Comparative evaluation of BacT/ALERT 3D and BACTEC systems for the recovery of pathogens causing bloodstream infections

To compare BacT/ALERT [BTA] and BACTEC 9240 [BAC], two continuously monitoring automated blood culture systems, for the recovery of bloodstream pathogens and standard media available for these systems. Blood samples from 100 adults and 50 paediatric patients suspected of having bloodstream infections were inoculated at the bedside into non-vented BTA and BAC standard blood culture bottles and incubated in their respective instruments. The time to growth detection [TD] was recorded for each bottle that became positive. A quantitative assay was also carried out with 5 standard bloodstream pathogens to assess TD of each pathogen as well as the quantity of organisms recovered. A total of 23 isolates representing true infections were recovered by both BTA and BAC bottles, indicating ablood culture positivity rate of 15.3%, 18 [78.3%] by BTA bottles and 13 [56.5%] by BAC. Proteus mirabilis, Pseudomonas aeruginosa and Clostridium perfringens were recovered only by the BTA system. The average TDs were 19.0 and 24.6 h for BTA and BAC, respectively. Analysis of the quantitative growth of known pathogens in both systems was more or less the same for Staphylococcus aureus, Escherichia coli and P. aeruginosa but slightly different for Haemophilus influenzae and Streptococcus pneumoniae. The anaerobic bottle ofthe BTA did not support the growth of H. influenzae below an inoculum of 10[10] CFU/ml whereas the BAC did so at a lower inoculum of 10[8] CFU/ml. TD for S. pneumoniae in the BTA was about half of that in the BAC. The BTA system appears to be more efficient in detecting common bloodstream pathogens asa higher inoculum is needed for the BAC system to detect the same organism

Prevalence of extended -spectrum beta -lactamases in enterobacteriaceae, Pseudomonas and stenotrophomonas as determined by VITEK2 and Etest syptems in Kuwait teaching hospital

To determine the prevalence of extended-spectrum beta-lactamase [ESBL]-producing members of the Enterobacteriaceae using VITEK 2 and E test systems. A total of 3,592 consecutive gram-negative isolates [single isolate per patient] of the family of Enterobacteriaceae and Pseudomonas adjudged to be clinically relevant to the patient's infection were studied for ESBL production over a period of 1 year at Mubarak Al-Kabeer Hospital, Kuwait. Two methods were used: the automated VITEK 2 system and E test ESBL, a manually manipulated plastic strip containing various gradients of beta-lactam antibiotics. These tests and interpretative criteria for the results were performed according to the manufacturer's instructions. Of the 3,592 bacterial isolates, 264 [7.5%] and 185 [5.2%] were positive for ESBL production by the VITEK 2 and E test, respectively. All the ESBL-producing Pseudomonas aeruginosa identified by VITEK 2 gave indeterminate results by E test. Prevalent ESBL producers, identified by the VITEK 2 versus E test, respectively, were: Citrobacter spp. [15 vs. 3.2%], K. pneumoniae [12.2 vs. 11.4%], Enterobacter spp. [12 vs. 3%], E. coli [6.5 vs. 5.6%], P. aeruginosa [6.5 vs. 0%] and Morganella spp. [2 vs. 1%]. The most common infection associated with ESBL-producing pathogens was urinary tract infection [68.2%], followed by wound infection [14.4%] and bloodstream infection [6.1%]. The result of this study showed a relatively high prevalence of clinically significant ESBL producers among the Enterobacteriaceae and Pseudomonas spp. at our teaching hospital. The VITEK 2 identified a higher prevalence of ESBL strains than the E test