MRSA decolonization failure—are biofilms the missing link?

Abstract

BackgroundDevice-associated infections due to biofilm-producing methicillin-resistant Staphylococcus aureus (MRSA) have been recently associated with the failure of antibiotic treatment and decolonization measures. The goal of our study was to evaluate the extent to which the formation of biofilms influenced the efficacy of topical decolonization agents or disinfectants such as mupirocin (MUP), octenidine (OCT), chlorhexidine (CHG), polyhexanide (POL), and chloroxylenol (CLO).MethodsBacterial killing in biofilms by the disinfectants and MUP was determined as the reduction [%] in metabolic activity determined by a biofilm viability assay that uses kinetic analysis of metabolic activity. The test substances were diluted in water with standardized hardness (WSH) at 25 °C at the standard concentration as well as half the standard concentration to demonstrate the dilution effects in a practical setting. The tested concentrations were: CHG 1%, 2%; OCT 0.1%, 0.05%; PH 0.04%, 0.02%; and CLO 0.12%, 0.24%. A test organism suspension, 1 mL containing ~1 × 109 bacterial cells/mL, and 1 mL of sterile WSH were mixed and incubated for six different exposure times (15 s, 1, 3, 5, 10 and 20 min) after the test substance was added.Additionally, the bactericidal effects of all substances were tested on planktonic bacteria and measured as the log10 reduction.ResultsThe disinfectants OCT and CHG showed good efficacy in inhibiting MRSA in biofilms with reduction rates of 94 ± 1% and 91 ± 1%, respectively. POL, on the other hand, had a maximum efficacy of only 81 ± 7%. Compared to the tested disinfectants, MUP showed a significantly lower efficacy with <20% inhibition (p < .05). Bactericidal effects were the greatest for CHG (log10 reduction of 9.0), followed by OCT (7.7), POL (5.1), and CLO (6.8). MUP, however, showed a very low bactericidal effect of only 2.1. Even when the exposure time was increased to 24 h, 2% MUP did not show sufficient bactericidal effect.ConclusionsOur data provide evidence that OCT and CHG are effective components for disinfection of MRSA-biofilms. On the other hand, exposure to MUP at the standard concentrations in topical preparations did not effectively inhibit MRSA-biofilms and also did not show adequate bactericidal effects. Combining an MUP-based decolonization regimen with a disinfectant such as OCT or CHG could decrease decolonization failure.

Emerging mupirocin resistance in methicillin-resistant Staphylococcus aureus isolates at a tertiary care children’s hospital in Argentina

“…Other authors have reported a high level of simultaneous mupirocin resistance with other antibiotics in association with a more frequent MRSA colonization. [4][5][6][7][8][9][10][11][12] Therefore, mupirocin is recommended as a first-line treatment for impetigo in patients with a limited number of lesions, especially considering MRSA local resistance patterns as per the 2014 guidelines of the Infectious Diseases Society of America. 3 In a children's hospital in the USA, mupirocin resistance was detected in 14.7 % of S. aureus isolates in association with recurrent skin and soft tissue infections, which was higher than the rate observed in other community studies conducted in children (1.8 %).…”

“…In relation to the possible correlation between mupirocin resistance in MRSA and its ability to form biofilm, other authors have reported biofilm-forming MUP-R-MRSA strains isolated in swabs from infected wounds collected after a surgery. 12 It has been suggested that biofilm formation may play a role in mupirocin resistance in the overall population of hospitalized patients. 11,12…”

“…12 It has been suggested that biofilm formation may play a role in mupirocin resistance in the overall population of hospitalized patients. 11,12…”

Resistencia emergente a la mupirocina en aislados de Staphylococcus aureus resistente a meticilina en un hospital pediátrico terciario en la Argentina

“…Otros autores reportaron un alto nivel de resistencias simultáneas de la mupirocina con otros antibióticos asociado con una recolonización más habitual por SARM. [4][5][6][7][8][9][10][11][12] Por ello, la mupirocina se recomienda como tratamiento de primera línea para el impétigo en los pacientes con un número limitado de lesiones y, sobre todo, teniendo en cuenta los patrones locales de resistencia del SARM según las directrices de 2014 de la Sociedad de Enfermedades Infecciosas. 3 En un hospital de niños de EE.…”

“…Con respecto a la posible correlación entre la resistencia a la mupirocina en los aislados de SARM y su capacidad para formar el biofilm, otros autores reportaron cepas de SARM-R-MUP aisladas a través de hisopados de heridas infectadas tomados posoperación, que eran productoras de biofilm. 12 Se ha sugerido que la formación de biofilm puede jugar un papel en la resistencia a la mupirocina entre las poblaciones de pacientes hospitalizados en general. 11,12…”