Diagnosis of bacteremia in children by quantitative direct plating and a radiometric procedure

Abstract

During a 1-year period, three bacteriological systems for detecting bacteremia in children were analyzed, namely, the BACTEC system (Johnston Laboratories, Inc., Cockeysville, Md.), the Fisher/Lederle bottle (Lederle Diagnostics, Pearl River, N.Y.), and a direct plating method of blood, termed quantitative direct plating (QDP). Of 2,123 blood cultures, 135 (6.4%) were positive; Haemophilus influenza type b, Neisseria meningitidis, and Streptococcus pneumoniae accounted for 3.4%, representing 61 patients, other pathogens accounted for 0.6%, and contaminants accounted for 2.4%. Of 72 cultures yielding H. influenza, N. meningitidis, and S. pneumoniae, 60 were recovered by both broth systems, 2 by BACTEC only and 10 by Fisher/Lederle bottle only. The BACTEC system failed to register a positive growth index reading by 24 h in 15 cultures which were positive for H. influenza, even though growth had occurred, as shown by positive subculture and microscopy at this time. QDP detected 89% of the cultures positive for H. influenza and N. meningitidis, of which 55% yielded results before either broth procedure. Only 50% of the cultures positive for S. pneumoniae yielded growth on QDP. This difference in the recovery rates probably is accounted for by the number of organisms in the blood. Thus, more than 100 organisms per mI of blood were found in 71% of cultures positive for H. influenza and N. meningitidis but in only 7% of those positive for S. pneumoniae. These studies, then, have revealed that H. influenza, which grew well in BACTEC broth, did not, however, give a significant growth index reading during day 1 of incubation, in contrast to N. meningitidis and S. pneumoniae. The QDP system not only provided information on the magnitude of bacteremia due to H. influenza and N. meningitidis but frequently allowed earlier diagnosis and, thus, proved to be a valuable, simple, and inexpensive supplementary technique for broth cultures, although not for the diagnosis of S. pneumoniae bacteremia.

Quantitation of bacteria in cerebrospinal fluid and blood of children with meningitis and its diagnostic significance

“…Furthermore, in relation to one of the objectives of the study to elucidate whether an association existed between bacterial counts in the CSF and the magnitude of bacteremia, 73% of the patients with H. influenza bacteremia and meningitis had counts in excess of 103 CFU/ml in blood as well as CSF. Similarly high concentrations of organisms in blood were previously noted by La Scolea et al (10) in children with H. influenza and N. meningitidis disease. The reason why such large concentrations of bacteria occur in CSF and blood is unclear.…”

“…The samples were placed in sterile tubes and had an average volume of 0.5 to 1.0 ml. Blood cultures were processed as previously described (9,10). In brief, the blood cultures consisted of BACTEC aerobic bottles that had attached quantitative direct plating heparin tubes.…”

Incidence of catheter-associated gram-negative bacteremia in children with short bowel syndrome

“…The number of organisms per milliliter was determined, and identification of all isolates was performed by conventional methods. The BACTEC system was used as described previously (6,15) and by using all the instructions of the manufacturer. The significance of clinical disease in relation to the organism isolated from the central line blood culture was determined by chi-square analysis.…”

Quantitative aspects of septicemia.

“…The magnitude of bacteremia in infants and children is generally greater than that in adults so cultures of as little as 0.5 to 1.0 ml of blood are considered adequate in most cases (94). Direct plating methods have been used in pediatrics to enhance the recovery of commonly encountered pathogens such as Haemophilus influenza and Neisseria meningitidis and to study the correlation between the magnitude of bacteremia and clinical manifestations (52,53).…”

“…Quantitative blood culture studies in pediatrics have used several methods, including pour plate (1, 25); spread plate (75); quantitative direct plating, using heparin tubes (53); and lysis direct plating, using the Isolator 1.5 Microbial Tube (10)(11)(12)98). La Scolea et al (53) described a quantitative direct plating method in which 0.5 to 1.0 ml of blood was collected into a heparin tube; upon arrival in the laboratory, the blood was inoculated onto agar plates. The quantitative direct plating method was compared with broth methods for detection of bacteremia in children (53).…”