Courtesy Arno Wünschmann, DVM, University of
Minnesota Diagnostic Laboratory
These lungs show clear evidence of a raging septicemia.
The next day, you learn that the Salmonella isolate from Melvin (the mouse) is serotype Typhimurium – the same as the Salmonella isolate from Sam. However, you know that Typhimurium is a very common serotype and therefore this is not strong evidence linking the boy’s infection with that of his mouse. The antibiotic resistance pattern can also be used to determine if strains may be related. You note that the antibiotic susceptibility results are the same for both S. Typhimurium isolates. The laboratory results on Melvin the mouse isolate show resistance to ampicillin, chloramphenicol, streptomycin, sulfizoxazole, and tetracycline (R-type ACSSuT). This was the same resistance pattern in the boy’s isolate, and therefore provides some evidence that links the infections in the boy and his pet mouse.
You are also awaiting a call from the laboratory regarding the PFGE results from Sam’s isolate so that you can compare the PFGE pattern to the isolate from Melvin, the mouse. The PFGE “fingerprint” is used to determine if the isolates’ DNA are related.