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Extended-spectrum β-lactamase (ESBL)-producing bacteria are a growing public health concern within the One Health framework. This study aimed to characterize ESBL-producing Enterobacterales in industrial and artisanal organic fertilizers marketed in southwestern Colombia. Five commercial fertilizer brands were analyzed using a selective culture on ceftriaxone supplemented media (4 µg/mL), antimicrobial susceptibility testing by broth microdilution to determine minimum inhibitory concentrations (MICs), phenotypic synergy testing for ESBL confirmation, and polymerase chain reaction (PCR) to detect bla_TEM, bla_SHV, and bla_CTX-M genes. Overall, 18.6% of the samples showed growth of ceftriaxone-resistant Enterobacterales, predominantly Escherichia coli and Klebsiella pneumoniae. ESBL producers accounted for 84% of the isolates, all of which carried at least one bla gene, predominantly bla_CTX-M. Statistically significant differences in bacterial growth frequency were observed among fertilizer types, with higher positivity rates observed in manure-based artisanal formulations (p < 0.05). Whole-genome sequencing of selected isolates identified Klebsiella pneumoniae ST37 and Escherichia coli ST224, both harboring bla_CTX-M-55 and additional resistance and virulence determinants. These findings demonstrate that organic fertilizers, particularly manure-derived products, may act as reservoirs and potential dissemination routes for clinically relevant antimicrobial-resistant bacteria. This is the first study in Colombia documenting the presence of ESBL-producing bacteria in organic fertilizers. These results underscore the need to incorporate surveillance of these products into national policies under a One Health perspective.

Ceftazidime/avibactam (CZA) is a promising treatment option for infections caused by carbapenem-resistant Enterobacterales (CRE). However, CZA resistance is increasingly reported worldwide, largely due to the emergence of KPC variants and increase of metallo-β-lactamases (MBL). This study describes the mechanisms associated with CZA resistance in circulating Enterobacterales isolates from Colombia, highlighting the challenge this represents for microbiological identification. Between 2021 and 2024, 68 CZA-resistant Enterobacterales isolates were identified by automated methods in seven Colombian cities. Resistance to CZA was subsequently confirmed by broth microdilution and E-test. Carbapenemase production was evaluated using phenotypic tests, such as the mCIM test, Carba NP, lateral flow assay, and qPCR ( bla _KPC , bla _NDM , bla _VIM , bla _IMP , and bla _OXA-48 ). Whole-genome sequencing was performed on 15 isolates that tested negative for MBL genes. Whole-genome sequencing of these 15 isolates revealed a variety of resistance determinants: six isolates harbored bla _KPC-31 , one bla _KPC-33 , one bla _KPC-8 , five harbored bla _PAC-2 , and two co-harbored bla _PAC-2 and bla _KPC-2 . Notably, bla _PAC-2 was located on an IncQ plasmid. However, some of these variants were not detected by phenotypic assays, likely due to their low or undetectable carbapenemase activity. CZA resistance in non-MBL producing Enterobacterales in Colombia is primarily mediated by the presence of bla _KPC-31 and emergence of bla _PAC-2 . These resistance mechanisms pose significant diagnostic, therapeutic, and epidemiological challenges, as they frequently go undetected by conventional microbiological methods. In this context, enhanced molecular surveillance and improved diagnostic strategies are urgently needed to enable early detection, guide antimicrobial therapy, and support infection control and stewardship efforts. IMPORTANCE: Antibiotic resistance is a serious global health threat. Ceftazidime/avibactam (CZA) is a key treatment option for multidrug-resistant (MDR) Enterobacterales often used when other antibiotics fail. However, bacteria are now developing resistance to this drug as well, making infections increasingly difficult to treat. In this study, we examined CZA-resistant bacteria from multiple cities in Colombia and found uncommon resistance genes across several bacterial species. These genes are frequently missed, as they often do not test positive due to the limitations of most routinely used laboratory tests. Importantly, some of these genes can be transferred between bacteria, increasing the likelihood of indiscriminate dissemination in the hospital setting. Therefore, our findings highlight the urgent need for improved diagnostic tools and molecular surveillance. Early detection will help physicians select effective treatments quickly and prevent the wider dissemination of these MDR-resistant bacteria.

Delay in the initial administration of antimicrobials is one of the strongest predictors for mortality for septic patients in the intensive care unit (ICU). Given the different logistics among hospitals for antibiotic administration, this delay can take hours. As antibiotic administration involves care coordination and the participation of different team members, education and the antimicrobial stewardship (AMS) program play a key role in reducing these times. This study evaluated the time between the initial prescription and the effective administration of antibiotics for ICU patients in seven Latin American hospitals, before (pre-) and after (post-I and post-II) the implementation of a tailored educational approach. After establishing a baseline measurement (pre-), we implemented a tailored educational intervention directed to the ICU team including nurses, specialists, pharmacists, and the members of the AMS team. Then, we conducted a post-intervention measurement after a 3 month period (post-I) and repeated it after a 1 year period (post-II). During the pre-interventional phase, the hang time varied between 88 and 178 min, reporting an adherence to the 1 hour bundle of 33.8%. For the post-I, it significantly reduced with time variations between 46 and 104 min, showing an increase of 54.9% in adherence. After 1 year, in post-II, a persistent effect of shorter administration time was observed, varying between 49 and 109 min, increasing the adherence to 59.6%. Our results highlight that an active and tailored multidisciplinary AMS educational process incorporating antibiotic hang time protocols and including multidisciplinary healthcare teams involved in coordinating sepsis care decreases the administration time of antibiotics in Latin American hospitals with limited resources.

Resistance to ceftazidime-avibactam (CZA) due to Klebsiella pneumoniae carbapenemase (KPC) variants is increasing worldwide. We characterized two CZA-resistant clinical Klebsiella pneumoniae strains by antimicrobial susceptibility test, conjugation assays, and WGS. Isolates belonged to ST258 and ST45, and produced a KPC-31 and a novel variant KPC-197, respectively. The novel KPC variant presents a deletion of two amino acids on the Ω-loop (del_168–169_EL) and an insertion of two amino acids in position 274 (Ins_274_DS). Continued surveillance of KPC variants conferring CZA resistance in Colombia is warranted. IMPORTANCE: Latin America and the Caribbean is an endemic region for carbapenemases. Increasingly high rates of Klebsiella pneumoniae carbapenemase (KPC) have established ceftazidime-avibactam (CZA) as an essential antimicrobial for the treatment of infections due to MDR Gram-negative pathogens. Although other countries in the region have reported the emergence of CZA-resistant KPC variants, this is the first description of such enzymes in Colombia. This finding warrants active surveillance, as dissemination of these variants could have devastating public health consequences.

Introducción. El comportamiento de la resistencia antimicrobiana es fundamental en el mejoramiento y ajuste de los programas de optimización de uso de antimicrobianos, la implementación de las guías terapéuticas y las precauciones que limitan la transmisión cruzada de bacterias resistentes entre pacientes. Desde el inicio del 2020, la pandemia del SARS-CoV-2 desafió profundamente al sistema de salud y, según algunos reportes, aumentó las tasas de resistencia antimicrobiana.Objetivo. Describir el comportamiento de la resistencia antimicrobiana en los microrganismos más frecuentes en veinte hospitales colombianos durante el periodo 2018-2021.Materiales y métodos. Se trata de un estudio descriptivo basado en la información microbiológica reportada por veinte instituciones de salud de nivel III y IV, entre enero de 2018 y diciembre de 2021, en doce ciudades de Colombia, las cuales hacen parte del “Grupo para el estudio de la resistencia nosocomial en Colombia”, liderado por la Universidad El Bosque. La identificación de género y especie de los microorganismos más frecuentes, junto con su perfil de resistencia frente a antibióticos marcadores, se determinaron mediante el análisis de los datos vía WHONET.Resultados. En general, los 10 microorganismos más frecuentes analizados a lo largo de los 4 años no presentaron cambios estadísticamente significativos en sus perfiles de resistencia durante los cuatro años del periodo evaluado, de 2018 a 2021. En contraste, Pseudomonas aeruginosa aumentó su resistencia frente a piperacilina-tazobactam y carbapenémicos, lo cual fue estadísticamente significativo.Conclusiones. Los cambios en la resistencia antimicrobiana en estos años no han sido estadísticamente significativos, excepto para P. aeruginosa, bacteria que mostró un incremento en las tasas de resistencia a piperacilina-tazobactam y carbapenémicos.

We report the presence of the mcr-1 gene among 880 Escherichia coli clinical isolates collected in 13 hospitals from 12 Colombian cities between 2016 and 2019. Seven (0.8%) isolates were colistin resistant (MIC ≥ 4 µg/mL). These colistin-resistant isolates were screened for the presence of the mcr-1 gene; five carried the gene. These five isolates were subjected to whole genome sequencing (WGS) to identify additional resistomes and their ST. In addition, antimicrobial susceptibility testing revealed that all E. coli isolates carrying mcr-1 were susceptible to third generation-cephalosporin and carbapenems, except one, which carried an extended-spectrum β-lactamase (CTX-M-55), along with the fosfomycin resistance encoding gene, fosA. WGS indicated that these isolates belonged to four distinct sequence types (ST58, ST46, ST393, and a newly described ST14315) and to phylogroups B1, A, and D. In this geographic region, the spread of mcr-1 in E. coli is low and has not been inserted into high-risk clones such as ST131, which has been present in the country longer.

Background: Ceftolozane/tazobactam (C/T) is a combination of an antipseudomonal oxyiminoaminothiazolyl cephalosporin with potent in vitro activity against Pseudomonas aeruginosa and tazobactam, a known β-lactamase inhibitor. The aim of this study was to evaluate the activity of C/T against clinical isolates of P. aeruginosa and Enterobacterales collected from five Latin American countries between 2016 and 2017, before its clinical use in Latin America, and to compare it with the activity of other available broad-spectrum antimicrobial agents. Methods: a total of 2760 clinical isolates (508 P. aeruginosa and 2252 Enterobacterales) were consecutively collected from 20 hospitals and susceptibility to C/T and comparator agents was tested and interpreted following the current guidelines. Results: according to the CLSI breakpoints, 68.1% (346/508) of P. aeruginosa and 83.9% (1889/2252) of Enterobacterales isolates were susceptible to C/T. Overall, C/T demonstrated higher in vitro activity than currently available cephalosporins, piperacillin/tazobactam and carbapenems when tested against P. aeruginosa, and its performance in vitro was comparable to fosfomycin. When tested against Enterobacterales, it showed higher activity than cephalosporins and piperacillin/tazobactam, and similar activity to ertapenem. Conclusions: these results show that C/T is an active β-lactam agent against clinical isolates of P. aeruginosa and Enterobacterales.

Polymyxin resistance in Klebsiella pneumoniae has been attributed to mutations in mgrB, phoPQ, pmrAB, and crrAB and to the presence of mcr plasmid-mediated genes. Herein, we describe the molecular characteristics of 24 polymyxin- and carbapenem-resistant K. pneumoniae isolates recovered from six Colombian cities between 2009 and 2019. Minimum inhibitory concentrations (MICs) to polymyxin were confirmed by broth microdilution, and whole-genome sequencing was performed to determine sequence type, resistome, and mutations in the genes related to polymyxin resistance, as well the presence of mcr. The results showed high-level resistance to polymyxin (MICs ≥ 4 μg/mL). bla_KPC-3 was present in the majority of isolates (17/24; 71%), followed by bla_KPC-2 (6/24; 25%) and bla_NDM-1 (1/24; 4%). Most isolates belonged to the CG258 (17/24; 71%) and presented amino acid substitutions in PmrB (22/24; 92%) and CrrB (15/24; 63%); mutations in mgrB occurred in only five isolates (21%). Additional mutations in pmrA, crrA, and phoPQ nor any of the mcr resistance genes were identified. In conclusion, we found clonal dissemination of polymyxin and carbapenem-resistant K. pneumoniae isolates in Colombia, mainly associated with CG258 and bla_KPC-3. Surveillance of this multidrug-resistant clone is warranted due to the limited therapeutic options for the treatment of carbapenem-resistant K. pneumoniae infections.

Background: The dissemination of the uropathogenic O25b-ST131 Escherichia coli clone constitutes a threat to public health. We aimed to determine the circulation of E. coli strains belonging to O25b:H4-B2-ST131 and the H30-Rx epidemic subclone causing hospital and community-acquired urinary tract infections (UTI) in Colombia. Methods: Twenty-six nonduplicate, CTX-M group-1-producing isolates causing UTI in the hospital and community were selected for this study. Results: Twenty-two E. coli isolates harboring CTX-M-15, one CTX-M-3, and three CTX-M-55 were identified. Multilocus Sequence Typing (MLST) showed a variety of sequence types (STs), among which, ST131, ST405, and ST648 were reported as epidemic clones. All the E. coli ST131 sequences carried CTX-M-15, from which 80% belonged to the O25b:H4-B2 and H30-Rx pandemic subclones and were associated with virulence factors iss, iha, and sat. E. coli isolates (23/26) were resistant to ciprofloxacin and associated with amino acid substitutions in quinolone resistance-determining regions (QRDR). We detected two carbapenem-resistant E. coli isolates, one coproducing CTX-M-15, KPC-2, and NDM-1 while the other presented mutations in ompC. Additionally, one isolate harbored the gene mcr-1. Conclusions: Our study revealed the circulation of the E. coli ST131, O25b:H4-B2-H30-Rx subclone, harboring CTX-M-15, QRDR mutations, and other resistant genes. The association of the H30-Rx subclone with sepsis and rapid dissemination warrants attention from the public health and infections control.