National Research Centre of Medical Sciences of I.R. IRAN
Abstract
Bacterial vaginosis (BV) has been considered to be the most prevalent
infection found in sexually active women. BV is thought to play an
important role in the premature rupture of membranes (PROM) and preterm
birth. Preterm delivery accounts for a substantial percentage of low
birth weight infants and perinatal mortality and morbidity. Bacteroides
and Prevotella species have been isolated from the amniochorion of
women with preterm birth and PROM. Women with >104 /mL Prevotella
bivius (formerly Bacteroides bivius ) have a 60-100% higher rate of
preterm delivery. The purpose of this study was to determine wether
some strains of Prevotella species isolated from PROM and BV patients
produce proteases especially collagenase enzymes which faciliate the
rupture of membranes leading to preterm birth. Vaginal specimens have
been obtained from 120 women with BV and premature rupture of membrane
in 30-44 weeks gestational age. Twenty anaerobic coccobacilli
consisting of Bacteroides fragilis , black pigmented Bacteroides and
Prevotella bivius were isolated and identified. The isolates were
examined for protease activity, using porcine skine gelatin and casein
as substrates by Martleys method. Elastase and collagenase activity
were detected using elastin, guinea pig skin collagen, bovine achilles
tendon collagen, FALGPA and GP,VPK as substrates by Levenson method.
Collagenase and elastase activity was detected in 90 and 100% of
isolates. Gelatinase and caseinase activity was detected in 40 and 50 %
of isolates. Collagenase produced by Prevotella bivia isolates was
purified by ammonium sulphate precipitation, gel filtration and ion
exchange chromatography. The collagenase was cleaved from the synthetic
collagen substrate FALGPA, and GP, VPK substrates. The activity of the
enzyme was inhibited by EDTA, Antipain and PMSF. This study suggests
that proteases produced by Prevotella bivia may be involved in the
pathogenesis of premature rupture of membrane. PROM before 37 weeks has
been reported to be significantly higher among patients with
Bacteroides and Prevotella colonisation of the genital tract. The
amniochorion consists of collagen and elastin which convey physical
integrity to the placenta. Collagenase and elastase released into the
genital tract may promote connective tissue destruction in the cervix
and chorioamnion membranes
