Blood culture series benefit may be limited to selected clinical conditions: time to reassess.

Blood cultures are often submitted as series (two to three sets per 24 hours) to maximize sample recovery. We assessed the actual benefit of additional sets. Blood cultures submitted from adults (≥ 18 years old) over 1 year (1 February 2012 to 31 January 2013) were examined. The medical records of patients with positive cultures were reviewed. Cultures with commensal organisms were considered contamination in the absence of a source and clinical findings. The impact of additional sets on antibiotic therapy was estimated. We evaluated 15,394 blood cultures. They were submitted as two to five sets per 24 hours in 12,236 (79.5%) instances. Pathogens were detected in 1227 sets, representing 741 bacteremias, of which 618 (83.4%) were detected in the first set and 123 (16.6%) in the additional sets. Pathogens missed in the first set were recovered from patients receiving antibiotics (n = 72; 58.5%) and after undergoing a procedure (n = 54; 43.9%). The additional sets' results could have influenced antibiotic therapy in 76/6235 (1.2%) instances, including 40 (0.6%) antibiotic switches and 36 (0.6%) possible extensions of therapy. The potential impact of the detection of missed pathogens on antibiotic therapy was not apparent in patients who had an endovascular infection (26/27, 96.3%) and those who lacked an obvious source of pathogens (10/10, 100%). These findings suggest that one blood culture is probably adequate in patients with an obvious source of pathogens. Blood culture series are beneficial in patients without an obvious source of pathogens and in those with endovascular infections. It is time to reassess the benefit of blood culture series, perhaps limiting them to selected conditions.

Keeping up with new technology: new approaches to diagnosis of Chlamydia infection.

Chlamydia trachomatis infections are among the most common sexually transmitted infections in the US today. One of the keys to the prevention of C. trachomatis infection rests on the ability to make this diagnosis on the basis of accurate laboratory testing. For many years the standard for diagnosis of C. trachomatis infections has been isolation in tissue culture. Numerous nonculture methods, including enzyme immunoassay, have been used as an alternative to cell culture. The performance characteristics of these tests have all been compared with a standard, cell culture, which at best will detect 90% of positive specimens. Nucleic acid amplification techniques, including PCR and ligase chain reaction, have been recently introduced. The advantage of these tests is their ability to detect 10-20% more positive specimens when compared with culture or confirmed nonculture methods performed with a single specimen. The sensitivity of amplified tests also allows us to test specimens from multiple sites (endocervix, urethra, urine), which expands our standard from an infected sample to detection of an infected patient. Tests based on amplified nucleic acid technology have greatly improved our ability to diagnose urogenital C. trachomatis infection. The use of an expanded standard will help us accurately define the true performance and clinical utility of nonculture Chlamydia diagnostic tests.

Comparison of five methods for the determination of rubella immunity.

OBJECTIVE: The purpose of this study was to compare the accuracy of commonly used methods for the detection of rubella immunity, especially the fully automated IMx assay. METHODS: A total of 190 sera (101 immune and 89 non-immune) submitted to Harrisburg Hospital or Polyclinic Medical Center for the determination of rubella immunity were tested by enzyme immunoassay (IMx and Rubazyme, Abbott Diagnostic Laboratories, North Chicago, IL), indirect immunofluorescence (FIAX, Whittaker Bioproducts, Walkersville, MD), and latex agglutination (Rubascan, Becton Dickinson Microbiology Systems, Cockeysville, MD, and Rubalex, Wellcome Diagnostics, Research Triangle Park, NC). Specimens were frozen at -30 until the study was initiated. Each of the assays was performed according to the manufacturers' specifications. Sensitivity, specificity, accuracy, and positive and negative predictive values for each assay were calculated using a consensus result of the 5 methods tested. RESULTS: The sensitivity, specificity, and accuracy, respectively, of the test systems were as follows: IMx, 96%, 97%, and 96%; Rubazyme, 100%, 99%, and 99%; Rubascan, 100%, 98%, and 99%; Rubalex, 99%, 97%, and 98%; and FIAX 90%, 100%, and 95%. False negative reactions were seen with the FIAX system. CONCLUSIONS: The IMx system, a new "walk away" system from Abbott Diagnostic Laboratories and the Rubazyme systems performed well; however the latex agglutination tests proved to be the most rapid and convenient methods for screening sera for the presence of rubella immunity.

Prevalence of Hepatitis C virus antibody in patients with sexually transmitted diseases attending a Harrisburg, PA, STD clinic.

OBJECTIVE: The prevalence of hepatitis B and hepatitis C in a sexually transmitted disease (STD) clinic population was studied, along with the prevalence of various STD agents, in an attempt to identify possible STD markers for the hepatitis C virus and help delineate the role of hepatitis C as an STD. The hepatitis C antibody rates found in the STD clinic were also compared with those found among patients attending a local OB/GYN clinic and those enrolled in a blood donor program, all from the same geographical area. METHODS: A total of 150 women attending an STD clinc were examined for each of the following agents: Chlamyadia trachomatis, Neisseria gonorrhoeae, syphilis, hepatitis B surface antigen, hepatitis B core antibody, hepatitis B surface antibody, and hepatitis C virus antibody. Additionally, several patients who signed informed consent to be evaluated for human immunodeficiency virus (HIV) antibody were tested by an enzyme immunoassay (EIA) screen method. The prevalence of each agent was then compared with the other agents. RESULTS: The overall prevalence rates detected were as follows: hepatitis B 16%, hepatitis C 4%, chlamydia 18.7%, gonorrhea 7.4%, syphilis 0.7%, and HIV 0%. Hepatitis C antibody was detected in 4% of patients in the STD clinic, 0.76% of volunteer blood donors from central Pennsylvania, and 0% of patiants studied from the Harrisburg Hospital (Harrisburg, PA) prentatal population. CONCLUSIONS: This screening study reveals an association between attending a Harrisburg, PA, area STD clinic and having an increased prevalence of hepatitis C antibody, but larger matched control studies will be needed to help clarify sexual transmission as a mode of transmission for the hepatitis C virus.

Evaluation of two rapid tests for the diagnosis of Chlamydia trachomatis genital infections.

The performance of two new enzyme immunoassays (EIA) for the detection of Chlamydia trachomatis in a practice setting was compared. A consecutive series of 207 female patients seen at an inner-city sexually transmitted disease clinic were tested by cell culture, the Kodak SureCell (SC) and Abbott TestPack Chlamydia (TP) EIAs. In addition 210 male patients, selected by physicians on the basis of the fact that multiple urethral samples could be obtained, were tested by cell culture and SC. The prevalence of infection was 19% in the females and 12.5% in males. The sensitivity, specificity, positive predictive value and negative predictive value for the SC and TP were 88%, 95%, 81%, 97% and 59%, 99%, 95%, 91%, respectively, in the female population. The sensitivity of the SC was significantly greater than that of the TP (p less than or equal to 0.002). The performance values of the SC in men (in the same order) were 64%, 96%, 71% and 95%, respectively. The SC in male patients and the TP in female patients had low sensitivity. The sensitivity of the SC in female patients was significantly higher than that of the TP. However, the SC yielded more false positive results. To determine the utility of these tests in a practice setting further studies are required.

Comparison of the Kallested Pathfinder EIA, cytocentrifuged direct fluorescent antibody, and cell culture for the detection of Chlamydia trachomatis.

A total of 203 duplicate endocervical samples collected from patients at an adolescent health care center were tested for the presence of Chlamydia trachomatis by cell culture, Pathfinder enzyme immunoassay (EIA) (Kallestad) and cytocentrifuged direct fluorescent antibody (DFA). Compared to cell culture, the Pathfinder assay demonstrated a sensitivity and specificity of 85.2% and 100%, whereas the DFA procedure demonstrated to be 92.6% sensitive and 99.4% specific.

Comparison of three new nonculture tests in the diagnosis of Chlamydia genital infections.

This study compares three new rapid nonculture tests to cell culture with passage for the diagnosis of Chlamydia genital infections in sexually active adolescent and young adult females. Two hundred consecutive patients having a pelvic examination had cervical samples taken for the following: Papanicolaou smear, gonorrhea culture, Chlamydia cell culture, direct fluorescent antibody (DFA; Difco), isotopic DNA probe (Gen-Probe), and enzyme immunoassay (EIA; IDEIA III, Novo BioLabs). After resolution of discrepant results, 25 of the specimens were judged to be positive. The DFA identified 17 of the 25, with 3 false-positive results; the DNA probe identified 20 of the 25, with no false positive results; and the EIA identified 22 of the 25, with one false-positive result. The sensitivities, specificities, and positive and negative predictive values, respectively, were DFA, 68%, 98.2%, 85%, 95.5%; DNA probe, 80%, 100%, 100%, 97.2%; and EIA, 88%, 99.4%, 95.6%, 98.3%. These new rapid nonculture tests are comparable and relatively reliable, with trends favoring the EIA and the DNA probe. Further studies with larger samples are needed to determine their clinical utility.

In-hospital anaerobic susceptibility testing: an aid to formulary decision making.

In this study, the susceptibility of 116 recent anaerobic isolates, including the Bacteroides fragilis group (n = 22), Bacteroides spp (n = 65), gram-positive cocci (n = 13), Clostridium spp (n = 10), and Fusobacterium spp (n = 6) were tested by agar dilution against a variety of agents suggested for prophylaxis or therapy. These agents included ampicillin sodium and sulbactam sodium, cefotaxime, cefoxitin, ceftizoxime, clindamycin, imipenem-cilastatin, metronidazole, and ticarcillin and clavulanate potassium. All anaerobes demonstrated 100% susceptibility to imipenem-cilastatin, metronidazole, ampicillin sodium and sulbactam sodium, and ticarcillin and clavulate potassium. Varying degrees of susceptibility (ranging from 60% to 100%) of Bacteroides spp to the selected panel of antibiotics were seen. Fusobacterium spp and the gram-positive cocci were inhibited by all agents tested. Clostridium spp was 90% susceptible to cefoxitin, 80% susceptible to clindamycin, and 100% susceptible to the other six agents. Due to the varying activity of these agents, local susceptibility patterns, antimicrobic spectrum, and cost effectiveness must be considered in the choice of agents used for empiric therapy.

Evaluation of latex agglutination and dot immunobinding assay for the detection of cytomegalovirus antibody.

The Virogen CMV Antibody Test and Difco CMV-Cube were compared with three other available methods, enzyme immunoassay, immunofluorescence and latex agglutination, for the detection of cytomegalovirus (CMV) antibody in 126 random sera submitted to the clinical laboratory. Based on concordance of three or more methods, 72% of the samples were positive for CMV antibody. The sensitivities and specificities of the assays were Virogen, 98% and 97%, and CMV-Cube 97% and 97%, respectively.

Comparison of IDEIA III and cell culture for the detection of Chlamydia trachomatis in endocervical specimens.

A total of 803 endocervical samples were obtained from females with clinical or epidemiological histories suggesting chlamydia infection. These specimens were tested by IDEIA III and cell culture for the presence of Chlamydia trachomatis. After resolution of discrepant results by direct fluorescent-antibody staining of pelleted cell culture transport materials, IDEIA III demonstrated sensitivity, specificity, and positive and negative predictive values of 93.8, 99, 92.9, and 99.1%, respectively.

Comparison of DNA probe, monoclonal antibody enzyme immunoassay, and cell culture for the detection of Chlamydia trachomatis.

A total of 201 endocervical specimens were obtained from patients with a clinical or epidemiological history suggestive of chlamydial infection. These specimens were tested by DNA probe (Gen-Probe, San Diego, Calif.) and the IDEIA III (Boots-Celltech, Berkshire, United Kingdom) monoclonal antibody enzyme immunoassay and compared with cell culture for detection of Chlamydia trachomatis. Discrepancies between cell culture and antigen detection methods were resolved by direct fluorescent-antibody testing. In a population with a 17.4% prevalence, the sensitivities and specificities of these assays were 82.8 and 99.4%, respectively, for the DNA probe assay and 97.1 and 98.1%, respectively, for the IDEIA III.

Comparison of a rapid latex agglutination assay and a fluorescent-antibody technique for the detection of herpes simplex antibody.

A total of 202 serum specimens was tested for the presence of herpes simplex virus antibody using a premarket latex agglutination kit (Wampole) and an indirect fluorescent antibody (IFA) technique (electronucleonics). Discrepant results between the two assays were resolved using an Enzyme-linked immunosorbent assay (ELISA) procedure. The overall sensitivity of the latex was 99.2% with a specificity of 98.5%. The latex agglutination test evaluated is a viable alternative to indirect immunofluorescence for the detection of herpes simplex virus antibody in serum samples.

Sepsis from Flavobacterium meningosepticum, an uncommon pathogen with unusual susceptibility patterns.

Flavobacterium meningosepticum, because of its unusual susceptibility patterns and predilection for debilitated or immunocompromised hosts, can be a dangerous pathogen. Identification of the organism and proper susceptibility studies, which are essential in designing antibiotic therapy, helped in the selection of a regimen that proved curative in this case.