<Emphasis Type="Italic">Staphylococcus aureus</Emphasis> colonization in the nasopharynx of nasogastric tube-fed patients in a long-term care facility

The purpose of this paper is to investigate whether the presence of a nasogastric tube (NGT) for feeding has an impact on the nasal colonization by Staphylococcus aureus. Three groups of frail elderly were examined: 76 patients fed by NGTs and 52 orally fed patients in skilled nursing wards, and 33 orally fed patients in regular nursing wards. Samples from the nasal and oral cavities were cultured for S. aureus and susceptibility testing for oxacillin was performed. The prevalence of S. aureus (either oxacillin-susceptible or oxacillin-resistant) in the NGT-fed group was not significantly different to that in the two orally fed groups nor the nostril in which the NGT was placed. A significant correlation in colonization was found between the two nares and between the nares and oral cavity in the same patient (r > 0.45, P < 0.005) for both oxacillin-susceptible and oxacillin-resistant S. aureus. The presence of NGTs for feeding in elderly frail patients is not associated with higher rates of S. aureus colonization in the nares or oral cavity.     

Intracellular and extracellular NO differentially modulates the stress response and apoptosis in macrophages exposed to the influence of biological or physical factors

We studied the role of extracellular and intracellular NO in the regulation of the stress response and apoptosis in macrophages of proinflammatory and antiinflammatory phenotypes under the influence of S. aureus and heat shock. Blockade of extracellular nitric oxide synthesis in cells with antiinflammatory phenotype inhibited the stress response induced by S. aureus and heat shock. The decrease in extracellular nitric oxide concentration around antiinflammatory macrophages potentiated the stress response induced by S. aureus, but had no effect on the stress response induced by heat shock. Hence, intracellular NO mediates the stress response induced by S. aureus and heat shock, while extracellular NO inhibits the stress response induced by S. aureus, but has no effect on the stress response induced by heat shock. In cells with antiinflammatory phenotype, intracellular NO plays an antiapoptotic role. S. aureus and heat shock did not cause apoptosis in macrophages with proinflammatory phenotype, while intracellular NO did not play a role in antiapoptotic activity of the proinflammatory phenotype. Extracellular NO synthesized by macrophages protects these cells from apoptosis induced by S. aureus and heat shock. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 143, No. 6, pp. 614–618, June, 2007     

Isolation and characterization of a novel Staphylococcus aureus bacteriophage, ϕMR25, and its therapeutic potential

A novel bacteriophage, ϕMR25, was isolated from a lysogenic Staphylococcus aureus strain by mitomycin C induction. Its biological features were analyzed in comparison with ϕMR11, which was described previously as a prototype therapeutic phage. ϕMR25 is morphologically similar to ϕMR11 (morphotype B1 of family Myoviridae) but has a broader host range than ϕMR11 on S. aureus strains. ϕMR25 can also multiply on S. aureus lysogens of ϕMR11. Its DNA is 44,342 bp in size, is predicted to include 70 open reading frames, and does not contain genes related to toxin or drug resistance. The lysogenic module and most of the putative virion protein genes are completely different from those of ϕMR11. In spite of their genetic diversity, intraperitoneal administration of ϕMR25 rescued mice inoculated with a lethal dose of S. aureus, as was the case for ϕMR11. These results suggest that ϕMR25 could be another candidate phage to treat S. aureus infection.     

High prevalence of ST121 in community-associated methicillin-susceptible Staphylococcus aureus lineages responsible for skin and soft tissue infections in Portuguese children

In order to evaluate the incidence of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) in Portugal, we analyzed a collection of 38 S. aureus isolates recovered from 30 children attending the pediatric emergency department of a central hospital in Lisbon due to skin and soft tissue infections. Molecular characterization identified seven clonal lineages among the 35 methicillin-susceptible S. aureus (MSSA) isolates, of which the major lineage PFGE A/t159/ST121 included 63% of the isolates. The three MRSA isolates belonged to the Pediatric clone PFGE D/t535/ST5-IV (n = 2) and to the European CA-MRSA clone PFGE G/t044/ST80-IVc (n = 1). All isolates harbored several virulence factors, namely, leukocidins. Panton–Valentine leukocidin (PVL) was produced by isolates from five MSSA lineages and by the ST80 MRSA. Of interest, this is the first reported isolation of CA-MRSA ST80 in Portugal.     

Prevalence of community-associated meticillin-resistant Staphylococcus aureus and Panton–Valentine leucocidin-positive S. aureus in general practice patients with skin and soft tissue infections in the northern and southern regions of The Netherlands

The purpose of this investigation was to determine the prevalence of community-associated meticillin-resistant Staphylococcus aureus (CA-MRSA) and Panton–Valentine leucocidin (PVL)-positive S. aureus in general practice (GP) patients with skin and soft tissue infections (SSTI) in the northern (Groningen and Drenthe) and southern (Limburg) regions of The Netherlands. Secondary objectives were to assess the possible risk factors for patients with SSTI caused by S. aureus and PVL-positive S. aureus using a questionnaire-based survey. From 2007 to 2008, wound and nose cultures were obtained from patients with SSTI in general practice. These swabs were analysed for the presence of S. aureus and the antibiotic susceptibility was determined. The presence of the PVL toxin gene was determined by polymerase chain reaction (PCR) and the genetic background with the use of spa typing. A survey was performed to detect risk factors for S. aureus infection and for the presence of PVL toxin.S. aureus was isolated from 219 out of 314 (70%) patients with SSTI, of which two (0.9%) patients were MRSA-positive. In 25 (11%) patients, the PVL toxin gene was found. A higher prevalence of PVL-positive S. aureus of patients with SSTI was found in the northern region compared to the south (p < 0.05). Regional differences were found in the spa types of PVL-positive S. aureus isolates, and for PVL-negative S. aureus isolates, the genetic background was similar in both regions. The prevalence of CA-MRSA in GP patients with SSTI in The Netherlands is low. Regional differences were found in the prevalence of PVL-positive S. aureus isolates from GP patients with SSTI. Household contacts having similar symptoms were found to be a risk factor for SSTI with S. aureus.     

Molecular characterization of Staphylococcus aureus from outpatients in the Caribbean reveals the presence of pandemic clones

Staphylococcus aureus infections continue to pose a global public health problem. Frequently, this epidemic is driven by the successful spread of single S. aureus clones within a geographic region, but international travel has been recognized as a potential risk factor for S. aureus infections. To study the molecular epidemiology of S. aureus infections in the Caribbean, a major international tourist destination, we collected methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) isolates from community-onset infections in the Dominican Republic (n = 112) and Martinique (n = 143). Isolates were characterized by a combination of pulsed-field gel electrophoresis (PFGE), spa typing, and multilocus sequence typing (MLST) typing. In Martinique, MRSA infections (n = 56) were mainly caused by t304-ST8 strains (n = 44), whereas MSSA isolates were derived from genetically diverse backgrounds. Among MRSA strains (n = 22) from the Dominican Republic, ST5, ST30, and ST72 predominated, while ST30 t665-PVL+ (30/90) accounted for a substantial number of MSSA infections. Despite epidemiological differences in sample collections from both countries, a considerable number of MSSA infections (~10%) were caused by ST5 and ST398 isolates at each site. Further phylogenetic analysis suggests the presence of lineages shared by the two countries, followed by recent genetic diversification unique to each site. Our findings also imply the frequent import and exchange of international S. aureus strains in the Caribbean.     

Heparan sulfate proteoglycans mediate Staphylococcus aureus interactions with intestinal epithelium

Staphylococcus aureus can be internalized by non-professional phagocytes, and may colonize the intestine in normal and antibiotic-treated individuals. Intestinal colonization may depend on the interactions of S. aureus with the intestinal epithelium. The best described mechanism of S. aureus binding to eukaryotic cells involves S. aureus fibronectin binding proteins (FnBPs), using fibronectin as a bridging molecule to β1 integrins on the eukaryotic cell surface. Because S. aureus can be internalized by enterocytes, and because S. aureus is known to bind heparan sulfate (HS), we hypothesized that heparan sulfate proteoglycans (HSPGs) widely expressed on epithelia may mediate S. aureus interactions with intestinal epithelial cells. Internalization of S. aureus RN6390 by cultured intestinal epithelial cells was inhibited in a dose-dependent fashion by the HS mimic heparin, and by HS itself. Internalization of S. aureus DU5883, which lacks expression of staphylococcal FnBPs, was also inhibited by heparin. S. aureus adherence to ARH-77 cells, transfected to express the HSPG syndecan-1, was greatly increased when compared to adherence to plasmid control ARH-77 cells which have little detergent extractable HS. In addition, compared to wild-type HS-expressing Chinese hamster ovary (CHO) cells, internalization of S. aureus was decreased using mutant CHO cells with decreased HS expression. These findings are consistent with a model wherein S. aureus internalization by intestinal epithelial cells (and perhaps other epithelia) is mediated by S. aureus binding to the HS moiety of cell-surface HSPGs, and this interaction appears independent of fibronectin binding.     

Long-term cortisol levels are not associated with nasal carriage of Staphylococcus aureus

Staphylococcus aureus (S. aureus) colonizes the anterior nares in part of the population and the persistent carrier state is associated with increased infection risk. Knowledge concerning the determinants of S. aureus nasal carriage is limited. Previously, we found that glucocorticoid receptor polymorphisms influence carrier risk, suggesting involvement of glucocorticoids. Our aim was to study long-term cortisol levels in non-carriers, intermittent, and persistent carriers of S. aureus. We hypothesized that cortisol levels are higher in carriers, since cortisol-induced immune suppression would enhance S. aureus colonization. We determined nasal carrier state and long-term hair cortisol levels in 72 healthy subjects. Nasal swabs were collected twice with an interval of 2 weeks. Cortisol levels were determined in hair segments of 3 cm, which corresponds to a period of roughly 3 months. Of all 72 participants, 38 were non-carriers, 10 were intermittent carriers, and 24 were persistent carriers of S. aureus. Cortisol levels did not differ between these carrier groups (p = 0.638). Long-term cortisol levels are not associated with S. aureus nasal carriage.     

Neuraminidase produces a decrease of adherence of slime-forming <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> to gelatin-impregnated polyester fiber graft fabric: an experimental study

Because slime-forming microorganisms are the major causative agents of graft infections, we aimed to investigate bacterial adherence in slime-forming and nonslime-forming Staphylococcus aureus and to determine the role of neuraminidase (NANase) on adherence to gelatin-impregnated polyester fiber graft fabric. An in vitro model was developed to quantitatively measure bacterial adherence to the surface of the graft. The grafts were divided into two groups – those colonized with slime-forming S. aureus and those colonized with nonslime-forming S. aureus. The grafts were put into sterile tubes and human plasma was instilled and incubated at 37°C to perform fibrin deposition on the grafts. After 48 h of incubation, grafts were drained and inoculated with slime-forming or nonslime-forming S. aureus in triptic soy broth in the presence or absence of NANase. Following 36 h of incubation at 36°C, grafts were vortexed and cultured to perform a colony count. Bacterial counts were expressed as total colony-forming units per square centimeter of graft. Slime-forming S. aureus had greater affinity with the graft compared with nonslime-forming S. aureus (P < 0.05). The adherence of slime-forming S. aureus was impaired by NANase treatment (P < 0.001) but NANase treatment of nonslime-forming S. aureus did not change the adherence to the graft (P > 0.05). These results show that slime plays an important role in the pathogenesis of vascular graft infection. Adherence of slime-forming S. aureus can be decreased by NANase treatment. This may have implications for the development of neuraminidase-embedded vascular grafts to diminish biomaterial-related infections.     

Evaluation of discrepancies between oxacillin and cefoxitin disk susceptibility for detecting methicillin-resistant <Emphasis Type="Italic">Staphylococcus aureus</Emphasis>

The Clinical Laboratory Standards Institute recommends that if both cefoxitin and oxacillin are tested against Staphylococcus aureus and either result is measured as resistant, the organism should be reported as oxacillin resistant. This indicates that discrepancies may be present between oxacillin and cefoxitin sensitivities in S. aureus. In this study, we aimed to investigate the discrepancy between oxacillin and cefoxitin susceptibility in S. aureus clinical isolates. Of 10,980 S. aureus isolates recovered from 2005 to 2010, 27 (0.3%) isolates with discordant results between oxacillin and cefoxitin were collected. Fourteen (oxacillin diameters 10–12 mm) of the 27 strains were susceptible (MICs = 0.5–2 μg/ml) and 13 (6–13 mm) were resistant (4–>256 μg/ml) to oxacillin. The cefoxitin MICs of 14 oxacillin-susceptible and 13 oxacillin-resistant strains ranged between 4 and 8 and 8 to 32 μg/ml, respectively. Discrepancies were present between oxacillin and cefoxitin in S. aureus, and these strains should be further tested for oxacillin MICs and for the mecA gene or β-lactamase activity.     

The effect of growth temperature on Staphylococcus aureus binding to type I collagen

Many strains of Staphylococcus aureus produce a collagen-binding surface protein that could enable these strains to colonize tissues such as bone. Previous studies indicated that the expression of the collagen receptor varies with growth conditions. We report here that the growth temperature influences the ability of some S. aureus strains to produce this receptor.S. aureus isolates from human, osteomyelitic bone were grown at 37°C and 42°C and tested for agglutination of collagen-coated latex beads. Binding by 42°C grown cells was significantly reduced in five of the seven isolates studied, including a complete loss of collagen binding in three of these isolates. In an ¹²⁵I-collagen-binding assay, the binding ability of one of these isolates, strain #16, was 20-fold lower if grown at 42°C. Reduced collagen binding by this isolate could be demonstrated after only two cell divisions at 42°C and the cells regained the ability to bind collagen when shifted back to 37°C.Sodium dodecyl sulfate (SDS)-PAGE confirmed the presence of proteins at 117 kDa in strain #16 and 135 kDa in SMH which were absent following growth at 42°C. Chicken IgG, specific for the 117 kDa protein, was found to react in immunoblot assays with these proteins as well as a protein of 135 kDa extracted from S. aureus Cowan 1. The antibody did not react with proteins extracted from non-binding strains. Strains #15 and #21, collagen-binders at both 37°C and 42°C, produced immunoreactive proteins at 110 and 135 kDa, respectively, in lysates from cells grown at both temperatures. Antibody against a recombinant form of a previously characterized collagen receptor was used to confirm cross reactivity with these novel collagen receptors. These data suggest that the ability to produce the collagen receptor is temperature sensitive in some S. aureus strains associated with osteomyelitis. It is proposed that a better understanding of the environmental effects on collagen receptor production could enhance our understanding of staphylococcal infections in bone and joints.     

Evaluation of the mecA femB Duplex Polymerase Chain Reaction for Detection of Methicillin-Resistant Staphylococcus aureus

 This study systematically evaluated a recently described duplex polymerase chain reaction test for methicillin-resistant Staphylococcus aureus with 25 different German epidemic strains of methicillin-resistant Staphylococcus aureus and 66 staphylococci other than methicillin-resistant Staphylococcus aureus, including 17 different coagulase-negative staphylococcal species and subspecies, that were either oxacillin susceptible or oxacillin resistant. The results were compared with those of conventional cultural identification and susceptibility testing. Of the 91 isolates tested, all 25 confirmed strains of methicillin-resistant Staphylococcus aureus were identified correctly. None of the remaining strains of methicillin-susceptible Staphylococcus aureus was misidentified as methicillin-resistant Staphylococcus aureus. It was concluded that the duplex polymerase chain reaction appears to offer a time-saving and accurate method of detection of methicillin-resistant Staphylococcus aureus.     

Staphylococcus aureus nasal carriage is associated with serum 25-hydroxyvitamin D levels, gender and smoking status. The Troms? Staph and Skin Study

Vitamin D induces the expression of antimicrobial peptides with activity against Staphylococcus aureus. Thus, we studied the association between serum 25-hydroxyvitamin D (25(OH)D) and S. aureus nasal colonization and carriage. Nasal swabs, blood samples and clinical data from 2,115 women and 1,674 men, aged 30–87 years, were collected in the Troms? Staph and Skin Study 2007–08, as part of the population-based sixth Troms? Study. Multivariate logistic regression analyses were stratified by recognized risk factors for S. aureus carriage: sex, age and smoking. In non-smoking men, we observed a 6.6% and 6.7% decrease in the probability of S. aureus colonization and carriage, respectively, by each 5 nmol/l increase in serum 25(OH)D concentration (P < 0.001 and P = 0.001), and serum 25(OH)D > 59 nmol/l and ≥75 nmol/l as thresholds for ~30% and ~50% reduction in S. aureus colonization and carriage. In non-smoking men aged 44–60 years, the odds ratio for S. aureus colonization was 0.44 (95% confidence interval, 0.28−0.69) in the top tertile of serum 25(OH)D versus the bottom tertile. In women and smokers there were no such associations. Our study supports that serum vitamin D is a determinant of S. aureus colonization and carriage.     

High Prevalence of Superantigens Associated with the <Emphasis Type="Italic">egc</Emphasis> Locus in <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> Isolates from Patients with Atopic Eczema

The present study was aimed at identifying a possible correlation between disease severity and colonization with superantigen-producing Staphylococcus aureus strains in patients with atopic eczema. To this end, Staphylococcus aureus strains from 91 patients with atopic eczema were screened for various staphylococcal superantigens such as SEA, SEB, SEC, SED, TSST1, the recently described enterotoxin gene cluster egc (which encodes the enterotoxins SEG, SEI, SEK, SEM, and SEO), and the see, seh, and sej loci. Swabs were taken from seven different sites in each patient. The rate of colonization with Staphylococcus aureus was 87.9%. Of those patients colonized, 35% were colonized with more than one different strain. Of the 120 genetically different strains investigated, the egc locus was found in 48.3% and the sej locus in 7.5%. The see and seh loci were not found in any strain. The presence of the classical superantigens SEA-SED or TSST1 was found in 38.3%. Overall, 71.3% of the Staphylococcus aureus-positive patients harbored at least one superantigen-producing strain on their skin. There was no difference in the prevalence of superantigens between atopic eczema patients and healthy volunteers. Moreover, there was no difference in the extent of disease expression between patients colonized by superantigen-positive Staphylococcus aureus strains and those with superantigen-negative strains as measured by the SCORAD system. However, patients colonized with Staphylococcus aureus had a significantly higher SCORAD score than those not colonized. Electronic Publication     

Rapid detection of Panton–Valentine leukocidin-positive <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> by real-time PCR targeting the <Emphasis Type="Italic">luk</Emphasis>S-PV gene

In order to assess the speed and accuracy of a real-time PCR assay targeting the lukS-PV gene of Panton–Valentine leukocidin (PVL)-positive Staphylococcus aureus, 700 S. aureus strains were tested and the results were compared to those achieved with block cycler PCR. Cross-reactivity was tested with 166 other bacterial species. Using this homogeneous real-time PCR assay format, the presence or absence of genetic information for PVL, which is also found in community-associated methicillin-resistant S. aureus, was correctly identified from pure culture and directly in various types of clinical specimens.     

Infant colonization by <Emphasis Type="Italic">Staphylococcus aureus</Emphasis>: role of maternal carriage

Infant colonization by Staphylococcus aureus has not been adequately investigated. In this study, we aimed to define determinants associated with the carriage of S. aureus in early infancy. Serial nasal swabs were collected from 128 infants and their mothers at months 0, 6, and 12 postpartum. S. aureus isolates were characterized by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), spa typing, and the presence of chromosomal mecA and of Panton–Valentine leukocidin (PVL) genes. S. aureus was isolated in 17.7% and 15.7% of swabs from infants and mothers, respectively. Carriage rates were higher in infants with carrier mothers, non-smoking mothers, and many siblings. Persistent carriage rates were higher in infants with carrier or non-smoking mothers. S. aureus typing revealed identical strains in 10/15 investigated infant–mother pairs. Among 19 investigated S. aureus isolates from infants, ten harbored mecA and two harbored PVL genes, and these determinants were concomitantly present in isolates from mothers. Resistance to methicillin was 43.6% among all isolates from infants. In conclusion, isolates from infants were commonly identical to isolates from their mothers, pointing to a principal role of maternal carriage in S. aureus colonization in infants.     

Molecular Characterization and Transfer Among Staphylococcus Strains of a Plasmid Conferring High-Level Resistance to Mupirocin

 In this work, mupirocin resistance was correlated with the presence of plasmids in methicillin-resistant Staphylococcus aureus (MRSA) strains isolated in the Rio de Janeiro Federal University Hospital in Brazil, where topical mupirocin has been used extensively since 1990. Of 19 strains studied, those exhibiting high-level resistance carried a large and relaxable plasmid of about 35 kb. Mupirocin-sensitive derivatives, obtained by growth at 42  °C of a strain exhibiting high-level resistance, were devoid of the large plasmid, which was designated pMG1. Mupirocin resistance was transferred to strain RN8411 during overnight filter-matings at low frequencies (7.0×10^–9/donor). The pMG1 plasmid was shown to be responsible for high-level mupirocin resistance in our isolates and to be incompatible with pGO1. Hybridization experiments suggested that mupirocin resistance in pMG1 is due to the presence of the ileS-2 gene. The pMG1 plasmid was successfully and bidirectionally transferred from Staphylococcus aureus to Staphylococcus epidermidis, suggesting that the latter may be a reservoir of this resistance plasmid. No transfer was detected to Staphylococcus haemolyticus. The development of self-transferable high-level mupirocin resistance should be considered when using mupirocin to control the spread of MRSA in hospitals.