Evaluation of the in vitro Activity of Two Fourth-Generation Cephalosporins Against Bacterial Samples Isolated From Patients in Several Brazilian Hospitals.

Cefpirome and cefepime are two fourth-generation cephalosporins recently introduced in Brazil. They have a very similar range of in vitro antimicrobial activity, but some differences have been noticed. The goal of this study was to compare the in vitro activity of cefpirome and cefepime against bacterial samples isolated in Brazilian hospitals. We studied 931 samples taken from hospitalized patients between April and June, 1998. The minimum inhibitory concentration (MIC) was determined by the Etest method. The potency of cefpirome was similar to that of cefepime, except against enterococci and coagulase-negative staphylococci, where cefpirome proved 2-fold more potent. The MIC(90) for cefepime were inferior to cefpirome in response to Klebsiella pneumoniae (MIC(90), 24 and 96µg/mL, respectively), Pseudomonas aeruginosa (MIC(90), 48 and 128µg/mL, respectively), and other Gram-negative organisms (MIC(90), 64 and 256µg/mL, respectively). Despite the fact that cefpirome presented a slightly broader range of action against Gram-positive bacteria (90% sensitive vs. 78% sensitive to cefepime), and that cefepime presented an equally broad range against Gram-negative bacteria (74% sensitive vs. 65% sensitive to cefpirome), these differences were not considered clinically significant because the sensitivity differed in MIC by less than 2 dilutions. Only 16 (1.7%) of the 931 samples tested showed a significant difference in sensitivity. This study suggests that, except for Acinetobacter sp. and P. aeruginosa, laboratories may routinely test only cefpirome and apply the same category result to cefepime. Since category discrepancies are very rare and cefpirome is slightly less active than cefepime against Enterobacteriaceae, isolates susceptible to cefepime will certanly also be susceptible to cefpirome. To optimize the treatment of severely infected patients, especially where species such as Acinetobacter sp and P. aeruginosa are involved, we recommend that both cephalosporins be tested by using the same susceptibility test method to determine the MIC.

Microbial Pathogens Associated With Cystic Fibrosis: Special Focus on Pseudomonas aeruginosa.

Cystic fibrosis (CF) is the most common inherited lethal disease among Caucasians. The disease is characterized by a high sodium sweat concentration, malabsorption, malnutrition, and chronic bronchopulmonary infection. Although CF is a multisystem disorder it is the deterioration of lung function, due mainly to bacterial colonization, that is the major determinant contributing to the high morbidity and mortality of affected patients. A relatively large variety of microbial species can be recovered from the CF sputum but it is widely accepted that Staphylococcus aureus, Haemophilus influenzae, Pseudomonas aeruginosa, and Burkholderia cepacia are the most important organisms causing infection in CF patients. Among these, P.aruginosa is the most prevalent pathogen responsible for much of the severe chronic lung infection. Antibiotic therapy aimed at clearing or reducing, the bacterial load in the CF lung, even though temporary, increases the longevity of patients and is one of the mainstays in treatment the disease.