case25.neisseriamenigitis

case25.neisseriamenigitis - Case 25 Lydyard, Peter; Cole,...

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1. What is the causative agent, how does it enter the body and how does it spread a) within the body and b) from person to person? Causative agent The patient has bacteremia (meningococcemia) caused by Neisseria meningitidis (often termed the meningococcus). This bacterium is one of the three principal causes of bacterial meningitis , the other two being Streptococcus pneumoniae (Sp) and Haemophilus influenzae serotype b (Hib). However, the introduction of conjugate vaccines for immunization of infants has reduced invasive disease caused by Sp and Hib significantly. Case 25 Neisseria meningitidis A 19-year-old college student was in his usual state of health until the evening before admission, when he went to bed with a headache. He told his room-mate that he felt feverish, and on the following morning his room-mate found him in bed, moaning and lethargic. He was taken to the emergency room, where he appeared toxic and drowsy but oriented. His temperature was 40 C, his heart rate was 126/min, and his blood pressure was 100/60 mm Hg. His neck was supple. He had an impressive, nonblanching purpuric rash, most prominent on the trunk, wrists, and legs (Figure 1). His white blood cell count was 26 000 m l –1 with 25% band forms. The platelet count was 80 000 m l –1 . Blood cultures were obtained and the patient was started on intravenous ceftriaxone. Blood cultures revealed gram-negative diplococci (Figure 2). It should be noted that in North America this patient would have received a lumbar puncture (LP) as an essential component in the diagnosis of meningococcal disease except where explicitly contraindicated. However, this is not the case in the UK where severe sepsis is a contraindication to lumbar puncture (www.meningitis.org). In the UK many pediatricians and adult physicians feel that LP should not be performed acutely in patients suspected of having meningococcal disease and, if LP is considered to be necessary, it is done once the patient is stable. In the case considered above the cerebrospinal fluid (CSF) glucose, protein, and white blood cell count were normal, and CSF bacterial culture was negative. Figure 1. Legs of patient showing a purpuric rash typical of meningococcal septicemia. Figure 2. Gram stain of N. meningitidis. © Lydyard, Peter; Cole, Michael; Holton, John; Irving, Will; Porakishvili, Nino; Venkatesan, Pradhib; Ward, Kate, Jan 01, 201 Garland Science, Hoboken, ISBN: 9780203856871
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The pathogenic Neisseria species N. meningitidis and N. gonorrhoeae are capnophilic , gram-negative cocci. The cocci are found in pairs where their adjacent sides are flattened giving them a coffee bean appearance (Figure 3). Neisseria species are oxidase-positive (Figure 4), catalase-posi- tive, and produce acid from sugars by oxidation. Their habitat is the mucous membranes of mammals and many species are commensals of these surfaces. However, N. meningitidis is an obligate human pathogen whose principal habitat is the nasopharynx. However, it has been reported
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case25.neisseriamenigitis - Case 25 Lydyard, Peter; Cole,...

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