رسائل دكتوراة
English
2023
Bacteriological and Immunological Study of Some Sepsis Biomarkers among Bacteremic Patients in Hilla City
حسين عليوي مطلب الدهموشي, مؤيد مهدي كاظم حسن
كلية العلوم-جامعة بابل · العراق
Bacteremia is a bacterial infection that has spread from the primary site of infection and reached the bloodstream. Continuously present bacterial agents within the circulation can cause serious body illnesses leading to sepsis, particularly when the laboratory procedures fail to recognize the actual etiological agents. Sepsis is a complex inflammatory response that is strongly associated with multiple organ dysfunction and considered as a major cause of morbidity and mortality worldwide. Bacteremia and sepsis confirmation can be achieved using many assays including cultural, immunological, and molecular methods. The current study aims to evaluate the potential sepsis biomarkers among culturable and unculturable bacteremia among clinically suspected sepsis patients. Blood culture and the PNEUMOBACT IFA test were used to detect the culturable and unculturable causative agents of bloodstream infection. Complete Blood Count (CBC), C-Reactive Protein (CRP), and Lactate Dehydrogenase (LDH) were used as valuable routine screening tests for bacteremia/septicemia, while Procalcitonin (PCT), Presepsin (PSN), and Pentraxin-3 (PTX3) were used as three potential biomarkers of sepsis.
A total of 100 blood samples from patients with symptoms of sepsis who resided in the Hilla City hospitals were collected, as well as 25 samples collected from healthy persons as a control group. Each blood sample was divided into three containers: 2 ml in an EDTA tube for the CBC test, 3 ml in a centrifuged tube to separate serum for the CRP, LDH, PCT, PSN, PTX3, and IFA tests, and 5 ml in brain heart infusion broth (BHI) for blood culture.
The results showed that 65/100 (65%) samples had abnormal (elevated CBC parameters, CRP, and LDH) screening tests, whereas only 25/65 (38.4%) of them gave positive results for blood culture. All control group persons had normal results of CBC, CRP, and LDH, and they gave negative results for blood culture. The 25 bacterial isolates identified by the Vitek 2 compact system were: Staphylococcus aureus 6 (24%), Staphylococcus epidermidis 4 (16%), Stenotrophomonas maltophilia 2 (8%), Escherichia coli 2 (8%), Streptococcus pneumoniae 2 (8%), Salmonella typhi 1 (4%), Staphylococcus hemolyticus 1 (4%), Klebsiella pneumoniae 1 (4%), Morganella morganii 1 (4%), Pseudomonas aeruginosa 1 (4%), Staphylococcus hominis 1 (4%), Kocuria kristinae 1 (4%), Enterobacter aerogenes 1 (4%), and Pseudomonas stutzeri 1 (4%). Most of these isolates were multidrug resistant when tested with the chosen antimicrobial agents.
Regarding routine screening tests (CRP, CBC, and LDH), statistical analysis shows a highly significant difference (P-value ≤ 0.001) between patients (n=65) and control groups (n=25). Non-significant differences in those parameters were observed between culture-positive and culture-negative patients (P-value > 0.05). On the other hand, these parameters had a significant strong correlation among them. In addition to that, there were no significant differences between males and females regarding CBC, CRP, and LDH for those who gave culture-positive (P > 0.05). Males and females who gave culture-negative also did not differ significantly (P > 0.05).
The serum levels of PCT, PSN, and PTX3 were determined by the ELISA test during the next part of the study. Statistical analysis (Duncan test) reveals that the control group had a highly significant difference from the patients (CPS and CNS) regarding PSN and PCT concentration (having different small letters in one row), while the difference was non-significant for the PTX3 concentration among patients and the control group (having the same small letters in one row). Furthermore, PSN and PCT concentrations did not significantly differ between the culture-positive and culture-negative groups of sepsis. The PSN and PCT concentrations have a strong positive correlation between them (r = 0.500; P < 0.001).
The results of the indirect immunofluorescent assay revealed that 36/40 (90%) out of 40 culture-negative serum samples had anti-bacterial antibodies identified based on this method, and these antibodies related to: Legionella pneumophila, Chlamydia pneumoniae, Mycoplasma pneumoniae, Coxiella burnetii, Chlamydia psittaci. Co-infections were present (each test gave positive reactions to different specific antibodies that belonged to more than one microorganism). The results of all investigated parameters revealed that no single parameter is ideal enough for sepsis identification, and even though blood culture is most commonly used as a diagnostic method for detecting bacteremia, this method is insufficiently sensitive alone. Hence, multiple methods must be used in order to identify the actual source of sepsis.