram-Negative Bacteria in a Hospital in Baoding City, China. Microbiology Research, 16(7), 147. https://doi.org/10.3390/microbiolres16070147

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