Antibiotics won't affect your weight one way or the other .. although they may cause some diarrhea, which would mean you could become dehydrated a bit ... so a good idea to keep the water intake up.

However ... an infection itself WILL screw up your metabolism. The bacteria (and viruses too) cause the blood sugar to be elevated and consequently insulin levels will be higher too. If you were eating a regular high-carb diet, you'd likely gain weight ... FAT weight, due to the insulin. But with low-carbing, you can prevent this by keeping a close eye on carbs, and keeping the blood sugar stable. It's worth noting that bacteria THRIVE on sugar, so there's further incentive to stick closely to your LC plan.

The acidophilus is a good idea Try to take on an empty stomach, and at bedtime.

Hope you're feeling better soon

Doreen