Detection of Meningococcal Antigen by Latex Agglutination

Abstract

Meningococcal meningitis and septicemia are serious infections with significant morbidity and mortality. A sensitive affordable test is required to provide evidence of meningococcal disease at the earliest opportunity to improve local management and give early warning of potential outbreaks of disease. Culture of organisms is considered the gold standard for diagnosis but is slow (24 h or more) and increasingly influenced by prior antibiotic treatment. Recently, the development of polymerase chain reaction (PCR) has improved diagnosis but this sensitive assay is costly, is not available at most primary care institutions and is not feasible for developing countries. Conventional latex agglutination (LA) enables rapid detection of bacterial antigen in cerebrospinal fluid (CSF) (1,2) and can also be used to test specimens of blood (3,4) or urine (5) and for serogroup determinations on primary cultures (6,7). We discuss here test-card agglutination and also describe a new technique based upon LA in an ultrasonic standing wave that retains the speed of direct antigen testing while significantly increasing sensitivity.

Use of Robotized DNA Isolation and Real-Time PCR To Quantify and Identify Close Correlation between Levels of Neisseria meningitidis DNA and Lipopolysaccharides in Plasma and Cerebrospinal Fluid from Patients with Systemic Meningococcal Disease

“…Before the development of PCR techniques, microbiological diagnosis of meningococcal infections relied on the cultivation or visualization of N. meningitidis from usually sterile body sites (blood, CSF, or petechiae), detection of capsular polysaccharide in CSF, or significant antibody responses several weeks after the acute infection (15,19,25,29). Quantitative blood culture of meningococci is a cumbersome technique, and few such studies have been published over the years (8,21,30,35).…”

Diagnosis of bacterial infection

“…A drawback of many antigen tests is reduced sensitivity compared with culture, and in severe or life-threatening illness this cannot reliably exclude infection. An example is bacterial meningitis, where a positive meningococcal [15] or pneumococcal antigen [16] test on cerebrospinal fluid is excellent at confirming those infections, but a negative test is insufficient for discontinuing empiric therapy. Another drawback of antigen tests is their inability to provide antimicrobial susceptibility data; therefore, even if pneumococcal meningitis is diagnosed on the basis of an antigen test, ceftriaxone will have to be continued until minimum inhibitory concentrations of penicillin can be determined from a cultured isolate.…”

Latex agglutination for bacterial antigens and meningococcus PCR: two useful tools in legal sudden deaths

“…In clinical microbiology, LA tests are used as a screening method and are not intended as a substitute for bacterial culture. Since the published values for the sensitivity of commercial LA kits vary considerably [12], a confirmatory diagnosis of an infection, using culture procedures, is always needed. Nevertheless, a higher concentration of antigens in the blood of individuals with septic shock and fatal outcome has been put forward [3,[12][13][14].…”

“…Since the published values for the sensitivity of commercial LA kits vary considerably [12], a confirmatory diagnosis of an infection, using culture procedures, is always needed. Nevertheless, a higher concentration of antigens in the blood of individuals with septic shock and fatal outcome has been put forward [3,[12][13][14]. In addition, it has been demonstrated recently using quantitative polymerase chain reaction (PCR) that a high copy number of N. meningitidis in whole blood predicts severe complications and death in meningococcal disease [15].…”