Carbapenems Research Articles

Novel 1,2,3-Triazole-sulphadiazine-ZnO Hybrids as Potent Antimicrobial Agents against Carbapenem Resistant Bacteria.

Bacterial pneumonia is considered one of the most virulent diseases with high morbidity and mortality rates, especially in hospitalized patients. Moreover, bacterial resistance increased over the last decades which limited the therapy options to carbapenem antibiotics. Hence, the metallo-β-lactamase-producing bacteria were deliberated as the most deadly and ferocious infectious agents. Sulphadiazine-ZnO hybrids biological activity was explored in vitro and in vivo against metallo-β-lactamases (MBLs) producing Klebsiella pneumoniae. Docking studies against NDM-1 and IMP-1 MBLs revealed the superior activity of the 3a compound in inhibiting both MBLs enzymes in a valid reliable docking approach. The MBLs inhibition enzyme assay revealed the remarkable sulphadiazine-ZnO hybrids inhibitory effect against NDM-1 and IMP-1 MBLs. The tested compounds inhibited the enzymes both competitively and noncompetitively. Compound 3b-ZnO showed the highest antibacterial activity against the tested metallo-β-lactamase producers with an inhibition zone (IZ) diameter reaching 43 mm and a minimum inhibitory concentration (MIC) reaching 2 µg/mL. Sulphadiazine-ZnO hybrids were tested for their in vitro cytotoxicity in a normal lung cell line (BEAS-2Bs cell line). Higher cell viability was observed with 3b-ZnO. Biodistribution of the sulphadiazine-ZnO hybrids in the lungs of uninfected rats revealed that both [124I]3a-ZnO and [124I]3b-ZnO hybrids remained detectable within the rats’ lungs after 24 h of endotracheal aerosolization. Moreover, the residence duration in the lungs of [124I]3b-ZnO (t1/2 4.91 h) was 85.3%. The histopathological investigations confirmed that compound 3b-ZnO has significant activity in controlling bacterial pneumonia infection in rats.

Clinical, Laboratory and Bacterial Profile of Spontaneous Bacterial Peritonitis in Vietnamese Patients with Liver Cirrhosis.

AimTo determine several clinical and laboratory features as well as the bacterial profile of spontaneous bacterial peritonitis (SBP) in 58 Vietnamese patients admitted to a single center due to liver cirrhosis.MethodsWe retrospectively analyzed bacteriological, clinical and laboratory characteristics of patients with SBP admitted to the Gastroenterology and Hepatology Center from July 2019 to July 2020.ResultsOut of a total 58 SBP patients, 41 (70.9%) had culture-negative neutrocytic ascites. The majority of patients experienced abdominal pain (93,1%) and large ascites (65,5%). Gram-negative bacteria formed the main pathogens (14/17). Escherichia coli (9/17) was the predominant cause followed by Burkholderia cepacia (2/17). Antibiotic sensitivity rate of E. coli for third generation cephalosporin was low but high for aminoglycoside and carbapenem antibiotics. The resistance of E. coli was significant against fluoroquinolones (100%). All 3 cases of gram-positive bacteria were sensitive to vancomycin.ConclusionOur study reported the bacteriological and clinical characteristics of patients with SBP and compared these findings between two groups: positive ascitic fluid culture and negative fluid culture. Ascitic fluid culture can guide for the right antibiotic choice since resistance to commonly prescribed antibiotics is common in SBP patients.

Graph-learning guided mechanistic insights into imipenem hydrolysis in GES carbapenemases

Pathogen resistance to carbapenem antibiotics compromises effective treatments of superbug infections. One major source of carbapenem resistance is the bacterial production of carbapenemases which effectively hydrolyze carbapenem drugs. In this computational study, the deacylation reaction of imipenem (IPM) by GES-5 carbapenemases (GES) is modeled to unravel the mechanistic factors that facilitate carbapenem resistance. Hybrid quantum mechanical/molecular mechanical (QM/MM) calculations are applied to sample the GES/IPM deacylation barriers on the minimum energy pathways (MEPs). In light of the recent emergence of graph-based deep-learning techniques, we construct graph representations of the GES/IPM active site. An edge-conditioned graph convolutional neural network (ECGCNN) is trained on the acyl-enzyme conformational graphs to learn the underlying correlations between the GES/IPM conformations and the deacylation barriers. A perturbative approach is proposed to interpret the latent representations from the graph-learning (GL) model and extract essential mechanistic understanding with atomistic detail. In general, our study combining QM/MM MEPs calculations and GL models explains mechanistic landscapes underlying the IPM resistance driven by GES carbapenemases. We also demonstrate that GL methods could effectively assist the post-analysis of QM/MM calculations whose data span high dimensionality and large sample-size.

Evaluation the reactivity of a peptide-based monoclonal antibody derived from OmpA with drug resistant pulsotypes of Acinetobacter baumannii as a potential therapeutic approach

BackgroundAcinetobacter baumannii is an opportunistic and antibiotic-resistant pathogen that predominantly causes nosocomial infections. There is urgent need for development nonantibiotic-based treatment strategies. We developed a novel monoclonal antibody (mAb) against a peptide of conserved outer membrane protein A (OmpA) and evaluated its reactivity with different pulsotypes of A. baumannii.MethodsPeptide derived from A. baumannii OmpA was conjugated to keyhole limpet hemocyanin and injected into BALB/c mice. Splenocytes of immunized mice were fused with SP2/0 myeloma cells followed by selection of antibody-producing hybridoma cells. After screening of different hybridoma colonies by ELISA, one monoclone was selected as 3F10-C9 and the antibody was tested for reaction with five different Acinetobacter pulsotypes that were resistant to carbapenem antibiotics. The affinity constant was measured by ELISA. The ELISA, western blotting, indirect immunofluorescence (IFA), and in vitro opsonophagocytosis assays were used to evaluate the reactivity of generated mAb.ResultsThe anti-OmpA antibody reacted with the immunizing peptide and had a high affinity (1.94 × 10−9 M) for its antigen in the ELISA. Specific binding of mAb to OmpA was confirmed in Western blot. IFA assays revealed that mAb recognized specific OmpA on the pulsotypes. Opsonophagocytosis assays showed that the mAb increased the bactericidal activity of macrophage cells. The antibody function was higher in the presence of serum complement.ConclusionsThe peptide-based mAb demonstrated optimal performance in laboratory experiments which may be appropriate in investigation on OmpA in Acinetobacter pathogenesis and development of passive immunization as a novel therapeutic approach.

Colonization of White-Tailed Deer (Odocoileus virginianus) from Urban and Suburban Environments with Cephalosporinase- and Carbapenemase-Producing Enterobacterales.

Wildlife play a role in the acquisition, maintenance, and dissemination of antimicrobial resistance (AMR). This is especially true at the human-domestic animal-wildlife interface, like urbanized areas, where interactions occur that can promote the cross-over of AMR bacteria and genes. We conducted a 2-year fecal surveillance (n = 783) of a white-tailed deer (WTD) herd from an urban park system in Ohio to identify and characterize cephalosporin-resistant and carbapenemase-producing bacteria using selective enrichment. Using generalized linear mixed models we found that older (OR = 2.3, P < 0.001), male (OR = 1.8, P = 0.001) deer from urbanized habitats (OR = 1.4, P = 0.001) were more likely to harbor extended-spectrum cephalosporin-resistant Enterobacterales. In addition, we isolated two carbapenemase-producing Enterobacterales (CPE), a Klebsiella quasipneumoniae harboring blaKPC-2 and an Escherichia coli harboring blaNDM-5, from two deer from urban habitats. The genetic landscape of the plasmid carrying blaKPC-2 was unique, not clustering with other reported plasmids encoding KPC-2, and only sharing 78% of its sequence with its nearest match. While the plasmid carrying blaNDM-5 shared sequence similarity with other reported plasmids encoding NDM-5, the intact IS26 mobile genetic elements surrounding multiple drug resistant regions, including the blaNDM-5, has been reported infrequently. Both carbapenemase genes were successfully conjugated to a J53 recipient conferring a carbapenem-resistant phenotype. Our findings highlight that urban environments play a significant role on the transmission of AMR bacteria and genes to wildlife and suggest WTD may play a role in the dissemination of clinically and epidemiologically relevant antimicrobial resistant bacteria. IMPORTANCE The role of wildlife in the spread of antimicrobial resistance is not fully characterized. Some wildlife, including white-tailed deer (WTD), can thrive in suburban and urban environments. This may result in the exchange of antimicrobial resistant bacteria and resistance genes between humans and wildlife, and lead to their spread in the environment. We found that WTD living in an urban park system carried antimicrobial resistant bacteria that were important to human health and resistant to antibiotics used to treat serious bacterial infections. This included two deer that carried bacteria resistant to carbapenem antibiotics which are critically important for treatment of life-threatening infections. These two bacteria had the ability to transfer their AMR resistance genes to other bacteria, making them a threat to public health. Our results suggest that WTD may contribute to the spread of antimicrobial resistant bacteria in the environment.

Assessment of well water as a reservoir for extended-spectrum β-lactamases (ESBL) and carbapenem resistant Enterobacteriaceae from Iwo, Osun state, Nigeria.

Unsafe water supplies are of public health concern, especially in developing countries. This article aims to investigate the microbiological quality of water from eight Wells in Iwo and to explore for the extended-spectrum β-lactamase (ESBL) and carbapenemase genes contained in isolated enteric bacteria from in the water samples. Bacterial isolation and identification were done using standard conventional methods. Antibiotic susceptibility testing was conducted using the Kirby-Bauer method. Ten phenotypically carbapenem-resistant isolates were further subjected to genotypic analysis (PCR amplification) for the detection of ESBL and carbapenemase gene. A total of 148 Enterobacteriaceae isolates belonging to seven (7) genera were isolated and identified which included E. coli, Enterobacter spp., Klebsiella spp., Salmonella, Citrobacter sp, Proteus, and Shigella. Results showed that 55% of isolates were resistant to tetracycline, 28% to cefepime, the least resistance was shown in moxifloxacin and gentamicin which had 6% and 9%, respectively, of the total isolates. For the two carbapenems used, results showed meropenem and imipenem had resistant values of 14% each, respectively. Two isolates carried the bla CTX-M gene while the carbapenemase gene (bla KPC, bla NDM, and bla OXA) was not detected in all the ten isolates. There was also negative chromosomal detection of carbapenemase in MDR isolates from well waters in Iwo town. Consequently, resistance to carbapenem antibiotics in these isolates may not be mediated by carbapenemase but by the production of extended-spectrum β-lactamases and through other mechanisms of resistance.

Conformational flexibility in carbapenem hydrolysis drives substrate specificity of the class D carbapenemase OXA-24/40

The evolution of multidrug resistance in Acinetobacter spp. increases the risk of our best antibiotics losing their efficacy. From a clinical perspective, the carbapenem-hydrolyzing class D β-lactamase subfamily present in Acinetobacter spp. is particularly concerning because of its ability to confer resistance to carbapenems. The kinetic profiles of class D β-lactamases exhibit variability in carbapenem hydrolysis, suggesting functional differences. To better understand the structure–function relationship between the carbapenem-hydrolyzing class D β-lactamase OXA-24/40 found in Acinetobacter baumannii and carbapenem substrates, we analyzed steady-state kinetics with the carbapenem antibiotics meropenem and ertapenem and determined the structures of complexes of OXA-24/40 bound to imipenem, meropenem, doripenem, and ertapenem, as well as the expanded-spectrum cephalosporin cefotaxime, using X-ray crystallography. We show that OXA-24/40 exhibits a preference for ertapenem compared with meropenem, imipenem, and doripenem, with an increase in catalytic efficiency of up to fourfold. We suggest that superposition of the nine OXA-24/40 complexes will better inform future inhibitor design efforts by providing insight into the complicated and varying ways in which carbapenems are selected and bound by class D β-lactamases.

Carbapenemase-producing Aeromonas species isolated from the urban-impacted Akaki river in Ethiopia.

Carbapenemase-producing Aeromonas species are an emerging health threat. This study aimed to determine carbapenemase-mediated resistance among Aeromonas isolates from the Akaki river, Ethiopia during the dry and wet seasons in 2019-2020. Antimicrobial susceptibility to carbapenems and cephalosporins was determined and carbapenemase production was confirmed. Of 163 isolates, the majority were human pathogens Aeromonas caviae (62), Aeromonas hydrophila (33) and Aeromonas veronii (49). These isolates were resistant to carbapenem and cephalosporin antibiotics, with the highest resistance to cefotaxime 86 (59.7%), ertapenem 71 (49.3%) and imipenem 65 (45.1%). Resistance to carbapenem antibiotics varied between species, where most A. veronii 37 (75.5%) and A. hydrophila 28 (84.8%) were resistant to imipenem and all A. caviae were sensitive. A. veronii, A. caviae and A. hydrophila resistance to meropenem was 31 (63.3%), 3 (4.8%) and 19 (57.6%), respectively. Of isolates resistant to carbapenem, 82.1% A. hydrophila and 94.4% A. veronii were carbapenemase producers. Cephalosporin resistance also varied among the different species. The highest resistance to carbapenem antibiotics was in isolates collected during the wet season (p<0.05); however, it was not consistent across all classes of antibiotics tested. The rivers in megacities could be reservoirs of carbapenemase-producing Aeromonas spp.

Utility of Drain Fluid Culture and Gram Stain in Early Intervention for Occult Anastomotic Leakage in Colorectal Cancer.

Although occult leakage after colorectal surgery does not usually cause critical illness, it can cause long-term complications that decrease the quality of life of patients. There is currently no established diagnostic, treatment, or follow-up method for occult leakage. We assessed the risk factors of occult leakage and examined the efficacy of drain fluid culture and Gram staining for its early detection and appropriate treatment intervention. Data from 243 consecutive colorectal cancer patients who underwent resection with reconstruction by the double stapling technique between 2016 and 2020 were reviewed. Sixteen (6.6%) patients had postoperative occult leakage. Multivariate analysis revealed that preoperative treatment was significantly associated with occult leakage (odds ratio=12.423; 95% confidence interval=4.095 to 17.680; p<0.001). Among the 16 patients, 1 experienced stenosis, and none experienced a fistula or chronic sinus. Drain fluid samples of 34 patients (14.0%) were Gram stainpositive, and those of 76 patients (31.3%) were culturepositive. The positive and negative predictive values of drain fluid culture were 18.4% and 98.7%, respectively, and those of Gram staining were 38.2% and 98.6%, respectively, for occult leakage. Among cases with occult leakage, more than two bacterial species were detected in 71.5% of the cultures. Antibiograms indicated that the three major species tended to be resistant to cephem antibiotics, which are used for prophylaxis, but susceptible to carbapenem antibiotics, which are used for empiric therapy. Drain fluid culture and Gram staining may enable early detection and appropriate treatment intervention for occult leakage.

Ertapenem Concentrations in Obese Patients Undergoing Surgery.

Background: Antimicrobial prophylaxis is a cornerstone to preventing surgical site infections (SSIs). Ertapenem, a carbapenem antibiotic, is commonly used for surgical prophylaxis for many different procedures, including patients undergoing colorectal and other gastrointestinal surgeries. Obesity complicates surgical intervention and increases the risk for SSIs. This study aims to describe the pharmacokinetics of ertapenem for surgical prophylaxis using a population pharmacokinetic model. Patients and Methods: Ten patients were recruited and given a single dose of ertapenem 1 g intravenous over 30 minutes. Plasma samples were obtained at multiple time points over 24 hours and assayed via validated high-performance liquid chromatography (HPLC). Pharmacokinetic analyses were conducted using a population pharmacokinetic analysis to generate pharmacokinetic parameters used in the subsequent 5,000 patient Monte Carlo simulation. The probability of target attainment (PTA) for free drug concentrations remaining above the minimum inhibitory concentration (MIC) for ≥40% was used. Results: The mean maximum plasma concentration and area under the concentration time curve (AUC0-∞) was 40.7 ± 16.5 and 148.8 ± 28.0, respectively, with a half-life of the terminal portion to be 4.3 ± 0.8 hours. Monte Carlo simulations observed PTAs above 90% for MICs ≤0.25 and ≤0.125 mcg/mL in surgeries up to three and four hours, respectively. Sufficiently high PTAs were not attainable for MICs of ≥0.5 mcg/mL. Conclusions: Ertapenem given as 1 g single dose may be an appropriate candidate for surgical prophylaxis in obese patients undergoing surgeries of four hours or less.

Regulatory mutants of Serratia with modulated antibiotic production due to intergenic transposon insertions

Antibiotic resistance is an increasing problem, exacerbated by global dissemination of drug resistance genes under selection pressure. Moreover, the rate of new antibiotic discovery declined over previous decades and so there is a growing need for new antibiotic discovery and a deeper appreciation of the various genetic and physiological factors that influence antibiotic biosynthesis. The enterobacterium Serratia sp. ATCC 39006 (Serratia) is a useful model for studies on the biosynthesis and regulation of bioactive secondary metabolites, including two antibiotics - a carbapenem and prodigiosin. Both compounds are tightly regulated in response to various physiological and environmental signals, including quorum sensing. We have identified novel regulators of antibiotic production after random transposon mutagenesis. Multiple regulatory mutations mapped to a small locus defining an intergenic region (IGR). These IGR insertion mutants display elevated production of both the carbapenem and prodigiosin antibiotics and they also exhibit reduced motility, confirming pleiotropic impacts. Exploiting phage transduction, we constructed double mutants with 15 known Serratia regulators and showed that the IGR mutant phenotype was epistatic over several of these. Further analysis suggested the presence of a putative gene encoded within the IGR locus, which may play an impactful role in the intricate regulatory network. Functional characterisation of the IGR region and its physiological impacts in both the modulation of antibiotic production and in wider pleiotropy were dissected. Mechanistic understanding of the regulatory mechanisms involved may prove exploitable in enhancing controlled antibiotic hyperproduction.

Virulence-associated genes analysis of carbapenemase-producing Escherichia coli isolates.

Carbapenem-resistant Escherichia coli has emerged as a major public health issue across the world. This study was aimed to determine the virulence content and phylogenetic groups of carbapenemase-producing E. coli isolates in southwest Iran. One hundred and fifty-two non-duplicate E. coli isolates were collected from various clinical samples. Antibiotic susceptibility and minimum inhibitory concentrations (MIC) were determined according to the Clinical and Laboratory Standards Institute (CLSI) guidelines by Kirby-Bauer disc diffusion and agar dilution methods. Phenotypic screening of carbapenemase enzymes was performed by modified Hodge test (MHT). Detection of carbapenemase genes, phylogenetic groups, and virulence-associated genes were also performed by the PCR assay. The highest and lowest resistance rates were observed against mezlocillin (70.4%) and doripenem (13.1%), respectively. Out of 28 isolates that were resistant to carbapenem antibiotics, 12 (7.9%) strains were phenotypically carbapenemase producers. The blaOXA-48 was the predominant carbapenemase gene, detected in 58.3% of isolates, followed by blaIMP (41.7%) and blaNDM (8.3%). None of the isolates harbored blaVIM and blaKPC genes. Among the twelve carbapenemase-producing strains, urinary isolates were mostly classified into B2 (41.7%) and D (25%) phylogenetic groups, while other clinical isolates belonged to B1 (25%) and A (8.3%) groups. The frequency of virulence-associated genes was also investigated in all isolates and ranged from 6.6% for hly to 75% for fimA. The emergence of carbapenemase-producing strains is a growing concern to public health. Therefore, the proper implementation of monitoring programs is crucial for limiting their dissemination.

Evaluation of Tebipenem Hydrolysis by β-Lactamases Prevalent in Complicated Urinary Tract Infections.

Tebipenem pivoxil is the first orally available carbapenem antibiotic and has been approved in Japan for treating ear, nose, and throat and respiratory infections in pediatric patients. Its active moiety, tebipenem, has shown potent antimicrobial activity in vitro against clinical isolates of Enterobacterales species from patients with urinary tract infections (UTIs), including those producing extended-spectrum β-lactamases (ESBLs) and/or AmpC β-lactamase. In the present study, tebipenem was tested for stability to hydrolysis by a set of clinically relevant β-lactamases, including TEM-1, AmpC, CTX-M, OXA-48, KPC, and NDM-1 enzymes. In addition, hydrolysis rates of other carbapenems, including imipenem, meropenem, and ertapenem, were determined for comparison. It was found that, similar to other carbapenems, tebipenem was resistant to hydrolysis by TEM-1, CTX-M, and AmpC β-lactamases but was susceptible to hydrolysis by KPC, OXA-48, and NDM-1 enzymes with catalytic efficiency values (kcat/Km) ranging from 0.1 to 2 × 106 M-1s-1. This supports the reported results of antimicrobial activity of tebipenem against ESBL- and AmpC-producing but not carbapenemase-producing Enterobacterales isolates. Considering that CTX-M and AmpC β-lactamases represent the primary determinants of multidrug-resistant complicated UTIs (cUTIs), the stability of tebipenem to hydrolysis by these enzymes supports the utility of its prodrug tebipenem, tebipenem pivoxil hydrobromide (TBP-PI-HBr), as an oral therapy for adult cUTIs.

Tebipenem pivoxil hydrobromide. Penicillin-binding protein (PBP) (bacterial) inhibitor, Carbapenem antibiotic, Treatment of urinary tract infections

Tebipenem pivoxil hydrobromide. Penicillin-binding protein (PBP) (bacterial) inhibitor, Carbapenem antibiotic, Treatment of urinary tract infections

The predominance of Klebsiella pneumoniae carbapenemase (KPC-type) gene among high-level carbapenem-resistant Klebsiella pneumoniae isolates in Baghdad, Iraq.

The serine carbapenemase enzymes (KPC) which produce from bacteria klebsiella pneumoniae today have been emerged as one of the β-lactamase enzymes that is capable to inactivating the last line of carbapenems. The gene encoding the K. pneumonia (blaKPC) belongs to gene carried on plasmid among Enterobacteriaceae family, which has modulation for the infections control so this study is aimed to spot the presence and evaluate blaKPC gene expression by real-time PCR in local isolates of K. pneumonia. Forty-seven of K. pneumonia isolates were isolated from different clinical samples (blood, sputum, urine, wounds and burns) from patients in separate hospitals in Baghdad., Antimicrobial sensitivity test was carried out by vitik-2 system and Kirby- Bauer method. The PCR was employed to detect carbapenemase gene. The results of this study showed that all explored isolates were resistant to Ertapenem, Meropenem and imipenem 47(100%). Phenotypically, all the isolates had carbapenemase which hydrolyzed the carbapenem antibiotics. Furthermore, the isolates showed (100%) resistance to Cefazolin, Ampicillin and Amoxicillin/ Clavulic acid. However, the most effective antibiotic was Levofloxacin (91.5%). The results of conventional PCR technique for the detection of blaKPC gene showed that 38 (80.9%) isolates of carbapenem-resistant K. pneumoniae harboured blaKPC gene (1010bp), while none carried other carbapenemase genes including blaNDM1, blaVIM and blaIMP genes. High levels of carbapenem resistance was clarified by the imipenem and meropenem MICs determination. All 38 isolates were positive in CNPT. Furthermore, the 38 isolates showed over expression of blaKPC gene compared with housekeeping rpo gene in Real-Time PCR. According to these results, the resistant isolates to carbapenem were belong to the present and high level expression of blaKPC gene in our local isolates.

Antimicrobial Susceptibility and Molecular Characterization of Clinical Strains of Acinetobacter sp. in the Qassim Area, Saudi Arabia

Acinetobacter sp bacteria especially Acinetobacter baumannii has emerged as a problematic multidrug-resistant (MDR) pathogen worldwide. Acinetobacter baumannii are important healthcare-associated pathogens, widely distributed in soil, water, and commonly found in the hospital environment as opportunistic pathogens from a neonatal intensive care unit and an intensive care unit (NICUs and ICUs) these bacteria formed as major nosocomial infections in hospitals environment all over the world and in the Middle East. The aim of this study was to characterize clinical isolates of A. baumannii from Qasim Area, Saudi Arabia that has an in this study, 217 nonrepetitive clinical isolates of A. baumannii were identified through MALDI-TOF and susceptibility was determined with VITEK-2 systems . Genotypic characterization of the isolates was performed by using index1,2 primers typing and polymerase chain reaction screening was performed for carbapenemase genes, insertion sequences, metallo-β-lactamases, and cephalosporinase genes. The isolates were recovered from heterogeneous clinical specimens, and the majority of the cases of A. baumannii infection were acquired in the hospital and predominantly involved patients who were older than 50 years. Total, 57.7% of the isolates were MDR, and 56.8% isolates were resistant to carbapenem antibiotics. Approximately half of the isolates were resistant to cefepime, and ceftazidime among the β-lactam antibiotics and ciprofloxacin from the quinolone group. The blaOXA-23-like gene and ISAba1 upstream of blaOXA-23-like were detected in 93% of the carbapenem-resistant isolates, while all carbapenem-resistant isolates were found to carry blaOXA-51-like, and blaADC-type cephalosporinase gene. Data demonstrate the coexistence of multiple carbapenem resistance determinants in A. baumannii from the Qssim region of Saudi Arabia.

What Doesn't Kill Them Makes Them Stronger: The Impact of the Resistance Patterns of Urinary Enterobacterales Isolates in Patients from a Tertiary Hospital in Eastern Europe.

(1) Background: The evolution of bacterial resistance to antibiotics is one of the factors that make infectious pathology an extremely dynamic field, also inducing a significant burden on public health systems; therefore, continuous updates on the bacterial resistance to antibiotics and their particular regional patterns is crucial for the adequate approach of various infectious diseases. (2) Methods: We retrospectively analyzed 354 patients with Enterobacterales urinary tract infections (UTIs), determined their antibiotic resistance pattern, thus aiming to correlate them with the outcome and other specific markers of poor prognosis. (3) Results: The most frequent causative agent was Escherichia coli, representing 64.6% of all UTIs. We identified 154 patients resistant to multiple antibiotic classes, of which 126 were multidrug-resistant (MDR), 17 were extensive drug-resistant (XDR) and 11 were pandrug-resistant (PDR). Moreover, 25 isolates were resistant to carbapenems (CRE), 25 were difficult-to-treat (DTR), and 84 were extended-spectrum cephalosporin-resistant (ESC), with only 95 isolates susceptible to all tested antibiotics. Mortality ranged from 1% for UTIs caused by isolates susceptible to all tested antibiotics, to 24% for the ones caused by DTR or CRE isolates. Other significant risk factors associated with mortality were: prolonged hospital stay (p = 0.0001), Charlson comorbidity index ≥ 3 (p = 0.02), urinary catheterization (p = 0.001), associated respiratory pathologies (p = 0.004), obesity (p = 0.047), a history of previous hospitalizations (p = 0.007), inappropriate empiric antibiotic regimen (p = 0.001), or hyper inflammatory status (p = 0.006). Basically, we observed that a multiple regression model comprising urinary catheterization, inappropriate empiric anti-biotherapy, obesity, and respiratory comorbidities exhibits the best correlation with mortality rate in patients with UTI (R = 0.347, R2 = 0.12). (4) Conclusions: By focusing on the novel resistance patterns, our study provides complementary evidence concerning the resistance profiles found in an Eastern European region, as well as their prognostic implications in patients with UTI.

C6 Hydroxymethyl-Substituted Carbapenem MA-1-206 Inhibits the Major Acinetobacter baumannii Carbapenemase OXA-23 by Impeding Deacylation.

ABSTRACTAcinetobacter baumannii has become a major nosocomial pathogen, as it is often multidrug-resistant, which results in infections characterized by high mortality rates. The bacterium achieves high levels of resistance to β-lactam antibiotics by producing β-lactamases, enzymes which destroy these valuable agents. Historically, the carbapenem family of β-lactam antibiotics have been the drugs of choice for treating A. baumannii infections. However, their effectiveness has been significantly diminished due to the pathogen’s production of carbapenem-hydrolyzing class D β-lactamases (CHDLs); thus, new antibiotics and inhibitors of these enzymes are urgently needed. Here, we describe a new carbapenem antibiotic, MA-1-206, in which the canonical C6 hydroxyethyl group has been replaced with hydroxymethyl. The antimicrobial susceptibility studies presented here demonstrated that this compound is more potent than meropenem and imipenem against A. baumannii producing OXA-23, the most prevalent CHDL of this pathogen, and also against strains producing the CHDL OXA-24/40 and the class B metallo-β-lactamase VIM-2. Our kinetic and mass spectrometry studies revealed that this drug is a reversible inhibitor of OXA-23, where inhibition takes place through a branched pathway. X-ray crystallographic studies, molecular docking, and molecular dynamics simulations of the OXA-23-MA-1-206 complex show that the C6 hydroxymethyl group forms a hydrogen bond with the carboxylated catalytic lysine of OXA-23, effectively preventing deacylation. These results provide a promising strategy for designing a new generation of CHDL-resistant carbapenems to restore their efficacy against deadly A. baumannii infections.

Interactions Between Meropenem and Renal Drug Transporters.

Meropenem is a carbapenem antibiotic and is commonly used with other antibiotics for the treatment of bacterial infections. It is primarily eliminated renally by glomerular filtration and renal tubular secretion. This study aimed to evaluate the roles of renal uptake and efflux transporters in the excretion of meropenem and potential drug interactions mediated by renal drug transporters. Uptake and inhibition studies were conducted in human embryonic kidney 293 cells stably transfected with Organic Anion Transporter (OAT) 1, OAT3, Multidrug and Toxin Extrusion Protein (MATE) 1, and MATE2K, as well as membrane vesicles containing breast cancer resistance-related protein (BCRP), multidrug resistance protein 1 (MDR1), and Multidrug Resistance-associated Protein 2 (MRP2). Probenecid and piperacillin were used to assess potential drug interactions with meropenem in rats. We observed that meropenem was a low-affinity substrate of OAT1/3 and had a weak inhibitory effect on OAT1/3 and MATE2K. BCRP, MDR1, MRP2, MATE1, and MATE2K could not mediate renal excretion of meropenem. Moreover, meropenem was not an inhibitor of BCRP, MDR1, MRP2, or MATE1. Among five tested antibiotics, moderate inhibition on OAT3-mediated meropenem uptake was observed for linezolid (IC50 value was 69.2 μM), weak inhibition was observed for piperacillin, benzylpenicillin, and tazobactam (IC50 values were 282.2, 308.0 and 668.1 μM, respectively), and no inhibition was observed for sulbactam. Although piperacillin had a relatively high drug-drug interaction index (ratio of maximal unbound plasma concentration to IC50 was 1.42) in vitro, no meaningful impact was reported on the pharmacokinetics of meropenem in rats. Our results indicated that clinically significant interactions between meropenem and these five antibiotics are low.

Mechanisms of Action of Carbapenem Resistance.

Carbapenem antibiotics are the most effective antimicrobials for the treatment of infections caused by the most resistant bacteria. They belong to the category of β-lactams that include the penicillins, cephalosporins, monobactams and carbapenems. This class of antimicrobials has a broader spectrum of activity than most other beta-lactams antibiotics and are the most effective against Gram-positive and Gram-negative bacteria. All β-lactams antibiotics have a similar molecular structure: the carbapenems together with the β-lactams. This combination gives an extraordinary stability to the molecule against the enzymes inactivating the β-lactams. They are safe to use and therefore widespread use in many countries has given rise to carbapenem resistance which is a major global public health problem. The carbapenem resistance in some species is intrinsic and consists of the capacity to resist the action of antibiotics with several mechanisms: for the absence of a specific target, or an intrinsic difference in the composition of cytoplasmatic membrane or the inability to cross the outer membrane. In addition to intrinsic resistance, bacteria can develop resistance to antibiotics with several mechanisms that can be gathered in three main groups. The first group includes antibiotics with poor penetration into the outer membrane of bacterium or antibiotic efflux. The second includes bacteria that modify the target of the antibiotics through genetic mutations or post-translational modification of the target. The third includes bacteria that act with enzyme-catalyzed modification and this is due to the production of beta-lactamases, that are able to inactivate carbapenems and so called carbapenemases. In this review, we focus on the mode of action of carbapenem and the mechanisms of carbapenem resistance.