In vitro activity and clinical efficacy of macrolides, cefoperazone-sulbactam and piperacillin/piperacillin-tazobactam against Bordetella pertussis and the clinical manifestations in pertussis patients due to these isolates：A single-center study in Zhejiang Province, China.

BACKGROUND AND OBJECTIVE: Macrolides are the recommended antibiotics for treating pertussis and preventing transmission. The causative bacterium, Bordetella pertussis, has high macrolide resistance and has recently circulated in China. The objective of the study was to find effective alternative antibiotics in therapy by assessing the in vitro activity and clinical efficacy of antibiotics against Bordetella pertussis.

METHODS: Bordetella pertussis was confirmed by agglutination with specific antisera and mass spectrometry. The minimal inhibitory concentrations (MICs) of antibiotics against isolates were determined using E-test method. Treatment outcomes were evaluated clinically and microbiologically.

RESULTS: Here, 126 pertussis patients were diagnosed based on culture, 69.8% of whom were ≤6 months old and 72.1% were treated with previous macrolides. Leukocytosis and lymphocytosis were observed in 29.4% and 54.8% of all patients respectively. Both MIC50 and MIC90 of erythromycin, azithromycin, and clindamycin were >256 mg/L, and 75.4% were highly macrolide-resistant. MIC90 of trimethoprim-sulfamethoxazole, ampicillin, ampicillin-sulbactam, cefuroxime, ceftriaxone and cefoperazone-sulbactam, were 0.38 mg/L, 0.25 mg/L, 0.19 mg/L, 12 mg/L, 0.19 mg/L and 0.047 mg/L, respectively. MICs of piperacillin in all of the isolations were <0.016 mg/L. Of the patients treated with single cefoperazone-sulbactam or piperacillin-tazobactam, 93.8% (30/32) had significant improved clinical symptoms and 96% (24/25) had negative culture results after 2 weeks of therapy.

CONCLUSION: Macrolide resistance in Bordetella pertussis is a serious problem in Zhejiang Province. Piperacillin/piperacillin-tazobactam and cefoperazone-sulbactam, have potent antibacterial activity in vitro and in vivo andmay become the alternative choice for treating pertussis caused by macrolide-resistant isolates.