[The composition and antimicrobial resistance of isolates from lower respiratory tract and blood in hospitalized patients in respiratory ward: a multicenter national study in China].

Objective: To investigate the species and antimicrobial resistance of bacterial pathogens isolated from hospitalized patients in respiratory ward in China.
Methods: This was a multicenter retrospective study based on a national epidemiological network called China Antimicrobial Resistance Surveillance System (CARSS). The non-repetitive strains isolated from lower respiratory tract and blood samples in 91 hospitals from seven geographic regions of CARSS were reviewed. The distribution of specimen type, hospital level (secondary and tertiary hospital), patient age group [geriatric (>65 years old), adult (15 to 65 years old), pediatric (28 days to 14 years old ) and newborn group (≤28 days)] and ward type (respiratory intensive care unit and general respiratory ward) were analyzed for MRSA, PRSP, CREC, CRKP, CRPA, CRAB, ESBL-EC and ESBL-KP. The categorical variables were analyzed by chi-square test using SPSS 16.0 statistical software. P<0.05 was regarded as statistically significant.
Results: A total of 50 417 non-repetitive isolates [42 751 isolates from lower respiratory tract (LRT), 2 649 isolates from blood and 5 017 isolates from other samples (urine and secretions)] from 48 752 inpatients (without illness type information) were enrolled in the study. 90.2% (45 491/50 417) isolates were obtained from 63 tertiary hospitals. According to patients' age, all cases were divided into 4 groups, i. e. geriatric(46.0%, 23 177/50 417), adult(29.9%, 15 092/50 417), pediatric(24.0%, 12 112/50 417) and newborn group(0.0%, 36/50 417). All isolates were obtained from respiratory intensive care unit (6.2%, 3 129/50 417) or general respiratory wards (93.8%, 47 288/50 417). The majority of bacterial pathogens were isolated from lower respiratory and blood culture samples, which accounted for 90.0% of all the samples (45 400/50 417). Sputum accounted for 81.6% (41 131/50 417) of samples, and the leading 4 isolates were K. pneumonia (18.9%, 7 784/41 131), P. aeruginosa (13.6%, 5 580/41 131), A. baumanni (11.3%, 4 644/41 131) and S. pneumonia (11.1%, 4 564/41 131). Blood samples accounted for 5.3% (2 649/50 417) of the samples, with the leading 4 bacteria being coagulase-negative staphylococcus (42.0%, 1 112/2 649), E. coli (18.3%, 484/2 649), K. pneumonia (7.4%, 194/2 649) and S. aureus (4.9%, 131/2 649). The species distribution of pathogens isolated from bronchoalveolar lavage fluid (BALF), which accounted for 3.2% (1 620/50 417) of the samples, was similar to that of sputum, and the leading 4 bacteria were P. aeruginosa (22.0%, 360/1 620), K. pneumonia (14.8%, 239/1 620), A. baumanni (11.9%, 193/1 620) and S. pneumonia (9.6%, 155/1 620). The prevalence of CRKP, CRPA and CRAB in tertiary hospitals [5.2% (384/7 439), 23.8% (1 260/5 304) and 53.5% (2 259/4 224), respectively] was significantly higher than that in secondary hospitals [2.5% (24/973), 12.8% (101/787) and 33.9% (109/322), respectively] (all P<0.01). In comparison, the prevalence of ESBL-EC in secondary hospitals (63.9%, 145/227) was higher than that in tertiary ones (55.0%, 1 141/2 074) (P=0.011). The prevalence of ESBL-EC and ESBL-KP in pediatric group [68.2% (283/415) and 55.3% (183/331), respectively] was higher than that in geriatric group [54.2% (684/1 263) and 27.1% (625/2 303), respectively] and adult group [51.1% (317/620) and 15.1% (272/1 804), respectively] (all P<0.001). Conclusions: In China, the predominant bacterial pathogens in the respiratory wards were Enterobacteriaceae and non-fermentative bacteria. High prevalence of ESBL-EC and ESBL-KP isolated from lower repiratory tract was revealed in primary hospitals and pediatric patients.