Population density-dependent regulation of the Bradyrhizobium japonicum nodulation genes.

The nodulation genes of Bradyrhizobium japonicum are essential for infection and establishment of a nitrogen-fixing symbiosis. Here, we demonstrate that plant-produced isoflavones induce nodulation gene expression in a population density-dependent fashion. Nodulation gene induction is highest at a low population density and significantly reduced in more dense cultures. A quorum signal molecule in the conditioned medium of B. japonicum cultures mediates this repression. Repression in response to the quorum signal results from the induction of NolA which, in turn, induces NodD2 leading to inhibition of nod gene expression. Consistent with this, nolA-lacZ and nodD2-lacZ expression increased with increasing population density. Unlike the wild type, the ability to induce nodY-lacZ expression did not decline with population density in a NolA mutant. Normally, nod gene expression is repressed in planta (i.e. within nodules). However, expression of a nodY-GUS fusion was not repressed in a NolA mutant, suggesting that quorum-sensing control may mediate in planta repression of the nod genes. Addition of conditioned medium to cultures significantly reduced nod gene expression. Treatment of inoculant cultures with conditioned medium also reduced the ability of B. japonicum to nodulate soybean plants.

Child and adolescent traumatic brain injury: correlates of disruptive behaviour disorders.

A record review focused on children and adolescents, with a history of traumatic brain injury (TBI), who were consecutively admitted to a brain injury clinic in which all new patients are psychiatrically evaluated. Correlates of post-injury oppositional defiant disorder/conduct disorder (ODD/CD) and post-injury attention deficit hyperactivity disorder (AHD) were investigated. Subjects who developed ODD/CD following TBI, when compared to subjects without a lifetime history of the disorder, had significantly more impaired family functioning, showed a trend toward a greater family history of alcohol dependence/abuse and suffered a milder TBI. In contrast, there were no variables which discriminated between subjects who developed ADHD following injury and those with no lifetime history of ADHD. It is difficult to determine whether ODD, CD and ADHD occurring after TBI in the patient is related to the TBI, directly or indirectly. Appropriate clinical assessment requires consideration of the important mediating role of family functioning, severity of injury and family psychiatric history.

Child and adolescent traumatic brain injury: correlates of injury severity.

A record review focused on children and adolescents, with a history of traumatic brain injury, who were consecutively admitted to a brain injury clinic in which all new patients are psychiatrically evaluated. Significant correlates of severity of injury in the cognitive, education and communication domains of functioning included Performance IQ but not Verbal IQ nor standardized ratings of language or learning disability. Current organic personality syndrome (OPS) but not attention deficit hyperactivity disorder or oppositional defiant disorder/conduct disorder diagnostic status was significantly related to severity. In conclusion, the findings in this referred sample are similar to prospective studies indicating that Performance IQ appears sensitive in reflecting brain damage. The finding linking OPS to severity of injury is not surprising. This is because OPS is a diagnosis which is dependent on the clinician's judgment of the likelihood that the organic factor is etiologically related to a defined behavioural syndrome. The diagnosis therefore requires a clinical judgment that the threshold of severity of a presumed organic etiological factor has been reached.

Child and adolescent traumatic brain injury: psychiatric findings from a paediatric outpatient specialty clinic.

A record review focused on children and adolescents, with a history of traumatic brain injury, who were consecutively admitted to a brain injury clinic in which all new patients are psychiatrically evaluated. The development of a 'novel' psychiatric disorder (not present before injury) occurred in 76% (38/50) of the cohort and was correlated significantly with family psychiatric history and family function, but not with severity of injury, preinjury psychiatric status, intellectual/educational functioning, or socioeconomic status. Psychiatric consultation is often necessary in this paediatric population even though much of the psychopathology, particularly following mild injury, may not be directly related to brain trauma.

Creating the environment for process improvement.

The incorporation of quality improvement methods into the practice of laboratory medicine has become widespread in recent years. However, a significant number of laboratory professionals feel that quality improvement efforts take an excessive amount of time to achieve results. Using quality improvement methods and tools will have limited success without first creating the proper environment. Steps that we have found to be beneficial in creating the environment for successful improvement activities using the FOCUS-PDSA model include having senior leaders perform specific activities, aiming the team, and strategic contracting.

Identification of gram-negative bacilli using the Autobac IDX.

The Autobac IDX is a new system for the rapid identification of clinically significant members of the Enterobacteriaceae and Aeromonas, Acinetobacter, Alcaligenes, Flavobacterium, Moraxella, and Pseudomonas species. The use of 18 differentially inhibitory compounds such as dyes and antibiotics along with a computerized algorithm based on a multivariate analysis provides the basis for the identification of 30 different groups of gram-negative bacilli. Required preliminary tests include observations on the presence or absence of swarming on a sheep blood agar plate and noting the following: growth, lactose fermentation, and bile precipitation from a MacConkey plate. Spot indole and spot oxidase tests must be performed as well. Identification by the Autobac IDX System takes 3-6 hr after completion of the preliminary tests. From a total of 403 isolates tested, the Autobac system agreed with the MicroID AND N/F systems on 382 identifications (94.8%). Four isolates, two Acinetobacter anitratus, one Serratia marcescens and one Moraxella osloensis could not be identified by IDX. Additional testing was required on 35 (8.7%) of the isolates.

Acridine orange staining and radiometric detection of microorganisms in blood cultures.

To determine whether acridine orange (AO) staining of blood cultures could be used as a substitute for blind subculture when used in conjunction with the BACTEC system (Johnston Laboratories, Inc., Towson, Md.), the two methods were compared on all BACTEC-negative specimens. Since blind subcultures were routinely performed in our laboratory on days 2 and 6 of incubation, AO staining was also performed on these days. Cultures which were BACTEC positive on day 1 of incubation were not included in the study. Of the 2,395 bottles tested after 2 days of incubation, 106 were subculture positive. Of these, 96 (90.6%) were also AO positive and BACTEC positive, 3 (2.8%) were AO positive and BACTEC negative, and 7 (6.6%) were AO negative and BACTEC positive. Of the 3,487 bottles tested on day 6 of incubation, 14 were subculture positive; 7 (50%) of these were AO positive and BACTEC positive, and seven were AO positive and BACTEC negative. Of the total of 10 culture-positive bottles missed by BACTEC, all were positive, and all 10 companion aerobic bottles were BACTEC positive. In both phases of the experiment, there was a total of only four false-positive AO stains. As a result of this investigation, we have substituted AO staining for blind subculturing of BACTEC-negative bottles.

Rapid detection of Haemophilus influenzae type b in cerebrospinal fluid by commercial coagglutination and latex agglutination kits.

The ability of two commercial kits to detect Haemophilus influenzae type b antigen in cerebrospinal fluid was evaluated. Results obtained by Bactogen, a latex agglutination test, and Phadebact, a coagglutination test, were compared to counterimmunoelectrophoresis, Gram stain and culture results. One hundred and seven specimens of cerebrospinal fluid were tested. Thirty were found to contain bacteria, 20 of which were Haemophilus influenzae type b. All 20 were positive by Bactogen and Phadebact testing, 19 were culture positive, 18 were positive by counterimmunoelectrophoresis and 15 had gram-negative bacilli seen on Gram stain. The culture negative specimen contained microscopically visible gram-negative bacilli and was from a patient on antimicrobial therapy who was previously Haemophilus influenzae type b culture positive. No false positives from other genera or the 77 culture negative specimens occurred with Phadebact, Bactogen or counterimmunoelectrophoresis.