Our study describes the baseline characteristics, clinical features, microbiological data, and outcomes of patients hospitalized with IE in a public hospital of the city of New York in the past decade. This is the first study evaluating the epidemiology of IE in the Bronx, New York. The main findings can be summarized as following: 1) S. aureus followed by streptococci and enterococci were the most common identified pathogens, 2) MRSA accounted for about half of the S. aureus IE cases, 3) the incidence of IE in patients with IVDU increased over time and the median age decreased, 4) The overall in-hospital mortality was 18.1% and was higher in 2010–2015 compared to 2016–2020, and 5) MRSA IE were found to be associated with a higher likelihood for in-hospital death.
S. aureus was the most common microbe identified in our population accounting for about 45% of cases. Similarly, S. aureus was the most prevalent pathogen in recent cohorts of patients with IE in Australia (45–53%)[34–36], Israel (33.3%) [37], Norway (31.4%) [38], Japan (27.2%) [39], Italy (27%) [40], and Taiwan (25.7%) [41]. On the other hand, recent observational studies from low- and middle-income countries demonstrated lower prevalence of S. aureus and revealed that streptococci largely remain the most common causative agents in these regions [21, 42–45]. The existing literature has repeatedly demonstrated increasing prevalence of staphylococcal IE particularly in the western world [6, 11, 34, 46–49]. Increased use of central venous catheters, prosthetic valves, and cardiac devices, along with the performance of higher number of invasive procedures than before seem to be responsible for this change in the epidemiology of the disease over time [14, 50]. It should be emphasized that patients with S. aureus IE are more likely to require longer hospitalization, surgical treatment and are associated with higher likelihood for large vegetations, prosthetic valve involvement, abscess, recurrence, readmission, and in-hospital death [44, 51–56].
MRSA accounted for about half of the S. aureus cases in our cohort. Although S. aureus has a well-known propensity to develop resistance to methicillin and MRSA strains have been a universally recognized problem [57, 58], such a high prevalence of MRSA IE is deeply concerning. Recent observational studies from four different continents demonstrated that MRSA accounted for 19–40.9% of S. aureus IE and bacteremia cases [39, 59–61] which is significantly lower compared to our findings. The high rates of IVDU (25.3%), recent hospitalization (29.1%), and SNF residence (16%) in our population are the most likely explanations of higher MRSA IE rates since all these characteristics are known risk factors for MRSA infections [62–65].
Several differences were observed comparing the early cohort (2010–2015) to the late cohort (2016–2020). Most notably, the rate of patients with IVDU was more than double in 2016–2020 compared to 2010–2015. This remarkable difference likely drove the other observed differences, namely higher median age and prevalence of chronic diseases in 2010–2015 and significantly higher rates of right-sided and multivalvular IE in 2016–2020[27, 66–68]. It is likely that the US opioid epidemic [69, 70], which peaked in the middle of the past decade, is associated with this epidemiological and clinical shift. Similar trends over time have been observed across the country [71] and Sweden [66].
The overall in-hospital mortality was 18.1% in our study, which is in line with the high in-hospital death rates observed in other recent cohorts and indicates that IE remains a life-threatening condition requiring immediate and special attention [4, 39, 45, 72–75]. A significant decrease in the in-hospital mortality from 22.1–14.6% was noted comparing 2010–2015 to 2016–2020, which can be explained at least partially by the higher representation of patients with IVDU in the late cohort, who typically are of younger age and have less comorbidities [71, 76, 77]. MRSA IE was the only predictor of higher likelihood for in-hospital death identified in the multivariate analysis. The latter finding is in accordance with the results of a large systematic review that included 17,563 patients and showed that MRSA IE was associated with a 95% higher likelihood for death compared to MSSA IE [29].
One of the key strengths of the current study is that the study population represents underserved and economically disadvantaged minorities; thus, revealing the epidemiologic characteristics and outcomes of infective endocarditis in this usually underreported and underrepresented population in clinical research. Moreover, we report our findings on the epidemiology and outcomes of infective endocarditis in the Bronx, where there is a paucity of relevant data. Additionally, two pairs of researchers independently and blindly collected data which reduces errors and bias. On the other hand, our study has several limitations. First, this is a single-center study performed in a hospital that does not have significant cardiac surgery capabilities, therefore our findings cannot be easily generalized and the outcomes could have been affected by this limitation. Second, the relatively low rates of performed TEE might have posed diagnostic limitations and affected the in-hospital outcomes. Third, this was a real-world study with a retrospective design utilizing the electronic medical records, which is suboptimal compared to a prospective study that would allow for a more accurate follow-up assessment and would additionally provide information on long-term outcomes.
In conclusion, in this cohort of patients hospitalized with IE in the past decade in a public hospital in the Bronx, New York, we found that S. aureus was the most common causative agent and MRSA accounted for nearly half of the S. aureus IE cases. The incidence of IE in patients with IVDU increased over time, while the median age decreased. The in-hospital death rate was higher in 2010–2015 compared to 2016–2020. MRSA IE was found to be associated with a higher likelihood for in-hospital death. Data from more local institutions are needed to better characterize the changing epidemiology of IE at a regional level and tailor our preventative and therapeutic approaches accordingly.