Usha Stiefel

Contamination of Hands with Methicillin-Resistant Staphylococcus aureus after Contact with Environmental Surfaces and after Contact with the Skin of Colonized Patients

In a study of 40 methicillin-resistant Staphylococcus aureus (MRSA) carriers, hand contamination was equally likely after contact with commonly examined skin sites and commonly touched environmental surfaces in patient rooms (40% vs 45%). These findings suggest that contaminated surfaces may be an important source of MRSA transmission.

Mechanisms by Which Anaerobic Microbiota Inhibit the Establishment in Mice of Intestinal Colonization by Vancomycin-Resistant Enterococcus

We used a mouse model to test the hypothesis that anaerobic microbiota in the colon inhibit the establishment of vancomycin-resistant enterococci (VRE) colonization by depleting nutrients within cecal contents and limiting the association of VRE with the mucus layer. Anaerobic growth of VRE was assessed in cecal contents and cecal mucus of mice that had received treatment with subcutaneous clindamycin or saline. VRE grew to high concentrations in cecal contents of clindamycin-treated mice and in cecal mucus of both groups but not in cecal contents of saline-treated mice, unless the cecal contents were autoclaved or converted into sterile filtrates. After orogastric inoculation of VRE, clindamycin-treated mice acquired high concentrations of VRE within the mucus layer, whereas saline-treated mice did not. These results suggest that colonic microbiota inhibit VRE by producing inhibitory substances or conditions rather than by depleting nutrients. The colonic mucus layer provides a potential niche for growth of VRE.

Effect of the increasing use of Piperacillin/Tazobactam on the incidence of Vancomycin‐resistant Enterococci in four academic medical centers

BACKGROUNDnThe substitution of piperacillin/tazobactam, ampicillin/sulbactam, or both for third-generation cephalosporins has been associated with reduced vancomycin-resistant enterococci (VRE). However, piperacillin/tazobactam came into widespread use during a period in which the prevalence of VRE increased. We hypothesized that the increasing use of piperacillin/tazobactam and other agents with relatively enhanced anti-enterococcal activity (ie, piperacillin, ampicillin/sulbactam, and ampicillin) has been associated with increased or unchanged rates of VRE in some hospitals.nnnDESIGNnWe retrospectively evaluated the correlation between hospital antibiotic use (defined daily doses per 10,000 patient-days of care) and incidence of stool or non-stool VRE isolation. We assessed whether a high or increasing proportion of use of beta-lactam agents with relatively enhanced versus minimal (ie, third-generation cephalosporins and ticarcillin/clavulanate) anti-enterococcal activity would prevent increased VRE.nnnSETTINGnFour academic medical centers.nnnRESULTSnWith the increasing use of piperacillin/tazobactam, the use of beta-lactam agents with enhanced activity against enterococci surpassed the combined use of third-generation cephalosporins and ticarcillin/clavulanate in each hospital. In one hospital, the incidence of VRE was positively correlated with the use of piperacillin/tazobactam or beta-lactam agents with enhanced anti-enterococcal activity (P < .0001). The incidence of VRE rose steadily in another hospital despite relatively high use of beta-lactam agents with enhanced versus minimal anti-enterococcal activity. A negative correlation between VRE and piperacillin/tazobactam or beta-lactam agents with enhanced anti-enterococcal activity was observed in one hospital, but this correlation was not statistically significant.nnnCONCLUSIONnIncreasing the hospital use of piperacillin/tazobactam and other beta-lactams with relatively enhanced anti-enterococcal activity may not be an effective control measure for VRE.

Occurrence of Skin and Environmental Contamination with Methicillin-Resistant Staphylococcus aureus before Results of Polymerase Chain Reaction at Hospital Admission Become Available

BACKGROUNDnActive surveillance to detect patients colonized with methicillin-resistant Staphylococcus aureus (MRSA) is increasingly practiced in healthcare settings. However, inpatients may already become sources of transmission before appropriate precautions are implemented.nnnOBJECTIVEnTo examine the frequency of MRSA contamination of commonly touched skin and environmental surfaces before patient carriage status became known.nnnMETHODSnWe conducted a 6-week prospective study of patients who were identified by use of polymerase chain reaction (PCR) at hospital admission as having nasal MRSA colonization. Skin and environmental contamination was assessed within hours of completion of PCR screening.nnnRESULTSnThere were 116 patients identified by PCR screening as having nasal MRSA colonization during the period from mid-April to May 2008, of whom 83 (72%) were enrolled in our study. Overall, MRSA was detected on the skin of 38 (51%) of 74 patients and in the environment of 37 (45%) of 83 patients. Of 83 environmental culture samples, 63 (76%) were obtained within 7 hours after PCR results became available, and 73 (88%) were obtained before wards were notified of PCR results. Of the 83 MRSA-colonized patients, 15 (18%) had contaminated their environment 25 hours after admission, and 29 (35%) had contaminated their environment 33 hours after admission. Thirty-two (39%) of the 83 patients had roommates, 13 (41%) of whom contaminated their environment. The median interval from admission to PCR result was 20 hours, and the median interval from PCR result to notification was 23 hours. An increased quantity of MRSA cultured from a nasal sample was significantly associated with contamination.nnnCONCLUSIONSnBefore any contact precautions can be implemented, newly identified MRSA carriers frequently have contaminated their environment with MRSA and have contamination of commonly examined skin sites. In hospitals that perform active surveillance, strategies are needed to minimize delays in screening or to preemptively identify patients at high risk for disseminating MRSA.

Oral Administration of β-Lactamase Preserves Colonization Resistance of Piperacillin-Treated Mice

We hypothesized that orally administered, recombinant class A beta-lactamase would inactivate the portion of parenteral piperacillin excreted into the intestinal tract, preserving colonization resistance of mice against nosocomial pathogens. Subcutaneous piperacillin or piperacillin plus oral beta-lactamase were administered 24 and 12 h before orogastric inoculation of piperacillin-resistant pathogens. Oral administration of beta-lactamase reduced piperacillin-associated alteration of the indigenous microflora and prevented overgrowth of pathogens.

Effects of Daptomycin, Linezolid, and Vancomycin on Establishment of Intestinal Colonization with Vancomycin-Resistant Enterococci and Extended-Spectrum-β-Lactamase-Producing Klebsiella pneumoniae in Mice

ABSTRACT In mice, vancomycin and linezolid treatment disrupted the anaerobic intestinal microflora, based on denaturing gradient gel electrophoresis analysis, and promoted colonization by Klebsiella pneumoniae and vancomycin-resistant enterococci. However, the effects varied depending on dose and duration of treatment. Daptomycin treatment did not disrupt the anaerobic microflora or promote either pathogen.

Effect of Carbapenem Administration on Establishment of Intestinal Colonization by Vancomycin-Resistant Enterococci and Klebsiella pneumoniae in Mice

ABSTRACT In a mouse model, ertapenem inhibited the anaerobic intestinal microflora and promoted overgrowth of enterococci, whereas imipenem-cilastatin had no effect on the indigenous microflora. Ertapenem, but not imipenem-cilastatin, promoted modest overgrowth of vancomycin-resistant enterococci when exposure occurred during treatment. Neither agent promoted colonization with extended-spectrum beta-lactamase-producing Klebsiella pneumoniae.

Emergence and Acquisition of Fluoroquinolone-Resistant Gram-Negative Bacilli in the Intestinal Tracts of Mice Treated with Fluoroquinolone Antimicrobial Agents

ABSTRACT After mice received orogastric administration of a fluoroquinolone-resistant Klebsiella pneumoniae strain, subcutaneous treatment with ciprofloxacin, levofloxacin, and moxifloxacin promoted persistent low-density colonization in 10% to 40% of the mice, whereas treatment with clindamycin consistently promoted high-density colonization. No emergence of fluoroquinolone-resistant gram-negative bacilli was detected in the mice during or after treatment with the fluoroquinolone antimicrobial agents.

Effect of a Selective Decontamination of the Digestive Tract Regimen Including Parenteral Cefepime on Establishment of Intestinal Colonization with Vancomycin-Resistant Enterococcus spp. and Klebsiella pneumoniae in Mice

ABSTRACT In mice, a selective decontamination of the digestive tract regimen consisting of orogastric tobramycin, polymyxin E, and amphotericin B in combination with subcutaneous cefepime inhibited gram-negative bacilli, including Klebsiella pneumoniae, and did not promote vancomycin-resistant Enterococcus spp. (VRE) colonization. However, concurrent administration of subcutaneous ampicillin-sulbactam resulted in promotion of VRE.

Perception vs Reality: Methicillin-Resistant Staphylococcus aureus Carriage Among Healthcare Workers at a Veterans Affairs Medical Center.

In a prevalence study of 209 healthcare workers, 18 (8.6%) and 13 (6.2%) carried methicillin-resistant Staphylococcus aureus in their nares or on their hands, respectively. However, 100 (62%) of 162 workers completing an associated survey believed themselves to be colonized, revealing a knowledge deficit about methicillin-resistant Staphylococcus aureus epidemiology. Infect. Control Hosp. Epidemiol. 2015;37(1):110-112.