When should mastitis be treated with antibiotics?

pillsMastitis – inflammation of the breast tissue – is a common problem for breastfeeding women. Although it can be associated with bacterial infection, this is rarely its primary cause (see milk stasis – not infection – is the main cause of mastitis). Many doctors nevertheless choose to treat it with antibiotics, ‘just in case’ infection is present. Given the uncertain relationship between bacteria and mastitis, what are the benefits – and drawbacks – of taking antibiotic medication?

There are disappointingly few properly controlled studies looking at the antibiotic treatment of mastitis. A recent Cochrane Review analyzing all the research in this area found only two studies that were sufficiently well designed or reported to provide unbiased evidence1. One study looked at the effects of two different types of antibiotic (Amoxicillin and Cephradine), and found that they were equally good at relieving symptoms. Unfortunately, as the study didn’t have a control group of women who did not take any medication, it is not clear whether the antibiotics actually helped them recover, or whether the mothers would simply have recovered over time anyway.

In the second study, mothers who had ‘infectious mastitis’ (diagnosed when both bacteria and white blood cell counts were higher than normal) were assigned to three groups. In the first group, the women were advised to treat the mastitis by emptying the affected breast every six hours (feeding their baby as normal and then expressing any remaining milk); in the second, mothers were asked to follow the same breast emptying routine, and were also prescribed a course of antibiotics (Penicillin, Ampicillin or Erythromycin); in a third control group no treatment was recommended. The results showed that antibiotics did indeed have a beneficial effect: whilst women in the breast-emptying group recovered more quickly than those who weren’t treated, those taking the medication recovered fastest of all.

This single study does appear to show that antibiotics can help treat mastitis associated with bacterial infection. Does this provide adequate evidence for treating all cases of mastitis in this way? Well, not really, for a number of reasons.

Firstly, the antibiotics were shown to be effective when infection was present. In many cases of mastitis, infection is not present, so antibiotics wouldn’t be any use. A risk of prescribing antibiotics without diagnosing infection is that it may not treat the root of the problem. As mastitis is more commonly caused by milk stasis than infection, it is vital to tackle this issue to ensure proper recovery and avoid reoccurrence.

Inappropriate antibiotic treatment is also problematic as it increases the chance that the bacteria may become resistant to the drug. Staphylococcus aureus is the bacteria most commonly associated with mastitis, and a well-known strain of this – MRSA – is already resistant to antibiotics, so this is potentially a serious problem2.

There is also the possibility that antibiotics taken by breastfeeding mothers may have adverse effects on their babies. Exposure to antibiotics through breast milk has been linked with problems such as minor infant breathing difficulties3 and diarrhoea4. Although such complications are not regarded as serious enough stop women from taking medication when they need it (particularly if it enables them to continue breastfeeding), it seems sensible to avoid putting babies at any unnecessary risk, particularly given that this area is currently under-researched1.

So, what does all this mean for mothers who have mastitis, and health professionals who are trying to treat it? There is some evidence that antibiotics help treat mastitis when infection, diagnosed using both bacteria and white blood cell counts, is known to exist. Ideally, antibiotics would be prescribed only in this situation, as using them unnecessarily increases the chance bacteria will develop resistance to them – leading to strains such as MRSA – and may expose babies to unnecessary health problems. Diagnosing infection is notoriously difficult, however, as the bacteria which potentially cause infection can be present even when infection itself isn’t5, and measuring both white blood cell and bacteria counts is rarely going to be practical in a normal health care setting, such as a GP surgery. In a paper published last year discussing this difficult issue, Linda Kvist and colleagues recommend a daily follow-up of mothers with mastitis, and the prescription of antibiotics when symptoms are persistent. In the meantime (and indeed, in the first instance) treating milk stasis, the primary cause of mastitis, remains the top priority.

  1. Cochrane Database Syst Rev. 2009 Jan 21;(1):CD005458
  2. Int Breastfeed J. 2008 Apr 7;3:6.
  3. Pediatrics. 2007 Jan;119(1):e225-31
  4. Am J Obstet Gynecol. 1993 May;168(5):1393-9.
  5. Mastitis: causes and management. World Health Organization; 2000.

Milk stasis – not infection – is the main cause of mastitis

holding_babyPrior to my brush with it, I thought that mastitis was caused by a bacterial infection. This is not completely unreasonable, given that this is precisely how numerous ‘health’ websites define it (FreeMD, eMedicineHealth, HealthSquare to name just a few). When you consider that the symptoms of mastitis can include a fever as well as redness, lumps and pain in the breasts, and treatment can involve antibiotics, the definition seems to make sense.

Unfortunately, it turns out to be somewhat misleading. Whilst bacterial infection may play a part in mastitis, it is in fact inflammation of the breast tissue that is at the root of the condition, and causes the majority of the symptoms. The World Health Organization describes mastitis as ‘an inflammatory condition of the breast, which may or may not be associated with infection’1. They summarize the uncertain relationship between bacterial infection and mastitis as follows:

Many lactating women who have potentially pathogenic bacteria on their skin or in their milk do not develop mastitis.
Many women who do develop mastitis do not have pathogenic organisms in their milk.

This basically means that you can be carrying the bacteria associated with mastitis – and even have it in your milk – without developing the condition, and conversely, you can succumb to mastitis when there is no evidence you’re carrying the bacteria.

So, if mastitis isn’t due to an infection, what does cause it? It appears that the inflammation that characterizes mastitis is a consequence of ‘milk stasis’: milk is produced, but then remains in the breast, rather than coming out during feeding. Milk stasis can occur for many reasons, including blockages in the ducts, a decrease in feeding frequency and poor attachment1,4. It’s also possible that stress might play a role, by both increasing milk production and delaying the letdown reflex2. Why milk stasis goes on to cause inflammation isn’t so clear, though it could result from inflammatory substances found in milk irritating the breast tissue, or an immune reaction to certain milk proteins3.

Although bacterial infection is not often the primary cause of mastitis, it is sometimes thought to exacerbate the symptoms3. Determining the precise role it plays, however, is a tricky business. Firstly, it is very hard to ensure that milk cultures are sterile, so it isn’t always possible to know that the bacteria found in a woman’s milk haven’t in fact come from her skin when the sample was taken1. Secondly, as stated above, harmful bacteria can be found in the milk of women who don’t have mastitis, indicating that there is not a simple cause and effect relationship between the two. One possibility is that mild changes initiated by milk stasis may be exacerbated by bacterial activity: symptoms could be considered to be on a scale, from a reduction in milk output but no pain (known as subclinical mastitis), to breast abscess and severe pain, with increasing amounts of bacterial involvement as you move from one end to the other3.

What does all this mean if you find yourself suffering from mastitis? Perhaps the most important thing to remember is that the symptoms are probably due to a milk flow problem, so your top priority should be to address any causes of this. This might include making sure your baby is properly latched on, feeding more frequently and emptying the breast properly at each feed. Many doctors also choose to treat mastitis with antibiotics, although there is a lack of consensus as to which ones to use, and even whether it’s appropriate to use them at all (see when should mastitis be treated with antibiotics?). Whether or not you take medication, the most important thing is to keep the milk moving. Whilst feeding with mastitis doesn’t appear to pose a risk to you or your baby, stopping could well do: not only will it make the symptoms worse, but it will almost certainly jeopardize your milk supply5. Mastitis is a common reason for giving up breastfeeding, but it needn’t be – focus on sorting out your feeding technique and you should hopefully make a rapid recovery.

  1. Mastitis: causes and management. World Health Organization; 2000.
  2. Mediators Inflamm. 2008;2008:298760.
  3. Arch Dis Child. 2003 Sep;88(9):818-21
  4. Cochrane Database Syst Rev. 2009 Jan 21;(1):CD005458.
  5. Am Fam Physician. 2008 Sep 15;78(6):727-31.