Faculty Bibliography

Since the year 2000, linezolid has been used in the United States to treat infections caused by antimicrobial-resistant Gram-positive cocci. At present, linezolid-resistant (Linr) Staphylococcus aureus and Staphylococcus epidermidis strains are rare and the diversity of their genetic backgrounds is unknown. We performed sequence-based strain typing and resistance gene characterization of 46 Linr isolates that were collected from local and national sources between the years 2004 and 2007. Resistance was found to occur in at least three clonal complexes (CCs; lineages) of S. aureus and in at least four subclusters of a predominant, phylogenetically unstable CC of S. epidermidis. New candidate resistance mutations in 23S rRNA and the L4 riboprotein were identified among the S. epidermidis isolates. These findings suggest that linezolid resistance has emerged independently in multiple clones of S. aureus and with a variety of ribosomal mutations in multiple clones of S. epidermidis

OBJECTIVE: We describe the first outbreak of multiple drug-resistant Acinetobacter baumannii (MDR-Ab) in a neonatal intensive care unit in the United States. DESIGN/METHODS: MDR-Ab was identified in the blood of a 24-week gestation, 7-day-old extremely low birth weight neonate. Multiple samplings of surveillance surface cultures were performed on exposed and nonexposed neonates. Enhanced infection control measures were implemented. Pulsed-field gel electrophoresis was performed to determine the genetic relatedness of the MDR-Ab isolates. Medical records were reviewed for all exposed patients. RESULTS: MDR-Ab was recovered from 6 additional neonates. Of these 7 MDR-Ab (index + 6) neonates, 4 died, 3 of whom had positive blood cultures. All affected neonates were born between 23 to 26 weeks gestational age, and were <7 days postnatal age and <750 g (430-720) at the time of exposure. All were housed within the same room as the index case. None of the other 5 exposed neonates older than postnatal day 7 or weighing >750 g at birth were affected. No additional cases occurred outside the original room. Pulsed-field gel electrophoresis was consistent with a clonal origin, identical to MDR-Ab recovered from the referring hospital. CONCLUSIONS: This MDR-Ab outbreak was rapidly controlled with enhanced infection control measures and was novel in that it affected only <750 g neonates, at < or =26 weeks gestational age, and < or =7 days postnatal age at the time of exposure, suggesting that invasive Ab has a special affinity for damaged or nonkeratinized immature skin in developmentally immature immunologic hosts

BACKGROUND: In 2004, a 650-bed, tertiary care medical center experienced an outbreak of multiple antibiotic-resistant Klebsiella pneumoniae (MR-KP) that included extended-spectrum beta-lactamase (ESBL)-producing and non-ESBL-producing strains. METHODS: Characteristics associated with MR-KP were evaluated by case-control study with variables tested by conditional regression analyses. Pulsed-field gel electrophoresis (PFGE) was used to compare the molecular relatedness of isolates. RESULTS: In 2004, the incidence rate of MR-KP increased significantly compared with 2003 (relative risk [RR], 5.1; 95% confidence interval [CI]: 3.10-8.37) when only ESBL-producing K pneumoniae were present. The increase involved both ESBL-producing MR-KP and MR-KP in which ESBL production was not detected by the testing in use. Nineteen isolates were identical or closely related by PFGE. Characteristics associated with MR-KP were longer length of hospital stay (odds ratio [OR], 2.92; 95% CI: 1.17-7.30; P = .022), greater total antibiotic-days (OR, 2.81; 95% CI: 1.19-6.65; P = .018], and higher Acute Physiology and Chronic Health Evaluation (APACHE) II score (OR, 1.15; 95% CI: 1.06-1.25; P = .001). When the MR-KP cases were subdivided into ESBL-producing K pneumoniae and ESBL-negative K pneumoniae, while controlling for length of stay, total antibiotic-days was significantly associated with ESBL-producing K pneumoniae (OR, 3.8; 95% CI: 1.2-12.1; P = .02). CONCLUSION: Compared with patients housed on the same unit at the same time, patients with MR-KP had a longer length of stay and greater antibiotic exposure. Patients with longer length of stay and greater total antibiotic exposure should be potential targets for stringent infection control measures

This article describes the laboratory modalities available to confirm the diagnosis of Lyme borreliosis. Use and limitations of these methods are discussed. Current guidelines for the use of recommended serologic methods and discussion of newer methods also are provided

Erythema migrans, the most common manifestation of Lyme disease, has been associated with highly variable rates of seropositivity for antibodies to Borrelia burgdorferi. Differences in the sensitivities of serologic assays for the detection of these antibodies, however, may not be the only or even the primary explanation for this observation. We investigated the impacts of four clinical variables on seropositivity--the duration of erythema migrans, the presence of single versus multiple skin lesions, and the gender and age of the patient. In this analysis, three different serologic tests were performed on acute-phase sera from 175 untreated patients with culture-confirmed erythema migrans: the C6 single-peptide enzyme-linked immunosorbent assay (ELISA), a commercially available ELISA in which a whole-cell sonicate of B. burgdorferi was the antigen, and a two-tier procedure. Irrespective of the serologic test performed, the results showed that seropositivity rates increased with the duration of the erythema migrans for patients with single lesions (P < 0.001) but not for those with multiple skin lesions. The variability in seropositivity rates was greatest for the two-tier testing strategy, with a >6-fold-higher rate of seropositivity among patients with a single lesion of 22- to 30-day duration than among those whose skin lesion was of 1- to 7-day duration (85.7 versus 14.1%; P < 0.001). Rates of seropositivity by each of the testing methods were also significantly higher for patients with multiple skin lesions than for those with single lesions (P < 0.001). In contrast, seropositivity rates were not affected by either the gender or the age of the patient. Thus, in patients with erythema migrans, certain clinical variables such as the duration and number of skin lesions had a profound impact on seropositivity rates, irrespective of the serologic assay performed

BACKGROUND: A potential concern with any serologic test to detect antibodies to Borrelia burgdorferi is whether the epitopes incorporated in the test provide sufficient cross-reactivity to detect infection with all of the pathogenic strains of the species. This is a particular concern for the C6 test, which is based on reactivity to a single peptide. METHODS: C6 testing and 2-tier testing were performed on acute-phase serum samples obtained from >158 patients with erythema migrans for whom the genotype of the borrelial isolate was defined on the basis of an analysis of the 16S-23S ribosomal DNA spacer region and/or on the genetic variation of the outer surface protein C gene (ospC). The sonicated whole cell-based enzyme-linked immunosorbent assay, the immunoblots used in the 2-tier testing, and the C6 assay all used antigens from B. burgdorferi sensu stricto strain B31. RESULTS: The sensitivity of C6 testing (69.5%) was greater than that of 2-tier testing (38.9%) (P<.001); the difference in sensitivity, however, was statistically significant only for patients infected with 2 of the 3 ribosomal spacer type-defined genotypes. The lower sensitivity of 2-tier testing was attributable to the low sensitivity of the immunoblot tests, rather than the first-tier enzyme-linked immunosorbent assay. There was also a trend for the sensitivity of 2-tier testing to vary according to the ospC genotype for the 14 genotypes represented in the study (P=.07); this relationship was not observed with C6 testing. CONCLUSIONS: Lack of sensitivity of the C6 test because of strain diversity seems less likely to be a limitation of this serologic test, compared with 2-tier testing in North American patients with early Lyme disease

BACKGROUND & AIMS. Microparticles are small membrane vesicles released from the cell plasma membrane, particularly in cell stress, apoptosis and altered cellular viability. Hepatocellular carcinoma (HCC) is a hypervascular neoplasm with high levels of apoptosis and necrosis. We investigated the levels of circulating microparticles of both tumor and endothelial origins in liver transplant patients with hepatitis C (HepC) cirrhosis with and without HCC and compared them with healthy people and patients with partial hepatectomy. METHODS. Using immunolabeling of microparticles of different origin and flow cytometry-based enumeration of microparticles, the levels of circulating microparticles were studied in 8 patients with HepC and 8 patients with both HepC and HCC before and within two weeks after the transplant. RESULTS. The initial levels of circulating microparticles were increased in patients with HepC and HCC as compared to patients with HepC alone. They were also increased in liver transplant patients as compared to patients with partial hepatectomy or healthy people. Levels of circulating microparticles were dynamically changing after the transplant, showing an initial increase with a subsequent decrease by the end of the second week after surgery. In some patients with a complicated clinical outcome, the levels of microparticles were continuously increasing after the surgery. CONCLUSION. The levels of circulating microparticles of endothelial and hepatic origin in liver transplant patients dynamically change after surgery and correlate with the clinical outcome. Perspectively, the levels of circulating microparticles may be used in clinical practice as a marker of the functional status of the transplanted liver

We describe the clinical and laboratory manifestations and pregnancy outcomes of 6 women who received a diagnosis of human granulocytic ehrlichiosis during pregnancy. Human granulocytic ehrlichiosis did not seem to present in a fulminant fashion, and all treated patients had excellent responses to rifampin or doxycycline therapy. Perinatal transmission was documented in 1 neonate, who responded well to treatment. There do not appear to be any long-term adverse sequelae in children born from these pregnancies (mean follow-up duration, 21 months)

Human granulocytic anaplasmosis (HGA) is a potentially fatal tick-borne infection caused by Anaplasma phagocytophilum. Treatment options are limited for this entity, with doxycycline being the drug of choice. Certain fluoroquinolones such as levofloxacin are active against A. phagocytophilum in vitro. We report a hospitalized patient with HGA who improved coincident with a 13-day course of levofloxacin therapy, but clinically and microbiologically relapsed 15 days after completion of treatment. Relapse of infection after levofloxacin therapy was reproduced in a severe combined immune-deficient (SCID) mouse infection model. Quinolone therapy should not be considered curative of HGA

A large amount of knowledge has been acquired since the original descriptions of Lyme borreliosis (LB) and of its causative agent, Borrelia burgdorferi sensu stricto. The complexity of the organism and the variations in the clinical manifestations of LB caused by the different B. burgdorferi sensu lato species were not then anticipated. Considerable improvement has been achieved in detection of B. burgdorferi sensu lato by culture, particularly of blood specimens during early stages of disease. Culturing plasma and increasing the volume of material cultured have accomplished this. Further improvements might be obtained if molecular methods are used for detection of growth in culture and if culture methods are automated. Unfortunately, culture is insensitive in extracutaneous manifestations of LB. PCR and culture have high sensitivity on skin samples of patients with EM whose diagnosis is based mostly on clinical recognition of the lesion. PCR on material obtained from extracutaneous sites is in general of low sensitivity, with the exception of synovial fluid. PCR on synovial fluid has shown a sensitivity of up to >90% (when using four different primer sets) in patients with untreated or partially treated Lyme arthritis, making it a helpful confirmatory test in these patients. Currently, the best use of PCR is for confirmation of the clinical diagnosis of suspected Lyme arthritis in patients who are IgG immunoblot positive. PCR should not be used as the sole laboratory modality to support a clinical diagnosis of extracutaneous LB. PCR positivity in seronegative patients suspected of having late manifestations of LB most likely represents a false-positive result. Because of difficulties in direct methods of detection, laboratory tests currently in use are mainly those detecting antibodies to B. burgdorferi sensu lato. Tests used to detect antibodies to B. burgdorferi sensu lato have evolved from the initial formats as more knowledge on the immunodominant antigens has been collected. The recommendation for two-tier testing was an attempt to standardize testing and improve specificity in the United States. First-tier assays using whole-cell sonicates of B. burgdorferi sensu lato need to be standardized in terms of antigen composition and detection threshold of specific immunoglobulin classes. The search for improved serologic tests has stimulated the development of recombinant protein antigens and the synthesis of specific peptides from immunodominant antigens. The use of these materials alone or in combination as the source of antigen in a single-tier immunoassay may someday replace the currently recommended two-tier testing strategy. Evaluation of these assays is currently being done, and there is evidence that certain of these antigens may be broadly cross-reactive with the B. burgdorferi sensu lato species causing LB in Europe