Caracterización de cepas clínicas y ambientales de Salmonella enterica subsp. enterica serovar Heidelberg aisladas en Chile / Characterization of Salmonella Heidelberg strains isolated in Chile

Background: Salmonella Heidelberg (S. Heidelberg) causes gastroenteritis and sometimes bacteremia and endocarditis. In other countries, this serovar has multidrug resistance including extended-spectrum β-lactamases (ESBLs) and AmpC (β-lactamases (AmpC), associated with the blaCMY-2 gene. In Chile, an outbreak by S. Heidelberg occurred in 2011, the phenotypic and genetic characteristics of Chilean strains are unknown. Aim: To determine the antimicrobial susceptibility, presence of plasmids and virulence factor genes in S. Heidelberg strains isolated in Chile over the period 2006-2011. Material and Methods: In sixty-one S. Heidelberg clinical and environmental strains collected by the Public Health Institute in Chile during 2006-2011, antimicrobial susceptibility, plasmids and virulence factor genes (invA, sifA, pefA, agfA, lpfA and, stkD) were studied. Results: S. Heidelberg had a high susceptibility to sulfamethoxazole-trimethoprim, gentamicin, ceftriaxone, ceftiofur, chloramphenicol, amoxicillin-clavulanic acid and ampicillin. However, 52% had decreased susceptibility to ciprofloxacin and 33% resistance to tetracycline. ESBLs were detected in three strains isolated from blood cultures, environment and human feces. The latter strain was positive for AmpC and blaCMY-2 gene. Fifty three of 61 strains showed one to seven plasmids of 0.8 to approximately 30 kb. Most plasmids were small with sizes between 0.8 and 2 kb. All isolates were positive for all genes except pefA. Conclusions: S. Heidelberg isolated from Chilean samples was susceptible to first-line antimicrobials, except tetracycline and ciprofloxacin. The emergence of strains with ESBLs and AmpC should be a warning. The strains were homogeneous for virulence genes, but heterogeneous in their plasmids.

Reporte de cuatro casos clínicos de bacteriemia por Hafnia alvei en una unidad cardio-quirúrgica pediátrica / Report of four clinical cases of Hafnia alvei bacteremia in a pediatric cardiac surgery unit

Introduction: The gram-negative bacillus Hafnia alvei is the only species of the genus Hafnia, family Enterobacteriaceae. It occasionally behaves as an opportunistic pathogen in humans, causing intestinal and respiratory infection and sepsis. It rarely causes bacteremia, usually of unknown focus. Objective: To describe a nosocomial outbreak of four pediatric patients with bacteremia by Hafnia alvei. Methods: Descriptive study using clinical records of pediatric patients diagnosed with Hafnia alvei bacteremia in a pediatric cardio surgical unit, in October 2008. Results: The attack rate was 4/8 (50 percent), lethality rate 2/4 (50 percent) and mortality 2/8 (25 percent). The microbiological study and pulsed-field gel electrophoresis confirmed the same clonal bacterial strain. Discussion: The source of bacteremia was identified only in two patients and was associated with central venous catheters. The other two cases had no known infectious source. Epidemiological surveillance of emerging agents must be maintained.

Introducción: Hajhia alvei, bacilo Gram negativo, constituye la única especie del género Hajhia, familia Enterobacteriaceae. En el humano se comporta ocasionalmente como oportunista produciendo infección intestinal, respiratoria y sepsis. Es causa infrecuente de bacteriemias, generalmente de foco infeccioso desconocido. Objetivo: Describir un brote intrahospitalario de cuatro pacientes pediátricos con bacteriemias por Hajhia alvei. Método: Estudio descriptivo retrospectivo de los registros clínicos de cuatro pacientes pediátricos con diagnóstico de bacte-riemia por Hajhia alvei en una unidad cardioquirúrgica pediátrica identificados en octubre del 2008. Resultados: La tasa de ataque fue 4/8 (50 por ciento), tasa de letalidad 2/4 (50 por ciento) y de mortalidad de 2/8 (25 por ciento). El estudio micro-biológico y la electroforesis de campo pulsado confirman la misma cepa bacteriana clonal. Discusión: Se identificó el origen de la bacteriemia sólo en dos pacientes asociado a catéter venoso central. Los otros dos casos no tuvieron foco infeccioso conocido. Se debe mantener vigilancia epidemiológica de agentes emergentes.

Subtipificación molecular de Salmonella entérica serotipo Enteritidis en el período post epidémico / Molecular subtyping of Salmonella enterica serotype Enteritidis in a post epidemic period

Background: In the last two decades, Salmonella enterica serotype Enteritidis has become one of the main agents causing food borne diseases worldwide. This agent is transmitted mainly by contaminated meat and poultry. Aim: To determine the genetic subtypes of Salmonella enterica serotype Enteritidis, circulating in Chile between 2001 and 2003, a post epidemc period. Material and methods: One hundred ninety three isolates coming from human samples, prepared foods and animal products for human consumption, were analyzed bypulsed field electrophoresis, using PulseNet standardized protocol. Results: Thirteen subtypes of Salmonella enterica serotype Enteritidis were identified, that had between 0 and 13 bands. A predominant subtype was identified in 172 strains (88%) that carne from human isolates, prepared foods and animal producís for human consumption. Other four subtypes, found in prepared foods and animal products for human consumption, were also found in human isolales. Most subtypes were lighlly inlerrelaled Subtypes II, VIII and XI were also found in the 1994 epidemic. Conclusions: Subtyping of baclerial strains by pulsed field electrophoresis is useful for the surveillance of food borne diseases.

Identificación rápida de micobacterias no tuberculosas mediante análisis de patrones de restricción / Rapid identification of non tuberculous mycobacteria by restriction pattern analysis

Background: The frequency of diseases caused by non tuberculous mycobacteria has increased in the last years. Their clinical diagnosis is difficult, mainly in immunocompromised patients. The identification of these mycobacteria by traditional methods is based on phenotypic characteristics and the results are obtained two to four weeks after their isolation in primary cultures. Aim: To report a new identification method for non tuberculous mycobacteria. Material and methods: The restriction pattern analysis method was implemented. It is based on the amplification, using polymerase chain reaction (PCR), of a polymorphic region of 440 base pairs that codifies Hsp65 protein, followed by a digestion with BstE II and Hae III restriction enzymes. The results were compared with patterns established for each strain. Results: Sixty four strains of mycobacteria obtained from clinical samples and seven reference mycobacteria, were identified using the traditional methods and restriction pattern analysis. The latter method identified the same strain as the former in 87.5% of cases. In the remainder 12.5% of cases there was no agreement between both methods. In these, the sequencing of a fragment of a gene that codifies 16S ribosomal RNA, confirmed the correct identification by restriction patterns. Conclusions: Restriction pattern analysis is a rapid identification method for non tuberculous mycobaterial strains.