Monitoring F1651 P-like fimbria expression at the single-cell level reveals a highly heterogeneous phenotype

Spatially localised expression of the glutamate decarboxylase gadB in Escherichia coli O157:H7 microcolonies in hydrogel matrices

Functional diversity within isogenic spatially organised bacterial populations has been shown to trigger emergent community properties such as stress tolerance. Considering gadB gene encoding a key glutamate decarboxylase involved in E. coli tolerance to acidic conditions, we investigated its expression in hydrogels mimicking the texture of some structured food matrices (such as minced meat or soft cheese). Taking advantage of confocal laser scanning microscopy combined with a genetically-engineered dual fluorescent reporter system, it was possible to visualise the spatial patterns of bacterial gene expression from in-gel microcolonies. In E. coli O157:H7 microcolonies, gadB showed radically different expression patterns between neutral (pH 7) or acidic (pH 5) hydrogels. Differential spatial expression was determined in acidic hydrogels with a strong expression of gadB at the microcolony periphery. Strikingly, very similar spatial patterns of gadB expression were further observed for E. coli O157:H7 grown in the presence of L. lactis. Considering the ingestion of contaminated foodstuff, survival of E. coli O157:H7 to acidic stomachal stress (pH 2) was significantly increased for bacterial cells grown in microcolonies in acidic hydrogels compared to planktonic cells. These findings have significant implications for risk assessment and public health as they highlight inherent differences in bacterial physiology and virulence between liquid and structured food products. The contrasting characteristics observed underscore the need to consider the distinct challenges posed by these food types, thereby emphasising the importance of tailored risk mitigation strategies.

Febrile urinary tract infections: pyelonephritis and urosepsis

PURPOSE OF REVIEW

Complicated infections of the urinary tract (UTI) including pyelonephritis and urosepsis are also called febrile UTI. This review describes insights from the literature on this topic since July 2014.

RECENT FINDINGS

Recent studies regarding risk factors and consequences of febrile UTI confirmed existing knowledge. It remains difficult to obtain insight into the epidemiology of febrile UTI because urine and blood cultures are frequently missing. The relationship between host and virulence factors of Escherichia coli was further explored showing that less virulent strains can cause infection in immunocompromised patients. In contrast to obstructive uropathy, diabetes, and being older, neutropenia was not a risk factor for lower UTI or urosepsis. A randomized controlled trial revealed that ceftolozane-tazobactam was marginally superior to levofloxacin as treatment for complicated UTI. Case series supported the notion that xanthogranulomatous and emphysematous pyelonephritis are more common in diabetic patients and that drainage or surgery is often required.

SUMMARY

Neutropenia was not a risk factor for lower UTI or urosepsis. When local resistance percentages to the frequently prescribed fluoroquinolones are high, the combination of ceftolozane-tazobactam may be an alternative as treatment for complicated UTI. Xanthogranulomatous and emphysematous pyelonephritis need to be considered in diabetic patients presenting with UTI symptoms.