Typing of Yersinia pestis isolates from the state of Ceara ´, Brazil Y.V.N. Cavalcanti 1 , N.C. Leal 2 and A.M.P. de Almeida 2 1 Universidade Federal Rural de Pernambuco, and 2 Centro de Pesquisas Aggeu Magalha˜es – FIOCRUZ, Recife (PE), Brazil 2002 ⁄ 185: received 13 June 2002, revised 5 September 2002 and accepted 17 October 2002 Y.V.N. CAVALCANTI, N.C. LEAL AND A.M.P. DE ALMEIDA. 2002. Aims: To investigate whether modifications in Yersinia pestis isolates from three plague foci from the state of Ceara ´, Brazil, had occurred over the years as a consequence of genetic adaptation to the environment. Methods and Results: The isolates were studied with respect to susceptibility to antimicrobial drugs, plasmid and protein profiling, pigmentation on Congo red-agar plates, and the presence of some pathogenicity genes using PCR. Most of the expected virulence markers were detected in the cultures examined. There was no evidence of any alteration that could be associated with their origin (patients, rodents and fleas) or period of isolation (1971–1997). Conclusions, Significance and Impact of the Study: Phenotypic or genotypic changes were not detected in the cultures examined. However, the results obtained will serve as a reference to follow the evolution of Y. pestis in these foci. INTRODUCTION Yersinia pestis is the causative agent of plague, which has been responsible for three well-characterized pandemics during the Christian era. In spite of scientific and techno- logical development, plague has never been eradicated and remains widespread around the world (Perry and Fetherston 1997; WHO 2000). Plague arrived in Brazil by sea during the last pandemic which began in the 19th century in China. Although control measures were promptly undertaken, it’s spread inland and establishment among wild rodents in most of the states of the north-east region could not be prevented (WHO 1965). In the State of Ceara ´, plague was first registered in 1900 in Fortaleza, the capital city, from where it spread and became concentrated in three mountain areas: Ibiapaba Mountain, Baturite ´ Mountain and Araripe Plateau. The incidence of human plague and the occurrence of epizootics declined in these areas. However, residual plague activity has been detected consistently among sentinel animals, suggesting that the infection could re-emerge at any moment if surveillance and control activities are neglected (Araga ˜o et al. 2002). The epidemiological characterization of plague areas is highly significant for the development of efficient plague control strategies. Therefore, the typing of Y. pestis strains to determine their sensitivity to antimicrobial drugs, their plasmid content and pathogenic potential is very import- ant. Furthermore, this knowledge would allow the detec- tion of any emerging strains that might be introduced accidentally from another country, or by bioterrorism. The purpose of this work was to perform a phenotypic and molecular characterization of Y. pestis isolates from patients, rodents and fleas from the three plague foci in the State of Ceara ´, to determine whether any modification of the plague bacillus had occurred over the years as a consequence of genetic adaptation to the environment. MATERIALS AND METHODS Bacterial samples and culture conditions The study involved 53 Y. pestis isolates from the State of Ceara ´, originating from different hosts during different periods (Table 1). The isolates were grown in brain heart infusion broth (Difco) at 28°C from 24 to 72 h and plated on blood agar base (Difco). The pigmentation phenotypes of the isolates were determined on Congo red-agar (CRA) as recommended by Bahmanyar and Cavanaugh (1976). Yersinia pestis EV76 (the vaccinal Girard-Robic strain), Correspondence to: Alzira Almeida, CPqAM ⁄ FIOCRUZ ⁄ MS, Campus da UFPE, Cidade Universita´ria, 50670–420 Recife (PE), Brazil (e-mail: aalmeida@cpqam.fiocruz.br). ª 2002 The Society for Applied Microbiology Letters in Applied Microbiology 2002, 35, 543–547