Bacterial growth in amniotic fluid is dependent on the iron-availability and the activity of bacterial iron-uptake system.
In the present study, the relationship among iron-availability, antibacterial activity, role of meconium as an iron source and the activity of bacterial iron-uptake system (IUS) for bacterial growth in amniotic fluid (AF) were investigated. Staphylococcus aureus ATCC 6538 and its streptonigrin-resistant (SR) mutant with defective IUS were used as the test strains. The growth of S. aureus in AF was stimulated dose-dependently by addition of meconium. Bacterial growth stimulated by meconium was re-inhibited dose-dependently by addition of iron-chelator, dipyridyl and apotransferrin. Iron concentration was correlated with the meconium content in AF (r(2)= 0.989, p=0.001). High-affinity IUS of S. aureus was expressed only in AF but not in AF with meconium. The growth of SR strain was more retarded than that of the parental strain in the iron-deficient brain heart infusion (ID-BHI), clear AF and AF containing apotransferrin. The retarded growth of both strains in the ID-BHI and AF was recovered by addition of holotransferrin, hemoglobin and FeCl3. Taken together, the antibacterial activity of AF is closely related with low iron-availability. Bacterial growth in AF considerably depends on the activity of bacterial IUS. Meconium acts as one of the exogenous iron-sources and thus can stimulate bacterial growth in AF.
Ahn
Young-Joon
YJ
Department of Pediatrics, Seonam University Medical School, Namwon, Korea. shsin@chosun.ac.kr
Park
Sang-Kee
SK
Oh
Jae-Wook
JW
Sun
Hui Yu
HY
Shin
Sung-Heui
SH
D000653:Amniotic Fluid / Q000382:microbiology*; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D002614:Chelating Agents / Q000494:pharmacology; D002712:Chlorides; D004305:Dose-Response Relationship, Drug; D005260:Female; D005290:Ferric Compounds / Q000494:pharmacology; D006801:Humans; D007501:Iron / Q000378:metabolism*; D008024:Ligands; D008470:Meconium / Q000378:metabolism; D009154:Mutation; D011247:Pregnancy; D011263:Pregnancy Trimester, Third; D011485:Protein Binding; D013211:Staphylococcus aureus / Q000378:metabolism; D013308:Streptonigrin / Q000494:pharmacology; D013997:Time Factors
D000903:Antibiotics, Antineoplastic; D002614:Chelating Agents; D002712:Chlorides; D005290:Ferric Compounds; D008024:Ligands; D013308:Streptonigrin; D007501:Iron; C024555:ferric chloride