ALBERT

Description: Acinetobacter baumannii is an opportunistic pathogen primarily associated with multidrug-resistant nosocomial infections, for which polymyxins are the last-resort antibiotics. This study investigated carbapenem-resistant A. baumannii strains exhibiting an extensively drug-resistant (XDR) phenotype, including four isolates considered locally pan drug-resistant (LPDR), isolated from inpatients during an outbreak at a teaching hospital in Brazil. ApaI DNA macrorestriction followed by PFGE clustered the strains in three pulsotypes, named A to C, among carbapenem-resistant A. baumannii strains. Pulsotypes A and B clustered six polymyxin-resistant A. baumannii strains. MLST analysis of representative strains of pulsotypes A, B, and C showed that they belong, respectively, to sequence types ST1 (clonal complex, CC1), ST79 (CC79), and ST903. Genomic analysis of international clones ST1 and ST79 representative strains predicted a wide resistome for β-lactams, aminoglycosides, fluoroquinolones, and trimethoprim-sulfamethoxazole, with blaOXA–23 and blaOXA–72 genes encoding carbapenem resistance. Amino acid substitutions in PmrB (Thr232Ile or Pro170Leu) and PmrC (Arg125His) were responsible for polymyxin resistance. Although colistin MICs were all high (MIC ≥ 128 mg/L), polymyxin B MICs varied; strains with Pro170Leu substitution in PmrB had MICs 〉 128 mg/L, while those with Thr232Ile had lower MICs (16–64 mg/L), irrespective of the clone. Although the first identified polymyxin-resistant A. baumannii strain belonged to ST79, the ST1 strains were endemic and caused the outbreak most likely due to polymyxin B use. The genome comparison of two ST1 strains from the same patient, but one susceptible and the other resistant to polymyxin, revealed mutations in 28 ORFs in addition to pmrBC. The ORF codifying an acyl-CoA dehydrogenase has gained attention due to its fatty acid breakdown and membrane fluidity involvement. However, the role of these mutations in the polymyxin resistance mechanism remains unknown. To prevent the dissemination of XDR bacteria, the hospital infection control committee implemented the patient bathing practice with a 2% chlorhexidine solution, a higher concentration than all A. baumannii chlorhexidine MICs. In conclusion, we showed the emergence of polymyxin resistance due to mutations in the chromosome of the carbapenem-resistant A. baumannii ST1, a high-risk global clone spreading in this hospital.

Description: Fungi are a rich source of bioactive compounds. Fungal cocultivation is a method of potentiating chemical interactions and, consequently, increasing bioactive molecule production. In this study, we evaluated the bactericidal, antiprotozoal, and cathepsin V inhibition activities of extracts from axenic cultures of 6 fungi (Fusarium guttiforme, Pestalotiopsis diospyri, Phoma caricae-papayae, Colletotrichum horii, Phytophthora palmivora, and C. gloeosporioides) that infest tropical fruits and 57 extracts obtained by their cocultivation. Our results reveal that fungal cocultivation enhances the biological activity of the samples, since all extracts that were active on Gram-positive bacteria, Gram-negative bacteria, Trypanosoma cruzi, and Leishmania infantum were obtained from cocultivation. Bacterial growth is either totally or partially inhibited by 46% of the extracts. Two extracts containing mainly fusaric and 9,10-dehydrofusaric acids were particularly active. The presence of the fungus F. guttiforme in co-cultures that give rise to extracts with the highest activities against L. infantum. An axenic culture gave rise to the most active extract for the inhibition of cathepsin V; however, other coculture extracts also exhibited activity toward this biological target. Therefore, the results of the biological activities indicate that fungal cocultivation increased the biological potential of samples, likely due to the hostile and competitive environment that pushes microorganisms to produce substances important for defense and allows access to metabolic routes then silenced in milder cultivation conditions.