Comparison of urovirulence factors and genotypes for bacteria causing acute lobar nephronia and acute pyelonephritis

BACKGROUND: Acute lobar nephronia (ALN) is a severe renal parenchymal inflammatory disease that has been diagnosed with increasing frequency as a result of newer noninvasive diagnostic modalities. Escherichia coli is the most common bacterial pathogen isolated from the urine samples of ALN patients. This prospective study was conducted to elucidate and distinguish the bacterial virulence factors associated with ALN and acute pyelonephritis (APN) in pediatric patients. METHODS: Patients included in the present study were those suspected of an upper urinary tract infection who underwent ultrasonographic, computed tomographic and technetium 99m-dimercaptosuccinic acid scintigraphic evaluation to distinguish between ALN and APN. The E. coli isolates from the urine samples of patients were screened with polymerase chain reaction analysis for various urovirulence genes. Pulsed-field gel electrophoresis was used to analyze the genetic association of the isolates. RESULTS: A total of 88 patients were enrolled. Forty-six patients were diagnosed with ALN and 42 with APN. Demographic characteristics and clinical results were similar except for longer fever duration before admission, longer fever continuation following antibiotic treatment and higher C-reactive protein values noted in the ALN group. Diverse genotypes were found among the E. coli isolates in both groups. Among the pathogenetic determinants examined, multivariate logistic regression analysis indicated that a papG II allele was the only significant urovirulence factor associated with ALN (P < 0.005; odds ratio, 17.16). This association was independent of the presence of VUR. CONCLUSIONS: While no specific genetic lineage was identified among the E. coli isolates studied, a papG II gene was found to be strongly associated with the cause of ALN among pediatric patients.