Antimicrobial Susceptibility Data Research Articles

Evolutionary genomic analyses of canine E. coli infections identify a relic capsular locus associated with resistance to multiple classes of antimicrobials.

Much of the human genomic epidemiology data available for E. coli mechanism discovery studies has been heavily biased toward shiga-toxin producing strains from humans and livestock. E. coli occupies many niches and produces a wide variety of other significant pathotypes, including some implicated in chronic disease. We hypothesized that since dogs tend to share similar strains with their owners and are treated with similar antibiotics, their pathogenic isolates will harbor unexplored AMR mechanisms of importance to humans as well as animals. By comparing over 1,000 genomes with in vitro antimicrobial susceptibility data from sick dogs across the US and Canada, we identified a strong multidrug resistance association with an operon that appears to have once conferred a type 1 capsule production system.

Creative usage of Vivli’s Antimicrobial Resistance Surveillance Open Data through the Re-Use Data Challenge

The escalation of infections caused by drug-resistant bacteria worldwide poses a formidable challenge to global health, necessitating innovative approaches to combat this issue. In 2022, Vivli launched the Antimicrobial Resistance (AMR) Register, a platform that consolidates antimicrobial susceptibility data from pharmaceutical industry surveillance programs. This register provides a freely available and fully searchable user-friendly repository to facilitate scientific understanding of resistance patterns and support development of innovative strategies to address AMR globally. To promote the register’s utility, raise AMR awareness and encourage further re-use of the available data, Wellcome funded the Vivli AMR Surveillance Open Data Re-Use Data Challenge in 2023. This data challenge successfully fostered diverse, impactful, and innovative solutions that leveraged the AMR Register data to contribute to resolving the AMR crisis. The outcomes of the initiative underscore the importance of access to open data in stimulating collaboration and innovation in the public health domain, particularly in combatting the growing threat of drug-resistant infections.

Best Practice of Peritoneal Dialysis-Associated Gram-Negative Peritonitis in Children: Insights From the International Pediatric Peritoneal Dialysis Network Registry

Gram-negative peritonitis (GNP) is associated with significant morbidity in children receiving long-term peritoneal dialysis (PD) and current treatment recommendations are based on limited data. Analysis of 379 GNP episodes in 308 children (median age 6.9 years, interquartile range [IQR]: 3.0-13.6) from 45 centers in 28 countries reported to the International Pediatric Peritoneal Dialysis Network registry between 2011 and2023. Overall, 74% of episodes responded well to empiric therapy and full functional recovery (FFR) was achieved in 82% of cases. Invitro bacterial susceptibility to empiric antibiotics and lack of severe abdominal pain at onset were associated with a good initial response. Risk factors for failure to achieve FFR included severe abdominal pain at onset and at 60 to 72 hours from treatment initiation (odds ratio [OR]: 3.81, 95% confidence interval [CI]: 2.01-7.2 and OR: 3.94, 95% CI: 1.06-14.67, respectively), Pseudomonas spp. etiology (OR: 1.73, 95% CI: 1.71-4.21]) and invitro bacterial resistance to empiric antibiotics (OR: 2.40, 95% CI: 1.21-4.79); the risk was lower with the use of monotherapy as definitive treatment (OR: 0.40, 95% CI: 0.21-0.77). Multivariate analysis showed no benefit of dual antibiotic therapy for treatment of Pseudomonas peritonitis after adjustment for age, presenting symptomatology, 60 to 72-hour treatment response, and treatment duration. Monotherapy with cefazolin in susceptible Enterobacterales peritonitis resulted in a similar FFR rate (91% vs. 93%) as treatment with ceftazidime or cefepime monotherapy. Detailed microbiological assessment, consisting of patient-specific and center-specific antimicrobial susceptibility data, should guide empiric treatment. Treatment "deescalation" with the use of monotherapy and narrow spectrum antibiotics according to susceptibility data is not associated with inferior outcomes and should be advocated in the context of emerging bacterial resistance.

Corynebacterium diphtheriae and Corynebacterium ulcerans: development of EUCAST methods and generation of data on which to determine breakpoints.

Evidence-based clinical susceptibility breakpoints have been lacking for antimicrobial agents used for diphtheria. We aimed to evaluate broth microdilution and disc diffusion methods and create a dataset of MIC values and inhibition zone diameters (ZDs) from which breakpoints could be determined. We included 400 recent clinical isolates equally distributed by species (Corynebacterium diphtheriae and Corynebacterium ulcerans) and by national surveillance programmes (France and Germany). Non-duplicate toxigenic and non-toxigenic isolates were chosen to enable the inclusion of a diversity of susceptibility levels for the 13 agents tested. Broth microdilution and disc diffusion, using EUCAST methodology for fastidious organisms, were used. The distributions of MIC and ZD values were largely in agreement among methods and countries. Breakpoints to allow categorization of WT isolates as susceptible, i.e. susceptible (S) or susceptible, increased exposure (I) were determined for 12 agents. The data supported a breakpoint for benzylpenicillin and amoxicillin of resistant (R) > 1 mg/L since WT isolates were inhibited by 1 mg/L or less. WT isolates were categorized as I (S ≤ 0.001 mg/L) for benzylpenicillin, emphasizing the need for increased exposure, and S (S ≤ 1 mg/L) for amoxicillin. Erythromycin breakpoints were set at S ≤ 0.06 mg/L and R > 0.06 mg/L. The corresponding ZD breakpoints were determined for all agents except amoxicillin, for which categorization was based on benzylpenicillin results. This work provided a large set of antimicrobial susceptibility data for C. diphtheriae and C. ulcerans, using a harmonized methodology. The dataset allowed EUCAST and experts in the diphtheria field to develop evidence-based breakpoints in January 2023.

Predictive Modeling of Phenotypic Antimicrobial Susceptibility of Selected Beta-Lactam Antimicrobials from Beta-Lactamase Resistance Genes.

The outcome of bacterial infection management relies on prompt diagnosis and effective treatment, but conventional antimicrobial susceptibility testing can be slow and labor-intensive. Therefore, this study aims to predict phenotypic antimicrobial susceptibility of selected beta-lactam antimicrobials in the bacteria of the family Enterobacteriaceae from different beta-lactamase resistance genotypes. Using human datasets extracted from the Antimicrobial Testing Leadership and Surveillance (ATLAS) program conducted by Pfizer and retail meat datasets from the National Antimicrobial Resistance Monitoring System for Enteric Bacteria (NARMS), we used a robust or weighted least square multivariable linear regression modeling framework to explore the relationship between antimicrobial susceptibility data of beta-lactam antimicrobials and different types of beta-lactamase resistance genes. In humans, in the presence of the blaCTX-M-1, blaCTX-M-2, blaCTX-M-8/25, and blaCTX-M-9 groups, MICs of cephalosporins significantly increased by values between 0.34-3.07 μg/mL, however, the MICs of carbapenem significantly decreased by values between 0.81-0.87 μg/mL. In the presence of carbapenemase genes (blaKPC, blaNDM, blaIMP, and blaVIM), the MICs of cephalosporin antimicrobials significantly increased by values between 1.06-5.77 μg/mL, while the MICs of carbapenem antimicrobials significantly increased by values between 5.39-67.38 μg/mL. In retail meat, MIC of ceftriaxone increased significantly in the presence of blaCMY-2, blaCTX-M-1, blaCTX-M-55, blaCTX-M-65, and blaSHV-2 by 55.16 μg/mL, 222.70 μg/mL, 250.81 μg/mL, 204.89 μg/mL, and 31.51 μg/mL respectively. MIC of cefoxitin increased significantly in the presence of blaCTX-M-65 and blaTEM-1 by 1.57 μg/mL and 1.04 μg/mL respectively. In the presence of blaCMY-2, MIC of cefoxitin increased by an average of 8.66 μg/mL over 17 years. Compared to E. coli isolates, MIC of cefoxitin in Salmonella enterica isolates decreased significantly by 0.67 μg/mL. On the other hand, MIC of ceftiofur increased in the presence of blaCTX-M-1, blaCTX-M-65, blaSHV-2, and blaTEM-1 by 8.82 μg/mL, 9.11 μg/mL, 8.18 μg/mL, and 1.04 μg/mL respectively. In the presence of blaCMY-2, MIC of ceftiofur increased by an average of 10.20 μg/mL over 14 years. The ability to predict antimicrobial susceptibility of beta-lactam antimicrobials directly from beta-lactamase resistance genes may help reduce the reliance on routine phenotypic testing with higher turnaround times in diagnostic, therapeutic, and surveillance of antimicrobial-resistant bacteria of the family Enterobacteriaceae.

Microbiological Survey and Evaluation of Antimicrobial Susceptibility Patterns of Microorganisms Obtained from Suspect Cases of Canine Otitis Externa in Gran Canaria, Spain.

A retrospective study of microbiological laboratory results from 2020 to 2022, obtained from a veterinary diagnostic laboratory of the island of Gran Canaria, Spain, focused on canine otitis cases, was performed. The objective of this study was to analyze the pathogen distribution, antimicrobial susceptibility, prevalence of multidrug resistant phenotypes and the role of coinfections in otitis cases in order to provide up-to-date evidence that could support effective control strategies for this prevalent pathology. A total of 604 submissions were processed for the diagnosis of canine external otitis. Of the samples analyzed, 472 were positive for bacterial or fungal growth (78.1%; 95% CI: 74.8-81.4%). A total of 558 microbiological diagnoses were obtained, divided in 421 bacterial (75.4%; 95% CI: 71.8-79.0%) and 137 fungal (24.6%; 95% CI: 20.9-28.1%) identifications. Staphylococcus pseudintermedius, Malassezia pachydermatis and Pseudomonas aeruginosa were the most prevalent microorganisms detected in clinical cases of otitis. High level antimicrobial resistance was found for Pseudomonas aeruginosa (30.7%), Proteus mirabilis (29.4%), Staphylococcus pseudintermedius (25.1%) and Escherichia coli (19%). Multidrug-resistant phenotypes were observed in 47% of the bacteria isolated. In addition, a 26.4% prevalence of methicillin-resistant Staphylococcus pseudintermedius was detected. The high prevalence of antimicrobial resistant phenotypes in these bacteria highlights the current necessity for constant up-to-date prevalence and antimicrobial susceptibility data that can support evidence-based strategies to effectively tackle this animal and public health concern.

In vitro antimicrobial susceptibility data of global meropenem-resistant Acinetobacter baumannii isolates causing pneumonia: Data from the Antimicrobial Testing Leadership and Surveillance Program, 2014–2021, and re-estimations of susceptibility breakpoints and appropriate dosages of important antibiotics for pneumonia treatment

To evaluate the susceptibility of globally pneumonia-causing meropenem-resistant (MEM-R) Acinetobacter baumannii isolates against important antibiotics and estimate appropriate dosages of indicated antibiotics. We extracted the 2014-2021 Antimicrobial Testing of Leadership Surveillance database regarding the susceptibility of MEM-R A. baumannii isolates causing pneumonia against important antibiotics. The susceptibility and carbapenemase-encoding gene (CPEG) data of pneumonia-causing MEM-R A. baumannii isolates from patients hospitalized in intensive care units of five major regions were analyzed. The susceptibility breakpoints (SBP) recommended by the Clinical and Laboratory Standards Institute (CLSI) in 2022, other necessary criteria [SBP of MIC for colistin, 2 mg/L, in the CLSI 2018; and cefoperazone-sulbactam (CFP-SUL), 16 mg/L], and the pharmacokinetic and pharmacodynamic data of indicated antibiotics were employed. Applying the aforementioned criteria, we observed the susceptible rates of colistin, minocycline, and CFP-SUL against the pneumonia-causing MEM-R A. baumannii isolates globally (n = 2905) were 93.2%, 69.1%, and 26.3%, respectively. Minocycline was significantly more active in vitro (MIC ≤4 mg/L) against the pneumonia-causing MEM-R A. baumannii isolates collected from North and South America compared to those from other regions (>90% vs. 58-72%). Additionally, blaOXA-23 and blaOXA-72 were the predominant CPEG in pneumonia-causing MEM-R A. baumannii isolates. After deliberative estimations, dosages of 200 mg minocycline intravenously every 12 h (SBP, 8 mg/L), 100 mg tigecycline intravenously every 12 h (SBP, 1 mg/L), and 160 mg nebulized colistin methanesulphonate every 8 h (SBP, 2 mg/L) are needed for the effective treatment of pneumonia-causing MEM-R A. baumannii isolates.

Clinical and microbiological characteristics of Ruminococcus gnavus bacteremia and intra-abdominal infection

ObjectivesRuminococcus gnavus is a rare human pathogen, and clinical data on R. gnavus infection are insufficient. This retrospective study aimed to investigate the clinical characteristics of R. gnavus infections. MethodsThis study included 13 cases of bacteremia and three cases of non-bacteremia infections caused by R. gnavus. We evaluated the patient data, infection source, clinical outcomes, and antimicrobial susceptibility of R. gnavus isolates for these cases. ResultsThe median age of patients was 75 years (range 47–95), and eight patients were female. Twelve cases were presumed to have an intra-abdominal infection source, and the remaining four cases had an unknown infection source. The most common underlying conditions were immunosuppression (seven cases), solid tumors (seven cases), and history of gastrointestinal surgery (five cases). Thirteen patients exhibited gastrointestinal problems (dysfunction, bleeding, intra-abdominal infection, or inflammation). Multiple pathogens were observed in six cases, and fatal outcomes were recorded in three cases. Antimicrobial susceptibility data were available for eight isolates, all of which exhibited low minimum inhibitory concentrations to penicillin (≤0.03 μg/mL), ampicillin–sulbactam (≤0.5 μg/mL), piperacillin–tazobactam (≤4 μg/mL), and metronidazole (≤0.5–1 μg/mL). ConclusionRuminococcus gnavus is frequently associated with an intra-abdominal infection source, and treatment strategies should consider the possibility of multiple pathogens.

Salmonella enterica Serovar Dublin from Cattle in California from 1993 to 2019: Characterization and Analysis of Antimicrobial Resistance Diversity.

For this study, antimicrobial susceptibility data for Salmonella enterica subsp. enterica serovar Dublin (S. Dublin)-a well-known cattle-adapted pathogen with current concerns for multidrug resistance-were recovered from cattle at the California Animal Health and Food Safety Laboratory System (CAHFS) over the last three decades (1993-2019) and were evaluated using tools to capture diversity in antimicrobial resistance. For this purpose, minimum inhibitory concentration (MIC) testing was conducted for 247 clinical S. Dublin isolates. Antimicrobial resistance (AMR) profiles revealed a predominant core multidrug-resistant pattern in the three most common AMR profiles observed. Antimicrobial resistance richness, diversity, and similarity analysis revealed patterns for changes in AMR profiles for different age groups. Discriminant analysis using MIC log2-transformed data revealed changes in MIC for year groups, with a time-sequence pattern observed. Drivers for reduced susceptibility were observed for 3rd generation cephalosporins and quinolones observed for more recent year groups (2011-2015 and 2016-2019) when compared to older year groups (1993-1999 and 2000-2005). Together, these results highlight the changes in the diversity of AMR profiles, as well as changes in susceptibility of S. Dublin over time for critical antimicrobials of importance to both animals and humans, and support the need for continued monitoring and efforts that will support judicious use of antimicrobials, especially for these two drug classes.

Analysis of blood culture data at a university hospital: bacterial distribution and cumulative antimicrobial resistance (2016–2020)

Background: The distribution of bacteria isolated from bloodstream infections and cumulative antimicrobial susceptibility data are the basis for empirical decisions regarding antibiotics as an initial treatment. Therefore, it is important to consistently collect blood culture results of individual patients and analyze them correctly. Methods: The blood culture results of patients at a university hospital from 2016 to 2020 were analyzed retrospectively to determine the bacterial distributions and antibiotic resistance patterns. Duplicates were eliminated by including only the first isolate of each species per patient. Results: Escherichia coli (27.1%) was the most commonly isolated bacterium from blood cultures, followed by Klebsiella pneumoniae (10.1%) and Staphylococcus aureus (8.6%). The methicillin resistance rate of S. aureus was 49.2%, and the vancomycin resistance rate of Enterococcus faecium was 39.5%; with no significant changes over the study period. The cefotaxime, ciprofloxacin, and ertapenem resistance rates of E. coli were 35.0%, 46.8%, and 0.7%, respectively. Seventeen carbapenem-resistant E. coli strains were isolated, of which 11 produced carbapenemase. The cefotaxime, ciprofloxacin, and ertapenem resistance rates of K. pneumoniae were 29.5%, 31.7%, and 5.4%, respectively. Forty-eight carbapenem-resistant K. pneumoniae strains were isolated, of which 37 produced carbapenemase. The imipenem resistance rates of Acinetobacter baumannii and Pseudomonas aeruginosa were 72.3% and 23.4%, respectively. Conclusion: In the blood culture results from 2016 to 2020, the isolation frequency of E. coli, K. pneumoniae, and E. faecium showed an increasing trend, whereas that of S. aureus was stable. Over the 5 year study period, the ciprofloxacin resistance rate of E. coli and P. aeruginosa and ampicillin/sulbactam resistance rate of A. baumannii significantly increased.

1253. Optimization of empiric gram-negative infections with the combination antibiogram

Abstract Background Anti-pseudomonal beta-lactam drugs such as aztreonam (AZR), cefepime (CEF), piperacillin-tazobactam (P/T), meropenem (MER) are drugs used for empiric gram-negative (GN) infections. They are used with other drugs as empiric combination therapy (CT) for patients with sepsis. The antibiogram is used to provide data for empiric therapy and gauge susceptibility pattern shifts over time. Combining different classes of drugs might enhance the susceptibility to various pathogens. This project assessed which empiric combination of drugs will yield optimal coverage for various GN pathogens from different sources. Methods In 2022 antimicrobial susceptibility data from 8288 isolates from blood, respiratory, wound and urine sources were collected and analyzed. Percent susceptibility was calculated for 11 gram-negative species with >30 isolates. Susceptibility testing was done by BD Phoenix™ automated identification and susceptibility testing system. A threshold of >90% susceptibility was used to indicate optimal coverage for the antimicrobial agents. CT is calculated as the % susceptible to either of two antibiotics. Results In respiratory sources AZR, CEF and P/T were the lowest at 73%, 83% and 77% susceptible. MER had the best overall coverage for all specimen types. Adding either an aminoglycoside (AG) or fluoroquinolone (FQ) increased susceptibility in all sources. AGs had a slightly better coverage than FQs. For blood isolates > 90% susceptibility was attained for single antibiotics without combination. CT was often required to achieve optimal coverage for respiratory sources, specifically for Pseudomonas, Enterobacter, E coli, Klebsiella and Proteus species.Figure 1.Combination antibiogram for beta-lactam agents for gram-negative respiratory isolates as monotherapy or in combination with ciprofloxacin, gentamicin, or tobramycin.*All gram-negative isolates included Serratia and Providencia species that were not included in the subgroups. Conclusion Using > 90% susceptibility as cut-off, monotherapy AZR and P/T are suboptimal for empiric coverage for certain GN respiratory infections. Blood specimens may not require CT. Adding either AGs or FQs enhanced susceptibility coverage to all tested pathogens but not uniformly. AGs enhancement was slightly better than FQs. Respiratory infections with Pseudomonas, Enterobacter cloacae, E coli, Proteus and Klebsiella species all showed enhanced coverage with CT especially for P/T and AZR. Every hospital should create a combination antibiogram to gain insight into whether empiric coverage with CT is needed. Disclosures All Authors: No reported disclosures

61 Antibiotic Resistant Patterns of Bacterial Pathogens Causing Invasive Neonatal Infections in Northern Alberta

Abstract Background Antimicrobial resistance is one of the most serious global health threats facing the world today. The neonatal intensive care unit (NICU) is a clinical environment that houses newborn infants who are highly susceptible to overwhelming infection. Early and decisive treatment with powerful anti-microbials tends to be the preferred clinical choice for treating sick infants empirically. Prolonged exposure to antimicrobials can result in multi-drug resistant organisms (MDROs), which can be associated with mortality due to an increase in virulence, delay in appropriate treatment, and a lack of treatment options. An updated antibiogram is important for determining the optimal empirical antimicrobial choice for sepsis evaluations. There is currently a lack of antimicrobial susceptibility data for bacterial pathogens in the Northern Alberta region. Objectives The objective of this study is to understand the antibiotic resistance patterns among isolates responsible for bacteremia and meningitis in the NICUs in Northern Alberta through the standard antibiograms produced by microbiology laboratories. Design/Methods We conducted a retrospective study to analyze antimicrobial resistance patterns found in NICUs during 2013-2021 in Northern Alberta. Bacteria isolated from blood and cerebrospinal fluid according to commonly used antibiotics in NICUs were collated to create a provincial antibiogram. Results A total of 5562 isolates were included in this antibiogram. The most frequently isolated organisms were Escherichia coli (1521), Staphylococcus aureus (1157), members of coagulase-negative staphylococcus (534), Enterococcus faecalis (326), and Klebsiella pneumoniae (357) in neonatal populations. Among the 1157 S. aureus isolates, 24% were resistant to oxacillin (i.e., “methicillin-resistant S. aureus” or MRSA) and 1% were resistant to vancomycin (i.e., “vancomycin-resistant S. aureus” or VRSA). Of the 326 strains of Enterococcus spp., there were no vancomycin-resistant enterococci (VRE) identified. Among gram-negative isolates, 251 out of the 2690 (9.6%) were producing extended-spectrum beta-lactamase (ESBL), in which 52% and 94% were susceptible to gentamicin and amikacin respectively. Among the non-ESBL-producing isolates, E. coli (1521) and K. pneumoniae (357), 7% of the E. coli strains and 1% of the K. pneumoniae strains were resistant to gentamicin. Conclusion The provincial antibiogram is a useful clinical tool that can best inform clinicians on the appropriate choice of empirical antimicrobial agent based on commonly identified invasive pathogens in neonatal infections within Northern Alberta. Our findings on these resistant patterns can aid next steps for developing an antimicrobial stewardship program.

Resistome-based surveillance identifies ESKAPE pathogens as the predominant gram-negative organisms circulating in veterinary hospitals.

Healthcare-associated infections (HCAIs) associated with extended-spectrum cephalosporin-resistant gram-negative (ESC-R GN) bacteria are an emerging concern in veterinary hospitals, especially in companion animal intensive care units (ICUs). To understand the molecular epidemiology of ESC-R GN isolates in two veterinary hospitals (equine and small animal), a 6-month pilot study was performed during which fecal and environmental samples were obtained twice from selected patients, upon ICU admission and after 48 h of hospitalization. In total, 295 ESC-R GNs were analyzed using the Acuitas Resistome® Test (OpGen, Maryland, US), a PCR-based assay screening for 50 antimicrobial resistance gene families encoding for production of extended-spectrum beta-lactamase (ESBLs), TEM/SHV/OXA or AmpC beta-lactamases and carbapenemases. Combining organism identification and antimicrobial susceptibility data to genotyping results, unique "Acuitas profiles" were generated that can be used for fast typing the isolates and tracking transmission events. ESKAPE GN pathogens were the most prevalent ESC-R GN isolates circulating in both the small animal and equine hospitals, consisting of Enterobacter cloacae complex (21.7%), Pseudomonas aeruginosa (20%), Klebsiella pneumoniae (15.9%), and Acinetobacter baumannii complex (13.6%) followed by Escherichia coli (12.2%), most harboring a combination of genes encoding for beta-lactamases and ESBLs. Some ESKAPE genotypes showed likely intra-hospital transmission, including E. cloacae (two genotypes, one carrying SHV4, SHV5, and TEM7 and the other TEM1, TEM3, and TEM7 enzymes) in the equine and K. pneumoniae (SHV1, SHV5, and DHA1-positive) in the small animal ICUs, respectively. Furthermore, P. aeruginosa (carrying OXA-50), A. baumannii complex (OXA-51), and E. coli (CTX-M-1) genotypes were isolated across both hospitals, suggesting possible transfer mediated via movement of staff and students. Importantly, isolates carrying transmissible resistance to last-resort antimicrobials (i.e. carbapenems) were identified within the hospital environments, consisting of three environmental Acinetobacter spp. harboring blaOXA - 23 and one clinical E. coli with blaOXA - 48. We describe the widespread occurrence of ESKAPE gram-negative organisms in veterinary ICU patients and hospital environments. Findings from this project provide baseline data on the epidemiology of ESKAPE pathogens in veterinary settings, which can inform infection control policies to aid in patient management and prevent transmission of nosocomial infections associated with these pathogens.

Serotype distribution and antibiogram of Streptococcus parauberis isolated from fish in South Korea.

Streptococcus parauberis is the dominant etiological agent of streptococcosis, the most devastating bacterial disease in the olive flounder farming industry in South Korea. In this study, the distribution of serotypes, antimicrobial susceptibility, and presence of antimicrobial resistance genes (ARGs) in S. parauberis isolates obtained between 1999 and 2021 was thoroughly investigated to gain insight into the dynamics of their presence and the relationship between serotypes and antimicrobial resistance. Disk diffusion testing of 103 isolates against 10 antimicrobial agents was performed, and epidemiological cut-off values generated through normalized resistance interpretation analysis were used to classify wild-type (WT) and non-wild-type (NWT) populations. Principal component analysis and hierarchical clustering were implemented to achieve an understanding on the relationship between serotypes and antimicrobial resistance patterns. PCR-based serotyping showed that serotype Ia (67.1%) was the most prevalent in South Korea, followed by serotypes Ib/Ic (25.2%) and II (7.7%). The highest proportion of isolates was assigned to NWT against amoxicillin (80.6%), followed by oxytetracycline (77.7%) and erythromycin (48.5%). The time-scale data showed that recently obtained serotypes Ib/Ic and II isolates tended to be categorized as NWT populations resistant to more antibiotics, possibly due to microbial adaptation to antibiotic pressure. ARGs responsible for resistance to oxytetracycline and erythromycin were found only in NWT populations in serotype Ia [tet(S) and erm(B), respectively], and serotype II [tet(M) and mef(J)-msr(I), respectively]. We also found that the mef-msr gene pair in S. parauberis serotype II might be involved in low-level resistance to erythromycin. IMPORTANCE This study presents serotype distribution and antimicrobial susceptibility data along with the antimicrobial resistance genes (ARGs) of Streptococcus parauberis, which is an important bacterial fish pathogen worldwide. In particular, almost all oxytetracycline and erythromycin non-wild-type (NWT) populations harbored tet(S) or tet(M), and erm(B) or mef(J)-msr(I), respectively. Interestingly, these ARGs were distributed in a highly serotype-dependent manner, resulting in a clear correlation between the antibiogram and serotype distribution. Moreover, recent isolates belonging to serotypes Ib/Ic and II tended to be more frequently categorized as NWT against antimicrobials, including amoxicillin and cefalexin compared to old isolates, while a dramatic decrease in erythromycin and clindamycin NWT frequencies was observed in recent serotype Ia isolates, which lacked erm(B). These variations might be attributed to shifts in the antibiotics employed in South Korean aquaculture over time. The overall findings would provide important background knowledge for understanding the epidemiology of S. parauberis infection in aquaculture.

Antimicrobial susceptibility patterns of community-acquired uropathogenic Escherichia coli, Dublin 2010-2022.

Escherichia coli is a common cause of urinary tract infections. Due to the increase in antimicrobial resistance (AMR) and global differences in antimicrobial susceptibility data, routine assessment of local antimicrobial susceptibility patterns is necessary to guide the selection of appropriate empirical therapy. The aim of this study was to evaluate the antimicrobial susceptibility patterns of community-acquired uropathogenic Escherichia coli within a catchment area in Dublin over a 13 year period, 2010-2022. All mid-stream urine samples received from local general practitioners in which there was significant E. coli bacteriuria during the study period, 2010-2022, were included in the analysis. Antimicrobial susceptibility testing was performed by disc diffusion as per the European Committee on Antimicrobial Susceptibility Testing recommendations. An average of 11 407 urine samples per month had significant bacteriuria, with E. coli accounting for an average of 67 % of those. Overall AMR rates were highest for ampicillin (53.9 %), followed by trimethoprim (32.4 %), gentamicin (18.6 %), co-amoxiclav (16.5 %), ciprofloxacin (12.3 %), cephalexin (8.3 %), cefpodoxime (6.8 %) and nitrofurantoin (2 %). While rates appeared grossly static, statistically significant reduced resistance rates were noted for co-amoxiclav (rs=-0.95; P=<0.001), cephalexin prior to 2019 (rs=-0.783; P=0.013) and trimethoprim (rs=-0.639; P=0.019), with a statistically significant increase in non-susceptibility to cefpodoxime (rs=0.802; P=0.001). In order to generate efficient empirical antimicrobial prescribing guidelines, knowledge of region-specific contemporaneous antimicrobial susceptibility patterns is pivotal. Our findings support the use of nitrofurantoin or cephalexin as empirical antimicrobial therapy within our setting.

National action plans for antimicrobial resistance and variations in surveillance data platforms.

To assess how national antimicrobial susceptibility data used to inform national action plans vary across surveillance platforms. We identified available open-access, supranational, interactive surveillance platforms and cross-checked their data in accordance with the World Health Organization's (WHO's) Data Quality Assurance: module 1. We compared platform usability and completeness of time-matched data on the antimicrobial susceptibilities of four blood isolate species: Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus and Streptococcus pneumoniae from WHO's Global Antimicrobial Resistance and Use Surveillance System, European Centre for Disease Control's (ECDC's) network and Pfizer's Antimicrobial Testing Leadership and Surveillance database. Using Bland-Altman analysis, paired t-tests, and Wilcoxon signed-rank tests, we assessed susceptibility data and number of isolate concordances between platforms. Of 71 countries actively submitting data to WHO, 28 also submit to Pfizer's database; 19 to ECDC; and 16 to all three platforms. Limits of agreement between WHO's and Pfizer's platforms for organism-country susceptibility data ranged from -26% to 35%. While mean susceptibilities of WHO's and ECDC's platforms did not differ (bias: 0%, 95% confidence interval: -2 to 2), concordance between organism-country susceptibility was low (limits of agreement -18% to 18%). Significant differences exist in isolate numbers reported between WHO-Pfizer (mean of difference: 674, P-value: < 0.001, and WHO-ECDC (mean of difference: 192, P-value: 0.04) platforms. The considerable heterogeneity of nationally submitted data to commonly used antimicrobial resistance surveillance platforms compromises their validity, thus undermining local and global antimicrobial resistance strategies. Hence, we need to understand and address surveillance platform variability and its underlying mechanisms.

Doxycycline post exposure prophylaxis could select for cross-resistance to other antimicrobials in various pathogens: An in silico analysis.

A number of randomized controlled trials have found that doxycycline post exposure prophylaxis (PEP) can reduce the incidence of gonorrhoea, chlamydia and syphilis in men who have sex with men (MSM). If tetracycline resistance is associated with resistance to other antimicrobials in a range of bacterial species, then doxycycline PEP could have the unintended effect of selecting for resistance to other antimicrobials in these bacterial species. Antimicrobial susceptibility data were retrieved from two sources: pubMLST (https://pubmlst.org/) and Pathogenwatch (https://pathogen.watch/) for the following bacterial pathogens: Klebsiella pneumoniae, Salmonella enterica subsp. Enterica serovar Typhi, Campylobacter jejuni, Staphylococcus aureus, Streptococcus pneumoniae and Streptococcus pyogenes. We assessed if tetracycline resistance was associated with resistance to six relevant antimicrobials. We found evidence of cross resistance to various antimicrobials in all six bacterial species assessed. Cross resistance was found in 4 of 5 antimicrobials for K. pneumoniae, 1 of 2 for C. jejuni, 3 of 5 for S. enterica subsp. Enterica serovar Typhi, 5 of 5 for S. aureus, 5 of 6 for S. pneumoniae and 2 of 3 for S. pyogenes. These associations include a higher prevalence of methicillin resistance in tetracycline resistant S. aureus, penicillin resistance in S. pneumoniae, macrolide and clindamycin resistance in S. pyogenes, fluoroquinolone resistance in S. enterica subsp. Enterica serovar Typhi and third-generation cephalosporin resistance in K. pneumoniae. These results suggest that studies evaluating the effects of doxycycline PEP should include the effects of doxycycline on resistance not only to doxycycline but also to other antimicrobials and in a broader array of bacterial species than has been included in doxycycline PEP studies thus far.

Occurrence of Antimicrobial Resistance in Canine and Feline Bacterial Pathogens in Germany under the Impact of the TÄHAV Amendment in 2018.

The occurrence of antimicrobial resistance due to the use of antimicrobials is considered to be a main cause for treatment failure of bacterial infections in humans and animals. The right of German veterinarians to use and prescribe medications such as antimicrobials is regulated by the Regulation of Veterinary Pharmacies (TÄHAV). The aim of this study was to investigate the impact of the second amendment to the TÄHAV in 2018 on the occurrence of antimicrobial resistance in selected bacterial pathogens isolated from dogs and cats in Germany. For this purpose, we analyzed antimicrobial susceptibility data from 38 German small animal practices gathered between 2015 and 2021 in cooperation with Laboklin (Labor für klinische Diagnostik GmbH & Co.KG, Bad Kissingen, Germany). Annual cumulative susceptibility data of eight bacterial species were analyzed and compared. The mean value of resistant isolates was determined for each year and supplemented by 95% confidence intervals. Encouraged by the amendment, an increase in sample submissions was observed in Germany. The highest resistance rates to the analyzed substances penicillin G, ampicillin, amoxicillin-clavulanic acid, cefovecin, and enrofloxacin were found for Staphylococcus pseudintermedius (S. pseudintermedius), S. aureus, and Escherichia coli (E. coli). In contrast, resistance rates were low for Pasteurella multocida (P. multocida) and β-hemolytic streptococci. Significant resistance trends (p < 0.05) assumed as influenced by the TÄHAV amendment could be the significant decreases in resistance rates of S. pseudintermedius against penicillin G to 67% (n = 322/479), and ampicillin to 63% (n = 286/453), as well as S. felis against amoxicillin-clavulanic acid and cefovecin to 2% (n = 2/109), furthermore, the reduction in the occurrence of resistance of S. aureus against enrofloxacin to 4% (n = 3/76) in 2021. Moreover, for all species, the efficacy against the analyzed substances was maintained over the study period.

Antibiograms as one-health tools for antimicrobial stewardship: California's experience with livestock antibiogram development.

Antibiograms are collections of antimicrobial susceptibility data for a particular bacterial organism and host species. Antibiograms are important tools for antimicrobial stewardship, as they may be used to guide empiric antimicrobial therapy and assess trends in antimicrobial resistance, maximizing treatment success and preserving the efficacy of currently available pharmaceuticals. Targeted use of antimicrobials is critically important to minimize the spread of antimicrobial resistance, which may be conveyed between animals and humans directly but may also be spread through the environment and ecological niches, such as soil, water, and wildlife reservoirs. To effectively utilize antibiograms as part of a comprehensive antimicrobial stewardship plan, veterinarians need to know data characteristics, including the source population, body site (when possible), and number of isolates included, in addition to the animal species and bacterial organisms for which each breakpoint was developed. Although widely used in human health systems, antibiograms are not often available in veterinary medicine. This paper describes antibiogram creation and use, discusses antibiogram development by US veterinary diagnostic laboratories, and shares California's process to create and promote livestock antibiograms. The companion Currents in One Health article by Burbick et al, AJVR, September 2023, addresses the benefits and challenges associated with developing veterinary antibiograms.

Monitoring trends in antimicrobial susceptibility patterns of bacterial isolates from horses with ulcerative keratitis

SummaryBackgroundUlcerative bacterial keratitis can result in loss of vision or the eye. Antimicrobial susceptibility data are essential in selecting optimal therapy while pending culture results.ObjectivesTo document aerobic bacterial isolates and antimicrobial susceptibilities from horses with ulcerative keratitis and report susceptibility patterns compared to previously described data from the same hospital.Study designRetrospective clinical case series.MethodsMedical records from horses with positive bacterial cultures and a clinical diagnosis of infectious ulcerative keratitis at the University of Tennessee Veterinary Medical Center between March 2011 and December 2020 were reviewed and compared to previously published data from January 1993 to May 2004.ResultsThirty‐one bacterial isolates were cultured from 27 samples (26 horses). The most common bacterial genera were Streptococcus (35%), Staphylococcus (29%) and Pseudomonas (13%), with a shift towards more Staphylococcus and less Streptococcus compared to previous years. There were minimal temporal changes in susceptibilities for these three genera. Staphylococcus spp. were statistically more likely to be cultured than other bacteria after the use of topical neomycin‐polymyxinB‐dexamethasone (p = 0.008). In vitro antimicrobial susceptibility results suggest that targeted combination therapy covered a greater percentage of isolates, compared with monotherapy, but in vitro results may not mirror in vivo results.Main limitationsInconsistencies in available medical data, selection bias and a small sample size are inherent limitations in this retrospective study, along with the inability to test against all available ophthalmic medications, challenges of interpreting cultures with limited veterinary susceptibility data and no susceptibility guidelines for topical medications.ConclusionLimited changes have occurred over the past several decades in corneal bacterial isolates and susceptibilities within this equine ophthalmology referral population, with a shift in more Staphylococcus cultured over time. Monitoring temporal trends of bacterial isolates and antimicrobial susceptibility data is important in every hospital.