Abstract: Objective The study aims to evaluate the incidence and microbiology of infectious complications (namely meningitis and/or bacteremia) after trans-sphenoidal pituitary adenomectomies (TSPA). Methods All hospitalized patients undergoing TSPA in Dept. Neurosurgery of Peking Union Medical College Hospital (PUMC) between January 2012 and December 2016 were retrospective recorded. Results The overall incidence of postoperative meningitis and/or bacteremia was 1.2% (59/5 098). 27 cases of meningitis were documented for a total of 41 isolates, 26 cases of bacteremia for 34 isolates , and 6 cases of coinfection. Gram-positive organisms predominated (27 cases , 65.9%) in meningitis, among which Coagulase-negative staphylococci were the main isolates (14 cases). The most common organisms causing bacteremia were Gram-negative organisms (25case，73.5%), including Klebsiella pneumonia (9 cases), Enterobacter aerogenes (7 cases) and Escherichia coli (5 cases), all of which were sensitive to amikacin, imipenem and meropenem. Fifty-two patients were cured after antibiotic treatment, whereas 7 died. The morality in patients with meningitis was relatively lower than those with bacteremia (21.2% vs. 3.1%，P＜0.001). Conclusions Postoperative meningitis and/or bacteremia can occur after TSPA. They differ in microbiology and prognosis, and should be treated with proper antibiotics according to the drug resistance.

Key words: Key words: TSPA, meningitis, bacteremia, pathogens