This is an area where research is ongoing, but here are some of the possible reasons.
1 They have been reinfected through another hospital contact and a cycle of sickness has started again
2 The drugs previously given subdued it but did not kill it. There is some evidence that some bacteria will ‘switch off’ and go dormant in their fight against vancocin. When the balance of the intestine is disturbed again by drug treatment for another illness the latent c diff is re-activated.
3 Little is known about the general prevelance of c difficile in the environment and community. Figures of 3-35% who might be ‘silent carriers’ are sometimes mentioned in the scientific literature. There is also a growing body of evidence that some are suffering c difficile infections without hospital contact. The possibility of community spread cannot be ruled out.
4 The intestine can sometimes be so disturbed by drug treatment, infection and illness that it struggles to get right. The controversial fecal transplant method does suggest that healthier fecal matter can restore the intestine to balance and break the cycle of illness
Understanding Your C Difficile Infection
How does C Diff actually make you ill
Why do some people have recurring C Diff infection
How can C diff infection be prevented
What is the C Diff ‘fecal transplant’ therapy
Is C Difficile contagious?
What is C Difficile colitis
What are C Difficile toxins