This study evaluated the relationship between previous colonization of the oropharynx and development of ventilator-associated pneumonia through the classification of genomic fingerprint pattern by pulsed-field gel electrophoresis of both oxacillin-resistant and oxacillin-susceptible Staphylococcus aureus isolates obtained from hospitalized patients in an intensive care unit.

INTRODUCTION : Antimicrobial resistance is an increasing threat in hospitalized patients, and inappropriate empirical antimicrobial therapy is known to adversely affect outcomes in ventilator-associated pneumonia (VAP). The aim of this study was to evaluate antimicrobial usage, incidence, etiology, and antimicrobial resistance trends for prominent nosocomial pathogens causing ventilator-associated pneumonia in a clinical-surgical intensive care unit (ICU). METHODS : Gram-negative bacilli and Staphylococcus aureus causing VAP, as well as their antimicrobial resistance patterns and data on consumption (defined daily dose [DDD] per 1,000 patient days) of glycopeptides, extended-spectrum cephalosporins, and carbapenems in the unit were evaluated in two different periods (A and B). RESULTS: Antimicrobial use was high, mainly of broad-spectrum cephalosporins, with a significant increase in the consumption of glycopeptides (p < 0.0001) and carbapenems (p < 0.007) in period B. For Acinetobacter baumannii and members of the Enterobacteriaceae family, 5.27- and 3.06-fold increases in VAPs, respectively, were noted, and a significant increase in resistance rates was found for imipenem-resistant A. baumannii (p = 0.003) and third-generation cephalosporins-resistant Enterobacteriaceae (p = 0.01) isolates in this same period. CONCLUSIONS: Our results suggest that there is a link between antibiotics usage at institutional levels and resistant bacteria. The use of carbapenems was related to the high rate of resistance in A. baumannii and therefore a high consumption of imipenem/meropenem could play a major role in selective pressure exerted by antibiotics in A. baumannii strains.

INTRODUÇÃO: Este estudo avaliou o consumo das principais classes de antibióticos, a colonização de orofaringe de pacientes sob ventilação mecânica e o risco de pneumonia associada à ventilação (PAV) causada por Staphylococcus aureus em uma unidade de terapia intensiva (UTI) de adultos. MÉTODOS: Foi realizado um estudo caso-controle, sendo caso os pacientes colonizados pelo oxacillin-resistant Staphylococcus aureus (ORSA), e controle aqueles pelo oxacillin-sensitive Staphylococcus aureus (OSSA), no período de maio de 2009 a agosto de 2010. A ocorrência de PAVs por S. aureus também foi avaliada no mesmo período. O consumo de antibióticos foi expresso pelo número de doses diárias definidas (DDDs)/1.000 pacientes-dia para glicopeptídeos, carbapenêmicos e cefalosporinas de amplo espectro. RESULTADOS: Trezentos e quarenta e seis (56,1%) dos pacientes foram submetidos à ventilação mecânica com uma frequência de colonização de orofaringe de 36,4%, correspondendo a 63,5% e 36,5% de ORSA e OSSA, respectivamente. O risco de adoecimento por este microrganismo foi significativo (p<0,05), considerando se a colonização/infecção foi por ORSA ou OSSA. O consumo de antibióticos foi alto, principalmente para cefalosporinas de amplo espectro (551,26 DDDs/1.000 pacientes-dia). A elevada densidade de uso de glicopetídeos (269,56 DDDs/1.000) foi relacionada com a colonização pelo ORSA (Pearson r=0.57/p=0.02). Adicionalmente, idade > 60 anos, terapia antibiótica prévia e uso prévio de carbapenêmicos foram estatisticamente significantes por análise multivariada. CONCLUSÕES: Foi observada uma relação significativa entre a colonização da mucosa de orofaringe e o risco de PAV por ambos fenótipos. O uso de glicopeptídos foi relacionado com a colonização pelo ORSA.

INTRODUCTION: his study evaluated the consumption of major classes of antibiotics, the colonization of the oropharynx of patients on mechanical ventilation, and the risk of ventilator-associated pneumonia (VAP) caused by Staphylococcus aureus in an intensive care unit for adults. METHODS: A case-control study was carried out using colonized patients (cases) by oxacillin-resistant S. aureus (ORSA) and (controls) oxacillin-sensitive S. aureus (OSSA) from May 2009 to August 2010. The occurrence of VAP by S. aureus was also evaluated in the same period. Antibiotic consumption was expressed as the number of defined daily doses (DDD)/1,000 patient-days for glycopeptides, carbapenems, and extended-spectrum cephalosporins. RESULTS: Three hundred forty-six (56.1%) patients underwent mechanical ventilation with a frequency of oropharyngeal colonization of 36.4%, corresponding to 63.5% for ORSA and 36.5% for OSSA. The risk of illness for this organism was significant (p<0.05), regardless of whether colonization/infection was by ORSA or OSSA. The consumption of antibiotics was high, mainly for broad-spectrum cephalosporins (551.26 DDDs/1,000 patient-days). The high density of use of glycopeptides (269.56 DDDs/1,000 patient-days) was related to colonization by ORSA (Pearson r=0.57/p=0.02). Additionally, age >60 years, previous antibiotic therapy, and previous use of carbapenems were statistically significant by multivariate analysis. CONCLUSIONS: There was a significant relationship between the colonization of the oropharyngeal mucosa and the risk of VAP by both phenotypes. The use of glycopeptides was related to colonization by ORSA.