رسائل ماجيستير
English
2021
Characterization , Antibiofilm and Antibacterial Activity of Biosynthesis AgNPs Against Klebsiella pneumonia Isolated from Clinical Specimens
جاسم محمد باقر حسن علي, وجدان رضا محمود محمد
كلية العلوم-جامعة بابل · العراق
The isolate of Lactobacillus acidophilus was obtained from the Life Sciences Laboratories of the University of Babylon. These isolates were cultured on De Man, Rogosa, and Sharpe (MRS) broth and agar for 24 h at 37°C. Based on microscopy and biochemical tests, these isolates were identified as Lactobacillus acidophilus. The fermentation test for carbohydrates distinguished the Lactobacillus acidophilus isolate, which was further confirmed using biochemical tests and the Vitek2 system.
The method of biosynthesis of nanoparticles is gaining significant attention due to its economic and environmental advantages compared to chemical and physical methods of synthesis. The goal of the current study is the use of Lactobacillus acidophilus to biosynthesize silver nanoparticles (AgNPs). AgNPs were biosynthesized by adding silver nitrate (AgNO3) to the cell-free supernatant of Lactobacillus acidophilus at a concentration of 5 mM as a precursor for the synthesis of AgNPs.
The color change of the solution from yellow to reddish-brown was the first indication of biosynthesis. UV-visible spectrophotometry was used to characterize the biosynthesized nanoparticles, and the maximum absorption peak of the nanoparticles was observed at 420 nm. The size and distribution of nanoparticles were determined using scanning electron microscopy (SEM), revealing circular, homogeneous particles with sizes ranging from 30–100 nm. The elemental composition was investigated using Energy Dispersive X-ray Spectroscopy (EDS), showing silver content at 59.18%.
The antibacterial activity of the biosynthesized AgNPs was evaluated against multidrug-resistant (MDR) bacteria, including both Gram-positive and Gram-negative strains, as well as their ability to inhibit biofilm formation. Between September 2020 and March 2021, a total of 150 clinical isolates of bacteria were collected from different infection sites and from both genders (male and female) attending Marjan Hospital and Al-Sadiq Hospital in Babil Governorate, and the Children’s Hospital and Al-Hussein Medical Hospital in the Holy Governorate.
Out of the 150 clinical isolates, 54 were identified as Klebsiella pneumoniae using the Vitek2 system and biochemical tests. The remaining 96 isolates included other pathogenic bacteria such as E. coli (44 isolates), S. aureus (26 isolates), 18 other bacterial isolates, and 8 isolates showed no growth of pathogenic bacteria. All isolates were obtained from clinical samples of urinary tract infections.
The identification of Klebsiella pneumoniae isolates was confirmed using morphological, cultural, and biochemical tests. The distribution of isolates according to the site of infection was as follows: 30 isolates from urinary tract infections, 18 isolates from wounds, and 6 isolates from ear swabs.
Regarding antibiotic susceptibility testing, all isolates (100%) were resistant to ceftazidime and cefepime, whereas the lowest resistance was observed against minocycline (26.67%) due to the misuse of antibiotics. The study also demonstrated the occurrence of some virulence factors such as the capsule in all isolates (100%) and biofilm formation in 30 isolates. Molecular detection of virulence genes (wbbm and wzm) was performed using conventional PCR techniques.