Detection of a microbial biofilm in intraamniotic infection.

Microbial invasion of the amniotic cavity has been detected in the mid-trimester of pregnancy in apparently healthy women,1–5 and in the amniotic fluid of women with cervical insufficiency,6;7 preterm labor with intact membranes, preterm prelabor rupture of membranes, idiopathic vaginal bleeding,8 preterm rupture of membranes at term,9;10 spontaneous labor at term with intact membranes11 and clinical chorioamnionitis. Intra-amniotic infection is a common mechanism of disease in obstetrics and bacteria can attack the fetus and cause systemic inflammation (a fetal inflammatory response syndrome12;13) and multiple organ damage.14 The microbiologic diagnosis of infection has been based upon the use of cultivation techniques in which bacteria are recovered from amniotic fluid. Growth of microorganisms in the laboratory depends on the provision of suitable nutritive and environmental conditions. This practice was developed after the seminal observations of Robert Koch, who established the time-honored isolation and pure culture techniques. However, there are two major limitations of cultivation-based techniques. First, approximately 99% of bacteria in aquatic and soil ecosystems resist cultivation (a phenomenon called “the great plate count anomaly”15); second, bacteria grow in communities called “biofilms” which typically adhere to surfaces.16 Molecular microbiologic techniques have been used recently to detect microorganisms in the amniotic cavity.17–21 The biofilm theory states that most of bacteria that grows in matrix-enclosed biofilms differ from their planktonic counterparts22 (isolated bacteria seen in Gram stain examinations of biologic fluids or of pure cultures). It is now recognized that biofilms play a major role in human disease. Periodontitis, otitis media, endocarditis, prostatitis, biliary tract infections and many other infections in which there is a device (e.g., prosthetic valves, catheters) involve bacterial biofilms.23 Microbial biofilms are important because bacteria in these communities are more resistant to antimicrobial agents and to the host response to infection.24–27 Moreover, since bacteria in biofilms are more difficult to isolate in culture, these infections are often overlooked. The presence of particulate matter in the amniotic fluid in close proximity to the cervix was recognized recently as “amniotic fluid sludge”.28 This finding was associated with microbial invasion of the amniotic cavity, impending preterm delivery and histologic chorioamnionitis.28 Subsequently, these results were confirmed in asymptomatic patients with sludge in mid-trimester of pregnancy29 and in those with cervical cerclage.30 The finding that “amniotic fluid sludge” represents the presence of bacteria and intra-amniotic inflammation has been recently reported.31 Because of the original description of “amniotic fluid sludge”, it has been speculated that this material may reflect the presence of biofilms in the amniotic fluid,28 which is a hypothesis with biological, diagnostic and therapeutic implications. The evidence in support of the contention that microorganisms can form a biofilm in the amniotic cavity is the subject of this case report.