[Analysis of microbiology and antibiotic susceptibility in 131 cases of prosthetic hip infections].

OBJECTIVE: To explore the microbiological etiology of prosthetic hip infections during two-staged revision and analyze antibiotic susceptibility of bacteria isolated from infected hip arthroplasty specimens so as to provide clinical recommendations for empiric prophylactic and therapeutic antibiotics therapy.

METHODS: A retrospective review was conducted for hospitalized patients of prothetic hip infections during two-staged revision between January 1, 2007 and December 31, 2013. Suspicious intraoperative tissues were cultured and microbiological data sets and antibiotic susceptibility of bacteria were analyzed.

RESULTS: A total of 131 patients met the inclusion criteria. Micro-organisms were isolated in 96 patients. The negative culture rate was 26.7%. Nearly half of primary diseases were of fractures and 31.29% of all infected patients had previous surgery. Gram-positive isolates were the most common genus encountered (n = 81, 74.3%), followed by Gram-negative isolates (n = 22, 20.2%) and fungal isolates (n = 6, 5.5%). Polymicrobial infections accounted for 11.5%. Coagulase-negative staphylococci was the most common causative organism of infection (n = 42, 38.5%), followed by Staphylococcus aureus (19.3%). The proportion of isolated methicillin-resistant Staphylococcus was 29.36% for all organisms and 44.4% for Staphylococcus. Gram-negative isolates were dominated by Pseudomonas aeruginosa and Escherichia coli. Fungal isolates were dominated by Candida albicans. Enterococcus was the most common causative organism of polymicrobialinfection. The results of antibiotic susceptibility showed cefazolin and cefuroxime were poorly susceptible to coagulase negative staphylococci (CNS) and methicillin-resistant staphylococcus (MRS). Some third and fourth-generation cephalosporins also had problems of bacterial resistance to Gram-negative isolates. Some antibiotics such as vancomycin, linezolid and rifampin were sensitive to Gram-positive isolates. Some antibiotics such as amikacin piperacillin/tazobactam, cefoperazone/sulbactam, levofloxacinareand carbapenems were sensitive to Gram-negative isolates.

CONCLUSION: Most infections are caused by staphylococci. The proportion of isolated methicillin-resistant Staphylococcus is high. Empiric antibiotics should include vancomycin for Gram-positive organisms and piperacillin/tazobactam (cefoperazone/sulbactam), levofloxacinare or carbapenems for most Gram-negative bacteria. Antibiotics should be timely adjusted according to the antibiotic susceptibility results.