[1] Univ Coimbra, Fac Med, Inst Physiol, Coimbra, Portugal
[2] Univ Coimbra, Fac Med, Inst Microbiol, Coimbra, Portugal
[3] Med Univ Sofia, Dept Microbiol, Sofia, Bulgaria
[4] Univ Coimbra, Fac Med, Inst Pathol, Coimbra, Portugal
[5] Univ Aveiro, Dept Educ Sci, P-3800 Aveiro, Portugal