Emergence of pan-resistance in KPC-2 carbapenemase-producing Klebsiella pneumoniae in Crete, Greece: a close call

Prevalence of colistin-resistant Enterobacteriaceae isolated from clinical samples in Africa: a systematic review and meta-analysis

BACKGROUND

Antimicrobial resistance among Enterobacteriaceae poses a significant global threat, particularly in developing countries. Colistin, a critical last-resort treatment for infections caused by carbapenem-resistant and multidrug-resistant strains, is increasingly facing resistance due to inappropriate use of colistin and the spread of plasmid-mediated resistance genes. Despite the significance of this issue, comprehensive and updated data on colistin resistance in Africa is lacking. Thus, the current study was aimed to determine the pooled prevalence of colistin-resistant Enterobacteriaceae in Africa.

METHODS

A systematic search was conducted across PubMed, Scopus, ScienceDirect, and Google Scholar to identify relevant studies. Forty-one studies reporting on the prevalence of colistin resistance in Enterobacteriaceae isolates from clinical specimens in Africa were included in the analysis. Stata 17 software was used to calculate the pooled prevalence of colistin resistance, employing a random-effects model to determine the event rate of resistance. Heterogeneity across studies was assessed using the I2 statistic, and publication bias was evaluated using Egger's test. Subgroup analyses were performed to address any identified heterogeneity.

RESULTS

This systematic review analyzed the colistin resistance profile of 9,636 Enterobacteriaceae isolates. The overall pooled prevalence of colistin resistance was 26.74% (95% CI: 16.68-36.80). Subgroup analysis by country revealed significant variability in resistance rates, ranging from 0.5% in Djibouti to 50.95% in South Africa. Species-specific prevalence of colistin resistance was as follows: K. pneumoniae 28.8% (95% CI: 16.64%-41.05%), E. coli 24.5% (95% CI: 11.68%-37.3%), Proteus spp. 50.0% (95% CI: 6.0%-106.03%), and Enterobacter spp. 1.22% (95% CI: -0.5%-3.03%). Analysis based on AST methods revealed significant differences in colistin resistance rates (p = 0.001). The resistance rates varied between 12.60% for the disk diffusion method and 28.0% for the broth microdilution method. Additionally, a subgroup analysis of clinical specimens showed significant variation (p < 0.001) in colistin resistance. Stool specimen isolates had the highest resistance rate at 42.0%, while blood specimen isolates had a much lower resistance rate of 3.58%.

CONCLUSIONS

Colistin resistance in Enterobacteriaceae is notably high in Africa, with significant variation across countries. This underscores the urgent need for effective antimicrobial stewardship, improved surveillance, and the development of new antibiotics.

Exploring New Delhi Metallo Beta Lactamases in Klebsiella pneumoniae and Escherichia coli: genotypic vs. phenotypic insights

BACKGROUND

Carbapenemase-producing Enterobacterales pose a serious clinical threat, particularly in high-burden settings of carbapenem-resistant Escherichia coli and Klebsiella pneumoniae (CREK), where rapid detection tools are essential to aid patient management. In this study, we focused on blaNDM, the most frequently reported carbapenemase in the region, and evaluated a combined phenotypic (lateral flow) and genotypic (PCR and WGS) approach for its detection. This research underscores the utility of lateral flow assays as a practical alternative to resource-intensive genotypic methods, offering a scalable solution for settings with limited laboratory capacity.

METHOD

One hundred seventy-seven extensively drug-resistant strains were characterized using MALDI-TOF. Isolates were analyzed to detect Carbapenem-resistant Escherichia coli and Klebsiella pneumoniae (CREK) using disk diffusion, MIC test, and PCR targeting blaNDM. Antibiotic susceptibility patterns were analyzed and visualized using single-linkage hierarchical clustering, with results displayed on a permuted heat map. Immunochromatographic assay, RESIST-5 O.K.N.V.I (Coris Bioconcept®) was used for CREK isolates [(n = 17), positive and negative)] and Oxford Nanopore Sequencing was conducted on subsets [(n = 5) blaNDM-positive co-producers of blaNDM and blaOXA, and (n = 2) blaNDM-negative blaOXA producers) to evaluate the reliability of phenotypic and genotypic tests.

RESULT

Most of the XDR strains (90%) were CREK, with K. pneumoniae (71.2%) more prevalent than E. coli (28.7%) (p < 0.05). All CREK strains exhibited complete resistance (100%) to multiple antibiotics with 66% showing sensitivity to levofloxacin. Furthermore, K. pneumoniae (57.8%) had higher blaNDM gene prevalence than E. coli (36.9%). Among blaNDM-positive CREK, lateral flow assay revealed approximately half of each bacteria type co-produced blaOXA (E.coli, 52.9%), and (K. pneumoniae, 47%). For blaNDM-negative strains, blaOXA was more prevalent in K. pneumoniae (82.35%) than E. coli (41%) (p < 0.05). Comparing phenotypic to genotypic assays, E. coli showed 100% (CI 80.49 - 100%) sensitivity and specificity with a high Kappa agreement coefficient (0.91) (CI 95% 0.661-1, p < 0.01), whereas K. pneumoniae assays had lower sensitivity and specificity (40%) (CI 5.27 - 85.34%), with a lower Kappa agreement coefficient (0.20) (CI 95% 0.104-0.298, p < 0.01).

CONCLUSION

This study demonstrates the value of the RESIST-5 O.K.N.V.I. lateral flow assay as a rapid and reliable diagnostic tool for detecting blaNDM in Escherichia coli, with strong agreement to PCR and WGS. While performance for Klebsiella pneumoniae was lower, the assay offers a practical alternative in resource-limited settings, aiding antimicrobial stewardship and improving diagnostic capacities in high-burden regions.

Efficacy of colistin-based combinations against pandrug-resistant whole-genome-sequenced Klebsiella pneumoniae isolated from hospitalized patients in Egypt: an in vitro/vivo comparative study

BACKGROUND

Colistin resistance significantly constrains available treatment options and results in the emergence of pandrug-resistant (PDR) strains. Treating PDR infections is a major public health issue. A promising solution lies in using colistin-based combinations. Despite the availability of in vitro data evaluating these combinations, the in vivo studies remain limited.

RESULTS

Thirty colistin-resistant Klebsiella pneumoniae (ColRKp) isolates were collected from hospitalized patients. Colistin resistance was detected using broth microdilution, and antimicrobial susceptibility was tested using the Kirby-Bauer method against 18 antibiotics. Extremely high resistance levels were detected, with 17% of the isolates being PDR. Virulence profiling, assessed using Anthony capsule staining, the string test, and the crystal violet assay, indicated the predominance of non-biofilm formers and non-hypermucoid strains. The isolates were screened for mcr genes using polymerase chain reaction. Whole-genome sequencing (WGS) and bioinformatics analysis were performed to characterize the genomes of PDR isolates. No plasmid-borne mcr genes were detected, and WGS analysis revealed that PDR isolates belonged to the high-risk clones: ST14 (n = 1), ST147 (n = 2), and ST383 (n = 2). They carried genes encoding extended-spectrum β-lactamases and carbapenemases, blaCTX-M-15 and blaNDM-5, on conjugative IncHI1B/IncFIB plasmids, illustrating the convergence of virulence and resistance genes. The most common mechanism of colistin resistance involved alterations in mgrB. Furthermore, deleterious amino acid substitutions were also detected within PhoQ, PmrC, CrrB, ArnB, and ArnT. Seven colistin-containing combinations were compared using the checkerboard experiment. Synergy was observed when combining colistin with tigecycline, doxycycline, levofloxacin, ciprofloxacin, sulfamethoxazole/trimethoprim, imipenem, or meropenem. The efficacy of colistin combined with either doxycycline or levofloxacin was assessed in vitro using a resistance modulation assay, and in vivo, using a murine infection model. In vitro, doxycycline and levofloxacin reversed colistin resistance in 80% and 73.3% of the population, respectively. In vivo, the colistin + doxycycline combination demonstrated superiority over colistin + levofloxacin, rescuing 80% of infected animals, and reducing bacterial bioburden in the liver and kidneys while preserving nearly intact lung histology.

CONCLUSIONS

This study represents the first comparative in vitro and in vivo investigation of the efficacy of colistin + doxycycline and colistin + levofloxacin combinations in clinical PDR ColRKp isolates characterized at a genomic level.

Global prevalence of mutation in the mgrB gene among clinical isolates of colistin-resistant Klebsiella pneumoniae: a systematic review and meta-analysis

Background

Colistin is used as a last resort for managing infections caused by multidrug-resistant bacteria. However, the high emergence of colistin-resistant strains has restricted the clinical use of this antibiotic in the clinical setting. In the present study, we evaluated the global prevalence of the mutation in the mgrB gene, one of the most important mechanisms of colistin resistance in Klebsiella pneumoniae.

Methods

Several databases, including Scopus, Medline (via PubMed), and Web of Science, were searched (until August 2023) to identify those studies that address the mgrB mutation in clinical isolates of K. pneumoniae. Using Stata software, the pooled prevalence of mgrB mutation and subgroup analyses for the year of publication, country, continent, mgrB mutation types, and detection methods of mgrB mutation were analyzed.

Results

Out of the 115 studies included in the analysis, the prevalence of mgrB mutations in colistin-resistant K. pneumoniae isolates was estimated at 65% of isolates, and mgrB variations with insertional inactivation had the highest prevalence among the five investigated mutations with 69%. The year subgroup analysis indicated an increase in mutated mgrB from 46% in 2014 to 61% in 2022. Europe had the highest prevalence of mutated mgrB at 73%, while Africa had the lowest at 54%.

Conclusion

Mutations in the mgrB gene are reported as one of the most common mechanisms of colistin resistance in K. pneumoniae, and the results of the present study showed that 65% of the reported colistin-resistant K. pneumoniae had a mutation in this gene.

Comparative Genomics of Pseudomonas aeruginosa Strains Isolated from Different Ecological Niches

The Pseudomonas aeruginosa genome can change to adapt to different ecological niches. We compared four genomes from a Mexican hospital and 59 genomes from GenBank from different niches, such as urine, sputum, and environmental. The ST analysis showed that high-risk STs (ST235, ST773, and ST27) were present in the genomes of the three niches from GenBank, and the STs of Mexican genomes (ST167, ST2731, and ST549) differed from the GenBank genomes. Phylogenetic analysis showed that the genomes were clustering according to their ST and not their niche. When analyzing the genomic content, we observed that environmental genomes had genes involved in adapting to the environment not found in the clinics and that their mechanisms of resistance were mutations in antibiotic resistance-related genes. In contrast, clinical genomes from GenBank had resistance genes, in mobile/mobilizable genetic elements in the chromosome, except for the Mexican genomes that carried them mostly in plasmids. This was related to the presence of CRISPR-Cas and anti-CRISPR; however, Mexican strains only had plasmids and CRISPR-Cas. bla_OXA-488 (a variant of bla_OXA50) with higher activity against carbapenems was more prevalent in sputum genomes. The virulome analysis showed that exoS was most prevalent in the genomes of urinary samples and exoU and pldA in sputum samples. This study provides evidence regarding the genetic variability among P. aeruginosa isolated from different niches.

Molecular characterization of colistin resistance genes in a high-risk ST101/KPC-2 clone of Klebsiella pneumoniae in a University Hospital of Split, Croatia

Klebsiella pneumoniae carbapenemase-producing K. pneumoniae (KPC-KP) has become a major concern worldwide due to multidrug resistance and the ability to spread locally and globally. Infections caused by KPC-KP are great challenge in the healthcare systems because these are associated with longer hospitalization and high mortality. The emergence of colistin resistance has significantly reduced already limited treatment options. This study describes the molecular background of colistin-resistant KPC-KP isolates in the largest hospital in southern Croatia. Thirty-four non-duplicate colistin-resistant KPC-KP isolates were collected during routine work from April 2019 to January 2020 and from February to May 2021. Antimicrobial susceptibility was determined using disk diffusion, broth microdilution, and the gradient strip method. Carbapenemase was detected with an immunochromatographic test. Identification of bla_KPC and mcr genes or mutations in pmrA, pmrB, mgrB, phoP, and phoQ genes were performed by polymerase chain reaction (PCR) and positive products were sequenced. Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were used for epidemiological analysis. All isolates were multidrug-resistant, with colistin minimum inhibitory concentrations (MICs) from 4 to >16 mg/L, and all harbored bla_KPC-2 and had a single point mutation in the mgrB gene resulting in a premature stop codon, with the exception of one isolate with four point mutations corresponding to stop codons. All isolates were negative for mcr genes. PFGE analysis identified a single genetic cluster, and MLST revealed that all isolates belonged to sequence type 101 (ST101). These results show emergence of the high-risk ST101/KPC-2 clone of K. pneumoniae in Croatia as well as appearance of colistin resistance due to mutations in the mgrB gene. Molecular analysis of epidemiology and possible resistance mechanisms are important to develop further strategies to combat such threats.

Flagellotropic Bacteriophages: Opportunities and Challenges for Antimicrobial Applications

Bacteriophages (phages) are the most abundant biological entities in the biosphere. As viruses that solely infect bacteria, phages have myriad healthcare and agricultural applications including phage therapy and antibacterial treatments in the foodservice industry. Phage therapy has been explored since the turn of the twentieth century but was no longer prioritized following the invention of antibiotics. As we approach a post-antibiotic society, phage therapy research has experienced a significant resurgence for the use of phages against antibiotic-resistant bacteria, a growing concern in modern medicine. Phages are extraordinarily diverse, as are their host receptor targets. Flagellotropic (flagellum-dependent) phages begin their infection cycle by attaching to the flagellum of their motile host, although the later stages of the infection process of most of these phages remain elusive. Flagella are helical appendages required for swimming and swarming motility and are also of great importance for virulence in many pathogenic bacteria of clinical relevance. Not only is bacterial motility itself frequently important for virulence, as it allows pathogenic bacteria to move toward their host and find nutrients more effectively, but flagella can also serve additional functions including mediating bacterial adhesion to surfaces. Flagella are also a potent antigen recognized by the human immune system. Phages utilizing the flagellum for infections are of particular interest due to the unique evolutionary tradeoff they force upon their hosts: by downregulating or abolishing motility to escape infection by a flagellotropic phage, a pathogenic bacterium would also likely attenuate its virulence. This factor may lead to flagellotropic phages becoming especially potent antibacterial agents. This review outlines past, present, and future research of flagellotropic phages, including their molecular mechanisms of infection and potential future applications.

A New Method Based on LAMP-CRISPR–Cas12a-Lateral Flow Immunochromatographic Strip for Detection

Introduction

Methods

Results

Discussion

Context-aware genomic surveillance reveals hidden transmission of a carbapenemase-producing Klebsiella pneumoniae

Genomic surveillance can inform effective public health responses to pathogen outbreaks. However, integration of non-local data is rarely done. We investigate two large hospital outbreaks of a carbapenemase-carrying Klebsiella pneumoniae strain in Germany and show the value of contextual data. By screening about 10 000 genomes, over 400 000 metagenomes and two culture collections using in silico and in vitro methods, we identify a total of 415 closely related genomes reported in 28 studies. We identify the relationship between the two outbreaks through time-dated phylogeny, including their respective origin. One of the outbreaks presents extensive hidden transmission, with descendant isolates only identified in other studies. We then leverage the genome collection from this meta-analysis to identify genes under positive selection. We thereby identify an inner membrane transporter (ynjC) with a putative role in colistin resistance. Contextual data from other sources can thus enhance local genomic surveillance at multiple levels and should be integrated by default when available.

Pandrug-resistant Gram-negative bacteria: a systematic review of current epidemiology, prognosis and treatment options

BACKGROUND

The literature on the epidemiology, mortality and treatment of pandrug-resistant (PDR) Gram-negative bacteria (GNB) is scarce, scattered and controversial.

OBJECTIVES

To consolidate the relevant literature and identify treatment options for PDR GNB infections.

METHODS

A systematic search in MEDLINE, Scopus and clinical trial registries was conducted. Studies reporting PDR clinical isolates were eligible for review if susceptibility testing for all major antimicrobials had been performed. Characteristics and findings of retrieved studies were qualitatively synthesized.

RESULTS

Of 81 studies reviewed, 47 (58%) were published in the last 5 years. The reports reflected a worldwide dissemination of PDR GNB in 25 countries in 5 continents. Of 526 PDR isolates reported, Pseudomonas aeruginosa (n=175), Acinetobacter baumannii (n=172) and Klebsiella pneumoniae (n=125) were most common. PDR GNB were typically isolated in ICUs, but several studies demonstrated wider outbreak potential, including dissemination to long-term care facilities and international spread. All-cause mortality was high (range 20%-71%), but appeared to be substantially reduced in studies reporting treatment regimens active in vitro. No controlled trial has been performed to date, but several case reports and series noted successful use of various regimens, predominantly synergistic combinations, and in selected patients increased exposure regimens and newer antibiotics.

CONCLUSIONS

PDR GNB are increasingly being reported worldwide and are associated with high mortality. Several treatment regimens have been successfully used, of which synergistic combinations appear to be most promising and often the only available option. More pharmacokinetic/pharmacodynamic and outcome studies are needed to guide the use of synergistic combinations.

Emerging Antimicrobial-Resistant High-Risk Klebsiella pneumoniae Clones ST307 and ST147

There is an enormous global public health burden due to antimicrobial-resistant (AMR) Klebsiella pneumoniae high-risk clones. K. pneumoniae ST307 and ST147 are recent additions to the family of successful clones in the species. Both clones likely emerged in Europe during the early to mid-1990s and, in a relatively short time, became prominent global pathogens, spreading to all continents (with the exception of Antarctica). ST307 and ST147 consist of multiple clades/clusters and are associated with various carbapenemases (i.e., KPCs, NDMs, OXA-48-like, and VIMs). ST307 is endemic in Italy, Colombia, the United States (Texas), and South Africa, while ST147 is endemic in India, Italy, Greece, and certain North African countries. Both clones have been introduced into regions of nonendemicity, leading to worldwide nosocomial outbreaks. Genomic studies showed ST307 and ST147 contain identical gyrA and parC mutations and likely obtained plasmids with bla _CTX-M-15 during the early to mid-2000s, which aided in their global distribution. ST307 and ST147 then acquired plasmids with various carbapenemases during the late 2000s, establishing themselves as important AMR pathogens in certain regions. Both clones are likely underreported due to restricted detection methodologies. ST307 and ST147 have the ability to become major threats to public health due to their worldwide distribution, ability to cause serious infections, and association with AMR, including panresistance. The medical community at large, especially those concerned with antimicrobial resistance, should be aware of the looming threat posed by emerging AMR high-risk clones such as K. pneumoniae ST307 and ST147.

Prevalence of OXA-type Class D β-lactamases Among Clinical Isolates of Klebsiella Pneumoniae in Multiple Centers of Tehran, Iran

BACKGROUND

Drug- and multidrug-resistant Klebsiella pneumoniae isolates have been found worldwide. Treatment failures against carbapenems and extended-spectrum cephalosporins, the currently recommended drugs, contribute to consider K. pneumoniae infections as untreatable infections. The emergence and spread of oxacillinases (OXAs) with carbapenem-hydrolyzing properties are a major concern and seriously become a public health problem worldwide. The present study was aimed to explore the bla_OXA genes among clinical isolates of K. pneumoniae in some clinical settings in Tehran, Iran.

METHODS

A total of 90 K. pneumoniae isolates were collected from different clinical samples at hospitals in Tehran during the year 2016 and 2018. Antimicrobial susceptibility testing was performed on bacterial isolates using the Kirby-Bauer disc diffusion method on Mueller Hinton agar plates. PCR experiments were carried out to detect the presence of the bla_OXA genes, including bla_{OXA- 1}, bla_OXA-2, bla_OXA-4, bla_OXA10, and bla_OXA-48-like, using specific primers.

RESULTS

The antibiotics susceptibility results showed that 41% of the K. pneumoniae isolates were resistant to imipenem and meropenem. Resistance rates for cephalosporin agents, including cefpodoxime, ceftazidime, cefuroxime, cefotaxime, and cefepime, were measured as 72.3%, 67.8%, 67.7%, 65.5%, and 60%, respectively. In the present study, 51.1% of isolates were classified as multidrug-resistant K. pneumoniae strains. The molecular assays showed that 56.6% of isolates harbored bla_OXA-2. In addition, bla_OXA-4, bla_OXA-1, bla_OXA-10, and bla_OXA-48-like genes were also found in 16.7%, 5.6%, 1.1%, and 1.1% of isolates, respectively.

CONCLUSION

The spread of bla_OXAs, especially bla_OXA-48-like, among K. pneumoniae isolates indicated the inadequate dissemination control of multidrug-resistant bacteria in the Iranian hospital environment. There is a reason to assume that OXA producing K. pneumoniae will limit clinical therapeutic options in the future and pose threats to national public health among the Iranian population.

CPO Complete, a novel test for fast, accurate phenotypic detection and classification of carbapenemases

Carbapenemase-producing organisms (CPOs) are Gram-negative bacteria that are typically resistant to most or all antibiotics and are responsible for a global pandemic of high mortality. Rapid, accurate detection of CPOs and the classification of their carbapenemases are valuable tools for reducing the mortality of the CPO-associated infections, preventing the spread of CPOs, and optimizing use of new β-lactamase inhibitor combinations such as ceftazidime/avibactam, meropenem/vaborbactam and imipenem/relebactam. The current study evaluated the performance of CPO Complete, a novel, manual, phenotypic carbapenemase detection and classification test. The test was evaluated for sensitivity and specificity against 262 CPO isolates of Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter baumannii and 67 non-CPO isolates. It was also evaluated for carbapenemase classification accuracy against 205 CPOs that produced a single carbapenemase class. The test exhibited 100% sensitivity 98.5% specificity for carbapenemase detection within 90 minutes and detected 74.1% of carbapenemases within 10 minutes. In the classification evaluation, 99.0% of carbapenemases were correctly classified for isolates that produced a single carbapenemase. The test is technically simple and has potential for adaptation to automated instruments. With lyophilized kit storage at temperatures up to 38°C, the CPO Complete test has the potential to provide rapid, accurate carbapenemase detection and classification in both limited resource and technologically advanced laboratories.

Whole-genome sequencing study of KPC-encoding Klebsiella pneumoniae isolated in Greek private laboratories from non-hospitalised patients

OBJECTIVES

Greece is endemic for KPC-encoding Klebsiella pneumoniae; however, until now, reports have referred only to hospital isolates. In this study, seven KPC-encoding K. pneumoniae isolated in private laboratories from non-hospitalised patients were characterised.

METHODS

Whole-genome sequencing was performed on an Illumina MiniSeq Sequencing System. Multilocus sequence typing (MLST) was performed using a BLAST-based approach, and antimicrobial resistance genes and plasmid replicons were identified using ResFinder and PlasmidFinder, respectively. The Rapid Annotation using Subsystem Technology (RAST) v.2.0 server was used for genome annotation of virulence, pathogenesis and defence genes.

RESULTS

Six isolates belonged to the major MLST sequence type 258 (ST258) and one to ST39. The resistome included genes encoding resistance mechanisms to β-lactams, aminoglycosides, quinolones, sulfonamides, trimethoprim, fosfomycin and phenicols, conferring multidrug-resistant phenotypes. Moreover, various genes involved in virulence, pathogenesis and defence have been identified.

CONCLUSIONS

It is highly probable that these isolates were acquired during previous hospitalisation in Greek hospitals. The presence of KPC-encoding K. pneumoniae in non-hospitalised patients is alarming, although it is not yet possible to assess its actual impact.

Antimicrobial activity of two novel antimicrobial peptides AA139 and SET-M33 against clinically and genotypically diverse Klebsiella pneumoniae isolates with differing antibiotic resistance profiles

Colistin is an antimicrobial peptide (AMP) used as a drug of last resort, although plasmid-mediated colistin resistance (MCR) has been reported. AA139 and SET-M33 are novel AMPs currently in development for the treatment of multidrug-resistant (MDR) Gram-negative bacterial infections. As many AMPs have a similar mode of action to colistin, potentially leading to cross-resistance, the antimicrobial activity of AA139 and SET-M33 was investigated against a collection of 50 clinically and genotypically diverse Klebsiella pneumoniae isolates with differing antibiotic resistance profiles, including colistin-resistant strains. The collection was genotypically characterised and susceptibility to clinically relevant antibiotics was determined. Susceptibility to AA139 and SET-M33 did not differ among the collection despite differences in underlying mechanisms of resistance or susceptibility to colistin. For three colistin-susceptible and three colistin-resistant strains with distinct MDR profiles as well as an additional MCR-producing strain, the bactericidal activity of AA139, SET-M33 and colistin during 24 h of exposure was examined. Following 24 h of exposure to AA139, SET-M33 or colistin, the seven strains were tested for changes in susceptibility to the respective AMPs. AA139 and SET-M33 showed a concentration-dependent bactericidal effect irrespective of bacterial susceptibility to colistin. Exposure to low colistin concentrations resulted in the development of colistin resistance in colistin-susceptible strains, whereas susceptibility to AA139 and SET-M33 following exposure to the respective AMPs was maintained. The two novel AMPs remained effective against colistin-resistant strains and may be promising novel drugs for the treatment of clinically and genotypically diverse MDR K. pneumoniae infections, including infections associated with colistin-resistant bacteria.

Tridecaptin M, a New Variant Discovered in Mud Bacterium, Shows Activity against Colistin- and Extremely Drug-Resistant Enterobacteriaceae

The World Health Organization has categorized the Gram-negative superbugs, which are inherently impervious to many antibiotics, as critical priority pathogens due to the lack of effective treatments. The breach in our last-resort antibiotic (i.e., colistin) by extensively drug-resistant and pan-drug-resistant Enterobacteriaceae strains demands the immediate development of new therapies.

The World Health Organization has categorized the Gram-negative superbugs, which are inherently impervious to many antibiotics, as critical priority pathogens due to the lack of effective treatments. The breach in our last-resort antibiotic (i.e., colistin) by extensively drug-resistant and pan-drug-resistant Enterobacteriaceae strains demands the immediate development of new therapies. In the present study, we report the discovery of tridecaptin M, a new addition to the family, and its potential against colistin-resistant Enterobacteriaceae in vitro and in vivo. Also, we performed mode-of-action studies using various fluorescent probes and studied the hemolytic activity and mammalian cytotoxicity in two cell lines. Tridecaptin M displayed strong antibacterial activity (MICs of 2 to 8 μg ml⁻¹) against clinical strains of Klebsiella pneumoniae (which were resistant to colistin, carbapenems, third- and fourth-generation cephalosporins, fluoroquinolones, fosfomycin, and other antibiotics) and mcr-1-positive Escherichia coli strains. Unlike polymyxins, tridecaptin M did not permeabilize the outer membrane or cytoplasmic membrane. It blocked ATP synthesis in bacteria by dissipating the proton motive force. The compound exhibited negligible acquired resistance, low in vitro cytotoxicity and hemolytic activity, and no significant acute toxicity in mice. It also showed promising efficacy in a thigh infection model of colistin-resistant K. pneumoniae. Altogether, these results demonstrate the future prospects of this class of antibiotics to address the unmet medical need to circumvent colistin resistance in extensively drug-resistant Enterobacteriaceae infections. The work also emphasizes the importance of natural products in our shrunken drug discovery pipeline.

Genomic epidemiology of multidrug-resistant Gram-negative organisms

The emergence and spread of antibiotic-resistant Gram-negative bacteria (rGNB) across global healthcare networks presents a significant threat to public health. As the number of effective antibiotics available to treat these resistant organisms dwindles, it is essential that we devise more effective strategies for controlling their proliferation. Recently, whole-genome sequencing has emerged as a disruptive technology that has transformed our understanding of the evolution and epidemiology of diverse rGNB species, and it has the potential to guide strategies for controlling the evolution and spread of resistance. Here, we review specific areas in which genomics has already made a significant impact, including outbreak investigations, regional epidemiology, clinical diagnostics, resistance evolution, and the study of epidemic lineages. While highlighting early successes, we also point to the next steps needed to translate this technology into strategies to improve public health and clinical medicine.

Insight into Acinetobacter baumannii: pathogenesis, global resistance, mechanisms of resistance, treatment options, and alternative modalities

Acinetobacter baumannii, once considered a low-category pathogen, has emerged as an obstinate infectious agent. The scientific community is paying more attention to this pathogen due to its stubbornness to last resort antimicrobials, including carbapenems, colistin, and tigecycline, its high prevalence of infections in the hospital setting, and significantly increased rate of community-acquired infections by this organism over the past decade. It has given the fear of pre-antibiotic era to the world. To further enhance our understanding about this pathogen, in this review, we discuss its taxonomy, pathogenesis, current treatment options, global resistance rates, mechanisms of its resistance against various groups of antimicrobials, and future therapeutics.

Characterization of Extensively Drug-Resistant or Pandrug-Resistant Sequence Type 147 and 101 OXA-48-Producing Klebsiella pneumoniae Causing Bloodstream Infections in Patients in an Intensive Care Unit

Carbapenem-resistant Klebsiella pneumoniae causes important health care-associated infections worldwide. An outbreak of sequence type 11 (ST11) OXA-48-producing K. pneumoniae (OXA-48-Kp) isolates occurred in Tzaneio Hospital in 2012 and was contained until 2014, when OXA-48-Kp reemerged. The present study involved 19 bloodstream infection (BSI) OXA-48-Kp isolates recovered from 19 intensive care unit (ICU) patients hospitalized between August 2014 and July 2016. MICs were determined by broth microdilution. Beta-lactamase genes were detected by PCR. All isolates were typed by pulsed-field gel electrophoresis/multilocus sequence typing (PFGE/MLST), and 10 representative isolates were typed by next-generation sequencing (NGS). Of the 19 study patients, 9 had previous hospitalizations, and 10 carried OXA-48-Kp prior to BSI isolation; median time from ICU admission to BSI was 29 days. Four OXA-48-Kp isolates belonged to PFGE profile A (ST147) and were pandrug resistant (PDR), while 15 isolates exhibited PFGE profile B (ST101) and were extensively drug resistant. Genes detected via NGS resistome analysis accounted for most of the resistance phenotypes, except for tigecycline and fosfomycin. Insertional inactivation of mgrB (distinct per clone) conferred colistin resistance in all 19 isolates. NGS single nucleotide polymorphism (SNP) analysis validated the clonal relatedness of the ST147 and ST101 strains and revealed the possible presence of two index ST147 strains and the microevolution of ST101 strains. Distinct, but highly related, IncL OXA-48-encoding plasmid lineages were identified; plasmids of the ST147 strains were identical with the plasmid of ST11 OXA-48-Kp which caused the 2012 outbreak. In conclusion, biclonal circulation of OXA-48-Kp and, alarmingly, emergence of a PDR clone are reported. These observations, along with the challenging phenotypic detection of OXA-48 producers and the high reported transmissibility of bla_OXA-48, necessitate intensive efforts to prevent their further spread.

Case Report of an Extensively Drug-Resistant Klebsiella pneumoniae Infection With Genomic Characterization of the Strain and Review of Similar Cases in the United States

Reports of extensively drug-resistant and pan-drug-resistant Klebsiella pneumoniae (XDR-KP and PDR-KP) cases are increasing worldwide. Here, we report a case of XDR-KP with an in-depth molecular characterization of resistance genes using whole-genome sequencing, and we review all cases of XDR-KP and PDR-KP reported in the United States to date.

Mortality due to KPC carbapenemase-producing Klebsiella pneumoniae infections: Systematic review and meta-analysis: Mortality due to KPC Klebsiella pneumoniae infections

INTRODUCTION

KPC carbapenemase-producing Klebsiella pneumoniae (KPC-KP) has become a major public health challenge. Accordingly, this study sought to use a systematic review of the scientific literature to ascertain the mortality of KPC-KP infection, and analyze such mortality by country, year of publication, hospital ward, and type of interpretation used to define carbapenem resistance.

METHODOLOGY

A search without language restrictions was made of the MEDLINE, CENTRAL, EBSCO, LILACS and EMBASE databases from 1996 through June 2017, to locate all studies which had determined the existence of KPC-KP infection. We then performed a meta-analysis of all studies that reported KPC-KP infection-related mortality, and analyzed mortality by subgroup in accordance with standard methodology.

RESULTS

A total of 51 papers were included in the systematic review. From 2005 through 2017, data on KPC-KP infection were reported in 5124 patients, with an average of 465 patients per year. The most widely studied type of infection was bacteremia (28∙0%). The meta-analysis showed that overall mortality for the 37 studies was 41.0% (95%CI 37.0-44.0), with the highest mortality rates being observed in oncology patients, 56.0% (95%CI 38.1-73.0), and Brazil, 51.3% (95%CI 43.0-60.0).

CONCLUSION

KPC-KP infection-related mortality is high, is manifested differently in some countries, and is highest among oncology patients.

Expansion of KPC-producing Klebsiella pneumoniae with various mgrB mutations giving rise to colistin resistance: the role of ISL3 on plasmids

mcr-1 has been reported as the first plasmid-encoded gene conferring colistin resistance. In KPC-producing Klebsiella pneumoniae (KPC-KP), however, colistin resistance is rapidly emerging through other mechanisms. Resistance is frequently due to disruption of the mgrB gene by insertion sequences, e.g. ISL3. The aim of this study was to investigate the expansion of mgrB-mutated KPC-KP isolates. In addition, the localisation and targets of ISL3 sequences within the core and accessory genome of common KPC-KP lineages were identified. A total of 29 clinical K. pneumoniae isolates collected from Italian patients were randomly selected. Whole genome sequences were analysed for resistance genes, plasmids and insertion sequences. In addition, 27 colistin-resistant KPC-KP isolates from a previous study from Crete (Greece) were assessed. Clonal expansion of KPC-KP isolates with various mutations in mgrB among all lineages was observed. In two Italian MLST ST512 isolates and eight Greek ST258 isolates, an identical copy of ISL3 was inserted in mgrB nucleotide position 133. ISL3, a transposable restriction-modification system of 8154 nucleotides, was located on pKpQIL-like plasmids and may transpose into the chromosome. In four isolates, chromosomal integration of ISL3 in diverse inner membrane proteins other than mgrB was identified. Colistin resistance is most often explained by clonal expansion of isolates with mutated mgrB. pKpQIL-like plasmids, which are omnipresent in KPC-KP, carry insertion sequences such as ISL3 that have mgrB as a target hotspot for transposition. Transposition of insertion sequences from plasmids and subsequent clonal expansion may contribute to the emerging colistin resistance in KPC-KP.

Analysis of OXA-204 carbapenemase-producing Enterobacteriaceae reveals possible endoscopy-associated transmission, France, 2012 to 2014

OXA-48-like beta-lactamase producing bacteria are now endemic in several European and Mediterranean countries. Among this carbapenemase family, the OXA-48 and OXA-181 variants predominate, whereas other variants such as OXA-204 are rarely reported. Here, we report the molecular epidemiology of a collection of OXA-204-positive enterobacterial isolates (n = 29) recovered in France between October 2012 and May 2014. This study describes the first outbreak of OXA-204-producing Enterobacteriaceae in Europe, involving 12 isolates of an ST90 Escherichia coli clone and nine isolates of an ST147 Klebsiella pneumoniae clone. All isolates co-produced the cephalosporinase CMY-4, and 60% of them co-produced the extended-spectrum beta-lactamase CTX-M-15. The bla_OXA-204 gene was located on a 150-kb IncA/C plasmid, isolated from various enterobacterial species in the same patient, indicating a high conjugative ability of this genetic vehicle.

Prophylactic Measures During Induction for Acute Myeloid Leukemia

PURPOSE OF REVIEW

Improved management of infectious complications of acute myeloid leukemia (AML) has contributed substantially to the success of care over the past half century. An important approach to reducing infectious complications during the induction period of chemotherapy involves the use of prophylactic antibacterial, antiviral, and antifungal agents targeting likely pathogens.

RECENT FINDINGS

There is not a one-size-fits-all approach to prophylaxis; every patient undergoing induction therapy should be evaluated individually and within the context of local microbiologic epidemiology and host risk factors. Pharmacologic and non-pharmacologic interventions as well as novel diagnostic platforms can help mitigate the risk of life-threatening infection in patients with AML who undergo induction chemotherapy.

Colistin Resistance in KPC-2- and SHV-5-Producing Klebsiella pneumoniae Clinical Isolates in Bulgaria

Background/Aims: Colistin resistance is increasingly recognized among carbapenemase-producing Klebsiella pneumoniae isolates in several European regions. The current study documents the appearance of colistin resistance among KPC-2 and SHV-5-produning K. pneumoniae strains in Bulgaria. Methods: Four colistin-resistant K. pneumoniae isolates were recovered from 2 patients hospitalized in the anesthesiology and resuscitation clinic of a tertiary care university hospital in Sofia, Bulgaria. Microbial identification and antimicrobial susceptibility testing was performed by Vitek 2 (Biomerieux, France). β-Lactamase genes were amplified using a panel of primers for detection of all MBL-types, KPCs, plasmid-mediated AmpCs in single PCR reactions, OXA-type carbapenemases, extended-spectrum β-lactamases (ESBLs) and TEM enzymes. The colistin-resistant mcr-1 gene was also investigated using previously described primers and conditions. Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were used to investigate clonality. Results: The 4 K. pneumoniae isolates exhibited colistin MICs >16 mg/L and showed multidrug-resistant phenotypes, remaining intermediately susceptible only to gentamicin. They were clustered into a single PFGE clonal type and MLST assigned them to sequence type 258. All isolates possessed KPC-2 carbapenemase and SHV-5 ESBL. They were negative for the plasmid-mediated colistin-resistant mcr-1 gene, possibly implying an intrinsic mechanism of resistance. Conclusions: Although colistin use in Bulgaria only started moderately during 2014, the findings of the current study notify the appearance of colistin resistance among carbapenemase-producing Klebsiella species in another European region.

Multihospital Occurrence of Pan-Resistant Klebsiella pneumoniae Sequence Type 147 with an ISEcp1-Directed blaOXA-181 Insertion in the mgrB Gene in the United Arab Emirates

The emergence of pan-resistant Klebsiella pneumoniae strains is an increasing concern. In the present study, we describe a cluster of 9 pan-resistant K. pneumoniae sequence type 147 (ST147) isolates encountered in 4 patients over nearly 1 year in 3 hospitals of the United Arab Emirates (UAE). The isolates exhibited highly similar genotypes. All produced chromosomally encoded OXA-181, and the majority also produced the NDM-5 carbapenemase. As with the previously described single isolate from the UAE, MS6671, the mgrB was disrupted by a functional, ISEcp1-driven bla_OXA-181 insertion causing resistance to carbapenems. The mutation was successfully complemented with an intact mgrB gene, indicating that it was responsible for colistin resistance. bla_NDM-5 was located within a resistance island of an approximately 100-kb IncFII plasmid carrying ermB, mph(A), bla_TEM-1B, rmtB, bla_NDM-5, sul1, aadA2, and dfrA12 resistance genes. Sequencing this plasmid (pABC143-NDM) revealed that its backbone was nearly identical to that of plasmid pMS6671E from which several resistance genes, including bla_NDM-5, had been deleted. More extensive similarities of the backbone and the resistance island were found between pABC143C-NDM and the bla_NDM-5-carrying IncFII plasmids of two K. pneumoniae ST147 isolates from South Korea, one of which was colistin resistant, and both also produced OXA-181. Notably, one of these strains was isolated from a patient transferred from the UAE. Our data show that this pan-resistant clone has an alarming capacity to maintain itself over an extended period of time and is even likely to be transmitted internationally.

Opportunities for natural products in 21st century antibiotic discovery

Natural products and their derivatives are mainstays of our antibiotic drugs, but they are increasingly in peril. The combination of widespread multidrug resistance in once susceptible bacterial pathogens, disenchantment with natural products as sources of new drugs, lack of success using synthetic compounds and target-based discovery methods, along with shifting economic and regulatory issues, conspire to move investment in research and development away from the antibiotics arena. The result is a growing crisis in antibiotic drug discovery that threatens modern medicine. 21^st century natural product research is perfectly positioned to fill the antibiotic discovery gap and bring new drug candidates to the clinic. Innovations in genomics and techniques to explore new sources of antimicrobial chemical matter are revealing new chemistry. Increasing appreciation of the value of narrow-spectrum drugs and re-examination of once discarded chemical scaffolds coupled with synthetic biology methods to generate new compounds and improve yields offer new strategies to revitalize once moribund natural product programs. The increasing awareness that the combination of antibiotics with adjuvants, non-antibiotic compounds that overcome resistance and enhance drug activity, can rescue older chemical scaffolds, and concepts such as blocking pathogen virulence present orthogonal strategies to traditional antibiotics. In all these areas, natural products offer chemical matter, shaped by natural selection, that is privileged in this therapeutic area. Natural product research is poised to regain prominence in delivering new drugs to solve the antibiotic crisis.

Evolution and Epidemiology of Multidrug-Resistant Klebsiella pneumoniae in the United Kingdom and Ireland

Klebsiella pneumoniae is a human commensal and opportunistic pathogen that has become a leading causative agent of hospital-based infections over the past few decades. The emergence and global expansion of hypervirulent and multidrug-resistant (MDR) clones of K. pneumoniae have been increasingly reported in community-acquired and nosocomial infections. Despite this, the population genomics and epidemiology of MDR K. pneumoniae at the national level are still poorly understood. To obtain insights into these, we analyzed a systematic large-scale collection of invasive MDR K. pneumoniae isolates from hospitals across the United Kingdom and Ireland. Using whole-genome phylogenetic analysis, we placed these in the context of previously sequenced K. pneumoniae populations from geographically diverse countries and identified their virulence and drug resistance determinants. Our results demonstrate that United Kingdom and Ireland MDR isolates are a highly diverse population drawn from across the global phylogenetic tree of K. pneumoniae and represent multiple recent international introductions that are mainly from Europe but in some cases from more distant countries. In addition, we identified novel genetic determinants underlying resistance to beta-lactams, gentamicin, ciprofloxacin, and tetracyclines, indicating that both increased virulence and resistance have emerged independently multiple times throughout the population. Our data show that MDR K. pneumoniae isolates in the United Kingdom and Ireland have multiple distinct origins and appear to be part of a globally circulating K. pneumoniae population.

Klebsiella pneumoniae is a major human pathogen that has been implicated in infections in healthcare settings over the past few decades. Antimicrobial treatment of K. pneumoniae infections has become increasingly difficult as a consequence of the emergence and spread of strains that are resistant to multiple antimicrobials. To better understand the spread of resistant K. pneumoniae, we studied the genomes of a large-scale population of extensively antimicrobial-resistant K. pneumoniae in the United Kingdom and Ireland by utilizing the fine resolution that whole-genome sequencing of pathogen genomes provides. Our results indicate that the K. pneumoniae population is highly diverse and that, in some cases, resistant strains appear to have spread across the country over a few years. In addition, we found evidence that some strains have acquired antimicrobial resistance genes independently, presumably in response to antimicrobial treatment.

Epidemiology of Carbapenem Resistant Klebsiella pneumoniae Infections in Mediterranean Countries

Infections by Carbapenem-Resistant Enterobacteriaceae (CRE), in particular, carbapenem-resistant Klebsiella pneumoniae (CRKp), are a significant public health challenge worldwide. Resistance to carbapenems in enterobacteriaceae is linked to different mechanisms, including the production of the various types of enzymes like KPC, VIM, IMP, NDM, and OXA-48. Despite several attempts to control the spread of these infections at the local and national level, the epidemiological situation for CRKp had worsened in the last years in the Mediterranean area. The rate and types of CRKp isolates greatly differ in the various Mediterranean countries. KPC-producing K. pneumoniae is diffused particularly in the European countries bordering the Mediterranean Sea and is endemic in Greece and Italy. On the contrary, OXA-48-producing K. pneumoniae is endemic in Turkey and Malta and diffused at inter-regional level particularly in some

North African and Middle East countries. The spread of these multiresistant pathogens in the world and the Mediterranean countries has been related to various epidemiological factors including the international transfer of patients coming from endemic areas.