Ceftriaxone MICs Research Articles

In Vitro Activity of Ertapenem against Neisseria gonorrhoeae Clinical Isolates with Decreased Susceptibility or Resistance to Extended-Spectrum Cephalosporins in Nanjing, China (2013 to 2019).

ABSTRACTNeisseria gonorrhoeae isolates collected in Nanjing, China, that possessed decreased susceptibility (or resistance) to extended-spectrum cephalosporins (ESCs) were examined for susceptibility to ertapenem, and their sequence types were determined. Ceftriaxone and cefixime MICs of ≥0.125 mg/L and ≥0.25 mg/L, respectively, were first determined in 259 strains isolated between 2013 and 2019, and then MICs of ertapenem were measured using the antimicrobial gradient Epsilometer test (Etest). Also, genetic determinants of ESC resistance were identified and N. gonorrhoeae multiantigen sequence typing (NG-MAST) was performed to analyze associations with ertapenem susceptibility. All isolates displayed ertapenem MICs between 0.006 mg/L and 0.38 mg/L; the overall MIC50 and MIC90 were 0.032 mg/L and 0.125 mg/L, respectively. Forty-four (17.0%) isolates displayed ertapenem MICs of ≥0.125 mg/L; 10 (3.9%) had MICs of ≥0.25 mg/L. The proportion of isolates with ertapenem MICs of ≥0.125 mg/L increased from 4.0% in 2013 to 20.0% in 2019 (χ2 = 24.144, P < 0.001; chi-square test for linear trend). The penA mosaic allele was present in a significantly higher proportion of isolates with ertapenem MICs of ≥0.125 mg/L than of isolates with MICs of ≤0.094 mg/L) (97.7% versus 34.9%, respectively; χ2 = 58.158, P < 0.001). ST5308 was the most prevalent NG-MAST type (8.5%); ST5308 was also significantly more common among isolates with ertapenem MICs of ≥0.125 mg/L than isolates with MICs of ≤0.094 mg/L (22.7% and 5.6%, respectively; χ2 = 13.815, P = 0.001). Ertapenem may be effective therapy for gonococcal isolates with decreased susceptibility or resistance to ESCs and isolates with identifiable genetic resistance determinants.

Antimicrobial susceptibility testing and molecular characterization of Neisseria gonorrhoeae in Tehran, Iran.

Gonorrhea is a sexually transmitted infection occurring worldwide. Antimicrobial resistance (AMR) surveillance in Neisseria gonorrhoeae and associated molecular epidemiological studies are crucial to ascertain the spread of antibiotic-resistant and developing the local treatment guidelines. This study was performed to determine the antimicrobial susceptibility testing (AST) and molecular epidemiology of N. gonorrhoeae isolates in Tehran, Iran. During 1 July 2018-30 July 2020, a total of 500 urogenital (468 endocervical, 32 urethral) swabs were collected from patients with signs and symptoms of genitourinary infections presenting to two women's hospitals and one health center located center and south of Tehran. Specimens were cultured and examined for the presence of N. gonorrhoeae isolates by biochemical tests. MIC Test Strip determined the MICs of ceftriaxone, azithromycin, and ciprofloxacin. Neisseria gonorrhoeae multiantigen sequence typing (NG-MAST) was also performed. A total of 38N. gonorrhoeae isolates were identified. The proportions of resistant N. gonorrhoeae isolates were as follows: ceftriaxone (MIC ≥0.125μg/mL) 10.5% (4/38), azithromycin (MIC >1μg/mL) 34% (13/38), and ciprofloxacin (MIC ≥1μg/mL) 31.5% (12/38). In total, 25 different NG-MAST STs were identified. The STs comprised 1-4 isolates each, and the predominant ST was ST266 (n = 4). Our study demonstrates a diverse gonococcal population with high rates of resistance to azithromycin and evidence of resistance to ceftriaxone. The results have potential implications for antibiotic choice for the gonococcal treatment and highlight the need to broaden gonococcal AMR monitoring in Iran.

Reliability of Genetic Alterations in Predicting Ceftriaxone Resistance in Neisseria gonorrhoeae Globally.

ABSTRACTAntimicrobial resistance in N. gonorrhoeae is increasing globally, and ceftriaxone is the recommended treatment for empirical therapy in most settings. Developing molecular assays to detect decreased ceftriaxone susceptibility is critical. Using PathogenWatch, a public database of N. gonorrhoeae genomes, antibiotic susceptibility data and DNA sequences of different genes associated with ceftriaxone resistance were extracted. That information was used to determine the sensitivity and specificity of different molecular markers and algorithms to predict decreased susceptibility to ceftriaxone. A total of 12,943 N. gonorrhoeae genomes were extracted from the PathogenWatch database, of which 9,540 genomes were used in the analysis. The sensitivity and specificity of specific molecular markers and algorithms were largely consistent with prior reports. Small variation (<10%) in either sensitivity or specificity occurred. Certain algorithms using different molecular markers at various prevalence of decreased ceftriaxone susceptibility identified a potentially clinically useful range of positive and negative predictive values. We validated previously described mutations and algorithms in a large public database containing a global collection of N. gonorrhoeae genomes. Certain mutations and algorithms resulted in sensitivity and specificity values consistent with those of prior studies. Further research is needed to integrate these markers and algorithms into the development of molecular assays to predict decreased ceftriaxone susceptibility.IMPORTANCE Antimicrobial resistance in Neisseria gonorrhoeae (N. gonorrhoeae), the causative agent of gonorrhea, is rising globally. Ceftriaxone is the last remaining antibiotic for empirical treatment of gonorrhea. Developing molecular tests to predict ceftriaxone resistance can help to improve detection and surveillance of ceftriaxone resistance. Here, we utilized PathogenWatch, a public global online database of N. gonorrhoeae genomes, to evaluate different genetic markers in predicting decreased susceptibility to ceftriaxone. We compiled MICs for ceftriaxone from the PathogenWatch database and used a computational approach to extract all the genetic markers from the genomic data. We determined the sensitivity and specificity for predicting decreased ceftriaxone susceptibility among several combinations of genetic markers. We identified several combinations of genetic markers with high predictive values for decreased susceptibility to ceftriaxone. These combinations of genetic markers might be promising candidates for future molecular tests to predict ceftriaxone resistance.

First characterisation of antimicrobial susceptibility and resistance of Neisseria gonorrhoeae isolates in Qatar, 2017–2020

Limited data are available regarding antimicrobial resistance in Neisseria gonorrhoeae strains circulating in WHO Eastern Mediterranean Region (EMR). We investigated the antimicrobial susceptibility/resistance of N. gonorrhoeae isolates to five antimicrobials (ceftriaxone, azithromycin, ciprofloxacin, tetracycline, and benzylpenicillin) currently or previously used for gonorrhoea treatment in Qatar, 2017–2020. Minimum inhibitory concentrations (MICs; mg/L) of antimicrobials were determined using Etest on gonococcal isolates collected during January 1, 2017-August 30, 2020 at Hamad Medical Corporation, a national public healthcare provider. During 2017–2020, resistance in isolates from urogenital sites of 433 patients was 64.7% (95% CI: 59.5–69.6%; range: 43.9–78.7%) for ciprofloxacin, 50.7% (95% CI: 45.3–56.1%; range: 41.3–70.4%) for tetracycline, and 30.8% (95% CI: 26.3–35.6%; range: 26.7–35.8%) for benzylpenicillin. Percentage of isolates non-susceptible to azithromycin was 4.1% (95% CI: 2.0–7.4%; range: 2.7–4.8%) and all (100%) isolates were susceptible to ceftriaxone. Two (1.6%) isolates from 2019 and one (2.2%) isolate from 2020 had high-level resistance to azithromycin (MIC≥256 mg/L). Overall, 1.0% (4/418) of isolates had a ceftriaxone MIC of 0.25 mg/L, which is at the ceftriaxone susceptibility breakpoint (MIC≤0.25 mg/L). Treatment with ceftriaxone 250 mg plus azithromycin 1 g can continuously be recommended for gonorrhoea therapy in Qatar. Continued quality-assured gonococcal AMR surveillance is warranted in EMR.

151. Simplifying Empiric Antimicrobial Therapy Selection for Lower Respiratory Tract Infections in Intensive Care Unit Patients: Using Resistance Frequency to Guide Decision Making

BackgroundIn the US, the burden of multidrug resistant bacterial infections, including carbapenem-resistant P. aeruginosa (CRPA) and ESBL-producing Enterobacterales (ESBL-E), is substantial. These resistant pathogens may affect the delivery of timely effective therapy. The aim of this study is to evaluate beta-lactam (BL) susceptibility trends based on the aggregate frequency of CRPA and a combined ESBL-E phenotype (K. pneumoniae (KPn) + E. coli (EC)) observed in critically ill patients with lower respiratory tract infections (LRTI).MethodsIn 2016-2019, ~20 US institutions per year submitted up to 250 gram-negative pathogens as part of the Study for Monitoring Antimicrobial Resistance Trends. A total of 871 PA, 380 KPn, and 336 EC isolates were collected from ICU patients with LRTI. MICs were determined using broth microdilution and interpreted using 2021 CLSI breakpoints. ESBL-E phenotype was defined as: ceftriaxone MIC ≥ 2 mcg/mL. Institutions were stratified into two groups based on frequency of CRPA and combined ESBL-E phenotype: Group 1: CRPA ≤ 15% and ESBL-E ≤ 15%; Group 2: CRPA > 15% and ESBL-E > 15%. Based on CLSI guidance, an empiric antibiotic susceptibility threshold of ≥90% was deemed optimal.ResultsOverall, CRPA and ESBL-E phenotypes were identified in 28.4% and 21.2% of isolates, respectively. Aggregate BL susceptibility in group 1 was above the 90% threshold for cefepime (FEP), piperacillin/tazobactam (TZP), meropenem (MEM), ceftolozane/tazobactam (C/T), and imipenem/relebactam (I/R) (Table 1). However, as frequency of CRPA and ESBL-E exceeded 15%, aggregate BL susceptibility declined to 77.3%, 79.3%, and 86.2% for FEP, TZP, and MEM, respectively. In contrast, C/T and I/R maintain susceptibility above the empiric susceptibility threshold.Table 1. Aggregate susceptibility of P. aeruginosa, E. coli, and K. pneumoniae ICU LRTI isolates stratified by resistance frequency: Best- (Group 1) and worst-case (Group 2) scenarios ConclusionIn ICU patients, exceeding CRPA and combined ESBL-E phenotype frequency of 15% for both classifications, impacts susceptibility to 1st line BL’s resulting in a failure to achieve empiric susceptibility thresholds. This stratification could serve as a decision point for triggering earlier susceptibility testing or modifying empiric therapy recommendations for LRTI to include newer agents pending microbiology results.Disclosures Kenneth Klinker, PharmD, Merck & Co., Inc. (Employee, Shareholder) Levita K. Hidayat, PharmD BCIDP, Merck & Co., Inc. (Employee, Shareholder) C. Andrew DeRyke, PharmD, Merck & Co., Inc. (Employee, Shareholder) Mary Motyl, PhD, Merck & Co., Inc. (Employee, Shareholder) Karri A. Bauer, PharmD, Merck & Co., Inc. (Employee, Shareholder)

949. Risk Factors for Subsequent Multidrug-Resistant Gram-Negative Bloodstream Infection Following an Initial Gram-Negative Bloodstream Infection among Solid Organ Transplant Recipients

Abstract Background Multidrug-resistant (MDR) Gram-negative (GN) bloodstream infections (BSI) are a major cause of morbidity and mortality among solid organ transplant recipients (SOTR). We determined risk factors associated with subsequent MDR-GN BSI following an initial Enterobacterales (EB) BSI among SOTRs. Methods A retrospective cohort study was performed. All SOTR with an EB BSI at the Hospital of the University of Pennsylvania and University of Maryland Medical Center between 1 Jan 2007 and 30 June 2018 and The Johns Hopkins Hospital between 1 Jan 2005 and 31 Dec 2015 were included. The primary outcome was any MDR-GN BSI within 60 days of the EB BSI, including MDR-EB (defined by ceftriaxone MIC ≥8μg/mL), and MDR-Pseudomonas and Acinetobacter (defined by resistance to three or more antibiotic classes). Unadjusted analyses were performed to identify possible risk factors, using a Fisher’s exact or χ 2 test for categorical and Student’s t-test for continuous variables. Results Of 988 SOTR with an EB BSI, 138 (14%) had a MDR-GN BSI within 60 days. In unadjusted analyses, possible risk factors for a subsequent MDR-GN BSI (Table 1) included: (1) an index BSI due to extended-spectrum beta-lactamase (ESBL)-producing EB (compared to a susceptible index EB BSI); (2) a carbapenem-resistant EB (CRE) index BSI (compared to a susceptible index EB BSI); (3) exposure to piperacillin-tazobactam or carbapenems in the 6 months prior to the index EB BSI; (4) prior liver transplantation; and (5) need for reoperation within four weeks of the original transplantation. There was no significant association between recurrent MDR-GN BSI and immunosuppression at time of infection, induction immunosuppression history, acute rejection history, or primary graft dysfunction. Table 1. Risk factors for subsequent MDR-GN BSI following EB BSI among SOTR. Data are presented as numbers (percentages) except where noted. Abbreviations: BSI, bloodstream infection; CRE, carbapenem-resistant Enterobacterales; EB, Enterobacterales; ESBL, extended-spectrum beta-lactamase; GN, Gram-negative; IQR, interquartile range; MDR, multidrug-resistant Conclusion This study shows that liver transplantation, reoperation following transplantation, an index ESBL-EB or CRE BSI, and recent exposure to broad-spectrum beta-lactam antibiotics are associated with an increased odds of subsequent MDR-GN BSI in SOTR, and underscores the need for future studies aimed at preventing emergence of MDR-GN infections in this vulnerable population. Disclosures Jennifer Han, MD, MSCE, GlaxoSmithKline (Employee, Shareholder) Ebbing Lautenbach, MD, MPH, MSCE, Merck (Other Financial or Material Support, Member of Data and Safety Monitoring Board (DSMB)) Pranita Tamma, MD, MHS, Nothing to disclose Emily Blumberg, MD, Amplyx (Other Financial or Material Support, Member of Data and Safety Monitoring Board (DSMB))Hologic (Research Grant or Support)Merck (Grant/Research Support, Other Financial or Material Support, Member of Scientific Advisory Committee)Takeda (Research Grant or Support, Other Financial or Material Support, Member of Scientific Advisory Committee) Judith A. Anesi, MD, MSCE, Nothing to disclose

1289. The Challenge of Treating Community-Associated Enterobacterales Infections in a Middle-Income Country: Data from SMART 2018-2019

BackgroundAntimicrobial stewardship programs have been used widely in hospital settings due to the rise of resistant bacteria, antibiotic toxicities, and costs. Nevertheless, few efforts are done to prevent the rising antimicrobial resistance in community settings. The aim of our study was to evaluate the antimicrobial resistance from Enterobacterales community- and hospital-acquired infections in Southern Brazil.MethodsA total of 272 Enterobacterales isolates (i.e., Escherichia coli, Klebsiella spp., Citrobacter spp., Enterobacter spp., Serratia spp., Proteus spp., and Providencia) were collected from 2018 and 2019. Broth microdilution method was used to determine minimum inhibitory concentrations for ceftriaxone, cefepime, levofloxacin, amikacin and ertapenem. Molecular evaluation of beta-lactamases (ESBLs, AmpC, and KPC) was also performed.ResultsNinety-three, and a hundred and seventy-nine isolates were from community- and hospital-acquired infections, respectively. Similar MIC distribution was found between community and hospital settings (Table 1). Levofloxacin MIC of 8mg/L occurred in 38.7% (n=36) and 30.7% (n=55) of isolates from community- and hospital-acquired infections, respectively (Figure 1). Ceftriaxone MIC of 16mg/L occurred in 39.7%(n=37) and 39.1% (n=70) of isolates from community- and hospital-acquired infections, respectively (Figure 1). At last, cefepime MIC of 32mg/L occurred in 22% (n=21) and 25% (n=46) of isolates from community- and hospital-acquired infections, respectively. The following beta-lactamases were found in isolates from community-acquired group, ACT-MIR, CTX-M, SHV and TEM; while beta-lactamases from the hospital-acquired group were ACT-MIR, CMY II, KPC-2, CTX-M, SHV and TEM. Table 1. Enterobacterales ceftriaxone, cefepime, levofloxacin, amikacin and ertapenem minimum inhibitory concentrations (mg/L) distribution from community- and hospital-settings. Figure 1. Enterobacterales ceftriaxone and levofloxacin minimum inhibitory concentrations (mg/L) distribution from community- and hospital-settings.ConclusionSimilar antimicrobials resistances were found in Enterobacterales from community- and hospital-acquired infections. New anti-infective agents are needed urgently to treat pathogens from the community-acquired infections and hospitals that have resistance to the first line regimen. Additionally, community antimicrobial stewardship programs are required.Disclosures All Authors: No reported disclosures

Linear Regression Equations To Predict β-Lactam, Macrolide, Lincosamide, and Fluoroquinolone MICs from Molecular Antimicrobial Resistance Determinants in Streptococcus pneumoniae.

ABSTRACTAntimicrobial resistance in Streptococcus pneumoniae represents a threat to public health, and monitoring the dissemination of resistant strains is essential to guiding health policy. Multiple-variable linear regression modeling was used to determine the contributions of molecular antimicrobial resistance determinants to antimicrobial MICs for penicillin, ceftriaxone, erythromycin, clarithromycin, clindamycin, levofloxacin, and trimethoprim-sulfamethoxazole. Training data sets consisting of Canadian S. pneumoniae isolates obtained from 1995 to 2019 were used to generate multiple-variable linear regression equations for each antimicrobial. The regression equations were then applied to validation data sets of Canadian (n = 439) and U.S. (n = 607 and n = 747) isolates. The MICs for β-lactam antimicrobials were fully explained by amino acid substitutions in motif regions of the penicillin binding proteins PBP1a, PPB2b, and PBP2x. Accuracies of predicted MICs within 1 doubling dilution to phenotypically determined MICs were 97.4% for penicillin, 98.2% for ceftriaxone, 94.8% for erythromycin, 96.6% for clarithromycin, 98.2% for clindamycin, 100% for levofloxacin, and 98.8% for trimethoprim-sulfamethoxazole, with an overall sensitivity of 95.8% and specificity of 98.0%. Accuracies of predicted MICs to the phenotypically determined MICs were similar to those of phenotype-only MIC comparison studies. The ability to acquire detailed antimicrobial resistance information directly from molecular determinants will facilitate the transition from routine phenotypic testing to whole-genome sequencing analysis and can fill the surveillance gap in an era of increased reliance on nucleic acid assay diagnostics to better monitor the dynamics of S. pneumoniae.

In Vitro Synergism of Penicillin and Ceftriaxone against Enterococcus faecalis.

Enterococcus faecalis infective endocarditis is commonly treated with intravenous ampicillin/ceftriaxone combination therapy. Ampicillin, however, is unsuitable for outpatient parenteral antibiotic therapy (OPAT) regimens due to its instability in 24 h continuous infusors, and has been successfully replaced by benzylpenicillin used together with ceftriaxone in a few small case series. Since in vitro synergy data of penicillin/ceftriaxone against E. faecalis are still lacking, checkerboard assays were performed for 28 clinical E. faecalis isolates and one laboratory standard strain. Synergistic effects (both lowest and median FICI) were observed for penicillin/ceftriaxone in 15/29 isolates, while ampicillin/ceftriaxone exhibited synergism in 22/29 isolates. For isolates with ceftriaxone MICs ≤ 256 mg/L, the addition of free ceftriaxone trough concentrations to penicillin or ampicillin resulted in comparable synergistic effects for both combinations. In contrast, for isolates with ceftriaxone MICs ≥ 512 mg/L free ceftriaxone trough concentrations were only sufficient to exhibit synergistic effects in combination with ampicillin, but not penicillin. This study suggests that benzylpenicillin/ceftriaxone would be expected to be suitable for the OPAT treatment of enterococcal endocarditis for E. faecalis isolates with ceftriaxone MICs ≤ 256 mg/L. However, combination therapy would be expected to provide no advantage over benzylpenicillin monotherapy for isolates with ceftriaxone MICs ≥ 512 mg/L. Further investigation is required to analyse the relationship between ceftriaxone susceptibility and penicillin/ceftriaxone synergy, especially for isolates with ceftriaxone MICs of 64 to 512 mg/L.

Prediction of ceftriaxone MIC inNeisseria gonorrhoeae usingDNA microarray technology and regression analysis

Decreased susceptibility of Neisseria gonorrhoeae to extended-spectrum cephalosporins is a major concern. Elucidation of the phenotypic and genetic characteristics of such isolates is a priority task. We developed a method for predicting the N. gonorrhoeae ceftriaxone susceptibility level (MICcro) by identifying genetic determinants of resistance using low-density hydrogel microarrays and a regression equation. A training dataset, containing 5631 isolates from the Pathogenwatch database and 181 isolates obtained in the Russian Federation during 2018-19, was used to build a regression model. The regression equation was tested on 14 WHO reference strains. Ceftriaxone resistance determinants for the 448 evaluated clinical isolates collected in Russia were identified using microarray analysis, and MICcro values were calculated using the regression equation and compared with those measured by the serial dilution method. The regression equation for calculating MICcro values included 20 chromosomal resistance determinants. The greatest contributions to the increase in MICcro were shown to be PBP2: Ala-501→Pro, Ala-311→Val, Gly-545→Ser substitutions, Asp(345-346) insertion; and PorB: Gly-120→Arg substitution. The substitutions PBP2: Ala-501→Thr/Val, PorB: Gly-120→Asn/Asp/Lys and PBP1: Leu-421→Pro had weaker effects. For 94.4% of the isolates in the evaluation set, the predicted MICcro was within one doubling dilution of the experimentally determined MICcro. No ceftriaxone-resistant isolates were identified in the analysed samples from Russia, and no interpretative errors were detected in the MICcro calculations. The developed strategy for predicting ceftriaxone MIC can be used for the continuous surveillance of known and emerging resistant N. gonorrhoeae isolates.

Retrospective Analysis of Drug Sensitivity of Neisseria gonorrhoeae in Teaching Hospitals of South China.

The aim of this study was retrospective analysis of drug sensitivity of Neisseria gonorrhoeae in two teaching hospitals of South China. A total of 304 Neisseria gonorrhoeae isolates obtained from patients in South China from 2016 to 2020 were evaluated. The MICs of penicillin, cefuroxime, ceftriaxone (CRO), cefepime, ciprofloxacin, ceftazidime and azithromycin (AZM) against the isolates were determined by the agar dilution method. Then, Neisseria gonorrhoeae isolates were categorized into sensitive, moderately sensitive and resistant according to MICs. Also, β-lactamases were detected by enzyme linked immunosorbent assay (ELISA). Ureaplasma urealyticum and Mycoplasma hominis were determined by culture in liquid medium, and Chlamydia was detected by rapid antigen test. The result showed there was 50.99%, 20.72%, 9.87%, 14.47%, 86.84%, 7.57%, 6.91%, 11.18% resistance to penicillin, cefuroxime, ceftriaxone, cefepime, ciprofloxacin, ceftazidime and azithromycin, respectively. Also, β-lactamase positivity was 53.29% and Chlamydia antigen positivity was 20.07%. Ureaplasma urealyticum and Mycoplasma hominis positivity was 11.84% and 6.25%, respectively. From 2016 to 2020, the resistant rate of ceftriaxone and azithromycin gradually increased. In conclusion, Southern China is among the area reporting gonococci with high-level resistance to AZM and CRO, so N. gonorrhoeae culture and drug sensitivity test will be vital for monitoring trends in antimicrobial resistance.

Molecular characterization of decreased susceptibility to ceftriaxone and genotyping of Neisseria gonorrheae isolates in New Delhi, India

Data on genetic characteristics of Neisseria gonorrhoeae isolates exhibiting decreased susceptibility to extended-spectrum cephalosporins in India is deficient. In this study, we have sequenced penA, porB, mtrR and ponA and blaTEM genes in 70 clinical isolates of NG with varying ceftriaxone MICs. Amongst these, 22 (31.4%) were PPNG. Additionally, N. gonorrheae Multiantigen Sequence Typing was performed. Fisher exact and χ2 were used to evaluate significance of mutations with MICs. A total of six non-mosaic penA (Penicillin binding protein 2 [PBP2]) amino acid patterns were seen (II, IV, IX, XII, XIX, XXII) of which, pattern IX was significantly associated with decreased susceptibility to ceftriaxone. Other significant associations were noted in porB & mtrR genes. There were no mutations in blaTEM gene. ST6069 was significantly associated with decreased susceptibility to ceftriaxone. To conclude, development of decreased susceptibility to ceftriaxone in gonococci involves cumulation of different mutations in the four chromosomal genes investigated.

Molecular characterization of Neisseria gonorrhoeae isolates collected through a national surveillance programme in Japan, 2013: evidence of the emergence of a ceftriaxone-resistant strain from a ceftriaxone-susceptible lineage.

To investigate the spread of ceftriaxone-resistant Neisseria gonorrhoeae lineages similar to strains H041 (2009) and FC428 (2015), we characterized 55 strains collected in 2013 from hospitals across Japan. Susceptibility testing and whole-genome sequencing. Susceptibility rates were 58% for cefixime and 98% for ceftriaxone. The 55 strains were whole-genome sequenced and classified into nine MLST-STs. MLST-ST1901 was the most prevalent (n = 19) followed by MLST-ST7363 (n = 12) and MLST-ST7359 (n = 11). The most prevalent penA [encoding penicillin binding protein 2 (PBP2)] mosaic types, based on the N. gonorrhoeae sequence typing for antimicrobial resistance (NG-STAR) scheme, were 10.001 (n = 20) followed by 34.001 (n = 13). The H041 and FC428 strains were not detected; however, a single ceftriaxone-resistant strain (TUM15748) with a MIC of 0.5 mg/L ceftriaxone was identified. The TUM15748 strain belonged to MLST-ST7359 and N. gonorrhoeae multiantigen sequence typing-ST6771, and had a novel PBP2 (PBP2TUM15748, penA type 169.001). The amino acid sequence of PBP2TUM15748 showed partial similarity to that of PBP2 from N. gonorrhoeae GU140106 and commensal Neisseria perflava and Neisseria cinerea. Natural transformation and recombination experiments using full-length TUM15748 penA showed that the ceftriaxone MICs of transformants increased 16-fold or more compared with the parental ceftriaxone-susceptible recipient strain (NG9807, belonging to MLST-ST7363). No ceftriaxone-resistant MLST-ST7359 strains have previously been reported. We showed here that a ceftriaxone-susceptible lineage acquired a mutant PBP2 mosaic type, integrating partial PBP2 sequences from commensal Neisseria species, resulting in the emergence of ceftriaxone-resistant strains.

PRO: Testing for ESBL production is necessary for ceftriaxone-non-susceptible Enterobacterales: perfect should not be the enemy of progress.

The MERINO trial has seemingly laid to rest the question: ‘Are carbapenems the preferred therapy for ESBL-producing infections?’ It has, however, brought another important question to the forefront: ‘How do we know when we have an ESBL-producing infection?’ A commonly used approach is the interpretation that non-susceptibility to third-generation cephalosporins (e.g. ceftriaxone MICs of ≥2 mg/L) is an accurate proxy for ESBL production. We believe that relying on antibiotic susceptibility results alone to predict ESBL production in clinical isolates is fraught with issues. Rather, we believe accurate molecular assays that detect a comprehensive range of ESBL genes, along with other relevant β-lactamase genes, are well within the reach of existing technology and necessary to optimize patient care. Herein, we elaborate on why the current approach for determining whether an organism is likely to be an ESBL producer (i) is inaccurate; (ii) encourages carbapenem overuse; (iii) ignores the potential for ESBL production in other Enterobacterales species; and (iv) promotes the silent epidemic of ESBL transmission.

Third-generation cephalosporin resistance in clinical isolates of Enterobacterales collected between 2016–2018 from USA and Europe: genotypic analysis of β-lactamases and comparative in vitro activity of cefepime/enmetazobactam

This study aimed to investigate third-generation cephalosporin (3GC) resistance determinants [extended-spectrum β-lactamases (ESBLs), AmpC β-lactamases and OXA-type β-lactamases] in contemporary clinical Enterobacterales isolates and to determine the in vitro activity of β-lactams and β-lactam/β-lactamase inhibitor combinations, including the investigational combination of cefepime and the novel β-lactamase inhibitor enmetazobactam. Antibacterial susceptibility of 7168 clinical Enterobacterales isolates obtained between 2016-2018 from North America and Europe was determined according to CLSI guidelines. Phenotypic resistance to the 3GC ceftazidime (MIC ≥ 16 µg/mL) and/or ceftriaxone (MIC ≥ 4 µg/mL) but retaining susceptibility to meropenem (MIC ≤ 1 µg/mL) was determined. β-Lactamase genotyping was performed on clinical isolates with ceftazidime, ceftriaxone, cefepime or meropenem MIC ≥ 1 µg/mL. Phenotypic resistance to 3GCs occurred in 17.5% of tested isolates, whereas 2.1% of isolates were resistant to the carbapenem meropenem. Within the 3GC-resistant subgroup, 60.1% (n=752) of isolates encoded an ESBL, 25.6% (n=321) encoded an AmpC-type β-lactamase and 0.9% (n=11) encoded an OXA-type β-lactamase. Susceptibility of the subgroup to piperacillin/tazobactam (57.5%) and ceftolozane/tazobactam (71.3%) was <90% based on breakpoints established by the CLSI. Projected susceptibility to cefepime/enmetazobactam was 99.6% when applying the cefepime susceptible, dose-dependent breakpoint of 8 µg/mL. Against ESBL-producing isolates (n=801) confirmed by genotyping, only susceptibility to meropenem (96.0%) and cefepime/enmetazobactam (99.9%) exceeded 90%. This study describes the antibacterial activity of important therapies against contemporary 3GC-resistant clinical Enterobacterales isolates and supports the development of cefepime/enmetazobactam as a carbapenem-sparing option for ESBL-producing pathogens.

High susceptibility to zoliflodacin and conserved target (GyrB) for zoliflodacin among 1209 consecutive clinical Neisseria gonorrhoeae isolates from 25 European countries, 2018.

Novel antimicrobials for treatment of gonorrhoea are imperative. The first-in-class spiropyrimidinetrione zoliflodacin is promising and currently in an international Phase 3 randomized controlled clinical trial (RCT) for treatment of uncomplicated gonorrhoea. We evaluated the in vitro activity of and the genetic conservation of the target (GyrB) and other potential zoliflodacin resistance determinants among 1209 consecutive clinical Neisseria gonorrhoeae isolates obtained from 25 EU/European Economic Area (EEA) countries in 2018 and compared the activity of zoliflodacin with that of therapeutic antimicrobials currently used. MICs of zoliflodacin, ceftriaxone, cefixime, azithromycin and ciprofloxacin were determined using an agar dilution technique for zoliflodacin or using MIC gradient strip tests or an agar dilution technique for the other antimicrobials. Genome sequences were available for 96.1% of isolates. Zoliflodacin modal MIC, MIC50, MIC90 and MIC range were 0.125, 0.125, 0.125 and ≤0.004-0.5 mg/L, respectively. The resistance was 49.9%, 6.7%, 1.6% and 0.2% to ciprofloxacin, azithromycin, cefixime and ceftriaxone, respectively. Zoliflodacin did not show any cross-resistance to other tested antimicrobials. GyrB was highly conserved and no zoliflodacin gyrB resistance mutations were found. No fluoroquinolone target GyrA or ParC resistance mutations or mutations causing overexpression of the MtrCDE efflux pump substantially affected the MICs of zoliflodacin. The in vitro susceptibility to zoliflodacin was high and the zoliflodacin target GyrB was conserved among EU/EEA gonococcal isolates in 2018. This study supports further clinical development of zoliflodacin. However, additional zoliflodacin data regarding particularly the treatment of pharyngeal gonorrhoea, pharmacokinetics/pharmacodynamics and resistance selection, including suppression, would be valuable.

What's left in the cupboard? Older antimicrobials for treating gonorrhoea.

Neisseria gonorrhoeae has developed resistance to all antimicrobials used to treat gonorrhoea, with even ceftriaxone being undermined. It is therefore important to examine any potential to redeploy older antimicrobials routinely used for other infections to treat ceftriaxone-resistant gonococcal infections. We examined the susceptibility of N. gonorrhoeae to aztreonam, chloramphenicol, co-trimoxazole, fosfomycin, piperacillin/tazobactam and rifampicin. N. gonorrhoeae isolates (n = 94) were selected to include a range of antimicrobial susceptibilities: 58 were collected in the Gonococcal Resistance to Antimicrobials Surveillance Programme; 17 were clinical isolates referred to the PHE reference laboratory; and 19 were control strains. MICs were determined by agar dilution for the six study antimicrobials and for ceftriaxone and azithromycin as comparators. There was correlation between piperacillin/tazobactam and ceftriaxone MICs, but all five isolates with high ceftriaxone MICs (>0.5 mg/L) were inhibited by piperacillin/tazobactam at 0.06-0.5 mg/L. Aztreonam MICs for ceftriaxone-resistant isolates exceeded those of ceftriaxone. Among non-β-lactams, fosfomycin and co-trimoxazole had low, tightly clustered MICs, suggesting widespread susceptibility, rifampicin split the collection into highly susceptible and highly resistant groups and chloramphenicol had a wide MIC distribution. Although unsuitable for empirical use, piperacillin/tazobactam, fosfomycin, co-trimoxazole, rifampicin and, possibly, chloramphenicol could be considered for individual patients with ceftriaxone-resistant gonococcal infection once MICs are known. Wider surveillance of the susceptibility of N. gonorrhoeae to these agents is needed, along with clinical trials and the establishment of clinical breakpoints for N gonorrhoeae.

Current profile and management of gonococcal infections: A population-based study in Western France

ObjectiveTo characterize the current profile of gonococcal infections in France, and to describe their management. Patients and methodA population-based retrospective study of all gonococcal infections documented by PCR in two French departments (Île-et-Vilaine, Morbihan), in 2014–2016. Cases were identified through hospital databases and the Rénago sentinel network. ResultsWe enrolled 245 patients (96 females, 149 males), with a median age of 25 years [interquartile range, 21–33]. The incidence rate was estimated at 4.54 per 100,000 inhabitants-year. Cases were diagnosed mostly by a general practitioner (n=122, 49.8%) or a gynecologist (n=45, 18.4%). The main clinical presentations included urethritis (n=59), pelvic inflammatory disease (n=40), cervicitis (n=12), and anorectitis (n=11). The main coinfections were Chlamydia trachomatis (n=40) and HIV (n=8). Ceftriaxone MIC was≤0.12mg/L in 146/147 patients with positive culture. Treatment was appropriate in 52/74 (70.2%) patients with available data. ConclusionsIn France, general practitioners are at the front line in management of gonococcal infections.

High percentage of the ceftriaxone-resistantNeisseria gonorrhoeaeFC428 clone among isolates from a single hospital in Hangzhou, China

Ceftriaxone is currently the last-remaining empirical antimicrobial therapy for treatment of gonorrhoea. However, the high-level ceftriaxone-resistant gonococcal FC428 clone has shown transmission in China in recent years. Therefore, the aim of this study was to analyse ceftriaxone resistance among a collection of recent clinical isolates, with a specific focus on prevalence of the FC428 clone. A total of 70 consecutive gonococcal isolates were collected between May and October 2019 from a single hospital in Hangzhou, China, and analysed for antimicrobial susceptibility by the agar dilution method. STs were determined by PCR and sequences and isolates related to the FC428 clone were further characterized by WGS and phylogenetic analysis. Ceftriaxone resistance (MIC >0.125 mg/L) was observed in 21 (30%) isolates, while 14 (20%) isolates displayed a ceftriaxone MIC of 0.125 mg/L. Importantly, seven (10%) isolates were related to the gonococcal FC428 clone based on the presence of mosaic penA allele 60.001, displaying identical or closely related STs, and phylogenetic analysis after WGS. These seven isolates displayed high-level ceftriaxone resistance (MIC = 1 mg/L) and all associated gonorrhoea cases resulted in treatment failure because oral cephalosporins were initially prescribed. Subsequent re-treatment with a higher dose (2 g) of IV ceftriaxone appeared to be successful because all patients returning for test-of-cure became culture-negative. Here, we report a high percentage of the internationally spreading gonococcal FC428 clone among clinical isolates from a single hospital in Hangzhou, China. A high dose of ceftriaxone is currently the only recommended and effective therapy.

1373. Vaccine Effectiveness and Pneumococcal Serotypes in Pediatric Otitis Media in the Era of Routine 13-valent Pneumococcal Vaccination in the United States

BackgroundPneumococcal acute otitis media (AOM) in children due to vaccine related serotypes (St) declined after the introduction of the 13-valent pneumococcal conjugate vaccine (PCV13).MethodsPatients < 18 years with pneumococcal OM isolates from 2014-2019 from the U S Pediatric Multicenter Pneumococcal Surveillance Group were analyzed for demographics, immunization status, antimicrobial susceptibility and St distribution. p< 0.05 was considered statistically significant. Vaccine effectiveness (VE) was calculated using a standard formula: 1-([PCV13St vaccinated (≥3 PCV13 doses) x Non-PCV13St unvaccinated (0-1 PCV13 doses)]/[PCV13St unvaccinated x Non-PCV13St vaccinated])Results646 patients were identified. Patients with PCV13 St were older compared to patients with non-PCV13 serotypes (3.3 vs 1.5 median years, p< 0.0001). Most isolates were from spontaneous drainage (71.4 %) and PE tube placements (26.9%). 36 different Sts were identified; 83.4% of isolates were non-PCV13 Sts; 35B represented 18.3% of all isolates. St 19A decreased over time (p=0.0003). 14% of isolates had penicillin MIC ≥2 µg/ml and 2.4% had ceftriaxone MIC >1 µg/ml. (Figure) 633 patients had known vaccine status. VE was 86.4% (Table).Table. Vaccine Effectiveness 0-1 Doses of PCV13 3 or More Doses of PCV13 PCV13 serotype 39 59 Non-PCV13 serotypes 41 456 VE: 86.4%, 95%CI 77.2%-91.9%FigureAntimicrobial susceptibility to penicillin and ceftriaxoneConclusionNon-PCV13 Sts caused most pneumococcal OM. St35B was the most common St. St 19A decreased as a cause of otitis. In this study the VE of≥3 PCV13 doses was 86% for pneumococcal OM.Disclosures Tina Q. Tan, MD, Pfizer (Grant/Research Support, Other Financial or Material Support, Chair, DMSB for PCV20 vaccine) Pia S. Pannaraj, MD, MPH, AstraZeneca (Grant/Research Support)Pfizer (Grant/Research Support)Sanofi Pasteur (Advisor or Review Panel member) Sheldon L. Kaplan, MD, Allergan (Research Grant or Support)Pfizer (Grant/Research Support)