Molecular typing and genetic environment of the blaKPC gene in Chilean isolates of Klebsiella pneumoniae.

The aim of this work was to determine the genetic environment and transferability of blaKPC as well as the pulsotypes of KPC-producing Klebsiella pneumoniae strains isolated from clinical samples in Chilean hospitals. Seventeen strains, principally isolated in Santiago (the capital of Chile) during the years 2012 and 2013, were included. The genetic environment of blaKPC was elucidated by PCR mapping and sequencing. Molecular typing was performed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Curing and conjugation experiments were performed with six strains of different sequence types (STs) and pulsotypes. Thirteen pulsotypes and six STs, mainly belonging to clonal complex 258, were found. In addition, seven strains belonged to a new ST assigned ST1161. The blaKPC sequence indicated that 16 strains had the KPC-2 variant; in only one strain (UC331) an amino acid change (R6P) was detected, corresponding to a new KPC variant designated KPC-24. Molecular characterisation of the blaKPC genetic environment revealed two distinct platforms, namely variant 1a and the Tn4401a isoform, with the first being the most common (11/17 strains). Mating experiments failed to produce transconjugants; however, loss of blaKPC was achieved by plasmid curing in all assayed strains. In conclusion, in Chilean strains of K. pneumoniae, blaKPC is primarily found associated with the variant 1a and is located in non-transferable plasmids. In addition, this study highlights the description of the new ST1161 and the new KPC-24 variant.

Analysis of molecular epidemiology of Chilean Salmonella enterica serotype enteritidis isolates by pulsed-field gel electrophoresis and bacteriophage typing.

Human Salmonella enterica serotype Enteritidis infections emerged in Chile in 1994. S. enterica serotype Enteritidis phage type 1 isolates predominated in the north, and phage type 4 isolates predominated in the central and southern regions. A study was planned to characterize this epidemic using the best discriminatory typing technique. Research involved 441 S. enterica serotype Enteritidis isolates, including clinical preepidemic samples (n = 74; 1975 to 1993) and epidemic (n = 199), food (n = 72), poultry (n = 57), and some Latin American (n = 39) isolates. The best method was selected based on a sample of preepidemic isolates, analyzing the discriminatory power (DP) obtained by phage typing and randomly amplified polymorphic DNA and pulsed-field gel electophoresis (PFGE) analysis. The highest DP was associated with BlnI PFGE-bacteriophage typing analysis (0.993). A total of 38 BlnI patterns (B patterns) were identified before the epidemic period, 19 since 1994, and only 4 in both periods. Two major clusters were identified by phylogenetic analysis, and the predominant B patterns clustered in the same branch. Combined analysis revealed that specific B pattern-phage type combinations (subtypes) disappeared before 1994, that different genotypes associated with S. enterica serotype Enteritidis phage type 4 had been observed since 1988, and that strain diversity increased before the expansion of S. enterica serotype Enteritidis in 1994. Predominant subtype B3-phage type 4 was associated with the central and southern regions, and subtype B38-phage type 1 was associated with the north (P < 0.0001). Food and poultry isolates matched the predominant S. enterica serotype Enteritidis subtypes, but isolates identified in neighboring countries (Peru and Bolivia) did not match S. enterica serotype Enteritidis subtypes identified in the north of Chile. The results of this work demonstrate that genetic diversity, replacement, and expansion of specific S. enterica serotype Enteritidis subtypes were associated with epidemic changes.

[Molecular epidemiology of a streptococcus pyogenes related nosocomial outbreak in a burn unit]. / Epidemiología molecular de un brote de infecciones por streptococcus pyogenes en una unidad de quemados.

BACKGROUND: Group A Streptococcal (GAS) infections have increased in frequency and severity worldwide. During April 1996, a nosocomial outbreak associated to GAS infections affected seven patients admitted to a pediatric burn unit. The causative organism was likely disseminated from the source patient to another child in the emergency room before he was transferred to the burn unit. Patients developed burn infections or invasive disease. One of them died due to a toxic shock syndrome and 3 other lost their skin grafts. Perineal and nasal microbiological surveillance of 42 related health care workers identified only one of them as carrier of S pyogenes. AIM: To report a molecular analysis of an apparently clonal outbreak. MATERIAL AND METHODS: The available isolates were analyzed by molecular methods including random amplified polymorphic DNA analysis (RAPD) with 4 different primers, Sma-I pulsed field gel electrophoresis (PFGE) analysis, and speA, speB and speC detection by polymerase chain reaction (PCR). RESULTS: Two phylogenetically distant and sequentially isolated bacterial groups were identified either by RAPD analysis with selected primers or by Smal-PFGE analysis. The first group involved isolates identified in two patients that included the lethal case. The second bacterial group comprised 5 clinical isolates and the perineal and nasal isolates obtained from a health care worker. Only strains belonging to the first group harbored the speA gene and were associated with invasive disease. The second group could be split further in two subgroups according to their speB profile. CONCLUSIONS: RAPD analysis with selected primers can reproduce the PFGE-discriminating ability on the epidemiological analysis of GAS infections.

Salmonella enteritidis, un patógeno entérico ligado a la industria de los alimentos / Salmonella enteritidis, an enteric pathogen related to the industry of foods

Chile ha experimentado un cambio epidemiológico en la última década con la desaparición progresiva de la fiebre tifoidea, causada mayoritariamente por Salmonella Typhi y la emergencia epidémica de Salmonella Enteritidis, un agente de diarrea sin tratamiento antibiótico eficaz y ligado estrechamente a productos avícolas contaminados e inadecuadamente preparados. La fiebre tifoidea ha disminuido su importancia debido al desarrollo humano experimentado en Chile con un alto grado de cobertura de agua potable y de manejo de excretas que, en conjunto con un mayor nivel de educación, han limitado la contaminación del ambiente por este agente y la adquisición de él por huéspedes susceptibles. A pesar de este notable avance, un nuevo serotipo de Salmonella ha irrumpido en Chile, denominado Enteritidis, que ha logrado aprovechar el nuevo escenario obtenido con la industrialización avícola donde miles de aves convivenen pequeños espacios, facilitando la infección cruzada entre ellas. La contaminación intermitente de huevos, ya sea por vía transovárica o superficial, ha permitido la llegada de este agente en forma errática, pero persistente al ser humano. Este nuevo panorama obliga a que nuestro país adopte estrategias de prevención que involucran a productores, distribuidores y consumidores de productos avícolas