Clinical severity of Mycoplasma pneumoniae (MP) infection is associated with bacterial load in oropharyngeal secretions but not with MP genotype.

BACKGROUND: Disease severity in Mycoplasma pneumoniae (MP) infection could potentially be related to bacterial factors such as MP genotype (MP1 or MP2; distinguished by different adhesions proteins) or bacterial load in airway secretions. We have compared these parameters in patients who were hospitalized for MP pneumonia, with outpatients with mild MP disease. METHODS: MP bacterial load was measured by real-time PCR in 45 in- and outpatients ("clinical study group") in whom MP DNA had been detected in oropharyngeal secretions by PCR. In addition, genotype and phylogenetic relationships were determined. The phylogenetical assessment was done by partial DNA sequencing of the P1 gene on isolates from 33 patients in the clinical study-group where sufficient DNA was available. The assessment was further extended to isolates from 13 MP-positive family members and 37 unselected MP positive patients from the two subsequent years and two different geographical locations. In total 83 strains were molecular characterized. RESULTS: Mean MP loads were significantly higher in 24 hospitalized patients than in 21 outpatients (1600 vs. 170 genomic equivalents/microL, p = 0.009). This difference remained significant after adjustment for age and days between disease onset and sampling. Hospitalized patients also had higher C-reactive protein levels. Mean levels were 188 vs 20 mg/L (p = 0,001). The genotype assessment showed MP genotype 1 in 17 of the 33 sequenced strains from the clinical study-group, and type 2 in 16 of these patients. Within each genotype, sequence differences were minimal. No association between disease severity and MP genotype was observed. In the extended genotype assessment, MP1 was found in similar proportions. In family contacts it was found in 53% and among patients from the two subsequent years 53% and 40%. CONCLUSIONS: A higher MP bacterial load in throat secretions at diagnosis was associated with more advanced respiratory disease in patients, but MP genotype did not influence disease severity. Both MP genotypes co-circulated during recent outbreaks in Sweden

Multi-locus sequence analysis (MLSA) of clinical "CandidatusNeoehrlichia mikurensis" strains from Europe.

CandidatusNeoehrlichia mikurensis is the tick-borne agent of neoehrlichiosis, an infectious disease that primarily affects immunocompromised patients. So far, the genetic variability of Neoehrlichia has been studied only by comparing 16S rRNA gene and groEL operon sequences. We describe the development and use of a multi-locus sequence analysis (MLSA) protocol to characterize the genetic diversity of clinicalNeoehrlichiastrains in Europe and their relatedness to other species within the Anaplasmataceae family.Six genes were selected:ftsZ, clpB, gatB,lipA,groEL and 16SrRNA. Each MLSA locus was amplified by real-time PCR, and the PCR-products sequenced. Phylogenetic trees of MLSA locus relatedness were constructed from aligned sequences. Blood samples from 12 patients with confirmed Neoehrlichia infection from Sweden (n = 9), the Czech Republic (n = 2) and Germany (n = 1) were analyzed with the MLSA protocol.Threeof the Swedish strains exhibited identical lipA sequences, while the lipA sequences of the strains from the other nine patients were identical to each other.One of the Czech strains had one differing nucleotide in the clpB sequence from the sequences of the other 11 strains. All 12 strains had identical sequences for the genes 16SrRNA,ftsZ, gatB, and groEL.According to the MLSA, Neoehrlichia is most closely related to E. ruminantium, less so to A. phagocytophilum and least to Wolbachiaendosymbiont, among the Anaplasmataceae.To conclude, three sequence types of infectious Neoehrlichia wereidentified: one in the west of Sweden, one in the Czech Republic, and one spread throughout Europe