Epidemiology and risk factors for community-acquired blood stream infection caused by extended spectrum β-lactamases-producing Escherichia coli and Klebsiella pneumonia strains
Objective 
To investigate the incidences, risk factors, genotypes and epidemiology of community-acquired blood stream infection caused by extended spectrum β-lactamases (ESBLs)-producing Escherichia coli and Klebsiella pneumonia strains and to analyze the sensitivity of those ESBLs producing strains to commonly used antibiotics. 
 
 
Methods 
Forty-two patients who were diagnosed with community-acquired blood stream infection caused by Escherichia coli or Klebsiella pneumonia strains in Sichuan Provincial People's Hospital were recruited in this study. Disc diffusion method was used for the phenotypic confirmatory test of ESBLs. Agar dilution method was performed to measure the antimicrobial susceptibility of the ESBLs-producing strains to 13 clinically commonly used antibiotics. Genotypes of the ESBLs-producing strains were identified by polymerase chain reaction (PCR). Multilocus sequence typing (MLST) was used to analyze the epidemiology of ESBLs-producing strains. Logistic regression analysis was performed to analyze the risk factors for community-acquired blood stream infection. 
 
 
Results 
The ESBLs-producing Escherichia coli strains accounted for 56.3% (18/32) and the ESBLs-producing Klebsiella pneumoniae strains accounted for 20% (2/10). All of the 20 ESBLs-producing strains were sensitive to imipenem, meropenem, ertapenem, nitrofurantoin and moxalactam. The ESBLs-producing strains sensitive to amikacin, piperacillin-tazobactam and fosfomycin accounted for 95%, 90% and 85%, respectively. Drug resistance rates of the 20 strains to cefotaxime, levofloxacin, ciprofloxacin and cefepime were relatively high accounting for 100%, 80%, 80% and 75%, respectively. Among the 20 ESBLs-producing strains, 7 strains only carried the CTM gene, while the other 13 strains were all positive for two genotypes of ESBLs, mainly identified as TEM+ CTM-M-14 and TEM+ CTM-15 genotypes. The 18 Escherichia coli strains were classified into 10 ST types, most of which were ST131 type, followed by ST10 and ST38 types. This study indicated that malignant tumor might be a possible risk factor. 
 
 
Conclusion 
The prevalence of community-acquired blood stream infection caused by ESBLs-producing Escherichia coli strains was becoming increasingly serious. Malignant tumor might be the risk factor associated with the producing of ESBLs in Escherichia coli and Klebsiella pneumonia strains. TEM+ CTX-M-14 was the predominant genotype of ESBLs-producing strains and the prevalent clone was ST131 type. Carbapenems and enzyme inhibitor compounds were ideal drugs for the treatment of community-acquired blood stream infection caused by ESBLs-producing Escherichia coli and Klebsiella pneumonia strains. This study was limited by the small sample size. Therefore, it is necessary to conduct further researches based on a large number of samples. 
 
 
Key words: 
Community-acquired blood stream infection; Extended spectrum β-lactamases; Escherichia coli; Klebsiella pneumoniae; Risk factor