Salmonella enterica Serovars Dublin and Enteritidis Comparative Proteomics Reveals Differential Expression of Proteins Involved in Stress Resistance, Virulence, and Anaerobic Metabolism.

The Enteritidis and Dublin serovars of Salmonella enterica are phylogenetically closely related yet differ significantly in host range and virulence. S Enteritidis is a broad-host-range serovar that commonly causes self-limited gastroenteritis in humans, whereas S Dublin is a cattle-adapted serovar that can infect humans, often resulting in invasive extraintestinal disease. The mechanism underlying the higher invasiveness of S Dublin remains undetermined. In this work, we quantitatively compared the proteomes of clinical isolates of each serovar grown under gut-mimicking conditions. Compared to S Enteritidis, the S Dublin proteome was enriched in proteins linked to response to several stress conditions, such as those encountered during host infection, as well as to virulence. The S Enteritidis proteome contained several proteins related to central anaerobic metabolism pathways that were undetected in S Dublin. In contrast to what has been observed in other extraintestinal serovars, most of the coding genes for these pathways are not degraded in S Dublin. Thus, we provide evidence that S Dublin metabolic functions may be much more affected than previously reported based on genomic studies. Single and double null mutants in stress response proteins Dps, YciF, and YgaU demonstrate their relevance to S Dublin invasiveness in a murine model of invasive salmonellosis. All in all, this work provides a basis for understanding interserovar differences in invasiveness and niche adaptation, underscoring the relevance of using proteomic approaches to complement genomic studies.

Intra-peritoneal abscess after an abdominal hysterectomy involving Cutibacterium avidum (former Propionibacterium avidum) highly resistant to clindamycin.

Cutibacterium avidum is a gram-positive anaerobic rod belonging to the cutaneous group of human bacteria with preferential colonization of sweat glands in moist areas. The microorganism rarely cause disease, generally delayed prosthetic joint infections (PJIs). We describe the second case of intraperitoneal abscess by C. avidum after an abdominal surgery in an obese female patient and the first case after a non-prosthetic abdominal surgery due to a highly clindamycin resistant strain in a patient with underling conditions. The patient was successfully treated with surgical drainage and beta-lactam antibiotics. Although rare and apparently non-pathogenic, C. avidum may be involved in infections, especially in some high-risk patients with obesity who have undergone surgical incision involving deep folder of the skin. The microorganism was identified by phenotypic methods, MALDI-TOF MS and 16S rRNA gene sequencing. Susceptibility test should be performed in C. avidum because high level resistance to clindamycin could be present. We present a literature review of C. avidum infections.

Widespread dispersion of the resistance element tet(B)::ISCR2 in XDR Acinetobacter baumannii isolates.

Acinetobacter baumannii is a significant nosocomial pathogen often associated with extreme drug resistance (XDR). In Argentina, isolates of A. baumannii resistant to tetracyclines have accounted for more than 40% of drug-resistant isolates in some hospitals. We have previously reported the dispersion of the tet(B) resistance element associated with the ISCR2 transposase in epidemiologically unrelated A. baumannii isolates recovered from 1983 to 2011. This study extends this surveillance to 77 recent (2009-2013) XDR A. baumannii isolates with different levels of minocycline susceptibility. Isolates were examined by a pan-PCR assay, which showed six different amplification patterns, and specific PCRs were used for the confirmation of the the ΔISCR2-tet(B)-tet(R)-ISCR2 element. The tet(B) gene was present in 66 isolates and the ISCR2 element in 68 isolates; the tet(B) gene was associated with ISCR2 in all tet(B)-positive isolates. We conclude that this element is widespread in XDR A. baumannii isolates from Argentina and could be responsible for the emergence of tetracycline resistance in recent years.

Genetic Variability of AdeRS Two-Component System Associated with Tigecycline Resistance in XDR-Acinetobacter baumannii Isolates.

The emergence of tigecycline resistance has increased in the last years. Although tigecycline-resistant Acinetobacter baumannii isolates were described all over the world, few reports regarding the molecular basis of this resistance are available. It has been recognized that the overexpression of AdeABC efflux pump is related to the tigecycline-resistant phenotype. In 37 clinical A. baumannii isolates we first determined the tigecycline-resistant phenotype and then, within a selected group, we analyzed the sequence of the adeRS operon, which is involved in the expression of the AdeABC efflux pump. Nucleotide sequence analysis of adeR and adeS showed the presence of 5 and 16 alleles, respectively. These results expose a high genetic variability in both genes, the adeS gene being more susceptible to genetic variation. The presence of 2 AdeR and 2 AdeS new variants were reported. Two of the new AdeRS variants were present in the intermediate and the resistant tigecycline A. baumannii isolates, suggesting a putative role in the development of the observed phenotype. More studies need to be addressed to determine the role of the genetic variability observed in the adeRS operon.