Insertion of ISPa1635 in ISCR1 Creates a Hybrid Promoter for blaPER-1 Resulting in Resistance to Novel ß-lactam/ß-lactamase Inhibitor Combinations and Cefiderocol.

Eleven blaPER-1-positive Pseudomonas aeruginosa clinical isolates showed variable susceptibility to ceftazidime-avibactam (CZA). The genetic contexts of blaPER-1 were identical (ISCR1-blaPER-1-gst) except for the ST697 isolate HS204 (ISCR1-ISPa1635-blaPER-1-gst). The insertion of ISPa1635 in ISCR1 upstream of blaPER-1 created a hybrid promoter, which elevated the blaPER-1 transcription level and resulted in increased resistance to CZA, ceftolozane-tazobactam, cefepime-zidebactam, and cefiderocol. Diversity in the promoter activity of blaPER-1 partially explains the variable susceptibility to CZA in PER-producing isolates.

CTX-M-190, a Novel ß-Lactamase Resistant to Tazobactam and Sulbactam, Identified in an Escherichia coli Clinical Isolate.

A novel ß-lactamase, CTX-M-190, derived from CTX-M-55 by a single substitution of Ser for Thr at position 133 (Ser133Thr), was identified in a natural Escherichia coli clinical isolate. CTX-M-190 exhibited potent hydrolytic activity against cefotaxime, with a kcat/Km ratio of 14.5 µM-1 s-1, and was highly resistant to inhibition by the ß-lactamase inhibitors tazobactam and sulbactam, whose 50% inhibitory concentrations were 77- and 55-fold higher, respectively, for CTX-M-190 than for CTX-M-55. blaCTX-M-190 was located within the genetic platform ISEcp1-blaCTX-M-orf477, which was harbored by a 70-kb IncI1 plasmid.

High ceftazidime hydrolysis activity and porin OmpK35 deficiency contribute to the decreased susceptibility to ceftazidime/avibactam in KPC-producing Klebsiella pneumoniae.

Objectives: To investigate mechanisms for the decreased susceptibility to ceftazidime/avibactam in KPC-producing Klebsiella pneumoniae (KPC-KP). Methods: A total of 24 isolates, 8 each with ceftazidime/avibactam MICs of 4-8, 1-2 and ≤0.5 mg/L, were randomly selected from 214 clinical isolates of KPC-KP, and the ß-lactamase hydrolysis activity and porin expression profiles were determined. Plasmid profile and relative expression and copy number of the bla KPC gene were also analysed. Results: Ceftazidime/avibactam MIC 50 and MIC 90 were 2 and 4 mg/L, respectively, for the 214 KPC-KP isolates. The hydrolysis activities of nitrocefin and ceftazidime in both of the ceftazidime/avibactam MIC 4-8 and 1-2 mg/L groups were significantly higher than those of the MIC ≤0.5 mg/L group, while the hydrolysis activities were 4-4.6-fold higher in the MIC 4-8 mg/L group than in the other two groups when 4 mg/L avibactam was added. The relative expression and copy number of the bla KPC gene in the MIC 4-8 mg/L group were 4.2-4.8-fold higher than in the other two groups. Meanwhile, SDS-PAGE showed that all isolates in the two groups with MIC ≥1 mg/L lacked OmpK35, which had either an early frameshift with a premature stop codon ( n = 15, ST11) or overexpression of the negative regulation genes, micF and ompR ( n = 1, ST15), whereas OmpK35 and OmpK36 could both be observed in all isolates with MIC ≤0.5 mg/L. Conclusions: Decreased ceftazidime/avibactam susceptibility in KPC-KP clinical isolates is caused by high ceftazidime hydrolysis activity and OmpK35 porin deficiency and the majority of isolates belong to ST11.

Predictors of mortality in patients with carbapenem-resistant Klebsiella pneumoniae infection: a meta-analysis and a systematic review.

BACKGROUND: Cases of carbapenem-resistant Klebsiella pneumoniae infection have been increasing. Patients with carbapenem-resistant Klebsiella pneumoniae infection have a poor prognosis and a high mortality rate. Identification of potential risk factors associated with carbapenem-resistant Klebsiella pneumoniae infection-related mortality may help improve patient outcomes. METHODS: Embase, PubMed, and the Cochrane Library databases were searched to identify articles describing predictors of mortality in patients with carbapenem-resistant Klebsiella pneumoniae infection. The quality of articles was assessed with the Newcastle-Ottawa Scale score (NOS). Review Manager was used for statistical analyses. RESULTS: Twenty-seven observational studies were included in the analysis. Factors associated with higher mortality were septic shock [odds ratio (OR): 4.41, 95% CI: 3.17-6.15], congestive heart failure (OR: 2.65, 95% CI: 1.71-4.13), chronic obstructive pulmonary disease (COPD; OR: 2.43, 95% CI: 1.87-3.15), chronic kidney disease (CKD; OR: 1.78, 95% CI: 1.43-2.22), diabetes mellitus (OR: 1.41, 95% CI: 1.16-1.72), mechanical ventilation (OR: 1.65, 95% CI: 1.25-2.18), and inappropriate empirical antimicrobial treatment (OR: 1.25, 95% CI: 1.03-1.52). The average Acute Physiology and Chronic Health Evaluation (APACHE) II score at the time of diagnosis of carbapenem-resistant Klebsiella pneumoniae infection was considerably higher in patients who did not survive than in those who survived (weighted mean difference: 5.86, 95% CI: 2.46-9.26). DISCUSSION: Patient condition, timing appropriate antimicrobial treatment, and disease severity according to the APACHE II score are the most important risk factors for death in patients with carbapenem-resistant Klebsiella pneumoniae infection. Our finding may help predict patients' outcomes and improve management for them. REGISTRATION NUMBER: 20210417EuEGX/INPLASY2020100037.

Promoter variations associated with expression of mcr-1 gene and level of colistin resistance.

OBJECTIVES: Colistin resistance mediated by plasmids for their rapid dissemination in Enterobacteriaceae is alarming. We aimed to characterize the genetic features of mcr-1 gene as well as the role of promoters in gene expression and levels of colistin resistance among clinical isolates of Enterobacteriaceae. METHODS: Clinical isolates of Enterobacteriaceae were collected in thirteen cities in China and screened for mcr-1 gene using polymerase chain reaction (PCR) amplification and sequencing. Antimicrobial susceptibility testing, transformation assay and plasmid sequencing, quantitative real-time PCR were performed for mcr-1-positive isolates. Promoter-probe vector pKK232-8 was utilized to assess the activity of the mcr-1 promoters. RESULTS: This study identified the mcr-1 gene in 15 clinical isolates of Enterobacteriaceae, among which 14 were resistant to colistin, with MICs of 4-8 mg/L, while one mcr-1-bearing isolate EC09 was susceptible to colistin, with an MIC of 0.5 mg/L. Moreover, mcr-1-harbouring plasmids from 10 clinical isolates were transferrable via transformation and belonged to different incompatibility groups (IncI2 and IncX4). Plasmid pEC09 failed to transform and belonged to IncP1. A genetic structure containing the mcr-1-pap2 element was detected in these plasmids. EC09 demonstrated the lowest transcription level of mcr-1 gene, as determined by quantitative real-time PCR, which was in accordance with its susceptibility to colistin. Furthermore, the promoter activity of mcr-1 in pEC09 was the lowest, as determined by promoter-probe vector pKK232-8. CONCLUSION: Promoter variations were associated with expression of the mcr-1 gene and ultimately the levels of colistin resistance.

Predictors of mortality in adult patients with methicillin-resistant Staphylococcus aureus bloodstream infection: a meta-analysis and systematic review.

BACKGROUND: Cases of methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infection have been increasing. Patients with MRSA bloodstream infection have a poor prognosis and high mortality rate. Identification of potential risk factors associated with MRSA bloodstream infection-related mortality may help improve patient outcomes. METHODS: Embase, PubMed, and the Cochrane Library databases were searched to identify articles describing predictors of mortality in patients with MRSA bloodstream infections. Two investigators independently assessed articles for inclusion and data extraction. RESULTS: Twenty observational studies were included in the analysis. Factors associated with higher mortality were development of severe sepsis or septic shock [odds ratio (OR): 4.56, 95% CI: 3.37-6.18], congestive heart failure (OR: 1.78, 95% CI: 1.27-2.50), liver cirrhosis (OR: 1.90, 95% CI: 1.27-2.65), malignancy (OR: 1.62, 95% CI: 1.33-1.98), infective endocarditis (OR: 2.05, 95% CI: 1.35-3.11), nosocomial infection (OR: 2.80, 95% CI: 1.41-5.55), intensive care unit admission (OR: 3.08, 95% CI: 1.49-6.36) and inappropriate empirical antimicrobial treatment (OR: 2.25, 95% CI: 1.16-4.36); removal of the eradicable foci was a protective factor (OR: 0.51, 95% CI: 0.40-0.63) The average APACHE II score at the time of diagnosis of MRSA bloodstream infection was considerably higher in patients who did not survive than in those who survived [weighted mean difference (WMD): 5.81, 95% CI: 3.03-8.59]. DISCUSSION: Patient condition, appropriate timing of antimicrobial treatment, surgical intervention and disease severity according to the APACHE II score are the most important risk factors for death in patients with MRSA bloodstream infections.

Clinical and Genomic Analysis of Liver Abscess-Causing Klebsiella pneumoniae Identifies New Liver Abscess-Associated Virulence Genes.

Hypervirulent variants of Klebsiella pneumoniae (hvKp) that cause invasive community-acquired pyogenic liver abscess (PLA) have emerged globally. Little is known about the virulence determinants associated with hvKp, except for the virulence genes rmpA/A2 and siderophores (iroBCD/iucABCD) carried by the pK2044-like large virulence plasmid. Here, we collected most recent clinical isolates of hvKp from PLA samples in China, and performed clinical, molecular, and genomic sequencing analyses. We found that 90.9% (40/44) of the pathogens causing PLA were K. pneumoniae. Among the 40 LA-Kp, K1 (62.5%), and K2 (17.5%) were the dominant serotypes, and ST23 (47.5%) was the major sequence type. S1-PFGE analyses demonstrated that although 77.5% (31/40) of the LA-Kp isolates harbored a single large virulence plasmid varied in size, 5 (12.5%) isolates had no plasmid and 4 (10%) had two or three plasmids. Whole genome sequencing and comparative analysis of 3 LA-Kp and 3 non-LA-Kp identified 133 genes present only in LA-Kp. Further, large scale screening of the 133 genes in 45 LA-Kp and 103 non-LA-Kp genome sequences from public databases identified 30 genes that were highly associated with LA-Kp, including iroBCD, iucABCD and rmpA/A2 and 21 new genes. Then, these 21 new genes were analyzed in 40 LA-Kp and 86 non-LA-Kp clinical isolates collected in this study by PCR, showing that new genes were present 80-100% among LA-Kp isolates while 2-11% in K. pneumoniae isolates from sputum and urine. Several of the 21 genes have been proposed as virulence factors in other bacteria, such as the gene encoding SAM-dependent methyltransferase and pagO which protects bacteria from phagocytosis. Taken together, these genes are likely new virulence factors contributing to the hypervirulence phenotype of hvKp, and may deepen our understanding of virulence mechanism of hvKp.