Clostridioides difficile infection (CDI) is currently one of the most important causes of infectious diarrhea in developed countries and the main cause in healthcare settings. Here, we characterized the gut microbiota from the feces of 57 patients with diarrhea from nosocomial and community-acquired CDI. We performed an ecological analysis by high-throughput sequencing of the V3-V4 region of 16S rRNA amplicons and evaluated the association of the various ecological profiles with CDI risk factors. Among all samples Bacteroidaceae 31.01%, Enterobacteriaceae 9.82%, Lachnospiraceae 9.33%, Tannerellaceae 6,16%, and Ruminococcaceae 5.64%, were the most abundant families. A reduced abundance of Bacteroides was associated with a poor CDI prognosis, with severe diarrhea and a high incidence of recurrence. This reduction was associated with a weakened host immune system and previous aggressive antibiotherapy. Peptostreptococcaceae family was 1.56% overall and within the family the only identified member was the genus Clostridioides, positively correlated with the presence of Akkermansia that may be predictive of the presence of a CDI. Finally, a relevant aspect that must be considered in clinical practice is the misdiagnosis of CDI, as patients with a stool sample that tests positive for C. difficile are usually diagnosed with CDI and subsequently treated as such. However, co-infection with other pathogenic agents often plays an important role in the development of diarrhea, and must be considered when prescribing antibiotic treatment.

Smooth lipopolysaccharide (S-LPS) and lipid A of Brucella abortus and Brucella melitensis induced the production of nitric oxide (NO) by rat adherent peritoneal cells, but they induced lower levels of production of NO than Escherichia coli LPS. The participation of the inducible isoform of NO synthase (iNOS) was confirmed by the finding of an increased expression of both iNOS mRNA and iNOS protein. These observations might help to explain (i) the acute outcome of Brucella infection in rodents, (ii) the low frequency of septic shock in human brucellosis, and (iii) the prolonged intracellular survival of Brucella in humans.Members of the genus Brucella are gram-negative bacteria that produce chronic infections in a large number of mammals, including humans (10). Brucella species are facultative intracellular pathogens which survive within a variety of cells, including macrophages, and the virulence of these species and the establishment of chronic infections by them are thought to be essentially due to their ability to avoid the killing mechanisms within macrophages (3, 36). The molecular mechanisms accounting for these properties are incompletely understood, and only some aspects of the processes involved have been identified as yet. Brucella does not evade phagocytosis by macrophages or neutrophils (6) but inhibits the degranulation of both primary and secondary neutrophil granules (30,33,34) and the myeloperoxidase-hydrogen peroxide-halide system (5, 7). The virulence of Brucella abortus, Brucella melitensis, and Brucella suis is associated with the smooth colony morphotype which contains the full lipopolysaccharide (LPS) (36, 38). The low biological activity induced by Brucella smooth LPS (S-LPS) compared with that produced by enterobacterial endotoxin might be one of the factors contributing to the survival of these pathogens in phagocytic cells (32). Further, a major proportion of the protective antibody response is directed against the O-chain component of the S-LPS (11) and Brucella LPS itself is a virulent factor because it is the main cause of the resistance of Brucella to lysosomal cationic proteins (15).Nitric oxide (NO) has been shown to play an important role in diverse functions, including vasoregulation, neurotransmission, immune response regulation (23, 24, 37), and macrophage-mediated cytotoxic activity against tumor cells and a variety of pathogens, including bacteria, fungi, viruses, helminths, and protozoa (22). NO has been implicated in host defenses against intracellular pathogens and might play a role in persistent or latent infections (14). NO is derived from L-arginine in a reaction catalyzed by the enzyme NO synthase (NOS), of which three different isoforms have been identified (29). The inducible isoform of NOS (iNOS) is responsible for the highoutput path of NO production involved in antimicrobial activity (28). iNOS expression is induced by proinflammatory cytokines such as gamma interferon (IFN-␥), tumor necrosis factor alpha, and interleukin 1 (IL-1), as well as by microbial product...

An extensively drug-resistant (XDR) Klebsiella pneumoniae isolate MS3802 from a tracheostomy exudate was whole-genome sequenced using MiSeq and Oxford Nanopore MinION platforms in order to identify the antimicrobial resistance and virulence determinates and their genomic context. Isolate MS3802 belonged to the clone ST23 and presented a capsular serotype K1, associated with hypervirulent K. pneumoniae (hvKp) isolates. The isolate harboured a chromosomally encoded blaCTX-M-15 gene and contained a large IncHI1B hybrid virulence/resistance plasmid carrying another copy of the blaCTX-M-15 and the virulence factors iucABCD-iutA, iroBCDN, rmpA and rmpA2. The carbapenemase gene blaOXA-48 was found in a Tn1999-like transposon and the 16S rRNA methylase armA gen located in the vicinity of other antibiotic-resistant genes on an IncM2 plasmid. This study represents, to the best of our knowledge, the first description of a blaCTX-M-15-, blaOXA-48- and armA-harbouring K. pneumoniae of ST23 and capsular serotype K1 in Spain. Our report emphasizes the importance of implementing new surveillance strategies to monitor the risk of emergence and spread of such XDR and hypervirulent K. pneumoniae isolates.

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