Production of a plasmid-encoded OXA-72 β-lactamase associated with resistance to carbapenems in a clinical isolate Acinetobacter junii

Acinetobacter baumannii infections in Amazon Region driven by extensively drug resistant international clones, 2016-2018

BACKGROUND

Acinetobacter baumannii is a leading cause of nosocomial infections. This species is characterised by the presence of pandemic lineages (International Clones) that present a broad antimicrobial resistance profile.

OBJECTIVE

To perform the molecular epidemiology of carbapenem-resistant A. baumannii from a clinical setting in the Amazon Basin, and to characterise their antimicrobial resistance determinants.

METHODS

The genetic relationship of carbapenem-resistant A. baumannii were assessed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Class A, B and D β-lactamase genes were screened by polymerase chain reaction (PCR) and sequencing. The antimicrobial susceptibility profile was obtained by Disc-diffusion method and minimum inhibitory concentration (MIC) determination.

FINDINGS

All carbapenem-resistant A. baumannii strains belonged to three international clones, IC-1, IC-5 and IC-6, the latter recently reported by the first time in Brazil. The major determinant of carbapenem resistance in IC-1 and IC-5 strains was bla_OXA-23, associated with ISAba1 and ISAba3, respectively, while IC-6 harboured the bla_OXA-72.

CONCLUSIONS

The A. baumannii epidemiology in Brazilian Amazon Region was unknown. It was demonstrated that A. baumannii XDR international clones were responsible for nosocomial infections in Boa Vista during 2016-2018, revealing that the epidemiological scenario of A. baumannii infections in Amazon Region resembles those from the cosmopolitan regions worldwide.

Evaluation of Combined Use of Temocillin Disk and Mastdisks Inhibitor Combination Set Against Polymerase Chain Reaction for Detection of Carbapenem-Resistant Enterobacteriaceae

AIM:

To evaluate the diagnostic performance of MDI and temocillin disk (30 μg) for detection of carbapenem-resistant Enterobacteriaceae in comparison to real-time PCR.

MATERIAL AND METHODS:

Fifty specimens submitted to the Microbiology Laboratory of Ain Shams University Hospitals and showed resistance to carbapenem drugs through routine culture and susceptibility testing, were assessed by both temocillin disk (30 μg) and MDI set to detect carbapenem-resistant Enterobacteriaceae. Results were compared to real-time PCR for detection of carbapenemase genes blaKPC, blaNDM, blaOXA–48-like, blaVIM, and blaIMP.

RESULTS:

Our work revealed that most of the CPE isolates were Klebsiella species (62%) followed by E. coli (24%), Serratia (10%) and Citrobacter (4%). Phenotypic detection of carbapenem-resistant classes revealed OXA - 48 in 96% of isolates, followed by MBLs (82%), and KPC (34%). All isolates were negative for AmpC. Detection of the genes by real-time PCR showed that the predominance was for the blaOXA-48 gene (96%) then blaVIM (94%) followed by blaNDM (54%), blaKPC (46%) and finally blaIMP (40%). Evaluation of the MDI set against PCR showed sensitivity (82.1%) and specificity (70%). The temocillin disk had 97.9% sensitivity and 50% specificity. The evaluation of Temocillin disk and MDI in combination for detection of carbapenem-resistant Enterobacteriaceae showed 99.7% sensitivity and 35% specificity.

CONCLUSION:

Adding Temocillin disk to Mastdisks ID inhibitor combination set provides a simple, easy, rapid and highly sensitive test that can be used for screening and classification of carbapenem-resistant Enterobacteriaceae. However, it still needs confirmation by molecular techniques.

Carbapenem-resistant Acinetobacter pittii strain harboring blaOXA-72 from Brazil

In this study, we report the isolation of OXA-72-producing Acinetobacter pittii in Brazil. A carbapenem-resistant A. pittii strain was recovered from a hospitalized female patient from Espírito Santo, Southeastern Brazil. PCR screening and DNA sequencing allowed us to identify the presence of bla_OXA-72. We observed bla_OXA-72 in a ~11kb plasmid and flanked by XerC/XerD-binding sites.

Antimicrobial susceptibility testing in predicting the presence of carbapenemase genes in Enterobacteriaceae in South Africa

BACKGROUND

Carbapenem-resistant Enterobacteriaceae (CRE) is a concern in South Africa and worldwide. It is therefore important that these organisms be accurately identified for infection prevention control purposes.

METHOD

In this study 1193 suspected CREs from 46 laboratories from seven provinces in South Africa were assessed to confirm the prevalence of carbapenemase genes from our referral diagnostic isolates for the period 2012 to 2015. We compared the antimicrobial susceptibility testing method used in the reference laboratory to the polymerase chain reaction (PCR) which is used as the gold standard. Organism identification and antimicrobial susceptibility testing were performed using automated systems and DNA was extracted using a crude boiling method. The presence of carbapenemase-producing genes (bla _NDM, bla _KPC, bla _OXA-48&variants_, bla _GES, bla _IMP and bla _VIM) was screened for using a multiplex real-time PCR.

RESULTS

Sixty-eight percent (n = 812) of the isolates harboured a carbapenemase-producing gene; the three most common genes included: bla _NDM, bla _OXA-48&variants and bla _VIM. Majority of the carbapenemase producing Enterobacteriaceae (CPE) isolates were Klebsiella species (71 %). The Microscan® Walkaway system used for the screening of carbapenemase production was 98 % sensitive with a minimal inhibitory concentration (MIC) breakpoint of less than 0.5 as susceptible for ertapenem and a low specificity (13 %).

CONCLUSION

From this study we can conclude that carbapenemase-producing Enterobacteriaceae is increasing in South Africa and the use of phenotypic methods for detection of CPEs showed good sensitivity but lacked specificity.

First report of Oxa-72-producing Acinetobacter calcoaceticus in Lebanon

Emergence of carbapenem-resistant Acinetobacter spp. has been increasingly reported worldwide. We report here the first detection of an Acinetobacter calcoaceticus isolate from vegetables in Lebanon carrying the bla Oxa-72 gene. These findings show that the Lebanese environment may constitute a potential reservoir for this antibiotic resistance gene.

The Molecular Epidemiology and Genetic Environment of Carbapenemases Detected in Africa

Research articles describing carbapenemases and their genetic environments in Gram-negative bacteria were reviewed to determine the molecular epidemiology of carbapenemases in Africa. The emergence of resistance to the carbapenems, the last resort antibiotic for difficult to treat bacterial infections, affords clinicians few therapeutic options, with a resulting increase in morbidities, mortalities, and healthcare costs. However, the molecular epidemiology of carbapenemases throughout Africa is less described. Research articles and conference proceedings describing the genetic environment and molecular epidemiology of carbapenemases in Africa were retrieved from Google Scholar, Scifinder, Pubmed, Web of Science, and Science Direct databases. Predominant carbapenemase genes so far described in Africa include the blaOXA-48 type, blaIMP, blaVIM, and blaNDM in Acinetobacter baumannii, Klebsiella pneumoniae, Enterobacter cloacae, Citrobacter spp., and Escherichia coli carried on various plasmid types and sizes, transposons, and integrons. Class D and class B carbapenemases, mainly prevalent in A. baumannii, K. pneumoniae, E. cloacae, Citrobacter spp., and E. coli were the commonest carbapenemases. Carbapenemases are mainly reported in North and South Africa as under-resourced laboratories, lack of awareness and funding preclude the detection and reporting of carbapenemase-mediated resistance. Consequently, the true molecular epidemiology of carbapenemases and their genetic environment in Africa is still unknown.

OXA-207, a novel OXA-24 variant with reduced catalytic efficiency against carbapenems in Acinetobacter pittii from Spain

A carbapenem-resistant Acinetobacter pittii strain carrying an OXA-24-like enzyme was isolated in northern Spain in 2008. Sequence analysis confirmed the presence of the novel bla(OXA-207) gene flanked by the site-specific XerC/XerD-like recombination binding sites and showing a unique Gly222Val substitution compared to OXA-24. Cloning and kinetic analysis showed that OXA-207 presents a reduction in the catalytic efficiency against carbapenems and a noticeable increase for oxacillin.