Colonization metrics by pathogen.

Nursing home acquired pneumonia (NHAP), and its subset – aspiration-associated pneumonia, is a leading cause of morbidity and mortality among residents in long-term care facilities (LTCFs). Understanding colonization dynamics of respiratory pathogens in LTCF residents is essential for effective infection control. This study examines the longitudinal trends in prevalence, persistence, bacterial load, and co-colonization patterns of five respiratory pathogens in three LTCFs in Phoenix, Arizona. Anterior nares and oral swabs were collected every other week and tested using qPCR for Haemophilus influenzae, Pseudomonas aeruginosa, Streptococcus pneumoniae, Staphylococcus aureus, and Chlamydia pneumoniae. Weekly average positivity rates were 17.75% for H. influenzae (0% – 39.39%), 9.95% for P. aeruginosa (0% – 37.74%), 31.89% for S. pneumoniae (1.79% – 41.67%), and for 28.00% for S. aureus (0% – 55.36%). C. pneumoniae was not detected. H. influenzae and S. pneumoniae predominantly colonized the oral cavity, while P. aeruginosa and S. aureus predominantly colonized the nasal cavity. Colonization by S. pneumoniae and S. aureus was significantly more persistent than H. influenzae and P. aeruginosa, with persistence correlating with significantly higher bacterial loads. Co-colonization did occur in ~20% of positive samples but appeared to be due to random chance. This study reveals distinct colonization patterns among respiratory pathogens in LTCF residents, highlighting differences in site-specific prevalence, persistence, and bacterial load. These findings underscore the importance of longitudinal monitoring to inform targeted infection control strategies in LTCFs.