Cavitated pulmonary nodules in a female patient with breast cancer: Keep in mind Serratia marcescens' infections

A preliminary exploration on the mechanism of the carbapenem-resistance transformation of Serratia marcescens in vivo

BACKGROUND

The infection of carbapenem-resistant organisms was a huge threat to human health due to their global spread. Dealing with a carbapenem-resistant Serratia marcescens (CRSM) infection poses a significant challenge in clinical settings. This study aims to provide insights into strategies for controlling CRSM infection by exploring the transformation mechanism of carbapenem-resistance.

METHODS

We used whole genome sequencing (WGS) to investigate the mechanism of carbapenem resistance in 14 S. marcescens isolates in vivo. The expression level of related genes and the minimum inhibitory concentration of meropenem (MICMEM) were also evaluated to confirm the mechanism of carbapenem resistance.

RESULTS

Seven groups of S. marcescens, each consisting of two strains, were collected from a hospital and displayed a shift in MICMEM from low to high levels. Homology analysis revealed that the isolates in five groups were significantly different from the remaining two. WGS and experimental evidence indicated that four groups of strains developed carbapenem resistance by acquiring the blaKPC (obtaining group), while two groups (persisting group) increased the expression level of the blaKPC. In contrast, isolates in the last group (missing group) did not carry the blaKPC. All strains possessed multiple β-lactamase genes, including blaCTX-M-14, blaSRT-1, and blaSRT-2. However, only in the missing group, the carbapenem-resistant strain lost an outer membrane protein-encoding gene, leading to increased blaCTX-M-14 expression compared to the carbapenem-susceptible strain.

CONCLUSION

The study findings suggest that S. marcescens strains developed diverse carbapenem resistance in vivo through the evolution of drug resistance, rather than through clone replacement. We hypothesize that carbapenem resistance in S. marcescens was due to certain clonal types with a distinct mechanism.

Clinicopathologic Features and Pathogens of Granulomatous Lobular Mastitis

BACKGROUND

Granulomatous lobular mastitis (GLM) is a rare, benign, and complex breast disease that can be easily misdiagnosed as breast cancer. The etiology of GLM is unclear, and optimal treatment has not been established.

METHODS

Medical records for 333 patients with GLM in recent 5 years at Longhua Hospital, Shanghai, China, were analyzed. Potential pathogens in 33 fresh tissue specimens were also analyzed using 16S rDNA sequencing technology, matrix-assisted laser desorption ionization time of flight mass spectrometry, and bacterial cultures.

RESULTS

The median age of patients was 32 years (range 22-47 years). Among 333 patients, 38.7% displayed elevated prolactin, while 23.7% displayed high interleukin-2. In the granulomatous lesion, CD3-positive T lymphocytes were significantly more than CD20-positive B lymphocytes around the vacuoles or microabscesses. Gram-positive organisms were observed in 82 cases, including in 22 cases from fresh tissue specimens. Thirty-three cases yielded associated pathogens and all displayed multiple pathogenic infections, as identified using 16S rDNA sequencing technology. Pathogenic infections were further identified as belonging to 16 main genera and 8 main pathogenic species.

CONCLUSIONS

GLM displays distinct histological and clinical features similar to those that have been previously reported in the literature. Using 16S rDNA sequencing technology, all of our cases demonstrated multiple pathogenic infections, which provided more useful information for clinical treatment.