Transmission of SARS and MERS coronaviruses and influenza virus in healthcare settings: the possible role of dry surface contamination.

Viruses with pandemic potential including H1N1, H5N1, and H5N7 influenza viruses, and severe acute respiratory syndrome (SARS)/Middle East respiratory syndrome (MERS) coronaviruses (CoV) have emerged in recent years. SARS-CoV, MERS-CoV, and influenza virus can survive on surfaces for extended periods, sometimes up to months. Factors influencing the survival of these viruses on surfaces include: strain variation, titre, surface type, suspending medium, mode of deposition, temperature and relative humidity, and the method used to determine the viability of the virus. Environmental sampling has identified contamination in field-settings with SARS-CoV and influenza virus, although the frequent use of molecular detection methods may not necessarily represent the presence of viable virus. The importance of indirect contact transmission (involving contamination of inanimate surfaces) is uncertain compared with other transmission routes, principally direct contact transmission (independent of surface contamination), droplet, and airborne routes. However, influenza virus and SARS-CoV may be shed into the environment and be transferred from environmental surfaces to hands of patients and healthcare providers. Emerging data suggest that MERS-CoV also shares these properties. Once contaminated from the environment, hands can then initiate self-inoculation of mucous membranes of the nose, eyes or mouth. Mathematical and animal models, and intervention studies suggest that contact transmission is the most important route in some scenarios. Infection prevention and control implications include the need for hand hygiene and personal protective equipment to minimize self-contamination and to protect against inoculation of mucosal surfaces and the respiratory tract, and enhanced surface cleaning and disinfection in healthcare settings.

Asymptomatic carriage of toxigenic Clostridium difficile by hospitalized patients.

Asymptomatic carriage of Clostridium difficile is common in hospitals, but the risk for transmission by carriers is unclear. In this point prevalence culture survey of asymptomatic hospitalized patients, 18 of 149 (12%) were carriers of toxigenic C. difficile. By comparison with C. difficile infection (CDI) patients, the prevalence of skin and/or environmental contamination was significantly lower in asymptomatic carriers (3/18, 17% versus 5/6, 83%; P = 0.007), but carriers outnumbered CDI patients in the hospital by a factor of 3 to 1. These data suggest that asymptomatic carriers have the potential to contribute to C. difficile transmission in hospitals.

Evaluation of a commercial real-time polymerase chain reaction assay for detection of environmental contamination with Clostridium difficile.

Contaminated environmental surfaces are an important source for transmission of Clostridium difficile. However, there are no efficient and easy methods to assess contamination. The performance of a commercial real-time polymerase chain reaction (PCR) assay was evaluated for detection of environmental toxigenic C. difficile in comparison with anaerobic culture followed by toxin testing of isolates. For 66 sites sampled, PCR had a sensitivity of 17.39%, specificity 100%, positive predictive value 100% and negative predictive value 69.35%. Increasing the PCR cycle threshold (CT) value to 45 increased sensitivity to 52% without decreasing specificity. The commercial PCR assay is not sufficiently sensitive for environmental monitoring, but improved sensitivity might be possible through CT value modification.

Clinical outcomes, safety, and pharmacokinetics of OPT-80 in a phase 2 trial with patients with Clostridium difficile infection.

OPT-80, a novel, minimally absorbed macrocycle, is a candidate treatment option for Clostridium difficile infection (CDI) based on cure without recurrence of CDI in the hamster challenge model, good in vitro activity against C. difficile, and relative sparing of commensal gram-negative anaerobes. In this open-label, dose-ranging clinical trial, 48 evaluable subjects were randomized to receive either 50, 100, or 200 mg of OPT-80 orally every 12 h for 10 days as treatment for mild to moderately severe CDI. OPT-80 was well tolerated by all subjects. Plasma concentrations were below the lower limit of quantitation in almost one-half of patients and typically

Competitive exclusion of a glycopeptide-resistant Enterococcus faecium in the presence of vancomycin but not equivalent concentrations of tylosin or gentamicin.

The effect of subtherapeutic concentrations of antibiotics (10.0 and 40.0 microg/mL of vancomycin, gentamicin, and tylosin) on the efficacy of a mixed anaerobe culture of chicken microflora (CCF) was studied in a continuous-flow fermentation system. Efficacy of CCF posttreatment was assessed by challenge with glycopeptide-resistant Enterococcus faecium (GRE) at 6.0 log10 cfu/mL. Bacterial enumeration of endogenous CCF isolates, volatile fatty acid (VFA) analysis, and challenge with GRE indicated that CCF efficacy was affected by all antibiotic treatments. Although CCF treated with 10.0 microg/mL of vancomycin eliminated GRE13 at a rate of 0.61 log10 cfu/ mL per day, it was unable to eliminate E. coli, a gram-negative challenge organism. All other antibiotic treatments allowed GRE persistence at approximately 2.0 to 6.5 log10 cfu/mL. All antibiotic-treated cultures had decreased concentrations of acetic and propionic acids. Our data suggest that low concentrations of antimicrobials may adversely affect the microbial ecology of gut microflora with respect to its ability to exclude exogenous bacteria. Moreover, gentamicin had an adverse effect on the inhibitory stringency of CCF even though it showed little anti-anaerobic activity against CCF strict anaerobes in pure culture. Verification of the results in live animals will be necessary to determine if antimicrobial treatment could compromise the effectiveness of normal microflora to serve as a natural host defense against infection.

Poultry digestive microflora biodiversity as indicated by denaturing gradient gel electrophoresis.

Populations of digestive microflora in chickens change with age and are affected by diet, stressors, and performance enhancers. Culturing techniques used to profile a bacterial community inadvertently select for some organisms while excluding others. Several molecular-based techniques have been used to profile mixed microbial populations on the basis of DNA extracted from the entire community. Denaturing gradient gel electrophoresis was used in the present study to examine PCR-amplified fragments (amplicons) of a 16S ribosomal DNA variable region from predominant digestive bacteria. The objective of the study was to examine changes in digestive microbial communities of developing Leghorn chicks and molted Leghorn hens. Dendrograms of amplicon patterns indicated approximately 51% similarity between cecal bacteria composition in Leghorn chicks less than 20 d old and chicks greater than 20 d old. Cecal communities in Leghorn chicks given a competitive exclusion culture exhibited 21% correlation at all ages with those in control chicks. Nonmolted and molted hens had 40% similarity between cecal communities, whereas diets with low calcium (0.8% wt/wt) and excess zinc (2,800 mg/kg) lessened population differences (90% similarity). Results indicated the potential usefulness of the molecular-based denaturing gradient gel electrophoresis to monitor changes in digestive bacterial communities in chickens.

Gene dosage and linezolid resistance in Enterococcus faecium and Enterococcus faecalis.

Resistance to linezolid has been associated with a G2576U mutation in domain V of the 23S rRNA. We analyzed nine clinical isolates of linezolid-resistant enterococci and showed a clear association between the number of 23S rRNA genes containing this mutation and the level of linezolid resistance expressed.

Inhibition of vancomycin-resistant enterococci by an in vitro continuous-flow competitive exclusion culture containing human stool flora.

An in vitro anaerobic continuous-flow competitive exclusion (CFCE) culture model was used to study the ability of human stool flora to inhibit the growth of vancomycin-resistant (VR) enterococci (VRE). The CFCE culture was established from a stool sample obtained from a healthy adult. When 10(3) or 10(6) cfu/mL of VR Enterococcus faecium were added to the CFCE culture, the VRE were eliminated within 6 or 9 days, respectively. When 10(7) cfu/mL of the CFCE culture was added to a continuous-flow culture that contained 10(7) cfu/mL of VRE, the density of VRE was reduced but not eliminated. These data support the hypothesis that the indigenous intestinal flora inhibit growth of VRE and suggest that CFCE cultures may be a useful means to study interactions between the indigenous flora and VRE.

Effect of oral Bacillus coagulans administration on the density of vancomycin-resistant enterococci in the stool of colonized mice.

AIMS: A mouse model of vancomycin-resistant enterococcus (VRE) stool colonization was used to study the effect of Bacillus coagulans, a biotherapeutic agent, on the density of colonization. METHODS AND RESULTS: VRE-colonized mice received orally administered B. coagulans (107 cfu) or saline daily for four days. For one VRE strain, the density of VRE at one and four days after treatment was 1.4 log10cfu x g(-1) lower in experimental vs. control mice (P=0.03), and 35% of experimental vs. 0% of control mice had no detectable VRE four days after treatment (P=0.03). For two additional strains, there was no statistically significant reduction of VRE density in the B. coagulans groups. CONCLUSION: B. coagulans therapy reduced the density of colonization for one of three VRE strains tested. SIGNIFICANCE AND IMPACT OF THE STUDY: This study suggests a potential role for biotherapeutic agents as a means to reduce the density of VRE intestinal colonization.

Effect of parenteral antibiotic administration on the establishment of colonization with vancomycin-resistant Enterococcus faecium in the mouse gastrointestinal tract.

A mouse model of intestinal colonization with vancomycin-resistant enterococci (VRE) was used to study the effect of different beta-lactam antibiotics on establishment of VRE colonization. A clinical VanB VRE isolate, Enterococcus faecium C68 (102 or 104 cfu), was inoculated by gastric gavage in conjunction with subcutaneous administration of antibiotics. The MIC of ceftriaxone and ticarcillin against VRE strain C68 is >10,000 microg/mL, and the MIC of piperacillin is 1250 microg/mL. Ceftriaxone and ticarcillin-clavulanate treatment groups developed persistently high levels of stool VRE compared with both the saline and the piperacillin-tazobactam (Pip-Taz) groups (P<.008). The level of stool VRE in the Pip-Taz group did not differ from that for the saline group. Thus, in this mouse model, beta-lactam antibiotics with minimal anti-enterococcal activity promoted establishment of high-level VRE colonization, but Pip-Taz (a beta-lactam antibiotic with more potent activity against VRE) did not.

Effect of antibiotic therapy on the density of vancomycin-resistant enterococci in the stool of colonized patients.

BACKGROUND: Colonization and infection with vancomycin-resistant enterococci have been associated with exposure to antibiotics that are active against anaerobes. In mice that have intestinal colonization with vancomycin-resistant enterococci, these agents promote high-density colonization, whereas antibiotics with minimal antianaerobic activity do not. METHODS: We conducted a seven-month prospective study of 51 patients who were colonized with vancomycin-resistant enterococci, as evidenced by the presence of the bacteria in stool. We examined the density of vancomycin-resistant enterococci in stool during and after therapy with antibiotic regimens and compared the effect on this density of antianaerobic agents and agents with minimal antianaerobic activity. In a subgroup of 10 patients, cultures of environmental specimens (e.g., from bedding and clothing) were obtained. RESULTS: During treatment with 40 of 42 antianaerobic-antibiotic regimens (95 percent), high-density colonization with vancomycin-resistant enterococci was maintained (mean [+/-SD] number of organisms, 7.8+/-1.5 log per gram of stool). The density of colonization decreased after these regimens were discontinued. Among patients who had not received antianaerobic antibiotics for at least one week, 10 of 13 patients who began such regimens had an increase in the number of organisms of more than 1.0 log per gram (mean increase, 2.2 log per gram), whereas among 10 patients who began regimens of antibiotics with minimal antianaerobic activity, there was a mean decrease in the number of enterococci of 0.6 log per gram (P=0.006 for the difference between groups). When the density of vancomycin-resistant enterococci in stool was at least 4 log per gram, 10 of 12 sets of cultures of environmental specimens had at least one positive sample, as compared with 1 of 9 sets from patients with a mean number of organisms in stool of less than 4 log per gram (P=0.002). CONCLUSIONS: For patients with vancomycin-resistant enterococci in stool, treatment with antianaerobic antibiotics promotes high-density colonization. Limiting the use of such agents in these patients may help decrease the spread of vancomycin-resistant enterococci.

A polyclonal outbreak of predominantly VanB vancomycin-resistant enterococci in northeast Ohio. Northeast Ohio Vancomycin-Resistant Enterococcus Surveillance Program.

We studied the molecular epidemiology of vancomycin-resistant enterococci (VRE) isolated in northeast Ohio during 1996 and examined the association between isolation of VRE from samples other than stool and antimicrobial purchases for five Cleveland hospitals. Susceptibility testing and pulsed-field gel electrophoresis were used to analyze 363 isolates from individual patients from 13 hospitals. Susceptibility testing indicated that 287 strains (79%) expressed the VanB phenotype and 76 (21%) expressed the VanA phenotype. The outbreak was polyclonal, with 30 total genotypes. Both VanA and VanB VRE demonstrated multiple genotypes. One genotype was present in all hospitals, suggesting spread between hospitals. For five teaching hospitals, rates of isolation from non-stool sources and from blood correlated positively with purchases of ticarcillin/clavulanic acid (P = .005). In summary, this outbreak demonstrates transmission of VRE between several hospitals in a geographic region and suggests that use of certain beta-lactam antibiotics may be associated with an increased prevalence of VRE.

Effect of parenteral antibiotic administration on persistence of vancomycin-resistant Enterococcus faecium in the mouse gastrointestinal tract.

A mouse model of vancomycin-resistant Enterococcus faecium (VRE) intestinal colonization was used to study the effect of different subcutaneous antibiotics on persistence and density of VRE colonization. Gastric inoculation of a clinical VanB VRE isolate, in conjunction with oral vancomycin in drinking water (250 microgram/mL), resulted in high-level VRE colonization (mean, 9.5 log10 cfu/g) in all 169 experimental mice. After discontinuation of oral vancomycin, the level of VRE in the stool specimens of mice receiving subcutaneous saline steadily decreased (mean, 3.59 log10 cfu/g at day 19). Subcutaneous vancomycin, clindamycin, piperacillin-tazobactam, ticarcillin-clavulanic acid, metronidazole, cefotetan, ampicillin, and ampicillin-sulbactam all promoted persistent high levels of stool VRE. Subcutaneous ceftriaxone, cefepime, ciprofloxacin, and aztreonam promoted increased VRE density to a lesser degree or not at all. Thus, in a mouse model, vancomycin and antibiotics with potent antianaerobic activity promoted persistent high-density intestinal VRE colonization, whereas antibiotics lacking potent antianaerobic activity did not.

Genetic linkage and cotransfer of a novel, vanB-containing transposon (Tn5382) and a low-affinity penicillin-binding protein 5 gene in a clinical vancomycin-resistant Enterococcus faecium isolate.

Mechanisms for the intercellular transfer of VanB-type vancomycin resistance determinants and for the almost universal association of these determinants with those for high-level ampicillin resistance remain poorly defined. We report the discovery of Tn5382, a ca. 27-kb putative transposon encoding VanB-type glycopeptide resistance in Enterococcus faecium. Open reading frames internal to the right end of Tn5382 and downstream of the vanXB dipeptidase gene exhibit significant homology to genes encoding the excisase and integrase of conjugative transposon Tn916. The ends of Tn5382 are also homologous to the ends of Tn916, especially in regions bound by the integrase enzyme. PCR amplification experiments indicate that Tn5382 excises to form a circular intermediate in E. faecium. Integration of Tn5382 in the chromosome of E. faecium C68 has occurred 113 bp downstream of the stop codon for the pbp5 gene, which encodes high-level ampicillin resistance in this clinical isolate. Transfer of vancomycin, ampicillin, and tetracycline resistance from C68 to an E. faecium recipient strain occurs at low frequency in vitro and is associated with acquisition of a 130- to 160-kb segment of DNA that contains Tn5382, the pbp5 gene, and its putative repressor gene, psr. The interenterococcal transfer of this large chromosomal element appears to be the primary mechanism for vanB operon spread in northeast Ohio. These results expand the known family of Tn916-related transposons, suggest a mechanism for vanB operon entry into and dissemination among enterococci, and provide an explanation for the nearly universal association of vancomycin and high-level ampicillin resistance in clinical E. faecium strains.

Transferable, plasmid-mediated vanB-type glycopeptide resistance in Enterococcus faecium.

An approximately 60-kb transferable, vanB-carrying plasmid has been identified in a clinical Enterococcus faecium strain. A similar plasmid has been observed in an unrelated E. faecium strain, suggesting that plasmid transfer of vanB operons occurs in nature and plays a role in the dissemination of VanB-type resistance among strains of E. faecium.

Acute epiglottitis. An 18-year experience in Rhode Island.

OBJECTIVE: To assess the incidence, clinical characteristics, management, and outcome of epiglottitis in a defined population over an 18-year period. DESIGN: Case series. SETTING: The state of Rhode Island, 1975 through 1992. PATIENTS OR OTHER PARTICIPANTS: Cases who met predetermined criteria for acute epiglottitis identified from hospital discharges and the State Medical Examiner's log of prehospitalization deaths. MAIN OUTCOME MEASURES: Incidence by year and age, clinical presentation, results of diagnostic evaluations, management, and outcome. RESULTS: Four hundred seven cases were identified, 134 in children and 273 in adults. Incidence in children dropped from 38 cases in the first 3 years of the study to 1 case in the last 3 years (p < 0.001). Adult cases increased from 17 in the first 3 years to 69 in the last 3 years (p < 0.001). Seventy-nine percent of adults and 32% of children were treated without an artificial airway. Factors associated with airway obstruction included symptomatic respiratory difficulty, stridor, drooling, shorter duration of symptoms, enlarged epiglottis on radiograph, and Haemophilus influenzae bacteremia (p < 0.001 for each). Twelve patients died (3 children and 9 adults), with all cases of fatal respiratory obstruction occurring within 12 h of presentation. CONCLUSIONS: There have been significant changes in the clinical epidemiology of epiglottitis, which now occurs almost exclusively in adults, often with less severe symptoms and a lower incidence of H influenzae infection. While careful observation is indicated for all patients, the data suggest that those with certain clinical characteristics can be treated safely without an immediate artificial airway.