ABSTRACT Acinetobacter baumannii most often causes pneumonia in critically ill patients. However, A. baumannii is also an important cause of a broader range of infections, including skin/wound and urinary tract infections. This study aims to evaluate the in vitro activity of sulbactam-durlobactam and comparator antibiotics, including meropenem and cefiderocol against A. baumannii-calcoaceticus complex isolates from non-respiratory and non-bloodstream sources. Samples included 285 A. baumannii-calcoaceticus complex isolates enriched for carbapenem resistance collected across 17 states in the United States (January 2023–May 2025). Antimicrobial susceptibility tests were conducted by manual broth microdilution and interpreted according to Clinical and Laboratory Standards Institute (CLSI) and Food and Drug Administration (FDA) (cefiderocol) standards. A. baumannii complex isolates were primarily cultured from skin/wound (58.6%), urinary tract (31.6%), and other sources (9.8%), including cerebrospinal and peritoneal fluid. Carbapenem resistance was observed in approximately 70% of isolates and more common among skin/wound cultures. Sulbactam-durlobactam was observed to be highly active (96.9% susceptible [S]; MIC90 4 mg/L) and demonstrated greater activity than sulbactam (37.9% S; MIC90 32 mg/L). Sulbactam-durlobactam also displayed high susceptibility rates across isolate sources, ranging from 96.4 (skin/wound) to 97.8% (urine). Cefiderocol demonstrated similar in vitro activity across culture sources and patient location, inhibiting >90 and >80% of isolates at CLSI and FDA susceptible breakpoints, respectively. Minocycline susceptibility was 69.1%, while tigecycline and eravacycline MICs50/90 were 1/4 and 0.5/1 mg/L, respectively. The observed data are consistent with results from surveillance studies among respiratory and bloodstream isolates and show that sulbactam-durlobactam demonstrates potent in vitro activity against clinical A. baumannii complex isolates from a variety of culture sources.IMPORTANCEAcinetobacter baumannii is a difficult-to-treat pathogen that often affects hospitalized patients and is known for a high level of multi-drug resistance. While commonly associated with pneumonia, it also causes infections in wounds, the urinary tract, and other parts of the body. This study shows that sulbactam-durlobactam is highly effective against A. baumannii from various infection sites. The results are important because they can inform clinicians on the susceptibility profiles of A. baumannii from a variety of infection sources, not just lung and bloodstream. As new antibiotics come onto the market, it is important to continuously assess resistance patterns to inform patient and system-wide health decisions.

This review summarizes novel taxon designations ascribed to prokaryotes derived from human primary clinical material during calendar year 2025, as well as proposed revisions to existing taxonomy. Major activity took place in the Streptococcus genus, as more than one dozen novel species were validly and effectively published, with two of these later classified as synonyms of Streptococcus thalassemiae. Moreover, whole genome sequencing and phylogenetic investigation of Streptococcus mitis group organisms resulted in a proposal to designate five species-level Streptococcus spp. taxa as Streptococcus mitis and an additional taxon as Streptococcus oralis subsp. dentisani. More than one dozen taxa were newly included in order Enterobacterales in 2025. Select novel taxa within genera Providencia and Enterobacter commonly possessed genotypes that conferred resistance to carbapenem and/or higher-generation cephem agents. Stenotrophomonas muris sp. nov. and Terrisporobacter muris sp. nov., initially characterized in gnotobiotic murine systems within the past 4 years, had clinical significance in human infection that was demonstrated in primary literature. The vast majority of the more than 70 novel obligate anaerobic taxa were derived from microbiome studies and had little ascribed clinical significance. Four novel obligate anaerobic Gram-negative taxa were shown to be of greater abundance in persons with Parkinson's disease than in those without. Updates to taxa previously published in the Journal of Clinical Microbiology compendia reveal that several could serve as reservoirs for multiple antimicrobial resistance determinants. One example is the non-glucose fermentative Gram-negative bacillus Pseudomonas juntendi.

Recognizing and updating bacterial names is key to communication between the veterinary clinical microbiology laboratory, veterinarians, and clients. Moraxella oculi sp. nov., distinct from Moraxella bovis and Moraxella bovoculi , was isolated from a cow with infectious bovine keratoconjunctivitis. Several respiratory pathogens were recognized, including Neisseria leonii sp. nov. described from rabbits, Mannheimia indoligenes sp. nov. described from cattle in Europe, and Moraxella haemolytica sp. nov. described from a goat in China. Stenotrophomonas forensis sp. nov. is a novel designation within the Stenotrophomonas maltophilia complex associated with isolates derived from horses. New additions to the Campylobacter genus included Campylobacter californiensis sp. nov. , recovered from bovine feces during a raw milk-associated outbreak of campylobacteriosis in humans. Taxonomic revisions were most notable in Gram-positive organisms. A species within genus Jeotgalicoccus has been renamed, and the subspecies designation Kocuria rosea subsp. polaris comb. nov. has been created. Streptococcus suis was revised to Streptococcus suis subsp. suis subsp. nov. in recognition of the initial description of Streptococcus suis subsp. hashimotonensis subsp. nov., which was isolated from people in Japan with bite wounds from boars. Chlamydophila caviae , which causes respiratory disease and abortion in guinea pigs and is zoonotic, has been revised to Chlamydia caviae comb. nov.

Ceftibuten is being developed in combination with the oral prodrug of avibactam. Outpatient isolates (n = 500) from 11 US states underwent susceptibility testing with manual broth microdilution. Ceftibuten had susceptibility rates of 64% (CLSI) and 23% (EUCAST). Ceftibuten-avibactam achieved 96.4% inhibition at MIC ≤ 1 µg/mL. Susceptibility rates were as follows: cefpodoxime (2.6%), ceftriaxone (1%), ceftazidime-avibactam (99.6%), tebipenem (89%), ertapenem (94.4%), levofloxacin (26.6%), trimethoprim-sulfamethoxazole (40.2%), and fosfomycin (96.8%). Ceftibuten-avibactam demonstrates potent in vitro activity against cephalosporin non-susceptible isolates.

ABSTRACT Preliminary experimentation has suggested that a research-use-only real-time transcription-mediated amplification assay for Treponema pallidum (RUO T. pallidum TMA) yields instances of T. pallidum nucleic acid detection that coincide with non-treponemal serology in men who have sex with men (MSM) at increased risk for sexually transmitted infection. To further characterize the specificity of RUO T. pallidum TMA testing, 3,586 rectal swab specimens reported as “not detected” by the assay generated a mean endpoint FAM fluorescence of 637.5 units. Introduction of Treponema denticola , Treponema phagedenis , and Treponema refringens nucleic acid into matrices generated mean endpoint FAM fluorescence ranging from 620.7 to 633.5 units ( P ≥ 0.15 versus control). Introduction of lubricant to a pooled rectal swab matrix did not result in elevated FAM fluorescence (mean endpoint value 628.3 units [95% CI 612.0, 644.6]; P = 0.67). Introduction of talcum powder, urine, seminal fluid, and blood also failed to generate increased FAM fluorescence ( P ≥ 0.20). Analytic sensitivity assessment was measured by serial 10-fold dilution of T. pallidum whole organism or in vitro 23S rRNA transcript in specimen transport medium or pooled rectal swab matrix and interrogation by the assay. Probit analysis estimated sensitivity (95% detection) of RUO T. pallidum TMA at 421–5,707 in vitro transcript copies/mL and 9–48 T. pallidum cells/mL, depending on dilution matrix. These results support RUO T. pallidum TMA as a highly sensitive method for T. pallidum detection that is not impacted by potentially cross-reactive organisms or interfering substances and may have adjunctive diagnosis capability for syphilis in MSM. IMPORTANCE Research-use-only Treponema pallidum transcription-mediated amplification (RUO T. pallidum TMA) has the potential to improve laboratory diagnosis of syphilis, particularly in patients at increased risk for sexually transmitted infection. The high analytic sensitivity and lack of cross-reactivity of the assay can facilitate other laboratories exploring the use of the test in a research setting.

Knowledge of novel and revised bacterial taxonomy facilitates routine operations in the medical microbiology laboratory and communication with important stakeholders. Notable new gram-positive taxa accepted in 2024 include the clinically significant Staphylococcus brunensis sp. nov., as well as Streptococcus suis subsp. hashimotonensis subsp. nov., which can be delineated from other Streptococcus suis subsp. by possession of the Lancefield group A antigen. Four novel Enterobacterales species are discussed, plus a novel eighth family Gallaecimonadaceae . One of these, Providencia huashanensis sp. nov. is clinically significant and harbors multiple genetic determinants that encode antimicrobial resistance mechanisms. Stenotrophomonas forensis sp. nov., derived from specimen transport medium, was determined to be a distinct component within the Stenotrophomonas maltophilia complex. Bartonella tamiae sp. nov. has become officially recognized as the agent of the first culture-confirmed bartonelloses in Thailand. Significant taxonomic revisions include the return of Chlamydophila caviae to the Chlamydia genus, creation of the novel Metaclostridioides genus for Clostridioides mangenotii , and reclassification of two Kocuria spp. into two subspecies of Kocuria rosea . Clinical updates are provided for 13 past Journal of Clinical Microbiology taxonomic compendium entries for which extensive clinical data were not previously available. These include potential clinical significance for non- vaginalis species of the Gardnerella genus and for Pandoraea commovens in a non-cystic fibrosis setting.

Abstract Background CTB is a currently available oral third-generation cephalosporin that is being developed in combination with the oral prodrug of AVI. In this study, we evaluated the in vitro activity of CTB-AVI against clinical ESBL-like Enterobacterales that were collected from outpatient settings. Methods 156 ESBL-like Enterobacterales isolates were received from 10 US medical centers that processed cultures from affiliated outpatient centers in 2022. Susceptibility tests for CTB-AVI and standard-of-care antibiotics were performed by CLSI broth microdilution method. Isolates were designated ESBL-like based on cefpodoxime MIC ≥2 mg/L for Proteus mirabilis and ceftriaxone MIC ≥2 mg/L for all other Enterobacterales. Fosfomycin disk diffusion was performed on E. coli isolates only and interpreted according to CLSI M100Ed32 guidance. CTB-susceptible breakpoints currently published by CLSI (≤8 mg/L) and EUCAST (≤1 mg/L) were applied to CTB-AVI for comparison. Results Isolates were primarily E. coli (60%) and Klebsiella pneumoniae (16%) and were recovered from patients seen in nursing home/long-term care (38%), urology (21%), and ambulatory care (19%) clinics. Based on CLSI and EUCAST breakpoints, CTB had susceptibility rates of 66% and 32%, respectively. The addition of AVI (fixed concentration of 4 mg/L) to CTB resulted in in vitro potentiation, resulting in 99% (CLSI) and 97% (EUCAST) susceptibility. Susceptibility rates of all isolates against comparator antimicrobials were as follows: cefpodoxime (7%), ceftriaxone (2%), ceftazidime/avibactam (CAZ-AVI) (99.4%), tebipenem (86% at preliminary susceptible breakpoint ≤0.125 mg/L), ertapenem (92.3%), levofloxacin (29%), sulfamethoxazole/trimethoprim (SMX-TMP) (47.4%), and fosfomycin (96%). CTB-AVI had 4-fold lower MIC50/90 values relative to CAZ-AVI (MIC50/90; 0.031/0.25 versus 0.25/1 mg/L). Overall, 100% of levofloxacin and SMX-TMP co-resistant isolates (n=43) were inhibited at CTB-AVI MIC breakpoint concentrations of 8 and 1 mg/L. Conclusion These data demonstrate potent in vitro activity of CTB-AVI against ESBL-like Enterobacterales isolated from patients in US nursing homes and outpatient clinics warranting further studies this oral treatment option. Disclosures April M. Bobenchik, PhD, Becton Dickinson: Grant/Research Support|BioMerieux: Advisor/Consultant|BioMerieux: Grant/Research Support|BioMerieux: Honoraria|Q-Linea: Grant/Research Support|QuidelOrtho: Grant/Research Support|TechLab: Grant/Research Support Lars Westblade, PhD, Accelerate Diagnostics, Inc: Grant/Research Support|bioMerieux, Inc: Grant/Research Support|Element Materials Technology: Grant/Research Support|Hardy Diagnostics: Grant/Research Support|Roche Molecular Systems, Inc.: Advisor/Consultant|Roche Molecular Systems, Inc.: Grant/Research Support|Selux Diagnostics, Inc.: Grant/Research Support|Shionogi, Inc: Advisor/Consultant|Talis Biomedical: Advisor/Consultant Erik Munson, PhD, Hologic, Incorporated: Advisor/Consultant|Hologic, Incorporated: Honoraria David P. Nicolau, PharmD, CARB-X: Grant/Research Support|Innoviva: Grant/Research Support|Innoviva: Honoraria|Merck: Advisor/Consultant|Merck: Grant/Research Support|Merck: Honoraria|Pfizer: Advisor/Consultant|Pfizer: Grant/Research Support|Pfizer: Honoraria|Shionogi: Advisor/Consultant|Shionogi: Grant/Research Support|Shionogi: Honoraria|Venatorx: Grant/Research Support Tomefa E. Asempa, PharmD, FDA/CDER: Grant/Research Support|Paratek: Grant/Research Support|Shionogi: Grant/Research Support|Spero: Grant/Research Support|VenatoRx: Grant/Research Support

Description of new and revised taxa originating from non-domestic animal species continues to be pursued. The majority are bacteria isolated from the alimentary system of a variety of healthy wildlife, adding to our understanding of microbial flora present in the normal state. A few new and revised taxa are associated with disease, including a novel Erysipelothrix species associated with sepsis in albatross and a revised species, Allocoenonia anatina comb. nov., associated with Riemerella anatipestifera -like disease in ducks and geese. Representative bacteria from genera that are additionally under study for the remediation of pollutants and bacteria that are related to significant animal or zoonotic pathogens are additionally discussed.

Recent work has optimized parameters of a real-time reverse transcriptase PCR-based laboratory-developed test on the Panther Fusion system which detects Mycoplasma genitalium-specific macrolide resistance-associated mutations LDT (MRM-LDT) from primary swab and urine specimens. In this study, MRM-LDT was applied to a large multi-demographic study set to further characterize M. genitalium resistance in the United States. A total of 2,145 primary clinical specimens testing positive for M. genitalium 16S rRNA by transcription-mediated amplification (TMA) were initially titered by the same assay using serial 10-fold dilutions to determine relative target nucleic acid burden. Specimens were then processed for MRM-LDT. Findings were stratified by men who have sex with men (MSM; n = 3 settings), community care (n = 2), and university student (n = 3) populations. The mean log10 target nucleic acid titer of a TMA-positive specimen was 3.46 (median 3; range 0-10). A 43.2% MRM-LDT detection rate was found in specimens derived from community care settings. Analogous assessments of university student and MSM demographics revealed 60.8% and 62.0% detection, respectively (P ≤ 0.0004 versus community care). Within the university student demographic, differences existed in target nucleic acid titer for two settings (P = 0.01); similar differences were encountered between a local MSM cohort and two that were nationally based (P ≤ 0.01). Within the university cohort, MRM-LDT detection rate was increased in symptomatic patients (P = 0.005). M. genitalium macrolide resistance rates among multiple demographics, as determined by MRM-LDT, are high in the United States and are consistent with target nucleic acid burden within the primary specimen. However, caveats experienced within subgroupings of these demographics support reflex MRM-LDT on M. genitalium-positive specimens. IMPORTANCE:Data generated from a high-throughput, automated system and presented in this report expand upon knowledge of Mycoplasma genitalium-specific macrolide resistance in the United States and may further inform providers on population- or demographic-based considerations for macrolide resistance mutation determination in M. genitalium.

The description of new taxa and nomenclature updates to currently known taxa from aquatic animal species continues. After a review of the literature from 2022 and 2023, multiple lists of bacteria, including members of Phylum Planctomycetota, were compiled. As with the previous review, most bacteria are oxidase-positive Gram-negative bacilli with familiar families including new taxa in Aeromonadaceae, Flavobacteriaceae, and Vibrionaceae. A number of Gram-positive bacilli are described including new taxa in the Nocardioides, Paenibacillus, and Streptomyces genera. Two anaerobic species are listed, and one new member of Family Planctomycetaceae is noted. Revised taxa are briefly mentioned. The majority of new and revised taxa are isolated from healthy aquatic animals, and therefore, the role of these new bacteria in health and disease is unknown. Bacteria with pathogenic association and potential production of bioactive substances are highlighted.

Continued investigation into the bacteria associated with non-domestic animals provides important information for recognizing normal flora, assessing the health status of these unique species of animals, and identifying new or emerging pathogens of concern. In this summary of novel taxa and taxonomic revisions, considerable additions have been made toward understanding fecal and mucosal flora in multiple wild animal species. In addition, novel pathogenic bacteria are discussed, including multiple Chlamydia spp. causing disease in a hawk and crocodile, two Corynebacterium spp. causing oral lesions in penguins and a lesser-known genus, Mergibacter within Family Pasteurellaceae, causing disease in multiple wild bird species. Finally, a few revisions to bacteria isolated from normal non-domestic animal body sites are mentioned.

Background We estimated the predictive value of rectal (bacterial sexually transmitted infection [bSTI]) pathogen detection for future HIV seroconversion among young adult sexual and gender minorities (YSGMs) assigned male at birth (AMAB).Methods Data were collected between March 2018 and August 2022 from RADAR, a longitudinal cohort study of YSGMs AMAB living in the Chicago metropolitan area (n = 1022). Rates of rectal bSTIs and the proportion of self-reported rectal bSTI symptoms are reported. We examined whether the presence of rectal bSTIs predicted HIV seroconversion using generalized estimating equations (GEEs).Results Participants tested reactive for rectal Mycoplasma genitalium (MGen), Neisseria gonorrhoeae (NG), and Chlamydia trachomatis (CT) at a rate of 20.8 (95% CI, 18.4-23.5), 6.5 (95% CI, 5.0-8.2), and 8.4 (95% CI, 6.8-10.3) cases per 100 persons, respectively. There were no statistically significant pairwise differences in self-reported rectal bSTI symptoms between participants with self-collected swabs testing nonreactive vs reactive for rectal MGen (chi 2 = 0.04; P = .84), NG (chi 2 = 0.45; P = .37), or CT (chi 2 = 0.39; P = .46). In multivariate GEE analysis, rectal NG (adjusted odds ratio, 5.11; 95% CI, 1.20-21.77) was a statistically significant predictor of HIV seroconversion after controlling for other bSTIs, demographics, and sexual risk behavior.Conclusions Our findings provide a robust longitudinal estimation of the relationship between primarily asymptomatic rectal NG nucleic acid detection and HIV infection. These findings highlight the importance of asymptomatic screening for bSTIs and targeting biobehavioral intervention to prevent HIV infection among YSGMs with rectal bSTI agents detected.

Background: Mycoplasmoides genitalium remains a difficult sexually-transmitted infection (STI) to manage due to its potential for antimicrobial resistance and post-infection sequelae. University students are especially vulnerable, as this demographic has the highest rate of STI in the United States. As a result, investigating prevalence rates and therapeutic outcomes in this population is essential to minimize future impact of M. genitalium. The purpose of this study was to investigate a university student population for M. genitalium distribution and treatment outcome. Design: Retrospective chart-review of university health clinic attendees, augmented by laboratory detection of M. genitalium following therapeutic intervention. Methods: A total of 1617 student encounters at a midwestern United States university health clinic over a 28-month interval from November 2017 through February 2020 were analyzed for M. genitalium and Chlamydia trachomatis positivity rates and prevalence. Detection of these sexually-transmitted pathogens occurred by commercial RNA amplification testing. Chart review was focused on participant outcomes following initial M. genitalium detection and therapeutic intervention. Results: C. trachomatis positivity and prevalence rates were 7.05% and 9.00%, respectively, while analogous rates for M. genitalium were 7.05% and 6.51%, respectively. An average of 1.83 positive results was generated from participants infected with M. genitalium at any time, with an average of 1.17 positive results for C. trachomatis (P < 0.0002). For students treated with azithromycin, 30.3% generated a negative M. genitalium result upon follow-up, with 1g daily and 2-day 500mg dosing regimens demonstrating less efficacy than a 4-day 250mg regimen or moxifloxacin. Conclusion: Data indicate a need for molecular M. genitalium macrolide resistance determination from primary specimens in the university setting.