Detection of streptomycin residues in whole milk using an optical immunobiosensor.

The development of an assay for the detection of streptomycin residues in pasteurized whole milk using an optical biosensor (Biacore) is reported. Streptomycin-adipic hydrazide coupled to bovine thyroglobulin was used to produce a sheep polyclonal antibody. The antibody displayed excellent cross-reactivity with dihydrostreptomycin (106%). There was no significant cross-reaction with other aminoglycosides or common antibiotics. Streptomycin was also immobilized onto a CM5 sensor chip to provide a stable, reusable surface. The developed assay permitted the direct analysis of whole milk samples ( approximately 3.5% fat) without prior centrifugation and defatting. Results were available in 5 min. The limit of detection of the assay was determined as 4.1 ng/mL, well below the European maximum residue limit (MRL) of 200 ng/mL. Repeatability (or coefficient of variation) between runs was determined as 3.5% (100 ng/mL; 0.5 x MRL), 5.7% (200 ng/mL; MRL), and 7.6% (400 ng/mL; 2 x MRL).

Evaluation of an immunobiosensor for the on-site testing of veterinary drug residues at an abattoir. Screening for sulfamethazine in pigs.

A study was conducted to determine the feasibility of performing "on-site" screening for sulfamethazine (SMT), at an abattoir, using a rapid immunobiosensor method. This involved transfer of the biosensor technology and an assay developed in the laboratory, to the cold, humid conditions of a modern pig-processing factory. A pre-determined threshold limit of 0.4 microgram ml-1 SMT in bile was used to identify the likelihood that corresponding tissue samples contained SMT concentrations in excess of the European maximum permissible residue limit of 0.1 mg kg-1. Bile samples containing SMT concentrations above the threshold limit were deemed positive and the corresponding kidney and muscle samples were sent to the laboratory for HPLC analysis. The robustness of the biosensor instrumentation in the harsh operating conditions was monitored throughout the project. The performance of the assay, on-site, was assessed by the regular inclusion of QA samples and by the submission of control 'SMT-positive' pigs to the abattoir. Sampling procedures, identification and traceability were also under scrutiny. During the project, 337 (9.35%) of the total kill were tested for SMT residues, representing 75% of all producers submitting pigs for slaughter. Twelve animals, including the ten controls, gave positive bile results. HPLC analysis confirmed SMT residues in all 12 kidneys (11 in excess of the permissible level). Ten muscle samples also contained violative SMT levels. Throughout the project, the biosensor performed reliably, with no adverse reaction of any mechanical or electrical components. The SMT assay also performed reliably. This is the first report of a biosensor being used for 'on-site' drug screening.

Immunobiosensor--an alternative to enzyme immunoassay screening for residues of two sulfonamides in pigs.

A rapid immunoassay using an optical biosensor (BIAcore) for determining the presence of sulfamethazine (SMT) residues in pig bile was developed. The assay was used in a routine screening laboratory alongside a previously described biosensor method for sulfadiazine (SDZ). Sulfonamide bile concentrations, determined by enzyme immunoassay (EIA), have already been shown suitable for use in predicting the extent of sulfonamide accumulation in kidney. The ability of immunobiosensor based bile screening to predict violative tissue residues (greater than the maximum residue limit; MRL) was compared with results achieved using two conventional EIAs for two of these drug residues (SMT and SDZ). Analysis of 2081 samples for both sulphonamide residues, over an 8 month period, showed the false positive prediction rate of biosensor analysis to be 0.14% and 0.34% for SMT and SDZ, respectively, compared with false positive rates of 1.54% and 1.44% by EIA. Biosensor analysis showed no false negative predictions for either SMT or SDZ while EIA showed a false negative prediction rate of 0.14% for SMT and 0.24% for SDZ. The present study has clearly demonstrated that immunobiosensor assays can be developed for veterinary drug residue screening programmes. These methods have the potential for generating faster and more reliable results than conventional immunoassay methods.

Prospective study of histoplasmosis in patients infected with human immunodeficiency virus: incidence, risk factors, and pathophysiology.

Histoplasmosis is a common opportunistic infection in patients with human immunodeficiency virus (HIV) infection who reside in areas where Histoplasma capsulatum is endemic. We undertook a prospective study of a cohort of 304 HIV-Infected patients in Kansas City from October 1990 through March 1993 to define the incidence-specific risk factors, and pathophysiology of histoplasmosis. The annual incidence of histoplasmosis was 4.7%; 74% of the patients with histoplasmosis were symptomatic (all of whom had disseminated disease). A history of exposure to chicken coops, a positive baseline serology for complement-fixing antibodies to Histoplasma mycelium antigen, and a baseline CD4+ lymphocyte count of < 150/microL were associated with an increased risk for histoplasmosis. Histoplasmin reactivity and the presence of pulmonary calcifications were not useful markers for patients at high risk. Symptomatic infection occurred in 9.9% of patients with evidence of prior exposure to H. capsulatum, in 4.0% of patients without documented prior exposure, and in 3.0% of patients who were anergic; these findings suggest that the pathophysiology of histoplasmosis in patients with AIDS involves reactivation of latent infection in some cases and dissemination of exogenously acquired infection in other cases.

Dosing guidelines for foscarnet and trimetrexate.

The P & T Committee at Trinity Lutheran Hospital, a 320-bed, community/teaching hospital in Kansas City, MO, has developed dosing and monitoring guidelines for foscarnet sodium (Foscavir) and trimetrexate glucuronate (Neutrexin)--two drugs used to treat patients with opportunistic infections associated with the human immunodeficiency virus (HIV). Presented in this Experience Brief is a short discussion of these drugs, the rationale for guideline development, and the actual dosing and monitoring protocols devised.

Mycobacterium kansasii among patients infected with human immunodeficiency virus in Kansas City. Kansas City AIDS Research Consortium.

Previous reports of infection due to Mycobacterium kansasii among patients infected with human immunodeficiency virus (HIV) have conflicted with regard to the significance of the isolate; the clinical, radiographic, and laboratory features of the disease; and the response to therapy. To clarify the spectrum of M. kansasii infection in this population, we conducted a retrospective study of 35 patients. Twenty-eight of these patients were believed to have disease due to M. kansasii, while the remaining seven patients were probably colonized with the organism. All but two patients presented with advanced HIV infection; the median CD4 cell count was 12/microL. Most patients with pulmonary disease presented with fever, cough, and dyspnea, but only eight of these 22 patients had radiographic findings of either pulmonary cavitation or predominantly upper-lobe disease. Ten patients had M. kansasii isolated from blood or bone marrow. The majority of patients with pulmonary or disseminated disease responded to therapy. However, 11 patients died either before mycobacterial infection was diagnosed or early in the course of treatment, and two had a relapse of infection during therapy.

Histoplasmosis in Missouri: historical review and current clinical concepts.

Histoplasmosis is particularly common in Missouri, and many important clinical observations about the disease were made in this state in the 1950s and 1960s. When the AIDS epidemic spread to Missouri in the mid-1980s, histoplasmosis became recognized as a common and important opportunistic infection among Missourians with AIDS. Clinicians must maintain a high level of suspicion for histoplasmosis in any HIV-infected patient who presents with unexplained fever, particularly if the patient has evidence of hepatosplenomegaly, generalized lymphadenopathy, pancytopenia, abnormal liver function tests, or bilateral pulmonary infiltrates. The diagnosis of histoplasmosis can be established rapidly by observation of organisms on peripheral blood smear or bone marrow biopsy specimens or by Histoplasma Polysaccharide Antigen testing. The diagnosis can be confirmed by blood cultures in most cases. Histoplasmosis in AIDS is invariably fatal if not treated. Treatment consists of two phases: initial induction therapy and subsequent lifelong maintenance therapy. Amphotericin B and itraconazole are extremely effective for induction and maintenance therapy; fluconazole appears to be effective maintenance therapy. Strategies for the prevention of histoplasmosis in high risk patients are being evaluated currently.

Women's business.

For Aboriginals, matters relating to reproduction are private and the preserve of women alone. At least one factor contributing to the high maternal and perinatal mortality in Aboriginals is the cultural inappropriateness of current health services. Future planning of maternal health services will be more effective if cultural imperatives of Aboriginal women are made a priority.

Serratia marcescens bacteremia.

Serratia marcescens bacteremia has become ubiquitous recently. S. marcescens bacteremia, either hospital- or community-acquired, can no longer be treated as insignificant. We reviewed 23 episodes of S. marcescens bacteremia in 1985. Among them, 17 patients (74%) were hospital-acquired infections, while 6 (26%) were community-acquired. Nine patients died, and the case fatality rate was 39%. Eleven patients (48%) had no clinically apparent source of infection, 5 (22%) had urinary tract infection, 3 (13%) had pneumonia, 2 (9%) had biliary tract infection, 1 (4%) had intra-abdominal infection, and 1 (4%) had skin and soft-tissue infection. Nosocomial isolates are often resistant to many antibiotics. Amikacin and the beta-lactamase-stable (third generation) cephalosporins are superior to gentamicin in the treatment of nosocomial S. marcescens bacteremia. We here emphasize that the awareness and treatment of S. marcescens bacteremia in daily clinical practice is unequivocally critical.

Short-course treatment of bacteremia with ceftriaxone monotherapy.

The efficacy of short-course ceftriaxone monotherapy in treatment of bacteremia was evaluated in an open protocol. Patients with laboratory-proven bacteremia were randomly treated with one of three dosing schedules for a duration of 5 to 7 days. Fifty-seven (62%) out of the 92 evaluable infections had successful results. Successful responses were seen in 20 (59%) out of 34 infections given 4 g every 24 hours, 15 (54%) out of 28 given 2 g every 12 hours, and 22 out (73%) of 30 given 2 g every 24 hours. The results showed no significant differences. The cases evaluated as failures were largely due to infections with resistant organisms or inadequate drainage of the primary infectious foci. Forty-nine (94%) of the 52 infections had successful results with one of the short-course treatment regimens, provided that they had no factors indicative of a poor prognosis. We stress the importance of anti-microbial susceptibility and adequate removal of the primary foci in the treatment of bacteremia. Our experience indicates that once-daily administrations of 2 g ceftriaxone as monotherapy is preferred for short-course treatment of bacteremia since it is equally effective, but more economical than higher dose regimens.

Changing caesarean section rates. Experience at a Sydney obstetric teaching hospital.

The Caesarean section rate has been rising in Australia in recent years. This study compares Caesarean section rates and indications for Caesarean section in 2 separate 2-year periods, 1970-71 and 1980-81, in a Sydney teaching hospital. The Caesarean section rate increased from 6.4% to 16.2% in this decade. Dystocia is now the most frequent indication for Caesarean section and accounted for 33.2% of the increase in rate while fetal distress contributed 23.8% of that increase. Repeat Caesarean section and breech presentation contributed 16.9% and 13.3% of the increase respectively. Caesarean section rates for all birthweights increased, but particularly in the very small infant and those above 3,500 g. Caesarean sections for public patients rose from 3.4% to 9.3% while for private patients the rate increased from 12.0% to 20.7%. While there has been some convergence of rates for public and private patients during the decade, private patients were still twice as likely to have a Caesarean section in 1980-81. The contribution of dystocia, as an indication for Caesarean section, to the increase in the rate over this period is consistent with recent international experience and indicates a strong trend towards procedural intervention.

Raised hypoxanthine, xanthine and uridine concentrations in meconium stained amniotic fluid and during labour.

Amniotic fluid samples were obtained at induction of labour in 64 women; in 15 of these there was meconium staining of the amniotic fluid; the remainder showed no signs of fetal distress. Using high pressure liquid chromatography, compared to the samples from normal patients there were highly significantly raised levels of hypoxanthine, xanthine and uridine in the meconium stained samples; oxypurines in the meconium itself could not explain the difference. Where serial samples were obtained during labour by intrauterine catheter, a terminal rise in oxypurine levels was apparent. Where the proportion of oxypurine present as hypoxanthine exceeded one per cent in amniotic fluid at the time of induction, there was a significantly greater occurrence of late fetal heart rate decelerations in the ensuing labour. These findings are consistent with other evidence that when tissues become hypoxic the metabolic products of nucleotide breakdown escape from the cells and appear in extracellular fluid. Oxygen lack in the fetus probably causes loss of these compounds from the hypoxic kidneys to the urine so that they appear in amniotic fluid.

The measurement of hypoxanthine, xanthine, inosine and uridine in umbilical cord blood and fetal scalp blood samples as a measure of fetal hypoxia.

Hypoxanthine, xanthine, inosine, urate and uridine, were measured in 149 samples of umbilical cord plasma using high pressure liquid chromatography. In spite of a good correlation with the simpler oxygen consumption method for measuring hypoxanthine, there was no clear discrimination between hypoxic and well oxygenated infants, although mean concentrations were higher in infants with well defined criteria of intrapartum hypoxia or bith asphyxia, there was overlap with the normal range. Fetal scalp blood samples were also found to be clinically unhelpful in the diagnosis of intrapartum hypoxia, at least in part due to variable degrees of haemolysis in the specimens. There were poor correlations between hypoxanthine concentrations and those of hydrogen ion, base deficit and lactate. Uridine concentrations were significantly higher in arterial cord blood than in venous cord blood but hypoxanthine or xanthine concentrations did not show this difference.

The merits of special antenatal care for twin pregnancies.

A combined series of 101 twin pregnancies for whom routine hospital rest during the last trimester was replaced by intensified antenatal care in a special twins clinic was studied. Perinatal mortality and morbidity was similar to that found in a comparison group of 137 twin pregnancies under the care of consultants and not referred to the twins clinic. Routine cervical assessments and uterine activity measurements were unhelpful in predicting premature delivery. Urinary oestrogens and ultrasonic measurements of fetal biparietal diameter were of little or no value in predicting weight for gestational age but the ultrasonic measurement of abdominal circumference provided limited information on fetal growth. The contribution of a placebo effect to the results of patients receiving more personalised care cannot be discounted.

Failure of epidural morphine to relieve pain in labour.

Lumbar epidural injections of 2 mg preservative-free morphine were given to 10 subjects in established labour. Assessment of pain using a visual analogue scoring system revealed no appreciable relief of pain 30 min after morphine infection. Analgesia was subsequently provided by epidural injection of 8 ml bupivacaine 0.375%. Failure of epidural 2 mg in the treatment of severe pain other than labour. Possible explanations for this discrepancy are discussed.