Methicillin-resistant Staphylococcus aureus colonization of the groin and risk for clinical infection among HIV-infected adults

Data on the interaction between methicillin-resistant Staphylococcus aureus (MRSA) colonization and clinical infection are limited. During 2007–2008, we enrolled HIV-infected adults in Atlanta, Georgia, USA, in a prospective cohort study. Nares and groin swab specimens were cultured for S. aureus at enrollment and after 6 and 12 months. MRSA colonization was detected in 13%–15% of HIV-infected participants (n = 600, 98% male) at baseline, 6 months, and 12 months. MRSA colonization was detected in the nares only (41%), groin only (21%), and at both sites (38%). Over a median of 2.1 years of follow-up, 29 MRSA clinical infections occurred in 25 participants. In multivariate analysis, MRSA clinical infection was significantly associated with MRSA colonization of the groin (adjusted risk ratio 4.8) and a history of MRSA infection (adjusted risk ratio 3.1). MRSA prevention strategies that can effectively prevent or eliminate groin colonization are likely necessary to reduce clinical infections in this population.

Prevalence and risk factors associated with vancomycin-resistant Staphylococcus aureus precursor organism colonization among patients with chronic lower-extremity wounds in Southeastern Michigan

BACKGROUND

Of the 13 US vancomycin-resistant Staphylococcus aureus (VRSA) cases, 8 were identified in southeastern Michigan, primarily in patients with chronic lower-extremity wounds. VRSA infections develop when the vanA gene from vancomycin-resistant enterococcus (VRE) transfers to S. aureus. Inc18-like plasmids in VRE and pSK41-like plasmids in S. aureus appear to be important precursors to this transfer.

OBJECTIVE

Identify the prevalence of VRSA precursor organisms.

DESIGN

Prospective cohort with embedded case-control study.

PARTICIPANTS

Southeastern Michigan adults with chronic lower-extremity wounds.

METHODS

Adults presenting to 3 southeastern Michigan medical centers during the period February 15 through March 4, 2011, with chronic lower-extremity wounds had wound, nares, and perirectal swab specimens cultured for S. aureus and VRE, which were tested for pSK41-like and Inc18-like plasmids by polymerase chain reaction. We interviewed participants and reviewed clinical records. Risk factors for pSK41-positive S. aureus were assessed among all study participants (cohort analysis) and among only S. aureus-colonized participants (case-control analysis).

RESULTS

Of 179 participants with wound cultures, 26% were colonized with methicillin-susceptible S. aureus, 27% were colonized with methicillin-resistant S. aureus, and 4% were colonized with VRE, although only 17% consented to perirectal culture. Six participants (3%) had pSK41-positive S. aureus, and none had Inc18-positive VRE. Having chronic wounds for over 2 years was associated with pSK41-positive S. aureus colonization in both analyses.

CONCLUSIONS

Colonization with VRSA precursor organisms was rare. Having long-standing chronic wounds was a risk factor for pSK41-positive S. aureus colonization. Additional investigation into the prevalence of VRSA precursors among a larger cohort of patients is warranted.

Severe methicillin-susceptible Staphylococcus aureus infections associated with epidural injections at an outpatient pain clinic

BACKGROUND

Recent outbreaks in ambulatory care settings have highlighted infection control breaches as risk factors for disease transmission. In May 2009, 3 patients were hospitalized with severe methicillin-susceptible Staphylococcus aureus (MSSA) infections after receiving epidural injections at a West Virginia outpatient pain clinic.

METHODS

We conducted a retrospective cohort study evaluating clinic patients who received injections during a 3-week period. A case was defined as laboratory-confirmed infection or clinical evidence of infection ≤ 14 days after a patient received an injection. Infection control procedures were assessed. MSSA isolates from patient infections and clinic staff nasal swabs were genotyped by using pulsed-field gel electrophoresis.

RESULTS

Eight (7%) of 110 cohort patients met the case definition; 6 (75%) cases were laboratory confirmed. Eight (12%) of 69 patients who received epidural injections were case patients compared with none of the other 41 patients (P = .02). During procedures, staff use of face masks and preparation of patient skin were suboptimal; epidural injection syringes were reused to access shared medication vials. MSSA isolates from 2 patients and 1 staff member were indistinguishable by pulsed-field gel electrophoresis.

CONCLUSION

Infection control breaches likely facilitated MSSA transmission to patients receiving epidural injections. Adhering to correct infection control practices in ambulatory care settings is critical to prevent disease transmission.

StaphPlex system for rapid and simultaneous identification of antibiotic resistance determinants and Panton-Valentine leukocidin detection of staphylococci from positive blood cultures

Phenotypic methods take several days for identification and antimicrobial susceptibility testing of staphylococcal isolates after gram-positive cocci in clusters (GPCC) are observed in positive blood cultures. We developed and validated a StaphPlex system that amplifies and detects 18 gene targets simultaneously in 1 reaction for species-level identification of staphylococci, detection of genes encoding Panton-Valentine leukocidin (PVL), and antimicrobial resistance determinants of staphylococci. The StaphPlex system was compared to phenotypic methods for organism identification and antimicrobial resistance detection for positive blood culture specimens in which GPCC were observed. Among a total of 360 GPCC specimens, 273 (75.8%), 37 (10.3%), 37 (10.3%), 1 (0.3%), 3 (0.8%), and 9 (2.5%) were identified by StaphPlex as coagulase-negative Staphylococcus (CoNS), methicillin-resistant Staphylococcus aureus (MRSA), methicillin-susceptible S. aureus (MSSA), or mixed infections of CoNS and MRSA, CoNS and MSSA, or nonstaphylococci, respectively, with an overall accuracy of 91.7%. The 277 CoNS-containing specimens were further identified to the species level as containing 203 (73.3%) Staphylococcus epidermidis isolates, 10 (3.6%) Staphylococcus haemolyticus isolates, 27 (9.7%) Staphylococcus hominis isolates, 1 (0.4%) Staphylococcus lugdunensis isolate, and 36 (13.0%) other CoNS isolates, with an overall accuracy of 80.1% compared to an API STAPH test and CDC reference identification. Numerous very major errors were noticed when detection of aacA, ermA, ermC, tetM, and tetK was used to predict in vitro antimicrobial resistance, but relatively few major errors were observed when the absence of these genes was used to predict susceptibility. The StaphPlex system demonstrated 100% sensitivity and specificity, ranging from 95.5% to 100.0% when used for staphylococcal cassette chromosome mec typing and PVL detection. StaphPlex provides simultaneous staphylococcal identification and detection of PVL and antimicrobial resistance determinants within 5 h, significantly shortening the time needed for phenotypic identification and antimicrobial susceptibility testing.

Severe community-acquired pneumonia due to Staphylococcus aureus, 2003-04 influenza season

During the 2003-04 influenza season, 17 cases of Staphylococcus aureus community-acquired pneumonia (CAP) were reported from 9 states; 15 (88%) were associated with methicillin-resistant S. aureus (MRSA). The median age of patients was 21 years; 5 (29%) had underlying diseases, and 4 (24%) had risk factors for MRSA. Twelve (71%) had laboratory evidence of influenza virus infection. All but 1 patient, who died on arrival, were hospitalized. Death occurred in 5 (4 with MRSA). S. aureus isolates were available from 13 (76%) patients (11 MRSA). Toxin genes were detected in all isolates; 11 (85%) had only genes for Panton-Valentine leukocidin. All isolates had community-associated pulsed-field gel electrophoresis patterns; all MRSA isolates had the staphylococcal cassette chromosome mec type IVa. In communities with a high prevalence of MRSA, empiric therapy of severe CAP during periods of high influenza activity should include consideration for MRSA.

Prevalence of Staphylococcus aureus nasal colonization in the United States, 2001-2002

BACKGROUND

Staphylococcus aureus is a common cause of disease, particularly in colonized persons. Although methicillin-resistant S. aureus (MRSA) infection has become increasingly reported, population-based S. aureus and MRSA colonization estimates are lacking.

METHODS

Nasal samples for S. aureus culture and sociodemographic data were obtained from 9622 persons > or = 1 year old as part of the National Health and Nutrition Examination Survey, 2001-2002. After screening for oxacillin susceptibility, MRSA and selected methicillin-susceptible S. aureus isolates were tested for antimicrobial susceptibility, pulsed-field gel electrophoresis clonal type, toxin genes (e.g., for Panton-Valentine leukocidin [PVL]), and staphylococcal cassette chromosome mec (SCCmec) type I-IV genes.

RESULTS

For 2001-2002, national S. aureus and MRSA colonization prevalence estimates were 32.4% (95% confidence interval [CI], 30.7%-34.1%) and 0.8% (95% CI, 0.4%-1.4%), respectively, and population estimates were 89.4 million persons (95% CI, 84.8-94.1 million persons) and 2.3 million persons (95% CI, 1.2-3.8 million persons), respectively. S. aureus colonization prevalence was highest in participants 6-11 years old. MRSA colonization was associated with age > or = 60 years and being female but not with recent health-care exposure. In unweighted analyses, the SCCmec type IV gene was more frequent in isolates from participants of younger age and of non-Hispanic black race/ethnicity; the PVL gene was present in 9 (2.4%) of 372 of isolates tested.

CONCLUSIONS

Many persons in the United States are colonized with S. aureus; prevalence rates differ demographically. MRSA colonization prevalence, although low nationally in 2001-2002, may vary with demographic and organism characteristics.

Comparison of Routine Glove Use and Contact-Isolation Precautions to Prevent Transmission of Multidrug-Resistant Bacteria in a Long-Term Care Facility

OBJECTIVES

To compare routine glove use by healthcare workers for all residents, without use of contact-isolation precautions, with contact-isolation precautions for the care of residents who had vancomycin-resistant enterococci or methicillin-resistant Staphylococcus aureus isolated from a clinical culture.

DESIGN

Random allocation of two similar sections of the skilled-care unit to one of the infection-control strategies during an 18-month study period.

SETTING

Skilled-care unit of a 667-bed acute- and long-term care facility.

PARTICIPANTS

All residents present or admitted to the skilled-care unit from June 1, 1998, through December 7, 1999.

MEASUREMENTS

Resident acquisition of four antimicrobial-resistant organisms (methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, or extended-spectrum beta-lactamase-producing Klebsiella pneumoniae or Escherichia coli). All isolates were strain typed. The facility level costs associated with each strategy were estimated.

RESULTS

Resident acquisition of antimicrobial-resistant organisms was no different in the glove-use and isolation-precautions sections (31 episodes (1.5 per 1,000 resident-days) vs 38 episodes (1.6 per 1,000 resident-days)). Acquisition of either of two prevalent K. pneumoniae strains was more likely (P=.06) in residents in the isolation-precautions section. The estimated costs of contact-isolation precautions were 40% greater than those of routine glove use.

CONCLUSION

There was a similar frequency of transmission of antimicrobial-resistant bacteria in the two study sections; there was evidence for resident-to-resident K. pneumoniae transmission in the isolation-precautions section. Routine glove use for healthcare workers, which decreases resident social isolation and healthcare facility costs, may be preferable in many long-term care facilities.

Pulsed-field gel electrophoresis typing of oxacillin-resistant Staphylococcus aureus isolates from the United States: establishing a national database

Oxacillin-resistant Staphylococcus aureus (ORSA) is a virulent pathogen responsible for both health care-associated and community onset disease. We used SmaI-digested genomic DNA separated by pulsed-field gel electrophoresis (PFGE) to characterize 957 S. aureus isolates and establish a database of PFGE patterns. In addition to PFGE patterns of U.S. strains, the database contains patterns of representative epidemic-type strains from the United Kingdom, Canada, and Australia; previously described ORSA clonal-type isolates; 13 vancomycin-intermediate S. aureus (VISA) isolates, and two high-level vancomycin-resistant, vanA-positive strains (VRSA). Among the isolates from the United States, we identified eight lineages, designated as pulsed-field types (PFTs) USA100 through USA800, seven of which included both ORSA and oxacillin-susceptible S. aureus isolates. With the exception of the PFT pairs USA100 and USA800, and USA300 and USA500, each of the PFTs had a unique multilocus sequence type and spa type motif. The USA100 PFT, previously designated as the New York/Tokyo clone, was the most common PFT in the database, representing 44% of the ORSA isolates. USA100 isolates were typically multiresistant and included all but one of the U.S. VISA strains and both VRSA isolates. Multiresistant ORSA isolates from the USA200, -500, and -600 PFTs have PFGE patterns similar to those of previously described epidemic strains from Europe and Australia. The USA300 and -400 PFTs contained community isolates resistant only to beta-lactam drugs and erythromycin. Noticeably absent from the U.S. database were isolates with the previously described Brazilian and EMRSA15 PFGE patterns. These data suggest that there are a limited number of ORSA genotypes present in the United States.

Surface sampling methods for Bacillus anthracis spore contamination

During an investigation conducted December 17-20, 2001, we collected environmental samples from a U.S. postal facility in Washington, D.C., known to be extensively contaminated with Bacillus anthracis spores. Because methods for collecting and analyzing B. anthracis spores have not yet been validated, our objective was to compare the relative effectiveness of sampling methods used for collecting spores from contaminated surfaces. Comparison of wipe, wet and dry swab, and HEPA vacuum sock samples on nonporous surfaces indicated good agreement between results with HEPA vacuum and wipe samples. However, results from HEPA vacuum sock and wipe samples agreed poorly with the swab samples. Dry swabs failed to detect spores >75% of the time when they were detected by wipe and HEPA vacuum samples. Wipe samples collected after HEPA vacuum samples and HEPA vacuum samples collected after wipe samples indicated that neither method completely removed spores from the sampled surfaces.

Methicillin-resistant Staphylococcus aureus sepsis associated with the transfusion of contaminated platelets: a case report

BACKGROUND

Platelet transfusion-associated sepsis is usually due to donor skin flora introduced into the unit during phlebotomy. An unusual case of a platelet component contaminated with methicillin-resistant Staphylococcus aureus (MRSA) is reported.

CASE REPORT

A 54-year-old man, terminally ill with progressive non-Hodgkin's lymphoma, developed fever and hypotension during a platelet transfusion. He was receiving multiple antibiotics, including vancomycin. Blood cultures taken soon after transfusion were negative. An aliquot taken from the platelet pool grew MRSA at a count of 1.6 x 10(8) CFUs per mL. One of the individual bags constituting the pool showed MRSA at a count of 5.1 x 10(8) CFUs per mL. The patient died soon after the platelet transfusion. This case was reported to the FDA and submitted to the BaCon Study. The identity of the isolate and its methicillin resistance were confirmed by the CDC as part of the BaCon Study protocol. The source of contamination of the implicated unit could not be established with certainty.

CONCLUSION

The emergence of antimicrobial-resistant organisms poses additional challenges for the diagnosis and treatment of transfusion-associated sepsis. Measures to prevent or intercept the transfusion of contaminated platelets should be developed.

Vancomycin resistance among strains of Staphylococcus epidermidis: effects on adherence to silicone

Nosocomial device-related infections with Gram-positive cocci and their resistance to vancomycin are of increasing occurrence. We examined clinical isolates of relatively avirulent coagulase-negative staphylococci for their resistance to vancomycin and for their capabilities to adhere in vitro to medical grade silicone. Vancomycin resistance was found in 9 of 20 isolates, but there was no correlation between adherence capacity to silicone in the absence of vancomycin and vancomycin resistance for a given strain. Vancomycin in the medium, adsorbed to the surface of medical grade silicone or adsorbed on nongrowing cells, reduced adherence of representative Staphylococcus epidermidis to medical grade silicone.

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.

Vancomycin-intermediate Staphylococcus aureus in a home health-care patient

In June 2000, vancomycin-intermediate Staphylococcus aureus (VISA) was isolated from a 27-year-old home health-care patient following a complicated cholecystectomy. Two VISA strains were identified with identical MICs to all antimicrobials tested except oxacillin and with closely related pulsed-field gel electrophoresis types. The patient was treated successfully with antimicrobial therapy, biliary drainage, and reconstruction. Standard precautions in the home health setting appear successful in preventing transmission.

Determining the significance of coagulase-negative staphylococci isolated from blood cultures at a community hospital: a role for species and strain identification

OBJECTIVES

To determine the degree to which species identification or strain relatedness assessment of successive blood culture isolates of coagulase-negative staphylococci (CNS) may improve the clinical diagnosis of bloodstream infection (BSI).

SETTING

400-bed community hospital.

DESIGN

Prospective laboratory survey during which all CNS blood culture isolates obtained between mid-August 1996 and mid-February 1997 (study period) were saved and later identified to the species level; selected isolates were genotyped using pulsed-field gel electrophoresis at the Centers for Disease Control and Prevention (CDC). Retrospective review of medical records of 37 patients with multiple cultures positive for CNS.

RESULTS

During the study period, 171 patients had blood cultures positive for CNS; 130 had single positive cultures and 41 had > or =2 positive cultures. Of these 41, 23 (62%) were from patients with signs and symptoms of BSI according to CDC surveillance definitions. Species identification and strain clonality of CNS isolates from patients with > or =2 positives revealed 3 (13%) of the 23 patients did not have a consistent CNS species, and another 3 (13%) did not have a consistent genotype in the > or =2 positive cultures, suggesting that CNS from these patients probably were contaminants. Thus, species identification and strain clonality assessment reduced by 27% the number of patients with BSI diagnosed based on the presence of symptoms and > or =2 positive blood cultures.

CONCLUSIONS

Routine species identification and selected strain genotyping of CNS may reduce the misinterpretation of probable contaminants among patients with > or =2 positive blood cultures.

Comparison of the microbial barrier properties of a needleless and a conventional needle-based intravenous access system

BACKGROUND

Sporadic reports of increased infection rates involving concerning access systems, especially in home-care setting, have raised questions concerning the safety of all needleless systems. Addressing this concern, Baxter Healthcare Corporation and the Centers for Disease Control an d Prevention performed parallel laboratory studies comparing the microbial barrier properties of the Interlink (trademark of Baxter Healthcare Corporation, Deerfield, Ill) needleless system with a conventional intravenous access system.

METHODS

Studies of needleless and conventional systems evaluated fluid path contamination introduced through injection site septa, which were intentionally inoculated with high levels of bacteria and subsequently punctured with a without alcohol swabbing disinfection before access.

RESULTS

With disinfection, the combined effects of the disinfection technique and the barrier properties of the septa prevented the transfer of organisms into the fluid path in 94% to 96% of needleless test articles and 96% to 100% of conventional test articles. Without disinfection, the barrier properties of the septa alone prevented the transfer of organisms into the fluid path in 20% to 69% of needleless test article and 10% to 28% of conventional test articles.

CONCLUSIONS

The data demonstrate the needless system performs as well as the conventional intravenous access system with respect to the risk of microbial contamination and reinforce the need for appropriate septum disinfection before accessing either system.

Characterization of staphylococci with reduced susceptibilities to vancomycin and other glycopeptides

During the last several years a series of staphylococcal isolates that demonstrated reduced susceptibility to vancomycin or other glycopeptides have been reported. We selected 12 isolates of staphylococci for which the vancomycin MICs were > or =4 microg/ml or for which the teicoplanin MICs were > or =8 microg/ml and 24 control strains for which the vancomycin MICs were < or =2 microg/ml or for which the teicoplanin MICs were < or =4 microg/ml to determine the ability of commercial susceptibility testing procedures and vancomycin agar screening methods to detect isolates with reduced glycopeptide susceptibility. By PCR analysis, none of the isolates with decreased glycopeptide susceptibility contained known vancomycin resistance genes. Broth microdilution tests held a full 24 h were best at detecting strains with reduced glycopeptide susceptibility. Disk diffusion did not differentiate the strains inhibited by 8 microg of vancomycin per ml from more susceptible isolates. Most of the isolates with reduced glycopeptide susceptibility were recognized by MicroScan conventional panels and Etest vancomycin strips. Sensititre panels read visually were more variable, although with some of the panels MICs of 8 microg/ml were noted for these isolates. Vitek results were 4 microg/ml for all strains for which the vancomycin MICs were > or =4 microg/ml. Vancomycin MICs on Rapid MicroScan panels were not predictive, giving MICs of either < or =2 or > or =16 microg/ml for these isolates. Commercial brain heart infusion vancomycin agar screening plates containing 6 microg of vancomycin per ml consistently differentiated those strains inhibited by 8 microg/ml from more susceptible strains. Vancomycin-containing media prepared in-house showed occasional growth of susceptible strains, Staphylococcus aureus ATCC 29213, and on occasion, Enterococcus faecalis ATCC 29212. Thus, strains of staphylococci with reduced susceptibility to glycopeptides, such as vancomycin, are best detected in the laboratory by nonautomated quantitative tests incubated for a full 24 h. Furthermore, it appears that commercial vancomycin agar screening plates can be used to detect these isolates.

Microbiologic evaluation of needleless and needle-access devices

OBJECTIVE

This study was carried out to determine whether needleless intravenous access devices are more likely to allow microorganisms to enter the fluid pathway than intravenous needle-access devices.

METHODS

A laboratory study was conducted with two needleless and one intravenous needle-access devices and Enterococcus faecium as a bacterial challenge. Inocula of E. faecium were prepared on the basis of the numerical estimates of 1000 to 10,000 colony-forming units (CFU)/cm2 of bacterial flora on dry regions of skin (arms, legs, and hands). The septum of each access device was inoculated with 10 to 20 microliters of a 10(4) to 10(5) CFU/ml challenge suspension, which was allowed to dry on the surface of the septum. In the first part of the experiment, the needleless or needle-access cannula of each device was used to puncture the corresponding septum without previously disinfecting the top of the septum. In the second part, the contaminated septum was punctured after disinfecting the septum with a 70% isopropyl alcohol wipe. After each puncture, trypticase soy broth was flushed through the fluid pathway of the intravenous access device, collected, and cultured by the membrane filtration technique. The septum of each injection-site cap and the needleless or needle-access cannula were sampled with sterile premoistened swabs. Swabs were cultured on blood agar plates.

RESULTS

The rate of fluid pathway contamination was 100% (40/40) for one of the needleless intravenous access devices and 80% (20/25) for the other when septa were contaminated with E. faecium and not disinfected before puncture. The rate for the intravenous needle-access device was 72% (18/25). When the septa of the three different devices tested were disinfected with 70% isopropyl alcohol, E. faecium was isolated on only one septum from all devices tested in part two (1/74, 1.3%).

CONCLUSIONS

These laboratory studies demonstrate that there is no statistically significant difference in the rate of fluid pathway contamination between needleless and intravenous needle-access devices. However, if the septa of either needleless or needle systems are not disinfected before puncture, a high rate of fluid pathway contamination may occur.

The source of coagulase-negative staphylococci in the Endophthalmitis Vitrectomy Study. A comparison of eyelid and intraocular isolates using pulsed-field gel electrophoresis

OBJECTIVE

To determine the species distribution of coagulase-negative staphylococci (CoNS) in patients with endophthalmitis and to ascertain whether the patient's own flora was a major source of postoperative endophthalmitis following cataract extraction.

METHODS

In a 4-year multicenter prospective study, 524 bacterial isolates were submitted from 225 Endophthalmitis Vitrectomy Study patients. From the 524 isolates, 250 represented CoNS cultured from the anterior chamber, the vitreous, or both of the 225 patients. Where possible, paired isolates from an individual patient's eyelid and intraocular compartment(s) were studied by pulsed-field gel electrophoresis, an established molecular strain-typing technique.

RESULTS

From all sites the most frequently isolated CoNS were Staphylococcus epidermidis (81.9%) and Staphylococcus lugdunensis (5.9%). Where analysis was possible, eyelid isolates were indistinguishable from intraocular isolates in 71 (67.7%) of 105 comparisons. Non-S epidermidis CoNS caused postoperative endophthalmitis in 5 patients. Four of the 5 had postoperative endophthalmitis caused by S lugdunensis and 1 by Staphylococcus haemolyticus.

CONCLUSIONS

Coagulase-negative staphylococci from the patient's periocular skin flora play a significant role in causing intraocular infections, and non-S epidermidis CoNS play a small but significant role. These results reinforce the necessity to follow stringent surgical site preparation prior to eye surgery.

Potential hazards of deionization systems used for water purification in hemodialysis

This study was conducted to determine the efflux of specific ions, including fluoride, from a deionization (DI) water purification system (WPS) when the WPS was operated beyond exhaustion of the DI resin. Effluent from the DI WPS was monitored for resistivity, total dissolved solids, pH, and concentrations of silica, fluoride, potassium, and sodium. After 16,000 L of water was purified, the resistivity declined to 0.492 omega Ohm-cm, and silica was released from the DI WPS. Fluoride ions were released after an additional 8,000 L water was treated, and the resistivity fell to 0.07 omega Ohm-cm. The fluoride efflux reached a peak of 32 mg/L, 28 times greater than the original fluoride concentration in the city water. Sodium and potassium ions were released after approximately 26,000 and 32,000 L of water had been treated and reached peaks of 76 and 47 mg/L, respectively. This study confirms that the minimum resistivity standard of 1 omega Ohm-cm for DI water used for hemodialysis should provide an adequate safety margin. Once resistivity fell to 1 omega Ohm-cm, more than 8,000 L of water was treated before fluoride efflux occurred. Accordingly, hemodialysis centers should be attentive to the calculated capacity of their DI WPS and reliably monitor the resistivity to prevent patient illness related to exhaustion of DI resins.

The effects of endotoxin-contaminated dialysate and polysulfone or cellulosic membranes on the release of TNF alpha during simulated dialysis

Simulated dialysis of whole blood was used to determine whether membrane factors (biocompatibility), endotoxin (ET) membrane diffusion, or transmembrane monocyte-ET interactions would stimulate tumor necrosis factor (TNF alpha) release. Whole blood containing EDTA and aprotinin was recirculated in the blood compartment of hollow fiber dialyzers containing either regenerated cellulose or polysulfone membranes. ET-free and ET-spiked dialysate were recirculated consecutively in the dialysate compartment for 30 min each. Blood and dialysate samples were collected at to and after each 30 min of simulated dialysis for determination of TNF alpha and ET concentrations. TNF alpha was not detected in any blood samples collected after simulated dialysis with regenerated cellulose (RC) membranes and ET-free or ET-spiked dialysate. However, blood ET concentrations, as determined by the Limulus amebocyte lysate (LAL) assay, increased in RC dialyzers after each 30 min of simulated dialysis even with ET-free dialysate. Since TNF alpha was not detected in these blood samples, the material detected by the LAL assay probably was not ET but an LAL-reactive material. After simulated dialysis with polysulfone dialyzers and ET-free dialysate, TNF alpha and ET were not detected in blood samples. ET also was not detected in blood samples after dialysis with ET-spiked dialysate. However, TNF alpha was detected in 7 of 13 (54%) of the blood samples following the 500 ng/ml of ET dialysate spike. TNF alpha release during simulated dialysis with polysulfone membranes and ET-contaminated dialysate may be due to transmembrane stimulation of circulating mononuclear cells and not diffusion of ET across the membrane.

An outbreak of pyrogenic reactions in chronic hemodialysis patients associated with hemodialyzer reuse

In February 1992, 22 patients undergoing chronic hemodialysis at an outpatient dialysis center experienced pyrogenic reactions (PR). The PR rate was significantly greater (p < 0.001) during the epidemic (February 3-5) than the pre-epidemic period (November 1, 1992-February 1, 1992). All patients with PR used dialyzers that had been manually reprocessed either on February 1 or 3. These dialyzers contained up to 120.8 EU/ml of endotoxin in the blood compartment. The only dialyzer reprocessed before February 1 that was available for analysis was found to contain no detectable endotoxin, while dialyzers reprocessed during the epidemic period contained a median endotoxin concentration of 52.8 EU/ml. The bioburden of water used to prepare dialysate was in excess of the Association for the Advancement of Medical Instrumentation (AAMI) standard for water, < or = 200 colony forming units (CFU)/ml. Samples of treated water collected in the reuse area were within AAMI standards at the time of the investigation (February 11 and February 26), but before the investigation, water samples were assayed with a culture method that could not detect microbial concentrations below 10(3) CFU/ml. In addition, the treated water feed line to the disinfectant container may never have been disinfected. However, no samples were collected from this line during the investigation. This outbreak emphasizes the need to use water that meets the AAMI bacteriologic and endotoxin standards of < or = to 200 CFU/ml and/or 5 EU/ml, respectively, for reprocessing hemodialyzers nad to ensure that appropriate culture techniques are used for treated water dialysate.

Potency of endotoxin from bicarbonate dialysate compared with endotoxins from Escherichia coli and Shigella flexneri

Endotoxin is a potent activator of the complement system and other host immunoregulators, including the cytokines, tumor necrosis factor alpha, interleukin-1 beta, and interleukin-6. In this study, the potency of an endotoxin from bicarbonate dialysate was compared with endotoxins from two enteric microorganisms, Shigella flexneri and Escherichia coli. Endotoxin concentrations were standardized for the three endotoxins by use of the Limulus amebocyte lysate turbidimetric assay. Endotoxin potency was assessed by the comparative plasma concentrations of tumor necrosis factor alpha, interleukin-1 beta, and interleukin-6 after an in vitro whole-blood challenge by each type of endotoxin. Blood collected from 10 hemodialysis patients was spiked with 0.1, 1, and 10 ng/mL of E. coli and Shigella endotoxin and with 1 and 10 ng/mL of bicarbonate dialysate endotoxin. After incubation, plasma was separated and frozen at -70 degrees C until assayed for cytokine concentrations. Dialysate endotoxin was found to be 10 to 100 times less potent than E. coli and Shigella endotoxins. It was concluded that there are significant differences in the potency of endotoxins from different strains of bacteria and that these differences should be noted when designing or evaluating studies on the clinical effects of endotoxins in hemodialysis settings.

Bloodstream infections in neonatal intensive care unit patients: results of a multicenter study

For identification of risk factors for bloodstream infection (BSI) among neonatal intensive care unit patients, prospective 6-month studies in three neonatal intensive care units were conducted. BSI was diagnosed in 42 of 376 (11.2%) enrolled infants. Pathogens included coagulase-negative staphylococci, Candida sp., Group B streptococci and Gram-negative species. Patients with BSIs were more likely to die during their neonatal intensive care unit stay than were patients who did not acquire BSIs (6 of 42 vs. 11 of 334, P = 0.007). BSI rate was highest in infants with birth weight < 1500 g (relative risk (RR) = 6.8, P < 0.001), those treated with H-2 blockers (RR = 4.2, P < 0.001) or theophylline (RR = 2.8, P < 0.001) and those with admission diagnoses referable to the respiratory tract (RR = 3.7, P < 0.001). Infants who developed BSI were more severely ill on admission than other infants (median physiologic stability index 13 vs. 10 (P < 0.001) and were of lower gestational age (28 vs. 35 weeks, P < 0.001). In logistic regression analysis, risk of BSI was independently associated only with very low birth weight, respiratory admission diagnoses and receipt of H-2 blockers. Risk of isolation of a pathogen from blood culture was independently associated with Broviac, umbilical vein or peripheral venous catheterization > 10, 7 or 3 days, respectively, at one insertion site. Rate of isolation of a pathogen was higher (9 of 59 (15%)) within 48 hours of a measurable serum interleukin 6 concentration than an interleukin 6 level of 0 pg/ml (10 of 159 (6%), P = 0.04).(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of uremia on tumor necrosis factor-alpha release after an in vitro whole-blood endotoxin challenge

Uremia has been associated with immunologic aberrations, including anergy, increased susceptibility to infections, and reduced phagocytic activity of polymorphonuclear leukocytes. In this study, cytokine release in uremic and nonuremic blood after in vitro endotoxin stimulation was studied. Blood from nonuremic controls, chronic renal failure patients not on dialysis, and chronic hemodialysis patients predialysis and postdialysis was spiked with 10 ng/mL of Escherichia coli endotoxin and incubated for 2 and 26 h. Plasma tumor necrosis factor-alpha (TNF alpha) concentrations were determined by ELISA after each incubation period. To further study which uremic blood component may be responsible for enhanced release of TNF alpha, plasma and cellular components of chronic renal failure patients and controls were switched and then given an in vitro endotoxin stimulation (1 ng/mL). It was found that (1) TNF alpha release is enhanced by uremia and is exacerbated with progressive declines in renal function, (2) enhanced TNF alpha release is related to a blood cellular phenomenon induced by uremia, and (3) enhanced TNF alpha release in hemodialysis patients is associated with a prolonged stimulation and/or reduced plasma elimination of TNF alpha.

Patient cytokine response in transfusion-associated sepsis

Cytokine concentrations in plasma from patients transfused with packed erythrocytes contaminated with gram-negative bacilli were measured. Cytokine concentrations in posttransfusion plasma were significantly elevated. A difference in cytokine patterns between survivors and a nonsurvivor was observed.

Cytokine kinetics in an in vitro whole blood model following an endotoxin challenge

Whole blood and peripheral blood mononuclear cell (PBMC) culture models have been used to study cytokine stimulation and release in vitro. In this study, we characterize the kinetics of the interleukins (IL-1 beta), (IL-6), (IL-8), and tumor necrosis factor-alpha (TNF-alpha) following an endotoxin (ET) challenge using our in vitro whole blood model. Whole blood samples from 10 healthy volunteers were studied. All cytokines were measured by enzyme-linked immunosorbent assay. Peak concentrations of TNF-alpha occurred 2 h after ET challenge followed by a rapid decline in free plasma TNF-alpha concentration (half-life 18.2 min). IL-1 beta was not significantly elevated until 4 h after ET challenge. IL-8 was elevated 1 h after ET challenge. IL-6 concentration exhibited a biphasic peak occurring at 6 and 74 h after ET challenge. We conclude that (1) our whole blood in vitro model produces cytokine release kinetics similar to those reported in vivo, and (2) the presence of either binding proteins or cellular metabolism of TNF-alpha in whole blood produces a similar plasma half-life to that observed in vivo.

A prospective study of pyrogenic reactions in hemodialysis patients using bicarbonate dialysis fluids filtered to remove bacteria and endotoxin

Pyrogenic reactions (PR) are a well-recognized complication of hemodialysis and have been associated with dialyzer reuse, high-flux dialysis, and bicarbonate dialysate. However, the roles of bacteria and endotoxin in dialysate for producing PR are not well defined. To determine the effect of removing most bacteria and endotoxin from the dialysate on the incidence of PR, a cohort of chronic hemodialysis patients receiving high-flux, high-efficiency, or conventional hemodialysis at three centers with bicarbonate dialysis fluids that had been filtered with a polysulfone high-flux hemodialyzer was prospectively studied. Unfiltered bicarbonate concentrate had median bacterial and endotoxin concentrations of 479,000 CFU/mL and 39,800 pg/mL, respectively. After filtration of the bicarbonate concentrate at the central proportioner, dialysate had a median 9.2 CFU/mL of bacteria and 17.8 pg/mL of endotoxin. Dialysate filtered at individual proportioning dialysis machines had a median 0.001 CFU/mL of bacteria and 0.19 pg/mL of endotoxin. Nine PR were identified among 303 patients after 28,007 hemodialysis treatments (0.3 PR/1,000 treatments). The rate of PR was similar for the three hemodialysis treatment modalities and for first-use compared with reused dialyzers. Although the PR rate in this study was lower (P = 0.046) than the PR rate of a previous study with unfiltered dialysis fluids (0.7 PR/1,000 treatments), it represents a difference of only 10 PR in over 28,000 treatments. It was concluded that filtration of hemodialysis fluids is efficacious in removing bacterial and endotoxin contamination and can result in a lower incidence of PR in patients receiving high-flux, high-efficiency, or conventional hemodialysis.

Prestorage removal of Yersinia enterocolitica from red cells with white cell-reduction filters

Prestorage removal of phagocytic white cells (WBCs) may increase the survivability of contaminating bacteria in units of stored red cells. Fourteen units of whole blood were inoculated with 65 colony-forming units per mL of Yersinia enterocolitica (serotype O:3) and processed into AS-3-preserved red cells. Five red cell units were filtered with a prototype third-generation filter and five red cell units with a second generation filter. WBC reduction was performed on the day of collection. Four red cell units were not filtered. Three noninoculated whole blood units served as negative controls; two were filtered (one with each type of WBC-reduction filter) and one remained unfiltered. All red cell units were then stored at 4 degrees C for 42 days. One of the five filtered red cell units (20%) in each filter group supported growth of Y. enterocolitica. In contrast, 4 (100%) of 4 unfiltered inoculated red cell units had growth (p = 0.04). Overall, 2 (20%) of 10 units of WBC-reduced red cells supported the growth of Y. enterocolitica, as compared to 100 percent of unfiltered red cell units after inoculation (p = 0.015). Bacterial contamination was not detected in any of the three noninoculated units. It can be concluded that prestorage WBC filtration significantly reduces the potential for growth of Y. enterocolitica in red cells stored at 4 degrees C for 42 days.

Bacteriologic and endotoxin analysis of salvaged blood used in autologous transfusions during cardiac operations

Autologous blood transfusion is a common method of reducing the need for heterologous blood transfusion during cardiac operations. Recently we investigated an outbreak of severe, nonsurgical postoperative bleeding among patients undergoing heart operations and receiving intraoperative transfusion of blood from a cell conservation device (Cell Saver System, Haemonetics Corp., Braintree, Mass.). As a result of this investigation, we conducted a prospective study to determine if bacterial or endotoxin contamination of the blood collected in the Cell Saver System and used for reinfusion during heart operations contributes to postoperative bleeding complications. Patients' blood samples were collected immediately before operation, at the end of cardiopulmonary bypass, 1 hour postoperatively, and from the Cell Saver System. All blood samples were cultured for bacteria, and all plasma samples were assayed for endotoxin. Preoperatively all patients having heart operations were without signs of infection, 33 of 37 blood cultures taken were negative, and none of the plasma samples had detectable endotoxin. After discontinuance of cardiopulmonary bypass but before delivery of blood from the Cell Saver System, bacteria and endotoxin were detected in 11 of 36 (30.6%) and five of 35 (14.3%) of the patients' blood samples, respectively. The blood aspirated from the open chest and collected by the Cell Saver System was culture positive in 30 of 31 (96.8%) samples, and seven of 29 (24.1%) contained endotoxin. One of 28 blood samples collected 1 hour postoperatively was culture positive, and five of 25 samples contained endotoxin. Of 61 total microorganisms isolated, 50 (82%) were coagulase-negative staphylococci, four (6.6%) aerobic diphtheroids, five (8.2%) anaerobic "diphtheroids" (Propionibacterium acnes), and two (3.2%) gram-negative bacilli. Plasma endotoxin concentrations ranged from 10 to 765 pg/ml. No signs of endotoxemia or unusual bleeding were observed intraoperatively or postoperatively in any of the 38 patients. Although blood collected in the Cell Saver System and used for reinfusion during heart operations often was contaminated with gram-positive bacterial commensals of the skin and low concentrations of endotoxin, no adverse effects were noted in the patients.

Pyrogenic reactions in patients receiving conventional, high-efficiency, or high-flux hemodialysis treatments with bicarbonate dialysate containing high concentrations of bacteria and endotoxin

High-efficiency (HE) and high-flux (HF) hemodialysis are becoming increasingly popular methods for treating patients with chronic renal failure because they reduce the time required for dialysis treatment. HF and HE dialyzers require bicarbonate dialysate, often prepared from concentrates that can support bacterial growth with endotoxin production. There is a concern that endotoxins or bacteria may cross or interact at the membranes of these dialyzers, triggering the release of endogenous pyrogens (cytokines) by peripheral blood mononuclear cells to cause pyrogenic reactions (PR). To determine the incidence of PR and to examine the association between PR and levels of bacteria and endotoxin in dialysate, a cohort of patients receiving conventional, HE, or HF hemodialysis with bicarbonate dialysate and reprocessed dialyzers at three dialysis centers during a 12-month period was studied prospectively. All dialyzers underwent a test of membrane integrity before use. A total of 19 PR were identified among 18 patients in 26,877 hemodialysis treatments (0.7 PR/1,000 treatments). There was no significant difference in PR rates by treatment modality: conventional, 0.5 per 1,000 (7 PR/13,123 treatments) versus HE, 0.9 per 1,000 (9 PR/11,345) versus HF, 1.2 per 1,000 (3 PR/2,409) (P = 0.21; chi 2 test). Throughout the study period, bacterial counts for dialysate at each center significantly exceeded the Association for the Advancement of Medical Instrumentation's (AAMI) microbiologic standards for dialysate of less than 2,000 CFU/mL (mean, 19,000 CFU/mL), but water used in the reuse of dialyzers tested less than 200 CFU/mL.(ABSTRACT TRUNCATED AT 250 WORDS)

Lack of plasma interleukin-1 beta or tumor necrosis factor-alpha elevation during unfavorable hemodialysis conditions

Plasma interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) were determined by ELISA in 17 healthy controls, 23 HD patients, 10 continuous ambulatory peritoneal dialysis patients, and 15 chronic renal failure patients, as well as in 2 HD patients experiencing pyrogenic reactions. Another group of 10 chronic HD patients were dialyzed for 2.5 h, 5 with first-use Cuprophan membranes and 5 with first-use high-flux cellulose triacetate membranes. The mean bacterial and endotoxin concentrations of the dialysate used for HD treatments during the study period were 18,440 +/- 530 CFU/mL (mean +/- SEM) and 976 +/- 205 pg/mL, respectively. Blood specimens were obtained intradialysis and postdialysis for cytokine assay and were incubated to augment cytokine production. There was no difference in plasma IL-1 beta or TNF-alpha concentrations among the healthy controls, continuous ambulatory peritoneal dialysis patients, chronic renal failure patients, or HD patients. Neither cytokine increased significantly during or after HD. Two patients experiencing pyrogenic reactions had plasma TNF-alpha concentrations of 537 and 413 pg/mL, compared with matched controls of 6 and 0 pg/mL. Il-1 beta concentration did not differ from controls. We conclude that: (1) plasma IL-1 beta and TNF-alpha are not chronically elevated in chronic renal failure, continuous ambulatory peritoneal dialysis, or HD patients; (2) HD with new Cuprophan or cellulose triacetate membranes and high concentrations of dialysate endotoxin and bacteria does not cause elevation of circulating IL-1 beta or TNF-alpha; and (3) pyrogenic reactions might be mediated by TNF-alpha.

Enhanced release of TNF-alpha, but not IL-1 beta, from uremic blood after endotoxin stimulation

Aberrant immunologic host defenses associated with uremia may be a cause of the high incidence of sepsis in chronic hemodialysis (CHD) patients. This investigation determined the cytokine response of blood from five nondialyzed chronic renal failure (CRF) patients, five CHD patients, and five healthy controls (HC) after in vitro stimulation with 1 ng/ml Escherichia coli 0113 endotoxin. Concentrations of the cytokines TNF-alpha and IL-1 beta were determined by ELISA and were similar in all baseline and unspiked samples. TNF-alpha concentrations in CRF and CHD spiked samples were similar to each other but significantly greater (p less than 0.01) than in HC spiked samples. IL-1 beta concentrations in CRF, CHD, and HC-spiked samples were not significantly different. We conclude that CRF and CHD patients have enhanced TNF-alpha response, which may be related to uremia and not dialysis-related factors. Uremia does not potentiate IL-1 beta release.

Microbial growth and endotoxin production in the intravenous anesthetic propofol

OBJECTIVE

In this study, we measured microbial growth and endotoxin production in the intravenous anesthetic propofol using 10 different microbial strains; 6 isolated from outbreak cases and 4 from laboratory stock cultures.

DESIGN

In each trial, endotoxin-free glass tubes containing 10 ml propofol were inoculated with 10(0)-10(3) CFU/ml of the test organism and incubated at 30 degrees C for 72 hours.

SETTING

In May and June 1990, the Centers for Disease Control received reports of 5 outbreaks in 5 states of postsurgical patient infections and/or pyrogenic reactions. Epidemiologic and laboratory investigations implicated extrinsic contamination of an intravenous anesthetic, propofol, as the probable source of these outbreaks.

RESULTS

After 24 hours, 9 of the 10 cultures increased in viable counts by 3 to 6 logs. At least 1 ng/ml of endotoxin was produced within 24 hours by Escherichia coli, Enterobacter cloacae, and Acinetobacter calcoaceticus subspecies anitratus.

CONCLUSIONS

Propofol can support rapid microbial growth and endotoxin production. To avoid infectious complications, scrupulous aseptic technique should be used when preparing or administering this anesthetic.