Aerogenes Isolates Research Articles

Molecular insights into the evolutionary trajectory of a Klebsiella aerogenes clinical isolate with a complex trade-off between resistance and virulence.

The fitness cost associated with antimicrobial resistance has an important influence on evolutionary dynamics. We compared the genomes of three Klebsiella aerogenes isolates recovered from blood samples or deep abscess cultures from the same patient: the wild-type strain (CT_WT), a piperacillin-tazobactam-resistant strain (CT_PENI), and an extended-spectrum-cephalosporin (ESC)-resistant strain (CT_R). Whole-genome sequencing revealed that CT_PENI had acquired a TEM-1 β-lactamase with a mutated promoter, accounting for overproduction. CT_PENI then acquired an E240G substitution in the TEM-1 β-lactamase (resulting in TEM-207) and lost the porin-encoding ompK36 gene to give CT_R. All three strains showed the same virulence in a mouse model of intraperitoneal infection. The results of recombination and transformation assays indicated that when present separately, the TEM-207 overproduction and the ompK36 gene deletion had only small effects on susceptibility to ESCs. However, the combination of the two changes led to a much lower susceptibility to ESCs. Moreover, the levels of fitness in vitro and in vivo in a murine model of gut colonization were significantly lower after TEM-1 β-lactamase overproduction and lower still after E240G substitution and OmpK36 loss. We hypothesize that the chosen courses of antibiotics led to the stepwise emergence of a clone with resistance to penicillins and ESCs and no loss of virulence. However, acquired resistance may have a fitness cost that limits evolutionary success. Our results might explain why the overproduction of extended-spectrum β-lactamases (which should confer a high level of piperacillin-tazobactam resistance) is not observed in clinical practice and why TEM-207 has rarely been detected in clinical isolates.

Genomic and Phenotypic Analysis of bla KPC-2 Associated Carbapenem Resistance in Klebsiella aerogenes: Insights into Clonal Spread and Resistance Mechanisms Across Hospital Departments in Beijing.

This study conducted an phenotypic and whole-genome sequencing analysis with Klebsiella aerogenes to elucidate its clinical epidemiological characteristics, antimicrobial resistance (AMR) phenotype, biofilm formation ability and hemolytic activity testing, AMR genes and phylogenetic relationships, so as to provide a further understanding of the intra-hospital strain transmission. Samples were collected from a hospital in Beijing between 2020 and 2022. All strains underwent bacterial identification, antimicrobial susceptibility testing (AST) using the VITEK-2 compact system. Biofilm formation ability and hemolytic activity were tested. Second-generation sequencing was applied to all strains, with those carrying the bla KPC gene were selected for third-generation sequencing. Whole-genome analysis identified resistance genes, plasmid types, MLST typing, and phylogenetic relationships. Plasmids were assembled to detect plasmid structures and AMR gene location. Among the 42 K. aerogenes isolates, 21 were carbapenem-resistant K. aerogenes (CRKA). All strains exhibited strong biofilm formation and no hemolytic activity. Most were sourced from sputum (83.3%). CRKA demonstrated extensive resistance to antibiotics, particularly β-lactamase inhibitors and Cefotetan. This resistance pattern was closely associated with the presence of an IncFII(pHN7A8) plasmid, which carried multiple resistance genes, including bla KPC-2, bla CTX-M-65, bla TEM-1, rmtB and a large number of mobile elements. The majority of CRKA strains clustered within the same branch of the phylogenetic tree, exhibiting minimal single nucleotide polymorphism (0-13 SNPs) differences, and they shared the same sequence type (ST292), resistance genes, and plasmids, originating from different departments, suggesting clonal transmission among the hospital. Our research reveals that the clonal transmission of CRKA occurs across various departments within the hospital. The widespread resistance observed in CRKA, attributed to the presence of bla KPC and ESBLs genes, underscores the need for heightened vigilance to prevent the further dissemination of CRKA within the hospital and, potentially, throughout the wider community.

Occurrence and characteristics of blaOXA-181-carrying Klebsiella aerogenes from swine in China

Klebsiella aerogenes is a largely understudied opportunistic pathogen that can cause sepsis and lead to high mortality rates. In this study, we reported the occurrence of carbapenem-resistant blaOXA-181-carrying Klebsiella aerogenes from swine in China and elucidate their genomic characteristics. A total of 126 samples, including 109 swine fecal swabs, 14 environmental samples, and three feed samples were collected from a pig farm in China. The samples were enriched with LB broth culture and then inoculated into MacConkey agar plates for bacterial isolation. After PCR detection of carbapenemases genes, the blaOXA-181-carrying isolates were subjected to antimicrobial susceptibility testing, and whole-genome sequence analysis. Four Klebsiella aerogenes isolates carrying the blaOXA-181 gene were obtained from swine faecal samples. All the 4 strains were belonged to ST438. The blaOXA-181 genes were located in IncX3-ColKP3 hybrid plasmids with the core genetic structure of IS26-ΔIS3000-ΔISEcp1-blaOXA-181-ΔlysR-ΔereA-ΔrepA-ISKpn19-tinR-qnrS1-ΔIS2-IS26, which suggests the potential for horizontal transfer and further dissemination of this resistance gene among Enterobacteriaceae and other sources. This study represents the first instance of OXA-181-producing K. aerogenes being identified from swine faeces in China. It is crucial to maintain continuous monitoring and ongoing attention to the detection of K. aerogenes carrying blaOXA-181 and other resistance genes in pigs.

Activity of cefepime, carbapenems and new β-lactam/β-lactamase inhibitor combinations on Enterobacter cloacae complex and Klebsiella aerogenes in Spain (SMART 2016–2022)

Abstract Objectives To analyse the susceptibility profile to cefepime, carbapenems and new β-lactam/β-lactamase inhibitor combinations in Enterobacter cloacae complex and Klebsiella aerogenes isolated from intra-abdominal, urinary, respiratory and bloodstream infections in the SMART (Study for Monitoring Antimicrobial Resistance Trends) surveillance study in Spain. Methods The susceptibilities of 759 isolates (473 E. cloacae complex and 286 K. aerogenes) collected in 11 Spanish hospitals from 2016 to 2022 were analysed following the EUCAST 2023 criteria. Molecular characterization looking for β-lactamase genes was performed through PCR and DNA sequencing analysis. Results E. cloacae complex showed resistance to third-generation cephalosporins in 25% of the cases, whereas K. aerogenes was resistant in 35%. Regarding cefepime, resistance in E. cloacae was higher (10%) than in K. aerogenes (2%). Carbapenems showed >85% activity in both microorganisms. Ceftazidime/avibactam, imipenem/relebactam and meropenem/vaborbactam had good activity against these microorganisms (>95%). In contrast, the activity of ceftolozane/tazobactam was lower (80%). A high proportion of the isolates resistant to new β-lactam/β-lactamase inhibitor combinations carried a carbapenemase, mainly OXA-48-like and VIM-1. Conclusions Ceftazidime/avibactam, imipenem/relebactam and meropenem/vaborbactam show high activity against both E. cloacae complex and K. aerogenes isolates recovered in the SMART-Spain study. In contrast, differences have been found in the case of cefepime, showing more activity against K. aerogenes than E. cloacae complex. These results are useful for antimicrobial stewardship programmes and for the implementation of local and national guidelines.

Fecal carriage of extended-spectrum β-lactamase-producing enterobacterales from hospitals and community settings in Gaza Strip, Palestine

BackgroundThe fecal carriage of extended-spectrum β-lactamase-producing Enterobacterales (ESBL-PE) is a major driver of the global spread of these antibiotic resistance determinants. Here we determined the rate of fecal ESBL-PE carriage in pediatric hospitals and community-serving healthcare centers serving adults and children in the Gaza Strip, Palestine.MethodsA total of 373 fecal and rectal samples were collected from different hospitals and clinics in Gaza. The antibiotic susceptibility was determined using the disk diffusion method and interpreted according to CLSI guidelines. The bacterial isolates were tested for ESBL production using phenotypic methods (double disk synergy test and growth on selective chromogenic media). BlaCTX−M, blaSHV, and blaTEM genes were sought by PCR.ResultsOut of the 373 isolates tested, 138 (37%) were considered ESBL positive as revealed by phenotypic tests. The prevalence of ESBLs among hospitalized patients was 39.1% (hospital setting) whereas, among outpatients attending community healthcare centers, it was 35.1% (community setting). ESBL production among Escherichia coli, Klebsiella pneumoniae, Citrobacter freundii, Proteus mirabilis, and Klebsiella aerogenes isolates was 52.8%, 39.1%, 26.7%, 2.8%, and 2.1% respectively. Meropenem and amikacin were the most effective antibiotics against ESBL producers (68.9% and 73.6% susceptibility, respectively), while only 15.2%, 22.5%, and 24.6% remained susceptible to ceftazidime, cefotaxime, and ceftriaxone, respectively. Out of 138 phenotypically ESBL-positive isolates, 98 randomly chosen were screened for blaCTX−M, blaTEM, and blaSHV genes. The prevalence rate of blaCTX−M was 45.9%, while blaTEM and blaSHV genes were detected in 16.8% and 5.2% of CTX-M-negative isolates (corresponding mostly for K. pneumoniae isolates in the case of SHV-PCR), respectively.ConclusionsThe study revealed an alarmingly high prevalence of fecal carriage of ESBL-producing Enterobacterales among hospitalized children but also in the community of the Gaza Strip. In addition, 30% of ESBL-producers were already resistant to carbapenems, the treatment of choice of infections with ESBL-producers.

2238. Effect of Cefazolin Breakpoint Update in Susceptibility Reports on Antimicrobial Use

Abstract Background The Clinical Laboratory Standards Institute updated the breakpoints for cefazolin in the treatment of E. coli, Klebsiella, and Proteus (EKP) infections in 2011 to reflect doses used in clinical practice and achievable therapeutic concentrations in different body sites (urine vs. non-urine). The UTMB clinical microbiology laboratory adopted this update in January 2022 with the introduction of MicroScan™ technology. Our objective was to evaluate the effect of the cefazolin breakpoint update on antimicrobial use in EKP bloodstream infections. Methods This was a retrospective, multicenter, pre-post, study conducted at four UTMB hospitals. Pre-intervention data was collected from January 2021 to December 2021 and post-intervention data was collected from February 2022 to March 2023. Patients ≥ 18 years old were included if they were admitted to a UTMB hospital and received antibiotics for EKP bacteremia. Texas Department of Criminal Justice patients, those with beta-lactam anaphylaxis, polymicrobial bacteremia, immunocompromised patients, and Klebsiella aerogenes isolates were excluded. The primary outcome was cefazolin days of therapy (DOTs) for EKP bacteremia. Extended-spectrum beta-lactamase (ESBL)-producing isolates and Clostridioides difficile (C. difficile) infection six months after the index admission, and in-hospital and 28-day mortality were also assessed. Results There were 50 and 48 patients included in the pre- and post-intervention periods, respectively. Most patients were female (59%) with a mean age of 67.8 years (standard deviation [SD] 14.9). The most isolated gram-negative pathogen was Klebsiella pneumonia (81%) followed by Proteus mirabilis (13%) from urinary sources of infection (59%). There was no significant difference in median cefazolin DOTs before (0 days; interquartile range [IQR] 0,0) and after (0 days; IQR 0,0) the breakpoint update (p=0.35). There was no difference in ESBL-producing pathogens (2 vs. 3, p=0.67), C. difficile infection (1 vs. 2, p=0.61), in-hospital (3 vs. 7, p=0.20), or 28-day mortality (0 vs. 0, p=1) between the pre- and post-breakpoint update groups. Conclusion Updating the breakpoint to a lower value for EKP isolates in the blood did not have an effect on cefazolin use. Disclosures All Authors: No reported disclosures

Evaluation of antibacterial activity of pomegranate (Punica granatum L. and Citrus lemon against urinary tract infection causing bacteria E. Coli, Enterococcus fecalis, Enterobacter aerogenes collected from various diagnostic laboratories of Khwazakhela,

E. Coli is one of the major gram-negative pathogens well known causative agent for almost all kind of UTIs, however Enterobacteriaceae such as Enterobacter aerogenes and Enterococci fecalis are responsible for UT infections. The present study was conducted to evaluate the in vitro antibacterial activity of ethanol and aqueous extract of pomegranate and lemon peels against (23 isolated stains) E. Coli, (16 isolated strains) Enterococcus faecalis and (9 isolated strain) of Enterobactor aerogenes recovered from the urine sample of patientsin Swat KPK-Pakistan. The Agar dilution and well method was applied for the antibacterial activity of pomegranate and lemon peelextracts. All of the three subject isolates were exposed to different concentrations of pomegranate and lemon peel. MIC of aqua extract of pomegranateagainst the subject isolates of E. Coli was 200 µl/mLand ethanol extract was 50 µl/mL. So the ethanol extract of pomegranate was found to be more effective as compared to the aqueous extract. On the other hand MIC of aqua extract lemon peel against the subject isolates of E. coli was100 µl/mL and ethanol extract was 25 µl/mL. So the ethanol extract of pomegranate was found to be more effective as compared to the aqueous extract. MIC of ethanol extract of pomegranate against the isolates of Enterococcus fecalis was found smaller (50 µl/mL) than that of water extract (100 µl/mL). So the ethanol extract of pomegranate was found to be more effective as compared to the aqueous extract. On the other hand. MIC of aqua lemon extract against the subject isolates of Enterococcus fecalis was 100 µl/mL and ethanol extract was 25 µl/mL. Mainly the ethanolic extract of lemon peel was more effective than the ethanolic extract of pomegranate against Enterococcus fecalis isolates. The MIC of the water and ethanolic extract of pomegranate against Enterobacter aerogenes was found 500 µl/mL and 200 µl/mL respectively. So the ethanol extract of pomegranate was found to be more effective as compared to the aqueous extract. On the other hand MIC of the ethanolic extract of lemon peel was 100 µl/mL, while the water extracts showed inhibition against the Enterobacter aerogenes isolates at the concentration of 250 µl/mL. So the ethanol extract of lemon was found to be more effective as compared to the aqueous extract.For the determination of antibacterial activity of both pomegranate and lemon extracts (in ethanol and water) method as described in Clinical and Laboratory Standard Guidelines (CLSI) was adopted. The subject isolate of E. Coli, Enterococcus fecali, and Enterobacter aerogenes were shown different sensitivities (sensitive >10mm zone inhibition or resistant <10mm zone inhibition t) for ciprofloxacin with a variable zone of inhibition.

Antimicrobial Activity of Acacia Nilotica and Ziziphus Mauritiana against Clinical Isolates of Escherichia Coli and Klebsiella Aerogenes

Klebsiella aerogenes is an opportunistic pathogen linked to several nosocomial illnesses, including pneumonia, sepsis, and infection of the urinary tract. Escherichia coli is frequently the source of numerous common bacterial illnesses, including bacteraemia, cholecystitis, cholangitis, urinary tract infections (UTI), traveler's diarrhoea, and other medical conditions such as meningitis in babies and pneumonia. This study aimed at determining the antimicrobial activity of Acacia nilotica and Ziziphus mauritania on clinical isolate of E. coli and K. aerogenes. The phytochemical constituents of Z. mauritiana and A. nilotica were determined. E. coli and K. aerogenes isolates were obtained from the Barau Dikko Teaching Hospital, Kaduna and reconfirmed using standard microbiological techniques. The antibacterial activity of Z. mauritiana and A. nilotica extracts against the isolates was determined using Agar well diffusion assay, the MIC and MBC was also determined and recorded. The findings of this study revealed that tannins, quinone, phenols, terpenoids, and steroids are present in Z. mauritiana extract while tannins, saponin, quinones, and terpenoids in A. nilotica extract. There was no activity of Z. mauritiana against any of the test isolates at all concentrations used in this study. Whereas A. nilotica exhibited an antibacterial activity against both E. coli and K. aerogenes recording respectively a zone of inhibition of 24 mm and 25 mm with MIC and MBC value of 600 mg/ml. This research displayed an antibacterial activity of A. nilotica and no activity of Z. mauritiana against E. coli and K. aerogenes.

Whole-genome sequencing analysis of Klebsiella aerogenes among men who have sex with men in Guangzhou, China.

Klebsiella aerogenes is a common infectious bacterium that poses a threat to human health. Nevertheless, there are limited data on the population structure, genetic diversity, and pathogenicity of K. aerogenes, especially among men who have sex with men (MSM). The present study aimed to clarify the sequence types (STs), clonal complexes (CCs), resistance genes, and virulence factors of popular strains. Multilocus sequence typing was used to describe the population structure of K. aerogenes. The Virulence Factor Database and Comprehensive Antibiotic Resistance Database were used to assess the virulence and resistance profiles. In this study, next-generation sequencing was performed on nasal swabs specimens collected in an HIV Voluntary Counseling Testing outpatient department in Guangzhou, China, from April to August 2019. The identification results showed that a total of 258 K. aerogenes isolates were collected from 911 participants. We found that the isolates were most resistant to furantoin (89.53%, 231/258) and ampicillin (89.15%, 230/258), followed by imipenem (24.81%, 64/258) and cefotaxime (18.22%, 47/258). The most common STs in carbapenem-resistant K. aerogenes were ST4, ST93, and ST14. The population has at least 14 CCs, including several novel ones identified in this study (CC11-CC16). The main mechanism of drug resistance genes was antibiotic efflux. Based on the presence of the iron carrier production genes irp and ybt, we identified two clusters according to virulence profiles. In cluster A, CC3 and CC4 carry the clb operator encoding the toxin. Increased monitoring is needed for the three main ST type strains carried by MSM. The main clone group CC4 has a large number of toxin genes, and it spreads among MSM. Caution is needed to prevent further spread of this clone group in this population. In sum, our results may provide a foundation for the development of new therapeutic and surveillance strategies for treating MSM.

Emergence and clonal spread of KPC-2-producing clinical Klebsiella aerogenes isolates in a hospital from northwest Argentina.

Introduction. Klebsiella aerogenes is a nosocomial pathogen associated with drug resistance and healthcare-associated infections.Gap Statement. K. aerogenes is associated with hospital-acquired infections with the ability to acquire mechanisms of resistance to reserve antimicrobials; its clinical behaviour has been poorly documented.Objective. We proposed to investigate an outbreak of carbapenem-resistant K. aerogenes in a hospital that persisted for 4 months.Methods. The primary aim was to evaluate the molecular characteristics and the clonal relationships among the isolates. We characterized isolates by polymerase chain reaction (PCR) and pulsed-field gel electrophoresis (PFGE). The information was integrated with clinical and epidemiological data.Results. Fourteen strains were disseminated in an intensive care unit and different wards at the hospital. The overall mortality was 42.8 %, and mortality attributed to infection was 21.4 %; strains showed high rates of resistance to most of the antimicrobials tested and carried bla KPC-2, bla SHV-2 and bla CTXM-15 genes. PFGE analysis indicated 2 PFGE groups; 12/14 isolates were associated with subgroup A and were likely to be primarily responsible for the first isolation and subsequent dissemination. The outbreak characteristics data showed prolonged hospitalization and previous use of antibiotics as potential risk factors.Conclusion. We consider that it is essential to perform phenotypic and genotypic identification of early genetic resistance mechanisms in K. aerogenes isolates, not only from infection sites but also from colonization, to prevent the spread of these multidrug-resistant (MDR) isolates.

1737. Xeruborbactam (QPX) Potentiates the Activity of β-Lactam (BL) Antibiotics Against a Diverse Group of Highly Drug-Resistant Enterobacterales (ENT)

Abstract Background Antibiotic resistant ENT are a growing threat worldwide. QPX is an ultra-broad-spectrum β-lactamase inhibitor (BLI) with potent inhibition of classes A and D, and many metallo-β-lactamases, which has potential to fill the void of currently available BL-BLIs. Methods We evaluated QPX (fixed concentration of 8 µg/mL) in combination with meropenem (MEM), cefepime (FEP) and aztreonam (ATM) against a diverse group of ENT clinical isolates selected from a worldwide repository. Antibiotic resistance determinants were assessed by mining whole-genome sequencing data generated using Illumina MiSeq. Results Klebsiella spp, Enterobacter spp, and Escherichia coli were most common among the 90 isolates tested (Fig. 1). 71% (64) produced carbapenemases (Fig. 2): 3 isolates produced both class A and B carbapenemases. 11% of isolates harbored mutations in ompK 36/ompC genes. 57% (51) were resistant to MEM, 31% to imipenem-relebactam, 17% (15) to ceftazidime-avibactam (CZA), and 9% to MEM-vaborbactam (MVB). ENT-resistant to CZA were due to production of class B, D or KPC-3 variants, or ompC mutation in a K. aerogenes isolate. ENT-resistant to MVB were due to class B or D enzymes, or class A with ompK36 or ompC mutations. MIC distributions of BL with or without QPX against all isolates tested are presented in Fig. 3. Addition of QPX to MEM, FEP and AMT reduced MIC50s and MIC90s of these agents (Fig. 3; p< 0.0001). Of note, addition of QPX reduced MEM MICs more than did vaborbactam (median 533- versus 24-fold; p=0.0006). QPX reduced MICs of MEM, FEP and ATM to levels below respective breakpoints for non-susceptibility (Fig. 3). MIC distribution of ENT isolates stratified by the types of carbapenemases are presented in Fig. 4. QPX potentiated activity of MEM, FEP or ATM against ENT, regardless of whether they produced class A, B or D carbapenemases. Conclusion QPX enhanced activity of MEM, FEP and ATM against carbapenemase-producing or other carbapenem-resistant ENT (CRE), regardless of species or other resistance determinants. Most remarkably, QPX rendered each BL equally active against CRE. The expanded spectrum of QPX against class B and D carbapenemases addresses a major unmet need against CRE. Disclosures Cornelius J. Clancy, MD, receives research funding paid to his institution from Astellas and Merck: Grant/Research Support|serves as an advisory Board member for Astellas, Cidara, and Scynexis, served on the advisory board for Merck, Qpex Biopharma, and Shionogi: Advisor/Consultant|Venatorx and Needham & Associates: Advisor/Consultant.

Andrographolide and 4-Phenylbutyric Acid Administration Increase the Expression of Antimicrobial Peptides Beta-Defensin-1 and Cathelicidin and Reduce Mortality in Murine Sepsis.

Antibiotic resistance is a global threat and requires the search for new treatment strategies. Natural antimicrobial peptides (AMPs) have pronounced antibacterial, antiviral, antifungal, and antitumor activity. AMPs' clinical use is complicated by the high synthesis costs and rapid proteolytic degradation. The search for small molecules, inducers of endogenous AMP expression, could become a new approach. Here, we investigated for the first time the effect of seven small molecules (andrographolide, levofloxacin, azithromycin, montelukast, 4-phenylbutyric acid, rosuvastatin and valsartan) on AMP (beta-defensin-1, hBD-1 and cathelicidin, LL-37) serum levels in rats. In control groups, the level of hBD-1 was 295.0 (292.9-315.4) pg/mL, and for LL-37, it was 223.8 (213.3-233.6) pg/mL. Andrographolide (ANDR) and 4-phenylbutyric acid (4-PHBA) administration significantly enhanced the level of both AMPs. The hBD-1 level was 581.5 (476.3-607.7) pg/mL for ANDR and 436.9 (399.0-531.6) pg/mL for 4-PHBA. The LL-37 level was 415.4 (376.2-453.8) pg/mL for ANDR and 398.9 (355.7-410.1) pg/mL for 4-PHBA. Moreover, we have shown that these compounds reduce mortality in a murine model of sepsis caused by a carbapenem-resistant Klebsiella aerogenes isolate. From our point of view, these small molecules are promising candidates for further study as potent AMP inducers. The data obtained allow the development of new strategies to combat antibiotic resistance and infectious diseases.

Emergence of a floR-carrying plasmid in extended spectrum β-lactamase (ESBL) producing Pasteurella aerogenes, isolated from an avian species in China

Identification and analysis of the antimicrobial resistance of Pasteurella aerogenes (P. aerogenes) isolated from poultry. For susceptibility testing in accordance with the CLSI, plasmids were extracted via alkaline lysis and transferred by CaCl2 treatment. Genomic DNA of a representative P. aerogenes isolate was subjected to whole genome sequencing. CCCP was utilized to determine whether SF190908 contains an efflux pump. The blaVEB gene was ligated with the pET-28 plasmid and transferred to Escherichia coli to verify it as an ESBL gene. SF190908 isolated from poultry was identified as P. aerogenes based upon biochemical and 16s rRNA results. The isolate showed high MIC values for eight antimicrobials. Sequencing results showed that the mobile element-mediated antimicrobial resistance gene cluster conferred antimicrobial resistance on the strain, and a single 5,105-bp plasmid, designated pRCAD0752PA-1, was isolated. Four antimicrobial resistance gene clusters were identified in the SF190908 chromosome; one antimicrobial resistance gene cluster carried the blaVEB gene, which was verified as ESBL according to the CLSI and was detected in Pasteurellaceae for the first time, to the best of our knowledge. The efflux pump may confer antimicrobial resistance to SF190908. P. aerogenes isolated from poultry showed resistance genes encoded in mobile elements that confer multi-antimicrobial resistance to SF190908. The antimicrobial-resistant plasmid pRCAD0752PA-1 was isolated in SF190908 and conferred resistance to florfenicol. This study indicates an urgent need to increase efforts to monitor the spread of P. aerogenes multi-antimicrobial-resistant strains and plasmids, especially in newly discovered at-risk species such as poultry.

First detection of a colistin-resistant Klebsiella aerogenes isolate from a critically ill patient with septic shock in Bulgaria.

Colistin is considered as the last-line antibiotic for the treatment of infections caused by extensively drug-resistant Gram-negative pathogens belonging to the ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) group. The present study aimed to explore the colistin resistance mechanisms of a Klebsiella aerogenes (formerly Enterobacter aerogenes) isolate (Kae1177-1bg) obtained from a Bulgarian critically ill patient with septic shock in 2020. Antimicrobial susceptibility testing and whole-genome sequencing using DNA nanoball technology were performed. The resulting read pairs were used for draft genome assembly, MLST analysis and mutation screening in the pmrA/B, phoP/Q, and mgrB genes. Kae1177-1bg demonstrated high-level resistance to colistin, resistance to 3rd generation cephalosporins and susceptibility to all other antibiotics tested. In our strain a CMY-2-type class C cephalosporinase was the only β-lactamase identified. No mobile colistin resistance (mcr) genes were detected. A total of three missense variants in the genes for the two-component PmrA/PmrB system were identified. Two of them were located in the pmrB (pR57K and pN275K) and one in the pmrA gene (pL162M). The pN275K variant emerged as the most likely cause for colistin resistance because it affected a highly conservative position and was the only nonconservative amino acid substitution. In conclusion, to the best of our knowledge, this is the first documented clinical case of a high-level colistin-resistant K. aerogenes in Bulgaria and the first identification of the nonconservative amino acid substitution pN275K worldwide. Colistin-resistant Gram-negative pathogens of ESKAPE group are serious threat to public health and should be subjected to infection control stewardship practices.

Prevalence of Extended-Spectrum Beta-Lactamases Enzymes in Enterobacter Aerogenes Isolated from Urinary Tract Infections in Shahrekord City

Introduction: Enterobacteriaceae produce the Extended-Spectrum Beta-Lactamases which is considered as an important resistant mechanism of beta-lactam antibiotics. The resistance to beta-lactam antibiotics is the main problem in the bacterial infections therapy. The prevalence of these enzymes changes in different geographical areas and with time. The present study aims to explore the frequency of the extended-spectrum blaSHV, blaCTX-M, blaTEM, in Enterobacter aerogenes isolated from urinary tract infections in Shahrekord City; the mentioned genes were investigated from the phenotypic and genotypic point of view. Methods: In this cross-sectional descriptive study, antibacterial susceptibility patterns of 50 isolates of Enterobacter aerogenes to Cefotaxim, Ceftazidim, Cefterixon and cephalotin were tested using disk diffusion (Kirby-Buer) method. In addition, confirmatory tests for detecting ESBLs phenotypes were performed using Ceftazidim-clavulanic acid and Cefotaxim- clavulanic acid combination disks. Then, the presence of blaSHV, blaCTX-M, blaTEM, genes in the broad-spectrum beta-lactamase producing strains was assessed in the presence of specific primers. Results: Out of 50 isolates of Enterobacter aerogenesis investigated in this study, 32 isolates (64%) were identified to produce broad-spectrum β-lactamases in the phenotypic study of ESBLS, and the prevalence of blaCTX-M, blaTEM and blaSHV was reported as 30%, 20% and 14%, respectively. In the statistical analysis, a statistically significant correlation was observed between resistance to the antibiotic ceftriaxone and the blaCTX-M, gene (p<0.05). Conclusion: The present study suggests that ESBL producing Enterobacter aerogenes isolates have a high prevalence. The increase in the number of these species is often caused due to the irrational prescription of antibiotics, which requires the use of new antimicrobial agents and limiting the unnecessary use of antimicrobial agents and increasing the use of infection control tools.

A Yersiniabactin-producing Klebsiella aerogenes Strain Causing an Outbreak in an Austrian Neonatal Intensive Care Unit.

Yersiniabactin, a siderophore with a high affinity to iron, has been described as a potential virulence factor in Enterobacteriaceae. Klebsiella aerogenes is a Gram-negative rod known to cause invasive infection in very low birth weight infants but is an unusual pathogen to cause outbreaks in neonatal intensive care units (NICU). We performed a retrospective analysis of all patients colonized with K. aerogenes in our NICU from September to December 2018. Each infant with an occurrence of K. aerogenes in any microbiological culture was defined as a case. Clinical data were taken from medical charts. K. aerogenes isolates were genotyped using whole-genome sequencing combined with core genome multilocus sequencing type analysis. Yersiniabactin production was evaluated by luciferase assay. In total 16 patients were colonized with K. aerogenes over the 3-month period and 13 patients remained asymptomatic or developed late-onset neonatal sepsis from another pathogen. Three patients developed necrotizing enterocolitis, 2 complicated by sepsis and 1 of them died. All symptomatic patients were premature infants with low birth weight. Genetic sequencing confirmed an outbreak with the same strain, all samples expressed the high-pathogenicity island, necessary for the production of yersiniabactin. Six exemplary cases were proven to produce yersiniabactin in vitro. This is the first report of an outbreak of a yersiniabactin-producing K. aerogenes strain causing invasive infection in preterm infants. We hypothesize that, due to improved iron uptake, this strain was associated with higher virulence than non-yersiniabactin-producing strains. Extended search for virulence factors and genetic sequencing could be pivotal in the management of NICU outbreaks in the future.

P09 Activity of newer antibiotics against NDM- and OXA-48-producing organisms

BackgroundSeveral antibiotics active against carbapenemase-producing organisms have recently been licensed for clinical use. These organisms usually have multiple integrative and conjugative elements with different resistance genes. The positioning of these agents for empirical use in sepsis caused by different carbapenemase-producing organisms is important in optimizing the likelihood of appropriate treatment before susceptibility testing is complete. Here we present the activities of meropenem-vaborbactam, imipenem-relebactam, eravacycline and tigecycline against NDM- and OXA-48-producing clinical isolates in a London teaching hospital.MethodsSixty-two previously characterized carbapenemase-producing Gram-negative clinical isolates were studied. These comprised 31 NDM and 31 OXA-48 producers. OXA-48 producers comprised Klebsiella pneumoniae (17), Escherichia coli (10), Enterobacter aerogenes (3) and Serratia marcescens (1). NDM producers comprised K. pneumoniae (11), E. coli (10), Acinetobacter baumannii (3), Klebsiella oxytoca (1), Enterobacter asburiae (1), Enterobacter cloacae (1), Pseudomonas aeruginosa (1), Citrobacter koseri (1), Citrobacter freundii (1) and Leclercia adecarboxylata (1). MICs of meropenem/vaborbactam, imipenem/relebactam, eravacycline and tigecycline were determined using Etests. Interpretation was done using EUCAST breakpoints.Results OXA-48 producers: Eight of 17 K. pneumoniae, 8/10 E. coli and 2/3 E. aerogenes isolates were meropenem/vaborbactam susceptible. Of these, 2 K. pneumoniae, 5 E. coli and 1 E. aerogenes isolates were imipenem/relebactam susceptible. All imipenem/relebactam/susceptible isolates were also meropenem/vaborbactam susceptible. The S. marcescens isolate (1/1) was resistant to both antibiotics. The only isolates demonstrating susceptibility to the glycylcyclines were E. coli. Five of 10 were susceptible to both glycylcyclines. One of 10 was susceptible to one glycylcycline but resistant to the other. NDM producers: Five of 11 K. pneumoniae, 6/10 E. coli and 1/1 K. oxytoca, E. asburiae and C. koseri isolates were susceptible to meropenem/vaborbactam. Of these, two K. pneumoniae and the K. oxytoca (1/1) and E. asburiae (1/1) isolates were imipenem/relebactam susceptible. The L. adecarboxylata isolate (1/1) was meropenem/vaborbactam resistant but imipenem/relebactam susceptible. All P. aeruginosa, C. freundii, A. baumannii and E. cloacae isolates were resistant to both meropenem/vaborbactam and imipenem/relebactam. Seven of 10 E. coli isolates were tigecycline susceptible of which 6 were also eravacycline susceptible. One of 11 K. pneumoniae, 1/1 K. oxytoca and 1/1 L. adecarboxylata isolates were susceptible to both glycylcyclines. All other isolates were resistant to both glycylcyclines.ConclusionsIn both OXA-48 and NDM producers, the activity of the four antibiotics tested was better against E. coli than K. pneumoniae. Meropenem/vaborbactam provided better cover than imipenem/relebactam. Eravacycline and tigecycline showed similar activity to each other, but their activity was inferior compared with the β-lactam combinations, particularly against K. pneumoniae.

Comparative Genomic Analysis and Phenotypic Characterization of Bronchoscope-Associated Klebsiella aerogenes.

Bronchoscopes have been linked to outbreaks of nosocomial infections. The phenotypic and genomic profiles of bronchoscope-associated Klebsiella aerogenes isolates are largely unknown. In this work, a total of 358 isolates and 13 isolates were recovered from samples after clinical procedures and samples after decontamination procedures, respectively, over the five months. Antimicrobial susceptibility testing found seven K. aerogenes isolates exhibiting a low-level resistance to antimicrobial agents. Among seven K. aerogenes isolates, we found five sequence types (STs) clustered into three main clades. Collectively, this study described for the first time the phenotypic and genomic characteristics of bronchoscope-associated K. aerogenes.

Assessment of the in vitro activity of ceftazidime/avibactam against a global collection of multidrug-resistant Klebsiella spp. from the INFORM surveillance programme (2015–2017)

Infections caused by Klebsiella spp. are difficult to treat when these pathogens exhibit multidrug resistance (resistance to ≥3 drug classes). This study determined rates of multidrug-resistant (MDR) Klebsiella spp. among clinical isolates collected globally (Africa/Middle East, Asia, Oceania, Europe and Latin America, but not the USA) as part of the INFORM surveillance programme (2015-2017). In vitro antimicrobial activities of ceftazidime/avibactam (CAZ/AVI) and comparator antimicrobials against these MDR isolates were determined using CLSI broth microdilution methodology. MICs were interpreted using EUCAST 2019 breakpoints. By species, 38.4% (4555/11 864) of Klebsiella pneumoniae isolates were MDR, followed by 28.3% (452/1598) of Klebsiella aerogenes. The majority (69.5%) of MDR K. pneumoniae isolates were extended-spectrum β-lactamase (ESBL)-positive and carbapenemase-negative compared with 1.3% of MDR K. aerogenes. Globally, >92% of MDR K. pneumoniae isolates were resistant to amoxicillin/clavulanic acid, aztreonam, cefepime, ceftazidime or ceftriaxone. CAZ/AVI, colistin and tigecycline MIC90 values were 1-2 mg/L against the global collection of MDR K. pneumoniae and MDR K. aerogenes. Approximately 5% (216/4555) of all MDR K. pneumoniae isolates and 1.1% (5/452) of all MDR K. aerogenes isolates were resistant to CAZ/AVI. Rates of resistance to CAZ/AVI and colistin were low for MDR, ESBL-positive, carbapenemase-negative K. pneumoniae (0.1% and 3.0%, respectively). Resistance to CAZ/AVI was highest among MDR, carbapenemase-positive, metallo-β-lactamase (MBL)-positive K. pneumoniae (98.0%), whereas colistin resistance was highest among MDR, carbapenemase-positive, MBL-negative isolates (30.2%). The results of this study suggest that CAZ/AVI, colistin and tigecycline are potential treatment options for nosocomial infections caused by MDR Klebsiella spp. isolates.

221. Newly-Named Klebsiella aerogenes Is Associated with Poor Clinical Outcomes Relative to Enterobacter cloacae Complex in Patients with Bloodstream Infection

BackgroundWhole-genome-based comparative bacterial phylogenetics led to Enterobacter aerogenes being renamed Klebsiella aerogenes. It is unclear how infections with K. aerogenes differ from Enterobacter cloacae complex (Ecc) regarding clinical characteristics, antibiotic resistance, patient outcomes, and bacterial virulence genes.MethodsAdult inpatients with K. aerogenes or Ecc bloodstream infection (BSI) were prospectively enrolled at Duke from 2002–2015. Whole-genome bacteria sequencing was performed. Chi-squared, Fisher’s exact, Mann–Whitney U, t-tests, and multivariable logistic regression models identified risk factors for infection and clinical outcomes. PanOCT algorithm identified flexible genomic islands (fgi). Multidrug resistance (MDR) was defined as resistance to ≥3 drug classes and poor clinical outcome as death before discharge and/or BSI complication (septic shock, acute kidney injury, acute lung injury/acute respiratory distress syndrome, disseminated intravascular coagulation).ResultsWe identified 104 (69%) patients with Ecc BSI and 46 (31%) with K. aerogenes BSI (N = 150). Patients with Ecc BSI more often required hemodialysis (23% vs. 9%, P = 0.04). MDR was similar between Ecc and K. aerogenes (30% vs. 33%; P = 0.85). Total (21% vs. 28%; P = 0.3) and attributable in-hospital mortality (12% vs. 20%; P = 0.3) did not differ between the two genera. Poor clinical outcome was more common with K. aerogenes BSI (70% vs. 40%, P = 0.001) and remained significant after adjusting for age, source of BSI, site of acquisition (e.g., hospital), days to appropriate antibiotic, and chronic APACHE-II score (odds ratio 2.8, 95% CI 1.2–6.4, P = 0.001). Ecc and K. aerogenes isolates formed 14 and 3 phylogenetic clades, respectively (Fig 1A). K. aerogenes contained 983 core genes, grouped within 324 fgi, that were not present in Ecc (Fig 1B). These included homologs to virulence genes involved in iron acquisition, flagella synthesis, and fimbriae production.ConclusionPatients with BSI due to K. aerogenes had poor clinical outcomes relative to Ecc. Multiple unique K. aerogenes genes homologous to virulence factors may contribute to this difference. Disclosures All authors: No reported disclosures.