An unusual community-acquired invasive and multi systemic infection due to ExoU-harboring Pseudomonas aeruginosa strain: Clinical disease and microbiological characteristics

High Prevalence of GES-5 Variant and Co-Expression of VIM-2 and GES-45 among Clinical Pseudomonas aeruginosa Strains in Tunisia

Carbapenem-resistant Pseudomonas aeruginosa (CRPA) are a global health concern. The antimicrobial resistance, virulence, and molecular typing of 57 CRPA isolated from 43 patients who attended a specific Tunisian hospital from September 2018 to July 2019 were analyzed. All but one were multidrug-resistant CRPA, and 77% were difficult-to-treat-resistant (DTR) isolates. The blaVIM-2 gene was detected in four strains (6.9%), and among the 36 blaGES-positive CRPA (62%), the blaGES-5 gene was the predominant variant (86%). Three strains co-harbored the blaVIM-2 and blaGES-45 genes, and seven CRPA carried the blaSHV-2a gene (14%). OprD alterations, including truncations by insertion sequences, were observed in 18 strains. Regarding the 46 class 1 integron-positive CRPA (81%), the blaGES-5 gene was located in integron In717, while the blaGES-29 and blaGES-45 genes were found in two new integrons (In2122 and In4879), and the blaVIM-2 gene was found in In1183 and the new integron In2142. Twenty-four PFGE patterns and thirteen sequence types (three new ones) were identified. The predominant serotype O:11 and exoU (81%) were mostly associated with ST235 and the new ST3385 clones. The seven blaSHV-2a-CRPA from different patients belonged to ST3385 and the same PFGE pattern. The blaGES-5- and blaVIM-2 + blaGES-45-positive CRPA recovered mostly from ICU patients belonged to the high-risk clone ST235. Our results highlight the alarming prevalence of blaGES-5- and ST235-CRPA, the co-existence of blaGES-45 and blaVIM-2, and their location within integrons favoring their dissemination.

Emergence of ST463 exoU-Positive, Imipenem-Nonsusceptible Pseudomonas aeruginosa Isolates in China

This study investigated the resistance mechanisms and the distribution and proportions of virulence genes, including exoU, in 182 imipenem-nonsusceptible Pseudomonas aeruginosa (INS-PA) strains collected from China in 2019. There was no obvious prevalent sequence type or concentrated evolutionary multilocus sequence typing (MLST) type on the INS-PA phylogenetic tree in China. All of the INS-PA isolates harbored β-lactamases with/without other antimicrobial mechanisms, such as gross disruption of oprD and overexpression of efflux genes. Compared with exoU-negative isolates, exoU-positive isolates (25.3%, 46/182) presented higher virulence in A549 cell cytotoxicity assays. The southeast region of China had the highest proportion (52.2%, 24/46) of exoU-positive strains. The most frequent exoU-positive strains belonged to sequence type 463 (ST463) (23.9%, 11/46) and presented multiple resistance mechanisms and higher virulence in the Galleria mellonella infection model. The complex resistance mechanisms in INS-PA and the emergence of ST463 exoU-positive, multidrug-resistant P. aeruginosa strains in southeast China indicated a challenge that might lead to clinical treatment failure and higher mortality. IMPORTANCE This study investigates the resistance mechanisms and distribution and proportions of virulence genes of imipenem-nonsusceptible Pseudomonas aeruginosa (INS-PA) isolates in China in 2019. Harboring PDC and OXA-50-like genes is discovered as the most prevalent resistance mechanism in INS-PA, and the virulence of exoU-positive INS-PA isolates was significantly higher than that of exoU-negative INS-PA isolates. There was an emergence of ST463 exoU-positive INS-PA isolates in Zhejiang, China, most of which presented multidrug resistance and hypervirulence.

Antiquorum and Antibiofilm Activities of Piper bogotense C. DC. against Pseudomonas aeruginosa and Identification of Bioactive Compounds

The present study describes the anti-biofilm and quorum sensing (QS) inhibitory potential of extracts and chemical constituents from Piper bogotense. Antibiofilm potential was determined through crystal violet assay against Pseudomonas aeruginosa, while QS inhibition efficacy was determined through violacein inhibition assay using Chromobacterium violaceum as a bacterial model. Additionally, this study reports the effects of the chemical constituents isolated in P. bogotense against various virulent factors associated with QS, such as the percentage decrease in pyocyanin, elastase, and protease production. The chemical study led to the isolation and identification of two prenylated benzoic acids (1 and 2) and a prenylated hydroquinone 3, of which compounds 1 and 2 are reported for the first time for P. bogotense. The ethanolic extract and the DCM fraction from P. bogotense stand out for reducing violacein production in C. violaceum, as well as the biofilm formation in P. aeruginosa. Compounds 2 and 3 stand out for having the lowest violacein production (43.8% and 68.3%), as well as the lowest production of virulence factors such as elastase (60.2% and 51.4%) and pyocyanin (39.7% and 33.2%). These results demonstrate the potential of P. bogotense components to be used as an alternative control against multidrug-resistant P. aeruginosa.

In vitro activity of cefiderocol, cefepime/enmetazobactam, cefepime/zidebactam, eravacycline, omadacycline, and other comparative agents against carbapenem-non-susceptible Pseudomonas aeruginosa and Acinetobacter baumannii isolates associated from bloodstream infection in Taiwan between 2018-2020

BACKGROUND/PURPOSE

This study aimed to investigate the in vitro susceptibilities of carbapenem-non-susceptible Pseudomonas aeruginosa (CNSPA) and Acinetobacter baumannii (CNSAB) isolates to cefiderocol, novel β-lactamase inhibitor (BLI) combinations, new tetracycline analogues, and other comparative antibiotics.

METHODS

In total, 405 non-duplicate bacteremic CNSPA (n = 150) and CNSAB (n = 255) isolates were collected from 16 hospitals in Taiwan between 2018 and 2020. Minimum inhibitory concentrations (MICs) were determined using the broth microdilution method, and susceptibilities were interpreted according to the relevant guidelines or in accordance with results of previous studies and non-species-related pharmacokinetic/pharmacodynamic data.

RESULTS

Among the isolates tested, cefiderocol demonstrated potent in vitro activity against CNSPA (MIC50/90, 0.25/1 mg/L; 100% of isolates were inhibited at ≤4 mg/L) and CNSAB (MIC50/90, 0.5/2 mg/L; 94.9% of isolates were inhibited at ≤4 mg/L) isolates. More than 80% of CNSPA isolates were susceptible to cefiderocol, ceftazidime/avibactam, ceftolozane/tazobactam, and amikacin, based on breakpoints established by the Clinical and Laboratory Standards Institute. Activities of new BLI combinations varied significantly. Tetracycline analogues, including tigecycline (MIC50/90, 1/2 mg/L; 92.5% of CNSAB isolates were inhibited at ≤2 mg/L) and eravacycline (MIC50/90, 0.5/1 mg/L; 99.6% of CNSAB isolates were inhibited at ≤2 mg/L) exhibited more potent in vitro activity against CNSAB than omadacycline (MIC50/90, 4/8 mg/L).

CONCLUSIONS

The spread of CNSPA and CNSAB poses a major challenge to global health. Significant resistance be developed even before a novel agent becomes commercially available. The development of on-site antimicrobial susceptibility tests for these novel agents is of great clinical importance.

Geographic Patterns of Carbapenem-resistant Pseudomonas aeruginosa in the Asia-Pacific Region: Results from the Antimicrobial Testing Leadership and Surveillance (ATLAS) program, 2015-2019

Pseudomonas aeruginosa is a common pathogen that is associated with multidrug-resistant (MDR) and carbapenem-resistant (CR) phenotypes; therefore, we investigated its resistance patterns and mechanisms by using data from the Antimicrobial Testing Leadership and Surveillance (ATLAS) program in the Asia-Pacific region during 2015-2019. MICs were determined using the broth microdilution method. Genes encoding major extended-spectrum β-lactamases and carbapenemases were investigated by multiplex PCR assays. Susceptibility was interpreted using the Clinical and Laboratory Standards Institute (CLSI) breakpoints. A total of 6,349 P. aeruginosa isolates were collected in the ATLAS program between 2015 and 2019 from 14 countries. According to the CLSI definitions, the numbers (and rates) of CR and MDR P. aeruginosa were 1,198 (18.9%) and 1,303 (20.5%), respectively. For 747 of the CR P. aeruginosa strains that were available for gene screening, 253 β-lactamases genes were detected in 245 (32.8%) isolates. The most common gene was bla_VIM (29.0, 71/245), followed by bla_NDM (24.9%, 61/245) and bla_VEB (20.8%, 51/245). The resistance patterns and associated genes varied significantly between the countries in the Asia-Pacific region. India had the highest rates of carbapenem resistance (29.3%, 154/525) and gene detection (17.7%, 93/525). Compared to those harboring either class A or B β-lactamase genes, the CR P. aeruginosa without detected β-lactamase genes had lower MICs for most of the antimicrobial agents, including ceftazidime/avibactam and ceftolozane/tazobactam. In conclusion, MDR and CR P. aeruginosa infections pose a major threat, particularly those with detected carbapenemase genes. Continuous surveillance is important for improving antimicrobial stewardship and antibiotic prescriptions.

Comparison of Etest and broth microdilution for evaluating the susceptibility of Staphylococcus aureus and Streptococcus pneumoniae to ceftaroline and of carbapenem-resistant Enterobacterales and Pseudomonas aeruginosa to ceftazidime/avibactam

OBJECTIVES

Decreased susceptibility to ceftazidime/avibactam (CZA) and ceftaroline (CPT) has been reported during antimicrobial resistance surveillance and therapy. Conventional laboratories are unable to provide timely susceptibility testing for CZA and CPT because these antimicrobial agents are not incorporated in automated susceptibility testing systems.

METHODS

We evaluated Etest and the Sensititre broth microdilution (BMD) method for testing CZA against carbapenem-resistant Gram-negative bacilli and CPT against important Gram-positive cocci bloodstream isolates. Genotypes of carbapenemases in Enterobacterales were also determined using the Xpert® Carba-R assay.

RESULTS

Etest showed ≥90% agreement with Sensititre BMD for carbapenem-resistant Klebsiella pneumoniae (CRKP) (n = 187), carbapenem-resistant Escherichia coli (CREC) (n = 28) and Streptococcus pneumoniae (n = 35); however, the very major error rate exceeded 3%. Agreement between Etest and Sensititre BMD was <90% for carbapenem-resistant Pseudomonas aeruginosa (CRPA) (n = 81), methicillin-susceptible Staphylococcus aureus (MSSA) (n = 92) and methicillin-resistant S. aureus (MRSA) (n = 170). Both agents remained potent with a high susceptibility rate by Sensititre BMD as follows: CZA against CRKP (95.0%), CREC (89.3%) and CRPA (84.5%); and CPT against MSSA (100.0%), MRSA (95.3%) and S. pneumoniae (94.3%). CZA was active against blaKPC-carrying CRKP (98.5% susceptible), and resistance in the majority of CZA-resistant Enterobacterales isolates (6 of 10 CRKP and 2 of 3 CREC) was due to the presence of a metallo-β-lactamase gene.

CONCLUSION

Our results suggest that interpretation of susceptibility results obtained by Etest for both agents should be undertaken cautiously and remains challenging.

Bacterial behavior in human blood reveals complement evaders with some persister-like features

Bacterial bloodstream infections (BSI) are a major health concern and can cause up to 40% mortality. Pseudomonas aeruginosa BSI is often of nosocomial origin and is associated with a particularly poor prognosis. The mechanism of bacterial persistence in blood is still largely unknown. Here, we analyzed the behavior of a cohort of clinical and laboratory Pseudomonas aeruginosa strains in human blood. In this specific environment, complement was the main defensive mechanism, acting either by direct bacterial lysis or by opsonophagocytosis, which required recognition by immune cells. We found highly variable survival rates for different strains in blood, whatever their origin, serotype, or the nature of their secreted toxins (ExoS, ExoU or ExlA) and despite their detection by immune cells. We identified and characterized a complement-tolerant subpopulation of bacterial cells that we named “evaders”. Evaders shared some features with bacterial persisters, which tolerate antibiotic treatment. Notably, in bi-phasic killing curves, the evaders represented 0.1–0.001% of the initial bacterial load and displayed transient tolerance. However, the evaders are not dormant and require active metabolism to persist in blood. We detected the evaders for five other major human pathogens: Acinetobacter baumannii, Burkholderia multivorans, enteroaggregative Escherichia coli, Klebsiella pneumoniae, and Yersinia enterocolitica. Thus, the evaders could allow the pathogen to persist within the bloodstream, and may be the cause of fatal bacteremia or dissemination, in particular in the absence of effective antibiotic treatments.

Blood infections by antibiotic resistant bacteria, notably Pseudomonas aeruginosa, are major concerns in hospital settings. The complex interplay between P. aeruginosa and the innate immune system in the context of human blood is still poorly understood. By studying the behavior of various P. aeruginosa strains in human whole blood and plasma, we showed that bacterial strains display different rate of tolerance to the complement system. Despite the complement microbicide activity, most bacteria withstand elimination through phenotypic heterogeneity creating a tiny (<0.1%) subpopulation of transiently tolerant evaders able to persist in plasma. This phenotypic heterogeneity thus prevents total elimination of the pathogen from the circulation, and represents a new strategy to disseminate within the organism.