Susceptibility To Ceftriaxone Research Articles

Characterization of Antibiotic Resistance in Select Tertiary Hospitals in Uganda: An Evaluation of 2020 to 2023 Routine Surveillance Data.

Antimicrobial resistance (AMR) is a public health concern in Uganda. We sought to conduct an extended profiling of AMR burden at selected Ugandan tertiary hospitals. We analyzed routine surveillance data collected between October 2020 and March 2023 from 10 tertiary hospitals. The analysis was stratified according to the hospital unit, age, gender, specimen type, and time. Up to 2754 isolates were recovered, primarily from pus: 1443 (52.4%); urine: 1035 (37.6%); and blood: 245 (8.9%). Most pathogens were Staphylococcus aureus, 1020 (37%), Escherichia coli, 808 (29.3%), and Klebsiella spp., 200 (7.3%). Only 28% of Escherichia coli and 42% of the other Enterobacterales were susceptible to ceftriaxone, while only 44% of Staphylococcus aureus were susceptible to methicillin (56% were MRSA). Enterococcus spp. susceptibility to vancomycin was 72%. The 5-24-year-old had 8% lower ampicillin susceptibility than the >65-year-old, while the 25-44-year-old had 8% lower ciprofloxacin susceptibility than the >65-year-old. The 0-4-year-old had 8% higher ciprofloxacin susceptibility. Only erythromycin susceptibility varied by sex, being higher in males. Escherichia coli ciprofloxacin susceptibility in blood (57%) was higher than in urine (39%) or pus (28%), as was ceftriaxone susceptibility in blood (44%) versus urine (34%) or pus (14%). Klebsiella spp. susceptibility to ciprofloxacin and meropenem decreased by 55% and 47%, respectively, during the evaluation period. During the same period, Escherichia coli ciprofloxacin susceptibility decreased by 40%, while Staphylococcus aureus gentamicin susceptibility decreased by 37%. Resistance was high across the Access and Watch antibiotic categories, varying with time, age, sex, specimen type, and hospital unit. Effective antimicrobial stewardship targeted at the critical AMR drivers is urgently needed.

Clinical and microbiological profile of Viridans group streptococcal bacteraemia; experience from South India.

Viridans Group Streptococci (VGS) are a group of distinct species that can cause bacteraemia and other invasive infections. They are also among the common organisms causing infective endocarditis. Data on the epidemiology and clinical profile of VGS is limited, especially from India. We conducted an electronic medical record-based retrospective analysis of patients with VGS bacteraemia admitted to our hospital between January 2012 to December 2021. Blood cultures were incubated by BacT/ALERT system and bacterial identification and susceptibility testing were done by using the VITEK 2 microbial identification system. Susceptibility test reporting was as per Clinical and Laboratory Standards Institute (CLSI) guidelines. The incidence, clinical profile, source of bacteraemia, co-morbidities and antimicrobial resistance among VGS bacteraemia were analyzed. VGS were isolated in 219 patients, accounting for 3.2% of positive blood cultures during the period studied. The median age of the patients was 58 years and 69% were males. Diabetes mellitus was the most common co-morbidity (55%) followed by chronic kidney disease and chronic liver disease. Patients with haematological malignancy and neutropenia were few. Intra-abdominal infections were the most common source of infection and was noted in 26%. Infective endocarditis was diagnosed in only 10% of the cases. Streptococcus mitis was the most common species isolated followed by S. gallolyticus and S. sanguinis. 9.58% of the isolates could not be identified up to the species level. Overall penicillin susceptibility was 71% and ceftriaxone susceptibility was 92%, with individual species variation. In-hospital mortality was 19%. VGS are an important cause of bacteraemia and was associated with 19% mortality in our study. High rates of penicillin and ceftriaxone resistance are a reason of concern. Molecular diagnostics like matrix assisted laser desorption ionization-time of flight (MALDI-TOF) identification must be increasingly applied for species identification considering that a substantial number of isolates were not identified to species level.

Rapid determination of antimicrobial susceptibility of Gram-negative bacteria from clinical blood cultures using a scattered light-integrated collection device.

Background. A bloodstream infection (BSI) presents a complex and serious health problem, a problem that is being exacerbated by increasing antimicrobial resistance (AMR).Gap Statement. The current turnaround times (TATs) for most antimicrobial susceptibility testing (AST) methods offer results retrospective of treatment decisions, and this limits the impact AST can have on antibiotic prescribing and patient care. Progress must be made towards rapid BSI diagnosis and AST to improve antimicrobial stewardship and reduce preventable deaths from BSIs. To support the successful implementation of rapid AST (rAST) in hospital settings, a rAST method that is affordable, is sustainable and offers comprehensive AMR detection is needed.Aim. To evaluate a scattered light-integrated collection (SLIC) device against standard of care (SOC) to determine whether SLIC could accelerate the current TATs with actionable, accurate rAST results for Gram-negative BSIs.Methods. Positive blood cultures from a tertiary referral hospital were studied prospectively. Flagged positive Gram-negative blood cultures were confirmed by Gram staining and analysed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, Vitek 2, disc diffusion (ceftriaxone susceptibility only) and an SLIC device. Susceptibility to a panel of five antibiotics, as defined by European Committee on Antimicrobial Susceptibility Testing breakpoints, was examined using SLIC.Results. A total of 505 bacterial-antimicrobial combinations were analysed. A categorical agreement of 95.5 % (482/505) was achieved between SLIC and SOC. The 23 discrepancies that occurred were further investigated by the broth microdilution method, with 10 AST results in agreement with SLIC and 13 in agreement with SOC. The mean time for AST was 10.53±0.46 h and 1.94±0.02 h for Vitek 2 and SLIC, respectively. SLIC saved 23.96±1.47 h from positive blood culture to AST result.Conclusion. SLIC has the capacity to provide accurate AST 1 day earlier from flagged positive blood cultures than SOC. This significant time saving could accelerate time to optimal antimicrobial therapy, improving antimicrobial stewardship and management of BSIs.

Global trends in non-susceptibility rates of Streptococcus pneumoniae isolates to ceftriaxone: Data from the antimicrobial testing leadership and surveillance (ATLAS) programme, 2016–21

To understand the global changes in non-susceptibility rates of Streptococcus pneumoniae to ceftriaxone, we conducted a study using the Antimicrobial Testing Leadership and Surveillance database. A total of 15,717 S. pneumoniae isolates were collected from 2016 to 2021. The minimum inhibitory concentrations (MICs) were determined using broth microdilution. The overall susceptibility rates of S. pneumoniae isolates to penicillin, ceftriaxone and ceftaroline were 63.4%, 94.0% and 99.6%, respectively. The geometric mean of MICs and MIC50/MIC90 values of ceftriaxone were higher in Asia than in other continents. China (33.9%), South Korea (33.8%) and Taiwan (27.6%) had the highest ceftriaxone non-susceptibility rates, followed by Turkey, India, Brazil, Malaysia, South Africa and Colombia, with rates between 10% and 20%. During the study period from 2020 to 2021, Asia had the highest MIC90 value (4 mg/L) for ceftriaxone in S. pneumoniae isolates, and the geometric mean of MICs increased from 0.25 mg/L in 2016–2017 to 0.39 mg/L in 2020–2021. Both Asia (from 83.4% to 75.1%) and Latin America (from 94.2% to 86.3%) showed a decreasing trend in ceftriaxone susceptibility rates from 2016 to 2021. In North America, Europe and Oceania, the susceptibility rate was higher than 95%, and there was no obvious change in the rate during the 6 y. Further analysis of the data from Asia revealed that individuals younger than 6 y of age had a lower susceptibility rate to ceftriaxone (71.6% vs. 81.7%, P < 0.05) than patients ≥6 y. The higher non-susceptibility rates of ceftriaxone in S. pneumoniae in Asia may lead to therapeutic challenges in community-acquired pneumonia.

Comparative analysis of a rapid diagnostic test and scoring tools for ESBL detection in Enterobacterales bloodstream infections for optimizing antimicrobial therapy.

Our study addresses a significant issue in the medical and scientific community-the delayed administration of appropriate antimicrobial treatments due to the time-consuming process of phenotypic susceptibility data collection in gram-negative bloodstream infections. Our research indicates that a multiplex PCR rapid diagnostic test (RDT) significantly outperformed two clinical scoring tools in predicting ceftriaxone susceptibility. Multiplex PCR also led to reduced instances of undertreatment with ceftriaxone and minimized overtreatment with carbapenems. Furthermore, multiplex PCR demonstrated high sensitivity and specificity in predicting ceftriaxone susceptibility. The results of our study underscore the potential RDTs to reduce the time to appropriate antimicrobial therapy, leading to improved patient outcomes and reduced healthcare costs.

162. The Genotypic Antibiogram: Using Results of Gram-Negative Antimicrobial Resistance Genes Identified via Rapid Blood Culture Identification Tests to Optimize Treatment of Enterobacterales Bloodstream Infections

Abstract Background With the increasing incidence of infections from Enterobacterales resistant to commonly used antibiotics, rapid diagnostic tests, such as BioFire’s Blood Culture Identification 2 (BCID2) multiplex PCR panel, can be utilized to detect potential antimicrobial resistance more rapidly and help direct more appropriate empiric therapy. We describe the epidemiology of Enterobacterales bloodstream infection (BSI), associated antimicrobial resistance genes using BCID2, and subsequent susceptibility patterns at an academic medical center to develop a genotypic antibiogram. Methods We reviewed all positive BCID2 results at Nebraska Medical Center from 8/1/2021–11/1/2022. Only monomicrobial Enterobacterales BSI were included. Patient demographics, antimicrobial resistance markers, BCID2, culture, and susceptibility results were assessed. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of blaCTX-M marker were compared to ceftriaxone susceptibility patterns. Results We reviewed 456 unique Enterobacterales isolates, of which 236 were from male patients (52%), 189 (41%) immunocompromised patients, and 342 (75%) community onset. The most common species identified were Escherichia coli (55%) and Klebsiella pneumoniae (17%). blaCTX-M was detected in 49 (11%) isolates, with 41 (84%) E. coli and 6 (12%) K. pneumoniae. blaKPC was detected in 2 isolates (1 K. oxytoca and 1 K. variicola), but no other carbapenemase genes were detected. blaCTX-M sensitivity and specificity for detection of ceftriaxone resistance was 83% and 100%, respectively. blaCTX-M PPV for ceftriaxone resistance was 100%, while the NPV of absent blaCTX-M for ceftriaxone susceptibility was 97%. Conclusion Locally, the majority of ceftriaxone-resistant E. coli and Klebsiella BSIs harbor blaCTX-M, while carbapenemases are rare. Utilization of rapid diagnostics can optimize antimicrobial therapy for Enterobacterales by creation of a genotypic antibiogram. Disclosures Scott J. Bergman, PharmD, bioMerieux, Inc.: Honoraria Trevor C. Van Schooneveld, MD, FSHEA, FACP, AN2 Therapeutics: Grant/Research Support|Biomeriuex: Advisor/Consultant|Biomeriuex: Grant/Research Support|Insmed: Grant/Research Support|Thermo-Fischer: Honoraria

Bacitracin enhances ceftriaxone susceptibility of the high-level ceftriaxone-resistant gonococcal FC428 clone

ABSTRACT Neisseria gonorrhoeae is a multidrug-resistant bacterial pathogen for which ceftriaxone mono-antimicrobial therapy and ceftriaxone plus azithromycin dual-antimicrobial therapy are the only remaining effective therapies. However, ceftriaxone efficacy is threatened by the global dissemination of the high-level ceftriaxone-resistant FC428 clone, while azithromycin has in recent years been removed from the recommended dual therapy in some countries as a result of increasing (high-level) azithromycin resistance. Inclusion of an alternative second antimicrobial could be an effective strategy to protect ceftriaxone from (further) resistance development. In this study, we investigated gonococcal susceptibility to bacitracin and determined its synergistic anti-gonococcal activity with ceftriaxone. Gonococcal susceptibility to bacitracin was investigated for 449 contemporary clinical isolates using the agar dilution method. Bacitracin displayed consistent activity against the N. gonorrhoeae strain collection, with a minimum inhibitory concentration (MIC) range of 2–32 mg/L and a MIC 90 of 32 mg/L. Furthermore, bacitracin was bactericidal in time-kill assays, particularly against the tested FC428-associated isolate, which showed 10 5 -fold inactivation after 8 hours of exposure to a 4× MIC dose. Importantly, bacitracin and ceftriaxone displayed synergistic activity, with a fractional inhibitory concentration index ≤0.5 for the majority of tested strains. Finally, spot assays showed strong synergistic activity against the FC428-associated isolates, with up to 200-fold reduced plating efficacy for bacitracin combined with ceftriaxone compared with ceftriaxone only. In conclusion, bacitracin shows synergistic anti-gonococcal activity with ceftriaxone and might therefore be an interesting candidate for inclusion in a dual-antimicrobial therapy with ceftriaxone. IMPORTANCE Ceftriaxone-based antimicrobial therapies for gonorrhea are threatened by waning ceftriaxone susceptibility levels and the global dissemination of the high-level ceftriaxone-resistant gonococcal FC428 clone. Combination therapy can be an effective strategy to restrain the development of ceftriaxone resistance, and for that purpose, it is important to find an alternative antimicrobial to replace azithromycin, which has recently been removed in some countries from the recommended ceftriaxone plus azithromycin dual-antimicrobial therapy. Ideally, the second antimicrobial should display synergistic activity with ceftriaxone. We hypothesized that bacitracin might display synergistic activity with ceftriaxone because of their distinct mechanisms targeting bacterial cell wall synthesis. In this study, we showed that bacitracin indeed displays synergistic activity with ceftriaxone against Neisseria gonorrhoeae . Importantly, strains associated with the FC428 clone appeared to be particularly susceptible to the bacitracin plus ceftriaxone combination, which might therefore be an interesting dual therapy for further in vivo testing.

Safety Aspects and Rational Use of Single Intramuscular Dose Ceftriaxone: Clinical Insights on the Management of Uncomplicated Gonococcal Infections.

Gonorrhea, a sexually transmitted infection caused by Neisseria gonorrhoeae, is a grave public health concern. Gonorrhea is the second most reported sexually transmitted infection worldwide. The treatment of uncomplicated gonococcal infections has evolved dramatically in response to the emergence of antimicrobial resistance. Multiple resistance mechanisms (for example, beta-lactamase production, antimicrobial efflux, and target site modification) exist, some of which may cause multidrug-resistance. Ceftriaxone was first recommended as an option for uncomplicated gonococcal infections in 1985, and it is now a mainstay of therapy in all clinical practice guidelines. Ceftriaxone has consistently shown high microbiologic cure rates in clinical trials, and it has demonstrated an excellent safety profile. Although its use may be limited in patients with hypersensitivity to penicillins, the risk of using ceftriaxone in such patients is overestimated. The emergence of reduced ceftriaxone susceptibility in N. gonorrhoeae, coupled with a lack of diverse treatment alternatives and the limited pipeline of new antimicrobials, is a significant threat to the treatment of gonorrhea.

Machine learning to predict ceftriaxone resistance using single nucleotide polymorphisms within a global database of Neisseria gonorrhoeae genomes.

Antimicrobial resistance (AMR) in Neisseria gonorrhoeae is an urgent global health issue. Machine learning (ML) is a powerful tool that can aid in identifying mutations and predicting their impact on AMR. The study aimed to use ML models to predict ceftriaxone susceptibility and decreased susceptibility (S/DS). A public database of N. gonorrhoeae genomes with minimum inhibitory concentration (MIC) data was used to evaluate seven ML models using 97 single nucleotide polymorphisms (SNPs) known to be associated with ceftriaxone resistance. Ceftriaxone MICs ≤ 0.064 mg/L were classified as susceptible, and ceftriaxoneMICs > 0.064 mg/L were classified as DS. The contributions of individual SNPs to predict S/DS were calculated using SHapley Additive exPlanation (SHAP) values. An ML model was retrained using different combinations of SNPs with the highest SHAP values. The performance of ML models was assessed using different metrics including area under the curve (AUC) and balanced accuracy (bAcc). The ML analyses included 9,540 N. gonorrhoeae genomes; 368 (0.04%) were classified as DS. Of the models evaluated, the model trained with a random forest classifier had the highest performance (AUC 0.965; bAcc 0.926). A model retrained the top five SNPs, according to SHAP values, demonstrated a similar performance (AUC 0.916; bAcc 0.879) as the model with 97 SNPs. An ML approach using mutations in N. gonorrhoeae can be used to predict S/DS to ceftriaxone. The results highlight a practical application of ML to identify mutations most associated with S/DS to ceftriaxone, which can aid in the development of assays to predict AMR. IMPORTANCE Antimicrobial resistance in Neisseria gonorrhoeae is an urgent global health issue. The objectives of the study were to use a global collection of 12,936 N. gonorrhoeae genomes from the PathogenWatch database to evaluate different machine learning models to predict ceftriaxone susceptibility/decreased susceptibility using 97 mutations known to be associated with ceftriaxone resistance. We found the random forest classifier model had the highest performance. The analysis also reported the relative contributions of different mutations within the ML model predictions, allowing for the identification of the mutations with the highest importance for ceftriaxone resistance. A machine learning model retrained with the top five mutations performed similarly to the model using all 97 mutations. These results could aid in the development of molecular tests to detect resistance to ceftriaxone in N. gonorrhoeae. Moreover, this approach could be applied to building and evaluating machine learning models for predicting antimicrobial resistance in other pathogens.

Influence of adhesion force on croRS gene expression and antibiotic resistance of Enterococcus faecalis.

Surface properties of materials influence bacterial adhesion and play important roles in biofilm antibiotic resistance. The two-component system CroRS of Enterococcus faecalis (E. faecalis) can be activated by antibiotics and is involved in cephalosporin resistance. We hypothesized that surfaces properties could influence the expression of croRS in E. faecalis biofilm and contribute to cephalosporin resistance. In this study, the hydrophobicity of poly-ethylene (PE) and stainless steel (SS) was characterized. Adhesion forces were measured using atomic force microscopy. The transcript levels of croRS in E. faecalis adhering to surfaces exerting different adhesion forces were compared, in presence and absence of cephalosporin. The ceftriaxone susceptibility of E. faecalis biofilms was investigated using colony forming units (CFU) counting. The water contact angles of PE and SS were 97.1 ± 0.3° and 33.5 ± 0.3°, respectively (p < .05). The adhesion force of E. faecalis on PE was 7.6 ± 1.0 nN, which was higher than that on SS surfaces (3.5 ± 0.5 nN, p < .05). The gene expression of croS and croR in E. faecalis was higher on PE compared to that on SS (p < .05). E. faecalis on the hydrophobic PE surfaces, exerting stronger adhesion force, was more resistant to ceftriaxone compared to that on more hydrophilic SS surfaces. Results revealed the surface properties of materials can modulate the expression of croRS system and interfere with the outcome of antimicrobial therapy of E. faecalis biofilm. The modification of surface properties of biomedical devices may be used as a strategy to increase the efficacy of antimicrobial therapy.

Combined mutations of the penA with ftsX genes contribute to ceftriaxone resistance in Neisseria gonorrhoeae and peptide nucleic acids targeting these genes reverse ceftriaxone resistance

To investigate the gene mutations associated with ceftriaxone (CRO) resistance among gonococcal isolates, and to determine the effects of the mutated genes on CRO minimum inhibitory concentrations (MICs) with transformation assays and antisense peptide nucleic acids (asPNAs). Ceftriaxone-resistant (CROR) and ceftriaxone-susceptible (CROS) isolates were identified using EUCAST and paired according to similarity in their MICs to other antimicrobials. The two groups of gonococci were sequenced and analysed. Mutated genes that showed a statistical difference between the two groups were transformed into gonococcal reference strains to determine their functions. AsPNAs were designed and transformed into the former transformant to further confirm the effects of the mutated genes. Twenty-two paired CROR and CROS isolates were obtained. The incidence of the penA-A501T and penA-G542S mutations individually, as well as combined mutations (penA-A501T and ftsX-R251H, penA-G542S and ftsX R251H), was statistically different between the two groups. The MIC of ATCC43069 (A43) increased 2 times following transformation with penA-A501T, and the MICs of A43 and ATCC49226 (A49) increased 32 times and 2 times following transformation with penA-A501T and ftsX-R251H, respectively. Antisense PNA-P3 reduced the MIC of the A43 transformant most significantly when transformed individually. PNA-P3 and PNA-F1 (asPNAs of the penA and ftsX) restored CRO susceptibility. PenA-A501T and penA-G542S mutations are important in CRO resistance among gonococci isolates. The ftsX-R251H mutation is also related to CRO resistance, and combined mutations of ftsX-R251H and penA-A501T comediate a significant reduction in CRO susceptibility. The combined application of PNA-P3 and PNA-F1 could effectively reverse the resistance to CRO in N. gonorrhoeae.

Antimicrobial Susceptibility of E. coli Isolates from Intra-Abdominal Infections in the Asia-Pacific Region: Trends in Ciprofloxacin, Ceftriaxone, Cefepime, and Piperacillin/Tazobactam Susceptibility.

To investigate the antibiotic susceptibility of Escherichia coli isolates in patients diagnosed with intra-abdominal infections (IAIs) in the Asia-Pacific region. This study was conducted at 50 medical hospitals across 9 countries/regions as part of the Study for Monitoring Antimicrobial Resistance Trends (SMART) surveillance program from 2014 to 2018. Nonduplicate isolates of aerobic and facultative gram-negative bacilli were collected and processed for further antimicrobial susceptibility testing. A total of 10,709 isolates were collected, with E. coli (n=4737, 44.2%) being the leading pathogen causing IAIs, followed by Klebsiella pneumoniae (n=2429, 22.7%) and Pseudomonas aeruginosa (n=931, 8.7%). Community-associated (CA) E. coli isolates generally exhibited higher susceptibility rates for most antibiotics than hospital-associated (HA) isolates. In countries/regions other than Hong Kong, South Korea, and Singapore, HA isolates displayed lower susceptibility rates for multiple classes (≥4) of antibiotics. Among the commonly used antibiotics in IAIs, the overall susceptibility rate for ciprofloxacin was low, with an average of 41.3%. Ceftriaxone susceptibility rates in all selected countries were below 80% starting in 2018, ranging from 23.3% to 75.8%. The cefepime susceptibility rates varied across regions, with consistently reduced susceptibility ranging from 45.5% to 57.8% in India, Thailand, and Vietnam. Piperacillin/tazobactam demonstrated effectiveness against E. coli isolates in almost all countries except India, with a downward trend observed in the Philippines and Taiwan. Carbapenems remained effective against more than 90% of E. coli isolates, except in India. Prudent use of fluoroquinolones and ceftriaxone is advised when treating both CA and HA IAIs in the Asia-Pacific region. The low susceptibility rate of cefepime in India, Thailand, and Vietnam needs careful consideration in its administration. Moreover, the increase in nonsusceptibility to piperacillin/tazobactam in the Philippines and Taiwan poses a potential risk that should be closely monitored.

Penicillin-Susceptible Streptococcus pneumoniae Meningitis in Adults: Does the Ceftriaxone Dosing Matter?

The recommended empiric ceftriaxone dosing regimen for acute bacterial meningitis in adults is 2 g every 12 h. After penicillin-susceptible Streptococcus pneumoniae is isolated as a causative microorganism, the ceftriaxone dose may be continued or reduced to a single dose of 2 g every 24 h, per institutional preference. There is no clear guidance that indicates the superiority of one regimen over the other. The objective of this study was to evaluate the susceptibility of S. pneumoniae in the cerebral spinal fluid (CSF) of patients with meningitis and the relationship between ceftriaxone dose and clinical outcomes. We identified 52 patients with S. pneumoniae meningitis with positive CSF cultures who were treated at the University Hospital, Bern, Switzerland, over a 19-year period. We collected clinical and microbiological data for evaluation. Broth microdilution and Etest methods were performed to test penicillin and ceftriaxone susceptibility. All isolates were susceptible to ceftriaxone. Ceftriaxone was empirically used in 50 patients, with a starting dosing regimen of 2 g every 24 h in 15 patients and 2 g every 12 h in 35 patients. In 32 patients started on a twice-daily regimen (91%), doses were reduced to once daily after a median of 1.5 (95% CI 1-2) days. The overall in-hospital mortality was 15.4% (n = 8), and 45.7% of patients reported at least one sequela of meningitis at the last follow-up (median 375, 95% CI 189-1585 days). We found no statistical difference in outcome between the 2 g every 24 h and the 2 g every 12 h ceftriaxone dosing regimens. A ceftriaxone total daily dose of 2 g may be associated with similar outcomes to a 4 g total daily dose, provided that the causative organism is highly susceptible to ceftriaxone. The persistence of neurological and infection sequelae at the last follow-up underscores the need for optimal treatment of these complex infections.

Rapid Molecular Phenotypic Antimicrobial Susceptibility Test for Neisseria gonorrhoeae Based on Propidium Monoazide Viability PCR.

Neisseria gonorrhoeae (NG) is an urgent threat to antimicrobial resistance (AMR) worldwide. NG has acquired rapid resistance to all previously recommended treatments, leaving ceftriaxone monotherapy as the first and last line of therapy for uncomplicated NG. The ability to rapidly determine susceptibility, which is currently nonexistent for NG, has been proposed as a strategy to preserve ceftriaxone by using alternative treatments. Herein, we used a DNA-intercalating dye in combination with NG-specific primers/probes to generate qPCR cycle threshold (Ct) values at different concentrations of 2 NG-relevant antimicrobials. Our proof-of-concept dual-antimicrobial logistic regression model based on the differential Ct measurements achieved an AUC of 0.93 with a categorical agreement for the susceptibility of 84.6%. When surveying the performance against each antimicrobial separately, the model predicted 90 and 75% susceptible and resistant strains, respectively, to ceftriaxone and 66.7 and 83.3% susceptible and resistant strains, respectively, to ciprofloxacin. We further validated the model against the individual replicates and determined the accuracy of the model in classifying susceptibility agnostic of the inoculum size. We demonstrated a novel PCR-based approach to determine phenotypic ciprofloxacin and ceftriaxone susceptibility information for NG with reasonable accuracy within 30 min, a significant improvement compared to the conventional method which could take multiple days.

Increased clonality among Neisseria gonorrhoeae isolates during the COVID-19 pandemic in Amsterdam, the Netherlands.

Distancing measures during the COVID-19 lockdown led to a temporary decrease of casual sex partners among clients of the Centre for Sexual Health (CSH) in Amsterdam, the Netherlands. We investigated the effect of this change on the genotypic and phenotypic distribution of Neisseria gonorrhoeae (Ng) isolates from CSH patients. From each Ng-positive patient we sequenced one isolate, resulting in 322 isolates which constituted two groups: 181 isolates cultured from 15 January to 29 February 2020 (before the first lockdown) and 141 cultured from 15 May to 30 June 2020 (during the first lockdown). Patient characteristics showed significantly more symptomatic patients and significantly fewer reported sex partners during the lockdown. Phenotypic data showed an increase in low-level azithromycin resistance and ceftriaxone susceptibility during the lockdown, and this remained after the study period. The diversity in sequence types (STs) decreased slightly during the lockdown. A shift occurred from ST 8156 being predominant before lockdown to ST 9362 during lockdown and a remarkably low median SNP distance of 17 SNPs was found between ST 9362 isolates obtained during lockdown. These findings reflect restricted travel and the change in sexual behaviour of CSH clients during the lockdown, with a potentially increased local transmission of the ST 9362 strain during this period, which led to genotypic and phenotypic changes in the Ng population. This shows that public health measures have far-reaching consequences and should be considered in the surveillance of other infectious diseases.

Antimicrobial susceptibility of bacterial isolates from clinical specimens in four Pacific Island countries, 2017–2021

There are limited antimicrobial resistance (AMR) surveillance data from low- and middle-income countries, especially from the Pacific Islands region. AMR surveillance data is essential to inform strategies for AMR pathogen control. We performed a retrospective analysis of antimicrobial susceptibility results from the national microbiology laboratories of four Pacific Island countries - the Cook Islands, Kiribati, Samoa and Tonga - between 2017 and 2021. We focused on four bacteria that have been identified as 'Priority Pathogens' by the World Health Organization: Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa. Following deduplication, a total of 20,902 bacterial isolates was included in the analysis. The most common organism was E.coli (n=8455) followed by S.aureus (n=7830), K.pneumoniae (n=2689) and P.aeruginosa (n=1928). The prevalence of methicillin resistance among S.aureus isolates varied between countries, ranging from 8% to 26% in the Cook Islands and Kiribati, to 43% in both Samoa and Tonga. Ceftriaxone susceptibility remained high to moderate among E.coli (87%-94%) and K.pneumoniae (72%-90%), whereas amoxicillin+clavulanate susceptibility was low against these two organisms (50%-54% and 43%-61%, respectively). High susceptibility was observed for all anti-pseudomonal agents (83%-99%). Despite challenges, these Pacific Island laboratories were able to conduct AMR surveillance. These data provide valuable contemporary estimates of AMR prevalence, which will inform local antibiotic formularies, treatment guidelines, and national priorities for AMR policy. Supported by the National Health and Medical Research Council.

Global Transmission of the penA Allele 60.001–Containing High-Level Ceftriaxone-Resistant Gonococcal FC428 Clone and Antimicrobial Therapy of Associated Cases: A Review

Abstract Neisseria gonorrhoeae is a multidrug-resistant bacterial pathogen for which ceftriaxone is the only remaining recommended first-line therapy. However, ceftriaxone susceptibility has been waning in a number of countries over the last decade and ceftriaxone treatment failures have been reported, commonly as a result of sporadic high-level ceftriaxone-resistant strains. In recent years, N. gonorrhoeae strains associated with the high-level ceftriaxone-resistant FC428 clone or strains that acquired its main ceftriaxone resistance determinant, penA allele 60.001, have shown global transmission, resulting in ceftriaxone treatment failure in a number of cases. The FC428 clone was first encountered in Japan in 2015 and subsequently in China, Europe, Australia, North America and Southeast Asia afterward. Strains associated with the FC428 clone commonly display a ceftriaxone minimum inhibitory concentration of 0.5–1 mg/L. However, where penA alleles encountered in sporadic high-level ceftriaxone-resistant isolates induce an in vitro growth defect, penA allele 60.001 does not seem to affect in vitro growth. The limited impact of penA allele 60.001 on biological fitness might be associated with its successful global transmission. Although the FC428 clone displays high-level ceftriaxone resistance, most gonorrhea cases associated with this clone were still successfully cured with ceftriaxone when intramuscular or intravenous doses of 500 mg to 2 g were used. A successful alternative therapy seems to be ertapenem given at 1-g doses, although further clinical studies are required to validate ertapenem efficacy. This review summarizes the global transmission of strains associated with the FC428 clone and antimicrobial treatment of associated cases.

P21 A novel, fast, impedance-based antimicrobial susceptibility test for Neisseria gonorrhoeae

Abstract Objectives To demonstrate that the impedance-based fast antimicrobial susceptibility test (iFAST) can define N. gonorrhoeae susceptibility for a range of frontline antibiotics, and determine time taken to see responses. Background Gonorrhoea is the second most common bacterial sexually transmitted infection in the UK. It can cause complicated infection and infertility if not treated effectively. Resistance to frontline treatments and MDR N. gonorrhoeae infections (‘super gonorrhoea’) are increasing, fuelled by inappropriate selection of antibiotics. The current gold-standard antimicrobial susceptibility test (AST) for N. gonorrhoeae is MIC agar dilution, which is time-consuming (∼7 days) and labour-intensive. Unemo et al. 2020 (https://doi.org/10.1093/jac/dkw288) published detailed resistance profiles of WHO-reference N. gonorrhoeae strains. This project aimed to test whether these strain sensitivities against front line antibiotics ceftriaxone, ciprofloxacin and azithromycin could be defined faster using iFAST, which calculates the opacity and electrical size of individual cells by measuring change in electrical currents as single cells flow between micro-electrodes. Antibiotic-treated susceptible bacteria change electrical radius (surrogate measure of cell size) and opacity (based on properties of bacterial membranes as resistors), compared with untreated or resistant cells (Spencer et al. 2020, 10.1038/s41467-020-18902-x). Methods N. gonorrhoeae WHO-reference strains F and X were incubated overnight on standard chocolate agar plates at 37°C, 3%–5% CO2. 10 viable plate colonies were selected and inoculated in 37°C brain heart infusion media, supplemented with 0.42% sodium bicarbonate and 1% Isovitalex. After 30 min incubation at 37°C with shaking, the cell concentration was measured on iFAST and added to five concentrations of ceftriaxone, ciprofloxacin, and azithromycin (at the published agar MIC and ±2 × 2-fold concentration) or at EUCAST susceptibility breakpoint concentrations (strains F, X, O, V, K, Y), at a final cell concentration of 5 × 105 cells/mL. Cells were exposed at 37°C 250 rpm for 2, 3 and 4 h. 60 µL of 1:10 dilutions of sample were read on iFAST. MATLAB analysis software created contours around 50% of untreated cells and overlayed this on exposed population scattergrams. Results Electrical MICs (eMICs) showed differences in cell count, electrical radius and opacity between cells exposed to concentrations ≥MIC, subinhibitory concentrations, or untreated cells for all three frontline drugs. These differences were detectable after 2 h of antibiotic exposure but were clearest after 4 h. When tested at breakpoint concentrations only, iFAST accurately detected susceptibility of tested N. gonorrhoeae reference strains after 4 h exposure. Generally, susceptible cells had reduced electrical cell size and increased opacity distribution (out of contour shift) for all compounds, though there was variation due to differing modes of action. Ciprofloxacin and azithromycin had more decreased electrical cell radius with increased opacity spread. Comparatively, ceftriaxone had smaller changes in electrical radius and a larger spread of opacity readings. Conclusions iFAST is potentially a rapid and accurate method for determining N. gonorrhoeae strain susceptibility for ceftriaxone, ciprofloxacin, and azithromycin. With additional validation, it may be useful for future N. gonorrhoeae AST development, as well as investigating the effect of novel antimicrobial compounds.

1836. Frequency and Antimicrobial Susceptibility of Gram-negative Bacteria Isolated from Patients with Bloodstream Infections in United States (US) Medical Centers (2020-2021)

Abstract Background Antimicrobial resistance among Gram-negative bacteria (GNB) is a major problem in US hospitals. The development of various β-lactamase inhibitor combinations (BLICs) markedly increased the armamentarium to treat infections caused by GNB in recent years. We evaluated the frequency and antimicrobial susceptibility of GNB causing bloodstream infection (BSI). Methods 5,796 organisms were consecutively collected (1/patient) from patients with BSI in 31 US medical centers in 2020-2021. The collection included 2,893 (49.9%) GNB, which were susceptibility tested against ceftazidime-avibactam (CAZ-AVI), ceftolozane-tazobactam (C-T), meropenem-vaborbactam (MEM-VAB), imipenem-relebactam (IMI-REL), and many comparators by CLSI broth microdilution method. Enterobacterales (ENT) isolates with an ESBL phenotype were screened for β-lactamase genes by whole genome sequencing. Results The most common GNBs were E. coli (41.9%), K. pneumoniae (16.1%), P. aeruginosa (10.2%), and E. cloacae (6.8%). Ceftriaxone susceptibility rates were 80.1%, 82.9%, and 74.0% for E. coli, K. pneumoniae, and E. cloacae, respectively. CAZ-AVI and MEM-VAB showed almost complete activity (≥ 99.7%) against ENT, whereas IMI-REL exhibited limited activity against P. mirabilis and indole-positive Proteeae isolates and C-T showed limited activity against E. cloacae, ESBL-phenotype, and multidrug-resistant (MDR) isolates (Table). CAZ-AVI, MEM-VAB, and IMI-REL were active against 84.2%, 57.9%, and 52.6% of carbapenem-resistant ENT (CRE) isolates, respectively. PSA susceptibility to PIP-TAZ, MEM, and CAZ were 86.1%, 88.5%, and 88.5%, respectively. CAZ-AVI (97.6% susceptible [S]), C-T (97.6%S), IMI-REL (99.0%S), and tobramycin (TOB; 98.3%S) were the most active agents against PSA and retained good activity against piperacillin-tazobactam (PIP-TAZ) nonsusceptible (NS), MEM-NS, and multidrug-resistant (MDR) isolates. Conclusion CAZ-AVI and MEM-VAB were the most active agents against ENT and CAZ-AVI; C-T and IMI-REL were the most active BLICs against PSA. The new BLICs represent valuable treatment options for infections caused by MDR GBNs. CAZ-AVI exhibited a more balanced spectrum against ENT and PSA when compared to other BLICs. Disclosures Helio S. Sader, MD, PhD, AbbVie: Grant/Research Support|Cidara: Grant/Research Support|Melinta: Grant/Research Support|Nabriva Therapeutics: Grant/Research Support|Pfizer: Grant/Research Support Rodrigo E. Mendes, PhD, AbbVie: Grant/Research Support|Cidara: Grant/Research Support|GSK: Grant/Research Support|Melinta: Grant/Research Support|Nabriva Therapeutics: Grant/Research Support|Office for Assistant Secretary of Defense for Health Affairs: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support|Spero Therapeutics: Grant/Research Support Cecilia G. Carvalhaes, MD, PhD, AbbVie: Grant/Research Support|Cidara: Grant/Research Support|Melinta: Grant/Research Support|Pfizer: Grant/Research Support Michael D. Huband, BS, AbbVie: Grant/Research Support|Melinta: Grant/Research Support Dee Shortridge, PhD, AbbVie: Grant/Research Support|JMI Laboratory: Employee|Melinta: Grant/Research Support|Menarini: Grant/Research Support|Shionogi: Grant/Research Support Mariana Castanheira, PhD, AbbVie: Grant/Research Support|Cidara: Grant/Research Support|GSK: Grant/Research Support|Melinta: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support.

1231. Microbial Profile of Biliary Stent, Bile and Surgical Site Cultures in Pancreaticoduodenectomy Patients – Implications for Surgical Prophylaxis

Abstract Background Surgical site infection (SSI) rates post pancreaticoduodenectomy (PD) range from 20 to 40%. Biliary obstruction (± stent in situ) leads to colonization of the biliary tract with gut flora, and bile contamination during surgery increases SSI risk. Current guidelines recommend surgical prophylaxis (ppx) with 1st or 2nd generation cephalosporins. However, emerging data favor targeted ppx based on biliary cultures to reduce SSI. We reviewed the microbial profile of pathogens isolated from perioperative biliary stent and bile cultures, and evaluated the impact of ppx on culture positive SSIs within 30 days of PD. Methods This was a retrospective study conducted in Singapore General Hospital. Patients who had PD from 1/1/2013 to 31/12/2019 were included. The first positive cultures from perioperative biliary stent, bile, and SSI cultures obtained within 30 days of surgery were reviewed. Antibiotic use 30 days prior and during surgery was collected. Results A total of 341 patients with a mean age of 63.9 ± 11.3 years were included; 202 (59.2%) were male and 137 (40.2%) received antibiotics in the past 30 days. For surgical ppx, patients received either cephalosporins ± metronidazole (216 [63.3%] ceftriaxone, 25 [7.3%] cefazolin), piperacillin-tazobactam (TZP) (35 [10.3%)], ciprofloxacin ± metronidazole (16 [4.7%)] or other antibiotics (14 [4.1%]), while 35 had missing data. Of the positive cultures from 84 biliary stent, 86 bile and 79 SSI, the most common organisms isolated were Enteroccocus spp., E. coli, Klebsiella spp., Enterobacter spp. and Candida spp. Ceftriaxone susceptibility rates in E. coli were 50.0%, 54.8% and 22.2% in biliary stent, bile and SSI cultures respectively; similarly low rates were also seen in Klebsiella spp. (Tables 1-3). Antibiotic use 30-days prior was associated with higher ceftriaxone resistance rates in E. coli and Klebsiella spp. from bile cultures (70.8% vs 36.4%, p=0.019). In patients with biliary stents cultured, use of TZP ppx showed a trend towards lower rates of culture positive SSIs compared to non-TZP ppx (9.1% vs 29.4%, p=0.054). Conclusion Our local gram-negative bacteria susceptibility rates to ceftriaxone are low in biliary stent, bile fluid cultures, and even lower for SSI post PD. Antibiotic ppx for PD in high-risk patients may need to be broadened. Disclosures All Authors: No reported disclosures.