Molecular epidemiology of bla OXA-23 -producing carbapenem-resistant Acinetobacter baumannii in a single institution over a 65-month period in north China.

BACKGROUND: Carbapenem-resistant Acinetobacter baumannii poses a significant threat to hospitalized patients, as few therapeutic options remain. Thus, we investigated the molecular epidemiology and mechanism of resistance of carbapenem-resistant A.baumannii isolates in Beijing, China. METHODS: Carbapenem-resistant A.baumannii isolates (n = 101) obtained between June 2009 and November 2014 were used. Multilocus sequence typing (MLST) and PCR assays for class C and D ß-lactamase were performed on all isolates. S1 nuclease pulsed-field gel electrophoresis (PFGE) and Southern blot hybridization were performed to identify the resistance gene location. RESULTS: All 101 A.baumannii isolates were highly resistant to frequently used antimicrobials, and were considered multidrug resistant. A total of 12 sequence types (STs) were identified, including 10 reported STs and 2 novel STs. Eighty-seven isolates were classified to clonal complex 92 (CC92), among which ST191 and ST195 were the most common STs. The bla OXA-23 gene was positive in most (n = 95) of the A.baumannii isolates. Using S1-nuclease digestion PFGE and Southern blot hybridization, 3 patterns of plasmids carrying bla OXA-23 were confirmed. ST191 and ST195 (both harboring bla OXA-23 ) caused outbreaks during the study period, and this is the first report of outbreaks caused by ST191 and ST195 in north China. CONCLUSION: bla OXA-23 -producing A.baumannii ST191 and ST 195 isolates can disseminate in a hospital and are potential nosocomial outbreak strains. Surveillance of imipenem-resistant A.baumannii and antimicrobial stewardship should be strengthened.

[Distribution of genotypes in ESBLs producing E. coli strains isolated from posthepatitic cirrhosis' patients with bloodstream infection].

OBJECTIVE: To study the genotype distribution of extended-spectrum beta-lactamases (ESBLs) in ESBLs-producing Escherichia coli (E. coli) isolates from posthepatitic cirrhosis' patients with bloodstream infection. METHODS: E. coli were isolated in bloodstream from patients with posthepatitic cirrhosis between January and December in 2011. The strains were identified by VITEK-II. The antibiol susceptibility tests were performed with K-B method. beta-lactamases genes were detected multi-PCR, PCR, sequence and blast. RESULTS: A total of 79 non-duplicate clinical isolates of E coli were consecutively collected from liver cirrhosis' patients with bloodstream infection. There were 20 isolates produced TEM-1 type beta-lactamases and 1 isolate produced SHV-1 typebeta-lactamases. 40 clinical isolates were detected to produce CTX-M type ESBLs, there were 20 CTX-M-1 group and 26 CTX-M-9 group, including 6 stains habouring both CTX-M-1 and CTX-M-9 group. Eight CTX-M genotypes were confirmed by sequencing of the PCR products, including CTX-M-3, CTX-M-14, CTX-M-15, CTX-M-24, CTX-M-28, CTX-M-31, CTX-M-65 and CTX-M-79. CONCLUSION: CTX-M genotype ESBLs was the most popular extended-spectrum beta-lactamases in E. coli isolated from liver cirrhosis' patients with bloodstream infection. The CTX-M-14 is the dominant epidemic type.

[The distribution and antimicrobial resistance tendency of pathogens associated with diarrhea in Beijing].

OBJECTIVE: To monitor the constituents and resistant tendency of bacterial pathogens isolated from diarrheal patients in our hospital form 1994 to 2005 to offer the basis for guiding epidemiologic study, vaccination research and clinical treatment. METHODS: Enteric pathogenic bacteria were cultured and identified to species, group and serotype with biochemical and serologic methods and the susceptibility of bacteria to antimicrobial agents were tested. RESULTS: Enteric pathogenic bacteria were isolated predominantly in male patients and mainly in children and youngsters. It reached a peak from July to September every year. Shigella spp. (75.11%) was the most frequently isolated pathogens and followed by Vibrio spp. (12.7%), Salmonella spp. (6.28%), Aeromonas spp. (4.43%) and Escherichia coli (1.25%). During the period from 1994 to 2005, diarrheal pathogens had a trend of decrease especially Shigella spp. and Salmonella spp. Of the 6329 isolates of Shigella spp., 75.62% was S. flexneri and S. sonnei, S. dysenteriae and S. boydii constituted 23.98%, 0.22% and 0.01% respectively. The sensitivity of different species, group or serotype to different antimicrobial agents was not the same. S. flexneri and Aeromonas spp. were highly resistant to most of antibiotics. However, S. sonnei and Vibrio spp. had good susceptibility to antibiotics tested except trimethoprim/sulfamethoxazole and ampicillin. CONCLUSION: There are many species and serotypes of enteric pathogenic bacteria causing infective diarrhea and the distribution changes gradually in Beijing. The resistance rate of enteric pathogenic bacteria to antibiotics is not the same in different species and serotypes, so strict surveillance is always needed.

[Detection of multiresistance Aeromonas with TEM type resistant genes in patients with cirrhosis].

OBJECTIVE: To study the status of beta-lactamase produced by multiresistant Aeromonas selected from cirrhosis patients to provide reference for treatment and reduce resistance and control spreading. METHODS: Four multiresistant Aeromonas strains isolated from serious liver cirrhosis patients from the No. 302 hospital. The TEM resistant genes were detected by PCR and agarose gel electrophoresis. RESULTS: Three TEM-1 positive strains were detected from four multiresistant Aeromonas isolates consisting of one Aeromonas sobria and three Aeromonas hydrophila isolated from blood and ascites. This was further confirmed by gene sequencing. The multiresistance to antibiotics was higher in four Aeromonas isolates. All strains tested were resistant to ampicillin, cefazolin and cefmetazole.The cirrhosis patients who suffered from Aeromonas infection had poor prognosis and had mortality rate of 3/4. CONCLUSION: The beta-lactamase TEM-1 resistant genes was detected in clinical multiresistant Aeromonas strain isolated from serious cirrhosis patients.The results suggested that TEM-1 was the main resistance mechanism of Aeromonas strain and was reduced by adding enzyme inhibitor.

[The clinical features and prognosis of Aeromonas septicaemia in hepatic cirrhosis: a report of 50 cases].

OBJECTIVE: Aeromonas septicaemia complicating cirrhosis is not a common infectious disease. To enhance the knowledge in this aspect, we analysed the clinical features, pathogenetic factors, resistance, treatment and prognosis of Aeromonas septicaemia in 50 cases of hepatic cirrhosis. METHODS: We cultured the bacteria from infected patients with BacT/Alert120 automation instrument made in AKsu and identified the bacteria with the Vitek-AMS60 made in Biomerieux company. We then tested the susceptibility of Aeromonas to 13 antimicrobial agents. RESULTS: A total of 50 cases of Aeromonas septicaemia occurred in severe hepatic cirrhosis. The majority of them had severe complications. Aeromonas hydrophila was the most common species isolated (52.0%). Nosocomial infection was the predominant way of infection. The major clinical manifestations of Aeromonas septicaemia were fever (100%), chill (64.0%), abdominal pain (60.0%), diarrhoea (32.0%) and shock (24.0%). The susceptive rate of Aeromonas to third generation cephalosporin, quinolones and aminoglycoside antibiotics was more than 80%. The cure rate and mortality attributed to Aeromonas septicaemia after treating with third generation cephalosporin, levofloxacin and their combination were 64.3%, 75.0%, 57.1% and 28.6%, 12.5%, 35.7% respectively. CONCLUSION: Aeromonas septicaemia tends to befall patients with severe hepatic cirrhosis and causes a rapidly fatal outcome. Aeromonas should be considered an important pathogen for septicemia in patients with liver cirrhosis. It is suggested that we should emphasize the clinical features and laboratory diagnosis so as to have proper antimicrobial treatment.