Optimal testing parameters for blood cultures.

The effects of volume of blood, number of consecutive cultures, and incubation time on pathogen recovery were evaluated for 37,568 blood cultures tested with the automated BACTEC 9240 instrument (Becton Dickinson Diagnostic Instrument Systems) at a tertiary care center over the period of 12 June 1996 through 12 October 1997. When the results for this study were compared with previous data published for manual broth-based blood culture systems and patient samples obtained in the 1970s and 1980s, the following were found: (1) the percentage increase in pathogen recovery per milliliter of blood is less, (2) more consecutive blood culture sets over a 24-h period are required to detect bloodstream pathogens, and (3) a shorter duration of incubation is required to diagnose bloodstream infections. Guidelines developed in the 1970s and 1980s for processing and culturing blood may require revision.

Antimicrobial susceptibility of Abiotrophia adiacens and Abiotrophia defectiva.

The susceptibilities of 27 Abiotrophia adiacens (proposed reclassification Granulicatella adiacens comb.nov., Collins & Lawson, 2000) and 12 Abiotrophia defectiva isolates were tested by microdilution in pyridoxal hydrochloride and lysed horse blood supplemented Mueller-Hinton broth. According to NCCLS interpretative criteria for Streptococcus spp. not Streptococcus pneumoniae, the susceptibilities of A. adiacens and A. defectiva were, respectively: penicillin, 55% and 8%; amoxicillin, 81% and 92%; ceftriaxone, 63% and 83%; meropenem, 96% and 100%; and 100% for both species with clindamycin, rifampin, levofloxacin, ofloxacin, quinupristin/dalfopristin, and vancomycin.

An assessment battery for identifying language impairment in African American children.

This investigation compares the performances of 24 African American children, diagnosed as language impaired (LI) and receiving school-based language therapy, to 2 groups of typically developing peers (N = 48) on 5 traditional types of language assessment measures. Three of the measures were derived from child-centered free play language sample analyses and included average length of communication units (MLCU), frequencies of complex syntax, and numbers of different words. Two of the measures examined language comprehension and included responses to requests for information in the form of Wh-questions and responses to probes of active and passive sentence constructions. The performances of the group of children with language impairments were significantly lower on each measure than that of chronological age matched African American children who were typically developing. Sensitivity and specificity of the battery appeared excellent. The findings are discussed in terms of the potential of these informal language measures to contribute to a culturally fair assessment protocol for young African American children.

Screening and confirmatory testing for extended spectrum beta-lactamases (ESBL) in Escherichia coli, Klebsiella pneumoniae, and Klebsiella oxytoca clinical isolates.

Escherichia coli and Klebsiella spp. were screened for ESBL based on routine susceptibility testing results. Isolates with intermediate or resistant susceptibilities for extended spectrum cephalosporins or aztreonam were reported as probable ESBL producers. By using the NCCLS proposed ESBL confirmatory method, we tested 61 screen-positive isolates from 42 patients, 30 randomly selected susceptible isolates, and 12 isolates with previously characterized beta-lactamases. Ceftazidime contributed to 97% of screen-positive isolates, whereas aztreonam added a single patient isolate. An ESBL was confirmed in 86% of K. pneumoniae, 100% of K. oxytoca, and 20% of E. coli screen-positive single patient isolates. None of the susceptible isolates were shown to produce ESBL. Based on these findings a comment regarding the presence of ESBL seems sufficient for Klebsiella spp. but confirmatory testing is indicated for E. coli. 0.25 microg/mL was used to indicate the presence of ESBL, the specificity of the assay increased to 100%. The NCCLS ESBL phenotypic confirmatory method was reproducible and accurate enough to be used in the clinical laboratory.

Reassessment of the routine anaerobic culture and incubation time in the BacT/Alert FAN blood culture bottles.

A total of 9,130 blood cultures were collected from adult patients with suspected bloodstream infections. The recommended 20 mL sample of blood was divided equally between the aerobic and anaerobic FAN bottles and monitored in the BacT/Alert Microbial Detection System for a total of 5 days. There were 757 clinically significant positive culture pairs from 291 patients. Significant differences were found with greater recovery of Pseudomonas aeruginosa (p < 0.001), Acinetobacter spp. (p = 0.002), coagulase-negative staphylococci other than Staphylococcus epidermidis (p = 0.002), and Candida spp. (p < 0.001) from the aerobic bottle and greater recovery of anaerobic bacteria (p < 0.001) from the anaerobic bottle. Significantly more episodes of P. aeruginosa bacteremia (p < 0.003) and candidemia (p < 0.001) were detected by the aerobic FAN bottle and significantly more episodes of anaerobic bacteremia (p < 0.001) were detected by the anaerobic FAN bottle (Table 2). No other significant differences between systems in their detection of bacteremias were noted. Anaerobic bacteremias were encountered in diverse and often unpredictable clinical settings. All clinically significant episodes of bloodstream infection were detected within 4 days of incubation of their cultures. We conclude routine, rather than selective, use of the anaerobic FAN bottle in the blood culture set and a 4-day incubation of blood cultures in the BacT/Alert aerobic and anaerobic FAN bottles is an appropriate routine procedure.

Reassessment of the incubation time in a controlled clinical comparison of the BacT/Alert aerobic FAN bottle and standard anaerobic bottle used aerobically for the detection of bloodstream infections.

This study assessed the minimum incubation time required to detect bloodstream infections during a controlled clinical comparison of the performance characteristics of the BacT/Alert aerobic FAN bottle and the standard anaerobic bottle used aerobically except on a selective basis. Blood was collected from adults with suspected bloodstream infections and inoculated into each bottle, which was monitored in the BacT/Alert Microbial Detection System. The anaerobic bottle was vented before incubation except when cultures were obtained from patients on the colorectal and gynecologic surgical and emergency services. Statistical analysis was limited to those culture sets in which each bottle was inoculated with > or = 8 mL of blood and bacterial growth was considered to be clinically significant. A total of 682 positive cultures from 243 patients satisfied the inclusion criteria. Significantly more isolates of Staphylococcus aureus (p < 0.001), S. epidermidis (p < 0.001), other coagulase-negative staphylococci (p < 0.001), Enterococcus spp. (p = 0.04), Escherichia coli (p = 0.03), all Enterobacteriaceae (p < 0.001), Pseudomonas aeruginosa (p = 0.001), and Candida spp. (p < 0.001) were detected by the aerobic FAN bottle. Significantly more septic episodes due to S. aureus, S. epidermidis, other coagulase-negative staphylococci, Enterobacteriaceae, P. aeruginosa, and Candida spp. were detected by the aerobic FAN bottle. Significantly more bacterial isolates were detected by the aerobic FAN whether or not antibiotics were being administered at the time of blood culture, whereas there were significantly fewer positive cultures in the vented standard anaerobic bottle when patients were receiving antimicrobial therapy than when they were not. All but 5% of positive cultures were detected within three days. Only six of the cultures requiring four or five days of incubation represented true misses, and only one of these six resulted in a change in therapy which, however, did not affect the patent's outcome.

Variable use of African American English across two language sampling context.

This investigation compares the impact of two language sampling elicitation contexts, free play and picture description, on variability in the use of African American English (AAE). Subjects were 65 normally-developing African American 4;4- to 6;3-year-old boys and girls from lower socioeconomic status homes. Comparisons of AAE production in the first 50 C units revealed significant differences by context. Picture descriptions elicited more AAE usage overall, a larger set of AAE types, and took less time. Gender differences in the use of AAE tokens were also apparent, with the boys using significantly more tokens than girls in the free play context. The use of AAE types and tokens was comparable for boys and girls in the picture description context. The advantages of language sampling with pictures to determine dialect usage is discussed.

The diagnostic usefulness of bone marrow cultures in patients with fever of unknown origin.

Bone marrow cultures (BMCs) and blood cultures (BCs) are frequently obtained in the evaluation of fever of unknown origin (FUO). However, the low yield of clinically significant isolates leads to questions about their cost-effectiveness. We retrospectively compared BMC with BC and studied the usefulness of bone marrow trephine biopsy (BMTB) histopathology in detecting infection in an unselected population of 61 patients with FUO, among whom 215 BMCs had been performed. For patients who had undergone BMTB, the histopathology was evaluated for granulomas and microorganisms. Only 1 BMC had a clinically significant isolate, Mycobacterium avium complex (MAC), which was also identified by BC. Rhodotorula rubra was found in the BMC of another patient and classified as a contaminant. Both patients had HIV infection. No growth occurred in BCs for the other 59 patients. Culture results for all 26 BMTB specimens were negative; 4 contained nonnecrotizing granulomas, including the case with MAC. BMCs are probably not justified for routine initial evaluation of FUO, but may be valuable after culture results for blood and easily obtainable tissues have been negative. Bone marrow histopathology and special stains for microorganisms in the absence of granulomas were noncontributory.

Socioeconomic status and gender influences on children's dialectal variations.

This investigation compares dialect use by African American children differing in socioeconomic status (SES) and gender. Subjects were 5- and 6-year-old boys (n = 30) and girls (n = 36), who were kindergartners attending schools in the Metropolitan Detroit area. Comparisons of the amount of dialect in the children's spontaneous discourse revealed systematic differences relative to SES and gender in the frequencies but not the forms of dialect in use. Children from lower-income homes, and boys, were more marked dialect users than their middle-class peers or girls. The sociolinguistic implications of the findings are discussed.

Average C-unit lengths in the discourse of African American children from low-income, urban homes.

This investigation reports average length of communication units (C-units) in words and in morphemes for 95 4- to 6 1/2-year-old African American boys and girls from lower-income homes in metropolitan Detroit. Mean C-units increased across the age span of this sample, and kindergartners produced significantly longer C-units than preschoolers. The syntactic complexity of the children's language samples correlated positively with increases in C-unit length, and regression analyses revealed that syntactic complexity was the best predictor of mean C-unit length. Children with longer average C-unit lengths produced greater frequencies of all types of syntactic complexity. Their language samples were distinguished from children with shorter mean C-unit lengths by clauses linked with coordinate and subordinate conjunctions. The findings indicate that average C-unit length will be useful as a quantitative index of linguistic growth in research designs focusing on young school-age African American children living in poverty.

Performances of young African American children on two comprehension tasks.

This investigation examines the performances of 63 urban 4- to 7-year-old African American children from middle-income homes on two tasks designed to assess the development of comprehension skills. Performances on a task designed to elicit responses to wh-questions, and another to distinctions between active and passive sentence constructions, revealed grade effects and a positive relationship to age. The findings are discussed in terms of the appropriateness of using tasks of these types with young African American boys and girls who are dialect users.

Antimicrobial susceptibility testing of a clinical isolate of vancomycin-dependent enterococcus using D-alanine-D-alanine as a growth supplement.

Bacteremia due to a vancomycin-dependent enterococcus (VDE) occurred during long-term vancomycin therapy in a renal transplant recipient with underlying pancreatitis and a vancomycin-resistant enterococcal (VRE) wound infection and bacteremia. The VDE was isolated from blood during vancomycin therapy and grew only in the presence of vancomycin and D-alanine-D-alanine (DADA), a substance required for cell-wall synthesis. Colonies beyond the periphery of growth of the VDE around a vancomycin disk contained vancomycin-independent revertant mutants after 48 hours of incubation. Pulsed-field gel electrophoresis of the VDE, revertant mutant, the initial blood culture isolate of VRE, and an autopsy isolate showed that the four strains were identical. Antimicrobial susceptibility testing was performed using standard macrobroth and microbroth dilution methods. DADA was used as a growth supplement for macrobroth dilution susceptibility testing of the VDE isolate. Minimum inhibitory concentrations (MICs) were similar for the VRE isolate and the VDE revertant, which were both resistant to ampicillin, high-level gentamicin, ciprofloxacin, imipenem, vancomycin, and daptomycin, and were susceptible to fusidic acid, high-level streptomycin, rifampin, and a quinupristin-dalfopristin combination. The MICs of teicoplanin were 2 microg/mL or less and 16 microg/mL for the clinical VRE isolate and the VDE revertant, respectively. The autopsy isolate was resistant to all antimicrobials tested and showed a fourfold increase in MICs for quinupristin-dalfopristin compared with that of the original blood isolate. The VDE was susceptible to all drugs tested except vancomycin.

Lactobacillus bacteremia and endocarditis: review of 45 cases.

Lactobacilli are part of normal gastrointestinal and genitourinary flora but are an uncommon cause of bacteremia. We reviewed the cases of 45 patients with clinically significant lactobacillus bacteremia occurring over 15 years. Underlying conditions were common, including cancer (40%), recent surgery (38%), and diabetes mellitus (27%). Twenty-two patients were in the intensive care unit at the time of onset of lactobacillus bacteremia. Eleven of the 45 patients were receiving immunosuppressive therapy, 11 were receiving total parenteral nutrition, and 23 had received antibiotics without activity against Lactobacillus prior to the occurrence of bacteremia. Bacteremia was polymicrobial in 27 patients and developed during hospitalization in 39. Thirty-one patients died, but only one death was attributable to lactobacillus bacteremia. Lactobacilli are relatively avirulent pathogens that produce bacteremia in patients with serious underlying illnesses, many of whom have received prior antibiotic therapy that may select out for the organism. While rarely fatal in itself, lactobacillus bacteremia identifies patients with serious and rapidly fatal illness.

Imipenem and meropenem activity against mecA-positive homogeneously and heterogeneously oxacillin-resistant and mecA-negative oxacillin-borderline-susceptible staphylococci.

Microbroth dilution and disk-diffusion testing of imipenem and meropenem was performed at 35 and 30 degrees C against 61 phenotypic expression class 3,4 and 9 phenotypic expression class 1,2 oxacillin-resistant isolates of Staphylococcus aureus (ORSA), 51 oxacillin-borderline-susceptible isolates of S. aureus (BORSA), and 37 phenotypic expression class 3,4 and 9 phenotypic expression class 1,2 isolates of Staphylococcus epidermidis (ORSE). Imipenem MIC ranges at 35 degree C were 0.6 to > 64 micrograms/ml for class 3,4 ORSA, 0.03 to 0.25 micrograms/ml for class 1,2 ORSA, 0.015 to 0.12 micrograms/ml for BORSA, 0.03 to 64 micrograms/ml for class 3,4 ORSE, and 0.12 to 8 micrograms/ml for class 1,2 ORSE. Corresponding values for meropenem were 0.5 to 64 micrograms/ml, 0.12 to 4 micrograms/ml, 0.06 to 1 microgram/ml, 0.5 to 64 micrograms/ml, and 1 to 8 microgram/ml. MIC ranges at 30 degrees C did not differ by more than 1 log2 dilution from those at 35 degrees C. After 24 h incubation of disk-diffusion tests at 35 degrees C, 44% of class 3,4 and 100% of class 1,2 ORSA isolates were imipenem-susceptible; after an additional 24 h at 25 degrees C, 39 and 100% of these isolates, respectively, remained susceptible to imipenem. Similar values were obtained with 24 h incubation at 30 degrees C followed by 24 h at 25 degrees C. All BORSA isolates were susceptible to imipenem. Of the ORSE isolates, 22 and 78% of isolates in classes 3,4 and 1,2, respectively, were susceptible at 24 h with little change after an additional 24 h at 25 degrees C. Similar trends were observed with meropenem. In parallel disk-diffusion studies with oxacillin, false-susceptibility rates of 5% of class 3,4 and 44% class 1,2 ORSA isolates after 24 h of incubation at 35 degrees C were reduced to 3 and 0%, respectively, after an additional 24 h of incubation at 25 degrees C. Imipenem- and meropenem-resistant subpopulations of oxacillin-resistant staphylococci did not seem to be detected by altered susceptibility testing conditions.

Antimicrobial resistance in Neisseria gonorrhoeae in the United States, 1988-1994: the emergence of decreased susceptibility to the fluoroquinolones.

Antimicrobial susceptibilities of Neisseria gonorrhoeae have been prospectively determined in the Gonococcal Isolate Surveillance Project of the Centers for Disease Control and Prevention. From 1988 through 1994, susceptibilities were determined for 35,263 isolates from 27 clinics. Patients were demographically similar to those in nationally reported gonorrhea cases. In 1994, 30.5% of isolates had chromosomally or plasmid-mediated resistance to penicillin or tetracycline. Penicillin resistance increased from 1988 (8.4%) to 1991 (19.5%) and then decreased in 1994 (15.6%). Tetracycline resistance decreased from 1988 (23.4%) to 1989 (17.3%) and then increased in 1994 (21.7%). Most isolates (99.9%) were highly susceptible to broad-spectrum cephalosporins. Isolates with decreased susceptibility to ciprofloxacin increased from 1991 (0.4%) to 1994 (1.3%); 4 isolates were ciprofloxacin-resistant. Ciprofloxacin-resistant strains may not respond to therapy with recommended doses of fluoroquinolones, and the clinical importance of strains with decreased susceptibility is unknown. The emergence of fluoroquinolone resistance in N. gonorrhoeae in the United States threatens the future utility of this class of antimicrobials for gonorrhea therapy.

A 1994-95 survey of Haemophilus influenzae susceptibility to ten orally administered agents. A 187 clinical laboratory center sample in the United States.

During August, 1994 to April, 1995, a total of 2278 clinical isolates of Haemophilus influenzae were obtained from 187 clinical laboratories in the United States (U.S.). The vast majority of these isolates (75%) were from respiratory sites, and the remaining organisms were from blood, ear, eye, and spinal fluid sources. The overall rate of beta-lactamase production and ampicillin resistance was 36%. The antimicrobial susceptibility of isolates was determined by reference broth microdilution testing against ten orally administered agents. MIC values were compared according to 12 geographical regions, inpatient or outpatient status, gender, and eight age groupings. Modest and occasionally significant differences were observed: 1) greater numbers of beta-lactamase-producing strains among outpatients, in males, in the mid-Atlantic region, and in children < or = 12 years of age; 2) lower prevalence of beta-lactamase-producing isolates in the Southeast and Pacific regions; 3) cefaclor, cefprozil, and loracarbef activity was lowest among the younger children (< or = six years); and 4) macrolide in vitro efficacy was lowest in patients > 50 years of age and in three eastern regions. Overall, more than 99% of the strains were susceptible to amoxicillin/clavulanic acid, cefixime, and cefpodoxime (e.g., widest potential clinical use). Susceptibilities using National Committee for Clinical Laboratory Standards (NCCLS) breakpoint criteria for the other agents were: 96.6% to cefuroxime, 86.5% to loracarbef, 84.0% to clarithromycin, 81.8% to cefaclor, and 80.7% to cefprozil. Non-beta-lactamase mechanisms of resistance to ampicillin were rare (0.2%) or episodic and were attributed to altered penicillin-binding proteins. Although there is an increased prevalence of beta-lactamase production among H. influenzae isolates compared to prior years, four beta-lactams remain highly active (> 95% susceptibility) against contemporary strains of H. influenzae. Other monitored compounds seem to have declined in spectrum and surveillance trials for resistance among H. influenzae isolates should continue in an effort to identify trends in the U.S.