Is there a community microbial community? A comparison of pathogens between 2 hospital SICUs in a single city

Author(s):
Robert Sawyer; Mikayla Moody

Background:

Nosocomial and healthcare-associated infections drive increased healthcare costs and negatively affect patient outcomes.  The human microbiome has been heavily explored in recent years with incomplete data regarding hospital-specific and community-specific microbial communities.  Although bacterial species differ between intensive care units in the same hospital, it is unclear if they differ between similar units in similar hospitals in the same community.

Hypothesis:

Our hypothesis is that pathogens in surgical intensive care units are distinct between hospitals, even in the same community.

Methods:

From 2017-2021, data were prospectively collected from the SICUs of two 500 bed hospitals located 3 miles apart in the same city (Hospital A and Hospital B).  Infections defined using CDC criteria were recorded for trauma and general surgery patients, as well as patient demographics, APACHE II score, and causative organism.  Means were then compared using the Student t-test, and proportions were compared with Chi-square or Fisher’s exact test.

Results:

Results: Overall, Escherichia coliwas the most commonly isolated pathogen in Hospital A, while Staphylococcus aureuswas most commonly isolated at hospital B (Table, * = p ≤ 0.05 between hospitals).  Enterococci were more common in Hospital A, and Haemophilus influenzae and Enterobacterspp. were more common in Hospital B.  After stratification between trauma and non-trauma patients, however, these differences disappeared, with the exception of more overall Gram-positive organisms and fewer Gram-negative organisms among Hospital A trauma patients compared to Hospital B.  There were no differences in rates of isolation of either fungi or resistant bacteria between hospitals.  APACHE II scores were also similar when stratified by diagnosis.

Conclusions:

Conclusion: At a species level, admission diagnosis appears to be a greater determinant of pathogen isolation than hospital when comparing similar intensive care units, but a larger body of data is needed to flesh out a distinct microbial map of the organisms occupying a certain geographic region.  Further areas for investigation include comparison between hospital units, specific anatomic sites, and ICU versus floor patients.