Abstract
BackgroundThere have been no systematic studies of microbiological differences before and after antibiotics treatment. The aim of this study was to evaluate the effect of prior receipt of antibiotics on the microorganism distribution.MethodsA retrospective, observational cohort study was conducted in a 3200-bed tertiary, referral, teaching hospital in eastern China. During a 2-year period, all hospitalized patients treated with antimicrobial agents were enrolled in this study. Among 48,692 patients evaluated, the 27,792 (57.1%) who were sampled within 2 days before or after administration of the first dose of antimicrobial agents were included. Distribution of clinical specimens and the microorganism were compared between before and after antibiotic drug treatment groups.ResultsCompared to specimens taken after antibiotics exposure, specimens taken before antibiotics exposure had a higher proportion of blood and urine specimens and a higher culture positive rate (all P < 0.001). Higher percentages of Staphylococcus aureus (9.9% vs. 8.5%, P = 0.041), non-fermenting bacteria (27.7% vs. 19.9%, P < 0.001), and fungi (8.4% vs. 4.0%, P < 0.001) were isolated from the group after antibiotics exposure, while the percentages of Streptococcus spp. (4.8% vs. 2.7%, P < 0.001), Haemophilus influenzae (2.3% vs. 0.8%, P < 0.001), and Moraxella catarrhalis (0.7% vs. 0.1%, P < 0.001) were higher in the group before antibiotics exposure. Further analysis found significant differences of microbes derived from respiratory secretions, blood or urine samples. We found, after antibiotics exposure, the separation rate of non-fermenting bacteria was significantly increased (all P < 0.05), and the separation rate of Candida spp. was higher, with statistical significance in airway secretion and urine samples (both P < 0.05), but the separation rate of Staphylococcus aureus among the three groups was not affected by antibiotics. In addition, the isolation rate of Streptococcus spp. in blood and urine samples decreased significantly (both P < 0.05) after antibiotics exposure. Interestingly, no statistical difference was found for microbes isolated from body fluid specimens between the two groups.ConclusionsThe outcome revealed that antibiotic-insensitive organisms such as non-fermentative bacteria and fungi were more frequently isolated after antibiotics exposure. However, this trend might be specimen dependent and was not obvious in body fluid specimens.
Highlights
There have been no systematic studies of microbiological differences before and after antibiotics treatment
Studies conducted by Montravers et al [10] and Harbarth et al [11] showed that starting antibiotic therapy before sample collection may result in detecting less-sensitive microorganisms
19,868 (71.5%) of patient samples were taken before antibiotic therapy (SBA group), and 7924 (28.5%) of patient samples were taken after antibiotic therapy (SAA group)
Summary
There have been no systematic studies of microbiological differences before and after antibiotics treatment. Studies conducted by Montravers et al [10] and Harbarth et al [11] showed that starting antibiotic therapy before sample collection may result in detecting less-sensitive microorganisms. The former only included 76 consecutive patients with ventilator-associated pneumonia [10], and the latter [11] mainly evaluated gram-negative pathogens. A systematic study of the microbiological differences isolated from samples taken before and after the initiation of antibiotic therapy, which to the best of our knowledge is lacking in the literature, is necessary
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