ABSTRACT
OBJECTIVE: To study the clinical significance of virulence genes exo U and exo S of type III secretion system (TTSS) of Pseudomonas aeruginosa (PA). METHODS: One hundred and eighty-nine clinical isolates of PA were collected from five hospitals. The incidence of virulence genes exo U and exo S in PA were determined with PCR. Minimum inhibitory concentration of anti-bacterial drug for PA was determined with microdilution method. The clinical features and outcomes of 60 hospitalized patients colonized or infected with exo U+/exo S- positive or exo U-/exo S+ positive PA isolated from sputum were analyzed retrospectively. Data were processed with chi-square test. RESULTS: Among the 189 PA isolates, 85.2% (161/189) harbored TTSS genes, including exo U-/exo S+ type (120 isolates), exo U+/exo S- type (31 isolates), exo U-/exo S- type (7 isolates), and exo U+/exo S+ type (3 isolates). 72.0% (72/100) isolates from sputum and 81.5% (44/54) isolates from blood belonged to exo U-/exo S+ genotype. Compared with those of TTSS-negative isolates, the antimicrobial resistance of TTSS-positive isolates to cefoperazone/sulbactam, ceftazidime, amikacin, and cefepime were lower (with χ² value respectively 10.1, 16.1, 9.3, 33.8, P values all below 0.01). The antimicrobial resistance to all examined drug between exo U-/exo S+ type and exo U+/exo S- type isolates was close (with χ² values from 0.08 to 2.04, P values all above 0.05). Patients detected with exo U+/exo S- positive PA isolated from sputum were significantly associated with PA infection, and they usually had history of tracheal intubation, ICU hospitalization, and combined use of drugs for anti-infection treatment. Patients detected with exo U-/exo S+ positive PA isolated from sputum were significantly associated with PA colonization, which had basic lung disease and better outcome than the former infection type. CONCLUSIONS: The TTSS exists in most clinical isolates of PA. Detection of exo U or exo S of PA isolated from sputum is helpful for the analysis of clinical features and outcome of patients.
Subject(s)
Bacterial Secretion Systems/genetics , Pseudomonas Infections/microbiology , Pseudomonas aeruginosa/genetics , Pseudomonas aeruginosa/pathogenicity , ADP Ribose Transferases/genetics , ADP Ribose Transferases/metabolism , Bacterial Proteins/genetics , Bacterial Proteins/metabolism , Bacterial Toxins/genetics , Bacterial Toxins/metabolism , Drug Resistance, Bacterial , Genes, Bacterial , Humans , Microbial Sensitivity Tests , Pseudomonas aeruginosa/isolation & purification , Retrospective Studies , VirulenceABSTRACT
OBJECTIVE: To evaluate the in vitro antimicrobial activity of piperacillin-sulbactam against clinical isolates of non-fermentative bacilli isolated from common infections. METHODS: Microdilution was employed to study the antimicrobial resistance. RESULTS: A total of 770 strains were collected from 6 hospitals in Guangzhou, including Pseudomonas aeruginosa, Acinetobacter baumannii, Stenotrophomonas maltophilia, Burkholderia cepacia, Flavobacterium, and Alcaligenes. Compared with other ß-lactams, piperacillin-sulbactam displayed the highest activity against all the isolates of P.aeruginosa, especially for imipenem non-sensitive isolates, with the susceptibility of 71.9% and 55.8%, respectively. Piperacillin-sulbactam and cefoperazone-sulbactam kept good activity against imipenem sensitive isolates of A.baumannii, with the susceptibility of 71.0% and 73.0%, respectively. For the strains of Burkholderia cepacia, 69% strains exhibited minimal inhibitory concentration (MIC) of ≤ 16 mg/L for piperacillin-sulbactam. For the strains of Flavobacterium, and Alcaligenes, piperacillin-sulbactam also had excellent activity, with the susceptibility of 70.2% and 94.4%, respectively. CONCLUSION: Piperacillin-sulbactam exhibits good activity again non-fermentative bacilli, especially for imipenem non-sensitive isolates of P.aeruginosa.
