الفهرس 
Chapter 1: EnterobacteriaceaeOnly 14 pages are availabe for public view
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Abstract
Hospital-acquired infections (HAIs) pose a significant threat to public health, leading to increased illness, mortality, and healthcare costs. Annually, approximately 1.7 million individuals suffer from HAIs, with a mortality rate of around 6%. Compounding this issue is the prevalence of antibiotic resistance, which often accompanies these infections, making treatment more challenging and expensive (Ali et al., 2018 & Dayyab et al., 2018).
The irresponsible use of antibiotics and the absence of antibiotic stewardship programs have worsened the global threat of antibiotic resistance. One of the most concerning resistance mechanisms is the emergence of carbapenem resistance (CR) within the Enterobacteriaceae family. Although carbapenem resistance has been observed in Enterobacteriaceae for the past two decades, its recent escalation into a global health issue is alarming. CR has been increasingly disseminated among various members of Enterobacteriaceae, notably E. coli and K. pneumoniae, across different regions worldwide (Aslam et al., 2019).
Colistin, a last-resort treatment option for multidrug-resistant bacterial infections, including extensively drug-resistant (XDR) carbapenem-resistant Enterobacteriaceae (CRE), is facing significant challenges due to its widespread use. The rise in reports of colistin resistance among CRE isolates is progressively creating additional obstacles in managing these infections (Dickstein et al., 2019 & Kang et al., 2019).
The objectives of this study were to determine the prevalence of Enterobacteriaceae isolates from patients with HAIs at Menoufia University Hospitals (MUHs), identify the most common species, and assess their antimicrobial susceptibility patterns. Additionally, the study aimed to investigate the prevalence of carbapenem and colistin resistance among the isolated Enterobacteriaceae species and confirm the contributing mechanisms using both phenotypic and genotypic methods. The presence of the entB virulence gene, a genetic determinant of siderophore metabolism, was also verified among the isolated Enterobacteriaceae species using multiplex PCR assay.
This study was conducted at the Medical Microbiology and Immunology Department, Faculty of Medicine, Menoufia University, from March 2021 to August 2022. The study included 360 patients (177 males and 183 females) ranging in age from 1 month to 75 years, with a mean age of 41.4 ± 24.2 years. These patients were presented with various types of HAIs that developed at least 48 hours after admission, such as respiratory tract infections, urinary tract infections, wound infections, burn infections, and bacteremia. The study protocol was approved by the local ethics committee of Menoufia University, and informed consent was obtained from each patient or their guardians if the patients were unaware.
Different clinical specimens (n=400) were collected from the study participants based on the type of infection, including urine (125 samples), blood (79 samples), pus (59 samples), sputum (51 samples), bronchial aspirate (43 samples), and burn swabs (43 samples). These samples were processed using standard microbiological methods to isolate and identify the causative organisms. A total of 160 Enterobacteriaceae isolates were obtained, with K. pneumoniae being the most frequently isolated bacillus (72/160; 45%) among the Enterobacteriaceae family, followed by E. coli (46/160; 28.75%), E. aerogenes (26/160; 16.25%), and P. mirabilis (16/160; 10%). The identified isolates were preserved in tryptic soy broth and 16% glycerol, frozen at -80°C, and characterized for different resistance and virulence mechanisms using both phenotypic and molecular methods.
Enterobacteriaceae species were frequently isolated from various clinical specimens, with the highest rates observed in sputum (57.1%), urine (52.5%), bronchial aspirate (46.5%), wound specimens (41%), blood (25%), and burn swabs (16.7%). Among the hospital departments, Enterobacteriaceae isolates were most frequently isolated from ICUs (36.3% or 58/160), followed by Urology (14.4%), Surgery and Pediatrics (13.1% each), Oncology (8.1%), Internal Medicine (6.9%), Burn Unit (4.4%), and Chest (3.8%).
The highest rate of Enterobacteriaceae isolation was observed in patients aged 18-60 years (38.1%), males (50.6%), those with low socioeconomic status (66.9%), rural residents (51.9%), and non-smokers (56.9%). A statistically significant difference was found in the distribution of Enterobacteriaceae isolates among different age groups (p<0.05), with higher rates observed in the 18-60 age group compared to children and the elderly.