Emergence of NDM-producing non-baumannii Acinetobacter spp. isolated from China

Infections Due to Acinetobacter baumannii-calcoaceticus Complex: Escalation of Antimicrobial Resistance and Evolving Treatment Options

Bacteria within the genus Acinetobacter (principally A. baumannii-calcoaceticus complex [ABC]) are gram-negative coccobacilli that most often cause infections in nosocomial settings. Community-acquired infections are rare, but may occur in patients with comorbidities, advanced age, diabetes mellitus, chronic lung or renal disease, malignancy, or impaired immunity. Most common sites of infections include blood stream, skin/soft-tissue/surgical wounds, ventilator-associated pneumonia, orthopaedic or neurosurgical procedures, and urinary tract. Acinetobacter species are intrinsically resistant to multiple antimicrobials, and have a remarkable ability to acquire new resistance determinants via plasmids, transposons, integrons, and resistance islands. Since the 1990s, antimicrobial resistance (AMR) has escalated dramatically among ABC. Global spread of multidrug-resistant (MDR)-ABC strains reflects dissemination of a few clones between hospitals, geographic regions, and continents; excessive antibiotic use amplifies this spread. Many isolates are resistant to all antimicrobials except colistimethate sodium and tetracyclines (minocycline or tigecycline); some infections are untreatable with existing antimicrobial agents. AMR poses a serious threat to effectively treat or prevent ABC infections. Strategies to curtail environmental colonization with MDR-ABC require aggressive infection-control efforts and cohorting of infected patients. Thoughtful antibiotic strategies are essential to limit the spread of MDR-ABC. Optimal therapy will likely require combination antimicrobial therapy with existing antibiotics as well as development of novel antibiotic classes.

Prevalence, Risk Factors, and Molecular Epidemiology of Intestinal Carbapenem-Resistant Pseudomonas aeruginosa

Pseudomonas aeruginosa may become multidrug-resistant (MDR) due to multiple inherited and acquired resistance mechanisms. The human gastrointestinal tract is known as a reservoir of P. aeruginosa and its resistance genes. In this study, we collected 76 intestinal carbapenem-resistant P. aeruginosa (CRPA) strains from clinical inpatients admitted to our hospital from 2014 to 2019, together with their medical data. We aim to analyze the clinical risk factors associated with CRPA infection and its molecular features. We found that the prevalence of CRPA in P. aeruginosa strains was 41.3% (95% confidence interval [CI], 34.1 to 48.8%). We also identified four variables associated with intestinal CRPA positivity, prior antibiotic exposure to aminoglycosides or carbapenems, underlying diabetes mellitus, and extraintestinal P. aeruginosa isolation. bla_KPC-2 is the only detected carbapenemase gene, accounting for 21.1% of CRPA strains. The genetic environment showed that the bla_KPC-2 gene was flanked immediately by ISKpn8 and ISKpn6 and several other mobile elements further upstream or downstream. Four sequence types (STs) were identified, with ST463 as the dominant sequence type. In conclusion, screening for P. aeruginosa colonization upon hospital admission could reduce the risk of P. aeruginosa infection and spread of CRPA in the hospital.

IMPORTANCEPseudomonas aeruginosa may become multidrug-resistant (MDR) due to multiple inherited and acquired resistance mechanisms. The human gastrointestinal tract is known as a reservoir of P. aeruginosa and its resistance genes. Risk factor analysis and molecular epidemiology are critical for preventing their potential dissemination. Here, we identified four risk factors associated with intestinal CRPA—prior antibiotic exposure to aminoglycosides or carbapenems, underlying diabetes mellitus, and extraintestinal P. aeruginosa isolation. Further, we found similar genetic environments with several mobile elements surrounding the bla_KPC gene, a carbapenemase gene only detected in intestinal CRPA strains in this study. These findings are of significant public health importance, as the information will facilitate the control of the emergence and spread of CRPA.

The Spread of NDM-1 and NDM-7-Producing Klebsiella pneumoniae Is Driven by Multiclonal Expansion of High-Risk Clones in Healthcare Institutions in the State of Pará, Brazilian Amazon Region

Carbapenem resistance among Klebsiella pneumoniae isolates is often related to carbapenemase genes, located in genetic transmissible elements, particularly the blaKPC gene, which variants are spread in several countries. Recently, reports of K. pneumoniae isolates harboring the blaNDM gene have increased dramatically along with the dissemination of epidemic high-risk clones (HRCs). In the present study, we report the multiclonal spread of New Delhi metallo-beta-lactamase (NDM)-producing K. pneumoniae in different healthcare institutions in the state of Pará, Northern Brazil. A total of 23 NDM-producing isolates were tested regarding antimicrobial susceptibility testing features, screening of carbapenemase genes, and genotyping by multilocus sequencing typing (MLST). All K. pneumoniae isolates were determined as multidrug-resistant (MDR), being mainly resistant to carbapenems, cephalosporins, and fluoroquinolones. The blaNDM-7 (60.9%-14/23) and blaNDM-1 (34.8%-8/23) variants were detected. MLST genotyping revealed the predomination of HRCs, including ST11/CC258, ST340/CC258, ST15/CC15, ST392/CC147, among others. To conclude, the present study reveals the contribution of HRCs and non-HRCs in the spread of NDM-1 and NDM-7-producing K. pneumoniae isolates in Northern (Amazon region) Brazil, along with the first detection of NDM-7 variant in Latin America and Brazil, highlighting the need for surveillance and control of strains that may negatively impact healthcare and antimicrobial resistance.

Emergence and Expansion of a Carbapenem-Resistant Pseudomonas aeruginosa Clone Are Associated with Plasmid-Borne bla KPC-2 and Virulence-Related Genes

Pseudomonas aeruginosa is a major opportunistic pathogen and one of the leading bacterial species causing health care-associated infections. Carbapenems are the most effective antimicrobial agents for the treatment of severe infections caused by P. aeruginosa However, our recent surveillance demonstrated that the prevalence of carbapenem-resistant P. aeruginosa (CRPA) reached 38.67% in Zhejiang, China. By analyzing CRPA isolates collected from patients from 2006 to 2018, we found that 33% of CRPA isolates carried the gene bla _KPC-2, which conferred high-level resistance to carbapenems and other β-lactams. In particular, a CRPA clone, ST463 (sequence type 463), emerged and has become the predominant CRPA clone among the population. Genome sequencing demonstrated that ST463 expansion was associated with plasmid-borne bla _KPC-2 The mobile element flanking bla _KPC-2, the type IV secretion system, and the successful expansion of clone ST463 might have further favored bla _KPC-2 spread in P. aeruginosa Molecular clock analysis dated the emergence of clone ST463 to around 2007. Genome-wide association analysis showed that 567 genes were associated with clone ST463, including several known virulence genes related to the biosynthesis of lipooligosaccharide (LOS) O-antigens and exotoxin. These findings indicate that ST463 is expanding with plasmid-borne bla _KPC-2 and virulence-related genes in nosocomial infections, and close surveillance should be undertaken in the future.IMPORTANCE Health care-associated infections, also known as nosocomial infections, are the most frequent adverse events in health care delivery worldwide, causing high rates of morbidity and mortality and high health care costs. Pseudomonas aeruginosa is one of the leading bacterial species causing health care-associated infections. Carbapenems are the most effective antimicrobial agents for the treatment of its severe infections. However, the prevalence of carbapenem-resistant P. aeruginosa (CRPA) has been increasing rapidly in recent years, and our surveillance demonstrated that the prevalence of CRPA reached 38.67% in Zhejiang, China. Genome sequencing of CRPA isolates over a decade showed that a CRPA clone (ST463) emerged recently. The clone is highly resistant to β-lactams, including carbapenems, and fluoroquinolones. Genome-wide association analysis showed that the clone expanded with virulence-related genes and the plasmid-borne carbapenem-resistant gene bla _KPC-2 These findings are of significant public health importance, as the information will facilitate the control and minimization of CRPA nosocomial infections.

Genomic Characterization of Clinical Extensively Drug-Resistant Acinetobacter pittii Isolates

Carbapenem-resistant Acinetobacter pittii (CRAP) is a causative agent of nosocomial infections. This study aimed to characterize clinical isolates of CRAP from a tertiary hospital in Northeast Thailand. Six isolates were confirmed as extensively drug-resistant Acinetobacter pittii (XDRAP). The bla_NDM-1 gene was detected in three isolates, whereas bla_IMP-14 and bla_IMP-1 were detected in the others. Multilocus sequence typing with the Pasteur scheme revealed ST220 in two isolates, ST744 in two isolates, and ST63 and ST396 for the remaining two isolates, respectively. Genomic characterization revealed that six XDRAP genes contained antimicrobial resistance genes: ST63 (A436) and ST396 (A1) contained 10 antimicrobial resistance genes, ST220 (A984 and A864) and ST744 (A56 and A273) contained 9 and 8 antimicrobial resistance genes, respectively. The single nucleotide polymorphism (SNP) phylogenetic tree revealed that the isolates A984 and A864 were closely related to A. pittii YB-45 (ST220) from China, while A436 was related to A. pittii WCHAP100020, also from China. A273 and A56 isolates (ST744) were clustered together; these isolates were closely related to strains 2014S07-126, AP43, and WCHAP005069, which were isolated from Taiwan and China. Strict implementation of infection control based upon the framework of epidemiological analyses is essential to prevent outbreaks and contain the spread of the pathogen. Continued surveillance and close monitoring with molecular epidemiological tools are needed.

Resistance of Klebsiella pneumoniae Strains Carrying bla NDM-1 Gene and the Genetic Environment of bla NDM-1

OBJECTIVE

Regional dissemination is the major cause of the widespread prevalence of a plasmid-encoding NDM-1 enzyme. We investigated the drug resistance, joint efficiency, and gene environment of a Klebsiella pneumoniae strain carrying bla NDM-1 gene.

MATERIALS AND METHODS

Carbapenem-non-susceptible strains were analyzed using the VITEK 2 Compact. Strains carrying bla NDM-1 were identified using polymerase chain reaction and sequencing. Antimicrobial susceptibility testing and plasmid conjugation experiments were then conducted. Strains carrying bla NDM-1 were subjected to Southern blot analysis. After the gene mapping of bla NDM-1, library construction, and sequencing, plasmids were subsequently spliced and genotyped using the software Glimmer 3.0, and then analyzed using Mauve software.

RESULTS

Among 1735 carbapenem-non-susceptible strains, 54 strains of bla NDM-1-positive bacteria were identified, which consisted of 44 strains of K. pneumoniae, 8 strains of Acinetobacter baumannii and 2 strains of Escherichia coli. Strains carrying bla NDM-1 had a resistance rate of more than 50% in most antibiotics. Plasmid conjugation between strains carrying bla NDM-1 and E. coli strain J53 had a success rate of 50%. Southern blot analysis indicated that each strain had multiple plasmids containing bla NDM-1. Among the five plasmids containing bla NDM-1 in K. pneumoniae for sequencing, two plasmids with complete sequences were obtained. The findings were as follows: (i) The p11106 and p12 plasmids were highly similar to pNDM-BTR; (ii) the p11106 and p12 plasmids showed differences in the 20-30 kb region (orf00032-orf00043) from the other six plasmids; and (iii) bla NDM-1 was located at orf00037, while ble was found at orf00038. Two tnpA genes were located in the upstream region, and orf00052 (tnpA) in the 36 kb region was in the downstream sequence.

CONCLUSION

bla NDM-1-containing bacteria exhibit multidrug resistance, which rapidly spreads and is transferred through efficient plasmid conjugation; the multidrug resistance of these bacteria may be determined by analyzing their drug-resistant plasmids. The presence of ble and tnpA genes suggests a possible hypothesis that bla NDM-1 originates from A. baumannii, which is retained in K. pneumoniae over a long period by transposition of mobile elements.

Genomic and Clinical Characterization of IMP-1-Producing Multidrug-Resistant Acinetobacter bereziniae Isolates from Bloodstream Infections in a Brazilian Tertiary Hospital

Acinetobacter baumannii is the main species of the Acinetobacter genus; however, non-baumannii Acinetobacter (NBA) species causing infections have been described for the past years, as well as antimicrobial resistance. In this study, we describe the occurrence of two multidrug-resistant (MDR) IMP-1-producing Acinetobacter bereziniae isolates recovered from bloodstream infections in different patients but in the same intensive care unit among 134 carbapenem-resistant Acinetobacter screened. Antimicrobial susceptibility testing revealed resistance to carbapenems, extended spectrum, and antipseudomonad cephalosporins, amikacin, and trimethoprim-sulfamethoxazole. Both A. bereziniae isolates shared the same ApaI-pulsed-field gel electrophoresis (PFGE) pattern. Whole-genome sequencing of both isolates revealed that bla_IMP-1 was embedded into an In86 Class I integron carrying also sul1, aac(6')-31, and aadA genes. A new sequence type (ST1309 Pasteur) was deposited. The virulence genes lpxC and ompA, seen in A. baumannii, were detected in the A. bereziniae strains. Recognition of A. bereziniae causing invasive MDR infection underscores the role of NBA species as human pathogens especially in at-risk patients.

Carbapenemase-producing bacteria in food-producing animals, wildlife and environment: A challenge for human health

Antimicrobial resistance is an increasing global health problem and one of the major concerns for economic impacts worldwide. Recently, resistance against carbapenems (doripenem, ertapenem, imipenem, meropenem), which are critically important antimicrobials for human cares, poses a great risk all over the world. Carbapenemases are β-lactamases belonging to different Ambler classes (A, B, D) and encoded by both chromosomal and plasmidic genes. They hydrolyze a broad variety of β-lactams, including carbapenems, cephalosporins, penicillins and aztreonam. Despite several studies in human patients and hospital settings have been performed in European countries, the role of livestock animals, wild animals and the terrestrial and aquatic environment in the maintenance and transmission of carbapenemase- producing bacteria has been poorly investigated. The present review focuses on the carbapenemase-producing bacteria detected in pigs, cattle, poultry, fish, mollusks, wild birds and wild mammals in Europe as well as in non-European countries, investigating the genetic mechanisms for their transmission among food-producing animals and wildlife. To shed light on the important role of the environment in the maintenance and genetic exchange of resistance determinants between environmental and pathogenic bacteria, studies on aquatic sources (rivers, lakes, as well as wastewater treatment plants) are described.

NDM Metallo-β-Lactamases and Their Bacterial Producers in Health Care Settings

New Delhi metallo-β-lactamase (NDM) is a metallo-β-lactamase able to hydrolyze almost all β-lactams. Twenty-four NDM variants have been identified in >60 species of 11 bacterial families, and several variants have enhanced carbapenemase activity. Klebsiella pneumoniae and Escherichia coli are the predominant carriers of bla _NDM, with certain sequence types (STs) (for K. pneumoniae, ST11, ST14, ST15, or ST147; for E. coli, ST167, ST410, or ST617) being the most prevalent. NDM-positive strains have been identified worldwide, with the highest prevalence in the Indian subcontinent, the Middle East, and the Balkans. Most bla _NDM-carrying plasmids belong to limited replicon types (IncX3, IncFII, or IncC). Commonly used phenotypic tests cannot specifically identify NDM. Lateral flow immunoassays specifically detect NDM, and molecular approaches remain the reference methods for detecting bla _NDM Polymyxins combined with other agents remain the mainstream options of antimicrobial treatment. Compounds able to inhibit NDM have been found, but none have been approved for clinical use. Outbreaks caused by NDM-positive strains have been reported worldwide, attributable to sources such as contaminated devices. Evidence-based guidelines on prevention and control of carbapenem-resistant Gram-negative bacteria are available, although none are specific for NDM-positive strains. NDM will remain a severe challenge in health care settings, and more studies on appropriate countermeasures are required.

Co-occurrence of carbapenemase encoding genes in Acinetobacter baumannii, a dream or reality?

BACKGROUND

Acinetobacter baumannii is an important opportunistic pathogen that is rapidly evolving towards multidrug resistance and is responsible for life-threatening infections. Carbapenems are commonly used to treat A. baumannii infections but the emergence of carbapenemase encoding genes, such as blaOXA-23-like, blaOXA-24-like, blaOXA-58-like, and blaNDM has been reported. Moreover, several studies have reported the co-occurrence of two distinct carbapenemases in some isolates. The aim of the present study is to demonstrate whether the phenomenon of co-occurrence of two distinct carbapenemase encoding genes in a single isolate still exists.

RESULTS

We studied six strains of A. baumannii including one harboring blaOXA-23-like and blaOXA-24-like genes and five with blaOXA-23-like and blaNDM genes. One colony of each strain was inoculated in sterile water and diluted ten-fold. Each dilution was cultivated on trypticase soy agar plates for 24 h at 37 °C and the isolated bacteria were analyzed. For two of the six tested strains, we identified two different populations of A. baumannii, each with a different carbapenemase, genes encoding aminoglycoside modifying enzymes, resistance phenotype, and clonal type. In addition, the two different populations had the same aspect on the agar plate.

CONCLUSIONS

Here, we demonstrate that A. baumannii infections could be linked to multiple clones harboring different carbapenemase encoding genes in the same sample. In addition, we describe an easy method of verifying the presence of co-occurrence of carbapenemase in one isolate.

Emergence of antimicrobial resistance among Acinetobacter species: a global threat

PURPOSE OF REVIEW

Bacteria within the genus Acinetobacter [principally Acinetobacter baumannii-calcoaceticus complex (ABC)] are Gram-negative coccobacilli that may cause serious nosocomial infections (particularly ventilator-associated pneumonia and infections of the bloodstream, urinary tract, and wounds) as well as community-acquired infections (often skin/soft tissue infections in the context of trauma). Within the past two decades, Acinetobacter spp. have been responsible for an increasing number of infections in intensive care units (ICUs) globally. Treatment of Acinetobacter infections is difficult, as Acinetobacter spp. are intrinsically resistant to multiple antimicrobial agents, and have a remarkable ability to acquire new resistance determinants via multiple mechanisms.

RECENT FINDINGS

Since the 1990s, global resistance to antimicrobials has escalated dramatically among ABC. Global spread of multidrug-resistant (MDR) A. baumannii strains reflects dissemination of a few clones between hospitals, geographic regions, and continents; this spread is amplified by excessive use of antibiotics. Many isolates are resistant to all antimicrobials except colistin (polymyxin E), and some infections are untreatable with existing antimicrobial agents.

SUMMARY

Antimicrobial resistance poses a serious threat to control infections due to ABC. Strategies to curtail environmental colonization with MDR-ABD will require aggressive infection control efforts and cohorting of infected patients. Thoughtful antibiotic strategies are essential to limit the consequences and spread of MDR-ABC. Optimal therapy will likely require combination antimicrobial therapy of existing antibiotics as well as development of novel antibiotic classes.

Comparison of clinical manifestations and antibiotic resistances among three genospecies of the Acinetobacter calcoaceticus-Acinetobacter baumannii complex

The Acinetobacter calcoaceticus-Acinetobacter baumannii (ACB) complex has emerged as a high priority among hospital-acquired pathogens in intensive care units (ICUs), posing a challenge to infection management practices. In this study, the clinical characteristics, antimicrobial susceptibility patterns, and patients outcome among genospecies were retrospectively compared. Samples were taken from the tracheal secretions of 143 patients in the ICU. Genospecies of the ACB complex were discriminated by analysis of the 16S-23S rRNA gene intergenic spacer (ITS) sequence. Univariate and multiple variable logistic regression analyses were performed to identify risk factors for infection and mortality. Three genospecies were isolated: A. baumannii (73, 51.0%), A. nosocomialis (29, 20.3%), and A. pittii (41, 28.7%). The results showed that the distribution of infection and colonization among the three genospecies were the same, while A. baumannii was more resistant to common antibiotics than A. nosocomialis and A. pittii. Advanced age, a long stay in the ICU, acute physiology and chronic health evaluation (APACHE) II score, the use of a mechanical ventilator, and previous antibiotic use were risk factors for patient infection. The APACHE II score was a risk factor for mortality in patients with ACB complex isolated from tracheal secretions. Poor outcome of patients with ACB complex isolated from tracheal secretion appears to be related to the APACHE II score rather than genospecies.

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.

Emergence of Acinetobacter pittii harboring New Delhi metallo-beta-lactamase genes in Daejeon, Korea

Carbapenemase production has been reported worldwide in gram-negative bacteria, including Acinetobacter species. We detected carbapenemase-producing Acinetobacter pittii in clinical isolates in Daejeon, Korea. Twenty-one ertapenem-resistant A. pittii isolates screened with a disk diffusion method were characterized by using the Epsilon test, four multiplex PCR assays, and a multilocus sequence typing (MLST) scheme. A total of 21 A. pittii isolates harbored the metallo-β-lactamase (MBL) gene bla(IMP-1) or bla(NDM-1). Nineteen isolates containing bla(IMP-1) were resistant to imipenem and meropenem, but two isolates harboring bla(NDM-1) were susceptible to them. The sequence types (STs) of the two New Delhi MBL (NDM-1)-producing A. pittii isolates were ST70 and ST207, which differed from the STs (ST63, ST119, ST396, and a novel ST) of the IMP-1-producing A. pittii. This is the first report on NDM-1-producing A. pittii isolates in Korea. Our results emphasize that the study of NDM-1-producing gram-negative bacteria should involve carbapenem-susceptible as well as carbapenem-resistant isolates.

Emergence of NDM-1 and OXA-72 producing Acinetobacter pittii clinical isolates in Lebanon

Acinetobacter spp. have emerged as global opportunistic pathogen causing a wide range of infections. Emergence of carbapenem resistance in these organisms is a matter of great concern. We report here the first detection of Acinetobacter pittii clinical isolates in Lebanon carrying either the bla NDM-1 or the bla OXA-72 gene.

Characterization of Tn3000, a Transposon Responsible for blaNDM-1 Dissemination among Enterobacteriaceae in Brazil, Nepal, Morocco, and India

In Enterobacteriaceae, the blaNDM genes have been found in many different genetic contexts, and a wide diversity of plasmid scaffolds bearing those genes has been found. In August 2013, we identified NDM-1-producing Escherichia coli and Enterobacter hormaechei strains from a single rectal swab sample from a patient hospitalized in Rio de Janeiro, Brazil, who had no history of travel abroad. Complete DNA sequencing using the Illumina platform and annotation of the two plasmids harboring the blaNDM-1 gene, one from each strain, showed that they belonged to incompatibility groups IncFIIK and IncX3 and harbored a novel transposon named Tn3000. Similar genetic structures have been identified among other isolates in Brazil but also on plasmids from other continents. Our findings suggest that the blaNDM-1 gene may be transmitted by Tn3000 in different parts of the world.

Rapid detection of porins by matrix-assisted laser desorption/ionization-time of flight mass spectrometry

The rapid and cost-efficient determination of carbapenem resistance is an important prerequisite for the choice of an adequate antibiotic therapy. A MALDI-TOF MS-based assay was set up to detect porins in the current study. A loss of the components of porin alone such as OmpK35/OmpK36 or together with the production of carbapenemases will augment the carbapenem resistance. Ten strains of Escherichia coli and eight strains of Klebsiella pneumoniae were conducted for both sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and MALDI-TOF MS analysis. MALDI-TOF/TOF MS analysis was then performed to verify the correspondence of proteins between SDS-PAGE and MALDI-TOF MS. The results indicated that the mass spectrum of ca. 35,000, 37,000, and 38,000-m/z peaks of E. coli ATCC 25922 corresponded to OmpA, OmpC, and OmpF with molecular weight of approximately ca. 38, 40, and 41 kDa in SDS-PAGE gel, respectively. The band of OmpC and OmpF porins were unable to be distinguished by SDS-PAGE, whereas it was easy to be differentiated by MALDI-TOF MS. As for K. pneumoniae isolates, the mass spectrum of ca. 36,000 and 38,600-m/z peaks was observed corresponding to OmpA and OmpK36 with molecular weight of approximately ca. 40 and 42 kDa in SDS-PAGE gel, respectively. Porin OmpK35 was not observed in the current SDS-PAGE, while a 37,000-m/z peak was found in K. pneumoniae ATCC 13883 and carbapenem-susceptible strains by MALDI-TOF MS which was presumed to be the characteristic peak of the OmpK35 porin. Compared with SDS-PAGE, MALDI-TOF MS is able to rapidly identify the porin-deficient strains within half an hour with better sensitivity, less cost, and is easier to operate and has less interference.

Emergence of KPC-2-producing Pseudomonas aeruginosa sequence type 463 isolates in Hangzhou, China

Thirty-nine Klebsiella pneumoniae carbapenemase (KPC)-producing Pseudomonas aeruginosa isolates, all exhibiting high-level resistance to carbapenems and other β-lactam antibiotics, were isolated in Hangzhou, China. Molecular epidemiology analysis indicated the presence of two dominant clones, namely, clones A and B, both of which belong to sequence type 463 (ST463). A genetic environment analysis demonstrated that both clones harbor an ISKpn8 transposase, bla(KPC-2), and an ISKpn6-like transposase. These findings depict the features of clonal expansion and transmission of KPC-2-producing P. aeruginosa strains in Hangzhou, China.

Molecular epidemiology of carbapenem-resistant Acinetobacter baumannii isolates in the Gulf Cooperation Council States: dominance of OXA-23-type producers

The molecular epidemiology and mechanisms of resistance of carbapenem-resistant Acinetobacter baumannii (CRAB) were determined in hospitals in the states of the Cooperation Council for the Arab States of the Gulf (Gulf Cooperation Council [GCC]), namely, Saudi Arabia, United Arab Emirates, Oman, Qatar, Bahrain, and Kuwait. Isolates were subjected to PCR-based detection of antibiotic resistance genes and repetitive sequence-based PCR (rep-PCR) assessments of clonality. Selected isolates were subjected to multilocus sequence typing (MLST). We investigated 117 isolates resistant to carbapenem antibiotics (either imipenem or meropenem). All isolates were positive for OXA-51. The most common carbapenemases were the OXA-23-type, found in 107 isolates, followed by OXA-40-type (OXA-24-type), found in 5 isolates; 3 isolates carried the ISAba1 element upstream of blaOXA-51-type. No OXA-58-type, NDM-type, VIM-type, or IMP-type producers were detected. Multiple clones were detected with 16 clusters of clonally related CRAB. Some clusters involved hospitals in different states. MLST analysis of 15 representative isolates from different clusters identified seven different sequence types (ST195, ST208, ST229, ST436, ST450, ST452, and ST499), as well as three novel STs. The vast majority (84%) of the isolates in this study were associated with health care exposure. Awareness of multidrug-resistant organisms in GCC states has important implications for optimizing infection control practices; establishing antimicrobial stewardship programs within hospital, community, and agricultural settings; and emphasizing the need for establishing regional active surveillance systems. This will help to control the spread of CRAB in the Middle East and in hospitals accommodating transferred patients from this region.

Carbapenem-resistant Enterobacteriaceae: biology, epidemiology, and management

Introduced in the 1980s, carbapenem antibiotics have served as the last line of defense against multidrug-resistant Gram-negative organisms. Over the last decade, carbapenem-resistant Enterobacteriaceae (CRE) have emerged as a significant public health threat. This review summarizes the molecular genetics, natural history, and epidemiology of CRE and discusses approaches to prevention and treatment.

Characterization and plasmid elimination of NDM-1-producing Acinetobacter calcoaceticus from China

The presence of multidrug-resistant bacterial pathogens in the environment poses a serious threat to public health. The opportunistic Acinetobacter spp. are among the most prevalent causes of nosocomial infections. Here, we performed complete genome sequencing of the Acinetobacter calcoaceticus strain XM1570, which was originally cultivated from the sputum of a patient diagnosed with pneumonia in Xiamen in 2010. We identified carbapenem resistance associated gene bla_NDM-1 located on a 47.3-kb plasmid. Three methods – natural reproduction, sodium dodecyl sulfate treatment and nalidixic acid treatment – were used to eliminate the bla_NDM-1-encoding plasmid, which achieved elimination rates of 3.32% (10/301), 83.78% (278/332), and 84.17% (298/354), respectively. Plasmid elimination dramatically increased antibiotic sensitivity, reducing the minimum bacteriostatic concentration of meropenem from 256 µg/ml in the clinical strain to 0.125 µg/ml in the plasmid-eliminated strain. Conjugation transfer assays showed that the bla_NDM-1-containing plasmid could be transferred into Escherichia coli DH5α:pBR322 in vitro as well as in vivo in mice. The bla_NDM-1 genetic environment was in accordance with that of other bla_NDM-1 genes identified from India, Japan, and Hong-Kong. The multilocus sequence type of the isolate was identified as ST-70. Two novel genes encoding intrinsic OXA and ADC were identified and named as OXA-417 and ADC-72. The finding of bla_NDM-1 in species like A. calcoaceticus demonstrates the wide spread of this gene in gram-negative bacteria which is possible by conjugative plasmid transfer. The results of this study may help in the development of a treatment strategy for controlling NDM-1 bacterial infection and transmission.