Background: Iron ions affect the expression of outer membrane protein A (OmpA), a major pathogenic protein in Acinetobacter baumannii.Objective: To analyze the effect of iron ions on the expression of the OmpA protein of A. baumannii and explore its association with the virulence of OmpA.Methods: Site-directed mutagenesis was used to construct ompA gene deletion strains and gene repair strains. The OmpA protein expression of A. baumannii under culture with different contents of iron ions was detected. The virulence of A. baumannii with different OmpA protein expression levels were evaluated in macrophages and mice.Results: OmpA protein levels of the three strains were enhanced under iron-rich conditions. They were reduced in the presence of the iron-chelating agent 2,2′-bipyridine. A. baumannii wild type and + ompA had a remarkable toxic effect on RAW246.7 macrophages (P < 0.05). In contrast, the ΔompA had a significantly reduced toxic effect on RAW246.7 macrophages (P < 0.05). The levels of the inflammatory factors IL-1β, IL-6, IL-8, and TNFα in the mice spleen were significantly increased in the + ompA strain treatment group compared with the ΔompA strain group (all P < 0.05). In addition, the levels were higher in the presence of iron ions than in the presence of the chelating agent.Conclusion: Iron-rich conditions increase the OmpA protein expression of A. baumannii. Strains with high OmpA protein expression were more invasive, which may be a key determinant of A. baumannii infection and pathogenicity. Iron control strategies might be used for the management of A. baumannii.

Headings Background : This is a case of a human disseminated nocardiosis caused by Nocardia vulneris which made the patient presenting with fever, cough, shortness of breath, muscle pain and multiple tubercle. Methods: Bacterial culture the blood, sputum, lung rinses and scalp pus samples of the patient, Nocardia vulneris was isolated and identified using the 16s ribosomal RNA gene sequence sequence data. and determine the sensitivity of the isolated bacteria to antibiotics and analysis of the strain's antibiotic treatment. Results: The isolated was identified as Nocardia brasiliensis, which was resistant to ciprofloxacin, but susceptible to amikacin, gentamicin, tobramycin, linezolid, trimethoprim-sulfamethoxazole, amoxicillin/clavulanic, moxifloxacin, ceftriaxone, cefotaxim, imipenem. The patient recovered and his condition remained stable by combinations with linezolid, amikacin and trimethoprim-sulfamethoxazole. Conclusions: This is the first case report of disseminated nocardiosis caused by Nocardia vulneris, and the current case was treated successfully with linezolid, amikacin and trimethoprim-sulfamethoxazole. Clinicians should be aware of its diagnostic, and the MIC value of the drug sensitivity test should be concerned when there is a wide choice of medicines, for the disseminated cases which are diagnosed definitely should be treated with at least 12 months of antimicrobial therapy, bacteriological examination and antimicrobial susceptibility testing should be performed repeatedly.

TLR4 is a key sensor of Gram negative bacteria and LPS. The Asp299Gly (D299G) and Thr399Ile (T399I) SNPs of TLR4 have been associated with increased risks or severity of certain bacterial infections and Gram negative sepsis. This study employed transfection-based complementation of TLR4-negative HEK293T cells to elucidate the role of TLR4 SNPs in sensing Gram-negative bacteria and LPS, and to determine their effect on LPS-elicited activation of MyD88- and TRIF-dependent signaling pathways. Overexpression of wild-type YFP-TLR4 led to marked activation of the NF-κB-dependent pELAM-luciferase reporter in HEK293/CD14/MD2 transfectants exposed to heat-killed E. coli, R. akari and LPS, whereas the D299G (but not T399I) TLR4 exhibited signaling deficiency. Likewise, LPS-mediated activation of TRIF-dependent pRANTES-luciferase and p125 (IFN-beta)-luciferase reporters was significantly lower in HEK293/CD14/MD-2 cells expressing D299G YFP-TLR4. Immunoprecipitation and immunoblot analyses revealed similar total expression levels of wild-type and mutant YFP-TLR4 proteins, and similar LPS binding was observed in HEK293/CD14/MD-2 cells expressing WT or mutant TLR4 species, as detected by FACS. Our data indicate that the D299G SNP impairs TLR4-elicited activation of MyD88- and TRIF-dependent signaling pathways in response to heat-inactivated Gram negative bacteria and LPS not due to lower expression levels of mutant TLR4 or impaired LPS recognition by D299G TLR4/MD2/CD14 complexes.