Comprehensive study reveals phenotypic heterogeneity in Klebsiella pneumoniae species complex isolates.

Here, we conducted a comprehensive analysis of 356 Klebsiella pneumoniae species complex (KpSC) isolates that were classified as classical (cl), presumptive hypervirulent (p-hv) and hypermucoviscous-like (hmv-like). Overall, K. pneumoniae (82.3%), K. variicola (2.5%) and K. quasipneumoniae (2.5%) were identified. These isolates comprised 321 cl-KpSC, 7 p-hv-KpSC and 18 hmv-like-KpSC. A large proportion of cl-KpSC isolates were extended-spectrum-ß-lactamases (ESBLs)-producers (64.4%) and 3.4% of isolates were colistin-resistant carrying carbapenemase and ESBL genes. All p-hv-KpSC showed an antibiotic susceptible phenotype and hmv-like isolates were found to be ESBL-producers (8/18). Assays for capsule production and capsule-dependent virulence phenotypes and whole-genome sequencing (WGS) were performed in a subset of isolates. Capsule amount differed in all p-hv strains and hmv-like produced higher capsule amounts than cl strains; these variations had important implications in phagocytosis and virulence. Murine sepsis model showed that most cl strains were nonlethal and the hmv-like caused 100% mortality with 3 × 108 CFUs. Unexpectedly, 3/7 (42.9%) of p-hv strains required 108 CFUs to cause 100% mortality (atypical hypervirulent), and 4/7 (57.1%) strains were considered truly hypervirulent (hv). Genomic analyses confirmed the diverse population, including isolates belonging to hv clonal groups (CG) CG23, CG86, CG380 and CG25 (this corresponded to the ST3999 a novel hv clone) and MDR clones such as CG258 and CG147 (ST392) among others. We noted that the hmv-like and hv-ST3999 isolates showed a close phylogenetic relationship with cl-MDR K. pneumoniae. The information collected here is important to understand the evolution of clinically important phenotypes such as hypervirulent and ESBL-producing-hypermucoviscous-like amongst the KpSC in Mexican healthcare settings. Likewise, this study shows that mgrB inactivation is the main mechanism of colistin resistance in K. pneumoniae isolates from Mexico.

Septic shock from disseminated tuberculosis with splenic tuberculous abscess.

Splenic tuberculosis is a little-known and difficult to diagnose entity due to its low presentation of symptoms. It corresponds to one of the forms of extrapulmonary presentation of the disease, which in turn have a greater association with immunocompromised states such as diabetes mellitus. We present the case of a patient with diabetes mellitus who was admitted in the context of septic shock secondary to a probable splenic abscess, requiring surgical intervention. A total splenectomy was performed, managing to isolate Mycobacterium tuberculosis from the surgical specimen.

La tuberculosis esplénica es poco conocida y de difícil diagnóstico por su escasa presentación de síntomas. Corresponde a una de las formas de presentación extrapulmonar de la enfermedad, las cuales tienen mayor asociación con estados de inmunocompromiso, como la diabetes mellitus. Presentamos el caso de un paciente con diabetes mellitus que ingresó con choque séptico secundario a un probable absceso esplénico, requiriendo intervención quirúrgica en la que se llevó a cabo esplenectomía total y estudio histopatológico, con identificación de Mycobacterium tuberculosis en la pieza quirúrgica.