In Vitro Activity of Retapamulin and Antimicrobial Susceptibility Patterns in a Longitudinal Collection of Methicillin-Resistant Staphylococcus aureus Isolates from a Veterans Affairs Medical Center

Abstract

bMupirocin is a topical antimicrobial used to decolonize patients who carry methicillin-resistant Staphylococcus aureus (MRSA), and the topical agent retapamulin may be a potential alternative therapy. The goal of this study was to determine the in vitro activity of retapamulin as well as a panel of 15 antimicrobial agents, including mupirocin, for 403 MRSA isolates collected longitudinally from a naive population at the Veterans Affairs Puget Sound Health Care System. The MICs for retapamulin had a unimodal distribution, ranging from 0.008 to 0.5 g/ml. One isolate had an MIC of >16 g/ml, was also resistant to clindamycin and erythromycin, and was recovered from the nares of a patient undergoing hemodialysis. Twenty-four isolates (6%) and 11 isolates (3%) demonstrated low-level resistance (MICs of 8 to 64 g/ml) and high-level resistance (MICs of >512 g/ml), respectively, to mupirocin. Isolates were recovered from 10 patients both before and after mupirocin therapy. Of those, isolates from 2 patients demonstrated MIC changes postmupirocin therapy; in both cases, however, strain typing demonstrated that the preand postmupirocin strains were different. A total of 386 isolates (96%) had vancomycin MICs of <1.0 g/ml; 340 isolates (84%) were resistant to levofloxacin, 18 isolates (4.5%) were resistant to trimethoprim-sulfamethoxazole, and 135 isolates (33%) had elevated MICs of 4 g/ml for linezolid. The baseline levels of resistance were low for mupirocin (9%) and even lower for retapamulin (0.25%) Although the use of mupirocin is currently the standard therapy for decolonization practices, the activity of retapamulin warrants its consideration as an alternative therapy in MRSA decolonization regimens.

Prevalence and molecular characterization of methicillin-resistant Staphylococcus aureus with mupirocin, fusidic acid and/or retapamulin resistance

“…Currently, limited data are available among clinical S. aureus strains worldwide. The resistance rates of 664 UK S. aureus (74% are MRSA), 155 USA MRSA, 403 USA MRSA, and 400 USA S. aureus from several studies were 0.15, 2.6, 0.25, and 9.5%, respectively [8,[29][30][31]. In this study, the prevalence of RET resistance was very low (3/1206, 0.24%).…”

“…RET is a semisynthetic pleuromutilin drug that represses the synthesis of bacterial proteins by interacting with domain V of 50S ribosomal subunit [3]. This drug has a potency to act as an alternative to MUP to eradicate the S. aureus colonization, except when used for the treatment of S. aureus-induced SSTIs [8,29]. Currently, limited data are available among clinical S. aureus strains worldwide.…”

Prevalence and molecular characterization of methicillin-resistant Staphylococcus aureus with mupirocin, fusidic acid and/or retapamulin resistance

“…For RET resistance, very little published data are available among clinical S. aureus strains worldwide. The resistance rates of 664 UK S. aureus (74% of them were MRSA), 155 USA MRSA, 403 USA MRSA and 400 USA S. aureus from several different studies were 0.15%, 2.6%, 0.25%, and 9.5%, respectively [8,[35][36][37]. In this study, the prevalence of RET resistance was very low (0.24%, 3/1226).…”

“…Retapamulin, a semisynthetic drug, represses the synthesis of bacterial proteins by interacting with domain V of 50S ribosomal subunit [3]. This drug has a potency to act as an alternative to MUP to eradicate the S. aureus colonization, except used for the treatment of SSTIs of S. aureus [8,35]. For RET resistance, very little published data are available among clinical S. aureus strains worldwide.…”

An Open Label, Multi-Center, Non-Interventional Post-Marketing Surveillance to Monitor the Safety and Efficacy of ALTARGO® (Retapamulin) Administered in Korean Patients According to the Prescribing Information

“…And there was another similar report about retapamulin and its antimicrobial susceptibility patterns. Researchers in USA also proposed that although the use of mupirocin has been the standard therapy for decolonization practices as of now, the activity of retapamulin could warrant its consideration as an alternative therapy in MRSA decolonization regimens 25 .…”