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Case Report Submitted by Stephen C. Marker, M.D. Department ofLaboratory Medicine and Pathology University ofMinnesota, Minneapolis A 9-day-old girl was brought to the hospital because of irritability and a fever of 102°F. She was born to a gravida 7 native American after an uncomplicated full-term pregnancy. Labor, delivery and nursery course had been uncomplicated. There was an 18-month-old sibling at home with an upper respiratory infection. The patient's cerebrospinal fluid (CSF) contained 191 mgldl protein, 36 mgldl glucose, and 1254leukocytes/j.d. Gramstained smear showed no organisms, but Listeria monocytogenes was grown from the CSF culture. In addition, a blood culture obtained on the day of admission grew Escherichia coli. All subsequent cultures of CSF and blood taken after initiation of antibiotic therapy were sterile. She received ampicillin, gentamicin, and chloramphenicol. Gentamicin was discontinued after 4 days, whereas ampicillin and chloramphenicol therapy were continued for 17 days. She became afebrile after 48 hours and remained alert, active, and afebrile for the remainder of her
hospital course. On the 18th hospital day, the CSF protein was 91 mgldl, glucose was 42 mgldl, and there were 21 leukocytes/p I. The E. coli recovered from the initial blood culture was resistant to both ampicillin and cephalothin but susceptible to chloramphenicol, gentamicin, and kanamycin. L. monocytogenes isolated from the CSF was susceptible to ampicillin, penicillin, and chloramphenicol. In the laboratory, L. monocytogenes may be discarded as a contaminant because it resembles diphtheroids. Diphtheroids isolated from CSF and blood should be routinely tested for motility at 25 ° and 37°C. Isolates that are motile at room temperature and that grow as typically small, clear{J-hemolytic colonies on sheep blood agar may be presumptively identified as L. monocytogenes. Corynebacterium aquaticum is a motile diphtheroid, but its yellow colony morphology will distinguish it from L. monocytogenes. Colonies of L. monocytogenes on sheep blood agar may also resemble group B streptococci. Confusion may occur because both are hippurate-positive, and L. monocytogenes may appear initially as gram-positive cocci in young cultures before assuming their characteristic rod shape.
Questions & Answers Q. How can gram-negative cocci (Neisseria and Branhamella) be differentiated
morphologically from gram-negative coccoid rods (Moraxella and Acinetobacter)?
A. A very simple test to differentiate cocci from coccobacilli has been described byCatIin (J. Clin. Microbiol.l:102, 1975). A disc diffusion antibiotic susceptibility plate may be used; if a susceptibility has not been performed, streak the organism on a sheep blood or chocolate agar plate, and place 100unit penicillin discs on the plate in both the heavy and light areas of inoculation. Mter overnight
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incubation, some of the growth from the edge of the wne of inhibition around the penicillin disc is removed and suspended in a drop of saline on a slide. A #1 coverslip is applied and the preparation is observed under the oil immersion objective with reduced light. Neisseria and Branhamella will appear as cocci although they may be enlarged. Coccobacilli (Moraxella and Acinetobactcr, etc.) will appear as rods and long f1laments. The growth may also be examined after staining with crystal violet, but use of the Gram's stain may distort the organisms.
Occasionally, L. monocytogenes is0lates have been confused with enteroco. because the colonies are similar, and bo organisms give a positive bile-escuIin te A slide catalase test will readily differen tiate catalase-positive Listeria from cat, lase-negative streptococci. This patient with sepsis and meningit caused by two different organisms in th neonatal period was most unusual and I presented the simultaneous occurrence ( two classic neonatal infections in the sal infant. Neonatal L. monocytogenes infl tions, when acquired at the time of birtl usually become clinically manifest 1- 4 weeks postpartum as meninigitis. It seemed more probable that this child h, an immunologic defect. Her 18-monthold sibling subsequently developed a rapidly fatal necrotizing enterocolitis wi Candida sepsis and Candida meningitis This unlikely sequence of events no dOll reflects an underlying immunologic defl that has not yet been dermed in this fan ily. In the clinical microbiology laboratory, there is a need to be alert for secor organisms in otherwise seriously ill or ir munocompromised patients.
hospital course. On the 18th hospital day, the CSF protein was 91 mgldl, glucose was 42 mgldl, and there were 21 leukocytes/p I. The E. coli recovered from the initial blood culture was resistant to both ampicillin and cephalothin but susceptible to chloramphenicol, gentamicin, and kanamycin. L. monocytogenes isolated from the CSF was susceptible to ampicillin, penicillin, and chloramphenicol. In the laboratory, L. monocytogenes may be discarded as a contaminant because it resembles diphtheroids. Diphtheroids isolated from CSF and blood should be routinely tested for motility at 25 ° and 37°C. Isolates that are motile at room temperature and that grow as typically small, clear{J-hemolytic colonies on sheep blood agar may be presumptively identified as L. monocytogenes. Corynebacterium aquaticum is a motile diphtheroid, but its yellow colony morphology will distinguish it from L. monocytogenes. Colonies of L. monocytogenes on sheep blood agar may also resemble group B streptococci. Confusion may occur because both are hippurate-positive, and L. monocytogenes may appear initially as gram-positive cocci in young cultures before assuming their characteristic rod shape.
Questions & Answers Q. How can gram-negative cocci (Neisseria and Branhamella) be differentiated
morphologically from gram-negative coccoid rods (Moraxella and Acinetobacter)?
A. A very simple test to differentiate cocci from coccobacilli has been described byCatIin (J. Clin. Microbiol.l:102, 1975). A disc diffusion antibiotic susceptibility plate may be used; if a susceptibility has not been performed, streak the organism on a sheep blood or chocolate agar plate, and place 100unit penicillin discs on the plate in both the heavy and light areas of inoculation. Mter overnight
6
incubation, some of the growth from the edge of the wne of inhibition around the penicillin disc is removed and suspended in a drop of saline on a slide. A #1 coverslip is applied and the preparation is observed under the oil immersion objective with reduced light. Neisseria and Branhamella will appear as cocci although they may be enlarged. Coccobacilli (Moraxella and Acinetobactcr, etc.) will appear as rods and long f1laments. The growth may also be examined after staining with crystal violet, but use of the Gram's stain may distort the organisms.
Occasionally, L. monocytogenes is0lates have been confused with enteroco. because the colonies are similar, and bo organisms give a positive bile-escuIin te A slide catalase test will readily differen tiate catalase-positive Listeria from cat, lase-negative streptococci. This patient with sepsis and meningit caused by two different organisms in th neonatal period was most unusual and I presented the simultaneous occurrence ( two classic neonatal infections in the sal infant. Neonatal L. monocytogenes infl tions, when acquired at the time of birtl usually become clinically manifest 1- 4 weeks postpartum as meninigitis. It seemed more probable that this child h, an immunologic defect. Her 18-monthold sibling subsequently developed a rapidly fatal necrotizing enterocolitis wi Candida sepsis and Candida meningitis This unlikely sequence of events no dOll reflects an underlying immunologic defl that has not yet been dermed in this fan ily. In the clinical microbiology laboratory, there is a need to be alert for secor organisms in otherwise seriously ill or ir munocompromised patients.