Clinical, Microbiological, and Genetic Characteristics of Heteroresistant Vancomycin-Intermediate Staphylococcus aureus Bacteremia in a Teaching Hospital

Abstract

The emergence of vancomycin intermediate Staphylococcus aureus (VISA) and heterogeneous VISA (hVISA) is of major concern worldwide. Our objective was to investigate the prevalence, phenotypic and molecular features of hVISA strains isolated from bacteremic patients and to determine the clinical significance of the hVISA phenotype in patients with bacteremia. A total of 104 S. aureus blood isolates were collected from a teaching hospital of Argentina between August 2009 and November 2010. No VISA isolate was recovered, and 3 out of 92 patients (3.3%) were infected with hVISA, 2 of them methicillin-resistant S. aureus (MRSA) (4.5% of MRSA). Macro Etest and prediffusion method detected 3/3 and 2/3 hVISA respectively. Considering the type of bacteremia, the three cases were distributed as follows: two patients had suffered multiple episodes of bacteremia (both hVISA strains recovered in the second episode), while only one patient had suffered a single episode of bacteremia with hVISA infection. MRSA bloodstream isolates exhibiting the hVISA phenotype were related to HA-MRSA Cordobes clone (ST5-SCCmec I-spa t149) and MRSA Argentinean pediatric clone (ST100-SCCmec IVNV-spa t002), but not to CA-MRSA-ST30-SCCmec IV-spa t019 clone that was one of the most frequent in our country. Although still relatively infrequent in our hospital, hVISA strains were significantly associated with multiple episodes of bacteremia (p=0.037) and genetically unrelated.

Recent pattern of antibiotic resistance in Staphylococcus aureus clinical isolates in Eastern India and the emergence of reduced susceptibility to vancomycin

“…[25][26][27] Further, among 127 MRSA isolates, 91 (71.6%) were MDR, which is similar to the study by Tiwari et al, [27] where among 783 isolates of S. aureus, 301 (38.4%) were methicillin resistant, of which 217 (72.1%) were found to be MDR. Similar to previous studies, [12,25,26] the present study also observed that MRSA isolates were significantly more resistant to various antibiotics, such as penicillin, trimethoprim-sulfamethoxazole, fluoroquinolones, erythromycin, and clindamycin as well as they exhibited significantly more multidrug resistance.…”

“…Hence, newer tests such as the glycopeptide resistance detection (GRD) Etest and the macromethod Etest are being used recently. [11,12] With the emergence of RVS, various alternative therapeutic options have been advocated for the treatment of resistant S. aureus infections such as ceftaroline, tigecycline, linezolid, telavancin, and daptomycin, which have shown considerable clinical efficacy against S. aureus in various studies. [13,14] Only a few studies from India have previously reported reduced susceptibility to vancomycin after the introduction of the revised CLSI guidelines.…”

Aislamiento de Staphylococcus aureus hetero-resistente a vancomicina en Hospital Clínico Regional de Concepción, Chile

“…La prevalencia de SAIVh es difícil de determinar por el amplio número de metodologías para su detección, pero se estima que corresponde a 1,3% de los aislados de SARM de aislados de SAIVh; sin embargo, recientemente Di Gregorio y cols. 13 , comunicaron una prevalencia de 3,3% de SAIVh en un hospital universitario de Argentina.…”

Características moleculares de Staphylococcus aureus suscetível à vancomicina poderia ajudar a prever falhas no tratamento devido à reduzida suscetibilidade à vancomicina

“…Although the relevance of hVISA persists unclear, studies speculate that these isolates could be a precursor of VISA phenotype. [9][10][11] MRSA strains also develop vancomycin tolerance, whose infections are even more difficult to treat, especially when they are invasive and present in immunocompromised patients. 7 Additionally, this reduced vancomycin suscepti-bility is associated with dysfunction in the accessory gene regulator (agr) locus, a quorum sensing system that controls the expression of genes encoding virulence factors.…”