High-Level Vancomycin-Resistant Staphylococcus aureus Isolates Associated with a Polymicrobial Biofilm

Abstract

Glycopeptides such as vancomycin are the treatment of choice for infections due to methicillin-resistant Staphylococcus aureus. This study describes the identification of high-level vancomycin-resistant S. aureus (VRSA) isolates in a polymicrobial biofilm within an indwelling nephrostomy tube in a patient in New York. S. aureus, Enterococcus faecalis, Enterococcus faecium, Micrococcus species, Morganella morganii, and Pseudomonas aeruginosa were isolated from the biofilm. For VRSA isolates, vancomycin MICs ranged from 32 to >128 g/ml. VRSA isolates were also resistant to aminoglycosides, fluoroquinolones, macrolides, penicillin, and tetracycline but remained susceptible to chloramphenicol, linezolid, rifampin, and trimethoprim-sulfamethoxazole. The vanA gene was localized to a plasmid of ϳ100 kb in VRSA and E. faecium isolates from the biofilm. Plasmid analysis revealed that the VRSA isolate acquired the 100-kb E. faecium plasmid, which was then maintained without integration into the MRSA plasmid. The tetracycline resistance genes tet(U) and tet(S), not previously detected in S. aureus isolates, were identified in the VRSA isolates. Additional resistance elements in the VRSA isolate included a multiresistance gene cluster, ermB-aadE-sat4-aphA-3, msrA (macrolide efflux), and the bifunctional aminoglycoside resistance gene aac(6)-aph(2؆)-Ia. Multiple combinations of resistance genes among the various isolates of staphylococci and enterococci, including vanA, tet(S), and tet(U), illustrate the dynamic nature of gene acquisition and loss within and between bacterial species throughout the course of infection. The potential for interspecies transfer of antimicrobial resistance genes, including resistance to vancomycin, may be enhanced by the microenvironment of a biofilm.

Response of corneal epithelial cells toStaphylococcus aureus

“…[9][10][11] Isolates with reduced susceptibility and even acquired resistance to last line drugs, including vancomycin, have been reported. 12,13 S. aureus expresses virulence traits that exacerbate invasive infection.…”

Antibiotic Resistance in Staphylococcus Species of Animal Origin

“…Studies report the transfer of glycopeptide-and macrolide-resistance genes by transconjugation among enterococci and from Enterococcus faecalis to S. aureus (Młynarczyk et al, 2002). The vancomycin-resistance gene acquisition by S. aureus from E. faecium in the clinical environment has also been reported by Weigel et al (2007). Recently, Tiwari & Sen (2006) have reported a VRSA which is van gene-negative.…”

“…From there on, reports of strains of S. aureus (predominately MRSA) demonstrating the heterogeneous VISA (hVISA) or VISA phenotype have now been reported for many countries including the United States, Japan, Australia, France, Scotland, Brazil, South Korea, Hong Kong, South Africa, Thailand, Israel, and others (Bierbaum et al 1999;Chang et al, 2003;Denis et al 2002;Ferraz et al, 2000Gemmell, 2004Howden et al, 2010;Kim et al, 2000;Perichon & Courvalin, 2006;Sng et al,2005;Song et al, 2004;Tenover et al, 2004;Weigel et al, 2007) Nowadays it is conceivable that VISA phenotype is related to the bacterial cell wall thickening, a passive resistance mechanism that reduces vancomycin access to its active site, which is localized in the cytoplasmic membrane in the division septum (Howden et al, 2010). It results in accumulation of acyl-D-alanyl-D-alanine (X-DAla-D-Ala) targets in the periphery that sequester glycopeptides (Cui et al, 2003).…”

Antibiofilm activity of natural substances derived from plants

“…They constitute microbial societies with their own set of social rules and behavior patterns, including altruism and cooperation, favoring group success (Parsek and Greenberg, 2005;Shapiro, 1998) by replicating behaviors on one side and competition (Velicer, 2003) on another. Certain subpopulations may show specialization; these behavioral patterns are orchestrated by chemical communications (Weigel et al, 2007). Thus, they constitute a unique form of interaction between species, inducing drastic changes in symbiotic relations between their components (Hansen et al, 2007).…”