P-577. Clinical Predictors of Mortality in Hospitalized Patients with Rickettsioses in Northern Mexico

Abstract Background Rickettsioses are life-threatening vector-borne infections1. Clinical manifestations are nonspecific, commonly including fever, malaise, and an exanthematous rash, necessitating a high index of suspicion for timely diagnosis. Without appropriate treatment, mortality can reach 100%2. Methods From October 2022 to April 2025, we conducted a prospective study of patients with qPCR-confirmed rickettsioses at a tertiary teaching hospital in Monterrey, Mexico. Data were analyzed using SPSS v19. We applied Student’s t-test and chi-square test for group comparisons and calculated relative risks (RR). Results A total of 49 patients were included, with a median age of 15 years (range 9-32 years), and 52% were males. Thirty patients (60%) died during hospitalization. The media time-to-treatment from hospital admission was 5.15 hours. All patients received doxycycline. Some patients received antibiotics prior to admission, including ceftriaxone and amoxicillin/clavulanic acid; only three received doxycycline. The median number of medical visits before diagnosis was 1 day (range 1-2) Symptom duration before admission had a median of 5 days (range 4-7). Fever (98%) and petechial rash (42%) were the most common clinical signs shown in Table 1, while thrombocytopenia was present in 98% of patients. Factors associated with increased mortality were thrombocytopenia RR 4 (95% CI 1.12-14.25) p = 0.03, elevated lactate RR 3.28 (95% CI 1.19.9.95) p = 0.02, increased creatinine RR 2.26 (95% CI 1.2-4.25) p = 0.01 and aspartate aminotransferase (AST) levels RR 2.33 (95% CI 1-5.43) p = 0.03, as shown in Table 3. Conclusion Rickettsioses are a critical illness associated with high mortality. In our cohort, fever was a common presenting symptom, while rash was observed in fewer than half of the patients; notably, 98% of the patients presented with thrombocytopenia. Elevated lactate levels, acute kidney injury, and thrombocytopenia at admission were significant predictors of mortality. Disclosures All Authors: No reported disclosures