ABSTRACT
BACKGROUND: Staphylococcus aureus nasal carriage is influenced by multifactorial interactions which are difficult to study in open populations. Therefore, we concomitantly assessed the epidemiological, microbiological, and human-genetic carriage-related factors in a nearly closed population. METHODS: In 2006 and 2008, we collected nasal S. aureus strains, human DNA, and epidemiological data from 154 adult Wayampi Amerindians living in an isolated village in the Amazonian forest. The genetics of the strains (multilocus sequence type, spa type, and toxin-content type), epidemiological risk factors, antibiotic exposure, and allelic polymorphism of human genes putatively involved in carriage of the persistent carriers were compared with those of other volunteers. RESULTS: Overall carriage prevalence was 41.7% in 2006 and 57.8% in 2008, but the overall prevalence of persistent carriage was only 26%. The rare and phylogenetically distant multilocus sequence type ST1223 was present in 18.5% of the carriers in 2006 and 34.8% in 2008. No epidemiological factors or antibiotic exposure were significantly associated with persistent carriage, but single nucleotide polymorphism distribution in C-reactive proteins C2042T and C1184T and interleukin-4 C524T genes was significantly associated (P=.02, by global test). CONCLUSION: Host genetic factors appeared to be the predominant determinant for S. aureus persistent nasal carriage in humans.
Subject(s)
Carrier State/microbiology , Nasal Cavity/microbiology , Staphylococcal Infections/genetics , Staphylococcus aureus/isolation & purification , Adolescent , Adult , Aged , Aged, 80 and over , Bacterial Typing Techniques , C-Reactive Protein/genetics , Carrier State/epidemiology , DNA Fingerprinting , Female , Gene Frequency , Genotype , Humans , Indians, South American , Interleukin-4/genetics , Male , Middle Aged , Polymorphism, Genetic , Prevalence , Risk Factors , Rural Population , Staphylococcal Infections/epidemiology , Staphylococcal Infections/microbiology , Staphylococcus aureus/classification , Staphylococcus aureus/genetics , Young AdultABSTRACT
BACKGROUND: Intestinal carriage is a key factor in extended-spectrum beta-lactamase (ESBL) infection epidemiology but is difficult to study in open communities. To overcome this problem, we studied a highly stable group of Amerindians for whom we reported an ESBL carriage prevalence of 3.2% in 2001. METHODS: In 2006, ESBL carriage was assessed among 163 healthy volunteer adults. ESBL isolates were identified, and their molecular resistance mechanisms were characterized. Antibiotic use in the year before sampling and the epidemiological characteristics of the population were analyzed. Results were compared to those obtained in 2001. RESULTS: In 2006, the ESBL carriage prevalence, exclusively comprising Escherichia coli, was 8.0%. It mainly consisted of CTX-M-type ESBL. The strains and plasmids carrying ESBL were heterogeneous, but 1 CTX-M-2-producing strain was found in 4.3% of the subjects analyzed. No individual risk factor was identified. However, overall antibiotic use had almost doubled since 2001. A 3-fold increase was noted for beta-lactams. CONCLUSIONS: In this population, the frequency of ESBL increased with time because of the appearance of CTX-M ESBL, mimicking what occurs in the developed world. This resulted from the probable repeated introduction of new strains and plasmids and from interindividual dissemination. During the same period, antibiotic use substantially increased.
