Combination therapy with ampicillin and azithromycin in an experimental pneumococcal pneumonia is bactericidal and effective in down regulating inflammation in mice

Objectives

Emergence of multidrug resistance among Streptococcus pneumoniae (SP), has limited the available options used to treat infections caused by this organism. The objective of this study was to compare the role of monotherapy and combination therapy with ampicillin (AMP) and azithromycin (AZM) in eradicating bacterial burden and down regulating lung inflammation in a murine experimental pneumococcal infection model.

Methods

Balb/C mice were infected with 10⁶ CFU of SP. Treatments with intravenous ampicillin (200 mg/kg) and azithromycin (50 mg/kg) either alone or in combination was initiated 18 h post infection, animals were sacrificed from 0 – 6 h after initiation of treatment. AMP and AZM were quantified in serum by microbiological assay. Levels of TNF-α, IFN-γ IL-6, and IL-10 in serum and in lungs, along with myeloperoxidase, inflammatory cell count in broncho alveolar lavage fluid, COX-2 and histopathological changes in lungs were estimated.

Results

Combination therapy down regulated lung inflammation and accelerated bacterial clearance. This approach also significantly decreased TNF-α, IFN-γ, IL-6 and increased IL-10 level in serum and lungs along with decreased myeloperoxidase, pulmonary vascular permeability, inflammatory cell numbers and COX-2 levels in lungs.

Conclusions

Combinatorial therapy resulted in comparable bactericidal activity against the multi-drug resistant isolate and may represent an alternative dosing strategy, which may help to alleviate problems with pneumococcal pneumonia.

Azithromycin-resistant Neisseria gonorrhoeae strains recently isolated in Italy

OBJECTIVES

The aim of this study was to characterize 22 azithromycin-resistant Neisseria gonorrhoeae isolates, collected in Italy from January 2007 through June 2008, during a study of the prevalence of antibiotic resistance.

METHODS

MICs of azithromycin, ciprofloxacin, ceftriaxone, penicillin and tetracycline were determined by the Etest method. Azithromycin-resistant strains (MIC > or = 1 mg/L) were genetically analysed by N. gonorrhoeae multi-antigen sequence typing (NG-MAST) and PFGE.

RESULTS

A total of 22 azithromycin-resistant isolates were found among the 219 collected. Five of the 22 isolates showed high-level azithromycin resistance (MICs of 128 or 256 mg/L). Sixteen of the 22 were isolated from men who have sex with men. Among the 14 sequence types (STs) found by NG-MAST, 5 STs, containing clusters of two, three or four strains, were homogeneous with respect to epidemiology and/or antibiotic susceptibility. PFGE divided the 22 strains into two main groups that were possibly related.

CONCLUSIONS

This is the first report of gonococci with high-level resistance to azithromycin circulating in Italy. Correlation between NG-MAST results and epidemiological data for some of the analysed strains and patients could be established. This study represents a reference point for future surveillance in Italy and suggests the need to add azithromycin to the antibiotic susceptibility panel for gonococci.