Data collection
Patient data were extracted from electronic medical records. Data on
patient characteristics such as age, sex, location of residence,
underlying comorbidities, body mass index (BMI), A-DROP score, GNRI
score, and laboratory test results were collected. The A-DROP scoring
system proposed by the Japan Respiratory Society was employed to assess
disease severity. The A-DROP score consists of the following items: age
≥70 years for male individuals and ≥75 years for female individuals,
blood urea nitrogen (BUN) ≥21 mg/dL or dehydration, oxyhemoglobin
saturation measured using pulse oximetry ≤90% or partial pressure of
oxygen in arterial blood ≤60 mmHg, confusion, and systolic blood
pressure ≤90 mmHg. Depending on the number of corresponding items, 0
points was defined as mild, 1–2 points as moderate, 3 points as severe,
and 4–5 points as most severe.18 Sputum samples were
collected at admission to identify causative pathogens of aspiration
pneumonia. They were obtained by expectoration or catheter suction and
then cultured. We defined methicillin-resistant Staphylococcus
aureus , Pseudomonas aeruginosa , Acinetobacter baumannii ,Stenotrophomonas maltophilia , and extended-spectrum
β-lactamase-producing gram-negative bacilli as potential drug-resistant
(PDR) pathogens. GNRI was calculated as follows: (14.89 × serum albumin
[g/dL]) + (41.7 × [actual body weight/ideal body weight]). Ideal
body weight was calculated as: height (cm) – 100 – ([height –
150]/4) for men and height (cm) – 100 – ([height – 150)/2.5]
for women. Nutritional risk was determined using GNRI scores, wherein
GNRI < 82, 82 ≤ GNRI < 92, 92 ≤ GNRI < 98,
and GNRI ≥ 98 indicated severe, moderate, mild, and no risk,
respectively.10 We collected data regarding initial
antibiotic agents, days of administration, and switching of the initial
drug to a different drug. Data on clinical course and outcomes included
length of stay (LOS) and in-hospital mortality. The study endpoint was
defined as in-hospital mortality. Patients who were discharged were
defined as the “survivor group” and those who died during
hospitalization were defined as the “non-survivor group.” Patient
characteristics, microbiological findings, and clinical course were
compared between survivor and non-survivor groups.