Multidrug-Resistant Sequence Type 235 Pseudomonas aeruginosa Clinical Isolates Producing IMP-26 with Increased Carbapenem-Hydrolyzing Activities in Vietnam.

Forty clinical isolates of multidrug-resistant Pseudomonas aeruginosa were obtained in a medical setting in Hanoi, Vietnam. Whole genomes of all 40 isolates were sequenced by MiSeq (Illumina), and phylogenic trees were constructed from the single nucleotide polymorphism concatemers. Of these 40 isolates, 24 (60.0%) harbored metallo-ß-lactamase-encoding genes, including blaIMP-15, blaIMP-26, blaIMP-51, and/or blaNDM-1 Of these 24 isolates, 12 harbored blaIMP-26 and belonged to sequence type 235 (ST235). Escherichia coli expressing blaIMP-26 was significantly more resistant to doripenem and meropenem than E. coli expressing blaIMP-1 and blaIMP-15 IMP-26 showed higher catalytic activity against doripenem and meropenem than IMP-1 and against all carbapenems tested, including doripenem, imipenem, meropenem, and panipenem, than did IMP-15. These data suggest that clinical isolates of multidrug-resistant ST235 P. aeruginosa producing IMP-26 with increased carbapenem-hydrolyzing activities are spreading in medical settings in Vietnam.

IMP-51, a novel IMP-type metallo-ß-lactamase with increased doripenem- and meropenem-hydrolyzing activities, in a carbapenem-resistant Pseudomonas aeruginosa clinical isolate.

A meropenem-resistant Pseudomonas aeruginosa isolate was obtained from a patient in a medical setting in Hanoi, Vietnam. The isolate was found to have a novel IMP-type metallo-ß-lactamase, IMP-51, which differed from IMP-7 by an amino acid substitution (Ser262Gly). Escherichia coli expressing blaIMP-51 showed greater resistance to cefoxitin, meropenem, and moxalactam than E. coli expressing blaIMP-7. The amino acid residue at position 262 was located near the active site, proximal to the H263 Zn(II) ligand.

Evaluation of the Etest method for detecting colistin susceptibility of multidrug-resistant Gram-negative isolates in Vietnam.

The minimum inhibitory concentrations (MICs) of colistin for 241 multidrug-resistant (MDR) Gram-negative pathogens were determined by the Etest and by the broth microdilution method (BMD). The two methods showed essential agreements of 76% (77/102) for Acinetobacter baumannii, 90% (36/40) for Pseudomonas aeruginosa and 84% (83/99) for Enterobacteriaceae isolates, with categorical agreements of 100%, 98%, and 100%, respectively. Of the 241 isolates, none showed a very major error and one (0.4%) showed a major error. MICs ranged from 0.125 to 0.5 µg/ml for all A. baumannii and most Enterobacteriaceae isolates, and from 1 to 2 µg/ml for most P. aeruginosa isolates. Of the 40 P. aeruginosa isolates, 27 (68%) showed higher colistin MICs by the Etest than by the BMD. In contrast, 77% (78/102) of the A. baumannii and 57% (56/99) of the Enterobacteriaceae isolates showed lower colistin MICs by the Etest than by the BMD. The Etest is a reliable and easy-to-use method to measure colistin MICs of MDR Gram-negative pathogens in clinical laboratories and can be used following validation by microdilution methods.

Emergence of 16S rRNA methylase-producing Acinetobacter baumannii and Pseudomonas aeruginosa isolates in hospitals in Vietnam.

BACKGROUND: 16S rRNA methylase-producing Gram-negative bacteria are highly resistant to all clinically important aminoglycosides. We analyzed clinical strains of 16S rRNA methylase-producing Acinetobactor baumannii and Pseudomonas aeruginosa obtained from clinical isolates in medical settings in Vietnam. METHODS: From 2008 to 2011, 101 clinical strains of A. baumannii and 15 of P. aeruginosa were isolated from patients in intensive care units (ICUs) in two medical settings in Vietnam. Antimicrobial susceptibilities were determined using the microdilution method and epidemiological analysis was performed by pulsed-field gel electrophoresis and MLST. Genes encoding the 16S rRNA methylases, OXAs and CTX-Ms were analyzed by PCR and sequence analysis. RESULTS: 16S rRNA methylase-producing Gram-negative pathogens were detected in two hospitals in Vietnam. Of the 101 clinical isolates of A. baumannii and the 15 of P. aeruginosa isolated from two ICUs in these hospitals, 72 (71.3%) were highly resistant to amikacin, arbekacin and gentamicin, with MICs greater than 1,024 mg/L. The 16S rRNA methylases ArmA and RmtB were produced by 61 and 9 isolates of A. baumannii, respectively, and RmtB was produced by 2 isolates of P. aeruginosa. Moreover, 52 of the A. baumannii isolates producing 16S rRNA methylases harbored both blaOXA-23-like and blaOXA-51-like genes. Most A. baumannii isolates producing 16S rRNA methylase obtained in hospital A in Hanoi were ST91 and ST231, whereas most from hospital B in Ho Chi Minh City were ST136, ST195, and ST254. CONCLUSIONS: Gram-negative bacteria producing the 16S rRNA methylases ArmA and RmtB are emerging in medical settings in Vietnam. A. baumannii isolates in northern and southern regions of Vietnam may be of different lineages.

Clinical and microbiological evaluation of ventilator-associated pneumonia in an intensive care unit in Vietnam.

Background: The increasing incidence of multidrug-resistant Gram-negative bacteria causing ventilator-associated pneumonia (VAP) is a global concern. A better understanding of the epidemiology of VAP in Southeast Asia is essential to optimise treatments and patient outcomes. Methods: VAP epidemiology in an intensive care unit in Vietnam was investigated. A prospective cohort study was conducted. Patients who were ventilated for >48 hours, diagnosed with VAP, and had a positive respiratory culture between October 2015 and March 2017 were included. Whole-genome sequencing (WGS) was performed on Acinetobacter baumannii isolates. Results: We identified 125 patients (137 episodes) with VAP from 1,699 admissions. Twelve patients had 2 VAP episodes. The median age was 60 years (interquartile range: 48-70), and 68.8% of patients were male. Diabetes mellitus was the most frequent comorbidity (N=35, 28%). Acinetobacter baumannii was most frequently isolated in the first VAP episode (N=84, 67.2%) and was multiply resistant to meropenem, levofloxacin, and amikacin. The 30-day mortality rate was 55.2% (N=69) and higher in patients infected with A. baumannii (N=52, 65%). WGS results suggested a complex spread of multiple clones. Conclusions: In an intensive care unit in Vietnam, VAP due to A. baumannii had a high mortality rate, and A. baumannii and K. pneumoniae were multidrug resistant, with carbapenem resistance of 97% and 70%, respectively.

Antimicrobial susceptibility of Burkholderia pseudomallei isolates in Northern Vietnam.

OBJECTIVES: The antimicrobial susceptibility pattern of clinical Burkholderia pseudomallei (B. pseudomallei) in Vietnam has not been reported since the first publication in 2008. The present study aimed to determine the antimicrobial susceptibility pattern of B. pseudomallei isolated in a tertiary referral centre in Hanoi from January 2012 to December 2017. METHODS: A total of 312 B. pseudomallei isolates obtained from melioidosis patients admitted to a 2000-bed general hospital were analysed by the Etest method. Interpretation of the susceptibility testing results were reported using Clinical and Laboratory Standards Institute guidelines. RESULTS: All isolates were susceptible to ceftazidime, imipenem and amoxicillin-clavulanate (100%) with MIC90s relatively low (2µg/mL). Two isolates had intermediate resistance to doxycycline (0.6%) and 34 isolates were resistant to trimethoprim/sulfamethoxazole (10.9%). CONCLUSION: The results of this study suggest that currently recommended antibiotics for melioidosis treatment can be empirically used, but continuously monitoring antimicrobial susceptibility should be a concern.

Assessment of Bacteremia in a Large Tertiary Care Hospital in Northern Vietnam: a Single-Center Retrospective Surveillance Study.

The clinical analysis of cases of bacteremia is valuable. However, limited data on bacteremia are available in Vietnam. We conducted a single-center retrospective surveillance study at the Bach Mai Hospital, Hanoi, Vietnam between 2009 and 2012. In total, 45,366 blood cultures were analyzed. The number of blood cultures per 1,000 patient-days was 9.59 sets. The percentage of solitary blood culture sets was 49.6%, and the rate of positive blood cultures was 13.9%. The major pathogens isolated in adults were coagulase-negative Staphylococcus species (16.7%), followed by Escherichia coli (6.8%), Streptococcus spp. excluding Streptococcus pneumoniae (3.8%), and Staphylococcus aureus (5.2%). Other major pathogens identified were Klebsiella spp. (4.2%) and Acinetobacter spp. (2.2%). The number of blood cultures per 1,000 patient-days was lower and the percentage of solitary blood culture sets higher than that of a Japanese study (9.6 vs. 25.2 and 49.6% vs. 32.8%, respectively). The distribution of microorganisms was unique in terms of the relative predominance of cases of Acinetobacter bacteremia. The percentage of cases of healthcare-associated bacteremia may be relatively high.

Drug-resistant pneumococci in children with acute lower respiratory infections in Vietnam.

BACKGROUND: Acute lower respiratory infections (ALRI), primarily pneumonia, are the leading cause of death in children under 5 years of age. Most of these deaths occur in Africa and southeast Asia. Increasing rates of drug resistance in pneumococcal strains emphasize the necessity of prevention of pneumococcal vaccines. The aim of the present study was to determine the frequency of drug resistance and the distribution of serotype of pneumococcal strains isolated from pediatric patients with ALRI in Vietnam. METHODS: Two hundred and twenty pediatric patients with ALRI under 5 years of age were enrolled in Hanoi, Vietnam between 2001 and 2002. Bacterial pathogens with a heavy growth (10(6) c.f.u./mL) were isolated from nasopharyngeal secretions on quantitative culture. Fifty-three pneumococcal strains isolated from the nasopharynx of pediatric patients were examined for antibiotic susceptibility including drug-resistant genes and serotyping. RESULTS: A total of 73.6% of pneumococcal strains were genotypic penicillin-resistant Streptococcus pnemoniae (gPRSP), possessing altered penicillin-binding protein genes pbp 1a + 2x + 2b; 67.9% of these strains were gPRSP and simultaneously had the ermB gene, which is responsible for high resistance to erythromycin. The majority of gPRSP strains were serotype 19F or 23F. CONCLUSION: gPRSP strains with serotype 19F or 23F are highly prevalent among pediatric patients with ALRI under 5 years of age in Hanoi, Vietnam.

Emergence of colistin-resistant Escherichia coli clinical isolates harboring mcr-1 in Vietnam.

The mcr-1 was first detected on a plasmid in colistin-resistant Escherichia coli from livestock and patients in China. We described here the emergence of colistin-resistant E. coli clinical isolates harboring mcr-1 on the chromosomes in Vietnam. To our knowledge, this is the first report of hospital-acquired E. coli isolates harboring mcr-1 in a medical setting in Vietnam.

Antimicrobial-resistant Pseudomonas aeruginosa and Acinetobacter baumannii From Patients With Hospital-acquired or Ventilator-associated Pneumonia in Vietnam.

PURPOSE: Multidrug-resistant bacterial pathogens are becoming a significant problem worldwide. Acinetobacter baumannii and Pseudomonas aeruginosa are problematic multidrug-resistant pathogens. This multicenter study in Vietnam determined the level of resistance to antimicrobial agents used to treat A baumannii and P aeruginosa infections in this country. METHODS: Five medical centers in Vietnam provided 529 P aeruginosa and 971 Acinetobacter species (904 A baumannii) isolates from patients with hospital-acquired or ventilator-associated pneumonia from 2012 to 2014. A central laboratory verified identification of the isolates and performed susceptibility testing using Clinical and Laboratory Standards Institute methods. FINDINGS: Resistance to cephalosporins, ß-lactam/ß-lactamase inhibitors, carbapenems, and fluoroquinolones was >90% against A baumannii. Aminoglycosides had only slightly better activity, with amikacin resistance >80%. Only colistin (MIC90, ≤0.25 mg/L) and tigecycline (MIC90, 4 mg/L) had appreciable activity against A baumannii. Similar activity was observed among the ß-lactams tested against P aeruginosa. Cefepime demonstrated the highest activity (60.1% susceptible), which was similar to doripenem (58.6% susceptible), the most active carbapenem tested. Amikacin was the most active aminoglycoside tested against P aeruginosa, with susceptibility of 81.7% compared with tobramycin (58.0%) and gentamicin (56.5%). Fluoroquinolones had limited activity against P aeruginosa with susceptibility to ciprofloxacin (55.0%). All P aeruginosa isolates had colistin MIC values ≤2 mg/L. IMPLICATIONS: The data from this 3-year longitudinal study in Vietnam demonstrate that 2 of the most common nonfermentative gram-negative pathogens associated with hospital-acquired and ventilator-associated pneumonia are significantly resistant to most of the available treatment options and require combination therapies unless new antimicrobial agents become available.

The efficacy and nephrotoxicity associated with colistin use in an intensive care unit in Vietnam: Use of colistin in a population of lower body weight.

BACKGROUND: There has been a growing need for colistin as a key drug for the treatment of MDR-GNB infection. Information on colistin use in Asian population is limited. METHODS: A retrospective observational study was conducted to assess the efficacy and nephrotoxicity in critically ill adult patients who received intravenous colistin for MDR-GNB infection in the intensive care unit (ICU) at Bach Mai Hospital in Hanoi, Vietnam. Colistin was administered according to the dosing guideline that was based on pharmacokinetic, pharmacodynamic and toxicodynamic principles, adjusted by body weight and creatinine clearance. RESULTS: Twenty-eight eligible patients were included. The mean patient age was 60±20.4 years. The mean body weight was 53±8.6kg. The mean daily dose of colistin was 4.1±1.6 MIU, and the mean cumulative dose of colistin was 48.2±22.8 MIU. Colistin therapies were classified as clinically effective in 19 (67.9%) cases. Six (21.4%) patients developed nephrotoxicity during the study period according to RIFLE criteria. CONCLUSION: A personalized dosing protocol of colistin was effective, with low nephrotoxicity, among critically ill Vietnamese patients with low body weight. Further studies are warranted for assessing the efficacy and toxicity in a larger cohort.

Antimicrobial susceptibility and extended-spectrum beta-lactamase rates in aerobic gram-negative bacteria causing intra-abdominal infections in Vietnam: report from the Study for Monitoring Antimicrobial Resistance Trends (SMART 2009-2011).

Treatment options for multidrug-resistant pathogens remain problematic in many regions and individual countries, warranting ongoing surveillance and analysis. Limited antimicrobial susceptibility information is available for pathogens from Vietnam. This study determined the bacterial susceptibility of aerobic gram-negative pathogens of intra-abdominal infections among patients in Vietnam during 2009-2011. A total of 905 isolates were collected from 4 medical centers in this investigation as part of the Study for Monitoring Antimicrobial Resistance Trends. Antimicrobial susceptibility and extended-spectrum beta-lactamase (ESBL) rates among the appropriate species were determined by a central laboratory using Clinical and Laboratory Standards Institute methods. Among the species collected, Escherichia coli (48.1% ESBL-positive) and Klebsiella pneumoniae (39.5% ESBL-positive) represented the majority (46.4%) of the isolates submitted for this study. Ertapenem MIC90 values were lowest for these 2 species at 0.12 and 0.25µg/mL and remained unchanged for ESBL-positive isolates. Imipenem MIC90 values were also the same for all isolates and ESBL-positive strains at 0.25 and 0.5µg/mL, respectively. Ertapenem MIC90 values for additional species with sufficient numbers for analysis, including Enterobacter cloacae, Proteus mirabilis, Acinetobacter baumannii, and Pseudomonas aeruginosa, were 1, 0.06, >4, and >4µg/mL, respectively. Analysis of beta-lactamases in a subset of 132 phenotypically ESBL-positive Enterobacteriaceae demonstrated that CTX-M variants, particularly CTX-M-27 and CTX-M-15, were the predominant enzymes. High resistance rates in Vietnam hospitals dictate continuous monitoring as antimicrobial inactivating enzymes continue to spread throughout Asia and globally.

Clinical and microbiological features of melioidosis in northern Vietnam.

Sporadic cases of melioidosis have been reported from Vietnam for decades, but clinical and epidemiological data for the indigenous population are still scarce. In this study, we reviewed clinical and demographic data of patients with culture-proven melioidosis diagnosed at a single large referral hospital in Hanoi between November 1997 and December 2005. We found that the clinical manifestations of melioidosis (with fatal septicaemia as the most common presentation), a high rate of underlying diseases, and a peak of cases admitted during the wet season, were similar to studies from other endemic areas. The geographical origin of patients with melioidosis showed that melioidosis existed in at least 18 northern provinces. The characterization of clinical Burkholderia pseudomallei strains by multilocus sequence typing identified 17 different sequence types (STs), 11 of which have (as yet) not been found outside Vietnam. Several of these STs presumably were generated through recent evolutionary events in this rapidly diversifying bacterial species, and thus, restricted geographic distribution may be a consequence of limited time passed since emergence. To our knowledge, this is the first report on a series of cases describing clinical and epidemiological features of melioidosis and corresponding B. pseudomallei strains from northern Vietnam.

Increased rates of intense nasopharyngeal bacterial colonization of Vietnamese children with radiological pneumonia.

Acute lower respiratory infection (ALRI), primarily pneumonia, is the leading cause of death in children under the age of five. Bacterial ALRI is preceded by asymptomatic bacterial colonization. Bacterial colonization, therefore, may have an important role in the development of pneumonia in children. This case-control study was conducted in order to determine if intense bacterial colonization was increased in the nasopharynx of pediatric patients with ALRI. One hundred-sixty four pediatric patients with ALRI and 70 healthy children < 5 years of age were enrolled in Hanoi, Vietnam between 2001 and 2002. Bacterial pathogens were isolated from nasopharyngeal secretions and quantitatively cultured. Of 164 patients, 91 were diagnosed as having radiological pneumonia (PN group) and 73 as having acute bronchitis (AB group). Intense growth of any bacterial pathogen (>or= 10(6) colony-forming units/ml) was highest in the PN group (49.4%), followed by the AB group (28.8%), with healthy children having the lowest (17.1%). Patients with intense bacterial growth were more likely to develop pneumonia, but not acute bronchitis, than were patients with light or no bacterial growth. The results of this case-control study suggest that the vertical spread of intense bacterial pathogens colonized in the nasopharynx to the lower airway leads to bacterial pneumonia in children under the age of five.