Flocked nylon swabs versus RODAC plates for detection of multidrug-resistant organisms on environmental surfaces in intensive care units.

To compare two culture methods [nylon fiber flocked swabs with broth enrichment versus RODAC ('replicate organism detection and counting') plates] for recovery of multidrug-resistant organisms, 780 environmental surfaces in 63 rooms of patients on contact precautions in four intensive care units at one hospital were examined. Among sites that had at least one positive culture, swab culture with broth enrichment detected the target organisms more frequently than RODAC plates (37.5% vs 26.0%, P = 0.06). There was moderate agreement between the two methods (κ = 0.44) with agreement better for small or flat surfaces compared to large or irregular surfaces.

Post-flood measurement of fungal bio-aerosol in a resource-limited hospital: can the settle plate method be used?

The performance of the settle plate method (SPM) compared with the microbiological air sampler method (MAS) for post-flood fungal bio-aerosol (FB) measurement was evaluated in a Thai hospital. Compared with closed-ventilation units, open-ventilation units had significantly higher median FB level by SPM on days 3 and 5 of incubation (270 vs 90 colony-forming units (cfu)/m(3) and 420 vs 180 cfu/m(3), respectively). Strong correlations between SPM and MAS results on day 3 (r = 1.60, P < 0.001) and day 5 (r = 1.49, P = 0.002) of incubation suggested the utility of SPM for post-flood FB measurement in open-ventilation units in resource-limited situations.

A guide to interpreting economic studies in infectious diseases.

Healthcare providers continue to seek improved methods for preventing, detecting and treating diseases that affect human survival and quality of life. At the same time, there will always be financial constraints because of limited societal resources. Many of the discussions on how to provide economically sound solutions to this challenge have not fully engaged the input of clinicians in the field. The purpose of this review is to increase economic knowledge for clinicians. We cover healthcare cost elements and methods used to assign value to a health outcome. We outline the challenges in conducting economic studies in the field of infectious diseases. Finally, we discuss the meaning of efficiency from multiple perspectives, and how the concept of economic externalities applies to infectious diseases.

Interventional evaluation of environmental contamination by vancomycin-resistant enterococci: failure of personnel, product, or procedure?

It is not clear whether improvement in environmental decontamination is more efficiently achieved through changes in cleaning products, cleaning procedures, or performance of cleaning personnel. To assess the impact of cleaning performance on environmental contamination with vancomycin-resistant enterococci (VRE), we conducted a sequential trial in which a multifaceted environmental cleaning improvement intervention was introduced in a medical intensive care unit and respiratory step-down unit. The intervention included educational lectures for housekeepers and an observational programme of their activities without changes in cleaning products or written procedures. Following these interventions, the proportion of environmental sites cleaned improved from 49% to 85% (P<0.001); contamination of environmental sites declined from 21% to 8% (P<0.0001) before cleaning and from 13% to 8% (P<0.0001) after cleaning. The improved cleaning and contamination rates persisted in a washout period. In a multivariate model, cleaning thoroughness strongly influenced the degree of environmental contamination, with a 6% decline in VRE prevalence with every 10% increase in percentage of sites cleaned. These findings suggest that surface contamination with VRE is due to a failure to clean rather than to a faulty cleaning procedure or product.

Development of Daptomycin resistance in vivo in methicillin-resistant Staphylococcus aureus.

Daptomycin is a new lipopeptide antibiotic that is rapidly bactericidal against Staphylococcus aureus. We report daptomycin resistance and treatment failure in 2 patients with osteomyelitis due to methicillin-resistant S. aureus. Disk diffusion susceptibility testing failed to detect resistance. Daptomycin at high concentration retained bactericidal activity against resistant isolates.

Bowel colonization with resistant gram-negative bacilli after antimicrobial therapy of intra-abdominal infections: observations from two randomized comparative clinical trials of ertapenem therapy.

The selection of resistant gram-negative bacilli by broad-spectrum antibiotic use is a major issue in infection control. The aim of this comparative study was to assess the impact of different antimicrobial regimens commonly used to treat intra-abdominal infections on the susceptibility patterns of gram-negative bowel flora after completion of therapy. In two international randomized open-label trials with laboratory blinding, adults with complicated intra-abdominal infection requiring surgery received piperacillin-tazobactam (OASIS 1) or ceftriaxone/metronidazole (OASIS II) versus ertapenem for 4-14 days. Rectal swabs were obtained at baseline, end of therapy, and 2 weeks post-therapy. Escherichia coli and Klebsiella spp. were tested for production of extended-spectrum beta-lactamase (ESBL). Enterobacteriaceae resistant to the agent used were recovered from 19 of 156 (12.2%) piperacillin-tazobactam recipients at the end of therapy compared to 1 (0.6%) patient at baseline (p<0.001) in OASIS I, and from 33 of 193 (17.1%) ceftriaxone/metronidazole recipients at the end of therapy compared to 5 (2.6%) patients at baseline (p<0.001) in OASIS II. Ertapenem-resistant Enterobacteriaceae were recovered from 1 of 155 and 1 of 196 ertapenem recipients at the end of therapy versus 0 and 1 ertapenem recipients at baseline in OASIS I and II, respectively. Resistant Enterobacteriaceae emerged significantly less often during treatment with ertapenem than with the comparator in both OASIS I (p<0.001) and OASIS II (p<0.001). The prevalence of ESBL-producers increased significantly during therapy in OASIS II among 193 ceftriaxone/metronidazole recipients (from 4 [2.1%] to 18 [9.3%]) (p<0.001), whereas no ertapenem recipient was colonized with an ESBL-producer at the end of therapy in either study. Selection for imipenem-resistant Pseudomonas aeruginosa was uncommon in all treatment groups. In these studies, the frequency of bowel colonization with resistant Enterobacteriaceae substantially increased in patients treated with either piperacillin-tazobactam or ceftriaxone/metronidazole, but not in patients treated with ertapenem.

Impact of a fluoroquinolone formulary change on acquisition of quinolone-resistant gram-negative bacilli.

Rising rates of fluoroquinolone resistance in bacteria have been associated with increased fluoroquinolone use. In vitro data show differences in potency among fluoroquinolone antibiotics against gram-negative bacteria and have led to the hypothesis that rates of selection of resistant microorganisms may be affected by the choice of the specific fluoroquinolone. Because clinical data to prove this hypothesis are lacking, the aim of the present study was to determine rates of acquisition of quinolone-resistant gram-negative bacilli (QRGNB) in the fecal flora of medical intensive care unit patients before and after a formulary change from ciprofloxacin to levofloxacin. Unadjusted rate ratios for acquisition of QRGNB were 1.09 (95%CI, 1.02-1.16) for each day of ciprofloxacin use and 1.01 (95%CI, 0.87-1.17) for each day of levofloxacin use. Following adjustment for other antibiotic use, enteral feeding, APACHE II score, and nursing home admission, neither ciprofloxacin nor levofloxacin use was associated with acquisition of QRGNB. In conclusion, a formulary change from ciprofloxacin to levofloxacin was not significantly associated with an increased risk of acquisition of QRGNB.

Are active microbiological surveillance and subsequent isolation needed to prevent the spread of methicillin-resistant Staphylococcus aureus?

BACKGROUND: Infection-control strategies usually combine several interventions. The relative value of individual interventions, however, is rarely determined. We assessed the effect of daily microbiological surveillance alone (e.g., without report of culture results or isolating colonized patients) as an infection-control measure on the spread of methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA) in a medical intensive care unit (MICU). METHODS: Colonization of patients with MSSA and MRSA was assessed by cultures of nasal swabs obtained daily and, if a patient was intubated, by cultures of additional endotracheal aspirates. Pulsed-field gel electrophoresis was used to determine relatedness between MSSA or MRSA isolates in surveillance cultures (i.e., cultures of nasal swab specimens obtained daily) and those in clinical cultures (i.e., any other culture performed for clinical purposes). Adherence to infection-control measures by health care workers (HCWs) was determined by observations of HCW-patient interaction. RESULTS: During a 10-week period, surveillance cultures were performed for 158 patients. Fifty-five patients (34.8%) were colonized with MSSA, and 9 (5.7%) were colonized with MRSA. Sixty-two patients were colonized before admission to the hospital (53 had MSSA, and 9 had MRSA). Two patients appeared to have acquired MSSA in the MICU, but, on the basis of genotyping analysis, we determined that this was not the result of cross-acquisition. CONCLUSION: Surveillance cultures and genotyping of MRSA and MSSA isolates demonstrated the absence of cross-transmission among patients in the MICU, despite ongoing introduction of these pathogens. Reporting culture results and isolating colonized patients, as suggested by some guidelines, would have falsely suggested the success of such infection-control policies.

Risk factors for antibiotic-resistant infection and treatment outcomes among hospitalized patients transferred from long-term care facilities: does antimicrobial choice make a difference?

A prospective observational study of 153 patients transferred from long-term care facilities and admitted to acute-care hospitals who had microbiologically confirmed infections was undertaken to determine the risk factors, outcomes, and resource use associated with isolation of antibiotic-resistant bacteria (ARB). Eighty patients (52%) were infected with ARB. In multivariable logistic analysis, the presence of a feeding tube (odds ratio, 3.0) or polymicrobial infection (odds ratio, 4.6) was associated with isolation of ARB. Forty-nine percent of patients infected with ARB received an initial antibiotic regimen to which their isolate was not susceptible. Fifty-one percent of all patients had a change in their antibiotic regimen during their hospital course. For these patients, length of stay, number of days of antibiotic therapy, and cost of hospitalization were significantly higher. However, neither infection with ARB nor appropriateness of initial treatment regimen was significantly related to outcome or resource use.

The effect of renal dysfunction on antimicrobial use measurements.

The defined daily dose, a popular measurement of antimicrobial use, may underestimate the use of antimicrobials that are dose-adjusted in patients with renal insufficiency. To evaluate the effect of renal dysfunction on these measures, we performed a retrospective cohort study that involved patients receiving ceftriaxone, levofloxacin, or vancomycin, with use of defined daily doses and 2 methods based on therapy duration--stop-start days (i.e., entire therapy duration) and transaction days (i.e., unique therapeutic days). The vancomycin use rate for patients with renal insufficiency was 36% lower than that of patients with normal renal function for defined daily doses, and it was 23% lower for transaction days; for levofloxacin, there was a 27% rate reduction for the defined daily dose. No significant reduction was noted when the stop-start day method was used. Compared with the defined daily dose method, measures of therapy duration are less affected by renal function and may improve comparisons between populations.

Multi-hospital analysis of antimicrobial usage and resistance trends.

We report a pilot study comparing antimicrobial usage and antimicrobial resistance trends for prominent nosocomial pathogens between 1994-1996. A convenience sample of ten hospitals participated in this retrospective review. We found a large variation in antimicrobial use and resistance trends and that many hospitals did not have data readily available to evaluate drug usage and resistance rates. A significant strong positive correlation was observed between the usage of ceftazidime and the prevalence of ceftazidime resistant Pseudomonas aeruginosa (r = 0.8, p = 0.005) and of ceftazidime resistant Enterobacter species (r = 0.8, p = 0.02). The presence of antibiotic control policies correlated with lower rates of some resistant strains and less antibiotic use. Our findings can be a useful starting point for hospitals that want to systematically measure antimicrobial use and resistance. Hospital laboratories, pharmacies, and infection control departments must work together to develop databases that will facilitate such measurements.

HIV-related Pneumocystis carinii pneumonia in older patients hospitalized in the early HAART era.

OBJECTIVE: To determine whether older age continues to influence patterns of care and in-hospital mortality for hospitalized persons with HIV-related Pneumocystis carinii pneumonia (PCP), as determined in our prior study from the 1980s. DESIGN: Retrospective chart review. PATIENTS/SETTING: Patients (1,861) with HIV-related PCP at 78 hospitals in 8 cities from 1995 to 1997. MEASUREMENTS: Medical record notation of possible HIV infection; alveolar-arterial oxygen gradient; CD4 lymphocyte count; presence or absence of wasting; timely use of anti-PCP medications; in-hospital mortality. MAIN RESULTS: Compared to younger patients, patients > or =50 years of age were less likely to have HIV mentioned in their progress notes (70% vs 82%, P <.001), have mild or moderately severe PCP cases at admission (89% vs 96%, P <.002), receive anti-PCP medications within the first 2 days of hospitalization (86% vs 93%, P <.002), and survive hospitalization (82% vs 90%, P <.003). However, age was not a significant predictor of mortality after adjustment for severity of PCP and timeliness of therapy. CONCLUSIONS: While inpatient PCP mortality has improved by 50% in the past decade, 2-fold age-related mortality differences persist. As in the 1980s, these differences are associated with lower rates of recognition of HIV, increased severity of illness at admission, and delays in initiation of PCP-specific treatments among older individuals--factors suggestive of delayed recognition of HIV infection, pneumonia, and PCP, respectively. Continued vigilance for the possibility of HIV and HIV-related PCP among persons > or =50 years of age who present with new pulmonary symptoms should be encouraged.

The effect of glucagon-like peptide 2 on intestinal permeability and bacterial translocation in acute necrotizing pancreatitis.

BACKGROUND: Acute pancreatitis (AP) initiates a generalized inflammatory response that increases intestinal permeability and promotes bacterial translocation (BT). Impairment of the intestinal epithelial barrier is known to promote BT. Glucagon-like peptide 2 (GLP-2), a 33 residue peptide hormone, is a key regulator of the intestinal mucosa by stimulating epithelial growth. The purpose of this study was to determine whether GLP-2 decreases intestinal permeability and BT in AP. METHODS: To examine whether GLP-2 can decrease intestinal permeability and thereby decrease BT in acute necrotizing pancreatitis, 34 male Sprague-Dawley rats (200 to 300 g) were studied. AP was induced in group I and group II by pressure injection of 3% taurocholate and trypsin into the common biliopancreatic duct (1 mg/kg of body weight). The potent analog to GLP-2 called ALX-0600 was utilized. Group I rats received GLP-2 analog (0.1 mg/kg, SQ, BID) and group II rats received a similar volume of normal saline as a placebo postoperatively for 3 days. Group III and group IV received GLP-2 analog and placebo, respectively. At 72 hours postoperatively, blood was drawn for culture of gram-negative organisms. Specimens from mesenteric lymph nodes (MLN), pancreas and peritoneum were harvested for culture of gram-negative bacteria. Intestinal resistance as defined by Ohm's law was determined using a modified Ussing chamber to measure transepithelial current at a fixed voltage. A point scoring system for five histologic features that include intestinal edema, inflammatory cellular infiltration, fat necrosis, parenchymal necrosis, and hemorrhage was used to evaluate the severity of pancreatitis. Specimens from MLN, pancreas, jejunum, and ileum were taken for pathology. RESULTS: All group I and group II rats had AP. The average transepithelial resistance in group I was 82.8 Omega/cm(2) compared with 55.9 Omega/cm(2) in group II (P <0.01). Gram-negative BT to MLN, pancreas, and peritoneum was 80%, 0%, and 0%, respectively in group I compared with 100%, 30%, and 20% translocation in group II. CONCLUSION: GLP-2 treatment significantly decreases intestinal permeability in acute pancreatitis.

Colonization of skilled-care facility residents with antimicrobial-resistant pathogens.

OBJECTIVES: To determine the frequency of and risk factors for colonization of skilled-care unit residents by several antimicrobial-resistant bacterial species, methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococcus (VRE), or extended-spectrum-beta-lactamase-producing (ESBL-producing) (ceftazidime resistant) Klebsiella pneumoniae or Escherichia coli. DESIGN: Point-prevalence survey and medical record review. SETTING: The skilled-care units in one healthcare facility. PARTICIPANTS: 120 skilled-care unit residents. MEASUREMENTS: Colonization by each of the four antimicrobial-resistant pathogens during a point-prevalence survey, using rectal, nasal, gastrostomy-tube site, wound, and axillary cultures, June 1-3, 1998; 117 (98%) had at least one swab collected and 114 (95%) had a rectal swab collected. Demographic and clinical characteristics were evaluated as risk factors for colonization. All isolates were strain typed by pulsed-field gel electrophoresis of total genomic deoxyribonucleic acid. RESULTS: Of 117 participants, 50 (43%) were culture positive for > or =1 antimicrobial-resistant pathogen: MRSA (24%), ESBL-producing K. pneumoniae (18%) or E. coli (15%), and VRE (3.5%). Of 50 residents culture positive for any of these four antimicrobial-resistant species, 13 (26%) were colonized by more than one resistant species; only three (6%) were on contact-isolation precautions at the time of the prevalence survey. Risk factors for colonization varied by pathogen: total dependence on healthcare workers (HCWs) for activities of daily living (ADLs) and antimicrobial receipt for MRSA, total dependence on HCWs for ADLs for ESBL-producing K. pneumoniae, and antimicrobial receipt for VRE. No significant risk factors were identified for colonization by ESBL-producing E. coli. Among colonized patients, there was a limited number of strain types for MRSA (24 patients, 4 strain types) and ESBL-producing K. pneumoniae (21 patients, 3 strain types), and a high proportion of unique strain types for VRE (4 patients, 4 strain types) and FSBL-producing E. coli (17 patients, 10 strain types). CONCLUSION: A large unrecognized reservoir of skilled-care-unit residents was colonized by antimicrobial-resistant pathogens, and co-colonization by more than one target species was common. To prevent transmission of antimicrobial-resistant pathogens in long-term care facilities in which residents have high rates of colonization, infection-control strategies may need to be modified. Potential modifications include enhanced infection-control strategies, such as universal gloving for all or high-risk residents, or screening of high-risk residents, such as those with total dependence on HCWs for ADLs or recent antimicrobial receipt, and initiation of contact-isolation precautions for colonized residents.

Controlling antimicrobial resistance in hospitals: infection control and use of antibiotics.

Antimicrobial-drug resistance in hospitals is driven by failures of hospital hygiene, selective pressures created by overuse of antibiotics, and mobile genetic elements that can encode bacterial resistance mechanisms. Attention to hand hygiene is constrained by the time it takes to wash hands and by the adverse effects of repeated handwashing on the skin. Alcohol-based hand rubs can overcome the time problem and actually improve skin condition. Universal glove use could close gaps left by incomplete adherence to hand hygiene. Various interventions have been described to improve antibiotic use. The most effective have been programs restricting use of antibiotics and computer-based order forms for health providers.