To the editor: Gender differences in the acquisition of P. aeruginosa

We read with interest the article by Maselli et al. about the risk factors for initial acquisition of P. aeruginosa (PA) in children with cystic fibrosis identified by newborn screening. The authors conclude that female gender is an important risk factor for early PA detection in children with cystic fibrosis (CF). The article offers itself to some remarks. The term ‘‘P. aeruginosa acquisition,’’ although used in other experiences, does not seem sufficiently clear if used for a cohort of CF patients diagnosed by screening, and followed with regular microbiological monitoring. A careful microbiological monitoring following diagnosis by screening offers the opportunity of evaluating with more precision themoment of the first PA colonization and allows for early eradication treatment. Considering the risk thatCFpatients have of acquiringPA, the authors refer to the moment of detection of the pathogen, but no indications are given with regard to the difference between first contact with PA (or first colonization) and chronic infection. This distinction is clinically relevant, particularly in consideration of the influence that adequate therapy may have on preventing PA infection from becoming chronic, with subsequent influence on the patient’s health status. The patients participating in the study of Maselli et al. were monitored from amicrobiological point of view only once a year after the first year of life. This period of time seems too long to allow for a prompt eradicating therapy. The study does not mention the phenotype of the pathogen, and does not refer to testing for anti-PA antibodies, which in CF patients diagnosed by screening represents a useful integration in order to define the relation between the pathogen and the host. Moreover, the data that result from our CF screening program seem to suggest that the role of gender in determining the acquisition of PA might be not so important. We evaluated an entire population of CF patients diagnosed by screening in Tuscany, Italy, from January 1, 1984, to December 31, 2001. In this period, 75 CF patients were diagnosed by screening, taken in charge within the thirdmonth of life, and followedwith no interruption, with regular visits at the Outpatient Clinic of the Regional CF Center of Tuscany, Italy. In our Center, airways cultures are usually performed every 3 months. Among the patients, 47 were male (mean age at end of period, 84 months; SD, 58.3; range, 2–211) and 28 were female (mean age at end of period, 98.4 months; SD, 58.8; range, 12–214). In each group, we examined the incidence of airways cultures positive for PA in the period (calculated as number of positive cultures/months free from infection patient 100), the prevalence of chronic PA infections, mean age at moment of first airways culture positive for PA, andmean age atmomentPA infectionbecamechronic. There was no difference among the two groups regarding incidence of airway cultures positive for PA in the period (2.6% in females, and 2.66% in males). Also, the prevalence of chronic PA infection was similar: 17.8% among females (n1⁄4 5), and 19.1% (n1⁄4 9) among males. As far asmeanage atmoment offirst PA-positive culture is concerned, it was higher among females (39.4 months; SD, 38.2; range, 2–137) than among males (27.5 months; SD, 37.6; range, 2–174), but not in a statistically significant way (P> 0.05). We found a statistically significant difference with regard to mean age at chronic PA colonization, which was higher in females (127.6 months; SD, 55.1; range, 53– 206) than in males (32.8 months; SD, 15.4; range, 8–56; P1⁄4 0.004), but this finding could be the result of the eradicating treatment performed at first PA colonization that we have long used in our Center. Our data show that in an entire population ofCFpatients diagnosed by screening over an 18-year period, there are no significant differences in acquisition of PA between the two genders. The only difference we found seems to suggest that in females, chronic infection by PA is delayed with respect to males, although this may be considered a result of treatment. Therefore, our data suggest that the conclusions of Maselli et al. should be considered with caution.