Semirapid Detection of Piperacillin/Tazobactam Resistance and Extended-Spectrum Resistance to β-Lactams/β-Lactamase Inhibitors in Clinical Isolates of Escherichia coli

Piperacillin/Tazobactam Co-Delivery by Micellar Ionic Conjugate Systems Carrying Pharmaceutical Anions and Encapsulated Drug

Previously obtained amphiphilic graft copolymers based on [2-(methacryloyloxy)ethyl]trimethylammonium chloride (TMAMA) ionic liquid were used as the matrices of three types of nanocarriers, i.e., conjugates with ionic piperacillin (PIP) and micelles with tazobactam (TAZ), which represented single systems, and dual systems bearing PIP anions and encapsulated TAZ for co-delivery. The exchange of Cl anions in TMAMA units with PIP ones resulted in a yield of 45.6-72.7 mol.%. The self-assembling properties were confirmed by the critical micelle concentration (CMC), which, after ion exchange, increased significantly (from 0.011-0.020 mg/mL to 0.041-0.073 mg/mL). The amphiphilic properties were beneficial for TAZ encapsulation to reach drug loading contents (DLCs) in the ranges of 37.2-69.5 mol.% and 50.4-80.4 mol.% and to form particles with sizes of 97-319 nm and 24-192 nm in the single and dual systems, respectively. In vitro studies indicated that the ionically conjugated drug (PIP) was released in quantities of 66-81% (7.8-15.0 μg/mL) from single-drug systems and 21-25% (2.6-3.9 μg/mL) from dual-drug systems. The release of encapsulated TAZ was more efficient, achieving 47-98% (7.5-9.0 μg/mL) release from the single systems and 47-69% (9.6-10.4 μg/mL) release from the dual ones. Basic cytotoxicity studies showed non-toxicity of the polymer matrices, while the introduction of the selected drugs induced cytotoxicity against normal human bronchial epithelial cells (BEAS-2B) with the increase in concentration.

Genetic determinants underlying the progressive phenotype of β-lactam/β-lactamase inhibitor resistance in Escherichia coli

IMPORTANCE

The increased feasibility of whole-genome sequencing has generated significant interest in using such molecular diagnostic approaches to characterize difficult-to-treat, antimicrobial-resistant (AMR) infections. Nevertheless, there are current limitations in the accurate prediction of AMR phenotypes based on existing AMR gene database approaches, which primarily correlate a phenotype with the presence/absence of a single AMR gene. Our study utilized a large cohort of cephalosporin-susceptible Escherichia coli bacteremia samples to determine how increasing the dosage of narrow-spectrum β-lactamase-encoding genes in conjunction with other diverse β-lactam/β-lactamase inhibitor (BL/BLI) genetic determinants contributes to progressively more severe BL/BLI phenotypes. We were able to characterize the complexity of the genetic mechanisms underlying progressive BL/BLI resistance including the critical role of β-lactamase encoding gene amplification. For the diverse array of AMR phenotypes with complex mechanisms involving multiple genomic factors, our study provides an example of how composite risk scores may improve understanding of AMR genotype/phenotype correlations.

Role of blaTEM and OmpC in the piperacillin-tazobactam resistance evolution by E. coli in patients with complicated intra-abdominal infection

Piperacillin-tazobactam resistance (P/T-R) is increasingly reported among Escherichia coli isolates. Although in vitro experiments have suggested that blaTEM gene plays a key role in the P/T-R acquisition, no clinical in vivo study has yet confirmed the role of blaTEM or other genes. Therefore, we aimed to identify the mechanisms underlying P/T-R by following up patients with E. coli complicated intra-abdominal infections (cIAI) who experienced P/T treatment failure. Four pairs of strains, clonally related from four patients, were isolated both before and after treatment with P/T dosed at 4 g/0.5 g intravenously. The P/T MIC was tested using broth microdilution, and β-lactamase activity was determined in these isolates. Whole-genome sequencing (WGS) was performed to decipher the role of blaTEM and other genes associated with P/T-R. Changes in the outer membrane protein (OMP) profile were analyzed using SDS-PAGE, and blaTEM and ompC transcription levels were measured by RT-qPCR. In addition, in vitro competition fitness was performed between each pairs of strains (P/T-susceptible vs. P/T-resistant). We found a higher copy number of blaTEM gene in P/T-R isolates, generated by three different genetic events: (1) IS26-mediated duplication of the blaTEM gene, (2) generation of a small multicopy plasmid (ColE-like) carrying blaTEM, and (3) adaptive evolution via reduction of plasmid size, leading to a higher plasmid copy number. Moreover, two P/T-R strains showed reduced expression of OmpC. This study describes the mechanisms involved in the acquisition of P/T-R by E. coli in patients with cIAI. The understanding of P/T-R evolution is crucial for effectively treating infected patients and preventing the spread of resistant microorganisms.

Rapid Detection of Piperacillin-Tazobactam Resistance in Klebsiella pneumoniae and Escherichia coli

Rapid determination of susceptibility to piperacillin-tazobactam (TZP) is very important since the development of antibiotic resistance and inadequate treatment could increase the risk of clinical failure in infected patients, especially if such resistance is unknown to the clinician. Therefore, based on color change from orange to yellow of phenol red due to glucose metabolism (bacterial growth) in the presence of an adequate concentration of TZP (10 mg/L piperacillin and 5 mg/L tazobactam), the RapidTZP test has been developed to detect TZP resistance in Escherichia coli and Klebsiella pneumoniae isolates in a maximum of 3 h. A total of 140 isolates, 43 of E. coli and 97 of K. pneumoniae, were used to evaluate the performance of the test, 60 being resistant to TZP. The sensitivity and specificity of the test were 98.24% and 100%, respectively. Additionally, the RapidTZP test was validated by a pellet obtained directly from blood culture bottles. A total of 37 positive blood cultures for E. coli and 43 for K. pneumoniae were used for validation, 8 of them resistant to TZP. The sensitivity and specificity shown in the evaluation were 100% for both parameters. This new test is easy, fast, and accurate, providing results in 3 h. IMPORTANCE TZP is an antibiotic widely used for the empirical treatment of severe infections such as bloodstream infections. However, resistance to TZP in K. pneumoniae and E. coli has been increasing in the last few years. Thus, rapid detection of TZP resistance is critical to optimize the empirical treatment of patients with severe infections. In this study, we developed and evaluated a rapid test (RapidTZP) for the detection of TZP resistance in K. pneumoniae and E. coli directly from positive hemocultures in just 3 h. This rapid test has been validated on 138 K. pneumoniae and E. coli clinical isolates directly from agar plates and 80 K. pneumoniae and E. coli isolates causing bloodstream infections. The results demonstrate that the RapidTZP test has great clinical potential to optimize the empirical treatment of patients with bloodstream infections.

Ultrasensitive and rapid identification of ESRI developer- and piperacillin/tazobactam-resistant Escherichia coli by the MALDIpiptaz test

Background

The excessive use of piperacillin/tazobactam (P/T) has promoted the emergence of P/T-resistant Enterobacterales. We reported that in Escherichia coli, P/T contributes to the development of extended-spectrum resistance to β-lactam/β-lactamase inhibitor (BL/BLI) (ESRI) in isolates that are P/T susceptible but have low-level resistance to BL/BLI. Currently, the detection of P/T resistance relying on conventional methods is time-consuming. To overcome this issue, we developed a cost-effective test based on MALDI-MS technology, called MALDIpiptaz, which aims to detect P/T resistance and ESRI developers in E. coli.

Methods

We used automated Clover MS Data Analysis software to analyse the protein profile spectra obtained by MALDI-MS from a collection of 248 E. coli isolates (91 P/T-resistant, 81 ESRI developers and 76 P/T-susceptible). This software allowed to preprocess all the spectra to build different peak matrices that were analysed by machine learning algorithms.

Results

We demonstrated that MALDIpiptaz can efficiently and rapidly (15 min) discriminate between P/T-resistant, ESRI developer and P/T-susceptible isolates and allowed the correct classification between ESRI developers from their isogenic resistance to P/T.

Conclusion

The combination of excellent performance and cost-effectiveness are all desirable attributes, allowing the MALDIpiptaz test to be a useful tool for the rapid determination of P/T resistance in clinically relevant E. coli isolates.