Evaluation of buffy-coat microscopy for the early diagnosis of bacteraemia

Overwhelming pneumococcal bacteremia revealed by a peripheral blood smear in a 74-year-old healthy woman

A 76-year-old woman, who had never been seriously ill, was admitted to our hospital with fever and shaking chills. She progressively developed septic shock. We detected Streptococcus pneumoniae in a routine examination of a Giemsa-stained peripheral blood smear. Despite intensive care with antibiotic therapy, she died within several hours after admission. A peripheral blood smear occasionally shows bacteria in cases of overwhelming septicemia, thus indicating a severe impairment of splenic function. We suggest that, in cases of severe septicemia, an examination of a peripheral blood smear is therefore useful for the rapid detection of organisms in comparison to a traditional blood culture.

Aetiology and management of children with acute fever of unknown origin

This is part I of a 2-part paper on fever of unknown origin (FUO) in children. FUO is best defined as fever without obvious source on initial clinical examination and then classified into acute (illness of < or =1 week's duration) and prolonged (>7 to 10 days' duration). Aetiologically, there is a marked overlap between acute and prolonged FUO, and infections are major players in both. Age, climate, local epidemiology and host factors are the major aetiological factors that should be considered in the choice of definitive tests. Depending on age, serious bacterial infections (including bacteraemia, meningitis and urinary tract infection) occur in 3 to 20% of cases of acute FUO. Prevention of mortality and sequelae from these infections, particularly bacteraemia and meningitis, is of particular concern in acute FUO. An individualised approach, based on clinical evaluation supplemented with screening and definitive laboratory tests to determine the need for empiric antibiotic therapy and hospitalisation, seems to be the best approach to acute FUO (although this may be less applicable to neonates and infants younger than 90 days, particularly those aged 0 to 7 days). The place of laboratory tests, empiric antibiotic therapy and hospitalisation are important issues that are likely to remain so for some time.

Rapid diagnosis of bacteremia in adults using acridine orange stained buffy coat smears

The use of acridine orange stained buffy coat smears was assessed as a rapid screening test for bacteremia in adults. A total of 356 consecutive blood cultures were submitted with simultaneous anticoagulated blood samples, from which a buffy coat smear was prepared and stained with acridine orange (100 mg/L; pH 3.0). Forty-one of 356 blood samples (12%) yielded organisms in the blood culture system. Compared to blood culture, the overall sensitivity of acridine orange stained buffy coat smears was 16%, specificity 88%, and positive predictive value 13%. There was no statistically significant difference in performance of the test among patients who had fever greater than 39°C and/or shock. The low sensitivity and specificity of the test makes it unsuitable as a means of rapid screening for adults with suspected bacteremia.

Evaluation of direct and buffy coat films of peripheral blood for the early detection of bacteraemia

During an 8 month period, 298 evaluations of direct and buffy coat films of peripheral blood for the detection of bacteraemia were undertaken in 287 infants (243 less than 24 h of age and 55 aged between 2 days and 30 days). Bacteraemia was diagnosed by simultaneously drawn aerobic and anaerobic blood cultures. Intracellular organisms were observed in both the direct and buffy coat films of only four of 24 infants with bacteraemia, giving a sensitivity of 17%, specificity of 100% and positive and negative predictive values of 100% and 93%, respectively. Of 12 infants with bacteraemia on the first day of life, eight were asymptomatic when studied, and none of the 12 had positive smears. As two of four infants with positive smears died, it is concluded that in fulminating sepsis the tests seem to correlate with the degree of illness and may give useful information as to the causative organism and the choice of antibiotic. However, as a screening test, the present methodology lacks sensitivity and cost-effectiveness.

Group B meningococcal infection in children during an epidemic in Cape Town, South Africa

One hundred and thirteen children with meningococcal infection were studied during an epidemic caused by N. meningitidis group B. Fifteen per cent presented with only meningeal symptoms, the remainder showed signs of septicaemia or combined septicaemia and meningitis. Sixteen per cent of the children were in shock and 18% required admission to the Intensive Care Unit (ICU). The mortality was 4.4%. More than half the children were younger than 2 years old. There was no statistical association between the age or nutritional state of the children and any of our measures of severity. A short history of symptoms was more common in children who presented with septicaemia and severe illness, who needed admission to the ICU, or who died. Diagnosis was confirmed by routine bacteriological methods and counter-immuno-electrophoresis (CIE) in 104 children. Eighty-six per cent of the isolates were group B type 2. A history of recent antibiotic treatment was associated with fewer positive cultures, but detection of meningococcal antigen by CIE was not affected by this. CIE antigen detection was not reliable because of the high incidence of false-negative results.

Neonatal candida septicaemia: diagnosis on buffy smear

We report a case of neonatal candida septicaemia diagnosed by examination of a buffy smear. This would seem to be a fairly simple test for a disease where a good prognosis is dependent on rapid diagnosis and isolation using standard culture techniques is notoriously unforthcoming.

Use of buffy-coat smears in the diagnosis of septicaemia in children

Gram-stained buffy-coat smears from venous and capillary blood samples in 105 children suspected of septicaemia were examined for the presence of bacteria and the results compared with blood culture isolates. Gram-positive and Gram-negative bacteria were identified in 18 venous (44%) and 19 capillary (46%) buffy-coat preparations in 41 instances where bacterial organisms were isolated from the blood cultures. It is concluded that the examination of buffy-coat smears for bacteria in children suspected of septicaemia is a useful adjunct to blood cultures and, in areas where no facilities exist for culture of blood, may be a simple and rapid method of establishing the diagnosis of bacteraemia in suspected patients.

Nonculture techniques using blood specimens for the diagnosis of infectious disease

Recent technological advances have increased the use of blood as a source for diagnosis of local and systemic infectious diseases. Traditionally, viable organisms may be cultured from the blood and others identified microscopically. The ability to detect microbial products by physicochemical, bioactivity, and antigenic techniques and the ability to detect specific immunoglobulin M (IgM) responses to infection improve our diagnostic capabilities but also present new problems in determining clinical relevance. The diagnostic use and reproducibility of new tests should be verified by comparative clinical field testing before implementation.