During her quarantine Mary Mallon secretly had her feces tes

During her quarantine, Mary Mallon secretly had her feces tested by an independent laboratory. The lab did not detect any Salmonella. How would you explain this finding biologically

Solution

Mary Mallon was an intermittent carrier of typhoid. In intermittent or asymptomatic carriers, the organism may lie dormant for long periods and reproduce during certain periods. So, the specimens of the carriers need not necessarily give positive results for the test organism. As Mary Mallon is an intermittent carrier, her species specimens could be positive sometimes and negative sometimes.