Controlled clinical comparison of BacT/alert FA plus and FN plus blood culture media with BacT/alert FA and FN blood culture media.

New blood culture media containing antibiotic-binding polymeric beads have been developed for the BacT/Alert (bioMérieux, Inc., Durham, NC) blood culture system. To assess the performance of these new media, we compared the new BacT/Alert aerobic medium (FA Plus) with resins to BacT/Alert FA medium with activated charcoal and the new BacT/Alert anaerobic medium (FN Plus) to BacT/Alert FN medium at 3 tertiary care medical centers. Study bottle pairs were inoculated with a target volume of 6 to 10 ml of blood from adults and incubated in the BacT/Alert 3D blood culture instrument. In the FA Plus versus FA comparison, there were 1,507 study pairs. Among 170 isolates causing true bloodstream infections (BSIs), significantly more Staphylococcus aureus (P<0.001) and total microorganisms (P<0.01) grew in the FA Plus bottle than in the FA bottle. Fewer coagulase-negative staphylococcal (CoNS) contaminants grew in the FA Plus bottle than in the FA bottle (10 versus 22; P=0.05). In addition, growth was detected earlier in the FA Plus bottle than in the FA bottle (P<0.001). In the FN Plus versus FN comparison, there were 2,386 study pairs. Among 201 isolates causing true BSIs, significantly more S. aureus (P<0.001), CoNS (P<0.005), and total microorganisms (P<0.001) grew in the FN Plus bottle than in the FN bottle. Also, significantly more CoNS contaminants grew in the FN Plus bottle than in the FN bottle (P<0.001). Overall, microorganisms were detected earlier in the FN Plus than in the FN bottle (P<0.001). Medical technologists at all 3 study sites preferred the new media for Gram stain interpretation. We conclude that the FA Plus and FN Plus media provide improved and earlier detection of microorganisms compared with the FA and FN media and are preferable for Gram stain interpretation as well.

A deceptive case of cellulitis caused by a Gram-negative pathogen.

Yokenella regensburgei is a member of the family Enterobacteriaceae that has rarely been implicated in clinical disease. We report here a case of septicemia with a skin and soft tissue source caused by Y. regensburgei in an immunocompromised host.

Controlled multicenter evaluation of a bacteriophage-based method for rapid detection of Staphylococcus aureus in positive blood cultures.

Staphylococci are a frequent cause of bloodstream infections (BSIs). Appropriate antibiotic treatment for BSIs may be delayed because conventional laboratory testing methods take 48 to 72 h to identify and characterize isolates from positive blood cultures. We evaluated a novel assay based on bacteriophage amplification that identifies Staphylococcus aureus and differentiates between methicillin-susceptible and methicillin-resistant S. aureus (MSSA and MRSA, respectively) in samples taken directly from signal-positive Bactec blood culture bottles within 24 h of positive signal, with results available within 5 h. The performance of the MicroPhage KeyPath MRSA/MSSA blood culture test was compared to conventional identification and susceptibility testing methods. At four sites, we collectively tested a total of 1,165 specimens, of which 1,116 were included in our analysis. Compared to standard methods, the KeyPath MRSA/MSSA blood culture test demonstrated a sensitivity, specificity, positive predictive value, and negative predictive value of 91.8%, 98.3%, 96.3%, and 96.1%, respectively, for correctly identifying S. aureus. Of those correctly identified as S. aureus (n = 334), 99.1% were correctly categorized as either MSSA or MRSA. Analysis of a subset of the data revealed that the KeyPath MRSA/MSSA blood culture test delivered results a median of 30 h sooner than conventional methods (a median of 46.9 h versus a median of 16.9 h). Although the sensitivity of the test in detecting S. aureus-positive samples is not high, its accuracy in determining methicillin resistance and susceptibility among positives is very high. These characteristics may enable earlier implementation of appropriate antibiotic treatment for many S. aureus BSI patients.

Lipid class dynamics and storage depots in juvenile weakfish Cynoscion regalis and their application to condition assessment.

Lipid class dynamics, the pattern of change in the primary form and location of lipid stores and their relationship with standard length (L(S) ), were investigated in collections of young-of-the-year weakfish Cynoscion regalis for the purpose of determining the utility of this analysis as an indication of condition. The separation of total lipids into individual classes and the analysis of potential storage depots revealed the general patterns of lipid class dynamics and energy storage in C. regalis during their period of juvenile estuarine residency. Phospholipid and cholesterol exhibited moderate but variable (8·1-40·0 and 1·3-21·5 mg g(-1) , respectively) concentrations across the entire juvenile period and were the predominant lipid classes in juveniles <100 mm L(S) , while wax ester concentrations were low (c. 1 mg g(-1) ) and exhibited the least amount of variability among lipid classes. Triacylglycerols (TAG) and free fatty acids (FFA) exhibited similar dynamics, with relatively low concentrations (<15 mg g(-1) ) in individuals ≤100 mm L(S) . In larger juveniles both TAG and FFA concentrations generally increased rapidly, though there was considerable variability in both measures (0·0-199·7 and 0·0-49·7 mg g(-1) , respectively). Increasing levels of lipids, primarily in the form of TAG, with size indicated an accumulation of energy reserves with growth, thus providing an indication of individual condition for larger juveniles. Separate analysis of liver, viscera and the remaining carcass indicated that liver and viscera did not represent a significant depot of TAG reserves. Analysis of samples derived from whole juvenile C. regalis thus provided an accurate estimate of energy reserves.

Is global climate change influencing the overwintering distribution of weakfish Cynoscion regalis?

The pattern of stable isotope signatures in a sub-sample of 67 juvenile weakfish Cynoscion regalis, captured at the mouth of the Christina River, 113 km upstream of the mouth of Delaware Bay (U.S.A) in the autumn of 2000, suggested that they resided at the location since recruitment. The possibility that young C. regalis departed from the generally characteristic life-history pattern of marine migrants at this latitude, i.e. emigrating offshore with the adults in autumn was bolstered by the collection of 69 individuals during the winters of 2000-2006 from the travelling screens of a power plant located at river kilometre 88 including an 118 mm total length juvenile captured in mid-February 2006.

Chronic encephalitis possibly due to herpes simplex virus: two cases.

Two patients had clinical findings of encephalopathy that progressed in 4 to 5 months. One patient had headache, fatigue, lethargy, hemiparesis, and a seizure. The second patient had only forgetfulness, confusion, and lethargy without focal signs. Herpes simplex virus was grown from brain biopsy in the first patient and from CSF in the second patient. These cases suggest that herpes simplex virus caused the encephalitis and that it should be considered in the differential diagnosis of chronic encephalopathy.

Clinical importance of "breakthrough" bacteremia.

Fifty-one episodes of bacteremia and a single episode of fungemia occurred during treatment with seemingly adequate doses of appropriate antibiotics. Clinical findings in these "breakthrough" bacteremias and fungemia were compared with those in 448 non-breakthrough episodes. Breakthrough was more likely to be caused by facultative or aerobic gram-negative rods (e.g., Enterobacteriaceae and Pseudomonas species) than by anaerobes. Of the underlying conditions examined, immunosuppressive doses of glucocorticosteroids, diabetes mellitus, and moderate renal failure were significantly more frequent in patients with breakthrough. A significant association was also observed between an intra-abdominal primary focus of infection (abscesses, biliary tract or bowel infections) and the occurrence of breakthrough. Mortality in breakthrough bacteremia was 61 percent compared with 40 percent in non-breakthrough episodes. The phenomenon of breakthrough bacteremia shows the potential limitations of antibiotic therapy alone.

Multicenter collaborative evaluation of a standardized serum bactericidal test as a predictor of therapeutic efficacy in acute and chronic osteomyelitis.

Forty-eight episodes of osteomyelitis, 30 acute and 18 chronic, were evaluated in a prospective multicenter collaborative study to determine whether a standardized serum bactericidal test could predict outcome of infection. All centers used a microdilution test method that defined the recognized important test variables, including inoculum size, culture medium, dilution technique, incubation time, method of subculture, and bactericidal endpoint. In patients with acute osteomyelitis, peak serum bactericidal titers had no predictive value; however, trough titers of 1:2 or greater accurately predicted cure, whereas trough titers of less than 1:2 predicted therapeutic failure. In patients with chronic osteomyelitis, peak serum bactericidal titers of 1:16 or greater and trough titers of 1:4 or greater accurately predicted cure, whereas peak titers of less than 1:16 and trough titers of less than 1:2 accurately predicted failure. It is concluded that this standardized serum bactericidal test provides good prognostic information in patients with osteomyelitis, and it is recommended that patients with acute osteomyelitis have serum bactericidal titers of 1:2 or greater at all times and that patients with chronic osteomyelitis have serum bactericidal titers of 1:4 or greater at all times.

Spontaneous bacterial peritonitis. A review of 28 cases with emphasis on improved survival and factors influencing prognosis.

During a five year period, 28 episodes of spontaneous bacterial peritonitis were documented. The number of cases recognized annually increased during the study period. Clinical and laboratory features of spontaneous bacterial peritonitis were similar to those previously reported; however, mortality was considerably lower (57 per cent). Factors associated with adverse prognosis were increasing hepatic encephalopathy, more than 85 per cent granulocytes in peripheral blood or ascitic fluid, total bilirubin greater than 8 mg/dl and serum albumin less than 2.5 g/dl. Temperature greater than 38 degrees C was associated with increased survival. Infection by enteric organisms was associated with higher mortality than infection by nonenteric organisms. Unexpectedly, patients with bacteremia fared no worse than those whose blood remained sterile. The data suggest that in patients with leukocyte counts greater than 1,000 cells/mm3 and more than 85 per cent granulocytes in their ascitic fluid, the likelihood of spontaneous bacterial peritonitis is high. Such patients deserve empiric antibiotic therapy pending the results of appropriate cultures.

Multicenter collaborative evaluation of a standardized serum bactericidal test as a prognostic indicator in infective endocarditis.

One hundred twenty-nine patients with bacterial endocarditis were evaluated in a multicenter collaborative study to determine whether a standardized serum bactericidal test could predict the outcome of the infection. All centers used a microdilution test method that defined all known test variables, including inoculum size, culture medium, dilution technique, incubation time, method of subculture, and bactericidal endpoint. Peak serum bactericidal titers of 1:64 or more and trough serum bactericidal titers of 1:32 or more predicted bacteriologic cure in all patients. The traditionally recommended serum bactericidal titer of 1:8 had statistically significant predictive accuracy at trough antibiotic levels only. The serum bactericidal test was a poor predictor of bacteriologic failure and ultimate clinical outcome, which depends on many factors. Wider recognition by physicians and clinical microbiologists that this in vitro test of antimicrobial activity can accurately predict bacteriologic success but cannot accurately predict either bacteriologic failure or clinical outcome could lead to a better consensus about its appropriate use. On the basis of the results of this study, peak serum bactericidal titers of 1:64 or more and trough serum bactericidal titers of 1:32 or more are recommended to provide optimal medical therapy for infective endocarditis.

Appropriate use of the microbiology laboratory in the diagnosis of infectious diseases.

The collection and processing of clinical specimens in the diagnosis of infectious diseases is reviewed. Available culture methods, other laboratory tests, and their appropriate use and interpretation are discussed. Particular emphasis is placed on selection of those tests most likely to give a specific diagnosis while avoiding unnecessary laboratory use.

Laboratory diagnosis of bacteremia and fungemia.

Many of the variables that affect the laboratory diagnosis of bacteremia and fungemia have been addressed in this article. Whereas the scientific basis and principles for blood cultures are well-established, and the methodology has improved, the diagnosis of bacteremia and fungemia still depends greatly on the care that is taken in obtaining the specimens of blood and the skill of the clinician in interpreting positive results.

Blood cultures.

Bacteremia and fungemia are encountered commonly and are associated with significant morbidity and mortality. Laboratory detection is therefore of paramount importance. Principles of successful blood culturing, clinically important technical issues, manual and automated detection systems, and interpretation of culture results are reviewed in this article.

Clinical evaluation of a urine transport kit with lyophilized preservative for culture, urinalysis, and sediment microscopy.

Comparative results of urine culture, specific gravity, chemical urinalysis, and sediment microscopy were assessed when specimens submitted to the clinical laboratory were divided and processed either in a transport kit containing a lyophilized preservative or in a conventional sterile cup without preservative. Overall agreement of results of 853 cultures after a 24-hr holding period (preserved samples at room temperature, unpreserved samples refrigerated) and 277 repeat cultures after a 48-hr holding period also showed excellent agreement (99.1% and 95.7%, respectively). Results of urinalysis and sediment microscopy done on 370 specimens demonstrated greater than 98% agreement after receipt of specimens in the laboratory and greater than 94% agreement after the holding periods. Specific gravity determinations from samples processed in the presence of preservative consistently were 0.006-0.007 units greater than in samples processed without preservative, and a reporting adjustment will be necessary when the transport kit is used.

Comparative in vitro activity of lomefloxacin and other antimicrobials against 597 microorganisms causing bacteremia.

The in vitro activity of lomefloxacin, a new fluorinated quinolone antimicrobial, was compared to that of enoxacin, norfloxacin, ofloxacin, imipenem, cefotaxime, ceftazidime, and tobramycin against 597 microorganisms isolated from bacteremic patients at a university hospital. Overall, lomefloxacin had activity similar to that of enoxacin and norfloxacin but less than that of ofloxacin. Lomefloxacin had excellent activity against members of the family Enterobacteriaceae and Haemophilus influenzae, and good activity against staphylococci, including oxacillin-resistant strains, as well as many strains of Pseudomonas aeruginosa, P. maltophilia, and Acinetobacter calcoaceticus anitratus ssp anitratus.

Qualitative intravascular catheter tip cultures do not predict catheter-related bacteremia.

During a 5-month period, we evaluated the sensitivity, specificity, and predictive value of qualitative cultures of intravenous catheters submitted to a university hospital microbiology laboratory. Of 36 catheters submitted for culture from nonseptic patients, 10 (28%) grew one or more microorganisms on qualitative culture. Of 44 catheters cultured from septic patients, 20 (45%) grew one or more microorganisms, but only 5 grew microorganisms that also were isolated from blood cultures. The sensitivity, specificity, and positive predictive values for catheter-related bacteremia were 71%, 96%, and 17%, values similar to those reported for quantitative methods. Although acceptable in terms of sensitivity and specificity, the very low positive predictive value suggests that catheter-related bacteremia cannot be predicted reliably by this test. We conclude, therefore, that nonstandardized qualitative IV catheter cultures have minimal value as predictors of bacteremia and recommend that they not be performed in clinical microbiology laboratories.

Comparison of one-day versus two-day incubation of urine cultures.

The value of incubating urine cultures for 1 versus 2 days was evaluated prospectively for 1526 consecutive specimens. A total of 507 cultures (33.2%) were positive after 1 day; 41 (2.7%) showed different results after 2 days. Only yeasts and corynebacteria were detected more often with longer incubation. Patient charts were available for review from 27 of 41 late positives; in only three instances (11.1%) was action taken by physicians based on these results.

Clinical importance of polymicrobial bacteremia.

Ninety-one episodes of polymicrobial bacteremia and fungemia were compared with 407 unimicrobial episodes to assess differences in the microbiological, epidemiological, and clinical features of the two syndromes. Enterobacteriaceae, nongroup A streptococci, anaerobic bacteria, and pseudomonads were disproportionately common in polymicrobial bacteremia. Polymicrobial episodes were significantly more likely to be hospital-acquired, to emanate from bowel or multiple foci, and to occur in patients with nonhematologic malignancies or multiple underlying diseases. Deaths directly related to sepsis were twofold higher in polymicrobial versus unimicrobial bacteremia. Factors associated with increased mortality in polymicrobial sepsis included age greater than 40 yr; absent or diminished febrile response to sepsis; absolute granulocytopenia; inadequate antimicrobial therapy for all microorganisms isolated; and a primary focus of infection in the bowel, the respiratory tract, an abscess, or an occult site. The occurrence and type of polymicrobial bacteremia can suggest a source of sepsis as well as additional diagnostic and therapeutic maneuvers.

Laboratory and clinical evaluation of Mycobacterium xenopi isolates.

Mycobacterium xenopi and Mycobacterium avium complex (MAC) are biochemically similar. To define the laboratory characteristics of M. xenopi that distinguish it from MAC, 53 M. xenopi isolates from different areas in the United States and 47 isolates recovered at one hospital were evaluated by 13 biochemical tests, AccuProbe MAC (Gen-Probe, Inc., San Diego, CA, USA), colony morphology, formation of X-colonies, pigmentation in response to light, growth on MacConkey agar without crystal violet, and relative growth rates at 25 degrees C, 36 degrees C, and 45 degrees C on solid media. Relative growth rates of 10 M. xenopi and 11 MAC isolates were measured at 25 degrees C, 36 degrees C, and 42 degrees C in Middlebrook broth processed using the BACTEC TB System. Ten M. xenopi were tested for p-nitro-alpha-acetylamino-beta-hydroxypropiophenone inhibition at 36 degrees C and 42 degrees C. Reevaluation of 81 isolates previously identified as MAC by biochemical tests alone revealed that two were M. xenopi. The most reliable characteristics distinguishing M. xenopi from MAC were the presence of X-colonies (M. xenopi 97% vs MAC 1%), positive 3-day arylsulfatase (M. xenopi 88% vs MAC 1%), growth at 25 degrees C (M. xenopi 0% vs MAC 100%), and AccuProbe MAC test results (M. xenopi 0% hybridized). Retrospective chart review of 37 patients using American Thoracic Society criteria revealed that six (16%) patients had clinically important isolates. At one of our hospitals M. xenopi was the second most common mycobacterial species isolated for 1990-1992, accounting for 27% of all isolates, whereas at our other hospital it accounted for 1% of isolates.(ABSTRACT TRUNCATED AT 250 WORDS)

Recovery of clinically important microorganisms from the BacT/Alert blood culture system does not require testing for seven days.

Recently, we published a comparison of the BacT/Alert blood culture system with the BACTEC 660/730 nonradiometric blood culture system using blood inocula of 5 ml per bottle. By reanalyzing data collected during that study, we found that, for true-positive isolates causing bacteremia or fungemia, 363 (97.6%) of 376 and 341 (97.7%) of 349 isolates were recovered by the end of day 5 of testing, and 364 (97.9%) of 376 and 343 (98.3%) of 349 isolates were recovered by the end of day 6 of testing for aerobic and anaerobic bottles, respectively. Most isolates recovered on days 6 (24 of 27) and 7 (20 of 25) of testing were either contaminants or indeterminate as a cause of sepsis. When used as recommended by the manufacturer, only six (1.3%) of 464 clinically important isolates recovered on test days 6-7 would have gone undetected had testing been limited to 5 days and four (0.9%) of 464 had testing been limited to 6 days. We conclude that BacT/Alert bottles can be tested for as few as 5 days and then discarded with minimal loss of true-positive isolates and maximal reduction of contaminants.