Resistance to quinolones, cephalosporins and macrolides in Escherichia coli causing bacteraemia in Peruvian children

Recent Updates on Antibacterial Quinolones: Green Synthesis, Mode of Interaction and Structure-Activity Relationship

Quinolone antibiotics are a crucial class of synthetic antibacterial agents, widely utilized due to their broad spectrum of antibacterial activity. Due to the development of antimicrobial resistance, the potency of quinolone drugs decreased. Many conventional methods have been developed to elevate amination rate and to improve yield. These methods are generally characterized by prolonged reaction durations, high boiling solvents, harsh conditions, costly reagents and excessive heat generation, which have adversely affected the therapeutic efficacy of these compounds. Recently, green chemistry has focused on sustainable chemistry-dependent quinolone analogue synthesis methods that significantly reduce bacterial infections. These methods include one-pot synthesis, photoredox catalysis, phase transfer catalysis, ultrasonic irradiation, microwave-assisted, green solvent and catalyst-free synthesis, which often utilize energy-efficient, non-toxic and less time-consuming techniques, aligning with green chemistry principles to improve safety and environmental impact. Researchers continuously explore innovative approaches to applying these methods in synthetic reactions. This review includes a comprehensive analysis of synthetic literature from the past 15 years from Scopus, PubMed, Embase and WOS using keywords, such as green chemistry, quinolone and antibacterial, highlighting significant advancements and emerging trends. This work's importance lies in its extensive literature overview on green synthesis methods for quinolones and related heterocyclic compounds. Furthermore, to provide useful information for the generation of future antibacterial drugs, some structural-activity relationship studies and in silico studies have also been included to investigate the stable binding interactions between quinolone leads and various target proteins.

Resistance to cephalosporins and quinolones in Escherichia coli isolated from irrigation water from the Rímac river in east Lima, Peru

OBJECTIVES.

To evaluate the presence and sensitivity to antimicrobials of Escherichia coli strains isolated from 24 irrigation water samples from the Rimac river of East Lima, Peru.

MATERIALS AND METHODS.

The E. coli strains were identified by PCR. Antibiotic susceptibility was processed by the disk diffusion method. Genes involved in extended spectrum beta-lactamases (BLEE), quinolones and virulence were determined by PCR.

RESULTS.

All samples exceeded the acceptable limits established in the Environmental Quality Standards for vegetable irrigation. Of the 94 isolates, 72.3% showed resistance to at least one antibiotic, 24.5% were multidrug resistant (MDR) and 2.1% were extremely resistant. The highest percentages of resistance were observed for ampicillin-sulbactam (57.1%), nalidixic acid (50%), trimethoprim-sulfamethoxazole (35.5%) and ciprofloxacin (20.4%). Among the isolates, 3.2% had a BLEE phenotype related to the bla CTX-M-15 gene. qnrB (20.4%) was the most frequent transferable mechanism of resistance to quinolones, and 2.04% had qnrS. It was estimated that 5.3% were diarrheagenic E. coli and of these, 60% were enterotoxigenic E. coli, 20% were enteropathogenic E. coli and 20% were enteroaggregative E. coli.

CONCLUSIONS.

The results show the existence of diarrheogenic pathotypes in the water used for irrigation of fresh produce and highlight the presence of BLEE- and MDR-producing E. coli, demonstrating the role played by irrigation water in the dissemination of resistance genes in Peru.

Motivation for the study. Aquatic systems, including irrigation water, have been identified as reservoirs of antimicrobial resistance, with few studies in Peru on the presence of Escherichia coli and their levels of virulence and antimicrobial resistance. Main findings. Our results show the presence of E. coli above the established standard for vegetable irrigation water, some with very high levels of antimicrobial resistance. Implications. The presence of ESBL-producing strains of extended-spectrum beta-lactamases and multidrug-resistant E. coli in irrigation water could contribute to the dissemination of resistance genes in Peru, posing a significant threat to public health.

Pons M. Antimicrobial resistance and associated risk factors in Escherichia coli isolated from Peruvian dogs: A focus on extended-spectrum β-lactamases and colistin

Background and Aim

Established antimicrobial resistance (AMR) surveillance in companion animals is lacking, particularly in low-middle-income countries. The aim of this study was to analyze AMR and its risk factors in Escherichia coli isolated from dogs at two veterinary centers in Lima (Peru).

Materials and Methods

Ninety dogs were included in the study. Antimicrobial susceptibility was established by disk diffusion, whereas microdilution was used to determine colistin susceptibility. Mechanisms related to extended-spectrum β-lactamases (ESBL) and colistin resistance were determined by polymerase chain reaction. Clonal relationships of colistin-resistant isolates were assessed by XbaI-pulsed-field gel electrophoresis.

Results

Thirty-five E. coli strains were isolated. High levels of resistance to ampicillin (57.1%), nalidixic acid (54.3%), tetracycline (48.6%), and azithromycin (25.7%) were detected. Cephalosporin resistance levels were ≥20% and those for colistin were 14.3%. Twelve (34.2%) isolates were ESBL producers; of these, six blaCTX-M-55 (50.0%), 2 (16.6%) blaCTX-M-15, and 2 (16.6%) blaCTX-M-8-like genes were found. The five colistin-resistant isolates were clonally unrelated, with four of them presenting amino acid codon substitutions in the mgrB gene (V8A) or mutations in the mgrB promoter (a12g, g98t, and c89t). Furthermore, dog age, <6 years (p = 0.027) and raw diet (p = 0.054) were associated with resistance to a greater number of antibiotic families.

Conclusion

Despite small number of samples included, the study found that dogs studied were carriers of multidrug-resistant E. coli, including last-resort antimicrobials, representing a public health problem due to close contact between dogs and humans. This issue suggests the need for larger studies addressed to design strategies to prevent the spread of resistant micro-organisms in small animal clinics and domestic settings.

Effects of breastfeeding on children's gut colonization with multidrug-resistant Enterobacterales in peri-urban Lima, Peru

Children living in low-resource settings are frequently gut-colonized with multidrug-resistant bacteria. We explored whether breastfeeding may protect against children's incident gut colonization with extended-spectrum beta-lactamase-producing Escherichia coli (ESBL-Ec) and Klebsiella, Enterobacter, or Citrobacter spp. (ESBL-KEC). We screened 937 monthly stool samples collected from 112 children aged 1-16 months during a 2016-19 prospective cohort study of enteric infections in peri-urban Lima. We used 52,816 daily surveys to examine how exposures to breastfeeding in the 30 days prior to a stool sample were associated with children's risks of incident gut-colonization, controlling for antibiotic use and other covariates. We sequenced 78 ESBL-Ec from 47 children to explore their diversity. Gut-colonization with ESBL-Ec was increasingly prevalent as children aged, approaching 75% by 16 months, while ESBL-KEC prevalence fluctuated between 18% and 36%. Through 6 months of age, exclusively providing human milk in the 30 days prior to a stool sample did not reduce children's risk of incident gut-colonization with ESBL-Ec or ESBL-KEC. From 6 to 16 months of age, every 3 additional days of breastfeeding in the prior 30 days was associated with 6% lower risk of incident ESBL-Ec gut-colonization (95% CI: 0.90, 0.98, p = .003). No effects were observed on incident ESBL-KEC colonization. We detected highly diverse ESBL-Ec among children and few differences between children who were predominantly breastfed (mean age: 4.1 months) versus older children (10.8 months). Continued breastfeeding after 6 months conferred protection against children's incident gut colonization with ESBL-Ec in this setting. Policies supporting continued breastfeeding should be considered in efforts to combat antibiotic resistance.

Traditional marketed meats as a reservoir of multidrug-resistant Escherichia coli

This study aimed to analyze Escherichia coli from marketed meat samples in Peru. Sixty-six E. coli isolates were recovered from 21 meat samples (14 chicken, 7 beef), and antimicrobial resistance levels and the presence of mechanisms of antibiotic resistance, as well as clonal relationships and phylogeny of colistin-resistant isolates, were established. High levels of antimicrobial resistance were detected, with 93.9% of isolates being multi-drug resistant (MDR) and 76.2% of samples possessing colistin-resistant E. coli; of these, 6 samples from 6 chicken samples presenting mcr-1-producer E. coli. Colistin-resistant isolates were classified into 22 clonal groups, while phylogroup A (15 isolates) was the most common. Extended-spectrum β-lactamase- and pAmpC-producing E. coli were found in 18 and 8 samples respectively, with blaCTX-M-55 (28 isolates; 16 samples) and blaCIT (8 isolates; 7 samples) being the most common of each type. Additionally, blaCTX-M-15, blaCTX-M-65, blaSHV-27, blaOXA-5/10-like, blaDHA, blaEBC and narrow-spectrum blaTEM were detected. In addition, 5 blaCTX-M remained unidentified, and no sought ESBL-encoding gene was detected in other 6 ESBL-producer isolates. The tetA, tetE and tetX genes were found in tigecycline-resistant isolates. This study highlights the presence of MDR E. coli in Peruvian food-chain. The high relevance of CTX-M-55, the dissemination through the food-chain of pAmpC, as well as the high frequency of unrelated colistin-resistant isolates is reported.

Class 1 and 2 Integrons in Escherichia coli Strains Isolated from Diarrhea and Bacteremia in Children Less Than 2 Years of Age from Peru

Class 1 and Class 2 integrons are mobilizable elements able to carry a variety of antibiotic resistance determinants. In the present study, Class 1 and 2 integrons present in 355 pathogenic Escherichia coli (285 diarrheagenic, of these 129 were enteropathogenic, 90 enteroaggregative, 66 enterotoxigenic, and 70 bacteremic) isolated from healthy and ill children under age 5 from periurban areas of Lima, Peru, were characterized. The presence of integrase 1 and 2 was established by polymerase chain reaction (PCR), and variable regions were grouped by PCR-restriction fragment length polymorphism and subsequent sequencing. Antimicrobial resistance was established by disk diffusion. Ninety-seven isolates (27.3%) presented integrase 1, and 16 (4.5%) presented integrase 2 (P < 0.0001); in addition, seven (2.0%) isolates, six diarrheagenic and one bacteremic, presented both integrase genes. The presence of integrase 1 was more frequent among bacteremic isolates (P = 0.0004). Variable regions were amplified in 76/120 (63.3%) isolates with up to 14 gene arrangements. The most prevalent gene cassettes were those encoding dihydrofolate reductases as well as aminoglycoside modifying enzymes. Of note, Class 1 integrons tended to be associated with the presence of extended-spectrum β-lactamases (ESBLs). A variety of Class 1 and 2 integrons were detected in diarrheagenic and bacteremic E. coli, demonstrating the heterogeneity of variable regions circulating in the area. The association of integrons with ESBLs is worrisome and has an impact on the development of multidrug resistance.

Resistance to Fluoroquinolones in Pseudomonas aeruginosa from Human, Animal, Food and Environmental Origin: The Role of CrpP and Mobilizable ICEs

Fluoroquinolone resistance and the associated genetic mechanisms were assessed by antimicrobial susceptibility and whole genome sequencing in 56 Pseudomonas aeruginosa strains from human, animal, food and environmental origins. P. aeruginosa PAO1, PA7 and PA14 reference strains were also included in the study. Twenty-two strains (37%) were resistant to, at least, one fluoroquinolone agent. Correlation between the number of changes in GyrA and ParC proteins and the level of fluoroquinolone resistance was observed. Mutations or absence of genes, such as mexZ, mvaT and nalD encoding efflux pumps regulators, were also found in resistant strains. The crpP gene was detected in 43 strains (72.9%; 17 of them non-clinical strains), and coded seven different CrpP variants, including a novel one (CrpP-7). The crpP gene was located in 23 different chromosomal mobile integrative and conjugative elements (ICEs), inserted in two tRNAs integration sites. A great variety of structures was detected in the crpP-ICEs elements, e.g., the fimbriae related cup clusters, the mercury resistance mer operon, the pyocin S5 or S8 bacteriocin encoding genes, and mobilization genes. The location of crpP-like genes in mobilizable ICEs and linked to heavy metal resistance and virulence factors is of significant concern in P. aeruginosa. This work provides a genetic explanation of the fluoroquinolone resistance and crpP-associated pathogenesis of P. aeruginosa from a One-Health approach.

Antibiotic susceptibility among non-clinical Escherichia coli as a marker of antibiotic pressure in Peru (2009-2019): one health approach

Objective

Antimicrobial resistance is an increasing health problem worldwide with serious implications in global health. The overuse and misuse of antimicrobials has resulted in the spread of antimicrobial-resistant microorganisms in humans, animals and the environment. Surveillance of antimicrobial resistance provides important information contributing to understanding dissemination within these environments. These data are often unavailable in low- and middle-income countries, such as Peru. This review aimed to determine the levels of antimicrobial resistance in non-clinical Escherichia coli beyond the clinical setting in Peru.

Methods

We searched 2009-2019 literature in PUBMED, Google Scholar and local repositories.

Results

Thirty manuscripts including human, food, environmental, livestock, pets and/or wild animals' samples were found. The analysis showed high resistance levels to a variety of antimicrobial agents, with >90% of resistance for streptomycin and non-extended-spectrum cephalosporin in livestock and food. High levels of rifamycin resistance were also found in non-clinical samples from humans. In pets, resistance levels of 70->90% were detected for quinolones tetracycline and non-extended spectrum cephalosporins. The results suggest higher levels of antimicrobial resistance in captive than in free-ranging wild-animals. Finally, among environmental samples, 50-70% of resistance to non-extended-spectrum cephalosporin and streptomycin was found.

Conclusions

High levels of resistance, especially related to old antibacterial agents, such as streptomycin, 1st and 2nd generation cephalosporins, tetracyclines or first-generation quinolones were detected. Antimicrobial use and control measures are needed with a One Health approach to identify the main drivers of antimicrobial resistance due to interconnected human, animal and environmental habitats.

Molecular Characterization of Salmonella Detected along the Broiler Production Chain in Trinidad and Tobago

This cross-sectional study determined the serovars, antimicrobial resistance genes, and virulence factors of Salmonella isolated from hatcheries, broiler farms, processing plants, and retail outlets in Trinidad and Tobago. Salmonella in silico serotyping detected 23 different serovars where Kentucky 20.5% (30/146), Javiana 19.2% (28/146), Infantis 13.7% (20/146), and Albany 8.9% (13/146) were the predominant serovars. There was a 76.0% (111/146) agreement between serotyping results using traditional conventional methods and whole-genome sequencing (WGS) in in silico analysis. In silico identification of antimicrobial resistance genes conferring resistance to aminoglycosides, cephalosporins, peptides, sulfonamides, and antiseptics were detected. Multidrug resistance (MDR) was detected in 6.8% (10/146) of the isolates of which 100% originated from broiler farms. Overall, virulence factors associated with secretion systems and fimbrial adherence determinants accounted for 69.3% (3091/4463), and 29.2% (1302/4463) counts, respectively. Ten of 20 isolates of serovar Infantis (50.0%) showed MDR and contained the bla_CTX-M-65 gene. This is the first molecular characterization of Salmonella isolates detected along the entire broiler production continuum in the Caribbean region using WGS. The availability of these genomes will help future source tracking during epidemiological investigations associated with Salmonella foodborne outbreaks in the region and worldwide.

Long-term maintenance of multidrug-resistant Escherichia coli carried by vampire bats and shared with livestock in Peru

Extended-spectrum beta-lactamase-producing Escherichia coli (ESBL-E. coli) have been reported in wildlife worldwide. Whether wildlife is a transient host of ESBL-E. coli or comprises an independently maintained reservoir is unknown. We investigated this question by longitudinally monitoring ESBL-E. coli in common vampire bats and nearby livestock in Peru. Among 388 bats from five vampire bat colonies collected over three years, ESBL-E. coli were detected at a low prevalence (10% in 2015, 4% in 2017 and 2018) compared to a high prevalence (48%) from 134 livestock sampled in 2017. All ESBL-E. coli were multidrug-resistant, and whole genome sequencing of 33 randomly selected ESBL-E. coli isolates (18 recovered from bats) detected 46 genes conferring resistance to antibiotics including third-generation cephalosporins (e.g., bla_CTX-M-55, bla_CTX-M-15, bla_CTX-M-65, bla_CTX-M-3, bla_CTX-M-14), aminoglycosides, fluoroquinolones, and colistin (mcr-1). The mcr-1 gene is reported for the first time on a wild bat in Latin America. ESBL-E. coli also carried 31 plasmid replicon types and 16 virulence genes. Twenty-three E. coli sequence types (STs) were detected, including STs involved in clinical infections worldwide (e.g., ST 167, ST 117, ST 10, ST 156 and ST 648). ESBL-E. coli with identical cgMLST (ST 167) were detected in the same bat roost in 2015 and 2017, and several ESBL-E. coli from different bat roosts clustered together in the cgMLST reconstruction, suggesting long-term maintenance of ESBL-E. coli within bats. Most antibiotic resistance and virulence genes were detected in E. coli from both host populations, while ESBL-E. coli ST 744 was found in a bat and a pig from the same locality, suggesting possible cross-species exchanges of genetic material and/or bacteria between bats and livestock. This study suggests that wild mammals can maintain multidrug-resistant bacteria and share them with livestock.

High Prevalence of blaCTX-M in Fecal Commensal Escherichia coli from Healthy Children

Background

Antibiotic-resistant Escherichia coli can colonize the intestinal tract of healthy children, causing concern when antibiotic resistance is related to the presence of transferable mechanisms, such as extended-spectrum β-lactamases (ESBLs).

Materials and Methods

Fecal samples from 41 healthy children from two villages of rural Peru were cultured on ceftriaxone-disks. ESBL production was confirmed with double disk synergy. In all ESBL-produced isolates, antibiotic susceptibility to 12 antibacterial agents was established by disk diffusion, while clonal relationships were determined by repetitive extragenic palindromic-polymerase chain reaction (REP-PCR). Presence of ST131 was determined using PCR.

Results

Ceftriaxone-resistant microorganisms were recovered from 39 samples belonging to 22 out of 41 children (53.7%). Of these, 80 ceftriaxone-resistant and two ceftriaxone-intermediate E. coli from inside ceftriaxone-halos were confirmed as ESBL-producers. All isolates were multidrug-resistant. In 79/80 (98.8%) ceftriaxone-resistant isolates, the presence of bla_CTX-M was detected alone (58 isolates, or together with other β-lactamase (bla_TEM, 17 isolates; bla_OXA-1-like, 3 isolates; bla_TEM + bla_OXA-1-like, 1 isolate), while in one isolate no such ESBL was identified. The two ceftriaxone-intermediate isolates recovered from the same sample, carried a bla_TEM and bla_SHV respectively. Thirty-four different clones were identified, with 4 clones being recovered from different samples from the same child. Twelve clones were disseminated among different children, including 5 clones disseminated between both villages. Two clones, accounting for 3 isolates and both recovered from the same children, belonged to E. coli ST131.

Conclusion

This study demonstrates high prevalence of ESBL-carriers among healthy children living in a rural area of Peru, stressing the need for continuous surveillance and search for public health control measures.

Prevalence and Molecular Characterization of Fluoroquinolone-Resistant Escherichia coli in Healthy Children

Faecal E. coli can act as reservoirs for resistance genes. Here, we analyzed prevalence of drug resistance in faecal E. coli isolated from healthy children at a single kindergarten in Beijing, China, then used whole genome sequencing to characterize fluoroquinolone-non-susceptible strains. Our results revealed high resistance to ampicillin (54.0%), trimethoprim/sulphurmethoxazole (47.5%) and tetracycline (58.9%) among 576 faecal E. coli isolates, 49.2% of which exhibited multidrug resistance. A total of 113 E. coli isolates were not susceptible to ciprofloxacin, with four sequence types, namely ST1193 (25.7%), ST773 (13.3%), ST648 (8.8%) and ST131 (7.1%) found to be the most prevalent (54.9%). With regards to resistance to quinolones, we detected chromosomal mutations in gyrA, parC, and parE in 111 (98.2%), 105 (92.9%), and 67 (61.1%) isolates, respectively. bla _CTX-M (37.2%) was the major ESBL gene, whereas bla _CTX-M-14 (12.4%) and bla _CTX-M-27 (11.5%) were the most frequent subtypes. A total of 90 (79.6%) ExPEC and 65 (57.5%) UPEC isolates were classified. Overall, these findings revealed clonal spread of certain prevalent STs, namely ST1193, ST773, ST648 and ST131 E. coli isolates in healthy children within a single kindergarten in Beijing, China, affirming the seriousness of the multidrug resistance problem and potential pathogenicity of E. coli isolates in healthy children. Therefore, there is an urgent need for increased surveillance to enhance control of this problem.

Evolution of Antimicrobial Resistance Levels of ESKAPE Microorganisms in a Peruvian IV-Level Hospital

BACKGOUND

The members of the so-called ESKAPE group (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter spp.) are a frequent cause of severe infection, ranking among the most relevant causes of hospital infections. In Peru, few studies, often focused in a single ESKAPE microorganism, have been performed, but none providing an overall and comprehensive long-time analysis of the antibiotic resistance of ESKAPE microorganisms. In the present study, the evolution of antimicrobial resistance levels of ESKAPE microorganisms isolated during 2009 - 2010 (Period 1) and 2012 - 2014 (Period 2) in a IV-level hospital in Lima was analyzed.

MATERIALS AND METHODS

ESKAPE microorganisms were isolated from inpatients clinical samples. Bacterial identification, as well as antimicrobial susceptibility levels for up to 29 antimicrobial agents and presence of Extended-Spectrum β-Lactamases (only established in K. pneumoniae) were determined using automatic methods.

RESULTS

Of 9,918 clinical isolates, 1,917/3,777 (50.8%) [JAN/2009-JUN/2010 (Period 1)] and 4764/6141 (46.4%) [JAN/2012-DEC/2014 (Period 2)] belonged to the ESKAPE group (P <0.0001). ESKAPE were more frequent in the intensive care unit (ICU) (P <0.0001). E. faecium decreased from 5.1% to 4.1% (P <0.5), S. aureus from 10.5% to 7.0% (P <0.05), and P. aeruginosa from 12.9% to 11.6% (P <0.05), while, A. baumannii increased from 5.0% to 6.7% (P <0.05), mainly related to an increase in ICU isolates (8.4% vs. 17.1%; P <0.05). Overall, high levels of antimicrobial resistance were detected, but with few exceptions (e.g. vancomycin in E. faecium), antibiotic resistance levels remained stable or lower in Period 2. Contrarily, A. baumannii showed significantly increased resistance to different cephalosporins, carbapenems and amoxicillin plus sulbactam.

CONCLUSION

The introduction of a successful extensively drug-resistant A. baumannii clone in the ICU is suspected. The isolation of ESKAPE and levels of antibiotic resistance levels have reduced over time.

Recurrence of Urinary Tract Infections due to Escherichia coli and Its Association with Antimicrobial Resistance

We analyzed the association between antibiotic resistance and recurrent urinary tract infection (rUTI) by Escherichia coli. Susceptibility levels to 14 antimicrobial agents and the presence of extended-spectrum β-lactamases (ESBL) were established using MicroScan. Incidences of multidrug resistant (MDR), extensively drug resistant (XDR), and ESBL-producer isolates as well as rUTIs were estimated. The time to recurrence was established adjusted for number of antibiotic-resistant families and MDR as predictors of interest, respectively. Overall, 8,553 urinary tract infection (UTI) cases related to E. coli, including 963 rITU, were analyzed with levels of resistance >30% in all cases, except for amikacin, nitrofurantoin, and carbapenems. The incidence of rUTI was of 11.3%, being 46.5%, 24.3%, and 42.5% for MDR, XDR, and ESBLs, respectively. Bivariate analysis showed that rUTI was associated with age, gender, resistance to specific antimicrobials, MDR, and XDR. The number of antibiotic families tested as resistant, MDR, XDR, gender, and age were associated with time to recurrence when adjusted for number of antibiotic families, and MDR, gender, and age were related when adjusted for MDR. High rates of antibiotic resistance to the usual antibiotics was observed in E. coli causing UTI, with female sex, age, and antibiotic resistance being risk factors for the development of rUTI.

Erythromycin loaded by tetrahedral framework nucleic acids are more antimicrobial sensitive against Escherichia coli (E. coli)

Erythromycin is a commonly used broad-spectrum antibiotic, but resistance to this antibiotic makes its use less effective. Considerable efforts, beside finding alternatives, are needed to enhance its antimicrobial effect and stability against bacteria. Tetrahedral framework nucleic acids (tFNAs), a novel delivery vehicle with a three-dimensional nanostructure, have been studied as a carrying platform of antineoplastic drugs. In this study, the use of tFNAs in delivering erythromycin into Escherichia coli (E. coli) was investigated for the first time. The tFNAs vehicle increased the bacterial uptake of erythromycin and promoted membrane destabilization. Moreover, it increased the permeability of the bacterial cell wall, and reduced drug resistance by improving the movement of the drug across the membrane. The tFNAs-based delivery system enhanced the effects of erythromycin against E. coli. It may therefore provide an effective delivery vehicle for erythromycin in targeting antibiotic-resistant bacteria with thick cell wall.

Antimicrobial Resistance Levels among Gram-negative Bacteria from Peruvian Boobies (Sula variegata) in Northern Peru

The presence of antimicrobial-resistant bacteria in feces of 42 Peruvian Boobies (Sula variegata) from a Northern Peru island was evaluated using MicroScan and disk diffusion. Fourteen microorganisms were recovered, including three Pseudomonas spp. resistant to one antibiotic each, and four multiresistant Escherichia coli. Antimicrobial-resistant bacteria are reported in S. variegata.

A Multidrug-Resistant Salmonella Infantis Clone is Spreading and Recombining in the United States

Recently, there have been reports worldwide of a multidrug-resistant, emergent Salmonella Infantis (ESI) clone with a large megaplasmid (pESI), often containing the extended-spectrum beta-lactamase gene blaCTX-M-65. This clone also has a gyrA mutation conferring fluoroquinolone resistance, further limiting treatment options. In the United States, this clone has also been found in poultry sources, indicating a likely source of human illnesses. We conducted short-read sequencing of Salmonella enterica isolated from retail meats as part of routine surveillance by the National Antimicrobial Resistance Monitoring System (NARMS). We analyzed the resulting data temporally and geographically to determine when and where the ESI clone has spread in the United States. We found the ESI clone was first found in retail meats in Tennessee in 2014, but by 2019 was throughout the United States and comprised 29% of all Salmonella isolated from retail chickens, and 7% from retail turkey. Of these isolates, 85.0% were within 20 single nucleotide polymorphisms (SNPs) of those causing human illnesses. Long-read sequencing data indicated substantial recombination in the pESI plasmid resulting in the presence of 0-10 resistance genes, despite all their chromosomes being within 31 SNPs of one another. This work demonstrates the rapid spread of this clone of Salmonella Infantis in poultry in the United States, with the potential for increased burden of human illness attributed to this multidrug-resistant pathogen.

Challenge in the Discovery of New Drugs: Antimicrobial Peptides against WHO-List of Critical and High-Priority Bacteria

Bacterial resistance has intensified in recent years due to the uncontrolled use of conventional drugs, and new bacterial strains with multiple resistance have been reported. This problem may be solved by using antimicrobial peptides (AMPs), which fulfill their bactericidal activity without developing much bacterial resistance. The rapid interaction between AMPs and the bacterial cell membrane means that the bacteria cannot easily develop resistance mechanisms. In addition, various drugs for clinical use have lost their effect as a conventional treatment; however, the synergistic effect of AMPs with these drugs would help to reactivate and enhance antimicrobial activity. Their efficiency against multi-resistant and extensively resistant bacteria has positioned them as promising molecules to replace or improve conventional drugs. In this review, we examined the importance of antimicrobial peptides and their successful activity against critical and high-priority bacteria published in the WHO list.

Dissemination of a multidrug resistant CTX-M-65 producer Salmonella enterica serovar Infantis clone between marketed chicken meat and children

The objective of the present study was to characterize Salmonella enterica serovar Infantis isolated from chicken meat determining their clonal relationships with S. Infantis isolated from children with diarrhea. Fifteen meat-recovered S. Infantis were analyzed. Susceptibility levels to 14 antibacterial agents, the presence of ESBL and that of inducible plasmid-mediated AmpC (i-pAmpC) were determined by phenotypical methods. The presence of ESBL and pAmpC was confirmed by PCR, and detected ESBL-encoding genes were sequenced and their transferability tested by conjugation. The presence of gyrA mutations as well as Class 1 integrons was determined by PCR. Clonal relationships were established by REP-PCR and RAPD. In addition, 25 clinical isolates of S. Infantis were included in clonality studies. All meat-recovered S. Infantis were MDR, showing resistance to ampicillin, nitrofurans and quinolones, while none was resistant to azithromycin, ceftazidime or imipenem. ESBL (bla_CTX-M-65) and i-pAmpC (bla_DHA) were detected in 2 and 5 isolates respectively (in one case concomitantly), with bla_CTX-M-65 being transferable through conjugation. In addition, 1 isolate presented a bla_SHV gene. All isolates presented D₈₇Y at GyrA, nalidixic acid active efflux pump and a Class 1 integron of ~1000 bp (aadA1). Clonal analysis showed that all isolates were related. Further they were identical to MDR bla_CTX-M-65-producing S. Infantis isolates causing children diarrhea in Lima. The dissemination of MDR bla_CTX-M-65-producing S. Infantis between marketed meat and children highlights a public health problem which needs be controlled at livestock level.

Structural characterization and pharmacological assessment in vitro/in vivo of a new copper(II)-based derivative of enrofloxacin

Enrofloxacin (EFX) was selected as the medicinal ligand to afford a new copper(ii)-based complex, EFX-Cu, which was structurally characterized by spectroscopic analyses including X-ray single crystal diffraction. It was also stable and could retain the coordination state in aqueous solution. The in vitro antibacterial activity of EFX-Cu against a panel of pathogenic bacteria was about the same as that of EFX, except that it was twice as active against E. coli. The in vivo test on mice gave a LD50 value of 8148 mg kg-1 for EFX-Cu, which was much lower than those for EFX (LD50, 5312 mg kg-1) and its clinically used sodium salt, EFX-Na (LD50, 1421 mg kg-1). In addition, no obvious lesions in the organs of the dead mice were found by histopathological examination. Pharmacokinetic studies on rats suggested similar pharmacokinetics between EFX-Cu and EFX. On the other hand, EFX-Cu showed higher acute toxicity than EFX-Na in zebrafish, which was inconsistent with that in mice. The ROS-related inflammation and anti-inflammatory assay of EFX-Cu, respectively, in normal cells and zebrafish could be ascribed to its ROS-related redox property. Unfortunately, the final in vivo therapeutic assay in the E. coli-infected mouse model indicated that the therapeutic effect of EFX-Cu, mainly in terms of mortality in mice, was found to be lower than that of EFX-Na at the same dosage (800 mg kg-1, continuous gavage), although the contradictory factors between toxicity and antibacterial activity could not be excluded in this trial.

Novel 5-Nitrofuran-Activating Reductase in Escherichia coli

The global spread of multidrug-resistant enterobacteria warrants new strategies to combat these pathogens. One possible approach is the reconsideration of "old" antimicrobials, which remain effective after decades of use. Synthetic 5-nitrofurans such as furazolidone, nitrofurantoin, and nitrofurazone are such a class of antimicrobial drugs. Recent epidemiological data showed a very low prevalence of resistance to this antimicrobial class among clinical Escherichia coli isolates in various parts of the world, forecasting the increasing importance of its uses to battle antibiotic-resistant enterobacteria. However, although they have had a long history of clinical use, a detailed understanding of the 5-nitrofurans' mechanisms of action remains limited. Nitrofurans are known as prodrugs that are activated in E. coli by reduction catalyzed by two redundant nitroreductases, NfsA and NfsB. Furazolidone, nevertheless, retains relatively significant antibacterial activity in the nitroreductase-deficient ΔnfsA ΔnfsB E. coli strain, indicating the presence of additional activating enzymes and/or antibacterial activity of the unreduced form. Using genome sequencing, genetic, biochemical, and bioinformatic approaches, we discovered a novel 5-nitrofuran-activating enzyme, AhpF, in E. coli The discovery of a new nitrofuran-reducing enzyme opens new avenues for overcoming 5-nitrofuran resistance, such as designing nitrofuran analogues with higher affinity for AhpF or screening for adjuvants that enhance AhpF expression.

Recent advances in the synthetic and medicinal perspective of quinolones: A review

In the modern scenario, the quinolone scaffold has emerged as a very potent motif considering its clinical significance. Quinolones possess wide range of pharmacological activities such as anticancer, antibacterial, antifungal, antiprotozoal, antiviral, anti-inflammatory, carbonic anhydrase inhibitory and diuretic activity etc. The versatile synthetic approaches have been successfully applied and several of the resulted synthesized compounds exhibit fascinating biological activities in numerous fields. This has prompted to discover quinolone-based analogues among the researchers due to its great diversity in biological activities. In the past few years, various new, efficient and convenient synthetic approaches (including green chemistry and microwave-assisted synthesis) have been designed and developed to synthesize diverse quinolone-based scaffolds which represent a growing area of interest in academic and industry as well as to explore their biological activities. In this review, an attempt has been made by the authors to summarize (1) One of the most comprehensive listings of quinolone-based drugs or agents in the market or under various stages of clinical development; (2) Recent advances in the synthetic strategies for quinolone derivatives as well as their biological implications including insight of mechanistic studies. (3) Further, the biological data is correlated with structure-activity relationship studies to provide an insight into the rational design of more active agents.

Transferable Mechanisms of Quinolone Resistance from 1998 Onward

While the description of resistance to quinolones is almost as old as these antimicrobial agents themselves, transferable mechanisms of quinolone resistance (TMQR) remained absent from the scenario for more than 36 years, appearing first as sporadic events and afterward as epidemics. In 1998, the first TMQR was soundly described, that is, QnrA. The presence of QnrA was almost anecdotal for years, but in the middle of the first decade of the 21st century, there was an explosion of TMQR descriptions, which definitively changed the epidemiology of quinolone resistance. Currently, 3 different clinically relevant mechanisms of quinolone resistance are encoded within mobile elements: (i) target protection, which is mediated by 7 different families of Qnr (QnrA, QnrB, QnrC, QnrD, QnrE, QnrS, and QnrVC), which overall account for more than 100 recognized alleles; (ii) antibiotic efflux, which is mediated by 2 main transferable efflux pumps (QepA and OqxAB), which together account for more than 30 alleles, and a series of other efflux pumps (e.g., QacBIII), which at present have been sporadically described; and (iii) antibiotic modification, which is mediated by the enzymes AAC(6')Ib-cr, from which different alleles have been claimed, as well as CrpP, a newly described phosphorylase.

Azithromycin resistance levels and mechanisms in Escherichia coli

Despite azithromycin being used in some countries to treat infections caused by Gram-negative pathogens, no resistance breakpoint for Escherichia coli exists. The aim of this study was to analyse the levels and mechanisms of azithromycin resistance in E. coli. The presence of chromosomal (rplD, rplV and 23S rRNA) mutations, 10 macrolide resistance genes (MRGs) and efflux pump overexpression was determined in 343 E. coli isolates. Overall, 89 (25.9%) isolates had MICs ≥ 32 mg/L to azithromycin, decreasing to 42 (12.2%) when assayed in the presence of Phe-Arg-β-Napthylamide, with 35 of these 42 possessing at least one MRG. Efflux pumps played a role in azithromycin resistance affecting the Minimal Inhibitory Concentration (MIC) levels of 91.2% isolates whereas chromosomal alterations seem to have a minimal role. At least one MRG was found in 22.7% of the isolates with mph(A) being the most commonly found gene. The mph(A) gene plays the main role in the development of azithromycin resistance and 93% of the mph(A)-carrying isolates showed a MIC of 32 mg/L. In the absence of a specific resistance breakpoint our results suggest a MIC of 32 mg/L to be considered in order to detect isolates carrying mechanisms able to confer azithromycin resistance.

Draft genome sequence of a multidrug-resistant CTX-M-65-producing Escherichia coli ST156 colonizing a giant anteater (Myrmecophaga tridactyla) in a Zoo

OBJECTIVES

This study aimed to report the draft genome sequence of a multidrug-resistant (MDR) Escherichia coli colonizing a giant anteater (Myrmecophaga tridactyla) in a Brazilian Zoo.

METHODS

The genome was sequenced using the Illumina MiSeq Platform and de novo genome assembly was performed using SPAdes v. 3.9. The draft genome sequence was annotated using NCBI Prokaryotic Genome Annotation Pipeline. Antibiotic resistance genes, virulence genes, sequence type, serotype and plasmid incompatibility groups were identified using tools from the Center for Genomic Epidemiology.

RESULTS

The genome presented 4970 coding sequences and a GC content of 50.2%. Several antimicrobial resistance genes associated with resistance to β-lactams (bla_TEM-1A and bla_CTX-M-65), aminoglycosides [aph(6)-ld, aph(3″)-lb, aph(4)-la, aac(3)-lVa, aadA1 and aadA2], tetracyclines (tetB), sulphonamides (sul2 and sul3), trimethoprim (dfrA8 and dfrA12) and phenicols (floR and cmlA1) were identified. Moreover, mutations in quinolone resistance-determining regions (QRDR) were found. This E. coli isolate also presented virulence genes and belonged to serotype ONT:H25 and ST156 (CC156).

CONCLUSION

This is the first report of a draft genome sequence of a CTX-M-65-producing E. coli ST156 obtained from a zoo animal, which can be used by genomic surveillance platforms, in order to track transmission dynamics of extended-spectrum β-lactamase (ESBL)-producing E. coli at the human-animal interface.

Guanidine functionalized anthranilamides as effective antibacterials with biofilm disruption activity

We describe a library of amphiphilic anthranilamide compounds as antimicrobial peptide (AMP) mimics. These contain a hydrophobic naphthoyl side chain and different hydrophilic cationic groups such as amino, quaternary ammonium and guanidino groups. These are prepared via the ring-opening of different isatoic anhydrides. The antibacterial activity against S. aureus and E. coli of compounds containing guanidino cationic groups was greater than that for amino and quaternary ammonium cationic groups. The fluoro-substituted guanidinium compound 9b showed a minimum inhibitory concentration (MIC) of 2.0 μM against S. aureus, and reduced established biofilms of S. aureus by 92% at 64 μM concentration. The bromo-substituted guanidinium compound 9d exhibited good MIC against S. aureus (3.9 μM) and E. coli (15.6 μM) and disrupted established biofilms of S. aureus by 83% at 62.4 μM concentration. Cytoplasmic membrane permeability studies suggested that depolarization and disruption of the bacterial cell membrane could be a possible mechanism for antibacterial activity and the in vitro toxicity studies against MRC-5 human lung fibroblast cells showed that the potent compounds are non-toxic against mammalian cells.

Interplay between MexAB-OprM and MexEF-OprN in clinical isolates of Pseudomonas aeruginosa

MexAB-OprM and MexEF-OprN are Pseudomonas aeruginosa efflux pumps involved in the development of antibiotic resistance. Several studies developed with laboratory strains or using a few clinical isolates have reported that the regulation system of MexEF-OprN is involved in the final levels of MexAB-OprM expression. Therefore, this study was aimed to determine the interplay between MexAB-OprM and MexEF-OprN in 90 out of 190 P. aeruginosa clinical isolates with an efflux pump overexpression phenotype. Regarding oprD, 33% (30/90) of isolates displayed relevant modifications (RM) defined as frameshift or premature stop, both related to carbapenem resistance. On the other hand, 33% of the isolates displayed RM in nalC, nalD or mexR, which were significantly associated with multidrug resistance (MDR), non-susceptibility to carbapenems, OprD alterations and strong biofilm production. Meanwhile, the RM in MexS were associated with presence of pigment (p = 0.004). Otherwise, when all the regulators were analysed together, the association between RM in MexAB-OprM regulators and MDR was only significant (p = 0.039) when mexS was the wild type. These data show the modulatory effect of MexEF-OprN on MexAB-OprM in a clinical population of P. aeruginosa. Further studies may contribute to design of novel molecules acting on this interplay to fight against antimicrobial resistance.

Antibacterial naphthoquinone derivatives targeting resistant strain Gram-negative bacteria in biofilms

The aims of this study were the planning, synthesis and in vitro evaluation of 2-hydroxy-3-phenylsulfanylmethyl-[1,4]-naphthoquinones against Gram-negative and Gram-positive strains, searching for potential lead compounds against bacterial biofilm formation. A series of 12 new analogs of 2-hydroxy-3-phenylsulfanylmethyl-[1,4]-naphthoquinones were synthesized by adding a thiol and different substituents to a ο-quinone methide using microwave irradiation. The compounds were tested against Gram-positive (Enterococcus faecalis ATCC 29212, Staphylococcus aureus ATCC 25923, S. simulans ATCC 27851, S. epidermidis ATCC 12228 and a hospital Methicillin-resistant S. aureus (MRSA) strain), as well as Gram-negative (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, P. aeruginosa ATCC 15442, Proteus mirabilis ATCC 15290, Serratia marcescens ATCC 14756, Klebsiella pneumoniae ATCC 4352 and Enterobacter cloacae ATCC 23355) strains, using the disk diffusion method. Ten compounds showed activity mainly against Gram-negative strains with a minimal inhibitory concentration (MIC = 4-64 μg/mL) within the Clinical and Laboratory Standards Institute (CLSI) levels. The biofilm inhibition data showed compounds, 9e, 9f, 9j and 9k, are anti-biofilm molecules when used in sub-MIC concentrations against P. aeruginosa ATCC 15442 strain. Compound (9j) inhibited biofilm formation up to 63.4% with a better profile than ciprofloxacin, which is not able to prevent biofilm formation effectively. The reduction of P. aeruginosa ATCC 15442 mature biofilms was also observed for 9e and 9k. The structure modification applied in the series resulted in 12 new naphthoquinones with antimicrobial activity against Gram-negative bacteria strains (E. coli ATCC 25922, P. aeruginosa ATCC 27853 and ATCC 15442). Four compounds decreased P. aeruginosa biofilm formation effectively.

Cefiderocol: a novel siderophore cephalosporin

INTRODUCTION

The emergence of multidrug-resistant bacterial pathogens has led to a global public health emergency and novel therapeutic options and drug-delivery systems are urgently needed. Cefiderocol is a siderophore cephalosporin antibiotic that has recently been developed to combat a variety of bacterial pathogens, including β-lactam- and carbapenem-resistant organisms.

AREAS COVERED

This paper provides an overview of the mutational and plasmid-mediated mechanisms of β-lactam and carbapenem resistance, the biochemical pathways of siderophores in bacterial iron metabolism, and how cefiderocol may be able to provide better targeted antimicrobial therapy that escape these drug-resistant mechanisms. We also explore the pharmacokinetics of this new compound as well as results from preclinical and clinical studies.

EXPERT OPINION

There is an urgent need for novel antimicrobial agents to address the emergence of multidrug-resistant pathogens, which are an increasing cause of morbidity and mortality worldwide. Our understanding of multidrug-resistance and bacterial biochemical pathways continues to expand, and the development of cefiderocol specifically targeting siderophore-mediated iron transport shows potential in escaping mechanisms of drug resistance. Cefiderocol, which demonstrates a favorable side effect profile, has the potential to become first-line therapy for our most aggressive and lethal multidrug-resistant Gram-negative pathogens.