In this study we describe the profile of antimicrobial susceptibility of S. aureus strains isolated from cutaneous lesions in a pediatric tertiary care center in Italy. To our knowledge, no other Italian data on this topic are available.
The first observation we can drive is that even if the prevalence of MRSA we observed was lower than in other pediatric studies from other countries3,4,5, the proportion this pathogen on skin lesions was significantly higher in outpatients compared with inpatients. However, since 95%CI of the proportions are imbricated it is probable that this difference is not clinically relevant but represents only a statistical effect.6
Since no other pediatric Italian data are available we can not make any national comparison, but it must be noted that European data (including also adults) report a MRSA prevalence of 15.1%, with a North (0%) to South (29%) increasing gradient7, that is consistent with our observations.
A recent Italian consensus on the treatment of skin infections in pediatrics8 indicated clindamycin for first line treatment in communities where proportions of MRSA is > 10% if clindamycin resistance is < 10%. Considering our epidemiology clindamycin (11% in out- and 14% in inpatients resistant strains) did not meet these criteria and could not represent a possible choice for empirical therapy before susceptibility tests availability. We do not know if this observation can be generalized to other Italian regions, but this observation should represent a warning. In spite of the significantly higher proportion of strains resistant to cotrimoxazole in outpatients (8% vs. 4.1%), as already described9, in our study resistance to cotrimoxazole was lower than the 10% threshold proposed for other drugs to be used for first line therapy of skin lesions8 and therefore it could represent an acceptable first choice, pending susceptibility tests. The generally lower proportion of resistant strains in inpatients could seem a paradox. However, IGG has a strict policy of antibiotics use and effective patients’ isolation procedure in presence of resistant strains10 that could at least partially explain this observation.
The use of topical antibiotics has been associated with selection of resistant strains.11 In our study data on resistance to mupirocin could be poorly reliable because of the high proportion (70%) of untested strains; Fusidic acid showed a very low proportion of resistance (about 3% of resistance) but also in this case near 1/3 of strains were not tested. Finally, topical gentamycin is a highly used over the counter topical antibiotic in Italy, and indeed the resistance is not negligible (9–12%). Our data suggest that fusidic acid is the better topical choice8, at least in our epidemiological condition.
The main limitation of this study is the lack of clinical data, due to fact that it is derived from a laboratory database. Despite this, it gives information about an important item such as antimicrobial resistance in pediatric staphylococcal skin infections in a geographic area and clinical field where epidemiological data are lacking.