Background: The use of quinolone prophylaxis in high-risk neutropenic patients is considered standard of care but the development of resistance is a concern. Previous studies have focused mainly on quinolone resistance among patients receiving prophylaxis, with very few data reporting its impact on the hospital microbial epidemiology. Methods: We analyzed a cohort of 329 episodes of chemotherapy-induced neutropenia in adults, and compared two periods: 2005 (period 1, no prophylaxis, n=110) and 2006-2008 (period 2, ciprofloxacin prophylaxis, n=219). Outcomes analyzed were the frequency of febrile neutropenia, bacteremia, duration of antibiotic therapy and hospitalization, and antimicrobial resistance to ciprofloxacin and extended-spectrum beta-lactamase [ESBL] production. We analyzed resistance rates (by patients-day) in the cohort, as well as in other patients (neutropenic and non-neutropenic, 11,975 patients-day) admitted to the hematology unit in the same period, taking into consideration the general resistance patterns in the hospital. Results: Quinolone prophylaxis (period 2) resulted in fewer episodes of febrile neutropenia (159/219 [73%] vs. 102/110 [93%], Chi-square 18.09, p = 0.00002), and bacteremia (49/219 [22] vs. 36/110 [33%], Chi-square 4.10, p = 0.04), shorter duration of antibiotic therapy (p = 0.0002) and hospitalization (p = 0.002), but more frequent use of carbapenems (79/219 [36%] vs. 15/110 [14%], Chi-square 18.06, p = 0.0002). In addition, period 2 was associated with higher rates of quinolone resistance (6.77 vs. 3.02 per 1,000 patients-day, p = 0.03). The rate of ESBL-producing enterobacteria in the two periods was slightly higher in patients receiving quinolone prophylaxis (1.27 vs. 0.38 per 1,000 patients-day, p = 0.26) as well as in the hematology unit overall (1.59 vs. 0.53 per 1,000 patients-day, p = 0.08), but remained stable in the whole hospital (0.53 vs. 0.56 per 1,000 patients-day, p = 0.74). Conclusions: Ciprofloxacin prophylaxis was beneficial in high risk neutropenic patients, but important modifications in the prescription of carbapenems and on antimicrobial resistance patterns of isolates were observed. The importance of hospital or ward ecology must be taken into account when deciding for quinolone prophylaxis in high-risk neutropenic patients.

Due to bacterial resistance to antimicrobials, antibiotic therapy for urinary tract infections (UTIs) has become a major challenge for clinicians. The present work aimed to compare the antimicrobial susceptibility profiles of 53 uropathogenic Escherichia coli (UPEC) isolates, assessed using the disk diffusion method and two automated systems (PHOENIX BD™ and VITEK2), with interpretations based on CLSI and BrCAST guidelines. Twenty-five antibiotics were tested to assess differences in susceptibility profiles. Statistical tools, including Kappa coefficient analysis and chi-square tests, were applied to assess concordance and significance between methods. Among the main discrepancies found, BrCAST has classified a greater number of UPEC isolates as resistant to more than half of the antibiotics tested by the disk diffusion method, when compared to CLSI. Although faster, the PHOENIX BD and VITEK2 automated systems exhibited significant discrepancies, with divergences observed for half of the antimicrobials tested. Both automated methods showed discrepancies compared to the disk diffusion method under CLSI and BrCAST guidelines. PHOENIX BD classified some isolates resistant by DD/CLSI as susceptible, while VITEK2 misclassified 25% to 50% of the antimicrobials tested. Conversely, VITEK2 also classified some isolates susceptible to DD/CLSI as resistant to 25% of the antimicrobials tested. Regarding DD/BrCAST, PHOENIX BD classified resistant isolates as susceptible (to 50% of the antimicrobials tested). In comparison, VITEK2 classified resistant isolates as susceptible and susceptible isolates as resistant (25% of the antimicrobials for both). These findings highlight the need for careful selection of susceptibility testing methods, as variations in interpretive criteria between CLSI and BrCAST could impact clinical decision-making. This study underscores the importance of methodological consistency in accurately informing antibiotic therapy in UTI management, especially in the face of rising resistance.

The increasing prevalence and dissemination of multidrug-resistant bacteria represent a serious concern for public health. Aeromonas caviae is a pathogenic microorganism that causes a wide spectrum of diseases in fish and humans and is often associated with aquatic environments and isolated from foods and animals. Here, we present the isolation and characterization of the V15^T strain isolated from a drinking water storage tank in Rio de Janeiro, Brazil. The V15^T strain has a genome length of 4,443,347 bp with an average G + C content of 61.78% and a total of 4028 open reading frames. Its genome harbors eight types of antibiotic resistance genes (ARGs) involving resistance to beta-lactamases, macrolides, and quinolones. The presence of bla_MOX-6, bla_OXA-427/bla_OXA-504, and mutations in parC were detected. In addition, other ARGs (macA, macB, opmH, and qnrA) and multidrug efflux pumps (such as MdtL), along with several resistance determinants and 106 genes encoding virulence factors, including adherence (polar and lateral flagella), secretion (T2SS, T6SS), toxin (hlyA), and stress adaptation (katG) systems, were observed. The genome sequence reported here provides insights into antibiotic resistance, biofilm formation, evolution, and virulence in Aeromonas strains, highlighting the need for more public health attention and the further monitoring of drinking water systems. Also, the results of physiological and phylogenetic data, average nucleotide identity (ANI) calculation, and digital DNA–DNA hybridization (dDDH) analysis support the inclusion of the strain V15^T in the genus Aeromonas as a new subspecies with the proposed name Aeromonas caviae subsp. aquatica subsp. nov. (V15^T = P53320^T). This study highlights the genomic plasticity and pathogenic potential of Aeromonas within household drinking water systems, calling for the revision of water treatment protocols to address biofilm-mediated resistance and the implementation of routine genomic surveillance to mitigate public health risks.

Background/Objectives: Uropathogenic Escherichia coli (UPEC) is the leading cause of urinary tract infections in both community and hospital settings worldwide. Antimicrobial-resistant UPEC strains pose a significant challenge for effective antibiotic therapy. In this study, 50 bacterial isolates recovered from urine samples of patients attended in different sectors of a public hospital in Rio de Janeiro over five months were analyzed to assess antimicrobial resistance and virulence profiles through broad gene screening. Methods: Biofilm production was assessed using a semi-quantitative adherence assay. PCR was employed to investigate 27 resistance genes, 6 virulence genes, sequence types (STs), and phylogroups. Susceptibility to 25 antimicrobial agents was determined by disk diffusion testing. Furthermore, the pathogenic potential was evaluated in vivo using the Tenebrio molitor larvae infection model. Results: Most UPEC isolates were moderate or strong biofilm producers (41/50; 82%). The sul1 and sul2 resistance genes were the most frequently detected (58%). Two virulence gene patterns were identified: fyuA, iutA, fimH, cnf1 and fyuA, iutA, fimH (13 isolates; 26%). ST131 and ST73 were the most common sequence types (16% each), and phylogroup B2 was the most prevalent (50%). Thirty isolates (60%) were multidrug-resistant, most of which belonged to phylogroup B2. UPEC exhibited dose-dependent lethality, causing 100% mortality at 2.6 × 10⁸ CFU/mL within 24 h. Conclusions: These findings reinforce the urgent need for surveillance strategies and effective antimicrobial stewardship in clinical practice.

Antimicrobial resistance (AMR), once a natural evolutionary phenomenon, has become a critical global public health threat due to the excessive and indiscriminate use of antibiotics. Over recent decades, widespread antibiotic use in clinical, agricultural, and environmental settings has exerted substantial selective pressure on microbial populations, accelerating the emergence and horizontal transfer of resistance genes. These resistant organisms, and their genetic elements, now circulate not only in healthcare systems but also in natural ecosystems, highlighting the scale and complexity of the problem. This study adopts a qualitative, applied research design grounded in a multiple case study methodology with cross-case synthesis, complemented by bibliometric network analysis using VOSviewer software. A literature review spanning the years 2014 to 2024 was conducted using a curated set of interdisciplinary keywords to capture the convergence of environmental science, microbiology, and public health. The findings revealed thematic clusters and knowledge structures associated with AMR, particularly its links to environmental contaminants such as heavy metals. By situating AMR within the One Health framework, this manuscript emphasizes the interconnectedness of human, animal, and environmental health. It calls for integrative and transdisciplinary strategies capable of responding to the biological, social, economic, and policy-related dimensions of AMR, underscoring the urgent need for systemic and coordinated global action.

The present study aims to investigate two of the Uropathogenic Escherichia coli (UPEC) pathogenesis mechanisms, as adherence and invasion in primate kidney epithelial (Vero) cells. Methods: 20 E. coli isolates from outpatients with UTI in one public clinic were evaluated for adherence and invasive abilities in Vero cells. Results: All 18 positive isolates for fimH gene adhered to the Vero cells (100%). The two UPEC isolates that did not carry the fimH gene did not adhere. Two different UPEC adherence patterns were observed: aggregative adherence pattern (AA) and a pattern called “no typical adherence pattern” (NTA). Among 18 adherent UPEC isolates, 11 presented AA adherence pattern (61%) and 7 showed NTA pattern (39%). The high rate of adherence of the UPEC fimH positive isolates (≅90%) to Vero cells suggests the expression and participation of the FimH adhesin in UPEC adherence behavior. Invasive capacity of UPEC isolates ranged of about 6.5% to 15.33%. Results corroborate the fact that UPEC can persist in the urinary tract through its adhesion, as well as invade cells establishing the bacterial UTI process.