Polymyxins are last-resort antimicrobial agents used to treat infections caused by carbapenem-resistant Enterobacteriaceae . Due to the worldwide dissemination of polymyxin resistance in animal and human isolates, we aimed to characterize polymyxin resistance associated with the presence of mcr-1 in Enterobacteriaceae and nonfermenter Gram-negative bacilli, using isolates collected retrospectively in Colombia from 2002 to 2016. A total of 5,887 Gram-negative clinical isolates were studied, and 513 were found to be resistant to the polymyxins. Susceptibility to colistin was confirmed by broth microdilution for all mcr-1 -positive isolates, and these were further subjected to whole-genome sequencing (WGS). The localization of mcr-1 was confirmed by S1 pulsed-field gel electrophoresis (S1-PFGE) and CeuI-PFGE hybridization. Transferability was evaluated by mating assays. A total of 12 colistin-resistant isolates recovered after 2013 harbored mcr-1 , including 8 Escherichia coli , 3 Salmonella enterica serovar Typhimurium, and 1 Klebsiella pneumoniae isolate . E. coli isolates were unrelated by PFGE and belonged to 7 different sequence types (STs) and phylogroups. S . Typhimurium and K. pneumoniae isolates belonged to ST34 and ST307, respectively. The mcr-1 gene was plasmid borne in all isolates but two E. coli isolates which harbored it on the chromosome. Conjugation of mcr-1 was successful in 8 of 10 isolates (8.2 × 10 ⁻⁵ to 2.07 × 10 ⁻¹ cell per recipient). Plasmid sequences showed that the mcr-1 plasmids belonged to four different Inc groups (a new IncP-1 variant and the IncFII, IncHI1, and IncH families). Our results indicate that mcr-1 is circulating in clinical isolates of colistin-resistant Enterobacteriaceae in Colombia and is mainly harbored in transferable plasmids.

The rise of multidrug-resistant (MDR) bacteria represents a public health threat, with carbapenem resistance exacerbating this challenge. This study investigates carbapenemase-producing bacteria (CPB) across the Latin America and the Caribbean (LAC) region. A retrospective observational study was conducted across 12 LAC countries from 2015 to 2020. A total of 58,909 isolates were analyzed utilizing polymerase chain reaction (PCR) to detect key carbapenemases in Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter baumannii complex (ABC). 47,804/58,909 (81.14%) carbapenemases were identified, with Brazil accounting for 73% of these. The majority were reported in carbapenem-resistant Enterobacterales-CRE (65.33%; 31,230/47,804), followed by carbapenem-resistant ABC-CRAB (22.05%; 10,542/47,804), and carbapenem-resistant P. aeruginosa-CRPA (6050/47,804; 12.66%). Among CRE, bla _KPC was the most detected gene (78.67%; 24,569/31,230), with Klebsiella pneumoniae being the most commonly associated species (75.9%). A relevant upward trend in bla _NDM was observed. CRPA exhibited diverse profiles, with bla _VIM (47.64%) being the most common. In CRAB, bla _OXA-23 was found in 88.80% (9361/10,542) of isolates. Carbapenemase co-production was detected in 2.60% (1190/47,804) of isolates, with CRPA bla _IMP + bla _VIM being the most frequent. This study highlights a high prevalence of CPB in LAC, with a stable trend in bla _KPC but a rising trend in bla _NDM. These findings underscore the urgent need for strengthened surveillance and public health interventions to combat carbapenemase-mediated resistance in the region. None.

Neisseria meningitidis is one of the leading causes of bacterial meningitis. In 2013, an increase in invasive disease caused by N. meningitidis serogroup B occurred in Cartagena, Colombia. The aim of this study was to characterize serogroup B isolates recovered from patients with meningococcal meningitis in Cartagena during 2012 and 2014. Twenty-five isolates were collected through a national, laboratory-based surveillance, and phenotypic and genotypic characteristics were determined by serosubtyping, serotyping, antimicrobial susceptibility testing, repetitive sequence-based PCR (rep-PCR). MLST data available were also used. The B:10,15:nt phenotype, associated with clonal complex ST-41/44, was responsible for 68.0% of all cases. The clinical, epidemiological and molecular characterization of meningococcal disease is necessary for understanding the spread of virulent meningococcal clones and for facilitating the early detection of cases to reduce epidemic risks.

Pseudomonas aeruginosa is an opportunistic pathogen that causes multiple infections in hospitalized patients. This microorganism has developed resistance to several antimicrobial agents, including carbapenems, which are considered to be the last therapeutic option against these infections. Carbapenem resistance of P. aeruginosa is mediated by different mechanisms: Carbapenemases class B (MBL) and A, alterations in the OprD expression and overexpression of the Mex efflux pump. To describe the presence of carbapenemases in P. aeruginosa isolates from seven Colombian provinces. A total of 57 P. aeruginosa isolates were collected between September 2012 and March 2013 from national surveillance in Colombia and were sent to the Grupo de Microbiología at the Instituto Nacional de Salud (INS) for evaluation. Iidentification and antimicrobial susceptibility were confirmed through automated method (Vitek ® 2) and disk diffusion (Kirby-Bauer) according to the Clinical and Laboratory Standards Institute, CLSI, 2013. Phenotypic and genotypic confirmation was determined using the modified Hodge test (MHT), a synergism test using imipenem, EDTA-SMA and meropenem, and conventional PCR to detect the bla KPC, bla VIM, bla IMP and bla NDM genes. Of the 57 isolates, two showed sensitivity to carbapenems. Forty-three isolates were positive for carbapenemases with a high percentage of sensitivity to colistin (76.4%, n=42). The 43 isolates producing carbapenemases showed multiple drug resistance: 72.1% were positive in the MHT and 79.1% showed MBL synergism. PCR amplification confirmed that 33 isolates were positive for bla VIM, nine were positive for bla KPC and one isolate expressed both KPC and VIM carbapenemases. No isolates showed amplified products with bla IMP and bla NDM primers. The most frequent carbapenemase was VIM, followed by KPC in an approximate ratio of 3:1.