Postmortem Postscript: Staphylococcal Pneumonia
Not two weeks after this womanss death, the lead article in Obstetrics and Gynecology addressed the increasing prevalence of Staphylococcal infections in pregnant women (Chen, KT, et al. Obstet Gynecol 2006;108:482-87), and was accompanied by a commentary on "Emerging Infections" (Obstet Gynecol 2006;108:480-81) by the journal editor, Dr. Ronald S. Gibbs, an internationally recognized expert in OB/GYN infectious diseases. The article by Chen and colleagues reported finding Staphylococcus aureus in 17.1% (507 of 2,963) rectovaginal cultures obtained for routine Group B Streptococcus (GBS) screening during pregnancy at 35-37 weeks. GBS screening has become a 'standard of care' in obstetrics because of the success of prophylactic maternal therapy in labor for known GBS carriers in reducing the risk of neonatal sepsis. Of the S aureus isolates, 14 (2.8%) were found to be methicillin-resistant, and 13 of these were considered to be "community-associated" by genetic characterization. Interestingly, there was also found to be an association between GBS-positivity and S aureus colonization.
S aureus is a very common and very adaptable organism. Many individuals carry it and are asymptomatic, and many others know it best for the more superficial skin and soft tissue infections with which it is often associated, and some individuals chronically plagued. However, the organism can cause serious, life-threatening problems, including bacteremia, endocarditis, necrotizing fasciitis, pneumonia, and 'toxic shock syndrome.' Like many other bacteria, S aureus has been quite successful in evolving strains that are resistant to the antibiotics commonly used to treat it. Traditionally, we think of MRSA as being confined to settings like hospitals where serious infectious diseases are concentrated, patients are more likely to be ill and immunocompromised, broad spectrum antibiotics are often used, and transmission can be readily perpetuated by contact between patients and hospital personnel. Indeed, it has been estimated that about 60% of Staph infections in hospital intensive care units are now MRSA. Unfortunately, it is also becoming increasingly apparent that MRSA is quickly moving into the community.
Community-acquired MRSA may rapidly become a problem once it is established because of the potential to be readily spread among family members where "good hand washing techniques" promoted within hospitals are unlikely to play a role to curb the spread. Patients who develop infectious complications related to Staph also often have multiple body sites affected. In a study of community-associated MRSA infections in pregnant women at one hospital, Laibl and colleagues (Obstet Gynecol 2005;106:461-5) reported patients with multiple sites of infection, including the buttocks, vulva, or groin (67%), extremities (44%), and breast (23%).
As Dr. Gibbs has cited in his editorial, MRSA strains have been implicated in "skin infections in otherwise healthy newborns and... sepsis in infants in neonatal intensive care units." It can cause mastitis and breast abscesses and can be transmitted to infants by breast milk. It can cause wound infections and infections at IV access sites. With the growing epidemic of obesity and diabetes in pregnancy (both of which probably increase risk for persistent colonization and risk of complications with S aureus), the persistently (and, abhorrently) high rates of cigarette smoking (ditto on the colonization and complications comment) among pregnant women, and the rising cesarean section rates, MRSA may well become a more serious factor in maternal and neonatal morbidity in the future.
In closing, I would have one other comment. We are moving into the flu season. Influenza carries its own higher morbidity for pregnant women; however, the virus has also been known to provide fertile ground for secondary infections by bacteria such as S aureus. Indeed, in the great flu epidemic of 1918, where 10's of millions died worldwide, superimposed Staph pneumonia is now thought to have played a significant role. If our obstetrical patients are now more likely to be colonized by MRSA, we may well need to be thinking of having a much lower threshold for rapid, early diagnosis of superimposed bacterial pneumonias, even in patients suspected of just having "the flu," so that appropriate antibiotic therapy might be employed in a timely fashion under circumstances where antibiotics are not ordinarily recommended.