Klebsiella pneumoniae, magA, rpmA, wzcK1 and wzcK2 genes - Molecular diagnosis (PCR).
Since 1981, a clinical syndrome that began in Southeast Asia (Taiwan and elsewhere in the region such as Korea, Singapore, Japan, India and Thailand) caused by Klebsiella pneumoniae, characterized by bacteremia and liver abscess primary (PLA known: Primary Liver Abscess) with high mortality (10-40%), followed in some cases of meningitis and endophthalmitis. In other cases , it manifests lung abscess, brain abscess, prostatic abscess, osteomyelitis, septic arthritis or psoas abscess. This infection is acquired in the community and usually immunocompetent patients, without having intestinal problems or underlying hepatobiliary, except for diabetes mellitus found in half of the cases.
The invasive capacity of some strains of Klebsiella pneumoniae appears to be related to a "viscosity" very evident colonies plated out , known as "hipermucoviscoso" phenotype, characterized by the formation of mucoviscosos yarns more than 5 mm when colonies are touched with bacteriological loop. These strains form a capsular mucopolysaccharide, show high resistance to serum lysis, increased resistance to phagocytosis, and are more virulent in mice. The inoculated mice develop liver and brain abscesses, similar to those observed in human infections. This phenotype was found hipermucoviscoso preferably related to the serotype K1, and to a lesser extent with serotype K2. Initially it was thought that the property of hipermucoviscosidad was related to the presence maga gene (mucoviscosity-associated gene A), and the regulatory gene MRPY (regulator of mucoid phenotype A), a plasmid regulatory gene described in 1989, involved in the synthesis extracapsular polysaccharide. Maga gene, described in invasive strains causing complicated primary liver abscess and meningitis endophthalmitis, and would encode a protein of outer membrane involved in the production of the exopolysaccharide. The operon containing maga was responsible for the capsular serotype K1, and mutations maga gene, or any of the other three adjacent genes result in loss of the K1 capsule. However, some authors have found that relation between the presence maga gene and characteristic of hipermucoviscosas strains. Klebsiella pneumoniae -negative mutants lost their exopolysaccharide Maga and became sensitive to serum lysis and phagocytosis.
Maga gene is restricted because Klebsiella pneumoniae capsular phenotype K1, and the operon containing maga was responsible for the serotype K1. What seems clear is currently the maga gene, when present, is only found in strains of capsular serotype K1 (approximately 86% of strains with serotype K1, would maga +). By contrast, other capsulated strains, as serotype K2 lack maga gene but have regulatory gene plasmid MRPY.
Klebsiella pneumoniae capsule, depend on a set of genes (cps), and this assembly would maga gene allele serotype K1 gene capsular serotype K1 wzy polymerase (wzy, kpk1). Serotype strains K2 gene would capsular serotype K2 polymerase (wzy, kpk2). In addition, the hypervirulent strains would be resistant to phagocytosis, would be lethal when inoculasen mouse, and resist in tests death caused by serum, would the gene encoding the uptake system corresponding iron aerobactin siderophore (KFU gene), and the gene associated with metabolism of allantoin (alls gene). All strains of serotype K1 would maga +, + and alls KFU +. K2 and K1 strains, avirulent hipermucoviscosoide not have the character that would lack the plasmid regulatory gene or RMPA aerobactin gene (KFU). However, the strains K2 would maga -, MRPY +, aerobactin +. Acapsuladas K1 strains exist that would K1, maga +, MRPY +, Aerobactin +.
There capsular serotype specific alleles at loci wzy wzx and. The set (cluster) of capsular genes (cps) has an organization preserved with 2 separated by a transcriptional attenuator regions. 3'es specific serotype region and encodes the enzymes for Wzy-dependent biosynthetic system, including the enzymes synthesizing glycosidic precursors, glycosyltransferases, and the two inner membrane proteins and Wzx -Wzy. The Wzy polymerase binds to the lipid carrier polymers of the cytoplasmic membrane of bacteria, undecaprenilfosfato using lipid repeating units exported by the flippase encoded by the wzx gene. Maga gene, wzy K1 correspond to allele (wzy_K1, ie, the polymerase gene of the capsular serotype component K1). Gene sets other serotypes have different alleles at loci wzy (polymerase capsular component) and wzx (flippase, the transport system in the cytoplasmic membrane).
Tests in IVAMI:
- Detection of gene mage (wzy_K1), by PCR amplification.
- MRPY gene detection by PCR amplification.
- KFU gene detection (aerobactin siderophore iron chelator) and / or alls (allantoin) gene.
- dentification serotype K1 and / or K2 for PCR amplification of the wzy-K1 and / or K2 wzy-genes.
- Klebsiella pneumoniae cultivation hipermucoso phenotype.
Preservation and shipment of sample:
Refrigerated (preferred) for less than 2 days.
- Molecular targets for PCR: 48 to 72 hours.
Cost of the test: