Is Kawasaki Disease Caused by a Respiratory Virus?

BACKGROUND

Kawasaki disease is characterized by high fever, rash, cervical lymphadenopathy, conjunctival injection, oral mucous membrane changes and swelling of the extremities followed by skin sloughing. Despite >50 years of study, no bacterial, viral or other infectious agent has been consistently associated with the illness. The lockdown and social distancing for COVID-19 in March 2020 led to a marked decrease in respiratory virus circulation. This provided an "experiment of nature" to determine whether Kawasaki disease would decline in parallel.

METHODS

Discharge ICD-10 diagnosis codes were obtained from the Vizient Clinical Data Base for Kawasaki disease and respiratory viruses, and analyzed for the age group < 5 years. Weekly respiratory virus positivity data were also obtained from BioFire Diagnostics.

RESULTS

Common enveloped respiratory viruses declined precipitously from April 2020 through March 2021 to levels at or below historical seasonal minimum levels. Kawasaki Disease declined about 40% compared with 2018-2019, which is distinctly different from the pattern seen for the enveloped respiratory viruses. Strong seasonality was seen for Kawasaki disease as far back as 2010, and correlated most closely with respiratory syncytial virus, human metapneumovirus and less so with influenza virus suggesting there is a baseline level of Kawasaki disease activity that is heightened during yearly respiratory virus activity but that remains at a certain level even in the near total absence of respiratory viruses.

CONCLUSIONS

The striking decrease in enveloped respiratory viruses after lockdown and social distancing was not paralleled by a comparable decrease in Kawasaki disease incidence, suggesting a different epidemiology.

Relationship of Multiplex Molecular Pneumonia Panel Results With Hospital Outcomes and Clinical Variables

Background

Antibiotic treatment decisions in severely ill patients must often be made in the absence of microbiologic results. The recently Food and Drug Administration-cleared BioFire FilmArray Pneumonia Panel (PN) detects 15 bacteria semiquantitatively, 3 atypical pneumonia bacteria, 8 viruses, and 7 antimicrobial resistance markers by multiplex PCR in ~1 hour in the laboratory. Previous reports have shown that the PN Panel bacterial detections are highly accurate, even when routine culture had no growth.

Methods

Consecutive bronchoalveolar lavage and endotracheal specimens submitted for culture between June and September 2018 from 270 patients with sufficient clinical and laboratory data were tested with the PN Panel. Patients were divided into 3 groups: (1) both culture and PN Panel positive, (2) PN Panel positive but culture uninformative (no growth or normal flora), and (3) patients with no PN Panel detections.

Results

Groups 1 and 2 had significantly higher maximum temperatures on the day of culture (P = .00036, analysis of variance [ANOVA] with Bonferroni correction), higher levels of an inflammatory response as measured by percent polymorphonuclear leukocytes in bronchoalveolar lavage (P = .00025, ANOVA with Bonferroni correction), and gram stain report of white blood cells, as previously reported [1].

Conclusions

Both group 1 (culture and PN Panel positive), and group 2 (PN Panel positive but culture uninformative) had higher levels of host response inflammatory responses compared with group 3, which had no targets detected, suggesting that PN Panel detections need to be interpreted in the clinical context, even if cultures are discordant. Depending on laboratory turnaround time, there could be opportunities for improved diagnosis and antibiotic stewardship.

Target capture sequencing of SARS-CoV-2 genomes using the ONETest Coronaviruses Plus

We introduce a target capture next-generation sequencing methodology, the ONETest Coronaviruses Plus, to sequence the SARS-CoV-2 genome and select loci of other respiratory viruses. We applied the ONETest on 70 respiratory samples (collected in Florida, USA between May and July, 2020), in which SARS-CoV-2 had been detected by a PCR assay. For 48 of the samples, we also applied the ARTIC protocol. Of the 70 ONETest libraries, 45 (64%) had a (near-)complete sequence (>29,000 bases and >90% covered by >9 reads). Of the 48 ARTIC libraries, 25 (52%) had a (near-)complete sequence. In 19 out of 25 (76%) samples in which both the ONETest and ARTIC yielded (near-)complete sequences, the lineages assigned were identical. As a target capture approach, the ONETest is less prone to loss of sequence coverage than amplicon approaches, and thus can provide complete genomic information more often to track and monitor SARS-CoV-2 variants.

Dissemination mechanisms of NDM genes in hospitalized patients

Background

NDM-producing Enterobacteriaceae are a major clinical concern worldwide. We characterized NDM-positive pathogens isolated from patients and assessed the dissemination patterns of the bla_NDM genes in a hospital setting.

Methods

Eleven NDM-positive Enterobacteriaceae (three Enterobacter hormaechei, six Klebsiella pneumoniae and two Escherichia coli) were isolated from nine patients over a 1 year period. Antimicrobial susceptibility was assessed by MICs. A combination of short- and long-read WGS was used for genome analysis. Clinical treatment history of patients was linked with genetic features of individual isolates to investigate the dissemination patterns of the bla_NDM genes and NDM-positive strains.

Results

bla_NDM in clonal K. pneumoniae were transmitted between two patients. In other instances, an identical IncC plasmid encoding NDM-1 was transmitted between E. coli and K. pneumoniae isolated from the same patient, and an IncX3 plasmid, carrying bla_NDM-1 or bla_NDM-5, was harboured in non-clonal E. hormaechei. Varying patterns of IS elements were identified as a critical transmission mechanism in association with bla_NDM genes.

Conclusions

Multiple transmission patterns were identified in hospitalized patients, including dissemination of clonal bacterial strains carrying resistance genes and horizontal transfer of resistance genes among divergent bacterial strains. Controlling spread of NDM is complex: while attention to standard infection control practices is critically important, this needs to be matched by aggressive efforts to limit unnecessary antimicrobial use, to minimize the selection for and risk of transfer of ‘high mobility’ resistance genes among Enterobacteriaceae.

Performance of a Semiquantitative Multiplex Bacterial and Viral PCR Panel Compared With Standard Microbiological Laboratory Results: 396 Patients Studied With the BioFire Pneumonia Panel

Background

Microbiologic results are critical to optimal management of patients with lower respiratory tract infection, but standard methods may take several days. The multiplex polymerase chain reaction BioFire Pneumonia (PN) panel detects 15 common bacterial species semiquantitatively as copy number/mL, 8 viral species, and 7 resistance genes in about an hour within the clinical laboratory.

Methods

We tested 396 unique endotracheal or bronchoalveolar lavage specimens with the BioFire Pneumonia panel and compared the bacterial detections to conventional gram stain and culture results.

Results

Of the 396 patients, 138 grew at least 1 bacterium that had a target on the PN panel, and 136/138 (98.6%) were detected by the panel. A total of 177 isolates were recovered in culture and the PN panel detected 174/177 (98.3%). A further 20% of patients had additional targets detected that were not found on standard culture (specificity 69%, positive predictive value 63%, and negative predictive value 98.9%). Copy number was strongly related to standard semiquantitative growth on plates reported by the laboratory (eg, 1+, 2+, 3+ growths) and was significantly higher in those specimens that grew a potential pathogen. Both higher copy number and bacterial detections found by the PN panel, but not found in culture, were strongly positively related to the level of white blood cells reported in the initial gram stain.

Conclusions

Higher copy number and bacterial detections by the PN panel are related to the host respiratory tract inflammatory response. If laboratories can achieve a rapid turnaround time, the PN panel should have a significant impact both on patient management and on antibiotic stewardship.

Hourly Effect of Pretreatment With IV Antibiotics on Blood Culture Positivity Rate in Emergency Department Patients

Although it is intuitive that antibiotics administered before obtaining a blood culture would reduce the likelihood of obtaining a positive culture, it is not clear exactly how rapidly and to what extent blood becomes sterile after administration of intravenous (IV) antibiotics. Using a large data set of patients admitted from the UFHealth Shands Adult Emergency Department (ED) between 2012 and 2016 (n = 25 686), we had the opportunity to more closely examine the effect of starting IV antibiotics before vs after obtaining blood cultures. We present data on the effect of pretreatment with IV antibiotics for both septic and nonseptic ED patients on the blood culture positivity rate on an hour-by-hour basis, as well as the effects on distribution of species recovered and the impact of antibiotic resistance in empiric treatment with antibiotics.

Enhanced in vitro activity of tigecycline in the presence of chelating agents

The lack of availability of novel antibiotic agents and the rise of resistance to existing therapies has led clinicians to utilise combination therapy to adequately treat bacterial infections. Here we examined how chelators may impact the in vitro activity of tigecycline (TIG) against Pseudomonas aeruginosa, Escherichia coli and Klebsiella pneumoniae. Minimum inhibitory concentrations (MICs) were determined by broth dilution with and without various combinations of chelators (EDTA and other tetracyclines) and metal ions (i.e. calcium, magnesium). Trimethoprim (TMP) was used as a non-chelating control. Addition of metal ions led to increases in MICs, whilst addition of EDTA led to decreases in MICs. The chelating effects of EDTA were reversed by addition of magnesium and most profoundly calcium. Similar effects of EDTA and calcium were observed for tetracycline (TET) and TMP. When other tetracyclines (TET, oxytetracycline (OXY) and chlortetracycline (CHL)) were used as chelators at concentrations below their MICs, TIG MICs decreased for P. aeruginosa but not for E. coli. Some decreases in TIG MICs were observed for K. pneumoniae when TET and CHL were added. A dose-dependent decrease in TIG MIC was observed for TET and was reversed by the addition of calcium. The presence of effects of EDTA and calcium on TMP MICs indicates that mechanisms outside of TIG chelation likely play a role in enhanced activity. Full characterisation of an unexpected interaction such as TIG-TET with different microorganisms could provide valuable insights into the underlying mechanisms and design of physiologically viable chelators as candidates for future combinations regimens.

Relationship between bacteriology report time in the morning and length of stay in hospital after the report

We studied the relationship between the time of day bacteriology reports were available in the electronic medical record (Epic, Verona, WI) and subsequent length of stay (LOS) following the last report before discharge. All patients ≥18years admitted to the UF Health Shands Hospital between 1/1/2014-2/29/2016 were included. We calculated the mean LOS following the report for each half-hour time period between 6AM and 1PM (N=14, 95.6% of all results) and tested the relationship to subsequent LOS. For patients whose total LOS was ≤168hours (N=13,830) there was a highly significant positive linear relationship between the report time and LOS following the last report (r=0.8813, P=0.00001556). For those patients with total LOS>168h, there was no clear relationship between report time in the morning and LOS after the last bacteriology report. The relationship between bacteriology report time in the morning and use of this information by physicians in discharge decision-making is likely to be complex and multi-factorial, but for those patients with a total hospital LOS ≤168h, there is a strong relationship between an earlier report and earlier patient discharge.

Semi-quantitative Influenza A population averages from a multiplex respiratory viral panel (RVP): potential for reflecting target sequence changes affecting the assay

Background

Yearly influenza virus mutations potentially affect the performance of molecular assays, if nucleic acid changes involve the sequences in the assay. Because individual patient viral loads depend on variables such as duration of illness, specimen type, age, and immunosuppression, we examined seasonal population averages of positive tests to smooth inherent variability.

Methods

We studied the population seasonal averages of the semi-quantitative nAMPs for the influenza matrix and hemagglutinin genes in the GenMark (Carlsbad, CA) Respiratory Viral Panel assay between 3 institutions over 3 Influenza seasons.

Results

Population average nAMPs were strikingly consistent between separate institutions, but differed substantially between H3N2 and H1N1 seasons. In the 2012–2013 and 2014–2015 influenza seasons, matrix gene H3N2 nAMP averages were 50–70% less than those of the same assay in the 2013–2014 H1N1 season. Influenza strains representative of these seasons were grown in tissue culture and when the supernatant virus was adjusted to the same copy number using a TaqMan assay, the same relative differences were reproduced in the RVP assay. Because the sequences for the PCR and PCR product detection in the GenMark assay are proprietary, the manufacturer provided single stranded DNA matching the capture probe for the representative H3N2 (3 mismatches) and H1N1 strains (2 different mismatches). Equimolar concentrations of these synthetic DNA sequences gave average nAMP values that closely correlated with the average nAMPS of the representative strains and their respective seasonal averages.

Conclusions

Seasonal averages of semi-quantitative data may provide a means to follow assay performance as a reflection of the effects of molecular drift.

Sample-to-result molecular infectious disease assays: clinical implications, limitations and potential

Molecular infectious disease diagnostic tests have undergone major advances in the past decade and will continue to rapidly evolve. Assays have become extraordinarily simple to perform, eliminating the need for pre-analytic sample preparation and post-amplification analysis. This allows these tests to be performed in settings without sophisticated expertise in molecular biology, including locations with limited resources. Additionally, the sensitivity and specificity of these assays is superb and many offer extremely fast turn-around times. These tests have major impacts on patient care, but also have some limitations.

Hemagglutinin Gene Clade 3C.2a Influenza A(H3N2) Viruses, Alachua County, Florida, USA, 2014–15

Influenza A(H3N2) strains isolated during 2014–15 in Alachua County, Florida, USA, belonged to hemagglutinin gene clade 3C.2a. High rates of influenza-like illness and confirmed influenza cases in children were associated with a decrease in estimated vaccine effectiveness. Illnesses were milder than in 2013–14; severe cases were concentrated in elderly patients with underlying diseases.

Hemagglutinin Gene Clade 3C.2a Influenza A(H3N2) Viruses, Alachua County, Florida, USA, 2014-15

Influenza A(H3N2) strains isolated during 2014-15 in Alachua County, Florida, USA, belonged to hemagglutinin gene clade 3C.2a. High rates of influenza-like illness and confirmed influenza cases in children were associated with a decrease in estimated vaccine effectiveness. Illnesses were milder than in 2013-14; severe cases were concentrated in elderly patients with underlying diseases.

Clinical and economic impact of antimicrobial stewardship interventions with the FilmArray blood culture identification panel

The purpose of this study was to evaluate the impact of the FilmArray Blood Culture Identification (BCID) Panel on the management of patients with blood cultures growing gram positive cocci and Candida. We retrospectively compared clinical and economic outcomes between patients during the BCID testing period and a matched historical control group before BCID testing was introduced. A total of 84 BCID patients were matched to 252 historical controls. BCID identification of coagulase negative staphylococci contaminants resulted in shorter post-culture length of stay (P < 0.008) and saved roughly $30,000 per 100 patients tested. The BCID led to shorter duration of empirical vancomycin for patients with contaminated blood cultures (P = 0.005) and methicillin-susceptible Staphylococcus aureus bacteremia (P < 0.001). Patients with vancomycin-resistant enterococcal bacteremia received active therapy earlier than historical controls (P = 0.047). The BCID, coupled with antimicrobial stewardship intervention, was a cost effective tool to improve patient care.

A rare case of classical Hodgkin's lymphoma in the setting of a newly diagnosed left atrial myxoma

We report a rare case of left atrial myxoma with concomitant classical Hodgkin's lymphoma in a 36-year-old woman with a non-significant medical history and 4 months of progressively worsening palpitations, dyspnoea on exertion, chest discomfort and fatigue. Outpatient echocardiography revealed functional mitral valve stenosis as a result of a large left atrial cardiac mass. Preoperative thoracic imaging revealed an anterior mediastinal mass with associated lymphadenopathy. The patient underwent successful resection of the anterior mediastinal mass and left atrial mass. Surgical pathology revealed myxoma in the left atrium and classical Hodgkin's lymphoma in the anterior mediastinum. Thus the patient was diagnosed with early-stage classical Hodgkin's lymphoma. This clinical vignette emphasises the importance of a comprehensive diagnostic evaluation in the setting of a newly discovered atrial tumour.

Multiplex gastrointestinal pathogen panels: implications for infection control

In the acute care hospital inpatient setting, there is a wide variety of causes for both infectious and noninfectious diarrhea. However, without molecular assays for the wide range of agents causing gastroenteritis, there is no reliable way to determine which individuals should be placed in contact precautions, as recommended by CDC. We tested 158 inpatient diarrheal stool specimens with the FilmArray GI Panel (BioFire Diagnostics, Salt Lake City, UT, USA) that had been stored at -70°C after testing negative by conventional methods for Clostridium difficile and/or rotavirus. We found that 22.2% had at least 1 other infectious agent detected, and 60% of these patients were never placed in appropriate isolation for a total of 109 patient-days. In addition, 20.3% of patients with negative GI panel results could have been removed from isolation. Use of multiplex gastrointestinal panels may improve decisions regarding patient isolation and reduce nosocomial transmission.

Direct identification of bacteria in positive blood cultures: comparison of two rapid methods, FilmArray and mass spectrometry

We evaluated the accuracy and performance of the FilmArray Direct from Positive Blood Culture system (BCID) (BioFire Diagnostics, Salt Lake City, UT, USA) and the VITEK Mass Spectrometry System (Vitek MS; bioMerieux, Durham, NC, USA) to identify bacterial isolates from 161 positive blood culture bottles. The BCID uses multiplex PCR to identify 90-95% of common isolates to the genus or species/complex level as well as mecA, Van A/B, and bla(KPC) genes in approximately 1 hour. Of 151 monomicrobic isolates, the FilmArray correctly identified 48/49 (98%) to the genus and 84/84 (100%) to the species/complex level, while 18/151 (12%) gave no identification, as expected from the database. Mass spectrometry correctly identified 142/151 (94%) monomicrobic cultures to the genus level, 137/151 (91%) to the species level, with only 8/151(5%) giving no identification. Although mass spectrometry has a much larger database, the filtration system was cumbersome in contrast to the 3-5 minutes hands-on-time for the BCID.

Universal intravenous access cleaning device fails to sterilize stopcocks

BACKGROUND

Contamination of a central venous catheter may occur through use of conventional open-lumen stopcock devices (COLDs), or disinfectable, needleless, closed connectors (DNCCs). We investigated the effectiveness of a new universal IV access cleaning device (Site-Scrub) compared with 70% isopropyl alcohol prep pads for sanitizing COLDs or DNCCs inoculated with common catheter-associated pathogens.

METHODS

Site-Scrub was compared with 70% alcohol prep pads for sanitizing contaminated female Luer lock COLD or DNCC filled with sterile saline or propofol and 2 common bacterial central venous catheter contaminants (Staphylococcus epidermidis or Pseudomonas aeruginosa). Devices were contaminated using a glove touch (COLD and DNCC) or syringe tip (COLD). The primary end point of the study was colony-forming units (CFU) after 24 hours.

RESULTS

The use of glove touch contamination, the contaminants, S epidermidis and P aeruginosa, produced CFU in saline-filled COLDs treated with the Site-Scrub, but not in those treated with alcohol pads (P < 0.001). Similar results were observed with propofol-filled COLDs (P < 0.001). For DNCCs filled with saline or propofol, both alcohol and Site-Scrub effectively reduced CFU growth compared with contaminated controls (P < 0.001). When COLDs were contaminated by treated syringe tips, there was no significant evidence of reduction in CFU growth by using either alcohol pads or Site-Scrub compared with contaminated controls.

CONCLUSIONS

These data suggest that when the inner surface of the COLD is contaminated, both alcohol pads and Site-Scrub were not significantly effective in decontaminating the COLD. When the COLD rim is contaminated, however, alcohol pads outperform Site-Scrub. DNCCs were uniformly decontaminated with either treatment. Future work should focus on better access systems because current COLDs are difficult to decontaminate.

Time to positivity of blood cultures supports antibiotic de-escalation at 48 hours

BACKGROUND

Appropriate de-escalation of empirical antimicrobial therapy is a fundamental component of antimicrobial stewardship. Concern for the late detection of bloodstream pathogens may undermine early streamlining efforts and subject patients to protracted courses of nonessential therapy.

OBJECTIVE

To quantify the prevalence of bacterial bloodstream infection (BSI) detection after more than 48 hours of culture incubation. We also assessed the impact of antimicrobial therapy delivered prior to blood sample collection.

METHODS

We retrospectively evaluated time to blood culture positivity (TTP) in adult patients at an academic tertiary care hospital. Microbiology reports were reviewed to identify the TTP for the first positive blood culture bottle for each episode of BSI occurring from February 1, 2011, to July 31, 2011. Isolates were classified as true pathogens or contaminants. Blood culture results after 48 hours of incubation were compared with results after 120 hours of incubation.

RESULTS

The median TTP of 416 monomicrobial BSIs and 210 contamination episodes was 13.7 and 24.4 hours, respectively (P < .001). The median TTPs in those who received and did not receive prior antibiotics were 17.0 and 12.8 hours, respectively (P < .001). By 48 hours, 98% of aerobic Gram-positive and Gram-negative BSIs were detected. Culture results at 48 hours were 97% sensitive and had a negative predictive value of 99.8%.

CONCLUSION

Few true BSIs are detected after more than 48 hours of culture incubation. Clinicians may adjust empirical antibiotic coverage at this time with little risk for subsequent bacterial pathogen detection.

Ultrastructural, immunofluorescence, and RNA evidence support the hypothesis of a "new" virus associated with Kawasaki disease

BACKGROUND

Intracytoplasmic inclusion bodies (ICI) have been identified in ciliated bronchial epithelium of Kawasaki disease (KD) patients using a synthetic antibody derived from acute KD arterial IgA plasma cells; ICI may derive from the KD etiologic agent.

METHODS

Acute KD bronchial epithelium was subjected to immunofluorescence for ICI and cytokeratin, high-throughput sequencing, and transmission electron microscopy (TEM). Interferon pathway gene expression profiling was performed on KD lung.

RESULTS

An intermediate filament cytokeratin "cage" was not observed around KD ICI, making it unlikely that ICI are overproduced or misfolded human protein aggregates. Many interferon-stimulated genes were detected in the bronchial epithelium, and significant modulation of the interferon response pathway was observed in the lung tissue of KD patients. No known virus was identified by sequencing. Aggregates of virus-like particles (VLP) were detected by TEM in all 3 acute KD patients from whom nonembedded formalin-fixed lung tissue was available.

CONCLUSIONS

KD ICI are most likely virus induced; bronchial cells with ICI contain VLP that share morphologic features among several different RNA viral families. Expedited autopsies and tissue fixation from acute KD fatalities are urgently needed to more clearly ascertain the VLP. These findings are compatible with the hypothesis that the infectious etiologic agent of KD may be a "new" RNA virus.

Clinical laboratory detection of AmpC β-lactamase: does it affect patient outcome?

Plasmid-mediated AmpC-producing Escherichia coli and Klebsiella pneumoniae have been associated with poor clinical outcomes, but they are not readily identified in hospital microbiology laboratories. We tested 753 gram-negative bloodstream isolates for AmpC by using the EDTA disk test and the modified Hodge test (n = 172) and the modified Hodge test alone (n = 581). The 30-day mortality for the AmpC group was 9% (2/23) and was 6% (3/51) for the control group. The clinical response was similar: afebrile on day 2 (AmpC group, 16/23 [70%]; control group, 32/45 [71%]) and on day 4 (AmpC group, 19/22 [86%]; control group, 37/44 [84%]). Patients with isolates in the AmpC group were more likely to be in an intensive care unit at the time of the positive blood culture (P = .01) and more likely to be intubated (P = .05) than patients with isolates in the control group. Effective antibiotic treatment within the first 48 hours was given to 47 (92%) of 51 patients with isolates in the control group but to only 14 (61%) of 23 patients with isolates in the AmpC group (P = .001). The modified Hodge test and the EDTA disk test did not identify patients at risk for a poor outcome from AmpC-producing bacterial infections.

Use of bronchoalveolar lavage to detect galactomannan for diagnosis of pulmonary aspergillosis among nonimmunocompromised hosts

Pulmonary aspergillosis in nonimmunocompromised hosts, although rare, is being increasingly recognized. The diagnosis of pulmonary aspergillosis is difficult, since the recovery of Aspergillus from respiratory samples cannot differentiate colonization from invasion. We assessed the role of bronchoalveolar lavage (BAL) in detecting galactomannan (GM) for diagnosing pulmonary aspergillosis in 73 nonimmunocompromised patients with pulmonary infiltrates for whom the test was ordered. Six patients had pulmonary aspergillosis, two each with acute invasive pulmonary aspergillosis, chronic necrotizing pulmonary aspergillosis, and aspergilloma. All six patients had a BAL GM level of >/=1.18. The sensitivity, specificity, and negative predictive value (NPV) for a BAL GM level of >/=1.0 were 100%, 88.1%, and 100%, respectively. Notably, the positive predictive value (PPV) was only 42.9%, likely reflecting the low prevalence of pulmonary aspergillosis among nonimmunosuppressed patients. The combination of BAL microscopy and culture had a sensitivity and NPV similar to those of BAL GM detection but a higher specificity and PPV (92.5% and 54.6%, respectively). Moreover, a BAL GM test did not identify any cases that were not diagnosed by conventional methods like microscopy and culture. In conclusion, there was no conclusive benefit of determining BAL GM levels in the diagnosis of pulmonary aspergillosis among nonimmunocompromised hosts. Given the likelihood of false-positive results, a BAL GM test should not be ordered routinely in this population.

Bronchoalveolar lavage galactomannan in diagnosis of invasive pulmonary aspergillosis among solid-organ transplant recipients

We review the experience at our institution with galactomannan (GM) testing of bronchoalveolar lavage (BAL) fluid in the diagnosis of invasive pulmonary aspergillosis (IPA) among solid-organ transplant recipients. Among 81 patients for whom BAL GM testing was ordered (heart, 24; kidney, 22; liver, 19; lung, 16), there were five cases of proven or probable IPA. All five patients had BAL GM of > or = 2.1 and survived following antifungal therapy. The sensitivity, specificity, and positive and negative predictive values for BAL GM testing at a cutoff of > or = 1.0 were 100%, 90.8%, 41.7%, and 100%, respectively. The sensitivity of BAL GM testing was better than that of conventional tests such as serum GM or BAL cytology and culture. Moreover, a positive BAL GM test diagnosed IPA several days to 4 weeks before other methods for three patients. Twelve patients had BAL GM of > or = 0.5 but no evidence of IPA. Among these, lung transplant recipients accounted for 41.7% (5/12) of the false-positive results, reflecting frequent colonization of airways in this population. Excluding lung transplants, the specificity and positive predictive value for other solid-organ transplants increased to 92.9% and 62.5%, respectively (cutoff, > or = 1.0). In conclusion, BAL GM testing facilitated more-rapid diagnoses of IPA and the institution of antifungal therapy among non-lung solid-organ transplant recipients and helped to rule out IPA.

The AmpC inhibitor, Syn2190, can be used to reveal extended-spectrum beta-lactamases in Escherichia coli

AmpC beta-lactamases are not inhibited by clavulanic acid and could potentially mask detection of extended-spectrum beta-lactamases (ESBLs) using the Clinical and Laboratory Standards Institute confirmatory test. Syn2190 (1,5-dihydroxy-4-pyridone monobactam) selectively inhibits AmpC, but not ESBLs. Fifty-four MicroScan ESBL screen-positive strains of Escherichia coli and an unrelated group of 20 cefoxitin-nonsusceptible E. coli strains were tested with the confirmatory ceftazidime-cefotaxime-clavulanate disk method with or without 4 microg/mL of Syn2190 in the agar. Without Syn2190, 8 (14.8%) of 54 E. coli isolates and 0 of 20 cefoxitin-nonsusceptible E. coli isolates were confirmed. With Syn2190, an additional 9 (16.6%) of 54 of the MicroScan screen-positive E. coli isolates and 6 (30%) of 20 of the cefoxitin-nonsusceptible E. coli isolates were found. Multiplex polymerase chain reaction and sequence analysis confirmed the presence of the plasmid-associated beta-lactamase gene bla(CMY-2) in the 2 available MicroScan-screened E. coli isolates and in 5 of 6 of the cefoxitin-resistant group. These data suggest that in the presence of AmpC, ESBLs in E. coli may not be detected by the currently recommended confirmatory test.

Daptomycin-reversible rifampicin resistance in vancomycin-resistant Enterococcus faecium

OBJECTIVES

In a previous study, we observed marked synergy between daptomycin and rifampicin against 73% of rifampicin-resistant, vancomycin-resistant Enterococcus faecium (VRE), with approximately 100-fold reductions in rifampicin MICs observed at one-eighth to one-fourth daptomycin MIC. The purpose of this study was to determine whether the synergy between daptomycin and rifampicin could be explained by enhanced entry of rifampicin into the cell or was related to amino acid substitutions in the rifampicin-binding site in the beta subunit (rpo beta) of the RNA polymerase.

METHODS

We developed a bioassay for rifampicin to measure cell-bound rifampicin levels as well as metabolic inactivation of rifampicin. In addition, we sequenced the rifampicin-binding site in the rpo beta of VRE strains with and without synergy between daptomycin and rifampicin.

RESULTS

Cell-bound rifampicin levels were the same in rifampicin-susceptible VRE as in rifampicin-resistant VRE showing daptomycin synergy and were not affected by the presence of daptomycin. In contrast, rifampicin-resistant VRE without daptomycin synergy had undetectable cell-bound rifampicin. Sequencing the rpo beta rifampicin-binding site revealed that the synergistic strains had the same sequence as rifampicin-susceptible wild-type E. faecium. The daptomycin synergy-resistant strains all had mutations in known rifampicin-binding sites.

CONCLUSIONS

Daptomycin is able to reverse rifampicin resistance in some strains of VRE, but the mechanism could not be explained by an effect of daptomycin on entry of rifampicin into or transport out of the cell, by inactivation of rifampicin or by mutation involving the rifampicin-binding site.

Pharmacokinetic/pharmacodynamic modeling of in vitro activity of azithromycin against four different bacterial strains

The bacterial time-kill curves of azithromycin against four bacterial strains (Streptococcus pneumoniae/penicillin-intermediate, S. pneumoniae/penicillin-sensitive, Haemophilus influenzae and Moraxella catarrhalis) were determined by in vitro infection models. Eighteen different pharmacokinetic/pharmacodynamic models were fitted to the time-kill data using non-linear regression and compared for best fit. A simple, widely used E(max) model was not sufficient to describe the pharmacodynamic effects for the four bacterial strains. Appropriate models that gave good curve fits included additional terms for saturation of the number of bacteria (N(max)), delay in the initial bacterial growth phase and/or the onset of anti-infective activity (1-exp(-zt)) as well as a Hill factor (h) that captures the steepness of the concentration-response profile. Azithromycin was highly effective against S. pneumoniae strains and M. catarrhalis while the efficacy against H. influenzae was poor. Applications of these pharmacokinetic/pharmacodynamic models will eventually provide a tool for rational antibiotic dosing regimen decisions.

Errors in interpretation of Gram stains from positive blood cultures

We reviewed major errors in Gram stain reports from positive blood cultures to identify patterns and potential clinical impact. During a 23-month period, blood cultures were misread for 57 (0.7%) of 8,253 patients. Of 5,885 read as gram-positive cocci, 6 (0.1%) had only gram-negative organisms by culture, 3 of which were Acinetobacter species Of 1,959 read as gram-negative bacilli, 25 (1.3%) had only gram-positive organisms by culture. Of these, 9 were Bacillus and 2 were Clostridium species. Nonrecognition of mixed Gram stains accounted for 28 errors that most often were associated with a reading of gram-positive cocci. In 4 cases, there were delays of 14 hours to 3 days in starting appropriate antibiotic treatment; 2 deaths occurred, although the erroneous Gram stain report probably was not contributory. Pathologists and laboratory personnel need to be aware of these types of misinterpretations and the potential effects on patient outcome.

Pharmacokinetic-pharmacodynamic modelling of antibacterial activity of cefpodoxime and cefixime in in vitro kinetic models

The bacterial time-kill curves of cefpodoxime and cefixime against four bacterial strains (Haemophilus influenzae, Moraxella catarrhalis, Streptococcus pneumoniae/penicillin sensitive and S. pneumoniae/penicillin intermediate) were compared in in vitro infection models in which various human pharmacokinetic profiles of unbound antibiotic were simulated. This approach offers more detailed information than the minimum inhibitory concentration (MIC) does about the time course of antibacterial efficacy of an antibiotic. A pharmacokinetic-pharmacodynamic (PK-PD) model based on unbound antibiotic concentrations at the site of infection, and a sigmoid Emax-relationship with EC50 as the antibiotic concentration necessary to produce 50% of the maximum effect, effectively described the antimicrobial efficacy of both cefpodoxime and cefixime. The EC50 values of cefpodoxime and cefixime were consistent with their respective MIC values. Both antibiotics had similar high potency against H. influenzae (EC50: 0.04 mg/L) and M. catarrhalis (EC50: 0.12 mg/L), while the potency of cefpodoxime against S. pneumoniae strains was about 10-fold higher than that of cefixime (EC50s/sensitive strain: 0.02 mg/L versus 0.27 mg/L; EC50s/intermediate strain: 0.09 mg/L versus 0.69 mg/L). Applications of this model and unbound tissue PK profiles obtained from a previous clinical study performed in our group, showed that cefpodoxime has higher bacteriological potency than cefixime against S. pneumoniae. Simulations based on this model allow the comparison of antibacterial efficacy of different antibiotics and dosing regimens.

Synergy of daptomycin with oxacillin and other beta-lactams against methicillin-resistant Staphylococcus aureus

We previously observed marked synergy between daptomycin and both rifampin and ampicillin against vancomycin-resistant enterococci (VRE). Because the synergy between daptomycin and ampicillin was observed for 100% of VRE strains with high-level ampicillin resistance (ampicillin MIC of > or =128 microg/ml), we looked for synergy between daptomycin and other beta-lactams against 18 strains of methicillin-resistant Staphylococcus aureus (MRSA) by employing a time-kill method using Mueller-Hinton broth supplemented to 50 mg of Ca2+/liter. All strains were resistant to oxacillin (16 of 18 strains were resistant at drug concentrations of > or =256 microg/ml), and all strains were susceptible to daptomycin (the MIC at which 90% of the tested isolates were inhibited was 1 microg/ml). Daptomycin was tested at concentrations of 2, 1, 0.5, 0.25, 0.125, and 0.0625 microg/ml alone or in combination with oxacillin at a fixed concentration of 32 microg/ml. Synergy was found for all 18 strains with daptomycin at one-half the MIC in combination with 32 microg of oxacillin/ml, and synergy was found for 11 of 18 strains (61%) with daptomycin at one-fourth the MIC or less in combination with oxacillin. At 24 h, the daptomycin-oxacillin combination with daptomycin at one-half the MIC showed bactericidal activity against all 18 strains, and the combination with one-fourth the daptomycin MIC showed bactericidal activity against 9 of 18 strains. We also used a novel screening method to look for synergy between daptomycin and other beta-lactams. In this approach, daptomycin was incorporated into Ca(2+)-supplemented Mueller-Hinton agar at subinhibitory concentrations, and synergy was screened by comparing test antibiotic Kirby-Bauer disks on agar with and without daptomycin. By this method, daptomycin with ampicillin-sulbactam, ticarcillin-clavulanate, or piperacillin-tazobactam showed synergy comparable to or greater than daptomycin with oxacillin. For seven of the eight strains tested, time-kill studies confirmed synergy between daptomycin and ampicillin-sulbactam with ampicillin in the range of 2 to 8 microg/ml. The combination of daptomycin and beta-lactams may be useful for the treatment of MRSA infection, but further studies are needed to elucidate the mechanisms and to determine the in vivo efficacy of the combination.

PK–PD modelling of the effect of cefaclor on four different bacterial strains

The effect of cefaclor against relevant bacterial strains was studied by employing a combined in vivo pharmacokinetic (PK)-in vitro pharmacodynamic (PD) approach. For this purpose selected isolates of Escherichia coli, Moraxella catarrhalis, Haemophilus influenzae and Streptococcus pneumoniae were exposed in vitro to the interstitial cefaclor profile obtained in vivo in the interstitial space fluid of human tissue after administration of commonly used doses of cefaclor and the change in the number of colony forming units per millilitre (CFU/ml) versus time was monitored. Fitting of the data using a modified E(max)-model resulted in a set of mean pharmacodynamic parameters (k0, k(max), EC50) for each bacterial strain. The parameters derived from these experiments were used in a computer-simulation of the antibacterial effects for different dosing regimens and formulations of cefaclor, notably an immediate (IR) and a modified (MR) release formulation. Dosage regimens were compared using the ratio between the number of bacteria remaining after 24 h of a given treatment (N24h). The results indicate that the number of bacteria of all investigated strains killed per day is equivalent when the same daily dose is administered twice a day with the MR dosage form than when given three times a day with the IR dosage form, in spite of the fact that the MR dosage form has approximately 20% lower bioavailability. Best results were obtained with the three-times a day regimen of the MR formulation. In conclusion, the present in vivo-PK/in vitro-PD simulations of the antimicrobial effects of cefaclor indicate that a twice-daily treatment with a MR formulation may offer a convenient and safe alternative to the conventional tid treatment.

Daptomycin synergy with rifampicin and ampicillin against vancomycin-resistant enterococci

We used a novel screening method to look for synergy between daptomycin and 18 other antibiotics against 19 strains of high-level vancomycin-resistant enterococci (VRE) (vancomycin MIC > or = 256 mg/L). In this approach, daptomycin was incorporated into Ca(2+)-supplemented Mueller-Hinton agar at subinhibitory concentrations, and synergy was screened by comparing test antibiotic Etest MICs on agar with and without daptomycin. A striking reduction in the rifampicin MIC was seen in 11/15 (73.3%) VRE that were resistant to rifampicin, from > or =12 mg/L to a mean +/- s.d. of 0.22 +/- 0.21 mg/L at daptomycin 0.25 x MIC and 0.85 +/- 0.90 mg/L at daptomycin 0.125 x MIC. Synergy was also observed for 13/19 (68%) isolates with ampicillin (MIC > or = 128 mg/L). There was no significant synergy between daptomycin and any other antibiotic by this screening method. If confirmed by further studies, daptomycin with either rifampicin or ampicillin may be useful in the management of infections caused by VRE.

Improved methods for the application of random peptide phage libraries to the study of the oligoclonal bands in cerebrospinal fluid of patients with multiple sclerosis

The target antigens of the oligoclonal bands in the cerebrospinal fluid (CSF) of patients with multiple sclerosis (MS) are unknown but may reflect important autoantigens in MS. One approach to identify candidate antigens is to allow CSF to select peptide motifs from a random phage library. To determine whether selected peptide motifs are related to the pathogenesis of MS, it is important to know if other MS patients and appropriate control patients have antibodies reactive with these sequences either in CSF or sera. Unfortunately, serologic screening of such sequences directly in phage clones gave non-specific reactions. Western blotting was found to obviate the non-specificity problem and together with isoelectric focusing, could also be used to demonstrate the co-migration of antigen specific oligoclonal bands with individual total IgG bands. Using 2D gel electrophoresis, absorption of CSF antibodies by specific peptide sequences selected from the phage library could be demonstrated. These techniques should facilitate the systematic study of the targets of the oligoclonal bands in CSF of patients with MS.

Epstein-Barr virus nuclear antigen-1 (EBNA-1) associated oligoclonal bands in patients with multiple sclerosis

Oligoclonal bands (OCBs) are frequently observed in the cerebrospinal fluid (CSF) of patients with multiple sclerosis (MS), but the target antigens of these antibodies remain unknown. We used antigen specific immunoblotting to determine whether Epstein Barr virus nuclear antigen-1 (EBNA-1) was a target of the OCBs in the CSF of patients with MS. Antibody indices (AIs) were measured by ELISA and calculated by the formula of Reiber and Lange which includes correction factors for both breakdown of the blood brain barrier and intrathecal polyclonal IgG synthesis. A distinctive oligoclonal antigen specific banding pattern for EBNA-1 was observed in 5/15 MS patients, but 0/12 controls (P=0.037, Fisher's Exact Probability). AIs in this EBNA-l positive subgroup were extremely high, comparable with levels observed in viral CNS infections. In one patient with EBNA-1 specific OCBs, EBNA-1 and a peptide 'equivalent', p62, were able to absorb a component of the total IgG. Our results suggest that in a subset of MS patients, EBNA-1 may be a major target of selected OCBs.

The potential for dissemination of Mycobacterium tuberculosis through the anesthesia breathing circuit

BACKGROUND

Respiratory pathogens that pass through the anesthesia breathing system potentially can infect other patients. This study was designed to determine if bacteria can pass through contemporary anesthesia breathing systems and if the environment within the machine is hostile to these organisms.

METHODS

Staphylococcus aureus, Pseudomonas aeruginosa, and Mycobacterium tuberculosis were nebulized into the expiratory limb of an anesthesia breathing circuit and collected from the inspiratory and expiratory limbs in an impinger system that provided a quantitative determination of the number of organisms entering the circuit and the number that would reach the patient in the inspiratory gas. Bacteria were collected before, during, and after nebulization. A second experiment determined if a saturated solution of soda lime was bactericidal.

RESULTS

When the gas flow through the circuit was interrupted for < 1 h following the nebulization period, large numbers of microorganisms (1 x 10(3) to 1 x 10(5), around 100% of the nebulized organisms) were collected from the inspiratory gas. Soda lime itself was not bactericidal for any of the organisms tested, but solutions of this material with a pH of 12 were bactericidal.

CONCLUSION

Cross contamination between patients may occur unless the gas flow through the anesthesia breathing system is interrupted for > 1 h.

Molecular approach to find target(s) for oligoclonal bands in multiple sclerosis

OBJECTIVES

Oligoclonal bands are a characteristic finding in the CSF of patients with multiple sclerosis, yet their target antigen(s) remain unknown. The objective was to determine whether a filamentous phage peptide library could be employed to allow the oligoclonal bands to select their own target epitopes.

METHODS

CSF IgG antibody from 14 patients with multiple sclerosis and 14 controls was used to select individual phage clones from a bacteriophage library containing approximately 4 x 10(7) different hexamers expressed on its surface pIII protein. The amino acid sequence selected was deduced by sequencing the DNA of the genetically engineered insert.

RESULTS

In general, after three rounds of selection, CSF from both patients with multiple sclerosis and controls selected one to two consistent peptide motifs. Five out of 14 patients with multiple sclerosis, and one control, selected the amino acid sequence motif, RRPFF. Given 20 possible amino acids per position, the likelihood of five patients selecting the same linear five amino acid sequence is at most 1.6 x 10(-3), corrected for the number of clones sequenced. A GenBank computer search showed that this sequence is found in the Epstein-Barr Virus nuclear antigen (EBNA-1), and a heat shock protein alphaB crystallin. Human serum antibodies to a synthetic peptide containing RRPFF were virtually exclusively found in patients with prior infection by Epstein-Barr virus. Other studies have suggested a relation between Epstein-Barr virus infection and multiple sclerosis, including nearly 100% Epstein-Barr virus seropositivity among patients with multiple sclerosis and increased concentrations of antibody to EBNA in CSF of patients with multiple sclerosis. By antigen specific immunoblotting, antibodies to the RRPFF motif in the CSF were shown to correspond to a subset of oligoclonal bands in the CSF from the same patient.

CONCLUSION

This study shows that phage epitope display libraries may be used to select amino acid motifs which are potentially relevant to the pathogenesis of multiple sclerosis.

A comparison of ligase chain reaction to polymerase chain reaction in the detection of Chlamydia trachomatis endocervical infections

OBJECTIVE

To compare the reliability of ligase chain reaction (LCR) to polymerase chain reaction (PCR) in detecting Chlamydia trachomatis endocervical infections.

METHODS

We conducted a prospective study of 486 patients at risk for chlamydial infection of the endocervix. We obtained two endocervical specimens from each patient and used LCR and PCR to detect C. trachomatis. Discrepant results between the two techniques were resolved by repeat testing and by testing for the major outer membrane protein (MOMP) gene, if necessary. We determined the sensitivity, specificity, positive predictive value, and negative predictive value for each test, using concordant results or MOMP gene results as the "gold standard".

RESULTS

Of the 486 patients, 42 (8.6%) had evidence of C. trachomatis infection after resolution of discrepant results. Of the 42 true positive specimens, 41 were positive by initial LCR and 38 were positive by initial PCR. Of the 444 true negative specimens, none had a positive initial LCR result, while 2 had a positive initial PCR test. Therefore, compared to the gold standard, LCR had a sensitivity of 97.6% and specificity of 100%, while PCR had a sensitivity of 90% and a specificity of 99.5%. The positive and negative predictive values of LCR were 100% and 99.8%, respectively. PCR had a positive predictive value of 95% and a negative predictive value of 99.1%. The difference in sensitivity of LCR versus PCR was not statistically significant (P = .125).

CONCLUSION

LCR and PCR perform equally well in detecting C. trachomatis endocervical infections.

A comparison of ligase chain reaction to polymerase chain reaction in the detection of Chlamydia trachomatis endocervical infections

OBJECTIVE

To compare the reliability of ligase chain reaction (LCR) to polymerase chain reaction (PCR) in detecting Chlamydia trachomatis endocervical infections.

METHODS

We conducted a prospective study of 486 patients at risk for chlamydial infection of the endocervix. We obtained two endocervical specimens from each patient and used LCR and PCR to detect C. trachomatis. Discrepant results between the two techniques were resolved by repeat testing and by testing for the major outer membrane protein (MOMP) gene, if necessary. We determined the sensitivity, specificity, positive predictive value, and negative predictive value for each test, using concordant results or MOMP gene results as the "gold standard".

RESULTS

Of the 486 patients, 42 (8.6%) had evidence of C. trachomatis infection after resolution of discrepant results. Of the 42 true positive specimens, 41 were positive by initial LCR and 38 were positive by initial PCR. Of the 444 true negative specimens, none had a positive initial LCR result, while 2 had a positive initial PCR test. Therefore, compared to the gold standard, LCR had a sensitivity of 97.6% and specificity of 100%, while PCR had a sensitivity of 90% and a specificity of 99.5%. The positive and negative predictive values of LCR were 100% and 99.8%, respectively. PCR had a positive predictive value of 95% and a negative predictive value of 99.1%. The difference in sensitivity of LCR versus PCR was not statistically significant (P = .125).

CONCLUSION

LCR and PCR perform equally well in detecting C. trachomatis endocervical infections.

Rejection criteria for endotracheal aspirates in neonates. Clinical impact

It has been suggested that endotracheal suction specimens from adult and pediatric patients be rejected for culture if no organisms are seen on Gram's stain. We reviewed the experience in neonates under three months of age from our neonatal intensive care unit. Of 195 such endotracheal specimens, 86 (44%) had no growth by culture, 83 (43%) grew normal flora only, and 26 (13%) from 22 patients grew a potential pathogen. Detailed chart review was undertaken to determine what the clinical outcome would have been if the culture information were not provided for these patients. Based on this analysis, almost all patients with Gram-negative rods would have empirically received antibiotics on clinical grounds regardless of culture results, and at least one received antibiotics unnecessarily based on a culture result. On the other hand, two patients whose cultures grew Trichosporon and Aspergillus would have been missed.

Determination of free extracellular concentrations of piperacillin by microdialysis

The tissue penetration and distribution of antibiotics is of great importance, since most of the infections occur in the tissue. At the infection site, the free, unbound fraction of the antibiotic is responsible for the antiinfective effect. These free extracellular concentrations can be measured by microdialysis. It was the aim of the study to correlate free levels of the beta-lactam antibiotic piperacillin in blood with those in tissue. In vivo microdialysis sampling was used to study the tissue distribution patterns of piperacillin in anesthetized rats after single dose iv administration of the drug. The pharmacokinetics of piperacillin in plasma were consistent with a two-compartment body model. Comparisons between calculated free concentrations in the peripheral compartment and measured free extracellular concentrations revealed excellent agreement. Microdialysis is a suitable method to evaluate unbound drug concentrations in the tissues. In case of piperacillin, predictions of the concentration time profiles of free drug in the peripheral compartment can be made on the basis of plasma data.

Pharmacokinetic-pharmacodynamic modeling of the antibiotic effect of piperacillin in vitro

PURPOSE

It was the aim of the present study to investigate the in vitro antimicrobial effects of the beta-lactam antibiotic piperacillin on Escherichia coli using concentration-time profiles similar to those encountered in vivo.

METHODS

An in vitro dilution model was used to expose E. coli to various piperacillin concentration profiles. The antimicrobial effect was evaluated by determination of the number of bacteria over time.

RESULTS

A modified Emax-model was found appropriate to describe the pharmacodynamic effect. This model was linked with the respective piperacillin concentrations to provide a suitable pharmacokinetic-pharmacodynamic (PK-PD) model. The average growth half-life in absence of piperacillin was 28 min and the maximum kill half-life was 25 min. The EC50 for the various dosing regimens averaged 5.2 micrograms/mL and was independent of dose. These parameters were used the simulate the bacterial effects of commonly administered doses or dosing regimens in humans.

CONCLUSIONS

Based on the in vitro data a more frequent administration of piperacillin will be more efficacious. The proposed PK-PD-model allows a more detailed evaluation of dosing regimens than the use of minimum inhibitory concentrations.

Concentration-dependent synergy and antagonism between cefoperazone and imipenem against methicillin-resistant Staphylococcus aureus

By the agar dilution checkerboard method, striking synergy between cefoperazone and imipenem was observed with 32 strains of methicillin-resistant Staphylococcus aureus (fractional inhibitory concentration indices, < or = 0.03 to 0.34; mean, 0.12 +/- 0.08). By the double-disk diffusion method, the synergy was confirmed, but about 60% of strains showed antagonism manifest by truncation of the zone of inhibition around cefoperazone. The mechanism may involve auxiliary factors distinct from those essential for the expression of methicillin resistance.

Detection of candidemia by polymerase chain reaction

Current blood culture methods may not identify all patients with candidemia. We attempted to develop a polymerase chain reaction (PCR)-based method for the detection of candidemia. Several major problems were encountered: use of primers based on single copy or low-copy-number genes lacked sensitivity, while those based on the 18S ribosomal RNA gene often crossreacted with human DNA. One primer set with an internal primer was found to be suitable in a hemi-nested PCR. Sensitivity was in the range of 1 colony forming unit of C. albicans per ml blood in reconstruction experiments. Using stored blood which had been obtained within 12 h of the time a positive blood culture was obtained, PCR was positive in 7/15 (46.7%) patients with culture proven C. albicans candidemia (44% of samples). However, only 1-3 ml blood was available for PCR, while culture results were based on 5-10 ml or more. Two out of 34 (5.9%) unselected outpatient blood samples stored under identical conditions were positive, but both samples were negative when the original DNA was retested. Blood collection and PCR processing equipment appears to be free of contaminating fungal DNA and organisms; however, human skin contains DNA amplifiable by these primers. At present the major limitation is the need for a simple method to recover Candida from 5-10 ml blood while removing haemoglobin and excess white blood cell DNA in a volume suitable for PCR.

Relationship of the polymerase chain reaction for cytomegalovirus to the development of hepatitis in liver transplant recipients

In a pilot study, the polymerase chain reaction was found to be more sensitive than standard viral culture methods for the detection of cytomegalovirus, particularly from blood and tissues. We therefore applied this technique to 71 serially collected liver biopsies from 16 orthotopic liver transplant patients. All patients were CMV-seropositive (n = 15) or seroconverted (n = 1). Seven patients (9 biopsies) had histologically proved CMV hepatitis, and all these biopsies were CMV PCR-positive. Six of these 7 patients had a prior liver biopsy that was CMV PCR-positive, but culture and histology-negative, an average of 13.2 +/- 6.9 days before the histologically positive biopsy. The 7th patient was not biopsied prior to the diagnostic biopsy. Three patients had 7 liver biopsies that were CMV PCR-positive, but histologically negative for CMV hepatitis. Two of these three had CMV infection confirmed by viral culture of blood or liver biopsy. The remaining 6 patients had a total of 26 liver biopsies that were negative for CMV by PCR, culture, and histology. Among liver transplant patients, CMV PCR performed on liver biopsy specimens correctly identified all histologically proven cases of CMV hepatitis. CMV PCR positivity in liver tissue did not correlate with latent infection and preceded the development of CMV hepatitis or other meaningful CMV infection in 8 of 10 patients.

Reproducibility of the microdilution checkerboard method for antibiotic synergy

We assessed the reproducibility of the microdilution checkerboard method for measuring antibiotic synergy. Five strains of Pseudomonas aeruginosa were tested with four antibiotic combinations by using 10 replicates each. Twenty-five percent of replicate sets gave discordant classification results (i.e., a 7:3 or worse split in categorization). Determination of the individual MICs of each antibiotic alone was excellent; all 10 replicates were within 1 twofold dilution for 95% of the 80 sets of 10 replicates. The microdilution checkerboard method either should not be used or should be used with at least five replicates per determination, with > or = 80% agreement among the replicates required for classification.

Vancomycin is not an essential component of the initial empiric treatment regimen for febrile neutropenic patients receiving ceftazidime: a randomized prospective study

The use of vancomycin as part of the initial antibiotic therapy of febrile neutropenic patients has become a controversial issue. Some studies support its incorporation in the initial regimen, and others suggest that vancomycin can be added later. We examined this issue in a prospective, randomized trial. We randomized 127 febrile neutropenic patients to receive either ceftazidime alone or ceftazidime plus vancomycin as the initial empiric antibiotic treatment. We added vancomycin to the ceftazidime arm of the study when fever persisted after 96 h of monotherapy, when new fever occurred after this time, or when a moderately ceftazidime-resistant gram-positive bacterium was isolated. Each of these regimens had similar initial response rates, similar durations of initial fever, similar frequencies of new fever during therapy, similar microbiological cure rates, similar superinfection rates, and similar survival rates. We observed more renal and cutaneous toxicities in patients receiving vancomycin and ceftazidime as initial therapy. We conclude that ceftazidime is appropriate as initial therapy for febrile neutropenic patients and that the addition of vancomycin is appropriate when fever persists after 4 days of monotherapy or when fever recurs following an initial response.

Quantitative tip culture methods and the diagnosis of central venous catheter-related infections

The diagnostic usefulness of two quantitative catheter culture methods was compared in a prospective study of central venous arterial catheters. The roll-plate method followed by sonication was used to culture 177 catheters from 85 patients, and the sonication method was used to culture 136 catheters from 68 patients. All patients were evaluated for catheter-related infections. Catheter-related infections were associated with greater than or equal to 100 colony-forming units (CFU) isolated from catheter tips by either roll plate (p = 0.01) or sonication (p less than 0.001). The sensitivity, specificity, and positive and negative predictive values of greater than or equal to 10(3) CFU by roll plate for catheter-related septicemia were 56%, 97%, 63%, and 96% compared with 93%, 95%, 76%, and 99%, respectively, for the same level by sonication. For central venous and arterial catheters, the sonication method can distinguish infection from contamination and is superior to the roll-plate method in that it may offer a more sensitive and predictive alternative in the diagnosis of catheter-related septicemia.

Pharmacokinetics of intravenous immunoglobulin (Gammagard) in bone marrow transplant patients

The pharmacokinetics of an intravenous immunoglobulin (IVIG), Gammagard (Baxter Healthcare Corp., Glendale, CA), were measured in 31 cytomegalovirus (CMV) antibody negative bone marrow transplant (BMT) patients as part of a multicenter efficacy trial of 2 weekly dose regimens. Since all patients lacked antibody to CMV and received only screened CMV negative blood products, the half-life of the exogenous CMV antibody could be measured with an ELISA assay. The CMV antibody titer was related to the immunoglobulin concentration using a standard curve. Compared with the 22-day half-life in normal subjects, the half-life in BMT patients was approximately 6 days for either the 250 mg/kg or 500 mg/kg dose regimen. The half-life did not change over the subsequent 3 weekly doses. Peak concentrations were 3.5 +/- 1.4 and 2.6 +/- 0.7 mg/mL of IVIG in week 1 as well as 5.5 +/- 2.6 and 3.4 +/- 1.2 mg/mL in week 3 after the 250 mg/kg and 500 mg/kg, respectively. Total body clearance of IVIG was 0.61 and 0.46 mL/kg/hr for the 500 mg/kg and 250 mg/kg, respectively.

A psycho-behavioral model of genital herpes recurrence

To develop a model of how stress and other psychosocial constructs may interact to explain recurrences of genital herpes, assessments of major and minor life stress, locus of control, arousal or stimulation seeking, and social support were given to 153 university students (33% male; 67% female) who were seropositive for genital herpes. Retrospective and concurrent indices of illness vulnerability were evaluated. Serum levels of thymosin-alpha-1, a peptide sensitive to psychosocial stress, were measured at the beginning of the study. A causal model suggested by previous research was not supported by the data. An alternate model showed that psychosocial stress did not affect herpes recurrence directly, but instead predisposed subjects to more generalized illnesses, which in turn mediated recurrences. Social support increased rather than decreased the likelihood of illness vulnerability, thus increasing the risk of recurrence. Higher levels of both arousal seeking and external locus of control increased illness vulnerability but moderated the likelihood of herpes recurrence. Higher levels of thymosin-alpha-1 were related to greater illness vulnerability but this peptide was not associated with psychosocial stress as originally predicted. Additional construct validation of the role of illness vulnerability in increasing the risk of herpes recurrence is recommended.