Carbapenem-susceptible Isolates Research Articles

Ampicillin-Sulbactam for Carbapenem-Susceptible Acinetobacter baumannii Pneumonia: A Case for High-Dose, Continuous Infusion Dosing Strategy in the Trauma ICU.

Background: The optimal ampicillin-sulbactam dosing regimen for carbapenem-susceptible Acinetobacter baumannii isolates in critically ill trauma patients has not been clearly defined. One strategy to provide the adequate sulbactam dose includes high-dose continuous infusion. Case(s) Description: We present three cases of critically ill trauma patients with augmented renal clearance treated with high-dose ampicillin-sulbactam through an intravenous continuous infusion for ventilator-associated pneumonia. All A. baumannii isolates were susceptible to sulbactam with low minimum inhibitory concentrations. All achieved clinical cure at the end of therapy and no recurrent pneumonia was noted. No clinically substantial adverse effect attributable to ampicillin-sulbactam therapy occurred. Discussion: There is limited evidence to endorse high-dose, continuous infusion ampicillin-sulbactam for treatment of infections caused by carbapenem-susceptible A. baumannii. This report presents three critically ill trauma patients with augmented renal clearance that achieved positive clinical outcomes with higher doses of ampicillin-sulbactam administered through a continuous infusion.

Activity of propyl-propane-thiosulfinate and propyl-propane-thiosulfonate against carbapenem-resistant Gram-negative bacteria.

Organosulfur compounds derived from plants of the Allium genus, such as propyl-propane-thiosulfinate (PTS) and propyl-propane-thiosulfonate (PTSO), have been proposed as an alternative in antibiotic resistance. The aim of this study was to compare the activity of these substances with other antibiotics against clinical isolates of carbapenem-resistant (CAR-R) and carbapenem-susceptible (CAR-S) Gram-negative bacteria. A total of 126 clinical isolates of CAR-R and 155 CAR-S bacteria were selected, including Enterobacterales, A. baumannii and P. aeruginosa. The antibiotic susceptibility of all isolates was assessed using the microdilution and Kirby-Bauer methods for PTS, PTSO, amoxicillin/clavulanate, piperacillin/tazobactam, cefotaxime, ceftazidime, cefepime, imipenem, ciprofloxacin, and amikacin. Both PTS and PTSO demonstrated in vitro bactericidal activity against CAR-R Enterobacteriaceae and A. baumannii, with no significant difference in activity compared to their response against CAR-S isolates. However, both compounds were less active against P. aeruginosa than against any of the other bacteria, regardless of their resistance to carbapenems. In all cases, the minimum inhibitory concentration values of PTSO were significantly lower than those of PTS. These findings offer valuable information about the potential antibacterial use of these substances, particularly against infections that currently have limited therapeutic options.

713. Prevalence of Microbicide Resistance Genes in Clinical Isolates of Acinetobacter baumannii

Abstract Background The persistence of Acinetobacter on different surfaces and the continuous exposure of bacteria to disinfectants such as quaternary ammonium compounds (QACs) in the healthcare environment have led to microbicide tolerance. Acinetobacter baumannii have also rapidly acquired carbapenem resistance. Here we determined the prevalence of microbicide resistance genes in carbapenem susceptible and resistant clinical isolates of Acinetobacter. Methods All clinical isolates were collected from two separate hospitals in Detroit between 2017-2021. Following DNA isolation using Qiagen kit, Nextera Flex kit was used for library preparation of Acinetobacter clinical isolates. Whole genome sequencing (WGS) was performed via Illumina NextSeq 550 using the prepared DNA library. The FASTQ files from the sequencing run were then subjected to bioinformatic analysis with Bionumerics software v7.6. ResFinder was used for determination of presence or absence of QAC resistant genes and results were tabulated by Carbapenem-Resistant Acinetobacter baumannii (CRAb) or Carbapenem-Susceptible Acinetobacter baumannii (CSAb) with or without the QAC resistant genes. Results Out of the 139 Acinetobacter patient isolates, 70/139 (50.4%) were CRAb containing carbapenemase blaOXA-23 and 69/139 (49.6%) belonged to CSAb (Table 1). Figure 1. shows the prevalence of antimicrobial resistance (AMR) genes in CRAb and CSAb isolates with qacE genes. For CRAb isolates, 56% had qacE genes while 39% of CSAb had qacE genes. About 42% of CRAb isolates were multi-drug resistant (MDR), indicating a prevalence of qacE genes among the MDR isolates. Table 2 shows the presence of qacE genes by sequence type (ST). In the ST2 (Pasteur) and ST406 (Pasteur) strains, qacE gene was mainly present. Interestingly, most of the Acinetobacter isolates that belong to ST2 (ST195 and ST281, Oxford) are CRAb with qacE gene.Figure 1:Different AMR genes and qacE in both CRAb and CSAb isolates Conclusion Clinical isolates in our study had an even distribution of both CRAb and CSAb. The presence of qacE gene was more prevalent in the CRAb isolates compared to the CSAb isolates. While different STs harbored the qacE gene, the prevalence of qacE gene was highest in ST2 among all isolates. Future studies are needed to determine the reduced susceptibility to other commonly used hospital disinfectants. Disclosures Keith S. Kaye, MD, MPH, Abbvie: Advisor/Consultant|Abbvie: Honoraria|Entasis: Advisor/Consultant|Entasis: Honoraria|GSK: Advisor/Consultant|GSK: Honoraria|Merck: Advisor/Consultant|Merck: Honoraria|Shionogi: Advisor/Consultant|Shionogi: Honoraria|VenatoRx: Advisor/Consultant|VenatoRx: Honoraria

Performance of Carbapenemase Nordmann-Poirel, Modified Carbapenem Inactivation, and EDTA Carbapenem Inactivation Methods for Detecting Carbapenem-Resistant Klebsiella pneumoniae Isolates.

Infections caused by carbapenem-resistant Klebsiella pneumoniae (CRKP) are a major threat to public health. Timely detection of CRKP will help treat patients with appropriate antibiotics. This study aimed to evaluate the performance of the carbapenemase Nordmann-Poirel (CarbaNP), modified carbapenem inactivation (mCIM), and EDTA carbapenem inactivation (eCIM) methods for the detection of CRKP. We compared the results of the three assays with that of real-time PCR. In total, 195 K. pneumoniae isolates, including 150 carbapenem-resistant and 45 carbapenem-susceptible isolates, were investigated. Carbapenem-resistance genes, such as blaKPC, blaNDM, blaVIM, blaIMP, and blaOXA-48-like, were identified using real-time PCR. Among the 150 CRKP isolates, 94 (62.7%) were positive for blaNDM, 29 (19.3%) were positive for blaOXA-48-like, and 27 (18%) were positive for both blaNDM and blaOXA-48-like. For detecting CRKP isolates, CarbaNP, mCIM, and eCIM showed 96.0%, 95.4%, and 96.7% sensitivity, respectively, and all three methods showed 100% specificity. All three phenotypic confirmatory tests are reliable for identifying CRKP, easy to perform, cost-effective, and can be incorporated with routine antibiotic susceptibility testing.

Comparison of prevalence, resistance, biofilm-forming ability and virulence between carbapenem-non-susceptible and carbepenem-susceptible Enterobacter cloacae complex in clusters

This study aimed to explore the differences of prevalence, resistance, biofilm, and virulence between carbapenem nonsusceptible and susceptible Enterobacter cloacae complex (ECC) in different clusters. Ninety-one carbapenem nonsusceptible isolates and an equal number of susceptible isolates as well as their clinical information were collected from a university teaching hospital in China. The strains were divided into different clusters according to the analysis based on hsp60. Agar dilution method was used to determine the MICs of common antibiotics. Crystal violet assay was used to measure biofilm-forming ability. Galleria mellonella infection model and PCR of virulence genes were used to evaluate the virulence. The isolates were divided into 12 clusters based on the hsp60 analysis. Cluster VIII accounted for a predominant and higher proportion of carbapenem nonsusceptible isolates than the other clusters. The same clusters exhibited different resistance rates in carbapenem nonsusceptible and susceptible isolates. Moreover, carbapenem nonsusceptible isolates carried fewer virulence genes than susceptible isolates, and cluster II in carbapenem nonsusceptible isolates didn't carry the detected virulence genes. The virulence of clusters I, III, VIII, and IX was significantly different between the nonsusceptible and susceptible isolates, as evaluated using the Galleria mellonella infection model. Cluster VIII accounted for a predominant and higher proportion as well as higher resistance, biofilm formation ability, and pathogenicity in carbapenem nonsusceptible isolates than the other clusters. This finding indicated the necessity to identify subgroups of ECC and provide better advice and guidance for the use of carbapenem.

Epidemiology and mortality outcome of carbapenem- and colistin-resistant Klebsiella pneumoniae, Escherichia coli, Acinetobacter baumannii, and Pseudomonas aeruginosa bloodstream infections

BackgroundBloodstream infections caused by carbapenem-resistant Gram-negative bacteria represent a major therapeutic challenge to clinicians worldwide. This study examined the epidemiology of carbapenem and colistin resistance in Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa, and Acinetobacter baumannii blood isolates in an academic institution in Oman. MethodsAdult patients with bloodstream infections caused by Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa, and Acinetobacter baumannii, between January 1, 2017, and December 31, 2020, were identified. Rates of carbapenem resistance, carbapenem-colistin dual resistance, and 30-day all-cause mortality were examined. Results585 non-repeat bloodstream infections due to Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa, and Acinetobacter baumannii were identified during the study period. OXA-48 was the most prevalent carbapenemase gene in carbapenem-resistant K. pneumoniae blood isolates. Carbapenem resistance was observed in 160 (27.7%) of blood isolates, with 131 (81.9%) of these being healthcare-onset cases. Carbapenem resistance was highest in Acinetobacter baumannii (80.4%), followed by Klebsiella pneumoniae (46.4%), and Pseudomonas aeruginosa (29.9%). Sixteen (13.4%) of the carbapenem-resistant blood isolates were found to be colistin resistant. Thirty-day all-cause mortality was 68.1% in patients with bloodstream infections caused by carbapenem-resistant isolates, versus 21.3% in patients with bloodstream infections caused by carbapenem-susceptible isolates. ConclusionThe prevalence of carbapenem resistance and carbapenem-colistin dual resistance in Gram-negative blood culture isolates from patients with bloodstream infections is unacceptably high. Patients with bloodstream infections due to carbapenem-resistant isolates had substantially higher mortality.

Increasing trends of colistin resistance in patients at high-risk of carbapenem-resistant Enterobacteriaceae

Introduction Occurrence of colistin-resistant Enterobacteriaceae in response to the unregulated use of this antibiotic has been documented. This study reports an investigation of colistin resistance rates among carbapenem-resistant enterobacterial clinical isolates. Methods A total of 196 multidrug-resistant Enterobacteriaceae isolates (Klebsiella pneumoniae (n = 100), Escherichia coli (n = 89) and Enterobacter cloacae (n = 7) were selected from Gram-negative isolates over one year. Susceptibility to antimicrobials was determined using Vitek2. Broth microdilution method was used to detect colistin antimicrobial susceptibility. Identification of ESBL and carbapenemases were both done phenotypically and by PCR. Results All the studied isolates showed multidrug-resistant phenotypes with 51.5% resistance to carbapenems (meropenem, imipenem). Very low resistance rates towards tigecycline (n = 9) 4.6% were found. Thirty-nine isolates (19.9%) showed reduced susceptibility to colistin among the MDR isolates. Sixty-four isolates (32.7%) were ESBL producers. Hundred isolates (51%) were carbapenemase producers using Carba NP test. The PCR amplification results revealed that 40 isolates (20%) harboured NDM-1 and 40 isolates contained OXA-48-like gene. Coexistence of both (NDM-1 and OXA-48-like) was observed in nine (4.59%) isolates. A Statistically significant relationship was observed between carbapenem resistance and each of the followings; OXA-48 producers (p= .009), amikacin resistance (p = .000), gentamicin resistance (p = .032), tobramycin resistance (p = .000), and tigecycline resistance (p-value ≤ .001). A statistical significance was detected between ESBL-producing isolates and carbapenem susceptible isolates ESBL producers with p = 0.000. Conclusion An alarming sign is the increasing colistin resistance rates among carbapenem-resistant isolates. Aminoglycosides are still a therapeutic option to decrease the use of colistin and avoid further development of resistance. KEY MESSAGES High rates of colistin resistance among carbapenem-resistant Enterobacteriaceae. The choice of antibiotic is significantly associated with the clinical site of infection. Aminoglycosides are offered choices for treating multiple drug-resistant Enterobacteriaceae to preserve the colistin and carbapenems.

Molecular patterns of clinically important fluoroquinolone resistance in multidrug-resistant Klebsiella pneumoniae isolates during nosocomial outbreaks in Shanghai, PR China.

Introduction. The soaring resistance of Klebsiella pneumoniae to fluoroquinolones in PR China has substantially limited the application of these antimicrobials, especially in those clinical settings that were threatened by persistent carbapenem-resistant K. pneumoniae (CRKP), necessitating strict implementation of antimicrobial stewardship and active enhanced surveillance of infection control.Hypothesis. There is interplay between plasmid-mediated quinolone resistance (PMQR) determinants and quinolone resistance-determining region (QRDR) mutations during the acquisition of a clinically important fluoroquinolone resistance (CI-FR) profile in multidrug-resistant K. pneumoniae (MDR-KP) isolates.Aim. To investigate the high-risk CRKP clones responsible for nosocomial spread and analyse the molecular patterns of CI-FR in MDR-KP isolates in a tertiary hospital in Shanghai, PR China.Methodology. A total of 34 isolates, including 30 CRKPs, were molecularly characterized. Investigations included antimicrobial susceptibility tests, multilocus sequence typing (MLST) and wzi genotyping, PCR sequencing and phylogenetic analysis for resistance-associated genes, and clinical information retrieval from medical records.Results. Two high-risk CRKP clones, ST11-wzi64 and ST15-wzi19/wzi24, were identified as being responsible for nosocomial outbreaks in the intensive care unit (ICU) and the neurosurgery department, potentially by the respiratory route. QRDR mutations of both gyrA and parC were detected in isolates of ST15 (S83F/D87A/S80I), ST11 (S83I/D87G/S80I) and ST218 (D87A/S80I), respectively. The PMQR genes, qnrS1, aac(6')-Ib-cr and oqxAB, were present in 32 (94.1 %) of the isolates alone or in combination, co-occurring with genes (bla) encoding β-lactamases, 16S rRNA methylases and putrescine ABC permeases. AcrR, an AcrAB transcriptional repressor, was insertion-inactivated by the IS5-like element in ST11 isolates. The encoding sequences of OmpK35 and OmpK36 genes were associated with specific STs and wzi alleles. ST11, ST15-wzi19 and ST218 isolates had frameshift disruptions in OmpK35 and specific GD insertions at position 134-135 in OmpK36. The 27 isolates with clinically important ciprofloxacin resistance (MICs ≥2 mg l-1) included 25 isolates (ST15, ST11, ST218) with multiple QRDR mutations, plus 1 with only 2 PMQR determinants (ST290-wzi21) and another with an unknown resistance mechanism (ST65-wzi72). Ciprofloxacin-susceptible isolates maintained intact ompK36 genes, including two CRKPs each with ST13-wzi74 (KPC-2 and NDM-1 coproducers) and ST65-wzi72, plus carbapenem-susceptible isolates (ST15-wzi24, ST65-wzi72, ST107-wzi173).Conclusions. Under selective pressures, the accumulation of mutations of three types (QRDR, acrR, ompK36) and the acquisition of resistance-conferring genes have continuously contributed to CI-FR in MDR-KP isolates.

Comparison of Virulence between Two Main Clones (ST11 and ST307) of Klebsiella pneumoniae Isolates from South Korea.

In this study, we investigate the characteristics of two main clones of carbapenemase-producing Klebsiella pneumoniae isolates from South Korea, ST11 and ST307, including carbapenem-susceptible isolates. Antibiotic susceptibility, serotype or wzi allelic type, the presence of virulence genes, and virulence with respect to serum resistance and macrophage internalization were determined for ST11 and ST307 isolates. ST11 isolates had a wide range of characteristics, including serotype and virulence, compared with those of homogeneous ST307 isolates. The wzi14 or K14 type had higher virulence than that of other serotypes among the ST11 isolates, and the homogeneous ST307 isolates showed similar virulence level as that of the wzi14-type ST11 isolates. Our data suggest that it is necessary to monitor not only the introduction and spread of a specific clone, but also its detailed serotype.

Detection and Characterization of Carbapenemases in Enterobacterales With a New Rapid and Simplified Carbapenemase Detection Method Called rsCDM.

ObjectiveThis study aimed to develop a new rapid and simplified carbapenemase detection method (rsCDM) for detection and characterization of carbapenemase with 3-aminophenylboronic acid (APBA), ethylenediaminetetraacetic acid (EDTA), and cloxacillin (CLO) β-lactamase inhibitors.MethodsA panel of 182 carbapenem-resistant Enterobacterales (CRE) strains with blaKPC (88), blaNDM (60), blaIMP (10), blaVIM (3), blaOXA-181 (5), blaKPC, and blaNDM (7), porin changes in combination with an extended-spectrum β-lactamase (ESBL) (3) or AmpC hyper-production (6) and 43 carbapenem-susceptible Enterobacterales isolates were used to evaluate the performance of rsCDM and EDTA-carbapenem inactivation method (eCIM). Carbapenemase class was determined with specific inhibitors at 4, 6, and 18 h by rsCDM, and the difference between imipenem (IMI) and meropenem (MEM) disks was simultaneously compared.ResultsThe sensitivity of rsCDM using IMI was 97.1% at the three time points, with a specificity of 100%, independent of the culture duration. Similar to IPM, MEM disk also showed high sensitivity (97.1%) and specificity (100%) at 6 h. And the sensitivity of eCIM was 95.4% and the specificity was 100%. Based on a decision algorithm, the characterization number of IMI and MEM in KPC-producing isolates was 88 vs. 87, metallo-β-lactamases (MBLs) was 73 vs. 72, KPC and NDM carbapenemase was 7 vs. 7 at 4 h, respectively. After 6 h, the category number changed insignificantly except for isolates with combined AmpC overproduction and porin changes, showing an increase in IMI (6) and MEM (2), and there was no difference in the results between 6 and 18 h for the two tablets. OXA-181-producing strains can’t be distinguished by rsCDM. For eCIM, the characterization number in KPC-, OXA- 181-, and MBLs-producing strains was 88, 5, and 72, but it failed to detect multi-enzyme-producing isolates (KPC and NDM).ConclusionrsCDM accurately discriminated carbapenemase within 4 h and could differentiate multi-enzyme (KPC and NDM) and AmpC in conjunction with porin changes strains. Hence, rsCDM represents a rapid, simple, easy readout, and accurate tool that can be used without any specialized equipment.

In Vitro Efficacy of Antibiotic Combinations with Carbapenems and Other Agents against Anaerobic Bacteria.

We investigated the in vitro efficacy of combinations of carbapenems with clindamycin (CLDM) and minocycline (MINO) against Bacteroides fragilis and Peptostreptococcus species. We selected the carbapenems imipenem, meropenem, panipenem, doripenem, and biapenem. To evaluate the antibiotic efficacy of these combination regimens, the fractional inhibitory concentration index (FICI) was calculated against clinical isolates. Consequently, combination regimens of each carbapenem with CLDM or MINO showed synergistic or additive effects against 83.3–100.0% and no antagonistic effects against P. anaerobius isolates. However, against the B. fragilis group (B. fragilis, B. thetaiotaomicron, and Parabacteroides distasonis), although the combination with other carbapenems and CLDM or MINO did not show remarkable synergistic effects, the combination regimen of IPM with CLDM or MINO indicated mainly additive antibiotic efficacies (FICIs: >0.5 to ≤1.0) to B. fragilis groups. Then, antagonistic effects were admitted in only 5.6% of B. fragilis groups. The effectiveness of antibiotic combination therapy against pathogenic anaerobes has remained unclear. Then, our results can provide new insights to explore the effective combination regimens against multidrug-resistant anaerobic bacteria as empirical and definitive therapies, while this study used only carbapenem susceptible isolates. Hence, further studies are needed to use highly antibiotic-resistant anaerobic isolates to carbapenems.

Computer Program for Detection and Analyzing the Porin-Mediated Antibiotic Resistance of Bacteria.

The aim of this work was to develop a new software tool for identifying gene mutations that determine the porin-mediated resistance to antibiotics in gram-negative bacteria and to demonstrate the functionality of this program by detecting porin-mediated resistance to carbapenems in clinical isolates of Pseudomonas aeruginosa.Materials and MethodsThe proposed algorithm is based on searching for a correspondence between the reference and the studied genes. When the sought nucleotide sequence is found in the analyzed genome, it is compared with the reference one and analyzed. The genomic analysis is then verified by comparing between the amino acid sequences encoded by the reference and studied genes. The genes of the susceptible P. aeruginosa ATCC 27853 strain were used as the reference nucleotide sequences encoding for porins (OprD, OpdD, and OpdP) involved in the transport of carbapenems into the bacterial cell. The complete genomes of clinical P. aeruginosa isolates from the PATRIC database 3.6.9 and our own collection were used to test the functionality of the proposed program. The analyzed isolates were phenotypically characterized according to the CLSI standard. The search for carbapenemase genes in the studied genomes of P. aeruginosa was carried out using the ResFinder 4.1.ResultsThe developed program for detecting the genetic determinants of non-plasmid antibiotic resistance made it possible to identify mutations of various types and significance in the porin genes of P. aeruginosa clinical isolates. These mutations led to modifications of the peptide structure of porin proteins. Single amino acid substitutions prevailed in the OpdD and OpdP porins of carbapenem-susceptible and carbapenem-resistant isolates. In the carbapenem-resistant strains, the gene encoding for OprD porin was found heavily modified, including insertions and/or deletions, which led to premature termination of porin synthesis. In several isolates resistant to meropenem, no mutations were detected in the gene encoding for OprD, which might be associated with alternative mechanisms of resistance to carbapenems.ConclusionThe proposed software product can become an effective tool for deciphering the molecular genetic mechanisms of bacterial chromosomal resistance to antibiotics. Testing the program revealed differences between the occurrences of mutations significant for carbapenem resistance in the oprD, opdD, and opdP genes.

LB16. Surveillance Rates of Cefiderocol Heteroresistance Correlate With All-cause Mortality in the APEKS-NP and CREDIBLE-CR Trials

BackgroundCefiderocol is a recently FDA approved, novel siderophore beta-lactam antibiotic. Conventional antimicrobial susceptibility testing (AST) suggests that a variety of Gram-negative pathogens, including carbapenem-resistant (CR) isolates, are overwhelmingly susceptible to cefiderocol.. This antibiotic performed well in the APEKS-NP trial for the treatment of nosocomial pneumonia caused largely by carbapenem susceptible isolates. However, in the CREDIBLE-CR trial involving exclusively CR Gram-negative bacteria, cefiderocol was associated with a higher rate of all-cause mortality. We hypothesized one explanation for these discrepant data might be undetected cefiderocol heteroresistance (HR).HR is a form of antibiotic resistance in which an isolate harbors a minority resistant subpopulation of cells co-existing with a majority susceptible population, and is often undetected by standard AST. Isolates exhibiting undetected HR, with as low as 1 in 1 million resistant cells, can cause treatment failure in in vivo models.MethodsWe quantified HR to cefiderocol by population analysis profile (PAP) of 161 Acinetobacter, 180 Klebsiella, and 108 Pseudomonas isolates collected in Georgia, USA.ResultsWe observed CR isolates exhibited a high frequency of HR, which was largely undetected by standard AST, and correlated with all-cause mortality in the CREDIBLE-CR study (Table). Carbapenem-susceptible isolates exhibited no or low rates of cefiderocol HR (Table). Cephalosporin-resistant bacteria mostly exhibited increased rates of cefiderocol HR, but below those of CR strains. These differences in rates of cefiderocol HR correlated with the mortality data from the APEKS-NP and CREDIBLE-CR trials, across the bacterial species tested (Table).Table: Surveillance rates of cefiderocol heteroresistance correlate with all-cause mortality in the APEKS-NP and CREDIBLE-CR trials ConclusionThese data suggest that the lower rates of cefiderocol HR in carbapenem-susceptible isolates that predominated the APEKS-NP trial may explain the enhanced efficacy of the drug in that study as compared to the CREDIBLE-CR trial. Importantly, the widespread, undetected cefiderocol HR observed among CR pathogens may explain the discordance between this drug’s excellent in vitro susceptibility profile and increased patient mortality in the CREDIBLE-CR trial.Disclosures All Authors: No reported disclosures

Risk factors and clinical impact of bacteremia due to carbapenem-nonsusceptible Enterobacteriaceae: A multicenter study in southern Taiwan.

The emergence of carbapenem-non-susceptible Enterobacteriaceae (CnSE) infections is a public health threat. This study investigated the risk factors and clinical impact of bacteremia due to CnSE. The study was conducted at three hospitals in southern Taiwan between January 1, 2017, and October 31, 2019. Only the first episode of CnSE bacteremia from each adult was included. For one episode of CnSE bacteremia, two subsequent bacteremic episodes due to carbapenem-susceptible Enterobacteriaceae isolates in each hospital were included as the controls. Among a total of 641 episodes of monomicrobial Enterobacteriaceae bacteremia were noted, 47 (7.3%) of which were of CnSE bacteremia. Ninety-four episodes of carbapenem-susceptible Enterobacteriaceae (CSE) bacteremia were selected as the controls for further analyses. In the multivariate analysis, hypertension (odds ratio [OR], 4.21; P=0.005), Pitt bacteremia score (OR, 1.61; P=0.002), and nosocomial bacteremia (OR, 3.30; P=0.01) were associated with carbapenem nonsusceptibility among Enterobacteriaceae bacteremia. The most abundant CnSE isolate was Klebsiella pneumoniae (91.5%), followed by Klebsiella oxytoca (6.4%) and Escherichia coli (2.1%). Patients with CnSE bacteremia had a higher overall in-hospital mortality rate than those with CSE bacteremia (53.2% vs. 23.4%, P=0.001). Moreover, in the multivariate analysis, the in-hospital mortality was significantly associated with higher Pitt bacteremia score (OR, 1.38; P=0.02) and marginally associated with CnSE infections (OR, 2.44; P=0.06). Among adults with Enterobacteriaceae bacteremia, carbapenem nonsusceptibility, male sex, and the presence of hypertension or chronic kidney disease indicate a poor prognosis during hospitalization.

Genetic Environment Surrounding blaOXA-55-like in Clinical Isolates of Shewanella algae Clade and Enhanced Expression of blaOXA-55-like in a Carbapenem-Resistant Isolate.

ABSTRACTAlthough Shewanella spp. are most frequently isolated from marine environments; more rarely, they have been implicated in human infections. Shewanella spp. are also recognized as the origin of genes for carbapenem-hydrolyzing class D β-lactamases. Due to the spread globally among Enterobacterales in recent years, risk assessments of both clinical and environmental Shewanella strains are urgently needed. In this study, we analyzed the whole-genome sequences of 10 clinical isolates and 13 environmental isolates of Shewanella spp. and compared them with those of Shewanella species strains registered in public databases. In addition, the levels of blaOXA-55-like transcription and β-lactamase activity of a carbapenem-resistant Shewanella algae isolate were compared with those of carbapenem-susceptible S. algae clade isolates. All clinical isolates were genetically identified as S. algae clade (S. algae, Shewanella chilikensis, and Shewanella carassii), whereas all but one of the environmental isolates were identified as various Shewanella spp. outside the S. algae clade. Although all isolates of the S. algae clade commonly possessed an approximately 12,500-bp genetic region harboring blaOXA-55-like, genetic structures outside this region were different among species. Among S. algae clade isolates, only one showed carbapenem resistance, and this isolate showed a high level of blaOXA-55-like transcription and β-lactamase activity. Although this study documented the importance of the S. algae clade in human infections and the relationship between enhanced production of OXA-55-like and resistance to carbapenems in S. algae, further studies are needed to elucidate the generalizability of these findings.IMPORTANCE Shewanella spp., which are known to carry chromosomally located blaOXA genes, have mainly been isolated from marine environments; however, they can also cause infections in humans. In this study, we compared the molecular characteristics of clinical isolates of Shewanella spp. with those originating from environmental sources. All 10 clinical isolates were genetically identified as members of the Shewanella algae clade (S. algae, S. chilikensis, and S. carassii); however, all but one of the 13 environmental isolates were identified as Shewanella species members outside the S. algae clade. Although all the S. algae clade isolates possessed an approximately 12,500-bp genetic region harboring blaOXA-55-like, only one isolate showed carbapenem resistance. The carbapenem-resistant isolate showed a high level of blaOXA-55-like transcription and β-lactamase activity compared with the carbapenem-susceptible isolates. To confirm the clinical significance and antimicrobial resistance mechanisms of the S. algae clade members, analysis involving more clinical isolates should be performed in the future.

Comparison of in vitro activities of plazomicin and other aminoglycosides against clinical isolates of Klebsiella pneumoniae and Escherichia coli.

To compare the in vitro activity of plazomicin and two older aminoglycosides (gentamicin and amikacin) against 180 isolates of Escherichia coli and Klebsiella pneumoniae, including subsets of 60 non-ESBL-producing, 60 ESBL-producing and 60 carbapenem-resistant (46 carrying blaOXA-48, 11 carrying blaNDM and 3 carrying blaOXA-48 and blaNDM) strains. MICs of plazomicin, gentamicin and amikacin were determined by a gradient diffusion method. Gentamicin and amikacin MICs were interpreted according to CLSI criteria and EUCAST breakpoint tables. Plazomicin MICs were interpreted using FDA-defined breakpoints. All non-ESBL-producing and ESBL-producing isolates were susceptible to plazomicin. The plazomicin susceptibility rate (71.7%) in carbapenem-resistant isolates was significantly higher than those observed for gentamicin (45%) and amikacin (56.7% and 51.7% according to CLSI and EUCAST breakpoints, respectively). Gentamicin, amikacin and plazomicin susceptibility rates (35.6% for gentamicin; 44.4% and 37.8% for amikacin according to CLSI and EUCAST breakpoints, respectively; 64.4% for plazomicin) in carbapenem-resistant K. pneumoniae were significantly lower than those observed for carbapenem-resistant E. coli isolates (73.3% for gentamicin; 93.3% for amikacin and plazomicin). Gentamicin, amikacin and plazomicin susceptibility rates for blaNDM-positive isolates were lower than those observed for blaOXA-48-positive isolates, but differences were not statistically significant. Among the isolates that were non-susceptible to both gentamicin and amikacin, the plazomicin susceptibility rate was less than 30%. Although plazomicin showed excellent in vitro activity against carbapenem-susceptible isolates, the plazomicin resistance rate increased to 35.6% among carbapenem-resistant K. pneumoniae and further increased to 45.5% among blaNDM-positive isolates.

Seasonality and weather dependance of Acinetobacter baumannii complex bloodstream infections in different climates in Brazil.

Recent studies report seasonality in healthcare-associated infections, especially those caused by Acinetobacter baumannii complex. We conducted an ecologic study aimed at analyzing the impact of seasons, weather parameters and climate control on the incidence and carbapenem-resistance in A. baumannii complex bloodstream infections (ABBSI) in hospitals from regions with different climates in Brazil. We studied monthly incidence rates (years 2006-2015) of ABBSI from hospitals in cities from different macro-regions in Brazil: Fortaleza (Ceará State, Northeast region), Goiânia (Goiás State, Middle-west) and Botucatu (São Paulo State, Southeast). Box-Jenkins models were fitted to assess seasonality, and the impact of weather parameters was analyzed in Poisson Regression models. Separate analyses were performed for carbapenem-resistant versus carbapenem-susceptible isolates, as well as for infections occurring in climate-controlled intensive care units (ICUs) versus non-climate-controlled wards. Seasonality was identified for ABSSI ICUs in the Hospitals from Botucatu and Goiânia. In the Botucatu hospital, where there was overall seasonality for both resistance groups, as well as for wards without climate control. In that hospital, the overall incidence was associated with higher temperature (incidence rate ratio for each Celsius degree, 1.05; 95% Confidence Interval, 1.01-1.09; P = 0.006). Weather parameters were not associated with ABBSI in the hospitals from Goiânia and Fortaleza. In conclusion, seasonality was found in the hospitals with higher ABBSI incidence and located in regions with greater thermal amplitude. Strict temperature control may be a tool for prevention of A. baumanii infections in healthcare settings.

In vitro activity of the novel siderophore cephalosporin, cefiderocol, in Gram-negative pathogens in Europe by site of infection

ObjectivesWe assessed the activity of the novel siderophore cephalosporin, cefiderocol and selected other antibacterial agents against Gram-negative bacterial isolates in Europe. MethodsIsolates were obtained between 2013 and 2018 from European countries participating in the SIDERO-WT and SIDERO-Proteeae multinational surveillance studies. Isolates were categorised by infection site, focusing on bloodstream infections, hospital-acquired/ventilator-associated bacterial pneumonia (HABP/VABP), complicated intra-abdominal infections and complicated urinary tract infections. Cefiderocol activity was compared with ceftazidime–avibactam, ceftolozane–tazobactam, colistin and meropenem using standard susceptibility testing methods. European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints were used to interpret susceptibility data. ResultsIsolates (n = 20 911) were collected from 145 sites in 24 countries in Europe, the highest proportion (34%) being from patients with HABP/VABP. Enterobacterales (66.6% of isolates) were more frequent than glucose non-fermenting species (33.4%) overall, with some differences between infection sites. Across all infection sites, the MIC50/MIC90 for cefiderocol was ≤0.5/≤2 mg/L for Enterobacter spp., ≤0.25/<2 mg/L for Klebsiella spp., 0.12/2 mg/L for Acinetobacter spp., ≤0.25/1 mg/L for Pseudomonas aeruginosa and ≤0.12/≤0.5 mg/L for Stenotrophomonas maltophilia. Across all infection sites, cefiderocol MICs were ≤2 mg/L for ≥96% of Enterobacter spp., ≥95% of Klebsiella spp., ≥90% of Acinetobacter spp. and ≥99% of Pseudomonas aeruginosa and Stenotrophomonas maltophilia isolates. Cefiderocol maintained high activity in carbapenem-resistant isolates, and the difference in activity between carbapenem-resistant (percentage susceptibility at EUCAST breakpoint: E. coli 77.8%, Klebsiella spp. 69.2%, Pseudomonas aeruginosa 97.5%, Acinetobacter spp. 90.7%, Stenotrophomonas maltophilia 99.6%) and carbapenem-susceptible (percentage susceptibility at EUCAST breakpoint: E. coli 99.4%, Klebsiella spp. 98.0%, Pseudomonas aeruginosa 99.7%, Acinetobacter spp. 94.9%) isolates was lower for cefiderocol than other agents. ConclusionsCefiderocol had excellent activity against all Gram-negative species, independent of key infection site and carbapenem MIC. Cefiderocol is a useful addition to the therapeutic options available for these difficult-to-treat infections.

Evaluation of the BD Phoenix CPO detect panel for prediction of Ambler class carbapenemases

Rapid detection of carbapenemases as a cause of resistance is beneficial for infection control and antimicrobial therapy. The BD Phoenix NMIC-502 panel and CPO detect test identifies presence of carbapenemases in Enterobacterales such as Klebsiella pneumoniae and assigns them to Ambler classes. To evaluate the performance of the CPO detect panel, we employed a European collection of 1222 K. pneumoniae including carbapenem non-susceptible and susceptible clinical isolates from 26 countries, for which draft genomes were available after Illumina sequencing and the presence of carbapenemase genes had been identified by ARIBA gene calling. The CPO panel detected 488 out of 494 carbapenemase-encoding isolates as positive and six as negative. One-hundred and two isolates were tested positive for carbapenemase in the absence of any carbapenemase gene. The CPO panel identified 229 out of 230 KPC-positive isolates as carbapenemase producing and classified 62 of these as class A enzyme. Similarly, the CPO panel correctly specified 167 of 182 as class D. Regarding metallo-beta-lactamases, the CPO panel assigned 78 of 90 MBL positive isolates to class B enzymes. The sensitivity of the CPO panel in detecting carbapenemase activity was 99.5%, 97.7% and 98.3% for class A, B and D enzymes, respectively. The sensitivity in assignation to Ambler class A, B and D was 27%, 86% and 91%, respectively. An overall sensitivity of 98.8% and specificity of 86% in unclassified detection of carbapenemases was observed, with frequent false positive detection of carbapenemase producing organisms, thus rendering further confirmatory tests necessary.

Carbapenem Resistance in Non-Fermentative Gram-Negative Bacilli Isolated from Intensive Care Unit Patients of a Referral Hospital.

Non-fermentative Gram-negative bacilli or non-fermenters are opportunistic pathogens associated with serious infections in intensive care unit patients. Although carbapenems were considered as a backbone of treatment for life-threatening infections, these bacteria are increasingly acquiring resistance to carbapenems. Carbapenem-resistant Acinetobacter baumannii and Pseudomonas aeruginosa are prioritized as critical pathogens by the World Health Organization. The objective of the study was to document the status of carbapenem-resistant and carbapenemase-producing non-fermenters isolated from intensive care unit patients. This study was conducted at Tribhuvan University Teaching Hospital, Kathmandu, Nepal. The clinical specimens collected from intensive care unit patients were processed for isolation and identification of non-fermenters and antibiotic susceptibility profile of bacterial isolates was determined. The multidrug-resistant isolates were identified and carbapenemase enzyme was detected in the carbapenem-resistant isolates. A total of 157 non-fermenters were isolated from 1063 samples which included Acinetobacter species (n=85), Pseudomonas aeruginosa (n=55), Burkholderia cepacia complex (n=15), and Stenotrophomonas maltophilia (n=2). Carbapenem resistance was reported in 85.9%, 72.7%, and 33.3% of Acinetobacter species, Pseudomonas aeruginosa, and Burkholderia cepacia complex, respectively. Among total non-fermenters, 91.1% isolates were multidrug-resistant and 60.8% carbapenem-resistant isolates were carbapenemase producers. The carbapenem-resistant isolates demonstrated an extremely high degree of resistance than carbapenem-susceptible isolates towards other antimicrobial classes. This study reported high rates of carbapenem-resistant, carbapenemase-producing, and multidrug-resistant non-fermenters isolates. Therefore, preventing the spread of these superbugs among the critically ill patients in intensive care units should be a major initiative in hospitals.