This single-center retrospective study analyzed de-duplicated Pseudomonas aeruginosa isolates collected at Huaian Municipal Infectious Diseases Hospital from 2023 to 2025. A total of 121 unique isolates were included, of which 83.5% were from sputum. Antimicrobial susceptibility testing (AST) was performed using an automated microbiology system, and minimum inhibitory concentration (MIC) results were interpreted according to CLSI M100, 33rd edition. In early 2024, a four-dimensional linkage-targeted antimicrobial stewardship intervention was implemented in the Respiratory and Tuberculosis Department (Resp-TB) (n = 97), comprising: (1) dynamic antimicrobial resistance surveillance with quarterly feedback; (2) risk-stratified antimicrobial prescribing based on local susceptibility data; (3) standardized specimen collection protocols; and (4) enhanced infection prevention and control measures. In the Resp-TB, the overall resistance rates were 74.19% in 2023, 81.63% in 2024, and 82.93% in 2025, with no significant reduction after the intervention (p ≈ 0.37). By 2025, resistance to tobramycin was 0/41 (0.00%), cefepime was 1/41 (2.44%), and piperacillin-tazobactam was 0/41 (0.00%); levofloxacin resistance reached 15/41 (36.59%). Trimethoprim-sulfamethoxazole resistance remained high across the study period. These findings show persistent antimicrobial resistance in the Resp-TB after implementation of the intervention, while resistance to selected agents, including tobramycin, cefepime, and piperacillin-tazobactam, remained low in 2025.

We conducted a retrospective review to characterize adverse events in patients receiving oral linezolid, trimethoprim-sulfamethoxazole, voriconazole, and itraconazole monitored under an outpatient parenteral antimicrobial therapy program. Among 118 patients, 61% incurred at least 1 adverse event during treatment, highlighting the need for evidence-based monitoring protocols for complex outpatient antimicrobial therapy.

Burkholderia pseudomallei, the causative agent of melioidosis, is a gram-negative bacterium historically endemic to Southeast Asia and Northern Australia. However, recent environmental detection along the Gulf Coast and an increasing number of reported cases in non-travelers have raised questions regarding potential endemicity and environmental establishment in the Southern United States. We report a case of putatively locally acquired pulmonary melioidosis in a Florida resident with no recent international travel history, illustrating the diagnostic and therapeutic challenges posed by this rare pathogen. The patient presented with fever, pleuritic chest pain, and hypoxia following a period of severe weather. Computed tomography (CT) of the chest revealed multiple solid pulmonary nodules with ground-glass opacities and mediastinal lymphadenopathy. Given his underlying stage 3b chronic kidney disease (CKD), the patient was treated with an intensive course of intravenous ceftazidime followed by oral doxycycline monotherapy, achieving full clinical recovery. Follow-up imaging at 3 months demonstrated complete resolution of the pulmonary nodules. This case emphasizes the importance of considering melioidosis in the differential diagnosis for non-resolving community-acquired pneumonia or significant pulmonary nodules in the Southern United States, even in the absence of international travel. Risk factors such as diabetes mellitus and severe weather events are key clinical clues. While trimethoprim-sulfamethoxazole remains the preferred eradication therapy, doxycycline may serve as a potential alternative for patients with renal impairment when first-line therapy is contraindicated.

Antimicrobial resistance (AMR) is a global human health threat and wastewater analysis of antibiotics can help inform AMR policies. Accurate quantification of antibiotic use in urban populations is needed. This requires analytical methods capable of high sample throughput to support short-term laboratory antibiotic fate investigations where large sample numbers are generated, and sub-µg L[-1] quantification limits for wastewater monitoring studies. Therefore, a direct injection ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was developed for 11 representative antibiotics and metabolites with a 13 min run time and quantitation limits in the range of 0.0012-0.69 µg L[-1]. Avoiding solid phase extraction simplified sample preparation whilst mitigating potential contamination or analyte loss, additional solvent use and single-use plastics. High throughput application of the method was demonstrated by assessing antibiotic stability in laboratory-scale gravity sewers (n = 6) with sampling intervals of 0, 0.5, 1, 2, 4, 6, 8, and 24 hours. Amoxicilloic acid, hydroxymetronidazole, trimethoprim and clarithromycin showed satisfactory short-term stability (4 h) for sampling influent wastewater at treatment plants for population use assessment. The sensitivity of the direct injection methodology was demonstrated by random influent wastewater monitoring (n = 5) at three treatment plants in North-East Scotland during August by 24 h pseudo flow-weighted composite sampling. This revealed amoxicillin, metronidazole, trimethoprim and clarithromycin use ranged from 263 to 3559 mg/1000 people per day. This was 0.5 to 1.8 times the corresponding average daily prescribed quantity (calculated from total August prescribing) within the treatment plant's catchment area, highlighting differences in prescription and consumption levels across locations. Findings demonstrated direct injection UHPLC-MS/MS to be ideal for supporting population use assessment of antibiotics through application to laboratory and monitoring wastewater studies.

Pasteurella multocida, a Gram-negative coccobacillus commonly found in the oropharyngeal flora of cats, is a rare cause of peritoneal dialysis-associated peritonitis. We report the case of a 44-year-old patient with exposure to stray cats who presented with abdominal pain and cloudy dialysis effluent. Laboratory tests showed leukocytosis and elevated C-reactive protein (CRP), and we initiated empirical intraperitoneal cefazolin therapy. Peritoneal fluid culture yielded P. multocida, which was resistant to fluoroquinolones but susceptible to penicillin, cefotaxime, trimethoprim-sulfamethoxazole, and tetracycline. The patient showed rapid clinical improvement. This case highlights the importance of assessing animal exposure in patients undergoing peritoneal dialysis and underscores the emergence of antimicrobial resistance in P. multocida within a One Health framework.

Streptococcus pneumoniae is a major bacterial pathogen, and dihydropteroate synthase (DHPS) is the primary target of sulfonamides (SAs). Environmental exposure to SAs promotes the emergence and spread of antibiotic resistance. However, the molecular basis of DHPS mutation-mediated resistance remains unclear. Derived from the folP sequences of trimethoprim-sulfamethoxazole-resistant clinical isolates, six clinically relevant DHPS mutants were constructed to investigate the molecular basis of resistance and to clarify how structure-activity relationships influence ligand recognition and binding modes. The results showed that the mutations altered the structural characteristics of the catalytic cavity and the substrate tunnel but exerted limited effects on the entry or binding of 6-hydroxymethyl-7,8-dihydropterin pyrophosphate (DHPPP). DHPPP binding induced conformational remodeling, including expansion of loop 2 or loop 5 and rotation of HIE153. Compared with the wild type, sulfamethoxazole (SMX) exhibited reduced binding affinities across all mutants, with loop 2 expansion and impaired loop closure identified as the primary structural determinants of resistance. Additionally, HIE153 indirectly contributed to SMX recognition by maintaining the local microenvironment, binding pocket conformation, and neighboring interaction networks. Structure-activity relationship analysis showed that fused-ring sulfonamides exhibited the strongest tolerance to resistance-associated mutations. These findings reveal how DHPS mutations preserve natural-substrate recognition while selectively weakening SA binding, providing molecular-level insight into SA resistance and its implications for environmental antimicrobial resistance.