Molecular Characteristics of Colistin Resistance in Acinetobacter baumannii and the Activity of Antimicrobial Combination Therapy in a Tertiary Care Medical Center in Lebanon.

(1) Background: Infections with pan-drug-resistant (PDR) bacteria, such as A. baumannii, are becoming increasingly common, especially in healthcare facilities. In this study, we selected 15 colistin-resistant clinical A. baumannii isolates from a hospital in Beirut, Lebanon, to test combination therapies and determine their sequence types (STs) and the mechanism of colistin resistance using whole-genome sequencing (WGS). (2) Methods: Antimicrobial susceptibility testing via broth microdilution against 12 antimicrobials from different classes and growth rate assays were performed. A checkerboard assay was conducted on PDR isolates using six different antimicrobials, each in combination with colistin. Genomic DNA was extracted from all isolates and subjected to WGS. (3) Results: All isolates were resistant to all tested antimicrobials with the one exception that was susceptible to gentamicin. Combining colistin with either meropenem, ceftolozane-tazobactam, or teicoplanin showed synergistic activity. Sequencing data revealed that 67% of the isolates belonged to Pasteur ST2 and 33% to ST187. Furthermore, these isolates harbored a number of resistance genes, including blaOXA-23. Mutations in the pmrC gene were behind colistin resistance. (4) Conclusions: With the rise in antimicrobial resistance and the absence of novel antimicrobial production, alternative treatments must be found. The combination therapy results from this study suggest treatment options for PDR ST2 A. baumannii-infected patients.

Pharmacokinetic and pharmacodynamic evaluation of the atypical tetracyclines chelocardin and amidochelocardin in murine infection models.

IMPORTANCE: There is a strong need to find novel treatment options against urinary tract infections associated with antimicrobial resistance. This study evaluates two atypical tetracyclines, namely chelocardin (CHD) and amidochelocardin (CDCHD), with respect to their pharmacokinetics and pharmacodynamics. We show CHD and CDCHD are cleared at high concentrations in mouse urine. Especially, CDCHD is highly effective in an ascending urinary tract infection model, suggesting further preclinical evaluation.

Antimicrobial effects of chlorine dioxide in a hospital setting.

Chlorine dioxide is a powerful disinfectant with strong antibacterial properties. We conducted a study at different sites of the Lebanese American University Medical Center-Rizk Hospital to determine the efficacy of the ECOM air mask in decreasing the particle load. Air cultures were obtained from three different locations, namely the patients' elevator, visitors' elevator and mobile clinic and the number of colonies grown on each type of agar was determined. We also measured particle counts at the three sites both at baseline and after placement of the ECOM air mask. After 7 days of ECOM air mask use, the numbers of colonies grown on all types of media was decreased by 20-100% versus the baseline values. The counts of particles of different diameters (0.3, 0.5 and 5 µm) were decreased at all three sampled sites. This study highlighted the efficacy of the ECOM air mask. The utility of the gaseous form of ClO2 as an antiseptic in the hospital setting appears promising.

Molecular characterization and differential effects of levofloxacin and ciprofloxacin on the potential for developing quinolone resistance among clinical Pseudomonas aeruginosa isolates.

Background: Fluoroquinolones are some of the most used antimicrobial agents for the treatment of Pseudomonas aeruginosa. This study aimed at exploring the differential activity of ciprofloxacin and levofloxacin on the selection of resistance among P. aeruginosa isolates at our medical center. Methods: 233 P. aeruginosa clinical isolates were included in this study. Antimicrobial susceptibility testing (AST) was done using disk diffusion and broth microdilution assays. Random Amplification of Polymorphic DNA (RAPD) was done to determine the genetic relatedness between the isolates. Induction of resistance against ciprofloxacin and levofloxacin was done on 19 isolates. Fitness cost assay was done on the 38 induced mutants and their parental isolates. Finally, whole genome sequencing was done on 16 induced mutants and their 8 parental isolates. Results: AST results showed that aztreonam had the highest non-susceptibility. RAPD results identified 18 clusters. The 19 P. aeruginosa isolates that were induced against ciprofloxacin and levofloxacin yielded MICs ranging between 16 and 256 µg/mL. Levofloxacin required fewer passages in 10 isolates and the same number of passages in 9 isolates as compared to ciprofloxacin to reach their breakpoints. Fitness cost results showed that 12 and 10 induced mutants against ciprofloxacin and levofloxacin, respectively, had higher fitness cost when compared to their parental isolates. Whole genome sequencing results showed that resistance to ciprofloxacin and levofloxacin in sequenced mutants were mainly associated with alterations in gyrA, gyrB and parC genes. Conclusion: Understanding resistance patterns and risk factors associated with infections is crucial to decrease the emerging threat of antimicrobial resistance.

Clinical predictors of mortality in patients with pseudomonas aeruginosa infection.

BACKGROUND: Infections caused by Pseudomonas aeruginosa are difficult to treat with a significant cost and burden. In Lebanon, P. aeruginosa is one of the most common organisms in ventilator-associated pneumonia (VAP). P. aeruginosa has developed widespread resistance to multiple antimicrobial agents such as fluoroquinolones and carbapenems. We aimed at identifying risk factors associated for P. aeruginosa infections as well as identifying independent risk factors for developing septic shock and in-hospital mortality. METHODS: We used a cross-sectional study design where we included patients with documented P. aeruginosa cultures who developed an infection after obtaining written consent. Two multivariable regression models were used to determine independent predictors of septic shock and mortality. RESULTS: During the observed period of 30 months 196 patients were recruited. The most common predisposing factor was antibiotic use for more than 48 hours within 30 days (55%). The prevalence of multi-drug resistant (MDR) P. aeruginosa was 10%. The strongest predictors of mortality were steroid use (aOR = 3.4), respiratory failure (aOR = 7.3), identified respiratory cultures (aOR = 6.0), malignancy (aOR = 9.8), septic shock (aOR = 18.6), and hemodialysis (aOR = 30.9). CONCLUSION: Understanding resistance patterns and risk factors associated with mortality is crucial to personalize treatment based on risk level and to decrease the emerging threat of antimicrobial resistance.

Antimicrobial-Resistant Infections after Turkey/Syria Earthquakes, 2023.

Increased rates of multidrug-resistant microbes have been reported after earthquakes. After the 2023 earthquakes in Turkey and Syria, the number of associated highly drug-resistant pathogens and nosocomial transmission will probably surge in hospitals treating injured patients. It is not too late to act to prevent antimicrobial-resistant infections from compounding these tragedies.

The under investigated facet of the COVID-19 pandemic: Molecular analysis of secondary bacterial infections at a COVID dedicated intensive care unit within a tertiary care center in Lebanon.

Background: The coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread worldwide. Secondary bacterial infections are associated with unfavorable outcomes in respiratory viral infections. This study aimed at determining the prevalence of secondary bacterial infections in COVID-19 patients admitted at a tertiary medical center in Lebanon. Methodology: From May till November, 2020, a total of 26 Gram-negative isolates were recovered from 16 patients during the course of their COVID-19 infection with Escherichia coli being the most prevalent. The isolates were assessed for their antimicrobial susceptibility by broth microdilution against 19 antimicrobial agents from different classes. Whole genome sequencing of 13 isolates allowed the mining of antimicrobial resistance (AMR) determinants as well as mobile genetic elements and sequence types (ST). Finally, broth microdilution with three different efflux pump inhibitors [theobromine, conessine and PheArg-ß-naphthylamide (PAßN)] was done. Results: Antimicrobial susceptibility testing showed that out of the 26 Gram-negative isolates, 1 (4%) was extensively drug resistant and 14 (54%) were multi-drug resistant (MDR). Whole genome sequencing results revealed a plethora of AMR determinants among the 13 sequenced isolates. Moreover, the 9 Enterobacterales and 4 Pseudomonas aeruginosa sequenced isolates belonged to 9 and 2 different ST, respectively. Using a variety of efflux pump inhibitors we demonstrated that only PAßN had a significant effect when combined with levofloxacin, and the latter regained its activity against two P. aeruginosa isolates. Conclusion: The identification of carbapenem and colistin resistant Gram-negative bacilli causing secondary bacterial infections in critical patients diagnosed with COVID-19 should be of high concern. Additionally, it is crucial to monitor and track AMR, post-COVID pandemic, in order to better understand the effect of this disease on AMR exacerbation.

Facial microbial flora in bearded versus nonbearded men in the operating room setting: A single-center cross-sectional STROBE-compliant observational study.

Beards are controversial in the operating room setting because of the possible retention and shedding of pathogens. Surgical site infection poses a significant burden on healthcare systems. All male healthcare workers who entered the operating room were approached to participate in the study. Four facial swab samples were anonymously collected and a hygiene practice questionnaire was administered. Sample A was taken from the upper and lower lips, sample B from cheeks, and samples C and D were collected by 20 and 40 cm shedding below the face. Colony-forming units (CFUs) and minimum inhibitory concentrations (MICs) of meropenem resistance were determined for samples A and B. Random samples from A, B, C, and D, in addition to meropenem-resistant isolates were cultured with chlorohexidine. Sixty-one bearded and 19 nonbearded healthcare workers participated in the study. 98% were positive for bacterial growth with CFU ranging between 30 × 104 and 200 × 106 CFU/mL. Bacterial growth was significantly higher in bearded participants (P < .05). Eighteen (27.1%) isolates were resistant to meropenem; of these which 14 (77.8%) were from bearded participants, this was not statistically significant. Chlorohexidine was effective in inhibiting the growth of all strains including the meropenem-resistant isolates. Bearded men in the operating room had a significantly higher facial bacterial load. Larger-scale resistance studies are needed to address facial bacterial resistance among healthcare workers in the operating room. This study aimed to estimate the facial microbial load and identify strains and antimicrobial resistance profiles in bearded versus nonbearded male healthcare workers in the operating room of a tertiary hospital in the Middle East.

HAS 1: A natural product from soil-isolated Streptomyces species with potent activity against cutaneous leishmaniasis caused by Leishmania tropica.

Cutaneous Leishmaniasis (CL) is a neglected tropical disease, classified by the World Health Organization (WHO) as one of the most unrestrained diseases. The Syrian war and the significant displacement of refugees aggravated the spread of this ailment into several neighboring countries in the Eastern Mediterranean Region (EMR). In Syria, Leishmania tropica is identified as one of the most aggressive and endemic identified species, causing localized or generalized lesions, often chronic or relapsing. Pentavalent antimonial drugs are currently used as first line treatment against CL. Nonetheless, these drugs exhibit several limitations, including the repetitive painful injections, high cost, poor availability, and mainly systemic toxicity. Besides, the emergence of acquired parasitic resistance hinders their potency, stressing the need for new therapies to combat CL. Natural products (NPs) epitomize a valuable source in drug discovery. NPs are secondary metabolites (SMs) produced by plants, sponges, or a wide variety of organisms, including environmental microorganisms. The EMR is characterized by its immense biodiversity, yet it remains a relatively untapped area in drug discovery. NPs of the region were explored over the last 2 decades, but their discoveries lack biogeographical diversity and are limited to the Red Sea. Here, we isolated previously uncultured environmental soil-dwelling Streptomyces sp. HAS1, from Hasbaya region in southeast Lebanon. When fermented in one of our production media named INA, HAS1 produced a crude extract with significant potency against a clinical Leishmania tropica isolate. Using bio-guided fractionation, the bioactive compound was purified and the structure was elucidated by NMR and LC-HRMS. Our findings establish NPs as strong candidates for treating Leishmania tropica and further dwells on the importance of these natural sources to combat microbial infections.

Urinary Tract Infections Impair Adult Hippocampal Neurogenesis.

Previous studies have suggested a link between urinary tract infections (UTIs) and cognitive impairment. One possible contributing factor for UTI-induced cognitive changes that has not yet been investigated is a potential alteration in hippocampal neurogenesis. In this study, we aim to investigate the effect of UTI on brain plasticity by specifically examining alterations in neurogenesis. Adult male Sprague Dawley rats received an intra-urethral injection of an Escherichia coli (E. coli) clinical isolate (108 CFU/mL). We found that rats with a UTI (CFU/mL ≥ 105) had reduced proliferation of neural stem cells (NSCs) at an early time point post infection (day 4) and neurogenesis at a later time point (day 34). This was associated with the decreased expression in mRNA of BDNF, NGF, and FGF2, and elevated expression of IL-1ß in the hippocampus at 6 h post infection, but with no changes in optical intensity of the microglia and astrocytes. In addition, infected rats spent less time exploring a novel arm in the Y-maze test. Treatment with an anti-inflammatory drug did not revert the effect on NSCs, while treatment with antibiotics further decreased the basal level of their proliferation. This study presents novel findings on the impact of urinary tract infections on hippocampal neurogenesis that could be correlated with cognitive impairment.

Acquired resistome and plasmid sequencing of mcr-1 carrying MDR Enterobacteriaceae from poultry and their relationship to STs associated with humans.

OBJECTIVES: To investigate the acquired resistome in 18 colistin-resistant Escherichia coli isolated from different poultry farms in Lebanon, analyse Inc plasmids associated with mcr and assess potential transmission to humans. METHODS: A total of 18 E. coli were recovered from poultry faeces collected from different poultry farms in Lebanon. Broth microdilution (BMD) assay was performed to determine the antimicrobial resistance profiles. WGS was used to identify the genetic determinants behind the resistance in these isolates. RESULTS: BMD results showed that all of the 18 isolates were colistin resistant. Furthermore, resistance to trimethoprim/sulfamethoxazole was the most recorded among the isolates and only one isolate was resistant to cefepime. Sequencing results showed that the isolates were distributed into seven different STs and that the most abundant was ST1140. The number of antimicrobial resistant determinants ranged from 4 to 21 among the 18 isolates, with tet(A) and floR being the most frequent. Moreover, a total of 15 different plasmid replicon types were identified. The mcr-1 gene was shown to be predominantly located on IncX4 plasmids. Additionally, two isolates harboured the IncI2-type self-conjugative plasmid. CONCLUSIONS: The findings show that mcr and other important resistance determinants occur in MDR E. coli isolated poultry farms in Lebanon. The occurrence of mcr on mobile plasmids and the zoonotic potential and clinical relevance of some strains highlight a risk of transmission to humans.

Diversity of Sequence Types and Impact of Fitness Cost among Carbapenem-Resistant Acinetobacter baumannii Isolates from Tripoli, Libya.

We investigated the molecular epidemiology of 21 carbapenem-resistant Acinetobacter baumannii isolates from Libya and assessed their relative fitness. Core genome multilocus sequence typing (MLST) revealed five interhospital transmission clusters. Three clusters were associated with the international clones (IC) IC1, IC2, and IC7. Carbapenem-resistance was associated with blaOXA-23, blaGES-11, or blaNDM-1. Compared to that of A. baumannii DSM 30008, the doubling time was similar over 10 h, but after 16 h, half the isolates grew to higher densities, suggesting a fitness advantage.

An unequivocal superbug: PDR Klebsiella pneumoniae with an arsenal of resistance and virulence factor genes.

INTRODUCTION: Infections caused by extensively-drug resistant (XDR) and pan-drug resistant (PDR) Klebsiella pneumoniae represent an emerging threat due to the high associated mortality. This study aimed to characterize two carbapenem resistant K. pneumoniae strains from the same patient, the first being PDR (referred to as IMP 1078b) and the second being XDR (referred to IMP 1078s) isolated from the same patient. METHODOLOGY: Antimicrobial susceptibility testing was done for the 2 K. pneumoniae isolates, followed by carbapenem/ß-lactamase inhibitor combination assay, and fitness cost against cefepime and meropenem. Then, whole-genome sequence analysis was performed to decipher the molecular mechanisms behind the high level of resistance recorded in both isolates. Finally, qRT-PCR was done for ß-lactam resistant genes. RESULTS: This is the first report about a K. pneumoniae isolate harboring 47 antimicrobial resistance genes and having type IV pilli (Yersinia) and the fimbrial adherence determinant Stb (Salmonella) as virulence factors. Further analysis on both isolates are discussed within the article. CONCLUSION: The co-existence of a high number of antimicrobial resistant (AMR) genes and virulence factor genes may lead to a life threatening invasive and untreatable infection.

The Microbiome of the Lebanese Wild Apple, Malus trilobata, is a Rich Source of Potential Biocontrol Agents for Fungal Post-harvest Pathogens of Apples.

The widespread use of harmful fungicides in the agricultural sector has led to a demand for safer alternatives to protect against crop pathogens. The domestic apple is the second most highly consumed fruit in the world and encounters several pre- and post-harvest fungal and bacterial phytopathogens. The goal of this study was to explore the uncharacterized microbiome of a wild apple, Malus trilobata, as a potential source of novel biocontrol agents for two post-harvest fungi that affect commercial apples: Botrytis cinerea and Penicillium expansum. We sampled microflora associated with the leaves, bulk soil, and roots of Malus trilobata in two regions of Lebanon: Ehden reserve in the north and Dhour EL Choueir near Beirut. The two regions have different soil types Dhour EL Choueir and samples from the two regions showed very different microbial compositions, with greater microbial diversity among those from Ehden reserve. Molecular characterization revealed a wide variety of genera displaying activity against the two fungal pathogens, including several with previously unknown antifungal activity: Bosea, Microlunatus, Microbacterium, Mycetecola, Rhizobium and Paraphoma. In total, 92 strains inhibited Penicillium expansum (39%) and 87 strains inhibited Botrytis cinerea (38%) out of 237 screened. Further chemical and genetic characterization of one or more selected strains could pave the way for future development of new biocontrol agents for post-harvest applications.

SynBio-SynChem Approaches to Diversifying the Pacidamycins through the Exploitation of an Observed Pictet-Spengler Reaction.

A nonenzymatic Pictet-Spengler reaction has been postulated to give rise to a subset of naturally occurring uridyl peptide antibiotics (UPAs). Here, using a combination of strain engineering and synthetic chemistry, we demonstrate that Pictet-Spengler chemistry may be employed to generate even greater diversity in the UPAs. We use an engineered strain to afford access to meta-tyrosine containing pacidamycin 4. Pictet-Spengler diversification of this compound using a small series of aryl-aldehydes was achieved with some derivatives affording remarkable diastereomeric control.

Natural products and polysorbates: Potential Inhibitors of biofilm formation in Pseudomonas aeruginosa.

INTRODUCTION: With all the challenges super bugs are imposing, biofilm formation opens the door against various more complicated challenges. Such issue may be highlighted with the ability of the latter to render the antibiotics hardly accessible to bacterial cells and sheds the light on the importance of finding antibiofilm formers. Therefore, we assessed the inhibitory effect of natural product extracts (ginger, wild blueberry) and polysorbates (PS20, PS80) on biofilm formation at the molecular level. METHODOLOGY: Growth inhibition assay was performed to test the effect of ginger (Zingiber Officinale), wild blueberry (Vaccinium Angustifolium), and polysorbates on Pseudomonas aeruginosa (PAN14) growth. Transcription levels of biofilm exopolysaccharides encoding genes (ndvB, pelC, algC) and quorum sensing genes (lasI, lasR, rhlI, rhlR) for LasI/LasR and RhlI/ RhlR systems were evaluated by RT qPCR. RESULTS: The polysorbates and the extracts of both ginger and wild blueberry had no effect on the growth of P. aeruginosa. Biofilms' examination has unraveled the effectiveness of treatments used in reducing its formation. Moreover, a significant reduction in the expression of all genes tested for biofilm exopolysaccharides and its quorum sensing system was observed. CONCLUSION: The decrease in the relative gene expression of the exopolysaccharides and quorum sensing encoding genes sheds the light on the mechanism of action of ginger and wild blueberry's constituents as well as polysorbates 20 and 80 on P. aeruginosa biofilm formation. Future studies need to assess the antibiofilm effect of each fraction of herbal extracts separately.

Phenotypic and Genotypic Characterization of Extended-Spectrum Beta-Lactamases Produced by Escherichia coli Colonizing Pregnant Women.

Introduction: Infections caused by extended spectrum beta lactamase (ESBL) producing bacteria continue to be a challenge for choosing the appropriate therapy since they may exhibit coresistance to many other classes of antibiotics. The aim of the study was to screen pregnant women for ESBL producing bacteria in Beirut, Lebanon, to examine their phenotypic and genotypic characterization and to study the association between ESBL colonization with adverse neonatal outcomes. Method: In this cross-sectional study, vaginal samples from 308 pregnant women at 35-37 weeks of gestation were studied during a one-year period. The samples were plated on MacConkey agar and selective MacConkey agar supplemented with ceftazidime. Phenotypic confirmation of ESBL production was performed by double-disc synergy test and all isolates were screened by PCR for the resistance genes blaSHV, blaTEM, and blaCTX-M. Clonal relatedness of Escherichia coli isolates was investigated by pulsed-field gel electrophoresis. Results: In total, 59 women out of 308 (19.1%) were colonized by ESBL producing gram negative bacteria. Two babies born to mothers colonized with ESBL were diagnosed with sepsis. The susceptibility rates of isolates to other antibiotics were 39% to co-trimoxazole, 49.2% to ciprofloxacin, 91.5% to gentamicin, 18.6% to aztreonam and 35.6% to cefepime. Most of isolates were highly sensitive to meropenem and imipenem, with a susceptibility of 93.2%. PCR was performed on all E. coli isolates to detect the most common ESBL producing genes; blaCTX-M was the predominant gene (90.7%), followed by blaTEM (88.4%) and finally blaSHV (44.2%). PFGE analysis of 34 E. coli isolates revealed 22 distinct clusters showing more than 85% similarity. Conclusion: In conclusion, this study showed that Lebanon has a high prevalence of ESBL carriage in pregnant women. Further studies that include a continuous screening of pregnant women and follow up of their newborn clinical status should be conducted to foresee the risk of transmission.

Heavy Metal Toxicity in Armed Conflicts Potentiates AMR in A. baumannii by Selecting for Antibiotic and Heavy Metal Co-resistance Mechanisms.

Acinetobacter baumannii has become increasingly resistant to leading antimicrobial agents since the 1970s. Increased resistance appears linked to armed conflicts, notably since widespread media stories amplified clinical reports in the wake of the American invasion of Iraq in 2003. Antimicrobial resistance is usually assumed to arise through selection pressure exerted by antimicrobial treatment, particularly where treatment is inadequate, as in the case of low dosing, substandard antimicrobial agents, or shortened treatment course. Recently attention has focused on an emerging pathogen, multi-drug resistant A. baumannii (MDRAb). MDRAb gained media attention after being identified in American soldiers returning from Iraq and treated in US military facilities, where it was termed "Iraqibacter." However, MDRAb is strongly associated in the literature with war injuries that are heavily contaminated by both environmental debris and shrapnel from weapons. Both may harbor substantial amounts of toxic heavy metals. Interestingly, heavy metals are known to also select for antimicrobial resistance. In this review we highlight the potential causes of antimicrobial resistance by heavy metals, with a focus on its emergence in A. baumanni in war zones.

Evaluating the Efficacies of Carbapenem/ß-Lactamase Inhibitors Against Carbapenem-Resistant Gram-Negative Bacteria in vitro and in vivo.

BACKGROUND: Carbapenem-resistant Gram-negative bacteria are a major clinical concern as they cause virtually untreatable infections since carbapenems are among the last-resort antimicrobial agents. ß-Lactamases implicated in carbapenem resistance include KPC, NDM, and OXA-type carbapenemases. Antimicrobial combination therapy is the current treatment approach against carbapenem resistance in order to limit the excessive use of colistin; however, its advantages over monotherapy remain debatable. An alternative treatment strategy would be the use of carbapenem/ß-lactamase inhibitor (ßLI) combinations. In this study, we assessed the in vitro and in vivo phenotypic and molecular efficacies of three ßLIs when combined with different carbapenems against carbapenem-resistant Gram-negative clinical isolates. The chosen ßLIs were (1) Avibactam, against OXA-type carbapenemases, (2) calcium-EDTA, against NDM-1, and (3) Relebactam, against KPC-2. METHODS: Six Acinetobacter baumannii clinical isolates were screened for bla OXA-23-like, bla OXA-24/40, bla OXA-51-like, bla OXA-58, and bla OXA-143-like, and eight Enterobacteriaceae clinical isolates were screened for bla OXA-48, bla NDM-1, and bla KPC-2. The minimal inhibitory concentrations of Imipenem (IPM), Ertapenem (ETP), and Meropenem (MEM) with corresponding ßLIs for each isolate were determined. The efficacy of the most suitable in vitro treatment option against each of bla OXA-48, bla NDM-1, and bla KPC-2 was assessed via survival studies in a BALB/c murine infection model. Finally, RT-qPCR was performed to assess the molecular response of the genes of resistance to the carbapenem/ßLI combinations used under both in vitro and in vivo settings. RESULTS: Combining MEM, IPM, and ETP with the corresponding ßLIs restored the isolates' susceptibilities to those antimicrobial agents in 66.7%, 57.1%, and 30.8% of the samples, respectively. Survival studies in mice revealed 100% survival rates when MEM was combined with either Avibactam or Relebactam against bla OXA-48 and bla KPC-2, respectively. RT-qPCR demonstrated the consistent overexpression of bla OXA-48 upon treatment, without hindering Avibactam's activity, while bla NDM-1 and bla KPC-2 experienced variable expression levels upon treatment under in vitro and in vivo settings despite their effective phenotypic results. CONCLUSION: New carbapenem/ßLI combinations may be viable alternatives to antimicrobial combination therapy as they displayed high efficacy in vitro and in vivo. Meropenem/Avibactam and Meropenem/Relebactam should be tested on larger sample sizes with different carbapenemases before progressing further in its preclinical development.