OXA-type Carbapenemases Research Articles

Phenotypic and genotypic identification of class C and D β-lactamases in clinical isolates of Pseudomonas aeruginosa: a cross-sectional study.

The emergence of Pseudomonas aeruginosa (P. aeruginosa) antibiotic resistance is an important public health problem worldwide that can negatively affect infection control. Therefore, obtaining knowledge about antibiotic resistance mechanisms is necessary for infection control policies. This study aimed to determine the frequency of class C and D β-lactamases in P. aeruginosa strains isolated from patients referred to Ardabil hospitals using phenotypic and genotypic tests. Phenotypic detection of β-lactamases including AmpC cephalosporinase, oxacillinase (OXA)-type extended-spectrum β-lactamases (ESBLs), and OXA-type carbapenemases were performed using the disk diffusion-based methods. Amplification of genes encoding classes C (ampC and FOX genes) and D (OXA-1, OXA-2, OXA-10, OXA-23, and OXA-48 genes) β-lactamases was performed using the polymerase chain reaction (PCR) method. A quantitative reverse transcription PCR (qRT-PCR) method was used to determine the expression level of the ampC gene among multiple drug-resistant and imipenem-resistant P. aeruginosa strains. In phenotypic tests, the prevalence of AmpC cephalosporinase, OXA-type ESBLs, and OXA-type carbapenemases were 52.5%, 7.2%, and 95.8%, respectively. In genotypic tests, the prevalence of ampC, FOX, OXA-1, OXA-2, OXA-10, OXA-23, and OXA-48 genes were 100%, 0%, 4.3%, 60.8%, 42%, 29.7%, and 2.9%, respectively. In addition, the ampC gene overexpression was seen in 16 (33.3%) drug-resistant P. aeruginosa clinical isolates. Given the presence of class C and D β-lactamases in clinical isolates of P. aeruginosa in Ardabil hospitals, early detection of these strains can help prevent the spread of resistant strains in hospital environments and subsequent treatment failure.

Detection of Carbapenem Resistance Using the Genotypic and Phenotypic Methods in Klebsiella pneumoniae

Aim: This study aimed to detect the carbapenem resistance of the Klebsiella pneumoniae strains, isolated from clinical specimens with genotypic and phenotypic methods. Material and Methods: A total of 87 Klebsiella pneumoniae strains whose carbapenem resistance was determined by disc diffusion method were included in the study. Carbapenemase was investigated using the combined disk method and polymerase chain reaction (PCR). Results: The evaluation of the PCR results demonstrated that OXA was detected in 60 (68.9%) samples, NDM was detected in 20 (22.9%), OXA + NDM in 5 (5.7%), and KPC was detected in 1 (1.1%) out of 87 clinical samples. Carbapenemase was not detected in one specimen with the PCR method. The results were found compatible with the combined disc test results for all isolates which were detected as only OXA, NDM, and KPC type carbapenemase positive. In 5 (5.7%) strains in which the co-existence of NDM and OXA type carbapenemases was detected by PCR, the combined disc method detected only OXA type carbapenemase. Conclusion: The combined disk method is inadequate in the presence of strains that have multiple carbapenemases, and also have OXA which is the most frequently detected carbapenemase in our hospital. EUCAST recommends verification by other methods in the presence of OXA-48. Genotypic methods can be used for confirmation testing. The detections of strains with NDM, multiple carbapenemases, and the first detection of KPC were striking in the study. Monitoring the spread of these strains in the hospital will be necessary for infection control.

Comparison of Three Different Methods in Investigating the Molecular Epidemiology of Carbapenem-Resistant Acinetobacter baumannii Clinical Isolates

The aim of the study was to evaluate the relationship between carbapenem-resistant Acinetobacter baumannii isolates carrying oxacillinase-type carbapenemase genes with "international high-risk clones" (IC I, II, and III) by different molecular epidemiological methods and to statistically compare the concordance and discrimination power of the methods. Carbapenem-resistant and moderately susceptible A.baumannii isolates from non-repeating blood cultures of 72 patients were included in the study. The presence of "blaOXA-23 , blaOXA-24 , blaOXA-51 ve blaOXA-58 " genes within OXA-type carbapenemases was detected by polymerase chain reaction (PCR) method and confirmed by DNA sequence analysis. Pulsed f ield gel electrophoresis (PFGE), multilocus sequence typing (MLST) and matrix-assisted laser desorption/ ionization time- of-flight mass spectrometry (MALDI-TOF MS) analyses were performed to evaluate the clonal relations of IC I, II and III clones together with clinical isolates. In the statistical comparison of the methods, discrimination power was evaluated by Simpson index of diversity (SID) and concordance by "Wallace coefficient". All of the isolates were found to carry blaOXA-23 and blaOXA-51 genes. As a result of the bioinformatic analysis of the four isolates selected for sequence analysis; blaOXA-23 and blaOXA-51 genes were detected in the selected isolates, and the analysis of two isolates carrying blaOXA-51 gene showed 99% similarity with blaOXA-92 gene. The isolates were clustered into five pulsotypes (A, B, C, D and E) according to ≥ 85% similarity coefficient by PFGE. The isolates and RUH 875, RUH 134, LUH 5875 strains belonging to high-risk clones ICI, ICII and ICIII, respectively, were divided into five main groups [A (n= 58), B (n= 8), C (n= 4), D (n= 4) and E (n= 1)] and 10 subgroups (A1, A2, A4, A5, A6, A9, B1, B4, C3, D1) by PFGE. IC clone III (E1) and seven strains showed singleton PFGE profiles (A3, A7, A8, B2, B3, C1, C2). ICII was found in A5 subtype, ICI in C1 subtype and ICIII in E1 subtype. By PFGE subtype groups, 18 pulsotypes were determined and ST1, ST2, ST81, ST157 and ST604 sequence types were found in 20 isolates randomly selected from pulsotypes according to MLST Pasteur scheme (cpn60, fusA, gltA, pyrG, recA, rplB, rpoB). Principal component analysis (PCA) of the spectra of 72 A. baumannii isolates and ICI, ICII and ICIII clones was performed by MALDI-TOF MS. In PCA analysis, the cluster distance level was defined as 1.5 and the isolates were divided into three clusters. IC clone I, II and III together with 70 clinical isolates were grouped in one cluster, while two clinical isolates (AB083 and AB0115) formed singleton clusters. There was no significant agreement between MALDI-TOF MS; MLST and PFGE data according to Wallace coefficient. It was found that PFGE method gave significant results in terms of discrimination power with SID coefficient, MALDI-TOF MS PCA analysis had the lowest discrimination power value, and the Wallace coefficient result of PFGE and MLST was concordant. In conclusion, MALDI-TOF MS may not function as a gold standard method like PFGE and MLST for epidemiological analysis in A.baumannii species and the epidemiological typing protocols used for MALDI-TOF MS need to be improved and developed.

2172. Activity of Cefiderocol and Comparator Agents Against Molecularly Characterized Multidrug-resistant Enterobacterales Clinical Isolates from United States Hospitals (2020–2022)

Abstract Background Cefiderocol (CFDC) is a siderophore cephalosporin that hijacks the iron transport system of Gram-negative bacteria to facilitate cell entry and reach its target. CFDC remains stable to hydrolysis in the presence of serine β-lactamases (ESBLs, KPC, and OXA-type carbapenemases) and metallo-β-lactamases (MBL). CFDC and comparator activities were analyzed against Enterobacterales (ENT), including molecularly characterized isolates, as part of the US SENTRY Antimicrobial Surveillance Program. Methods 11,884 ENT were collected from 33 sites in the USA in 2020–2022. Susceptibility (S) testing was performed by broth microdilution. CFDC testing utilized iron-depleted media. CLSI breakpoints were used. E. coli, K. pneumoniae, and P. mirabilis with ceftriaxone, ceftazidime, or aztreonam MIC ≥ 2 μg/mL plus any ENT displaying an MIC ≥ 2 μg/mL for imipenem (excluding P. mirabilis, P. penneri, and indole-positive Proteeae) or meropenem (MER) were subjected to genome sequencing and screening of β-lactamase genes. Results CFDC (99.8%S), imipenem-relebactam (IMR; 98.0%S), meropenem-vaborbactam (MEV; 100%S), and ceftazidime-avibactam (CZA; 100%S) were active against carbapenem-susceptible ENT that carried ESBL and/or AmpC genes (Table). CFDC (MIC50/90, 0.5/4 μg/mL; 97.6%S) and CZA (MIC50/90, 1/8 μg/mL; 91.5%S) were the most active agents against carbapenem-nonS isolates, whereas IMR (MIC50/90, 0.25/4 μg/mL; 81.2%S) and MEV (MIC50/90, 0.12/8 μg/mL; 87.9%S) had suboptimal activity. CFDC (MIC50/90, 0.5/4 μg/mL), IMR (MIC50/90, 0.12/0.5 μg/mL), MEV (MIC50/90, 0.03/1 μg/mL), and CZA (MIC50/90, 1/2 μg/mL) were active (98.7–100%S) against the KPC subset. CFDC (MIC, 2/4 μg/mL; 90.9%S) was also active against ENT carrying MBL genes, whereas CFDC (MIC, 0.5-2 μg/mL; 100%S) and CZA (0.5-4 μg/mL; 100%S) were active against isolates carrying blaOXA-48–like. Conclusion CFDC activity against ENT was consistent, regardless of isolate phenotypes or genotypes, including against isolates carrying carbapenemase genes other than blaKPC, where approved β-lactam/β-lactamase inhibitor combinations showed limited activity. These data emphasize CFDC as an important option for the treatment of infections caused by ENT and resistant subsets. Disclosures Rodrigo E. Mendes, PhD, AbbVie: Grant/Research Support|Basilea: Grant/Research Support|Cipla: Grant/Research Support|Entasis: Grant/Research Support|GSK: Grant/Research Support|Paratek: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support John H. Kimbrough, PhD, AbbVie: Grant/Research Support|Basilea: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support Valerie Kantro, BA, AbbVie: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support Dee Shortridge, PhD, Melinta: Grant/Research Support|Shionogi: Grant/Research Support Helio S. Sader, MD, PhD, FIDSA, AbbVie: Grant/Research Support|Basilea: Grant/Research Support|Cipla: Grant/Research Support|Paratek: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support Mariana Castanheira, PhD, AbbVie: Grant/Research Support|Basilea: Grant/Research Support|bioMerieux: Grant/Research Support|Cipla: Grant/Research Support|CorMedix: Grant/Research Support|Entasis: Grant/Research Support|Melinta: Grant/Research Support|Paratek: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support

A global view on carbapenem-resistant Acinetobacter baumannii.

Carbapenem-resistant Acinetobacter baumannii are of increasing public health importance, as they are resistant to last-line antibiotics. International clones with well-characterized resistance genes dominate globally; however, locally, other lineages with different properties may be of importance to consider. This study investigated isolates from a broad geographic origin from 114 hospitals in 47 countries and from five world regions ensuring the greatest possible diversity in an organism known for its propensity for clonal epidemic spread and reflecting the current global epidemiology of carbapenem-resistant A. baumannii. In Latin America, a lineage different from other geographic regions circulates, with a different resistance gene profile. This knowledge is important to adjust local infection prevention measures. In a global world with migration and increasing use of antimicrobials, multidrug-resistant bacteria will continue to adapt and challenge our healthcare systems worldwide.

Evaluation of NG-Test CARBA 5 version 2, Cepheid Xpert Carba-R, and carbapenem inactivation methods in comparison to whole-genome sequencing for the identification of carbapenemases in non-fermenting Gram-negative bacilli.

NG-Test CARBA 5 (NG-Biotech) is a rapid in vitro multiplex immunoassay for the phenotypic detection and differentiation of the "big five" carbapenemase families (KPC, OXA-48-like, VIM, IMP, and NDM). Version 2 of this assay was evaluated alongside the Xpert Carba-R assay (Cepheid, Inc.), the modified carbapenem inactivation method (mCIM), and the CIMTris assay, with a collection of carbapenem-resistant non-fermenting Gram-negative bacilli comprising 138 Pseudomonas aeruginosa and 97 Acinetobacter baumannii isolates. Whole-genome sequencing (WGS) was used as the reference standard. For P. aeruginosa, NG-Test CARBA 5 produced an overall percentage agreement (OPA) with WGS of 97.1%, compared with 92.8% forXpert Carba-R and 90.6% for mCIM. For A. baumannii, as OXA-type carbapenemases (non-OXA-48) are not included, both the NG-Test CARBA 5 and Xpert Carba-R only had an OPA of 6.2%, while the CIMTris performed well with an OPA of 99.0%. The majority of A. baumannii isolates (95.9%) tested falsely positive for IMP on NG-Test CARBA 5; no IMP genes were found on WGS. No clear cause was found for this phenomenon; a cross-reacting protein antigen unique to A. baumannii is a possible culprit. NG-Test CARBA 5 performed well for carbapenemase detection in P. aeruginosa. However, results from A. baumannii isolates should be interpreted with caution.

Frequency of OXA-Type Carbapenemases among Carbapenem-Resistant Acinetobacter baumannii in Clinical Isolates from Adult Intensive Care Unit in India

Abstract Purpose Acinetobacter baumannii is a highly virulent bacteria in modern health care, with a high ability to acquire antimicrobial resistance. Carbapenemases production appears to be the most common mechanism involved in drug resistance to carbapenem. As the prevalence of carbapenem-resistant A. baumannii was high in intensive care unit (ICU) patients, this study was designed to find the frequency of oxacillinases (OXA) genes including OXA-23, OXA-24, OXA-51, and OXA-58. Materials and Methods A clinical specimen was collected from patients admitted to the adult ICU. DNA was isolated from carbapenem-resistant A. baumannii and amplified using conventional polymerase chain reaction technique and gel electrophoresis for visualization of results. Results The frequency of the OXA-23 gene was high with 87.5%, followed by OXA-51 gene with 73.2%. All 56 isolates were negative for the OXA-24 and OXA-58 genes. We also found that both OXA-23 and OXA-51 genes coexisted in 40 (71.4%) isolates. No significant difference was found between drug-resistant genes (OXA-23 and OXA-51) and clinical outcomes. The relationship between the presence of OXA gene was compared between survivors and nonsurvivors, which was found out to be nonsignificant. The presence of OXA genes showed no significant increase in the length of hospital stay. The significant association between acute physiology and chronic health evaluation IV scores and clinical outcome was calculated, and it was evident in the comparison of the discharged and died groups. Conclusion Early detection of these drug-resistant genes by molecular methods is essential in decreasing the spread of carbapenem-resistant A. baumannii.

Two non-active site residues W165 and L166 prominently influence the beta-lactam hydrolytic ability of OXA-23 beta-lactamase.

Dissemination of class D OXA-type carbapenemases is one of the significant causes of beta-lactam resistance in Gram-negative bacteria. The amino acid residues present near the active site are involved in hydrolytic mechanism of class D carbapenemases, though it is not identified in OXA-23. Here, with the help of site-directed mutagenesis, we aimed to explicate the importance of the residues W165, L166 and V167 of the possible omega loop and residue D222 in the short β5-β6 loop on the activity of OXA-23. All the residues were substituted with alanine. The resultant proteins were assayed for the changes in activity in E. coli cells and purified for in vitro activity, and stability assessment. E. coli cells harboring OXA-23_W165A and OXA-23_L166A, individually, exhibited a significant decrease in resistance towards beta-lactam antibiotics as compared to OXA-23. Further, purified OXA-23_W165A and OXA-23_L166A imparted about >4-fold decrease in catalytic efficiency and displayed reduced thermal stability as compared to OXA-23. Bocillin-FL binding assay revealed that W165A substitution results in improper N-carboxylation of K82, leading to deacylation deficient OXA-23. Therefore, we infer that the residue W165 maintains the integrity of N-carboxylated lysine (K82) of OXA-23 and the residue L166 might be responsible for properly orientating the antibiotic molecules.

Characterization of a novel carbapenem-hydrolysing β-lactamase OXA-1041 in Escherichia coli.

We found a carbapenem-resistant Escherichia coli without known carbapenemase-encoding genes and performed a study to identify the possible new carbapenemase. The production of carbapenemase was examined using the modified carbapenem inactivation method. The strain was subjected to short- and long-read genome sequencing and the complete genome was obtained by hybrid assembly. The gene encoding a potential new OXA-type carbapenemase was cloned. The enzyme was purified and was then subjected to kinetic assays. Molecular docking analysis of the enzyme was performed using the MOE software suite. Mating experiments were attempted to obtain the plasmid carrying the corresponding gene. We identified and characterized a novel class D carbapenem-hydrolysing β-lactamase, OXA-1041, in a carbapenem-resistant E. coli clinical strain. OXA-1041 had 89.77% (237/264) amino acid identity with OXA-427, a known carbapenemase. By cloning in an E. coli laboratory strain, blaOXA-1041 was found to reduce susceptibility to ertapenem by 16 times (MIC 0.25 versus 0.016 mg/L) and meropenem by four times (MIC 0.06 versus 0.016 mg/L) but did not significantly reduce susceptibility to imipenem and doripenem. Enzyme kinetic measurement of purified OXA-1041 showed that OXA-1041 could hydrolyse ertapenem and meropenem with a turnover number (kcat)/Michaelis constant (KM) of 8.57 and 3.63 mM-1s-1, respectively. The complete genome contained a single plasmid (223 341 bp, IncF, containing five replicons), which was self-transmissible. blaOXA-1041 was downstream of insertion sequence ISCR1 and there were three tandem copies of ISCR1-blaOXA-1041-creDΔ (encoding an envelope protein) on this plasmid. The above findings suggest OXA-1041 is a new plasmid-encoded carbapenemase with preferential activity against ertapenem.

Genotypic characterization and clonal relatednessof metallo-β-lactamase-producingnon-fermentative gram negative bacteria in the first 5years of their circulation in Paraguay(2011-2015).

Pseudomonas aeruginosa and species of Acinetobacter calcoaceticus-baumanii complex are multiresistant intrahospital opportunistic pathogens, able to acquire carbapenemases and produce outbreaks with high morbidity and mortality. Pseudomonas putida has also emerged with similar characteristics. The aim of this research was to characterize the Metallo-β-lactamases (MBLs) detected by surveillance in Paraguay in the first 5years of their circulation in hospitals. The coexistence of KPC and OXA-type carbapenemases was also investigated. 70 MBL-producing strains from inpatients were detected from clinical samples and rectal swab from 11 hospitals. The strains were identified by manual, automated, and molecular methods. Antimicrobial susceptibility was studied by Kirby-Bauer and automated methods, while colistin susceptibility was determined by broth macrodilution. MBLs were investigated by synergy with EDTA against carbapenems and PCR, and their variants by sequencing. KPC and OXA-carbapenemases were investigated by PCR. Clonality was studied by pulsed-field gel electrophoresis (PFGE). The results demonstrated the circulation of blaVIM-2 (60%), blaNDM-1 (36%), and blaIMP-18 (4%). The MBL-producing species were P. putida (45.7%), P. aeruginosa (17.2%), A. baumannii (24.3%), A. pittii (5.7%), A. nosocomialis, (4.3%) A. haemolyticus (1.4%), and A. bereziniae (1.4%). PFGE analysis showed one dominant clone for A. baumannii, a predominant clone for half of the strains of P. aeruginosa, and a polyclonal spread for P. putida. In the first 5years of circulation in Paraguay, MBLs were disseminated as unique variants per genotype, appeared only in Pseudomonas spp. and Acinetobacter spp., probably through horizontal transmission between species and vertical by some successful clones.

642. In Vitro Activity of Cefiderocol and Comparator Agents Against Molecularly Characterized Enterobacterales Clinical Isolates Causing Infection in United States Hospitals (2020-2021)

Abstract Background Cefiderocol (CFDC) is a siderophore cephalosporin that hijacks the Gram-negative bacteria iron transport system to facilitate cell entry and reach its target. CFDC remains stable to hydrolysis in the presence of serine β-lactamases (ESBLs, KPC, and OXA-type carbapenemases) and metallo-β-lactamases (MBL). CFDC and comparator activities were analyzed against Enterobacterales (ENT), including molecularly characterized isolates, as part of the SENTRY Antimicrobial Surveillance Program in the USA. Methods 8,328 ENT were collected from 32 sites in 2020-2021. Susceptibility testing was performed by broth microdilution. CFDC testing used iron-depleted media. CLSI breakpoints were used. E. coli, K. pneumoniae, and P. mirabilis with ceftriaxone, ceftazidime, or aztreonam MIC ≥2 μg/mL, and any ENT displaying MIC ≥2 μg/mL for imipenem (excluded for P. mirabilis, P. penneri, and indole-positive Proteeae) or meropenem (MER), were subjected to genome sequencing and screening of β-lactamase genes. Results In general, CFDC (≥ 99.9% susceptible [S]), imipenem-relebactam (IMR; 99.4-100%S), meropenem-vaborbactam (MEV; 100%S), and ceftazidime-avibactam (CZA; 100%S) were active against carbapenem-susceptible ENT that carried ESBL and/or AmpC genes (Table). CFDC (MIC50/90, 0.5/4 μg/mL; 98.4%S) and CZA (MIC50/90, 1/8 μg/mL; 91.2%S) were the most active agents against carbapenem-nonS isolates, whereas IMR (MIC50/90, 0.25/4 μg/mL; 81.6%S) and MEV (MIC50/90, 0.12/8 μg/mL; 86.4%S) had suboptimal activity. CFDC (MIC50/90, 0.5/2 μg/mL), IMR (MIC50/90, 0.12/0.5 μg/mL), MEV (MIC50/90, 0.03/0.5 μg/mL), and CZA (MIC50/90, 1/2 μg/mL) were active (100%S) against the KPC subset. CFDC (MIC, 0.5-4 μg/mL; 100%S) was also active against ENT carrying MBL genes, whereas CFDC (MIC, 0.5-2 μg/mL; 100%S) and CZA (1-4 μg/mL; 100%S) were active against isolates carrying blaOXA-48-like. Conclusion CFDC activity was consistent, regardless of phenotypes or genotypes, including against isolates carrying carbapenemase genes other than blaKPC, where approved β-lactam/β-lactamase inhibitor combinations showed limited activity. These data reinforce CFDC as an important option for the treatment of infections caused by ENT and resistant subsets. Disclosures Rodrigo E. Mendes, PhD, AbbVie: Grant/Research Support|Cidara: Grant/Research Support|GSK: Grant/Research Support|Melinta: Grant/Research Support|Nabriva Therapeutics: Grant/Research Support|Office for Assistant Secretary of Defense for Health Affairs: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support|Spero Therapeutics: Grant/Research Support John H. Kimbrough, PhD, AbbVie: Grant/Research Support|GSK: Grant/Research Support Valerie Kantro, BA, AbbVie: Grant/Research Support|GSK: Grant/Research Support|Melinta: Grant/Research Support|Shionogi: Grant/Research Support Dee Shortridge, PhD, AbbVie: Grant/Research Support|JMI Laboratory: Employee|Melinta: Grant/Research Support|Menarini: Grant/Research Support|Shionogi: Grant/Research Support Helio S. Sader, MD, PhD, AbbVie: Grant/Research Support|Cidara: Grant/Research Support|Melinta: Grant/Research Support|Nabriva Therapeutics: Grant/Research Support|Pfizer: Grant/Research Support Jennifer M. Streit, BS, MT(ASCP), Cidara: Grant/Research Support|GSK: Grant/Research Support|Melinta: Grant/Research Support|Shionogi: Grant/Research Support Mariana Castanheira, PhD, AbbVie: Grant/Research Support|Cidara: Grant/Research Support|GSK: Grant/Research Support|Melinta: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support.

Mechanisms involved in resistance to carbapenems among Acinetobacter baumannii isolates recovered in Brazil: A systematic review and meta-analysis

Introduction: Infections caused by carbapenem-resistant Acinetobacter baumannii(CRAB) is a health problem due to the limited therapeutic options available. This study was carried out to evaluate the main mechanisms of resistance of carbapenems in CRAB in the last 10 years in Brazil and to describe the susceptibility profile to tigecycline and polymyxins in these isolates. Material and methods: A systematic review was carried out according to Prisma in PUBMED/MEDLINE, Scopus, SciELO, Biblioteca Virtual de Saúde (BVS) and Cochrane Library. Data regarding enzyme resistance to carbapenems were evaluated by meta-analysis according to the random effect. Results: 21 articles were selected according to inclusion and exclu-sion criteria that evaluated 1096 CRAB. Most of the studies were carried out in the southern (33.3 %) and southeast (23.8 %) regions of Brazil (33.3 %) and in 2016 and 2018. According to the meta-analyzes, OXA-type carbapenemase was the main mechanism involved in the low susceptibility to carbapenems in CRAB (98%; 95% CI: 0.91, 0.99; I² = 95%), with blaOXA-23-like(91 %; 95 % CI: 0.76; 0.97; I² = 97 %) or blaOXA-51-like/ ISAba1 (84 %; 95 % CI: 0.15, 0.99; I² = 98 %) genes, followed by metallo-β-lactamases (MBL) (12 %, 95 % CI: 0.09, 0.15, I² = 99 %) and Klebsiella pneumoniae carbapenemase (KPC) (6 %, 95 % CI: 0.04; 0.08; I² = 87 %). Conclu-sion: The included studies showed that susceptibility to colistin (99 %) and tigecy-cline (93 %) remains high and was not affected by carbapenem resistance.

In-vitro Activity of Ceftazidime-Avibactam Against Carbapenem-Resistant K. pneumoniae in a Tertiary-Care Center in Al-Ahsa, KSA

Abstract Introduction/Objective Carbapenem-resistant Enterobacteriaceae (CRE) represents an urgent global threat. Klebsiella pneumoniae is a common cause of various clinical infections showing increased rates of resistance. Carbapenem-resistant Klebsiella pneumoniae (CR-KP) is often multi-drug resistant and sometimes becomes pan-drug resistant causing serious infections with substantial morbidity, mortality and cost. Ceftazidime-avibactam (CZA) is considered to be a good alternative to standard CRE therapy. In our region, CRE is mostly due to OXA-type carbapenemases which are inhibited by CZA, however, metallo-beta-lactamases (MBLs) are being increasingly reported and against which CZA is inactive. The aim of this study is to determine the activity of CZA against CRE-KP isolated in our hospital. Methods/Case Report Single-center, prospective study on consecutive non-duplicate CRE-KP isolates recovered from various clinical specimens in 2020 and 2021. BD Phoenix® system was used for initial Identification and susceptibility testing. E-test was done to confirm susceptibility and determine the minimum inhibitory concentration (MIC) for CZA. The standards of the Clinical and Laboratory Standards Institute were followed. Results (if a Case Study enter NA) 95 CRE-KP isolates were collected. CRE-KP was mostly isolated from: Respiratory samples: 36% (n=34), bedsores: 28% (n=27), urine: 23% (n=22) and 11% (10 isolates) were retrieved from blood cultures. 65% of patients were admitted to the intensive care unit (ICU), 13% were in long-term care wards and 13% were admitted for management of infected bedsores. 88 isolates were susceptible to CZA (93%) with MIC50= 1.5 μg/mL and MIC90= 4.0 μg/mL. 26 isolates (27%) were sensitive only to CZA. Susceptibility to tigecycline was 54%, amikacin 18% and gentamicin 17%. Other antimicrocbials including ceftolozane-tazobactam were basically ineffective. Conclusion Ceftazidime-avibactam shows excellent in-vitro activity against CR-KP isolates tested in this study. Further clinical studies on treatment efficacy and emergence of resistance are needed. Moreover, with the recent increase in reported MBLs-mediated resistance in our region, infection control measures, resistance-surveillance programs, and molecular testing may prove essential in the fight against carbapenem-resistant Enterobacteriaceae.

Molecular Detection of OXA-type Carbapenemases among Acinetobacter baumannii Isolated from Burn Patients and Hospital Environments

Background:Acinetobacter baumanniiis known as one of the major causes of nosocomial infections, especially in intensive care units and burn patients. The emergence of antimicrobial resistance in burn wound bacterial pathogens is a severe health crisis. Detection of carbapenem resistance and genetic elements inA. baumanniiassociated with burn patients and hospital environments play a key role in the control and alerting in clinical settings.Purpose:In this study, the prevalence of OXA-type carbapenemases was investigated inA. baumanniistrains isolated from burn patients and from a hospital environment in Tehran, 2021.Methods:A total of 85 non-duplicateA. baumanniiisolates (53 from various surfaces of the hospital environment and 32 from burn patients) were recovered in the Burns Hospital in Tehran. TheA. baumanniiisolates were screened for antibiotic susceptibility and the presence of the most common OXA-type carbapenemase genes.Results:A. baumanniiwas isolated from 38.5% of hospital patient burn wounds and 22.1% of surfaces, including burn units (15.6%) and intensive care units (52.4%). Antibiotic susceptibility results showed that (100%) of burn patient isolates were resistant to imipenem, while (100%) of ICU isolates and (96.8%) of burn isolates were resistant to imipenem. All clinical isolates were identified as MDR and XDR, whereas all (100%) and 98.1% of environmental isolates were identified as MDR and XDR, respectively. All studiedA. baumanniiisolates carriedblaOXA-51-likegene. Moreover, 50 (94.3%) and 49 (92.5%) of environmental isolates, 32 (100%) and 30 (93.7%) of burn patient isolate harboredblaOXA-23-likeandblaOXA-24/40–likegenes, respectively. None of the isolates carried theblaOXA-58orblaOXA-143genes and all isolates had at least 2 OXA-type carbapenemase genes.Conclusion:Our results suggest that surfaces in the hospital environment, particularly in ICUs, are contaminated with MDR or XDRA. baumanniistrains. They may be considered a potential reservoir for the colonization of hospital patients. In addition, OXA-type carbapenemases, including OXA-23-like and OXA-24/40-like, appear to be one of the major mechanisms of carbapenem resistance in the clinical and environmentalA. baumanniistrains.

Molecular Epidemiology of Carbapenem-Resistant Acinetobacter baumannii in the United States, 2013-2017.

Healthcare-associated carbapenem-resistant Acinetobacter baumannii (CRAB) infections are a serious threat associated with global epidemic clones and a variety of carbapenemase gene classes. In this study, we describe the molecular epidemiology, including whole-genome sequencing analysis and antimicrobial susceptibility profiles of 92 selected, nonredundant CRAB collected through public health efforts in the United States from 2013 to 2017. Among the 92 isolates, the Oxford (OX) multilocus sequence typing scheme identified 30 sequence types (STs); the majority of isolates (n = 59, 64%) represented STs belonging to the international clonal complex 92 (CC92OX). Among these, ST208OX (n = 21) and ST281OX (n = 20) were the most common. All isolates carried an OXA-type carbapenemase gene, comprising 20 alleles. Ninety isolates (98%) encoded an intrinsic OXA-51-like enzyme; 67 (73%) harbored an additional acquired blaOXA gene, most commonly blaOXA-23 (n = 45; 49%). Compared with isolates harboring only intrinsic oxacillinase genes, acquired blaOXA gene presence was associated with higher prevalence of resistance and a higher median minimum inhibitory concentration to the carbapenem imipenem (64 μg/mL vs. 8 μg/mL), and antibiotics from other drug classes, including penicillin, aminoglycosides, cephalosporins, and polymyxins. These data illustrate the wide distribution of CC92OX and high prevalence of acquired blaOXA carbapenemase genes among CRAB in the United States.

Molecular characterization and genetic diversity of multidrug- and extensively drug-resistant A. baumannii clinical isolates

ObjectiveThe increasing prevalence of multi-drug resistant (MDR) strains is now a serious menace for public health. The purpose of the study is to investigate the relationship between the variation of carbapenemases and antibiotic resistance profile among A. baumannii strains isolated from Tabriz, North-west Iran. MethodsA total of 127 A. baumannii isolates were obtained from two teaching hospitals in Tabriz, North-west Iran. Multiplex PCR was performed for the detection of carbapenemase-encoding genes. Furthermore, the genetic relationship of isolates was investigated by the enterobacterial repetitive intragenic consensus (ERIC)-PCR technique. ResultsAll isolates were resistant to carbapenem based on resistance to meropenem and imipenem. The frequency of multidrug-resistant (MDR) and extensively drug-resistant (XDR) was equal to 74.80% and 33.07% respectively. The most prevalent of MDR and XDR was related to patients up to 50 years (p < 0.05). The blaOXA-23-like genes were the most predominant among tested isolates 82 (64.5%), followed by blaOXA-143-like, 54 (42.51%); blaOXA-72, 39 (30.7%). None of the isolates were positive for the blaOXA-58-like gene. There was a significant relationship between the presence of the blaOXA-23 gene and the frequency of XDR strains (p < 0.01). Based on ERIC-PCR, 88 isolates were clustered into seven groups, while the remaining 21 were as single isolates. Most of the MDR isolates were related to B and C clusters (p < 0.05). The frequency of OXA-143 and OXA-72 was significantly high in A and B clusters (p < 0.05). This is the first report of the high incidence of blaOXA-143 and blaOXA-72 positive A. baumannii strains in Iran. The genetic relatedness of A. baumannii isolates was high, indicating cross-transmission within hospitalized patients. ConclusionA high prevalence of MDR and XDR A. baumannii strains with new resistance mechanisms was observed in our region. The incidence rate of OXA-type carbapenemases was different in the clusters classified by ERIC -PCR typing.

1232. In Vitro Activity of Cefiderocol and Comparator Agents against Molecularly characterized Carbapenem-resistant Enterobacterales Clinical Isolates Causing Infection in United States Hospitals (2020)

1232. <i>In Vitro</i> Activity of Cefiderocol and Comparator Agents against Molecularly characterized Carbapenem-resistant <i>Enterobacterales</i> Clinical Isolates Causing Infection in United States Hospitals (2020)

Molecular Detection of blaOXA -type Carbapenemase Genes and Antimicrobial Resistance Patterns among Clinical Isolates of Acinetobacter baumannii.

Acinetobacter baumannii is a bacterium found in most places, especially in clinics and hospitals, and an important agent of nosocomial infections. The presence of class D enzymes such as OXA-type carbapenemases in A. baumannii is proven to have a key function in resistance to carbapenem. The aim of the current study is to determine the blaOXA -type carbapenemase genes and antimicrobial resistance among clinically isolated samples of A. baumannii. We assessed 100 clinically isolated specimens of A. baumannii from patients in intensive care units of educational hospitals of Hamadan, West of Iran. The A. baumannii isolates' susceptibility to antibiotics was performed employing disk diffusion method. Multiplex polymerase chain reaction was used to identify the bla OXA-24-like , bla OXA-23-like , bla OXA-58-like , and bla OXA-51-like genes. The bla OXA-23-like , bla OXA-24-like , and bla OXA-58-like genes' prevalence were found to be 84, 58, and 3%, respectively. The highest coexistence of the genes was for bla OXA-51/23 (84%) followed by bla OXA-51/24-like (58%). The bla OXA-51/23- like pattern of genes is a sort of dominant gene in resistance in A. baumannii from Hamadan hospitals. The highest resistance to piperacillin (83%) and ciprofloxacin (81%) has been observed in positive isolates of bla OXA-23-like . The A. baumannii isolates with bla OXA-58-like genes did not show much resistance to antibiotics. Based on the results of the phylogenetic tree analysis, all isolates have shown a high degree of similarity. This study showed the high frequency of OXA -type carbapenemase genes among A. baumannii isolates from Hamadan hospitals, Iran. Thus, applying an appropriate strategy to limit the spreading of these strains and also performing new treatment regimens are necessary.

Comparative study of phenotypic-based detection assays for carbapenemase-producing Acinetobacter baumannii with a proposed algorithm in resource-limited settings

The increasing incidence of carbapenem resistance in Acinetobacter baumannii is a critical concern worldwide owing to the limitations of therapeutic alternatives. The most important carbapenem resistance mechanism for A. baumannii is the enzymatic hydrolysis mediated by carbapenemases, mostly OXA-type carbapenemases (class D) and, to a lesser extent, metallo-β-lactamases (class B). Therefore, early and accurate detection of carbapenemase-producing A. baumannii is required to achieve the therapeutic efficacy of such infections. Many methods for carbapenemase detection have been proposed as effective tests for A. baumannii; however, none of them are officially recommended. In this study, three carbapenemase detection methods, namely, CarbaAcineto NP test, modified carbapenem inactivation method (mCIM), and simplified carbapenem inactivation method (sCIM) were evaluated for phenotypic detection of clinically isolated A. baumannii. The MICs of imipenem, meropenem, and doripenem were determined for 123 clinically isolated A. baumannii strains before performing three phenotypic detections. The overall sensitivity and specificity values were 89.09%/100% for the carbAcineto NP test, 71.82%/100% for sCIM, and 32.73%/33.13% for mCIM. CarbAcineto NP test and sCIM performed excellently (100% sensitivity) when both Class B and Class D carbapenemases were present in the same isolate. Based on the results, the combined detection method of sCIM and CarbAcineto NP test was proposed to detect carbapenemase-producing A. baumannii rather than a single assay, significantly increasing the sensitivity of detection to 98.18%. The proposed algorithm was more reliable and cost-effective than the CarbAcineto NP test alone. It can be easily applied in routine microbiology laboratories for developing countries with limited resources.

Multiplex lateral flow immunochromatographic assay is an effective method to detect carbapenemases without risk of OXA-48-like cross reactivity

BackgroundIt is essential to detect carriers of carbapenemase-producing Enterobacterales in order to implement infection control measures. The objectives of this study was to evaluate the NG-Test® CARBA 5 (CARBA 5) assay for detection of five carbapenemases and to assess the cross reactivity of other OXA-type carbapenemases with the OXA-48-like specific antibodies.MethodsA total of 197 Enterobacterales isolates were tested. To evaluate the cross reactivity, 73 carbapenem-resistant A. baumannii, harboring OXA-type variants, were tested. Polymerase chain reaction (PCR) served as gold standard for carbapenemase identification.ResultsExcellent agreement was found between PCR and CARBA 5, for all but one isolate. The single false positive result (a blaSME positive S. marcescens isolate) was incorrectly positive for blaOXA-48 by CARBA 5. No cross reactivity was observed. The sensitivity and specificity were 100.0% and 98.0%, respectively.ConclusionsThe CARBA 5 assay is highly sensitive and specific and is recommended as a tool for the detection of the main carbapenemases of interest in clinical microbiology laboratories.