Enhancing the activity of β-lactamase inhibitory protein-II with cell-penetrating peptide against KPC-2-carrying Klebsiella pneumoniae

Carbapenem-resistant Enterobacterales (CRE) is considered a paramount threat due to its rapid spread and high mortality rate. Klebsiella pneumoniae carbapenemases (KPCs), specifically KPC-2, are prevalent enzymes responsible for carbapenem resistance in many countries. While combinations of antibiotics are commonly used, they must be tailored to match the remaining susceptibility of the infecting strains. Therefore, there is a need to develop the β-lactamase inhibitor to effectively address this issue. β-lactamase inhibitor protein (BLIP) and its variants, BLIP-I and BLIP-II, have demonstrated the ability to inhibit class A β-lactamases. In particular, BLIP-II shows strong binding to the KPC-2 carbapenemase, making it a potential candidate for inhibition. To improve the intracellular penetration of BLIP-II, a cell-penetrating peptide (CPP) was employed. In this study, a KRK-rich peptide was introduced at either the N-terminal or C-terminal region of tBLIP-II, excluding the signal sequence of the BLIP-II protein. tBLIP-II, tBLIP-II-CPP, and CPP-BLIP-II were successfully expressed, and the chimeric proteins retained inhibitory activity compared to tBLIP-II alone. It is apparent that homology modeling demonstrated neither the poly-histidine tag nor the CPP interfered with the essential interaction residues of tBLIP-II. Interestingly, BLIP-II-CPP exhibited the highest inhibitory activity, reducing the minimal inhibitory concentration (MIC) of meropenem by 8 folds. Moreover, the combination of tBLIP-CPP with meropenem significantly decreased the viable bacterial cell count compared to the combination of tBLIP-II with meropenem or meropenem alone. These findings suggest that tBLIP-CPP is a promising candidate for restoring carbapenem susceptibility against CRE and provides a valuable therapeutic option for infections caused by CRE.

High-risk lineages of extended spectrum cephalosporinase producing Escherichia coli from Eurasian griffon vultures (Gyps fulvus) foraging in landfills in north-eastern Spain

Extended-spectrum cephalosporinase producing (ESC) E. coli are regarded as key indicator microorganisms of antimicrobial resistance (AMR), calling for a One Health integrated global surveillance strategy. Wildlife is exposed to antibiotic contaminants and/or resistant bacteria that have been released into the environment, potentially acting as reservoirs and spreaders of resistance genes as well as sentinels of anthropogenic pressure. Monitoring AMR in wildlife has become crucial in determining anthropogenic environmental impacts as well as transmission routes. In this study, we determined the occurrence and potential sources of ESC E. coli in 218 Eurasian griffon vultures (Gyps fulvus) foraging regularly on human waste disposed at a dumpsite in north-eastern Spain. Minimal inhibitory concentration for 14 different antimicrobials was performed to evaluate the phenotype of the isolates, and whole genome sequencing was carried out to investigate lineages and plasmids harbouring ESC genes. Our sequences were compared to previously published Spanish sequences of human, animal, and wildlife origin. We report a high prevalence of CTX-M-15, as well as the presence of other resistance genes such as OXA-10, CTX-M-27, and CTX-M-65 which are rarely described in European livestock, suggesting a human origin. The isolates also carried a diverse range of additional AMR genes for a broad spectrum of drug families, with the majority being multi-drug resistant. The phylogenomic analyses suggests the transmission of high-risk lineages from humans to vultures, with 49 % of our isolates matching the most common extraintestinal pathogenic E. coli (ExPEC) lineages described in humans worldwide, including ST131, ST10 and ST58. We conclude that anthropogenically altered habitats, such as landfills, are hotspots for the acquisition and spread of high-risk ESC E. coli lineages associated with hospital infections. Measures must be implemented to limit their spread into natural environments.

Evaluation of the BL-RED (Beta-Lactamase Rapid Electrochemical Detection) test for the rapid detection of resistance to third-generation cephalosporins in Enterobacteriaceae

The sensitivity of NG-test CTX-M Multi assay and BL-RED test incubated 10 min for the detection of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae was 80.6% and 90.3% respectively. Using an extended 60 min incubation with the BL-RED test, its sensitivity was increased to 100% and 60.9% for ESBL-producing and cephalosporinase-overexpressing Enterobacteriaceae respectively.

Impact of Peptidoglycan Recycling Blockade and Expression of Horizontally Acquired β-Lactamases on Pseudomonas aeruginosa Virulence

In the current scenario of antibiotic resistance magnification, new weapons against top nosocomial pathogens like Pseudomonas aeruginosa are urgently needed. The interplay between β-lactam resistance and virulence is considered a promising source of targets to be attacked by antivirulence therapies, and in this regard, we previously showed that a peptidoglycan recycling blockade dramatically attenuated the pathogenic power of P. aeruginosa strains hyperproducing the chromosomal β-lactamase AmpC. Here, we sought to ascertain whether this observation could be applicable to other β-lactamases. To do so, P. aeruginosa wild-type or peptidoglycan recycling-defective strains (ΔampG and ΔnagZ) harboring different cloned β-lactamases (transferable GES, VIM, and OXA types) were used to assess their virulence in Galleria mellonella larvae by determining 50% lethal doses (LD50s). A mild yet significant LD50 increase was observed after peptidoglycan recycling disruption per se, whereas the expression of class A and B enzymes did not impact virulence. While the production of the narrow-spectrum class D OXA-2 entailed a slight attenuation, its extended-spectrum derivatives OXA-226 (W159R [bearing a change of W to R at position 159]), OXA-161 (N148D), and principally, OXA-539 (D149 duplication) were associated with outstanding virulence impairments, especially in recycling-defective backgrounds (with some LD50s being >1,000-fold that of the wild type). Although their exact molecular bases remain to be deciphered, these results suggest that mutations affecting the catalytic center and, therefore, the hydrolytic spectrum of OXA-2-derived enzymes also drastically impact the pathogenic power of P. aeruginosa. This work provides new and relevant knowledge to the complex topic of the interplay between the production of β-lactamases and virulence that could be useful to build future therapeutic strategies against P. aeruginosa. IMPORTANCE Pseudomonas aeruginosa is one of the leading nosocomial pathogens whose growing resistance makes the development of therapeutic options extremely urgent. The resistance-virulence interplay has classically aroused researchers' interest as a source of therapeutic targets. In this regard, we describe a wide array of virulence attenuations associated with different transferable β-lactamases, among which the production of OXA-2-derived extended-spectrum β-lactamases stood out as a dramatic handicap for pathogenesis, likely as a side effect of mutations causing the expansion of their hydrolytic spectrums. Moreover, our results confirm the validity of disturbing peptidoglycan recycling as a weapon to attenuate P. aeruginosa virulence in class C and D β-lactamase production backgrounds. In the current scenario of dissemination of horizontally acquired β-lactamases, this work brings out new data on the complex interplay between the production of specific enzymes and virulence attenuation that, if complemented with the characterization of the underlying mechanisms, will likely be exploitable to develop future virulence-targeting antipseudomonal strategies.

Faecal carriage of extended-spectrum beta-lactamase-producing bacteria in the community

We determined the faecal carriage of extended-spectrum beta-lactamase-(ESBL)-producing bacteria in the community in Saudi Arabia. A total of 716 faecal specimens (from 505 healthy individuals and 211 community outpatients) were screened for ESBL using the double-disk synergy test and confirmed by the Clinical Laboratory Standards Institute combined disk method. We found 91 (12.7%) isolates were ESBL-producers. Of these, 87 (95.6%) were Escherichia coli and 4 (4.4%) Klebsiella pneumoniae. A similar rate of faecal carriage of ESBL-producers was demonstrated in community outpatients and healthy individuals: 62 (12.3%) healthy persons and 29 (13.7%) outpatients. We conclude that the community could be a reservoir of these ESBL-producing bacteria and enzymes.

[Multifactorial analysis of the phenotypes for beta-lactams of 1044 Escherichia coli strains]

1,044 E. coli strains were randomly collected by the beginning of 1992. Their susceptibility for seven beta-lactam antibiotics: amoxycillin, augmentin, ticarcillin, claventin, cephalothin, cefoxitin and cefotaxime, was studied routinely by the agar diffusion method. The datas were analyzed by the CERIB multifactorial analysis package which yields to homogeneous populations. This analysis showed four well defined populations: 1) 588 strains (56.4%) susceptible to all antibiotics; 2) 410 strains (39.3%) present a penicillinase phenotype; 3) 11 strains (1.05%) are cephalosporinase producer; 4) 7 strains (0.67%) were identified as producing an extended-spectrum beta-lactamase. The remaining strains: 28 (2.68%) had a reduced susceptibility to all antibiotics, which suggests the combination of few resistance mechanisms or other hypothesis.

An X-ray-crystallographic study of beta-lactamase II from Bacillus cereus at 0.35 nm resolution

Crystals of beta-lactamase II (EC 3.5.2.6., 'penicillinase') from Bacillus cereus were grown with Cd(II) in place of the natural Zn(II) cofactor and stabilized by cross-linking with glutaraldehyde. Their space group is C2, the cell dimensions are a = 5.44 nm, b = 6.38 nm, c = 7.09 nm and beta = 93.6 degrees, and there is one molecule in the asymmetric unit. Diffraction data were collected from cross-linked crystals of the Cd(II)-enzyme, the apoenzyme and six heavy-atom derivatives. The electron-density map calculated at 0.35 nm resolution reveals the essential Cd(II) ion surrounded by three histidine residues and one cysteine residue. The position of a glutamic acid residue, modification of which destroys activity [Little, Emanuel, Gagnon & Waley (1986) Biochem. J. 233, 465-469], suggests the probable location of the active site of the enzyme. Two minor Cd(II) sites not essential for activity were also located. The structure of the apoenzyme at this resolution appears to differ from that of the Cd(II)-enzyme only in the orientation of two of the histidine residues and the cysteine residue that surround the metal ion.

[Problems in the determination of isoelectric points of beta lactamases]

Analytical isoelectric focusing in polyacrylamide gels and preparative electrofocusing in density gradients may give very different pI determination for the same beta lactamase. This difference seems due to a lack of enzyme migration in some parts of the cross-linked polyacrylamide gel. This migration appears easier in density gradient isoelectricfocusing, and thus this technique yields more significant absolute pI values. Analytical isoelectric focusing should only be used for comparison studies.

Iodmetric and spectrophotometric assays for cephradine after its hydrolysis with a beta-lactamase

Iodmetric and spectrophotometric methods were developed for the analysis of the new antibiotic cephradine. The procedures are modifications of known methods but are novel in employing a specific beta-lactamase for hydrolysis of the beta-lactam ring of the cephalosporin molecule. The iodometric method is rapid, precise, and accurate, but it requires fairly large amounts of cephradine. The spectrophotometric method, using differential UV absorption at 260 nm, is more rapid and more sensitive than the iodometric method but somewhat less accurate. Both methods proved useful for the routine assay of cephradine in certain formulations.