Epidemiology Of Enterobacteriaceae Causing Intestinal Colonization And Bloodstream Infections

Objective: To determine the prevalence, drug susceptibility and molecular epidemiology of extended-spectrum ?-lactamase-producing Enterobacteriaceae(ESBL-E) and to assess risk factors for fecal carriage of ESBL-E in resident, staff and facility levels among nursing home residents;To investigate the bacterial distribution and drug-resistance of pathogens causing bloodstream infections(BSI) in Ruijin Hospital in 2012 and then to analyze drug susceptibility and molecular epidemiology of Escherichia coli isolates causing BSI isolated from 2011 to 2013, providing the scientific evidence for nosocomial infection control and clinical therapy.Methods: 1) Build and evaluate CHROMagar orientation mediumin conjunction with simple biochemical tests including indole test, ornithine decarboxylase test and lysine decarboxylase test for identifying common oxidase-negative gram-negative bacilli with the results of Vitek-2 system as reference method; 2) Rectal swabs and NH records at the individual-resident level, staff level and facility level were collected, antimicrobial susceptibilitytesting was performed by disk diffusion, drug resistance genes coding for ESBLs and carbapenemases were detected by polymerase chain reaction(PCR), NH records at the individual-resident level and facility level were collected and examined for potential risk factors; 3) Collected records of blood samples from Jan 2012 to Dec 2012 from inpatients in Ruijin Hopital to identify characteristics of pathogens causing bloodstream infections; 4) E.coli isolates causing bloodstream infections were consecutively collected between June 2011 and June 2013 in Ruijin Hospital, antimicrobial susceptibility testing was performed by disk diffusion, drug resistance genes coding for extended-spectrum ?-lactamases(ESBLs) and carbapenemases,and phylogenetic groups were detected by polymerase chain reaction(PCR),e BURST was used for multi-locus sequence typing(MLST).Results: 1) The specificity of all bacteria was above 90% and the sensitivity of them was 75%~90%, the Kappa value of the study was above0.85 in addition to Citrobacter freundii whose Kappa value was just 0.5947.Mc Nemar test showed that p>0.05 in all bacteria. However,the cost was reduced by 90%; 2) 457 Enterobacteriacea isolates were collected among 7NHs of which 183(46.92%) were colonized by ESBL-E. Escherichia coli(365, 79.87%), Proteus mirabilis(40, 8.75%) and Klebsiella pneumoniae(24,5.25%) were the most common microorganisms. CTX-M enzymes(198,99.00%) predominated, with CTX-M-14(84, 42.00%), the most common types. Both carbapenemase producers harbored bla KPC-2. Resistance rates of ESBL-E isolates to Carbapenems, TZP, AK, FOS, CL and TGC were low.History of invasive procedures(OR=3.112, 95%CI 1.725-5.615, p=0.000),quinolones use(OR=1.808, 95%CI 1.047-3.121, p=0.034) and frequency of bathing weekly(OR=1.959, 95%CI 1.163-3.302, p=0.012) were independently associated with ESBL-E fecal carriage; 3) From Jan 2012 to Dec 2012, there were 17630 samples in Ruijin Hospital, including 16428 samples from inpatients,there were 5546 episodes and 384 were positive(6.92%). There were 272(68.34%) Gram-negative bacteria, 94(23.62%)Gram-positive bacteria and 32(8.04%) fungi; The strains isolated from middle aged and elderly people mostly and the most frequent depatments were Department of Burn, Department of Chinese Medicine, Cardiac Intensive Care Unit, Transplant Department and department of traumatology;Gram positive cocci were highly susceptible to vancomycin, linezolid and teicomycin and there was one Enterococcus Faecium resistant to vancomycin;Gram negative bacilli were highly susceptible to amikacin and carbapenems;the drug resistance rates of Enterobacteriaceae, Acinetobacter baumannii and Pseudomonas aeruginosa to carbapenems were 7.51%, 70.97% and 35.90%;4) From Jun 2011 to Jun 2013, 128 strains causing BSI in Ruijin Hospital were collected of which 80 produced ESBLs. No carbapenem-resistant isolates were found. The resistance rates to penicillins, fluoroquinolone,folate pathway inhibitors, tetracyclines and second-generation cephalosporins were high. Molecular analysis showed that CTX-M-14(40/80) was the most common ?-lactamase, followed by CTX-M-55(17/80) and CTX-M-15(14/80). Phylogenetic group B2 predominated(37.5%), but phylogenetic group D exhibited the highest rates of ESBL production. ST131(17/128) was the most common sequence type, followed by ST69(12/128) and ST648(10/128).Conclusions: 1) The cost-effective algorithm of using CHROMagar Orientation mediumin conjunction with simple biochemical tests would efficiently identify common oxidase-negtive gram-negative bacilli; 2)History of invasive procedures, quinolones use and frequency of bathing weekly were independently associated with ESBL-E fecal carriage and continuous and active surveillance is important, as are prudent infection-control measures and antibiotic use to prevent and control the spread of these antibiotic-resistant strains in NH residents; 3) Gram negative bacteria were the main pathogens isolated from blood in our hospital and they were mostly from middle aged and elderly people; Genetic diversity showed no correlation to the nosocomial origin of the isolates; 4) Prevalence and antimicrobial resistance rate were high in both hospital and NH ESBL-E isolates, but those of NH isolates were higher; However, TZP,AK, FOS, CL, TGC and Carbapenems could be optimistic options for the empiric therapy; CTX-M-14, CTX-M-15 and CTX-M-55 were the most common ?-lactamases.