Polymorphisms of Gene Cassette Promoters of the Class 1 Integron in Clinical Proteus Isolates

Association analysis of antibiotic and disinfectant resistome in human and foodborne E. coli in Beijing, China

The widespread use of chemical disinfectants and antibiotics poses a major threat to food safety and human health. However, the mechanisms of co-transmission of antimicrobial resistance genes (ARGs) and biocides and metal resistance genes (BMRGs) of foodborne pathogens in the food chain is still unclear. This study isolated 343 E. coli strains from animal-derived foods in Beijing and incorporated online data of human-derived E. coli strains from NCBI. Our results demonstrated a relatively uniform distribution of strains from various regions in Beijing, indicating a lack of region-specific clustering. Additionally, predominant sequence types varied between food- and human-derived strains, suggesting a preference for different hosts and environments. Phenotypic association analysis showed that the chlorine disinfectants peroxides had a significant positive correlation with tetracyclines. Many more ARGs and BMRGs were enriched in human-associated E. coli compared with those in chicken- and pork-origin. The quaternary ammonium compounds (QACs) resistance gene qacEΔ1 had a strong correlation with aminoglycoside resistance gene aadA5, folate pathway antagonist resistance gene dfrA17, sul1 and macrolide resistance gene mph(A). The correlation results indicated a significant association between the copper resistance gene cluster pco and the silver resistance gene cluster sil. Coexistence of many resistance genes was observed within the qacEΔ1 gene structure, with qacEΔ1-sul1 being the most common combination. Our findings demonstrated that the epidemiological spread of resistance is affected by a combination of heavy metals, disinfectants and antibiotic use, suggesting that the prevention and control strategies of antimicrobial resistance need to be multifaceted and comprehensive.

Genetic characteristics of chromosomally integrated carbapenemase gene (blaNDM-1) in isolates of Proteus mirabilis

OBJECTIVE

This study aims to conduct an in-depth genomic analysis of a carbapenem-resistant Proteus mirabilis strain to uncover the distribution and mechanisms of its resistance genes.

METHODS

The research primarily utilized whole-genome sequencing to analyze the genome of the Proteus mirabilis strain. Additionally, antibiotic susceptibility tests were conducted to evaluate the strain's sensitivity to various antibiotics, and related case information was collected to analyze the clinical distribution characteristics of the resistant strain.

RESULTS

Study on bacterial strain WF3430 from a tetanus and pneumonia patient reveals resistance to multiple antibiotics due to extensive use. Whole-genome sequencing exposes a 4,045,480 bp chromosome carrying 29 antibiotic resistance genes. Two multidrug-resistant (MDR) gene regions, resembling Tn6577 and Tn6589, were identified (MDR Region 1: 64.83 Kb, MDR Region 2: 85.64 Kbp). These regions, consist of integrative and conjugative elements (ICE) structures, highlight the intricate multidrug resistance in clinical settings.

CONCLUSION

This study found that a CR-PMI strain exhibits a unique mechanism for acquiring antimicrobial resistance genes, such as blaNDM-1, located on the chromosome instead of plasmids. According to the results, there is increasing complexity in the mechanisms of horizontal transmission of resistance, necessitating a comprehensive understanding and implementation of targeted control measures in both hospital and community settings.

Commensal Fitness Advantage May Contribute to the Global Dissemination of Multidrug-Resistant Lineages of Bacteria-The Case of Uropathogenic E. coli

It is widely accepted that favorable fitness in commensal colonization is one of the prime facilitators of clonal dissemination in bacteria. The question arises as to what kind of fitness advantage may be wielded by uropathogenic strains of the two predominant fluoroquinolone- and multidrug-resistant clonal groups of E. coli-ST131-H30 and ST1193, which has permitted their unprecedented pandemic-like global expansion in the last few decades. The colonization-associated genes' content, carriage of low-cost plasmids, and integrons with weak promoters could certainly contribute to the fitness of the pandemic groups, although those genetic factors are common among other clonal groups as well. Also, ST131-H30 and ST1193 strains harbor fluoroquinolone-resistance conferring mutations targeting serine residues in DNA gyrase (GyrA-S83) and topoisomerase IV (ParC-S80) that, in those clonal backgrounds, might result in a commensal fitness benefit, i.e., beyond the antibiotic resistance per se. This fitness gain might have contributed not only to the widespread dissemination of these major clones in the healthcare setting but also to their long-term colonization of healthy individuals and, thus, circulation in the community, even in a low or no fluoroquinolone use environment. This evolutionary shift affecting commensal E. coli, initiated by mutations co-favorable in both antibiotics-treated patients and healthy individuals warrants more in-depth studies to monitor further changes in the epidemiological situation and develop effective measures to reduce the antibiotic resistance spread.

Prevalence, molecular characterization of integrons and its associated gene cassettes in Klebsiella pneumoniae and K. oxytoca recovered from diverse environmental matrices

The high prevalence of infections arising from Klebsiella species is related to their ability to acquire and disseminate exogenous genes associated with mobile genetic elements such as integrons. We assessed the prevalence, diversity, and associated gene cassettes (GCs) of integrons in Klebsiella species. The isolates recovered from wastewater and hospital effluents, rivers, and animal droppings were identified using the conventional Polymerase Chain Reaction (PCR) with primers targeting the gryA, pehX, and 16S-23S genes. The antimicrobial resistance profile and the Extended-Spectrum and Metallo β-lactamases production were carried out using standard microbiological techniques. PCR, DNA sequencing analyses, and Restriction Fragment Length Polymorphism were used to characterize the integrons and their associated GCs. Furthermore, the genotypic relationships between the different isolated K. pneumoniae were determined using Enterobacterial Repetitive Intergenic Consensus (ERIC)-PCR. About 98% (51/52) of the confirmed isolates harboured an integrase gene, with 80% intI1, while the remaining 20% concurrently harboured intI1 and intI2, with no intI3 observed. About 78% (40/51) of the bacterial strains were positive for a promoter, the P2R2, investigated, while 80% (41/51) harboured at least one of the qacEΔ1 and sul1. Three different GCs arrangements identified were aac(6')-Ib, aadA1-dfrA1, and dfrA1-sat2. At a similarity index of 60%, the ERIC-PCR fingerprints generated were categorized into nine clusters. Our study is the first to reveal the features of integrons in Klebsiella spp. recovered from environmental sources in the Eastern Cape Province, South Africa. We conclude that the organisms' sources are repositories of integrons harbouring various gene cassettes, which can be readily mobilized to other microorganisms in similar or varied niches.

Molecular characterization of class 1 integrons in carbapenem-resistant Enterobacterales isolates

OBJECTIVE

Carbapenem-resistant Enterobacterales (CRE) infections result in higher treatment costs and mortality rates. Integrons play important roles in emergence and spread of antibiotic resistant genes. To get a better understand on the effects of integron on CRE resistance, distribution of common carbapenemase genes and class 1 integron in clinical CRE isolates were investigated.

METHOD

Carbapenemase genes, including bla_KPC, bla_VIM, bla_IMP, bla_NDM, bla_GES, bla_VEB and bla_OXA-23, were screened in 161 CRE isolates and subtypes of these genes were confirmed through sequence analysis. Class 1 integron was screened and common promoter and gene cassette arrays were determined by sequencing. The resistant rates to clinical commonly used antibiotics between integron positive and integron negative CRE isolates were compared.

RESULTS

Of 161 CRE isolates, the most prevalent carbapenemase gene was bla_KPC-2, which was detected in 139 isolates, including 99 Klebsiella pneumoniae. Class 1 integron was detected in 78 isolates. Twenty different gene cassettes, including two carbapenemase genes bla_VEB-1 and bla_IMP-4, and nine different gene cassette arrays, including bla_VEB-1-aadB-arr-2-cmlA5-bla_OXA-10-aadA1, aadB-catB8-bla_OXA-10-aadA1-dfrA1-aacA4 and bla_IMP-4-qacG-aacA4-catB3, were detected. Five types of common promoters were identified. Relative weak promoter PcH1 was the dominant type. Resistant rates of CRE isolates containing class 1 integrons to ceftazidime, amikacin, trimethoprim/sulfamethoxazole and gentamicin were higher than those without class 1 integrons (P < 0.05).

CONCLUSION

Class 1 integrons play important roles in the emergence and spread of CRE resistance. To the best of our knowledge, this is the first report of aadB-catB8-bla_OXA-10-aadA1-dfrA1-aacA4 and bla_IMP-4-qacG-aacA4-catB3 in the same Providencia rettgeri isolate and bla_VEB-1-aadB-arr-2-cmlA5-bla_OXA-10-aadA1 in P. rettgeri.

Antimicrobial Resistance and Molecular Characterization of Gene Cassettes from class 1 Integrons in Carbapenem-resistant Escherichia coli strains

OBJECTIVE

To investigate the distribution of class 1 integrons and their variable regional molecular characteristics, as well as the diversity of promoter and drug sensitivity of CR-Eco (carbapenem-resistant E. coli) strains.

METHOD

A total of 117 CR-Eco strains, collected between 2012.01 and 2019.12, underwent fully automated bacterial identification and sensitization using VITEK-2 Compact and supplemented by K-B assay. PCR was employed to screen for class 1 integrase genes and integron variable regions, while the promoter type and variable region gene cassette characteristics were determined by sequencing analysis.

RESULTS

The positive rate of the class 1 integron of the CR-Eco strains was 83.70% (92/117) herein. Moreover, class 1 integrase-positive strains exhibited statistically significant resistance to aztreonam, ceftazidime, ciprofloxacin, ceftriaxone, gentamicin, meropenem, and trimethoprim-sulfamethoxazole compared to integron-negative strains (P < 0.05). Variable regions were observed in 77 of the 92 class 1 integrase-positive strains. In addition, seven gene cassettes were detected, namely dfrA17-aadA5, aadA22, dfrA12-aadA2, dfrA12, dfrA17, dfrA27 and aadA. Finally, five types of class 1 integron variable region promoters were identified in those 77 strains, including PcW, PcH1, PcW_TGN-10, PcH1_TGN-10, and P2, which were detected in 48, 18, 8, 2, and 1 strains, respectively.

CONCLUSION

The primary integrator variable region gene cassettes of this class were dfrA and aadA. The integron-positive strains displayed simultaneous high resistance to multiple antimicrobial drugs. The integrator variable region promoters of the CR-Eco strains are primarily weak and can potentially form and spread drug resistance.

Distribution and Molecular Characterization of Functional Class 2 Integrons in Clinical Proteus mirabilis Isolates

Background

Integrons are the main mode of horizontal transmission of drug-resistance genes and are closely related to drug resistance in clinical bacteria. In this study, the distributions of class 1, 2, and 3 integron gene cassettes were investigated in 150 Proteus mirabilis (P. mirabilis) isolates from patients, and molecular characterization of functional class 2 integrons was further analyzed.

Methods

Class 1, 2, and 3 integrons were screened by polymerase chain reaction (PCR) in 150 clinical P. mirabilis isolates. The variable regions of the integrons were determined by restriction analysis and sequencing. Internal stop codons mutations in class 2 integrons and their common promoters were also determined by sequencing. Enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC-PCR) was used to analyze the phylogenetic relations of class 2 integron-positive isolates.

Results

Class 1 integrons were detected in 69 (46%) of 150 P. mirabilis isolates, and six different gene cassette arrays were detected, with the most prevalent being dfrA32-aadA2. Class 2 integrons were detected in 61 (40.7%) of 150 P. mirabilis isolates, and three different gene cassette arrays were detected, including sat2-aadA1, which was detected for the first time in a class 2 integron. Nearly similar ERIC-PCR fingerprinting patterns were detected in 45 (73.8%) of 61 class 2 integron-positive isolates. The functional class 2 integron was detected in three P. mirabilis isolates having the same gene cassette, dfrA1-sat2-aadA1, in the variable region and four novel open reading frames with unknown functions. Same PintI2 and Pc promoters were detected in these three functional class 2 integron isolates, as was found in other class 2 integron isolates. However, these three strains did not totally show identical homology and drug sensitivity.

Conclusion

Although functional class 2 integrons have low distribution and relatively conserved molecular characteristics, they can still form clinical dissemination and drug resistance expression.

Integron Functionality and Genome Innovation: An Update on the Subtle and Smart Strategy of Integrase and Gene Cassette Expression Regulation

Integrons are considered hot spots for bacterial evolution, since these platforms allow one-step genomic innovation by capturing and expressing genes that provide advantageous novelties, such as antibiotic resistance. The acquisition and shuffling of gene cassettes featured by integrons enable the population to rapidly respond to changing selective pressures. However, in order to avoid deleterious effects and fitness burden, the integron activity must be tightly controlled, which happens in an elegant and elaborate fashion, as discussed in detail in the present review. Here, we aimed to provide an up-to-date overview of the complex regulatory networks that permeate the expression and functionality of integrons at both transcriptional and translational levels. It was possible to compile strong shreds of evidence clearly proving that these versatile platforms include functions other than acquiring and expressing gene cassettes. The well-balanced mechanism of integron expression is intricately related with environmental signals, host cell physiology, fitness, and survival, ultimately leading to adaptation on the demand.

Prevalence and characterization of antibiotic resistance genes and integrons in Escherichia coli isolates from captive non-human primates of 13 zoos in China

Antimicrobial resistance (AMR) has become a public health concern; but antibiotic resistance genes (ARGs) and integrons that link to AMR of Escherichia coli from non-human primates remain largely unknown. This study aimed to investigate antibiotic resistance, emerging environmental pollutants ARGs, and integrons factors (intI1, intI2 and intI3) in 995 E. coli isolates obtained from 50 species of captive non-human primates of 13 zoos in China. Our result showed 83.62% of the E. coli isolates were resistant to at least one antibiotic and 47.94% isolates showed multiple drug resistances (MDR). The E. coli isolates mainly showed resistance to tetracycline (tetracycline 62.71%, doxycycline 61.11%), β-lactams (ampicillin 54.27%, amoxicillin 52.36%), and sulfonamide (trimethoprim-sulfamethoxazole 36.78%). A total of 423 antibiotic resistance patterns were observed, of which DOX/TET (49 isolates, 4.92%) was the most common pattern. Antibiotic resistance rates among 13 zoos had a significant difference (P < 0.01). We further detected 22 ARGs in the 995 E. coli isolates, of which tetA had the highest occurrence (70.55%). The presence of integrons class 1 and 2 were 24.22% and 1.71%, respectively, while no class 3 integron was found. Significant positive associations were observed among integrons and antibiotics, of which the strongest association was observed for integrons / Gentamicin (OR, 2.642) and integrons / Cefotaxime (OR, 2.512). In addition, cassette arrays were detected in 64 strains of class 1 integron-positive isolates (26.56%) and 10 strains of class 2 integron-positive isolates (58.82%). Eighteen cassette arrays were found within 64 class 1 integron isolates, while 3 cassette arrays were identified within 10 class 2 integron isolates. Our results indicate a high diversity of antibiotic resistance phenotypes in non-human primate E. coli isolates, which carry multiple ARGs and integrons. Corresponding preventive measures should be taken to prevent the spread of integron-mediated ARGs in non-human primates and their living environments in zoos.

Global Evolution of Pathogenic Bacteria With Extensive Use of Fluoroquinolone Agents

It is well-established that the spread of many multidrug-resistant (MDR) bacteria is predominantly clonal. Interestingly the international clones/sequence types (STs) of most pathogens emerged and disseminated during the last three decades. Strong experimental evidence from multiple laboratories indicate that diverse fitness cost associated with high-level resistance to fluoroquinolones contributed to the selection and promotion of the international clones/STs of hospital-associated methicillin-resistant Staphylococcus aureus (HA-MRSA), extended-spectrum β-lactamase-(ESBL)-producing Klebsiella pneumoniae, ESBL-producing Escherichia coli and Clostridioides difficile. The overwhelming part of the literature investigating the epidemiology of the pathogens as a function of fluoroquinolone use remain in concordence with these findings. Moreover, recent in vitro data clearly show the potential of fluoroquinolone exposure to shape the clonal evolution of Salmonella Enteritidis. The success of the international clones/STs in all these species was linked to the strains' unique ability to evolve multiple energetically beneficial gyrase and topoisomerase IV mutations conferring high-level resistance to fluorquinolones and concomittantly permitting the acquisition of an extra resistance gene load without evoking appreciable fitness cost. Furthermore, by analyzing the clonality of multiple species, the review highlights, that in environments under high antibiotic exposure virulence factors play only a subsidiary role in the clonal dynamics of bacteria relative to multidrug-resistance coupled with favorable fitness (greater speed of replication). Though other groups of antibiotics should also be involved in selecting clones of bacterial pathogens the role of fluoroquinolones due to their peculiar fitness effect remains unique. It is suggested that probably no bacteria remain immune to the influence of fluoroquinolones in shaping their evolutionary dynamics. Consequently a more judicious use of fluoroquinolones, attuned to the proportion of international clone/ST isolates among local pathogens, would not only decrease resistance rates against this group of antibiotics but should also ameliorate the overall antibiotic resistance landscape.

Characterization of Beta-Lactamases in Bloodstream-Infection Escherichia coli: Dissemination of blaADC - 162 and blaCMY- 2 Among Bacteria via an IncF Plasmid

OBJECTIVES

To describe the molecular characteristics of beta-lactamases in bloodstream-infection Escherichia coli isolated from elderly patients, and to determine the genotypic patterns of bla CMY - 2 and bla ADC - 162.

METHODS

A total of 50 bloodstream-infection E. coli isolates were obtained from patients aged > 50 years at Shanghai Sixth People's Hospital South Campus during 2015-2018. The isolates were subjected to beta-lactamase detection using phenotypic and molecular methods. Beta-lactamase genes were verified by sequencing and the phylogenetic relationships of the isolates were analyzed by multilocus sequence typing (MLST). The transferability of plasmids carrying bla CMY- 2 and bla ADC- 162 genes was verified by conjugation experiments and plasmid replicon typing.

RESULTS

Eight beta-lactamase subtypes were detected in 50 isolates of bloodstream-infection E. coli. bla TEM- 1 (21/50) was the most common beta-lactamase gene, followed by bla CTX-M- 14 (8/50), bla OXA- 27 (5/50), bla CTX-M- 27 (3/50), bla CTX-M- 65 (1/50), bla ADC- 162 (1/50), and bla CMY- 2 (1/50). Of these, bla ADC- 162 (ST95-A), and bla CMY- 2 (ST95-B2) have not previously been reported in bloodstream-infection E. coli. In 21 isolates, beta-lactamase genes were located on conjugative plasmids belonging to incompatibility groups FrepB (n = 7), FIA (n = 1), FIC (n = 2), K (n = 8), N (n = 1), and I (n = 1), and bla CTX-M was associated with the common elements ISEcp1, IS903, and IS26, but with special sequences (region V, region Y, and region W) for ISEcp1 in 14 isolates.

CONCLUSION

To the best of our knowledge, this study provides the first molecular characterization of beta-lactamase genes in E. coli isolated from the bloodstream in elderly patients. Beta-lactamase genes were detected at a relatively high frequency in elderly patients with bloodstream E. coli infections. Plasmid replicon analysis showed that horizontal dissemination of beta-lactamase genes was mainly mediated by IncK and IncF plasmids, which could encode multidrug resistance genes. The study also provides the first report of ISAba1-bla ADC - 162-tnpA and ISEcp1-bla CTX-M- 14-IS903-bla CMY- 2-blc-sugE in E. coli, and demonstrates IncF plasmid-mediated bla ADC - 162 and bla CMY- 2 gene dissemination among bacteria.