Identification of Genetic Alterations Associated with Acquired Colistin Resistance in Klebsiella pneumoniae Isogenic Strains by Whole-Genome Sequencing

Clinical outcomes of intensive care unit patients infected with multidrug-resistant gram-negative bacteria treated with ceftazidime/avibactam and ceftolozane/tazobactam

In intensive care units (ICUs), infection rates range from 18 to 54%, which is five to ten times higher than those observed in other hospital units, with a mortality rate of 9% to 60%. In recent decades, the susceptibility pattern has changed and Gram-Negative Bacteria (GNB) have become a threat due to their high frequency of multidrug resistance associated with a scarcity of therapeutic options. However, the drugs Ceftolozane/Tazobactam (C/T) and Ceftazidime/Avibactam (C/A) are demonstrating good clinical and microbiological response in the treatment of severe nosocomial infections. Therefore, this study aims to evaluate the clinical outcome of patients with severe infections caused by Multidrug-Resistant (MDR) GNB treated with C/T and C/A. Our study evaluates a total of 131 patients who received treatment with C/T and C/A due to infections caused by MDR GNB within the period from 2018 to 2021. The main infections were urinary tract (46,6%) and respiratory (26,7%) infections. Pseudomonas aeruginosa was the prevailing agent in the sample evaluation (34.3%), followed by Klebsiella pneumoniae (30,1%). About 54,9% of patients showed a favorable response, with culture negativation in 66,4% of the samples, with no discrepancy in negativations when comparing ages: 67,7% in young and 66% in elderly patients. Among the patients, 62,6% received monotherapy with C/T and C/A with a better response observed with monotherapy compared to combination therapy (58,6% vs 41,4%). The overall mortality rate was 45%, with MDR GNB infections responsible for 33,9% of these deaths, and the others (66,1%) due to factors such as oncological, hematological, and degenerative neurological diseases. In regards to hematological aspect, 35,1% of patients showed changes, with 28,2% of them presenting anemia, 4,5% thrombocytopenia, and 2,5% thrombocytosis. Concerning the use of invasive devices, higher mortality was observed in patients on mechanical ventilation (52%). In this manner, it was possible to observe that therapy with C/T and C/A yielded a favorable clinical outcome in patients with severe infections caused by MDR GNB in the study. These drugs also demonstrated good tolerability regardless of age or the presence of preexisting comorbidities and were deemed safe when assessing adverse effects. Our data also demonstrate the importance of determining the mechanism of resistance to carbapenems so that these drugs can be used more effectively and rationally.

The menace of colistin resistance across globe: Obstacles and opportunities in curbing its spread

Colistin-resistance in bacteria is a big concern for public health, since it is a last resort antibiotic to treat infectious diseases of multidrug resistant and carbapenem resistant Gram-negative pathogens in clinical settings. The emergence of colistin resistance in aquaculture and poultry settings has escalated the risks associated with colistin resistance in environment as well. The staggering number of reports pertaining to the rise of colistin resistance in bacteria from clinical and non-clinical settings is disconcerting. The co-existence of colistin resistant genes with other antibiotic resistant genes introduces new challenges in combatting antimicrobial resistance. Some countries have banned the manufacture, sale and distribution of colistin and its formulations for food producing animals. However, to tackle the issue of antimicrobial resistance, a one health approach initiative, inclusive of human, animal, and environmental health needs to be developed. Herein, we review the recent reports in colistin resistance in bacteria of clinical and non-clinical settings, deliberating on the new findings obtained regarding the development of colistin resistance. This review also discusses the initiatives implemented globally in mitigating colistin resistance, their strength and weakness.

Prevalence of Mutated Colistin-Resistant Klebsiella pneumoniae: A Systematic Review and Meta-Analysis

The emergence of genetic mutations in chromosomal genes and the transmissible plasmid-mediated colistin resistance gene may have helped in the spread of colistin resistance among various Klebsiella pneumoniae (K. pneumoniae) isolates and other different bacteria. In this study, the prevalence of mutated colistin-resistant K. pneumoniae isolates was studied globally using a systematic review and meta-analysis approach. A systematic search was conducted in databases including PubMed, ScienceDirect, Scopus and Google Scholar. The pooled prevalence of mutated colistin resistance in K. pneumoniae isolates was analyzed using Comprehensive Meta-Analysis Software (CMA). A total of 50 articles were included in this study. The pooled prevalence of mutated colistin resistance in K. pneumoniae was estimated at 75.4% (95% CI = 67.2−82.1) at high heterogeneity (I2 = 81.742%, p-value < 0.001). Meanwhile, the results of the subgroup analysis demonstrated the highest prevalence in Saudi Arabia with 97.9% (95% CI = 74.1−99.9%) and Egypt, with 4.5% (95% CI = 0.6−26.1%), had the lowest. The majority of mutations could be observed in the mgrB gene (88%), pmrB gene (54%) and phoQ gene (44%). The current study showed a high prevalence of the mutation of colistin resistance genes in K. pneumoniae. Therefore, it is recommended that regular monitoring be performed to control the spread of colistin resistance.

Insertion sequence mediating mrgB disruption is the major mechanism of polymyxin resistance in carbapenem-resistant Klebsiella pneumoniae isolates from China

OBJECTIVES

Infections caused by carbapenem-resistant Klebsiella pneumoniae (CRKP) pose a huge health challenge worldwide. The aim of this study was to evaluate the incidence of polymyxin resistance in clinical CRKP isolates in China and to characterize the molecular mechanisms underlying these polymyxin-resistant CRKP (PR-CRKP) isolates.

METHODS

A total of 493 CRKP clinical isolates from patients were collected from six tertiary-care hospitals in China during 2017-2018. Minimum inhibitory concentrations of polymyxin B and colistin were determined using the broth microdilution method. PR-CRKP isolates were identified and subjected to whole-genome sequencing. Quantitative real-time PCR and structural modelling analysis were also performed.

RESULTS

We observed a 2.2% (11/493) polymyxin resistance rate in this multicentre cohort. Polymyxin B MICs ranged from 4 to 64 μg/mL and colistin MICs ranged from 8 to 128 μg/mL in 11 PR-CRKP isolates. Key genetic variations identified in PR-CRKP isolates involved eight disruptions (seven insertional inactivation by an insertion sequence [IS] element, one frameshift deletion) in mgrB, and three missense mutations in pmrA, pmrB, and phoP. ISKpn26 was the predominant IS (4/7), and three of these occurred in nucleotide position 74 in the mgrB gene. In addition, we reported a novel mutation S62R in pmrB that may confer polymyxin resistance in K. pneumoniae.

CONCLUSIONS

Our findings highlight the multifaceted molecular mechanisms of polymyxin resistance in CRKP.

Prevalence of insertion sequence elements in plasmids relating to mgrB gene disruption causing colistin resistance in Klebsiella pneumoniae

Colistin is a last resort antibiotic for the treatment of carbapenemase producing Klebsiella pneumoniae. The disruption of the mgrB gene by insertion sequences (ISs) is a mechanism mediating colistin resistance. Plasmids encode mobilizable IS elements which integrate into the mgrB gene in K. pneumoniae causing gene inactivation and colistin resistance. The species prevalence of mgrB-gene disrupting insertion elements ISL3 (ISKpn25), IS5 (ISKpn26), ISKpn14, and IS903B present on plasmids were assessed. IS containing plasmids were also scanned for antimicrobial resistance genes, including carbapenem resistant genes. Plasmids encoding ISs are abundant in K. pneumoniae. IS903B was found in 28 unique Inc groups, while ISKpn25 was largely carried by IncFIB(pQil) plasmids. ISKpn26 and ISKpn14 were most often found associated with IncFII(pHN7A8) plasmids. Of the 34 unique countries which contained any of the IS elements, ISKpn25 was identified from 26. ISKpn26, ISKpn14, and IS903B ISs were identified from 89.3%, 44.9%, and 23.9% plasmid samples from China. Plasmids carrying ISKpn25, ISKpn14, and ISKpn26 IS have a 4.6-, 6.0-, and 6.6-fold higher carbapenemase gene count, respectively, relative to IS903B-carrying plasmids. IS903B bearing plasmids have a 20-, 5-, and 5-fold higher environmental source isolation count relative to ISKpn25, ISKpn14, and ISKpn26 bearing plasmids. ISKpn25 present on IncFIB(pQil) sourced from clinical settings is established across multiple countries, while ISKpn26, ISKpn14, and IS903B appear most often in China. Carbapenemase presence in tandem with IS elements may help promote an extensively drug resistant profile in K. pneumoniae limiting already narrow treatment options.

Lipid A-Ara4N as an alternate pathway for (colistin) resistance in Klebsiella pneumonia isolates in Pakistan

Objectives

This study aimed to explore mechanism of colistin resistance amongst Klebsiella pneumoniae isolates through plasmid mediated mcr-1 gene in Pakistan. Carbapenem and Colistin resistant K. pneumoniae isolates (n  = 34) stored at − 80 °C as part of the Aga Khan University Clinical Laboratory strain bank were randomly selected and subjected to mcr-1 gene PCR. To investigate mechanisms of resistance, other than plasmid mediated mcr-1 gene, whole genome sequencing was performed on 8 clinical isolates, including 6 with colistin resistance (MIC  >  4 μg/ml) and 2 with intermediate resistance to colistin (MIC  >  2 μg/ml).

Results

RT-PCR conducted revealed absence of mcr-1 gene in all isolates tested. Whole genome sequencing results revealed modifications in Lipid A-Ara4N pathway. Modifications in Lipid A-Ara4N pathway were detected in ArnA_ DH/FT, UgdH, ArnC and ArnT genes. Mutation in ArnA_ DH/FT gene were detected in S3, S5, S6 and S7 isolates. UgdH gene modifications were found in all isolates except S3, mutations in ArnC were present in all except S1, S2 and S8 and ArnT were detected in all except S4 and S7. In the absence of known mutations linked with colistin resistance, lipid pathway modifications may possibly explain the phenotype resistance to colistin, but this needs further exploration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-021-05867-3.

Comparative genome analysis of colistin-resistant OXA-48-producing Klebsiella pneumoniae clinical strains isolated from two Iranian hospitals

BACKGROUND

Carbapenemase-producing Klebsiella pneumoniae (CP-KP) is becoming extensively disseminated in Iranian medical centers. Colistin is among the few agents that retains its activity against CP-KP. However, the administration of colistin for treatment of carbapenem-resistant infections has increased resistance against this antibiotic. Therefore, the identification of genetic background of co-carbapenem, colistin-resistance K. pneumoniae (Co-CCRKp) is urgent for implementation of serious infection control strategies.

METHODS

Fourteen Co-CCRKp strains obtained from routine microbiological examinations were subjected to molecular analysis of antimicrobial resistance (AMR) using whole genome sequencing (WGS).

RESULTS

Nine of 14 K. pneumoniae strains belonged to sequence type (ST)-11 and 50% of the isolates had K-locus type 15. All strains carried blaOXA-48 except for P26. blaNDM-1 was detected in only two plasmids associated with P6 and P26 strains belonging to incompatibility (Inc) groups; IncFIB, IncHI1B and IncFII. No blaKPC, blaVIM and blaIMP were identified. Multi-drug resistant (MDR) conjugative plasmids were identified in strains P6, P31, P35, P38 and P40. MICcolistin of K. pneumoniae strains ranged from 4 to 32 µg/ml. Modification of PmrA, PmrB, PhoQ, RamA and CrrB regulators as well as MgrB was identified as the mechanism of colistin resistance in our isolates. Single amino acid polymorphysims (SAPs) in PhoQ (D150G) and PmrB (R256G) were identified in all strains except for P35 and P38. CrrB was absent in P37 and modified in P7 (A200E). Insertion of ISKpn72 (P32), establishment of stop codon (Q30*) (P35 and P38), nucleotides deletion (P37), and amino acid substitution at position 28 were identified in MgrB (P33 and P42). None of the isolates were positive for plasmid-mediated colistin resistance (mcr) genes. P35 and P38 strains carried iutA, iucD, iucC, iucB and iucA genes and are considered as MDR-hypervirulent strains. P6, P7 and P43 had ICEKp4 variant and ICEKp3 was identified in 78% of the strains with specific carriage in ST11.

CONCLUSION

In our study, different genetic modifications in chromosomal coding regions of some regulator genes resulted in phenotypic resistance to colistin. However, the extra-chromosomal colistin resistance through mcr genes was not detected. Continuous genomic investigations need to be conducted to accurately depict the status of colistin resistance in clinical settings.