Sonia Téllez

Polymorphism of genes encoding PmrAB in colistin-resistant strains of Escherichia coli and Salmonella enterica isolated from poultry and swine

OBJECTIVES To detect the occurrence of low susceptibility to colistin (polymyxin E), a last-resort antimicrobial, among enterobacteria isolated from samples of animal origin (poultry and swine) and to find out the molecular basis of colistin resistance. METHODS Salmonella enterica and Escherichia coli were isolated from eggs and swine samples. Bacterial strains were screened for colistin resistance by using MIC determinations interpreted according to EUCAST recommendations. pmrAB genes were amplified by PCR from bacterial isolates and their sequences were characterized. RESULTS Nine colistin-resistant strains were detected in a collection of 739 enterobacteria (S. enterica and E. coli) isolated from animal samples taken in different environments. Sequences encoding the PmrAB two-component sensor-regulator from two colistin-resistant E. coli strains isolated from swine faeces presented three non-synonymous polymorphisms, producing the variants 39S → I and 81R → S of PmrA and 161V → G of PmrB, among which the involvement of mutations in PmrA-81 and PmrB-161 in resistance to the antimicrobial had been previously shown. No variation at the protein level was detected after analysis of PmrAB sequences from seven colistin-resistant S. enterica strains. CONCLUSIONS E. coli strains carrying mutations in PmrAB that confer resistance to polymyxins, which might have evolved in vivo and have been rarely detected, are described for the first time in enterobacteria isolated from animals.

Salmonella septicaemia in a beauty snake (Elaphe taeniura taeniura).

THE presence of Salmonella species in the intestines of reptiles has been documented since 1944 (Hinshaw and McNeil 1944). For many years it has been thought that diverse serotypes of salmonella represent part of the normal microbiota of the intestines of reptiles (Chiodini and Sundberg 1981, Dorrestein and others 2000). Nevertheless, it became obvious that besides being mere faecal carrier status or just minor subclinical infections in reptiles, salmonella can also result in severe, often fatal, diseases (Johnson-Delaney 1996), including gastroenteritis and septicaemia (Hinshaw and McNeil 1946, Boever and Williams 1975, Jacobson 1978, Frye 1991). This depends upon the virulence of the serotype, the nature and chronicity of the lesions, and the innate immunity of the reptile host (Hoff and Hoff 1984). In all cases, poor husbandry, maladaptability, stress and malnutrition have been identified as predisposing factors (Gobel and others 1991). This short communication describes the clinical, pathological and microbiological findings in a case of systemic salmonellosis in a beauty snake (Elaphe taeniura taeniura). An adult female beauty snake was found dead in its cage without having shown any signs of disease over the previous 24 hours. It formed part of a private reptile collection which

SEPTICEMIC SALMONELLOSIS CAUSED BY SALMONELLA HESSAREK IN WINTERING AND MIGRATING SONG THRUSHES (TURDUS PHILOMELOS) IN SPAIN

We investigated two mortality events in wintering and migrating Song Thrushes (Turdus philomelos) in Catalonia, northeastern Spain in 2009 and 2010. Both episodes occurred in late February to mid-March during the spring migration. Salmonellosis produced by the serotype Salmonella enterica subsp. enterica serotype Hessarek (S. Hessarek) was identified as the cause of death in both episodes. Poor body condition, marked splenomegaly, and microscopic disseminated intravascular coagulation with numerous intravascular and tissular bacteria were the most consistent findings. Macro-restriction profiling by pulsed-field gel electrophoresis (PFGE) using XbaI was performed for epidemiologic typing of the S. Hessarek isolates. Two clusters were discernible, that are possibly related, with a similarity of 82.8%. Analysis comparing pectoral muscle and subcutaneous fat scores from the Song Thrushes that died from S. Hessarek with those from healthy Song Thrushes from nearby areas during 2009 and 2010 suggest that poor body condition was associated with the S. Hessarek infection.