Infections caused by Pseudomonas aeruginosa: relatively frequent isolation of serogroup 12 from clinical specimens.

Serological typing of P. aeruginosa is the most simple and reliable procedure recommended for "in-house" investigations and for studies of suspected outbreaks of infection by this microorganism. It is also a useful procedure in order to know serotype prevalence in a definite geographical area and to obtain indications about the more appropriate composition of polyvalent anti-Pseudomonas vaccines. In the present report, we describe the relatively high frequency of isolation of serogroup 12 from patients in Palermo, Italy. Serogroup 12 is very rare in north-Europe and in the USA, and, as a consequence, it is not included in some vaccine preparations. In Palermo, strains belonging to this serogroup, resistant to a large number of antibiotics, were on the contrary isolated, during more than six years, in different hospitals and from three out-patients. In a Burns Unit, they were in particular responsible for extensive and life-threatening outbreaks.