Prevalence of carbapenemases among high-level aminoglycoside-resistant Acinetobacter baumannii isolates in a university hospital in China

Abstract

The prevalence of aminoglycoside resistant enzymes has previously been reported and extended-spectrum β-lactamase among Acinetobacter baumannii. To track the risk of multidrug-resistant A. baumannii, the present study aimed to determine the prevalence of carbapenemases in high-level aminoglycoside resistant A. baumannii over two years. A total of 118 strains of A. baumannii were consecutively collected in the First Affiliated Hospital of Chengdu Medical College, Chengdu, China. These isolates were investigated on the genetic basis of their resistance to aminoglycosides. The results showed that 75 (63.56%) isolates were high-level resistant to aminoglycosides, including gentamicin and amikacin (minimum inhibitory concentration, ≥256 µg/ml). Aminoglycoside-resistant genes ant(2″)-Ia, aac(6′)-Ib, aph(3′)-Ia, aac(3)-Ia, aac(3)-IIa, armA, rmtA, rmtB, rmtC, rmtD, rmtE, rmtF, rmtG, rmtH and npmA, and carbapenem-resistant genes blaOXA-23, blaOXA-24, blaOXA-51, blaOXA-58, blaSIM, blaIMP, blaNDM-1 and blaKPC, were analyzed using polymerase chain reaction. The positive rate of ant(2″)-Ia, aac(6′)-Ib, aph(3′)-Ia, aac(3)-Ia and aac(3)-IIa was 66.95, 69.49, 42.37, 39.83 and 14.41%, respectively. armA was present in 72.0% (54/75) of A. baumannii isolates with high-level resistance to aminoglycosides. The remaining nine 16S ribosomal RNA methlyase genes (rmtA, rmtB, rmtC, rmtD, rmtE, rmtF, rmtG, rmtH and npmA) and aminoglycoside-modifying enzyme gene aac(6′)-Ib-cr were not detected. Among the 54 armA-positive isolates, the prevalence of the carbapenem resistant blaOXA-23 and blaOXA-51 genes was 79.63 and 100%, respectively. armA, ant(2″)-Ia and aac(6′)-Ib were positive in 43 isolates. The results of multilocus sequence typing revealed 31 sequence types (STs) in all clinical strains. Among these STs, the high-level aminoglycoside-resistant A. baumannii ST92, which mostly harbored blaOXA-23, was the predominant clone (29/75). In conclusion, A. baumannii harboring carbapenemases and aminoglycoside-resistant enzymes are extremely prevalent in western China, emphasizing the need to adopt surveillance programs to solve the therapeutic challenges that this presents.

High distribution of 16S rRNA methylase genes rmtB and armA among Enterobacter cloacae strains isolated from an Ahvaz teaching hospital, Iran

“…In this study, we observed that 4 out of 33 strains with HLAR phenotype were lacking the 16S rRNA methylase genes. Similar finding was also reported in a study conducted in China by Wang et al [24] on Acinetobacter baumannii strains. Moreover, they showed that some strains with HLAR phenotype had genes encoding AMEs instead of the 16S rRNA methylase genes.…”

Distribution of virulence-associated genes and antimicrobial susceptibility in clinical Acinetobacter baumannii isolates

“…Our previous surveys revealed that the antibiotic resistance among A. baumannii clinical isolates is very serious. [ 20 , 21 ]. And antimicrobial- resistant A. baumannii has very high potential to spread among ill patients in ICU (intensive care units), so it is crucial to adopt early recognition and timely implementation of appropriate infection control measures in preventing outbreaks.…”

High-Level Aminoglycoside Resistance in Human Clinical Klebsiella pneumoniae Complex Isolates and Characteristics of armA-Carrying IncHI5 Plasmids

“…Ten 16S-RMTase gene-negative strains showing a high MIC (>1,024 mg/L) for kanamycin carried at least one aac(3)-IId or aph(3´)-Ia gene, indicating that aac(3)-IId and aph(3´)-Ia may provide high-level resistance against kanamycin. Similarly, the production of 16S-RMTase or a combination of multiple AMEs was shown to be the major mechanism underlying high-level aminoglycoside-resistant gram-negative bacilli in Chengdu, China, and Brazil ( Wang et al, 2016 ; Ballaben et al, 2018 ).…”