what causes infections in the incision marks after Breast Augmentation?

Bacteria, most commonly from the patient's skin, is the usual cause of wound infections.It is, however, an uncommon issue when good sterile technique is followed.  In our practice, we track the percentage of infection issues after breast implant surgery:  it's less than one-half of one percent, which is very low.You can help to avoid infection issues by using antibacterial soap, wiping the breasts with 2% chlorhexidine wipes prior to surgery, taking your antibiotics as prescribed, and reporting any fever or redness near the incisions to your surgical team.  If you have had skin infections in the past, or live with anyone who currently (or recently) has a skin infection, report this to your surgeon prior to your procedure.

Infections after breast augmentation are caused by the same sorts of bacterial contamination that we see with almost any type of post-operative infection. If an infection is serious enough to cause the skin edges at the incision closure to dehisce or open up, then the scar quality for that incision may be worse in comparison to an incision that did not get infected. It is worthwhile to inquire about your surgeon's infection rate with breast augmentation prior to deciding upon where you will have your operation done, and most surgeons are proud to offer you a preoperative tour of their O.R. facilities if you express an interest. After surgery, it is important to follow your doctor's instructions for cleaning/showering these areas, as well as any post-op antibiotic regimen or dressing change/application specified. The good news is that infection of the incisions from a breast augmentation are a relatively rare occurrence (they just seem to be more common on forums like these because these are the places that people come for advice on problems when they arise). 

are extremely rare and I have never seen one myself in my own practice.  But it can happen and you must be willing to accept that risk in order to have your procedure.