Variable-Number Tandem Repeat Analysis and Multilocus Sequence Typing Data Confirm the Epidemiological Changes Observed with Staphylococcus aureus Strains Isolated from Bloodstream Infections

Abstract

Since 2000, our geographical region in France systematically surveys bloodstream infections (BSI) due to Staphylococcus aureus. This survey involves 39 health care institutions (HCIs) encompassing 6,888 short-stay beds and was performed during two 3-month periods during 2007 and 2008. The study periods of this survey identified 292 S. aureus isolates causing BSI. Extensive molecular characterization, including genotyping as well as toxin, agr, and staphylococcal cassette chromosome content determinations, allowed us to describe epidemiological evolution in comparison to that discussed in our previous study. Our main epidemiological observation shows that the incidence of BSI remained constant but that methicillin (meticillin)-resistant S. aureus strains with a wider variety of genetic backgrounds now harbor pyl, as has already been reported in different European countries. We noticed stable numbers of BSI episodes involving community-acquired methicillin-sensitive S. aureus (MSSA), whereas a drastic increase in the number of strains harboring the tst gene was recorded. The increase in the number of tst gene-harboring strains is related to known hospitalacquired MSSA isolates and appears related to epidemic episodes in specific HCIs. Monitoring the increase in prevalence of specific strains helps us understand where the standard precautions are not satisfactorily applied or do not efficiently prevent the spread of epidemic MSSA strains in these HCIs. The recent increases in incidence of these strains call for particular vigilance to avoid the spread of potentially virulent MSSA strains harboring the tst gene and for continuance of this strategy of BSI surveillance.Reporting of methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infections (BSI) is often mandatory, and reduction of BSI rates is a performance target (2,15,16,19,22,23). Since 2000, a prospective, longitudinal survey of BSI has been under way at a regional level in France. Results obtained during the first 7 years of surveillance have been reported (26,27). After sustained and decreasing incidence rates of S. aureus BSI attributed to successful infection control efforts in participating health care institutions (HCIs), we reported in 2006 a sudden increase in incidence that involved two populations of S. aureus strains: one of methicillin-sensitive S. aureus (MSSA) strains and one of MRSA isolates.First, an increasing incidence of BSI was observed due to MSSA strains, including (i) strains associated with epidemic phenomena in HCIs and (ii) a genetically homogeneous population of tst-positive MSSA isolates, mostly associated with community-acquired (CA) BSI, suggesting clonal spread at a regional level.Second, we observed the emergence of BSI associated with genetically diverse nonmultiresistant staphylococcal cassette chromosome mec type IV (SCCmec IV) MRSA strains (named NORSA) that could not be related to any local outbreak in the participating HCIs.We report here data collected in 2007 and 2008 using exactly the same study design. Agai...

Genotyping of 353 Staphylococcus aureus Bloodstream Isolates Collected between 2004 and 2009 at a Norwegian University Hospital and Potential Associations with Clinical Parameters

“…The frequency of isolates containing the tst gene (15.3%) correlates well with previous findings on SAB and asymptomatic S. aureus carriers (9,14).…”

Predominant Effect of Host Genetics on Levels of Lactobacillus johnsonii Bacteria in the Mouse Gut

“…Strain characterization was conducted on L. johnsonii, a potentially probiotic bacterium (38) that was found here to populate the gut of C57BL/6J mice at higher levels than in BALB/c mice. Molecular typing of L. johnsonii was performed by MLST and VNTR analysis, widely used methods for strain typing and for epidemiological studies in many bacterial species (4,7,47,49). Both VNTR and MLST of conserved hypothetical genes did not discriminate between strains isolated from the two mouse lines, in contrast to the high discrimination that we had achieved among other L. johnsonii strains isolated from various hosts in general and mice in particular (Buhnik-Rosenblau et al, submitted).…”

Indication for Co-evolution of Lactobacillus johnsonii with its hosts

“…The complete genomic sequence of L. johnsonii NCC 533, obtained from the NCBI database, was screened for perfect SSR (i.e., exact-repeat motifs) using the “SSR” computer program [ 37 , 50 ], and for non-perfect SSR (NP-SSR, i.e. non-exact repeat motifs) using the “ATR Hunter” computer program ( http://bioinfo.cs.technion.ac.il/atrhunter/ATRHunter.htm [ 51 ]).…”

“…In this study we used simple sequence repeats (SSR), also termed variable number tandem repeats (VNTR). SSR loci presents inherently high mutation rate [ 34 ], which makes them an appropriate tool for strain typing in many bacterial species [ 35 - 37 ].…”