Staphylococcus aureus intestinal colonization is associated with increased frequency of S. aureus on skin of hospitalized patients.

BACKGROUND: Intestinal colonization by Staphylococcus aureus among hospitalized patients has been associated with increased risk of staphylococcal infection and could potentially contribute to transmission. We hypothesized that S. aureus intestinal colonization is associated with increased frequency of S. aureus on patients' skin and nearby environmental surfaces. METHODS: Selected inpatients were cultured weekly for S. aureus from stool, nares, skin (groin and axilla), and environmental surfaces (bed rail and bedside table). Investigator's hands were cultured after contacting the patients' skin and the environmental surfaces. RESULTS: Of 71 subjects, 32 (45.1%) had negative nares and stool cultures, 23 (32.4%) had positive nares and stool cultures, 13 (18.3%) were nares carriers only, and 3 (4.2%) were stool carriers only. Of the 39 patients with S. aureus carriage, 30 (76.9%) had methicillin-resistant isolates. In comparison to nares colonization only, nares and intestinal colonization was associated with increased frequency of positive skin cultures (41% versus 77%; p = 0.001) and trends toward increased environmental contamination (45% versus 62%; p = 0.188) and acquisition on investigator's hands (36% versus 60%; p = 0.057). Patients with negative nares and stool cultures had low frequency of S. aureus on skin and the environment (4.8% and 11.3%, respectively). CONCLUSION: We found that hospitalized patients with S. aureus nares and/or stool carriage frequently had S. aureus on their skin and on nearby environmental surfaces. S. aureus intestinal colonization was associated with increased frequency of positive skin cultures, which could potentially facilitate staphylococcal infections and nosocomial transmission.

Acquisition of nosocomial pathogens on hands after contact with environmental surfaces near hospitalized patients.

We examined the frequency of acquisition of bacterial pathogens on investigators' hands after contacting environmental surfaces near hospitalized patients. Hand imprint cultures were positive for one or more pathogens after contacting surfaces near 34 (53%) of 64 study patients, with Staphylococcus aureus and vancomycin-resistant Enterococcus being the most common isolates.

Coexistence of vancomycin-resistant enterococci and Staphylococcus aureus in the intestinal tracts of hospitalized patients.

The potential for transfer of vancomycin-resistance genes from enterococci to Staphylococcus aureus exists when these organisms share an ecologic niche. We performed an 8-month prospective study to determine the frequency at which S. aureus and vancomycin-resistant enterococci (VRE) coexist in the intestinal tracts of VRE-colonized patients and evaluated whether antianaerobic antibiotic therapy promoted increased density of S. aureus colonization. Of 37 patients colonized with vancomycin-resistant Enterococcus faecium, 23 (62%) had S. aureus recovered from stool specimens and 20 (87%) had methicillin-resistant strains. There was no significant difference in the mean density (+/- standard deviation) of S. aureus during versus > or =1 month after discontinuation of antianaerobic antibiotic therapy (5.1+/-1.5 vs. 4.7+/-1.6 log10 colony-forming units per gram of stool; P=.34). No S. aureus isolates were resistant to vancomycin. S. aureus and VRE often coexist in the intestinal tract, providing a potential reservoir for the emergence of vancomycin-resistant S. aureus isolates.

Antianaerobic antibiotic therapy promotes overgrowth of antibiotic-resistant, gram-negative bacilli and vancomycin-resistant enterococci in the stool of colonized patients.

BACKGROUND AND OBJECTIVE: Antianaerobic antibiotic therapy promotes persistent high-density growth of vancomycin-resistant enterococci (VRE) in the stool of colonized patients. We tested the hypothesis that antibiotic regimens with potent antianaerobic activity promote overgrowth of coexisting antibiotic-resistant, gram-negative bacilli in the stool of VRE-colonized patients. DESIGN: Eight-month prospective study examining the effect of antibiotic therapy on the stool density of gram-negative bacilli resistant to ceftazidime, ciprofloxacin, or piperacillin/tazobactam. SETTING: A Department of Veterans Affairs medical center including an acute care hospital and nursing home. PATIENTS: All VRE-colonized patients with at least 3 stool samples available for analysis. RESULTS: One-hundred forty stool samples were obtained from 37 study patients. Forty-nine (61%) of 80 stool samples obtained during therapy with an antianaerobic regimen were positive for an antibiotic-resistant, gram-negative bacillus, where-as only 14 (23%) of 60 samples obtained 4 or more weeks after completion of such therapy were positive (P < .001). Twenty-four (65%) of the 37 patients had one or more stool cultures positive for a gram-negative bacillus resistant to ciprofloxacin, ceftazidime, or piperacillin/tazobactam. The density of these organisms was higher during therapy with antianaerobic regimens than in the absence of such therapy for at least 2 weeks (mean +/- standard deviation, 5.6 +/- 1.4 and 3.9 +/- 0.71 log10 organisms/g; P < .001). CONCLUSION: Limiting the use of antianaerobic antibiotics in VRE-colonized patients may reduce the density of colonization with coexisting antibiotic-resistant, gram-negative bacilli.