Introduction
Acute postpartum bacterial skin infection refers to the emergence of common complications after childbirth, the problem of the drug resistance of pathogenic bacteria has become the important influence factors for the treatment and prognosis [1]. In recent years, with the widespread use and abuse of antibiotics, the problem of bacterial resistance has become increasingly serious [2, 3]. Therefore, understanding the drug resistance of pathogenic bacteria in patients with acute bacterial skin infections are of great significance for clinical practice. Acute bacterial skin infections are caused by a variety of bacteria, among which the most common pathogens include Staphylococcus aureus, Streptococcus, and Escherichia coli [4]. After reaching the skin, these bacteria invade the body by destroying the skin barrier or using surgical incisions and other ways to cause infection. However, due to the widespread use of antibiotics, the increasing resistance of these pathogens makes treatment more difficult. At present, postpartum and the treatment of acute bacterial skin infections mainly depends on the antibiotic [5]. However, due to the increase in resistance, traditional antibiotics may not be able to effectively kill bacteria. Therefore, understanding the resistance of pathogenic bacteria to different antibiotics can help doctors choose the appropriate antibiotic treatment plan and improve the treatment effect.
T cells is an important part of the immune system, and are able to identify and kill microorganisms [6]. T lymphocytes can be divided into several subsets, including helper T cells (CD4+ T cells) and cytotoxic T cells (CD8+ T cells) [7, 8]. Helper T cells are primarily responsible for recognizing antigens and activating other immune cells, such as B lymphocytes and macrophages, to enhance the immune response. Cytotoxic T cells are able to directly kill infected or abnormal cells, such as cancer cells. T lymphocytes bind to antigens through T cell receptors (TCR) on the surface, thereby recognizing and responding to foreign antigens [9]. Once activated, T lymphocytes produce cytokines and are involved in regulating and coordinating various aspects of the immune response. They play important roles in immune responses such as anti-infection, anti-tumour, and autoimmunity. The dysfunction or decrease in the number of T lymphocytes can lead to the dysfunction of the immune system, which may cause diseases such as immunodeficiency diseases, autoimmune diseases, and malignant tumors [10]. Therefore, the study of T lymphocytes in understanding the normal function of the immune system and related mechanism of the occurrence of diseases is of great significance. However, in acute postpartum bacterial skin infections, the function of T lymphocytes may be suppressed, resulting in an inadequate immune response. Therefore, it is important to explore the changes of T lymphocytes in acute postpartum bacterial skin infections to understand the regulation of immune mechanisms. Inflammatory factor is a kind of protein molecules produced by immune cells, they play a major role in the process of inflammation [11, 12]. Inflammatory factors can promote the occurrence and maintenance of inflammatory response, and participate in the activation, proliferation, and migration of immune cells. Inflammatory factors are produced in large quantities in pathological processes such as infection, tissue injury, and autoimmunity, which can cause inflammatory symptoms such as vascular dilatation, tissue oedema, pain, and fever [13]. Excessive production or abnormal regulation of inflammatory factors is closely related to the occurrence and development of many diseases, such as rheumatoid arthritis, inflammatory bowel disease, asthma, cardiovascular disease [14]. Acute bacterial skin infections due to inflammation factors in postpartum plays an important role. The production and release of inflammatory factors can trigger inflammatory responses and participate in the process of bacterial clearance and tissue repair [15]. However, excessive inflammation may cause tissue damage and disease progression. Therefore, the inflammation factor in postpartum changes in acute bacterial skin infections to evaluate the degree of inflammation, and to provide basis for clinical treatment.
Aim
This study aimed to analyse drug resistance of pathogens in patients with acute postpartum bacterial skin infections and the differences in T lymphocytes and inflammatory factors. Through this article, it hopes to deeply understand the changes of pathogen resistance and immune mecha nism in patients with acute postpartum bacterial skin infections, and provide more accurate guidance and in dividualized treatment strategies for clinical treatment.
Material and methods
This was a case control study in the Department of Obstetrics and Gynaecology of the Zhongxian People’s Hospital in Chongqing from 2022 to 2023. One hundred patients with acute bacterial skin infections were selected as the experimental subjects, and the pathogenic bacteria on the maternal body were collected and cultured. In addition, healthy maternal 100 cases matched based on age, pregnancy delivery route, and parity, were enrolled as controls. Acquisition of two groups of maternal peripheral blood samples, T lymphocyte subsets distribution was detected. All the participants were informed and the experiment was approved by the Ethics committee of the Zhongxian People’s Hospital in Chongqing.
Experiment method
Pathogenic bacteria from 100 postpartum patients with acute bacterial skin infections were isolated and these patients were identified as the experimental subjects. Standard microbiological methods, including culture, staining, and biochemical tests, were used to identify the pathogens. Moreover, a drug sensitivity test was used to test the sensitivity of different antibiotics to pathogenic bacteria. 100 healthy parturients were selected as the controls. Peripheral blood samples were collected from the two groups of patients. Flow cytometry was used to detect the distribution of T lymphocyte subsets, including CD4+T cells, CD8+T cells, Th1 cells, Th2 cells, etc. The levels of inflammatory factors such as IL-6 were detected by enzyme-linked immunosorbent assay (ELISA).
Culture of pathogenic bacteria
Through the culture of pathogenic bacteria, drug sensitivity tests can be carried out to determine the sensitivity of pathogens to different antibiotics, to guide the clinical drug selection and treatment plan. The detailed steps are displayed in Table 1.
Table 1
Specific steps of bacterial culture
Drug susceptibility testing
Drug susceptibility testing is performed by assessing the sensitivity of different antibiotics to pathogens [16]. This test is a common and important case method for determining optimal treatment and preventing the development of antibiotic resistance. In this experiment, conventional antibiotics were selected for testing, including different antibiotics such as penicillin, erythromycin, azithromycin, gentamicin, and doxycycline. These antibiotics represent different classes of drugs and are widely used in clinical practice. In drug susceptibility testing, pathogens were exposed to different concentrations of antibiotics and their responses to antibiotics were observed. By measuring the degree of growth or inhibition of the bacteria, the susceptibility of the pathogen to antibiotics can be determined. If the pathogen is highly susceptible to a particular antibiotic, that antibiotic will be the drug of choice for treating the infection. Conversely, if the pathogen becomes resistant to a certain antibiotic, then other treatment options need to be considered to avoid treatment failure. The specific steps are displayed in Table 2.
Table 2
Drug sensitive test steps
Inflammatory inflammation detection
In order to detect the content of inflammatory factors such as IL-6, ELISA can also be used [17]. First, the serum to be tested was added to a 96-well plate precoated with the specific antibody. These specific antibodies bound to IL-6. The orifice plate was incubated for a period, so that IL-6 or TNF-α in the sample to be tested combined with antibodies. Next, the well plate needed to be washed to remove unbound material. This would reduce the possibility of false positive results. Then, HRP-labeled secondary antibody was put and the well plates were incubated for a period for the secondary antibody to bind to the IL-6 antibody complex. HRP is an enzyme that binds to the secondary antibody. The well plate was washed again to remove the unbound secondary antibody. Then, the substrate solution was added and the well plates were incubated for a period to allow the substrate to react with HRP and produce a detectable signal. The choice of substrate depended on the enzyme used. Finally, a stop solution was applied to stop the reaction of the substrate with HRP. Then, an enzyme standard instrument was used to measure absorbance value, determining the content of IL-6. A higher absorbance value indicated a higher amount of IL-6 in the sample. In conclusion, ELISA is a commonly used immunological case technique that can be used to detect and quantitatively analyse the presence of specific antigens or antibodies. By combining the enzyme-labeled antibody or antigen with the target substance in the sample to be tested, and then producing a measurable signal through the reaction of the enzyme substrate, the content of the target substance was determined.
T lymphocytes detected by flow cytometry
Flow cytometry is a technique used to analyse and count cells [18]. It analyses cell characteristics by passing a cell suspension through an elongated tube, then illuminating the cell using a laser beam and detecting the light signal reflected or emitted by the cell. In flow cytometry, specific antibodies are used to label specific proteins on the surface of T lymphocytes, such as CD3, CD4, and CD8, among others. These antibodies bind to fluorescent dyes so that when cells pass through a flow cytometer, the fluorescent signal can be detected to determine the expression of specific proteins in the cells. By detecting T lymphocytes by flow cytometry, information on T lymphocyte subsets, such as the proportion of CD4+ and CD8+ T cells, can be obtained. In addition, the functional status of T lymphocytes can be assessed by detecting other markers, such as apoptosis markers or activation markers.
Statistical analysis
Data analysis was performed using SPSS 22 software. All case data were presented as means. Continuous variables were compared using t test or analysis of variance (ANOVA). For categorical variables, either the χ2 test or Fisher’s exact test can be adopted. Correlation analysis was performed using Pearson’s correlation coefficient or Spearman’s rank correlation coefficient. A p-value of less than 0.05 was considered statistically significant.
Results
The general data of the patients are displayed in Table 3. While the experimental group, on average, is slightly older (26.91 ±4.9 years) than the controls (25.61 ±5.3 years), both groups exhibit a comparable number of cases with multiparity. Notably, the experimental subjects show a slightly higher inci dence of first births (49 cases) compared to the controls (47 cases). Moreover, the mode of delivery demonstrates a nuanced difference, with both groups predominantly experiencing normal deliveries; however, the experimental group has a slightly higher percentage of cesarean deliveries (41%) compared to the controls (38%). Meanwhile there were no statistically significant differences in maternal age, frequency of delivery, and mode of delivery between the two groups (p > 0.05).
Table 3
Contrast of general data of parturients
Significant differences were observed in multiple immunological and inflammatory markers. The experimental subjects exhibited a lower CD4+ percentage (36.39 ±4.12) compared to controls (47.49 ±3.29), resulting in a significantly reduced CD4+/CD8+ ratio (1.24 ±0.05) in experimental subjects as opposed to controls (1.675 ±0.11). Additionally, the Th/Treg ratio is significantly lower in experimental subjects (1.22 ±1.29) compared to controls (1.67 ±0.89). Elevated levels of IL-4 (47.69 ±6.24), IL-10 (32.46 ±5.3), and hs-CRP (3.24 ±0.21) in experimental subjects, as opposed to controls (IL-4: 29.98 ±4.35, IL-10: 15.14 ±4.71, hs-CRP: 1.83 ±0.74), p < 0.05. However, there was no obvious difference in CD8+ between the controls and the experimental subjects (p = 0.678).
As illustrated in Figure 1, the main pathogens (more than 10%) in patients with acute postpartum bacterial skin infections were Staphylococcus aureus (30.13%), β-hemolytic streptococcus (20.41%), Escherichia coli (14.71%), and Pseudomonas aeruginosa (9.81%).
Gram-positive bacteria such as Staphylococcus aureus and β-hemolytic Streptococcus showed high resistance to penicillin, erythromycin, clindamycin, and tetracycline, but were sensitive to linezolid and vancomycin. Gram-negative bacteria such as Escherichia coli and Pseudomonas aeruginosa were highly resistant to amoxicillin, ampicillin, aztreonam, ceftriaxone, cefazolin, and ciprofloxacin, and were more sensitive to imipenem (Figure 2).
Discussion
Our study’s immunological assessments indicated lower CD4+ and CD4+/CD8+ ratios, elevated Th17/Treg, and increased IL-4, IL-10, and hs-CRP levels in infected patients compared to normal parturients. Acute postpartum bacterial skin infections refer to bacterial infections caused by wound breakage and infections during delivery [19, 20]. The infections are mainly caused by a broken wound during delivery, allowing the bacteria to enter the body and multiply on the skin. These bacteria can be the normal flora on the skin surface, or they can be pathogenic bacteria in the external environment. The harm of acute bacterial skin infections cannot be ignored [21, 22]. Firstly, it can cause local redness, pain, and pus discharge, which seriously affects the quality of life of patients. Second, in severe cases, the infection can spread throughout the body, leading to sepsis and other systemic symptoms of the infection [23, 24]. Sepsis is a serious infectious disease, which can cause symptoms such as high fever, chills, rapid heart rate, and hypotension, and even threaten life [25]. For pregnant women, infections may also delay wound healing and increase the risk of postoperative complications [26]. For infants, the infection may be transmitted through breast milk or direct contact, posing a threat to their health [27].
Compared with other studies [28, 29], this article can provide guidance for clinicians to choose appropriate antibiotic treatment by analysing the drug resistance of pathogens in patients with acute postpartum bacterial skin infections. Analysing the differences of T lymphocytes can allow for understanding the role of the immune system in acute postpartum bacterial skin infections, and provide new ideas for treatment. Analysis of the differences in inflammatory factors can allow for understanding the degree and characteristics of inflammatory response in the acute postpartum bacterial skin infection, and provide reference for assessing the severity and prognosis of the disease. However, there are some limitations. First, the sample size is small, which may lead to a bias in the results. Second, only T lymphocyte subsets and several inflammatory factors are tested, and other immune indicators are not analysed. Finally, this article is an observational study and lacks evaluation of interventions.
The role of CD4+ and CD8+ T cells in bacterial skin infections has been investigated in various studies. Notably, a study demonstrated that antigen-specific CD4−CD8−Thy1+ cells played a significant role in controlling the growth of Francisella tularensis in murine bone marrow-derived macrophages in vitro [30]. Another study explored the recruitment of CD8+ T cells to the skin after acute viral infection, highlighting the independent nature of CD8+ T cell recruitment [31]. Additionally, research indicates alterations in T lymphocyte subsets, such as lower CD4+ and CD4+/CD8+ ratios, and elevated Th17/Treg in patients with acute postpartum bacterial skin infections compared to normal parturients [32].
As well as our study, patients with acute postpartum bacterial skin infections exhibit lower CD4+ levels and altered CD4+/CD8+ ratios compared to normal parturients in study of Burns et al. [33].
Conclusions
The drug resistance of common pathogens in patients with acute postpartum bacterial skin infections is mainly concentrated in Staphylococcus aureus and Escherichia coli. The immune system plays a key regulatory role in the process of the infection, and the differences in the expression of T lymphocytes and inflammatory factors are particularly significant. These results provide an important reference for clinical treatment and help to improve the treatment effect of the acute postpartum bacterial skin infection.
