4 DISCUSSION AND CONCLUSION
This retrospective study of 82 elderly patients with bacteremia, compared with a control group of 69 patients, identified E. coli, K. pneumoniae, and streptococcus as the most prevalent gram-negative bacteria. These findings align with prior research conducted by Guarno et al. [7]. Similarly, an investigation by Daniela Dambroso et al. [8]indicated that 47.7% of bloodstream infections were due to Gram-positive bacteria and 52.3% to Gram-negative bacteria, with the Enterobacteriaceae family, particularly E. coli (26.5%) andK. pneumoniae (19.7%), being the most prevalent. Further support for these results was offered by a study conducted in Japan[9], which identified E. coli (28/58, 48%) as the leading causative bacteremia pathogen, followed by K. pneumoniae (6/58, 10%), and Staphylococcus (5/58, 8%).
Our research also revealed a significant predominance of gram-negative bacteria in elderly female patients with bacteremia (74.4%), compared to their male counterparts (25.6%) (P = 0.021) (Table 5). Interestingly, a higher positivity rate for E. coli was found in the female patient population, making E. coli the most common bacteremia pathogen among this demographic. This is in alignment with existing literature that identifies E. coli as a predominant human pathogen with the capability to colonize, infect, and invade various human tissues, leading to severe E. coli disorders and potential mortality [10]. E. coli is the leading cause of bacteremia among adults in the world and is the common frequent of sepsis and subsequent hospitalization or deaths in the United States[11]. The risk of invasive E. coli infections, which consisted of sepsis and bacteremia, and increased with the growth of the age [12].
The comparative evaluation of blood cell parameters in our study revealed a statistically significant increase in leukocyte count, NLR, PLR, and RDW among bacteremia patients. From the ROC curves, NLR emerged as the most effective predictor of bacteremia in geriatric patients. While the total white blood cell count is traditionally used as an indicator of bacterial infection, its efficacy is limited by the influence of other conditions such as hematological diseases, non-infectious inflammatory diseases, surgery, and trauma[13]. In our study, the sensitivity and specificity of WBC in diagnosing bacteremia in elderly patients were determined to be 74.4% and 87.0%, respectively. RDW, a measure of the variation in red blood cell volume size, is primarily used for diagnosing anemia. Elevated RDW may reflect better residual bone marrow hematopoiesis during severe anemia [14]. In conditions such as sepsis, oxidative stress and inflammation can disrupt erythrocyte maturation, leading to an increased RDW[15]. A previous study by Professor Dogan P et al. showed that an RDW cut-off of >19.50% was associated with a sensitivity of 87% and a specificity of 81% for predicting late-onset Gram-negative sepsis (P < 0.001)[16]. In our study, the diagnostic value of RDW demonstrated an RDW cut-off of >13.0% with the sensitivity of 78.0% and the specificity of 52.2% for predicting bacteremia. The difference in the results of the two investigations were mainly due to the difference in the enrolled subjects.
Finally, our study underscores the value of NLR as a reliable indicator of systemic inflammatory response, which has potential predictive value for bacteremia. While NLR can be influenced by several factors, including age, obesity, and various diseases [5], its efficacy in diagnosing bacteremia is supported by several studies, including our own.
The insights provided by this study make a compelling case for utilizing these routine blood parameters as cost-effective, straightforward, and rapid indicators for bacteremia in the elderly. However, it’s important to acknowledge the study’s limitations. Our focus was on bacterial pathogens, excluding others such as fungi, mycoplasma, chlamydia, parasites, and viruses. Moreover, the single-center nature of the study limits the generalizability of our findings. Future studies should aim for a multi-center approach with larger sample sizes to provide a more comprehensive understanding of geriatric bacteremia infections. These studies should also further investigate the distribution of microorganisms and the predictive value of routine.