Search Results (5)

Among carbapenem-resistant Enterobacterales (CRE) are diverse mechanisms, including those that are resistant to meropenem but susceptible to ertapenem, adding further complexity to the clinical landscape. This study investigates the emergence of ertapenem-resistant, meropenem-susceptible (ErMs) Escherichia coli and Klebsiella pneumoniae CRE across five hospitals in San Antonio, Texas, USA, from 2012 to 2018. The majority of the CRE isolates were non-carbapenemase producers (NCP; 54%; 41/76); 56% of all NCP isolates had an ErMs phenotype. Among ErMs strains, E. coli comprised the majority (72%). ErMs strains carrying bla_CTX-M had, on average, 9-fold higher copies of bla_CTX-M than CP-ErMs strains as well as approximately 4-fold more copies than bla_CTX-M-positive but ertapenem- and meropenem-susceptible (EsMs) strains (3.7 vs. 0.9, p < 0.001). Notably, carbapenem hydrolysis was observed to be mediated by strains harboring bla_CTX-M with and without a carbapenemase(s). ErMs also carried more mobile genetic elements, particularly IS26 composite transposons, than EsMs (37 vs. 0.2, p < 0.0001). MGE- ISVsa5 was uniquely more abundant in ErMs than either EsMs or ErMr strains, with over 30 more average ISVsa5 counts than both phenotype groups (p < 0.0001). Immunoblot analysis demonstrated the absence of OmpC expression in NCP-ErMs E. coli, with 92% of strains lacking full contig coverage of ompC. Overall, our findings characterize both collaborative and independent efforts between bla_CTX-M and OmpC in ErMs strains, indicating the need to reappraise the term “non-carbapenemase (NCP)”, particularly for strains highly expressing bla_CTX-M. To improve outcomes for CRE-infected patients, future efforts should focus on mechanisms underlying the emerging ErMs subphenotype of CRE strains to develop technologies for its rapid detection and provide targeted therapeutic strategies. Full article

Carbapenem-resistant Acinetobacter baumannii (CRAB) is designated as an urgent public health threat, both due to its remarkable multidrug resistance and propensity for clonal spread. This study aimed to explore the phenotypic and molecular characteristics of antimicrobial resistance in CRAB isolates (n = 73) from intensive care unit (ICU) patients in two university hospitals in Bulgaria (2018–2019). The methodology included antimicrobial susceptibility testing, PCR, whole-genome sequencing (WGS), and phylogenomic analysis. The resistance rates were as follows: imipenem, 100%; meropenem, 100%; amikacin, 98.6%; gentamicin, 89%; tobramycin, 86.3%; levofloxacin, 100%; trimethoprim–sulfamethoxazole, 75.3%; tigecycline, 86.3%; colistin, 0%; and ampicillin–sulbactam, 13.7%. All isolates harbored bla_OXA-51-like genes. The frequencies of distribution of other antimicrobial resistance genes (ARGs) were: bla_OXA-23-like, 98.6%; bla_{OXA-24/40-like}, 2.7%; armA, 86.3%; and sul1, 75.3%. The WGS of selected extensively drug-resistant A. baumannii (XDR-AB) isolates (n = 3) revealed the presence of OXA-23 and OXA-66 carbapenem-hydrolyzing class D β-lactamases in all isolates, and OXA-72 carbapenemase in one of them. Various insertion sequencies, such as ISAba24, ISAba31, ISAba125, ISVsa3, IS17, and IS6100, were also detected, providing increased ability for horizontal transfer of ARGs. The isolates belonged to the widespread high-risk sequence types ST2 (n = 2) and ST636 (n = 1) (Pasteur scheme). Our results show the presence of XDR-AB isolates, carrying a variety of ARGs, in Bulgarian ICU settings, which highlights the crucial need for nationwide surveillance, especially in the conditions of extensive antibiotic usage during COVID-19. Full article

Salmonella enterica is, globally, an important cause of human illness with beef being a significant attributable source. In the human patient, systemic Salmonella infection requires antibiotic therapy, and when strains are multidrug resistant (MDR), no effective treatment may be available. MDR in bacteria is often associated with the presence of mobile genetic elements (MGE) that mediate horizontal spread of antimicrobial resistance (AMR) genes. In this study, we sought to determine the potential relationship of MDR in bovine Salmonella isolates with MGE. The present study involved 111 bovine Salmonella isolates obtained collectively from specimens derived from healthy cattle or their environments at Midwestern U.S. feedyards (2000–2001, n = 19), or specimens from sick cattle submitted to the Nebraska Veterinary Diagnostic Center (2010–2020, n = 92). Phenotypically, 33/111 isolates (29.7%) were MDR (resistant to ≥3 drug classes). Based on whole-genome sequencing (WGS; n = 41) and PCR (n = 111), a MDR phenotype was strongly associated (OR = 186; p < 0.0001) with carriage of ISVsa3, an IS91-like Family transposase. In all 41 isolates analyzed by WGS ((31 MDR and 10 non-MDR (resistant to 0–2 antibiotic classes)), MDR genes were associated with carriage of ISVsa3, most often on an IncC type plasmid carrying bla_CMY-2. The typical arrangement was floR, tet(A), aph(6)-Id, aph(3″)-Ib, and sul2 flanked by ISVsa3. These results suggest that AMR genes in MDR S. enterica isolates of cattle are frequently associated with ISVsa3 and carried on IncC plasmids. Further research is needed to better understand the role of ISVsa3 in dissemination of MDR Salmonella strains. Full article

Gallibacterium (G.) anatis isolates associated with respiratory diseases in calves and harboring acquired antimicrobial resistance genes have been described in Belgium. The aim of this study was to analyze the genetic organization of acquired resistance genes in the G. anatis isolate IMT49310 from a German calf suffering from a respiratory tract infection. The isolate was submitted to antimicrobial susceptibility testing, and a closed genome was obtained by a hybrid assembly of Illumina MiSeq short-reads and MinION long-reads. Isolate IMT49310 showed elevated MIC values for macrolides, aminoglycosides, florfenicol, tetracyclines, and trimethoprim/sulfamethoxazole. The acquired resistance genes catA1, floR, aadA1, aadB, aphA1, strA, tet(M), tet(B), erm(B), and sul2 were identified within three resistance gene regions in the genome, some of which were associated with IS elements, such as ISVsa5-like or IS15DII. Furthermore, nucleotide exchanges within the QRDRs of gyrA and parC, resulting in amino acid exchanges S83F and D87A in GyrA and S80I in ParC, were identified. Even if the role in the pathogenesis of respiratory tract infections in cattle needs to be further investigated, the identification of a G. anatis isolate with reduced susceptibility to regularly used antimicrobial agents in cases of fatal bovine respiratory tract infections is worrisome, and such isolates might also act as a reservoir for antimicrobial resistance genes. Full article

A total of 43 A. baumannii strains, isolated from 43 patients affected by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and by bacterial sepsis, were analyzed by antimicrobial susceptibility testing. All strains were resistant to almost three different classes of antibiotics, including carbapenems and colistin. The whole-genome sequencing (WGS) of eight selected A. baumannii isolates showed the presence of different insertion sequences (ISs), such as ISAba13, ISAba26, IS26, ISVsa3, ISEc29, IS6100 and IS17, giving to A. baumannii a high ability to capture and mobilize antibiotic resistance genes. Resistance to carbapenems is mainly mediated by the presence of OXA-23, OXA-66 and OXA-82 oxacillinases belonging to OXA-51-like enzymes. The presence of AmpC cephalosporinase, ADC-25, was identified in all A. baumannii. The pathogenicity of A. baumannii was exacerbated by the presence of several virulence factors. The multi-locus sequence typing (MLST) analysis showed that all strains belong to sequence type 2 (ST) international clone. Full article