Yes calamansi is antibacterial and has shown to be very effective at preventing things such as and protecting you against S. aureus, P. aeruginosa, and C. albicans.
The acid which is present in calamansi is citric acid.
The citric acid contained in calamansi is healthy for you and it also contains many Vitamins including Vitamin C which can help prevent the flu and boost your immune system.
The entire calamansi fruit contains a small level of carbohydrates (3%), minerals (1%), ascorbic acid (0.1%), and citric acid (3%).
The peel of calamansi is also rich in essential oils and ascorbic acid (0.15%).
The juice of calamansi is very acidic and contains 5.5% citric acid.
So while the calamansi is healthy you should still watch how much you eat of the calamansi if you have digestive issues or acid issues with your stomach such as acid reflux.