Rapid identification and antibiotic susceptibility testing of Salmonella enterica serovar Typhi isolated from blood: Implications for therapy

The turnaround time (TAT) for Salmonella enterica serovar Typhi identificat ion and reporting of the antibiotic susceptibility profile was determined f or 391 cases of typhoid fever, using the lysis direct plating or lysis cent rifugation method of blood culture along with rapid antimicrobial susceptib ility testing. The TAT was more rapid (TAT for 90% of the patients [TAT(90) ] = 30 h; TAT(100) less than or equal to 67 h) than was possible with conve ntional methodologies and was equivalent to that reported previously using more advanced, costly technologies that are largely unavailable in developi ng countries. Antibiotic susceptibility profiles, determined by the rapid a ntimicrobial susceptibility testing method, of randomly selected 60 S. ente rica serovar Typhi isolates were identical to those determined by overnight conventional testing. Preliminary assessment of the impact of the reduced TAT on physician practices revealed that initial empirical therapy was pres cribed at the time of presentation in most cases (87 of 108 [81%]) despite awareness that the final report would be available on the following day. Pa tients treated empirically with first-line antibiotics and shown subsequent ly to be infected with a multidrug-resistant strain benefited most (8 cases ), since therapy was changed appropriately on the following day. In an addi tional 21 cases, therapy with an appropriate antibiotic was initiated after culture results were available. Thus, in approximately one-fourth (29 of 1 08 [27%]) of the cases, a change in management to an agent active for treat ment of the isolate was made after receipt of the test results. However, in no case was therapy changed from a second-line to a first-line agent, even if the isolate was reported on the day after presentation to be sensitive to first-line therapy (33 cases). Ways in which to utilize rapid-TAT result reporting in order to positively influence physicians' prescribing in Bang ladesh are the subject of ongoing research.