Liz Erika Cruz-Pio

Tocosh, an ancestral fermented potato product, relies on spontaneous processes near freshwater springs under extreme high-altitude conditions and represents an underexplored reservoir of microbial diversity with significant potential for the discovery of probiotics. This study provides, for the first time, a comprehensive probiogenomic characterization of 19 lactic acid bacteria (LAB) isolated from tocosh, in the Peruvian Andes, at three distinct altitudes—2992, 3882, and 4451 m above sea level (m.a.s.l.)—using whole genome sequencing (WGS) and bioinformatic profiling. A total of six species were identified: Lactiplantibacillus plantarum and Levilactobacillus brevis at all three study sites, Lacticaseibacillus paracasei and Lentilactobacillus buchneri at the lowest altitude (2992 m.a.s.l.), and Latilactobacillus curvatus and Latilactobacillus sakei at the highest altitudes (3882 and 4451 m.a.s.l.). Our results reveal that the extreme Andean environment is associated with stability in L. plantarum (genome sizes from 3.36 to 3.38 Mb) across all altitudinal levels. Functional analysis using CAZymes determined that L. brevis and L. buchneri act as primary degraders (high percentage of glycosyl hydrolases/carbohydrate binding) while L. curvatus and L. sakei function as primary builders through exopolysaccharide biosynthesis, likely a cryoprotective adaptation preventing cell damage during cold temperatures at high altitudes. Additionally, L. sakei and L. plantarum exhibited unique auxiliary activity (AA) enzymes, suggesting an oxidative mechanism to breach recalcitrant starch surfaces. All isolates were confirmed as genomically safe, lacking transferable antibiotic resistance genes and virulence factors. Pathogenic risk potential scores (PPRS) were consistently ≤2.0, fulfilling qualified presumption of safety (QPS) criteria. These findings provide the first genomic characterization of tocosh-associated LAB, establishing a basis for tocosh standardization, enabling the rational design of starter cultures that preserve ancestral traits and ensure microbiological safety in modern food applications.

Pseudomonas aeruginosa is an opportunistic pathogen associated with health care infections, it has high levels of antimicrobial resistance and is associated with hospital outbreaks. Early outbreak detection is a usual problem in hospitals, therefore, this study aimed to assess the clonal relationship of carbapenemaseproducing P. aeruginosa in a tertiary hospital in Lima, Peru. Twenty-four metallo β-lactamase-producing P. aeruginosa strains isolated from hospitalized patients were collected. The clonal relation was determined using the REP-PCR technique. REP-PCR band profiles were normalized, analyzed and combined using BioNumerics version 7.6 software. Molecular identification showed 19 different profiles and four clonal groups. We determined polyclonality among isolates. We did not find clonal dissemination among themetallo-β-lactamase-producing P. aeruginosa strains circulating in the hospital.

Los Enterococcus constituyen parte de la microbiota autóctona de quesos artesanales y contribuyen con el desarrollo del aroma y maduración de los quesos. Algunas cepas, sintetizan péptidos antimicrobianos denominados enterocinas y pueden suprimir el crecimiento de microorganismos patógenos contaminantes de alimentos. El objetivo, fue seleccionar y caracterizar cepas nativas de Enterococcus con actividad antimicrobiana de quesos artesanales. Para su aislamiento, las muestras fueron sembradas en agar bilis esculina y agar MRS. La caracterización fenotípica así como la detección de sustancias antimicrobianas, fueron realizadas por métodos bioquímicos, bicapa y difusión en agar respectivamente. De 68 cepas aisladas, Enterococcus faecium fue la especie predominante, seguida de Enterococcus durans y Enterococcus faecalis. Asimismo, nueve cepas mostraron actividad antimicrobiana contra bacterias taxonómicamente afines y patógenas contaminantes de alimentos. Las cepas Enterococcus faecium QPa.1 y QPa.2 ejercieron un efecto antagonista muy efectivo frente a Listeria monocytogenes. La sustancia antimicrobiana producida por E. faecium QPa.1 fue inactivada por tripsina y α-quimotripsina, pero no por catalasa. Además, dicha actividad fue estable a pH 3 y 9, a 100 °C por 20 min y a 4 y -20 °C durante 180 días. En conclusión, Enterococcus faecium QPa.1 produjo una bacteriocina activa y específica contra Listeria monocytogenes, con posibilidad de ser utilizada como un cultivo bioprotector para la preservación de quesos.

To determine the effect of three different freezing temperatures on post-freeze-drying survival rates of wine yeasts and lactic acid bacteria (LAB). To know if a similar freeze-drying protocol can be used for both micro-organisms. Cells from liquid culture media were recovered and concentrated in appropriate lyoprotectants. Aliquots of each strain were frozen at −20, −80 and −196°C before vacuum drying. Viable cell counts were done before freezing and after freeze-drying. Survival rates were calculated. Freezing temperatures differently affected yeast and bacteria survival. The highest survival rates were obtained at −20 and −80°C for yeasts, but at −196°C for LAB. Major differences in survival rates were recorded among freeze-dried yeasts, but were less drastic for LAB. Yeasts Pichia membranifaciens, Starmerella bacillaris and Metschnikowia pulcherrima, and LAB Lactobacillus paracasei, Pediococcus parvulus and Lactobacillus mali, were the most tolerant species to freeze-drying, regardless of freezing temperature. Yeast and LAB survival rates differed for each tested freezing temperature. For yeasts, −20°C ensured the highest post-freeze-drying viability and −196°C for LAB. Freezing temperature to freeze-dry cells is a crucial factor for ensuring good wine yeast and LAB survival. These results are important for appropriately preserving micro-organisms and for improving starter production processes.