My daughter is 7 months and has cultured this twice without us ever knowing, i didnt even know about this until i called. also she has cultured staf once or twice too, i dont even know what signs would be to look for but its werid cause one time she'll have it and than the next it will be gone, they said what causes it though is that when she is sick and coughs mucus up and than it doesnt come out it just slides back down her throat which causes this bacteria to grow so when she is sick we pump her with medicine and do tobi just incase always we dont even chance it. and sometimes if we know mucus is coming we suck it out with a bulb thing. good luck!