Prostate Cancer PSA

So my father had his PSA come back around 8.8 last week, which was high for him but not concerning since he's had prostate infections before and after taking antibiotics the issue was always resolved. After a week and a half of antibiotics he did another test and this time his PSA was 19. Can a PSA increase that much that fast? We couldn't believe it was so high so he just retested and it's 19 again.
I've read articles where people experience a 2-3 point increase in a couple of months but not 10 points in a week or so. I should add he had a biopsy done 3 years ago that came back clear.