Open Access Research article

Genetic diversity of clinical Pseudomonas aeruginosa isolates in a public hospital in Spain

Margarita Gomila1*, Maria del Carmen Gallegos1, Victoria Fernández-Baca1, Antonio Pareja2, Margalida Pascual3, Paz Díaz-Antolín1, Elena García-Valdés3 and Jorge Lalucat3

Author Affiliations

1 Microbiología, Hospital Son Llàtzer, Palma de Mallorca, Illes Balears 07198, Spain

2 Unidad de Epidemiología y control de infecciones, Hospital Son Llàtzer, Palma de Mallorca, Illes Balears 07198, Spain

3 Microbiología, Departamento de Biología, Universidad de las Islas Baleares, and Instituto Mediterráneo de Estudios Avanzados (CSIC-UIB), Palma de Mallorca, Illes Balears 07122, Spain

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BMC Microbiology 2013, 13:138  doi:10.1186/1471-2180-13-138

Published: 18 June 2013

Abstract

Background

Pseudomonas aeruginosa is an important nosocomial pathogen that exhibits multiple resistances to antibiotics with increasing frequency, making patient treatment more difficult. The aim of the study is to ascertain the population structure of this clinical pathogen in the Hospital Son Llàtzer, Spain.

Results

A significant set (56) of randomly selected clinical P. aeruginosa isolates, including multidrug and non-multidrug resistant isolates, were assigned to sequence types (STs) and compared them with their antibiotic susceptibility profile classified as follows: extensively drug resistant (XDR), multidrug resistant (MDR) and non-multidrug resistant (non-MDR). The genetic diversity was assessed by applying the multilocus sequence typing (MLST) scheme developed by Curran and collaborators, and by the phylogenetic analysis of a concatenated tree. The analysis of seven loci, acsA, aroE, guaA, mutL, nuoD, ppsA and trpE, demonstrated that the prevalent STs were ST-175, ST-235 and ST-253. The majority of the XDR and MDR isolates were included in ST-175 and ST-235. ST-253 is the third in frequency and included non-MDR isolates. The 26 singleton sequence types corresponded mainly to non-MDR isolates. Twenty-two isolates corresponded to new sequence types (not previously defined) of which 12 isolates were non-MDR and 10 isolates were MDR or XDR.

Conclusions

The population structure of clinical P. aeruginosa present in our hospital indicates the coexistence of nonresistant and resistant isolates with the same sequence type. The multiresistant isolates studied are grouped in the prevalent sequence types found in other Spanish hospitals and at the international level, and the susceptible isolates correspond mainly to singleton sequence types.

Keywords:
Pseudomonas aeruginosa; Multilocus sequence typing; Multiresistant; Clinical isolates; Population structure