Interpretation
New β-lactamases have emerged rapidly with the development of new β-lactam antibiotics over the past 20 years, and the prevalence of ESBL-producing bacteria is increasing worldwide.1,3-5The prevalence of community-acquired ESBL-E infections among hospitalized patients has also increased in Korea.17In our study, the rate of maternal ESBL-E vaginal colonization increased to 6.2% in the recent period. In a Norwegian study, the prevalence of ESBL-E rectal colonization was 2.9% among pregnant women at 36 weeks of gestation.18 In another study conducted in Sri Lanka, the pre-delivery ESBL-E lower vaginal colonization rate was 1.6%.19
Our data are in line with previously reported findings that prior use of antibiotics, particularly fluoroquinolone and cephalosporin, is a risk factor for ESBL-E infection in hospitalized patients.1,2 It is well recognized that an increase in the rate of ESBL-E infection is associated with the widespread use of antibiotics.1,2,20-22 In our study, the multivariate analysis confirmed that prior antibiotic treatment and cerclage were the independent risk factors for ESBL-E vaginal colonization in high-risk pregnant patients. In fact, previous studies have suggested that antibiotic administration during pregnancy may alter the vaginal microbiological ecology.23,24 For example, lessLactobacillus species colonization than expected was reported in pregnant women using antibiotics, and an increased vaginal colonization rate by E. coli was reported after antibiotic use during pregnancy.24 Similar to the general population, prolonged antibiotic use in pregnant women is also a known risk factor for ESBL-producing bacterial infection.12,13Similarly, our study also showed that the duration of antibiotic administration was significantly longer in the ESBL-E-positive group. Clinically, the proper use of antibiotics during pregnancy is very important for the health of both the mother and fetus.25 Considering our study results, antibiotic treatment during pregnancy could be a risk factor for ESBL-E vaginal colonization infection and thus should be used only when needed. Therefore, our study also indirectly supports the limited exposure to antibiotics during pregnancy with narrow-spectrum antibiotics, if possible.
Cerclage is an effective treatment option for preventing PTB in women with cervical incompetency.26,27 In several studies, dilated cervix and short CL were associated with a paucity ofLactobacillus species in the vagina.28,29 A reduced abundance of normal vaginal flora could make it vulnerable to colonization by abnormal vaginal flora. Previous studies have suggested that cerclage increases the risk of maternal infection requiring medical intervention and puerperal pyrexia27,30; the possibility of vaginal dysbiosis owing to the effects of suture materials has also been suggested.31 Our study found that cerclage was associated with the risk of ESBL-E vaginal colonization. However, it is unclear whether cerclage is the cause or result of ESBL-E vaginal colonization. Similarly, one study confirmed that when postoperative vaginal culture was performed in patients undergoing cerclage, more than 75% of the samples were positive forE. coli. 32 Based on the results of these studies, it is necessary to consider the risks and benefits when deciding whether to perform cerclage.
Abnormal vaginal colonization by E. coli or K. pneumoniaeduring pregnancy is clinically important with respect to neonatal infection and PTB.33-36 Especially, ESBL-E is very important because it has been reported to be the major cause of neonatal infection, which increases neonatal mortality owing to limitations in therapeutic options.10,37,38 In light of this importance, it is considerably regrettable that there are only a few studies on the screening or treatment of ESBL-E colonization in pregnant women.
The organisms known to cause EONS are generally colonized in the maternal genito-urinary tract.39 Among them, maternalE. coli vaginal colonization has been widely studied as an independent risk factor for neonatal E. colisepsis.40,41 In addition, a previous study has shown that EONS with E. coli was associated with worse perinatal outcomes compared with EONS with group BStreptococcus. 42 For this reason, neonatalE. coli sepsis, especially ESBL-E sepsis, which is difficult to treat, is emerging as an important condition. A recent study on ESBL-E infection during pregnancy identified that maternal ESBL-E colonization is an important risk factor for vertical transmission. The authors explained that the rate of ESBL-E-positive postnatal swabs was significantly higher in neonates born to mothers who were positive for ESBL-E colonization at delivery.43 Among the total neonatal sepsis cases in the ESBL-E-positive group in our study, ESBL-E was identified in five cases. Consequently, the mother-to-neonate transmission rate of ESBL-E infection was estimated to be 7.6% (5/66). According to a Sri Lankan study, the mother-to-neonate transmission rate of Enterobacteriaceae was 6.9%, of which ESBL producers had a transmission rate of 0.6%.19 Another study reported a mother-to-neonate ESBL-E transmission rate of 34.3%.44 Our study also confirmed that the rate of proven EONS was significantly higher in the ESBL-E-colonized mothers. This finding supports the results of previous studies and highlights the importance of evaluating the need for screening and treatment for ESBL-E colonization in high-risk pregnancies.