Answer

Identification of Pathogenic Bacteria that may Cause an Increase in Preterm Delivery

Abstract

The purpose of the proposed study is to identify pathogenic bacteria that are present in preterm births but are not associated with bacterial vaginosis. Preterm birth is defined as delivery that occurs before 37 weeks of gestation.^1,2 This paper provides the background, aims and objectives, significance and justification (innovation) of the study, review of current literature, methodology, and a conclusive statement. It is expected that pathogenic bacteria found in the vaginal tract of pregnant women plays a significant role in the initiation of preterm births. To establish this, microbiological samples collected from women who have carried pregnancy to term and women whom have experienced preterm births will be compared. A convenience sample will be taken from a hospital or clinic in which the study will be conducted. Data will be analyzed using SPSS, measures of central tendency, and descriptive statistics. Preterm birth is a considered a multi-etiological occurrence; however, the proposed study aims to establish the role played by female urinary tract pathogenic infections that are not identified to cause bacterial vaginoses but in causation of preterm births.

Key words: preterm birth, bacterial vaginosis, microbiota, Gardnerella vaginalis, and Lactobacilli.

Hypothesis: Pathogenic bacterial species that colonize the vaginal tract of pregnant women increases the risk of preterm birth.

Objectives

1. To identify and compare pathogenic bacterial species in vaginal tract of women who experienced preterm birth and in women who carried pregnancy to term.
2. To determine and compare the abundance of pathogenic species in women who had preterm birth and those who carried pregnancy to term.
3. To determine whether the frequency and abundance of pathogenic bacterial species is correlated with the number of preterm births.
4. To come up with a list of specific pathogenic bacterial species associated with preterm births for further studies.

Potential Impacts of the Proposed Research

            The major potential impact of the study is to reduce the risk of preterm birth through identification and treatment of pathogenic bacteria that infect the vaginal canal. Preterm birth is a public health issue since it reduces infant survival due to complications and may contribute to medical morbidity and adverse developmental issues.² Preterm birth is an important public health issue due to its economic impact and its link to morbidity and mortality to children under the age of 5 years.¹ Approximately 15 million preterm births are recorded annually around the world; thus, worldwide preterm birth rate is approximately 11%. About 1 million children die annually as a consequence of preterm birth.¹⁴ Reduced risk of preterm birth, through development of effective strategies to manage pathogenic bacteria, can reduce the burden of morbidity and mortality in children under the age of 5 years. Prevention of preterm births can also shield children from the risk of development challenges such as sensorial, neurodevelopmental, physical, and cognitive health disturbances.⁸ The project can promote achievement of the United Nations’ Sustainable Development Goal three (3) target number 3.2 that purposes to end all preventable-deaths of children (<5 years) and newborns by the year 2020.¹⁴ Besides, findings will be used for the purposes of educating healthcare providers and patients so as to improve outcomes; particular reduced risk of preterm births and improved survival of newborns and children.⁵

Background

Pre-mature Birth

            Pre-mature birth is delivery that occurs before 37 weeks of gestation. Very preterm birth occurs before 32 weeks of gestation while extreme preterm birth occurs before 28 weeks of gestation.⁹ Moderate or late preterm birth occurs within 32 to less than 37 weeks of gestation.⁹ In 2013, it was estimated that more than 1 in 10 infants were born preterm, which accounted for about 15 million premature babies globally. Among prematurely born babies, 1 million children under the age of five years die every year due to complications of preterm birth.² Very preterm infants seem to experience long-term medical morbidity and adverse neurodevelopmental issues such as neurosensory, motor, behavioral, and cognitive deficits.² Preterm births have disproportionate impact on middle- and low-income countries. It contributes to about one million neonatal deaths per year, and is considered as a significant contributor to childhood morbidity.⁹ In addition, preterm birth is associated with increased risk of gastrointestinal complications, respiratory complications, and central nervous system impairment.⁴

Pathogenic Bacteria of the Female Genital Tract

            Potentially, pathogen bacteria colonizing the lower female genital tract can be passed to the infant at birth. Reduction in Lactobacillus population from the lower female genital tract is associated with infection by pathogenic bacteria, for example, by members of the Enterobacteriaceae family and Staphylococcus aureus. Lower genital infections that can be seeded to the newborn during the birth process include; group B Streptococcus, S. aureus, group A Streptococcus, Citrobacter, Pseudomonas spp., Escherichia coli, Klebsiella pneumonia, and Enterobacter spp..¹³

Bacterial Vaginosis among Pregnant Women

            A healthy vagina harbors a microbiome, which is dominated by hydrogen peroxide and lactic acid producing bacteria, which provide protection against harmful or pathogenic infections by maintaining a low pH. Changes in the composition of normal microbiota lead to bacterial vaginosis.¹⁰ Bacterial vaginosis is caused by overgrowth of the vaginal normal flora.⁶ Bacterial vaginosis often presents with vaginal discharge, which has a fish-like odor. The discharge is either white or grey and typically thin in nature. Bacterial vaginosis increases the risk for occurrence of other sexually transmitted infections. Besides, pregnant women who are diagnosed with bacterial vaginosis tend to experience an increased risk of preterm birt.⁶ However, bacterial vaginosis is not contagious. The condition is often associated with a decrease in the normal hydrogen-peroxide-producing Lactobacilli with anaerobic bacteria overgrowth. In historical perspective, Gardnerella vaginitis was the term that was used to refer to bacterial vaginitis since there was a common believe that Gardnerella spp. was the etiological agent of the condition.⁶

Aims

The goal of conducting the proposed study is to investigate whether pathogenic bacteria (apart from those established as causes of bacterial vaginosis) increase the risk of preterm birth.

Specific Aim I: Determining the abundance and species composition of pathogenic bacteria present in patients with preterm births.

1. To isolate pathogen in the vaginal canal of women who had preterm birth and in those who had full-term birth.
2. To identify the species of pathogenic bacteria from the collected samples.
3. To determine abundance of pathogenic bacteria from vaginal tract.
4. To calculate abundance of pathogen bacteria

Specific Aim II: Does the frequency and abundance of these identified bacteria correlate with premature delivery?

1. To determine the correlation between frequency and abundance of pathogenic bacteria and preterm birth.
2. To determine the correlation between frequency and abundance of pathogenic bacteria and full-term birth.
3. To compare the risk of pathogenic bacteria in association with preterm birth compared to women who experienced full-term birth.

Research Strategy

1. Significance and Justification of the Proposed Study

            Preterm birth is associated with an increased risk of medical complications, death of the new born, and neurodevelopmental sequelae.² Causes of preterm birth have not been described. Evidence is not clear in current literature. Preterm birth is most often associated with preterm labor, premature rupture of membranes, and maternal medical conditions.² Predictors of preterm labor include smoking, low socioeconomic status, previous history of preterm labor, and multiple pregnancies.¹² Other issues that are associated with preterm birth include hormonal changes, cervical incompetence, antepartum hemorrhage, inflammation and bacterial infection.⁹ The investigator aims are to determine whether there is a significant occurrence association of pathogenic bacteria in the upper and lower regions of the vagina which are not part of the group associated with bacterial vaginosis which may play a possible causative effect in preterm birth.

1. Innovation Novel Concepts

            Preterm birth is a major global health issue and continues to contribute to significant neonatal mortality and morbidity. This occurs regardless of advances that have been made in neonatal care and obstetrics. The underlying cause of preterm birth remains incompletely understood and multifactorial. It is estimated that 1 million deaths due to preterm birth occur globally per annum.^9,10 About one third of these preterm deaths is caused by infections.³ Abnormal composition of the reproductive track is associated with an increased risk of premature pre-labor which results in infection by pathogenic bacteria.¹ Vaginal symptoms, such as itching, odor and discharge, cause discomfort and suffering in reproductive age women. These symptoms are associated with recurrent vulvovaginal infections, which have become a serious clinical and epidemiological problem.⁷ Infection is present in about 25% of cases of preterm labor. Similarly, about 79% of extreme cases of preterm birth are associated with infectious agents. Inflammatory and infectious processes are associated with worse prognosis.¹²

            Recurrent vulvovaginal infections may lead complications such as preterm birth, infertility, other infectious diseases, and miscarriages. Due to these complications on the wellbeing and reproductive health of women, vaginal infections have proved to be key public health concern around the world.⁷ Imbalance in normal flora may result in infection by pathogenic bacteria and chorioamnionitis, which is the chief cause of preterm delivery. Use of metronidazole up to 20^th gestational week helps to reduce the risk of preterm delivery.¹¹

            Bacteria such as Lactobacillus lactis are associated with an intra-vaginal cleansing effect in a normal pregnancy. L. lactis helps to minimize the presence of normal flora.¹¹ Vaginal microbiome tends to become less diverse and more stable as pregnancy progresses on, which confers protective effect against genital tract infection. Normal flora that often colonize the vaginal tract in pregnancy do not cause vaginitis or inflammatory conditions. However, pathogenic bacteria can cause vaginitis and inflammation.¹¹ Unbalanced composition of vaginal microbiota results in inflammation (vaginitis), and vulvovaginal infections. Vulvovaginal infection is named in accordance to the type of the infectious organisms that are present in the vagina, and responsible for causing the infection and associated symptoms.  Symptoms include; excessive vaginal discharge (non-offensive/offensive), fissuring, soreness, edema, vulval itching, erythema, dyspareunia, skin lesions, and dysuria.⁷

            Evidence suggests that inflammation or infection is a major contributor to early spontaneous pre-term birth.¹² In a study by Tedesco, it was established that 65.9% of women who experienced spontaneous pre-term birth had reported having urinary tract infection during pregnancy.¹² Urinary tract infection is associated with long-term morbidity and neonatal death. Preterm birth occurs in about 10.6% of all pregnancies in the world, and is the leading cause of perinatal mortality. Children who survive preterm birth are likely to develop a collection of long- and medium-term complications such a developmental delay, cerebral palsy, and retinopathy of prematurity, at a rate of 50 to 75%. In addition, preterm birth can have a significant burden on pregnant women and their family members, which may increase emotional stress and anxiety.¹²

            Preterm birth may be a clinical manifestation of the invasion of the amniotic cavity by infectious microorganisms. Inflammatory cytokines are detectable in the cord blood samples, which are collected from preterm neonates associated with the occurrence of chorioamnionitis. This condition is probably a result of altered membrane and placental microbiome, which appear to trigger the onset of preterm birth and premature rupture of membranes.¹²

1. Approach

Design

This proposed study assumes a quasi-experimental design involving the use of a convenience sampling technique. The investigator needs to scout for a hospital or clinic with a midwifery and post-natal unit in which the study can be conducted.

Sampling

            A convenience sample of 100 women will be recruited into the study. Among these will include 50 women who just had preterm birth (within a period of 30 days) to serve as experimental group and 50 women who had carried their pregnancy to full-term as control group. Participants will be required to sign informed consent forms before their involvement in the study.

Data Collection

            Samples will be collected from vaginal swabs from the participants weekly for a period of one month. Observations will be made on the appearance of vaginal discharge and the pH will be determined and recorded for each the sample. Vaginal smear for each sample will be prepared in three replicates and subsequently Gram stained for microscopic analysis to identify bacterial species, counts, and abundance of pathogenic organisms in vaginal samples. Refer to Table 1 below for data sheet. Automated counting of bacterial cells will also be done using Quantom Tx^TM microbial cell counter¹⁶. Refer to Figure 1. In addition, vaginal smear for potassium hydroxide for testing for fungal infection and saline wet-mount for bacterial vaginosis will also be made. Clue cells will be identified on wet-mount; whereas, amine odor test will be detected after potassium hydroxide application. Vaginal wash will be taken for gas-liquid chromatographic analysis and culture. Gas-liquid chromatography helps identify species-specific bacterial fatty acids. Refer to Figure 2. Qauntom TX^TM and gas-liquid chromatography will facilitate realization of specific aim I, which is determination of the abundance and species composition of pathogenic bacteria present in patients with preterm births. Single colonies of microorganisms will be identified by culture under microscopic analysis.

Figure 1: Exemplar of how Quantom Tx^Tm works to count microbial cells¹⁶.

Figure 2: Exemplar of representative chromatographs of various bacteria generated by gas-liquid chromatography¹⁷.

            Microscopic analysis is necessary so as to determine composition (naming, type), and identify bacterial species, counts, and abundance of pathogenic organisms in vaginal samples. The frequency and abundance of pathogenic bacteria will be determined statically from the data generated in Excel. Subsequently, correlation between abundance of pathogenic bacteria and occurrence of preterm birth will be established.

Table 1: Data Sheet

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Presentation and Analysis of Data

                        Data will be analyzed using Statistical Package for Social Sciences (SPSS) software for correlation analysis descriptive statistics and measures of central tendency will be used for data processing. Analyzed data will be presented in terms of percentages, graphs, and tables. Processed data using SPSS software and other data analytical tools will help in realization of specific aim II, which is to determine whether frequency and abundance of the identified pathogenic bacteria correlate with premature delivery.

Expected Outcomes

                        It is expected that pathogenic bacteria will be more abundant in women who have had preterm births compared to those who had full-term deliveries. It is projected that particular pathogenic bacteria may be playing a key role in contributing to preterm deliveries rather than a combination of various pathogenic bacteria. Besides, there will be a statistically significant correlation between the presence of pathogenic bacteria in the vaginal tract and preterm delivery. Full-term delivery will act as a negative control for the study.

Potential Pitfalls and Alternative Strategies

                        This study aims to use a convenience sample but women who have preterm births may not be that common. A total of 50 women who have just experienced preterm birth will be recruited; thus, the study may take a long time to complete since it may be difficult to recruit suitable subjects. In addition, not all women who have just experienced preterm birth may give informed consent to participate in the study. To reduce the impact of this risk of affecting the outcome of the study, the investigator plans to carry-out the studies in more hospitals so as to increase the chance of recruiting suitable subjects and to shorten the project lifespan.

Ethical Implication

                        Since the study will involve human participants, the study needs approval from the Institutional Ethical Review Board at Southeastern University. Consideration of ethical and legal implications of research forms a critical component of modern research.  Informed consent, confidentiality, whether to provide incentives or not, and how to avoid research misconduct are important concerns in the proposed study.¹⁵ The Declaration of Helsinki recognized ethical principles that need to be applied in any research that involves human subjects.¹⁵ The investigator has a duty to protect dignity, life, right to self-determination, health, confidentiality, and privacy of each and every research participant.¹⁵