A survey of five broad-host-range plasmids in gram-negative bacilli isolated from patients

To learn the prevalence of the primary classical broad-host-range (BHR) IncA/C, IncN, IncP, IncQ, and IncW plasmids in dominant gram-negative bacilli from inpatients in a teaching hospital in southern China.

A multiplex polymerase chain reaction based on the replicons of BHR IncA/C, IncN, IncP, IncQ, and IncW plasmids was developed and used to determine these BHR plasmids. The difference in prevalence rates among the different species from three specimens was evaluated by a binary logistic regression model and the differences between multidrug-resistant organisms (MDRO) and non-MDRO were assessed using a chi-square test.

The average positive detection percentages of the replicons were 4.3%, 3.7%, 3.0%, 2.6%, and 1.9%, respectively, for IncN, IncP, IncQ, IncW, and IncA/C in descending order. The distribution of all five BHR plasmids did not differ significantly between specimens collected from wounds and urine, although both were significantly higher than those of sputum. The prevalence rates of all five BHR plasmids in MDROs were significantly higher than those in non-MDRO for Enterobacteriaceae; however, no significant difference was seen in non-fermenting gram-negative bacilli (NFGNB).

BHR IncA/C, IncN, IncP, IncQ, and IncW plasmids, which occur more often in bacilli from wound and urine specimens than those of sputum, are widespread in Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Enterobacter cloacae, Pseudomonas aeruginosa, and Acinetobacter baumannii strains isolated from inpatients. The prevalence rates in MDRO are higher than those in non-MDRO for Enterobacteriaceae but not significantly different for NFGNB.