Research on pathogenic bacteria and antibiotic resistance of Enterobacteriaceae in hospitalized elderly patients
Feng Zheng* and Xiang-zhu Meng
Department of Infectious Disease, Qilu Hospital of Shandong University, Jinan, PR China
- *Corresponding Author:
- Feng Zheng
Department of Infectious Disease
Qilu Hospital of Shandong University, PR China
Accepted on July 26, 2017
Objective: To observe the pathogens types of Enterobacteriaceae infection in hospitalized elderly patients, and analyse its drug resistance of germ and provide laboratory evidence for clinical prevention and treatment in the future.
Methods: The clinical data of hospitalized elderly patients (≥ 60 y) from July, 2009 to June, 2017 were retrospectively analysed, identification of the strain was conducted after using conventional methods for separation of Enterobacteriaceae, and the disk diffusion method (K-B) was adopted for detecting the drug resistance of bacteria to various antimicrobial agents.
Results: In this study, 3541 cases were confirmed with the occurrence of hospital infection from Enterobacteriaceae, and 2338 strains of Enterobacteriaceae were isolated, of which 771 strains of Escherichia coli (32.98%), 682 strains of Klebsiella (29.17%) with the highest relevance ratio. The drug resistance rates of Escherichia coli to sulfamethoxazole were the highest (98.57%) and that of Klebsiella pneumoniae reached 82.99%. They were followed by ciprofloxacin and levofloxacin. The drug resistance rates of Escherichia coli to ciprofloxacin and levofloxacin were higher than Klebsiella pneumoniae (p<0.05). In every sample, the drug resistance rates of sulfamethoxazole, ciprofloxacin and levofloxacin were relatively high. The drug resistance of cefotaxime and piperacillin in the drainage liquid samples were higher than other, but that of sulfamethoxazole was lower than the urine samples (p<0.05). The drug resistance of levofloxacin, imipenem, meropenem and sulfamethoxazole in the sputum sample were lower than urine samples (p<0.05).
Conclusion: The Enterobacteriaceae bacteria produce the drug resistance to many antibiotics, which affects the treatment effect of hospitalized elderly patients. The antibacterial agents should be properly used and the distribution condition of pathogenic bacteria and drug resistance of patients should be closely monitored.
Elderly, Enterobacteriaceae, Bacterial infections, Pathogens, Drug resistance.
At present, with the infection degree of hospital pathogens continuing to expand, the effective pathogen prevention and control has become the main task for clinicians. Due to clinicians’ and patients’ irrational use of broad-spectrum antibiotics, the drug resistance of most pathogenic bacteria are increasing . So the control of intestinal bacteria is very important. Because of physical function constant decline and resistance reduction of elderly patients who are suffering from a variety of illness and are more susceptible to infection and do not have a good respond to treatment with long time of hospitalization, so the control of bacterial infections in hospitalized elderly patients is more important [2-4]. Therefore, the pathogenic bacteria and drug resistance of hospitalized elderly patients with Enterobacteriaceae infection in our hospital were studied in this research and the drug resistance rate was reduced as possible for clinical rational drug use, in order to provide the basis for improving the clinical cure rate and survival rate in the future. The current study report is shown as follows.
Data and Methods
The hospitalized elderly patients (≥ 60 y old in our hospital from July, 2009 to June, 2017 were included in the study for retrospective analysis according to ‘the diagnostic criteria for hospital infection’ formulated by the National Health Planning Commission  combined with medical history, symptoms, signs and imaging examination report and medical examination reports. In these cases, 541 were confirmed for occurrence of Escherichia coli hospital bacterial infection, whose inspection samples came from infection samples of elderly hospitalized patients, of which there were 876 copies of urine, 813 of sputum samples, 642 of drainage samples, 589 of secretions samples, 304 cases of pus samples, 317 cases of others. After excluding isolated strains from the same parts of patients where he agreed (agreed strains collected in 7 d, which were not repeatedly included in the statistics), and through VITEK2 compact automatic microbial analysis system (provided by the BioMerieux company in Lyons, France), 2338 strains of Enterobacteriaceae were isolated and collected. The study and patients or their relatives signed informed consent form.
In this study, the antibacterial drug disk were purchased from Thermo Fisher biochemical products (Beijing) company, MH medium was purchased from the British company OXOID, as well as ceftazidime clavulanic acid, cefotaxime clavulanic acid and nitrocefin disk from OXOID goods, which were 30 μg/ piece. Disposable medical supplies were purchased from Beijing Hua Rui Bo Yang Technology Co. Ltd. All products were qualified to enter the indoor quality control before becoming clinical specimens.
Bacterial culture and isolation
In this study, the isolated 2338 strains were cultured by the microbiological inspection technology in the national clinical laboratory operation procedures. The collected strains were inoculated in the culture dish and cultured for 18-24 h in 35°C for their recovery. After the single bacterial colony was obtained, all the Escherichia coli were further evaluated using automatic VITEK2 microorganism identification drug sensitivity instrument according to gram stain, bacteria form. All the specimens were cultured by the same group of personnel, and cultured samples were transported and identified by certain person.
Strain identification and drug susceptibility test
In this study, the cultured strains were identified by VITEK2 compact automatic microbial analysis system, and relative inspection standard and operation specification M02-A11: ‘standard for antimicrobial susceptibility testing operating procedures’ (disk method) were used for preliminary screening and phenotypic confirmatory test. The bacteria liquid of 0.5 Maxwell was formulated using sterile normal saline and uniformly coated on the M-C agarose surface with 4% NaCl. The drug sensitivity paper pieces of amoxicillin, amikacin, ceftazidime, cefotaxime, cefepime, ciprofloxacin, levofloxacin, imipenem, meropenem, ertapenem, sulfamethoxazole, gentamicin, sulbactam, piperacillin were put on the M-H agar surface and incubated for 24 h in the constant temperature water incubator in 35°C using paper separator. The bacterial inhibition diameters were respectively detected.
Quality control strains
In this study, Escherichia coli (ATCC25922) and Klebsiella pneumoniae (ATCC 700603) were selected as the quality control strains, all of which were derived from the clinical laboratory center of the Ministry of health. The standard strains (ATCC25922 and ATCC 700603) using antibacterial drug paper every week were detected and their results were within the interpretation range specified by CLSI.
Statistical data analysis
All the data were input into Excel spread sheet for statistical analysis by using SPSS18.0 statistical software for data processing. The χ2 test was used for count data, and P<0.05 meant the difference was statistically significant. Drug resistance test results were analysed by WHONET 5.6 software.
In this study, 3541 cases were confirmed with the occurrence of hospital infection from Enterobacteriaceae, and 2338 strains of Enterobacteriaceae were isolated, of which 771 strains of Escherichia coli (32.98%) , 682 strains of Klebsiella pneumoniae (29.17%) with the highest detection rate, 465 strains of Enterobacter spp. (19.89%), 249 strains of Klebsiella oxytoca (10.65%), and other 171 strains (7.31%) were detected. The results are shown in Table 1.
|Pathogenic bacteria||Number (stain)||Constituent ratio (%)|
Table 1. Distribution of pathogenic bacteria.
In this study, samples infected by Enterobacteriaceae bacterial included 587 urine samples (25.11%), 423 sputum samples (18.09%), 396 drainage samples (16.94%), 369 secretions samples (15.78%), 295 pus samples (12.62%) and 268 other samples (11.46%) (Table 2).
|Specimen||Number (stain)||Constituent ratio (%)|
Table 2. The distribution and composition of bacterial specimens (%).
Detection rate of drug-resistant bacteria
In this study, 771 strains of Escherichia coli were detected in 2338 strains of Enterobacteriaceae, and 682 strains of Klebsiella pneumoniae were detected. Drug resistance analysis on the quality control index of Escherichia coli and Klebsiella pneumoniae was conducted and the results showed that the drug resistance rate of Escherichia coli to sulfamethoxazole was the highest upto 98.57% and that of Klebsiella pneumoniae was 82.99%, followed by ciprofloxacin and levofloxacin with respective 85.08% and 80.42% resistant rates of Escherichia coli, which were higher than Klebsiella pneumoniae (66.86%, 50.0%). There was statistic difference (p<0.05). Then gentamicin, cefotaxime, cefepime, ceftazidime amoxicillin appeared. And the resistance rates of other drugs with higher sensitivity such as Amikacin, piperacillin and sulbactam were all <25%. The detection results of Klebsiella pneumoniae were similar to that of Escherichia coli. But drug resistance rates of cefotaxime, cefepime, ciprofloxacin, levofloxacin were lower than Escherichia coli and there was statistic difference (p<0.05) (Table 3).
|Antimicrobial agents||Escherichia coli (n=771)||Klebsiella pneumoniae (n=682)|
|Number||Resistance rate||Number||Resistance rate|
Note: a was compared with Escherichia coli, p<0.05;
Table 3. Drug resistance (%) of major intestinal bacteria.
Analysis of drug resistance rate in different samples
In the clinical study, the resistance rates of Escherichia coli to common drugs in 3541 samples were analysed, and the results showed that, in urine samples, the resistance rates of sulfamethoxazole, ciprofloxacin and levofloxacin were higher, the resistance rates of amikacin, piperacillin and sulbactam were relatively lower. The trends of drug resistance in sputum, drainage, secretion, pus and other samples were similar. Additionally, the drug resistance rates of cefotaxime and piperacillin in the drainage liquid samples were higher than other samples. But that of Sulfamethoxazole was lower than urine samples and there was statistic difference (p<0.05). The drug resistance rates of levofloxacin, imipenem, meropenem and Sulfamethoxazole were lower than urine samples and there was statistic difference (p<0.05) (Table 4).
|Antimicrobial agents||Urine (n=587)||Sputum sample (n=423)||Drainage sample (n=396)||Secretion sample (n=369)||Pus sample (n=295)||Others (n=268)|
|Amoxicillin||66 (11.24)||28 (6.62)||19 (4.80)||58 (15.72)||33 (11.19)||32 (11.94)|
|Amikacin||37 (6.30)||27 (6.38)||29 (7.32)||47 (12.74)||9 (3.05)||21 (7.84)|
|Ceftazidime||18 (3.07)||9 (2.13)e||0 (0.00%)e||79 (21.41)b||0 (0.00%)e||4 (1.49)e|
|Cefotaxime||46 (7.84)||63 (14.89)||116 (29.29)||0 (0.00%)cd||26 (8.81)d||5 (1.87)d|
|Cefepime||28 (4.77)||26 (6.15)||18 (4.55)||1 (2.71)||8 (2.71)||13 (4.85)|
|Ciprofloxacin||39 (6.64)||26 (6.15)||0 (0.00%)||0 (0.00%)||24 (8.14)||0 (0.00%)|
|Levofloxacin||85 (14.48)||8 (1.89)b||30 (7.56)||0 (0.00%)bg||32 (10.85)||33 (12.31)|
|Imipenem||9 (1.53)||46 (10.87)||8 (2.02)||19 (5.15)||0 (0.00%)c||0 (0.00%)c|
|Meropenem||17 (2.090)||75 (17.73)||3 (7.83)||19 (5.15)||26 (8.81)||26 (9.70)|
|Ertapenem||18 (3.07)||21 (4.96)||9 (2.27)||28 (7.59)||32 (10.85)||41 (15.30)be|
|Sulfamethoxazole||117 (19.93)||29 (6.86)b||17 (4.29)b||7 (1.90)b||17 (5.76)b||8 (2.99)b|
|Gentamicin||9 (1.53)||18 (4.26)||16 (4.04)||16 (4.34)||6 (2.03)||0 (0.00%)|
|Sulbactam||84 (14.31)||47 (11.11)||38 (9.60)||18 (4.88)||29 (9.83)||30 (11.19)|
|Piperacillin||8 (1.36)||7 (2.65)||58 (14.65)bc||39 (10.57)||44 (14.92)bc||9 (3.36)|
Note: bwas compared with urine samples, p<0.05; cwas compared with drainage liquid samples, p<0.05; ewas compared with secretion samples, p<0.05; gwas compared with other samples, p<0.05.
Table 4. Analysis of drug resistance rate of Escherichia coli in different samples (n (%)).
Currently, because of irregular and unreasonable use of clinical antibacterial agents, the drug resistance of bacterial is increasing, which seriously affects the treatment effect of drug . In the study, the detection rate of enterobacteriaceae bacteria in elderly patients in our hospital was 66.03% accounting for a large proportion. Especially, Escherichia coli and Klebsiella pneumoniae were main detected stains with 32.98% and 29.17% of detection rate, which should be regarded as mainly focused bacterial infected and monitored by the hospital. Antibacterial agents play a very import role in use number, amount, variety and other aspects of our clinic and ward. They save life and health of many patients meanwhile promoting the production of “superbacteria”, which is mainly caused by abuse, misuse, joint use and irregular and unreasonable use of antibiotic . To this day, the drug resistance and study bottleneck of antibacterial agents have become one difficulty urgently needing to be solved, otherwise, which may form an awkward situation of “no medicine”.
In this study, the drug resistance rate of gram-negative bacterium Escherichia coli to sulfamethoxazole was the highest up to 82.99%, followed by ciprofloxacin and levofloxacin. The drug resistance rates of Escherichia coli to Ciprofloxacin and levofloxacin were higher than Klebsiella pneumoniae and there was statistic difference (p<0.05). Then gentamicin, cefotaxime, cefepime, amoxicillin, ceftazidime were followed. The drug resistance rates of other high sensitivity drugs (such as amikacin, piperacillin and sulbactam) were lower than 25%. The detection result of Klebsiella pneumoniae was similar to Escherichia coli. But the drug resistance rates to ceftazidime, cefotaxime, ciprofloxacin and levofloxacin were lower than Escherichia coli and there was statistic difference (p<0.05). We can see that we can select more reasonable treatment scheme by timely and correctly understanding pathogenic bacteria of elderly patients and drug resistance monitoring. The hyper spectrum β-lactamase (ESBLs) is one of important reasons that why gram-negative bacillus produces drug resistance to penicillin and cephalosporin [8,9]. Certain study shows that currently, the detection rate of the enzyme is increasing year by year . Once the bacteria produced the antibacterial ESBLs enzyme, they would almost be resistant to penicillins, cephalosporins, etc., and only sensitive to carbapenem antibiotics. Therefore, once the resistance to the drug appears, it will bring a new crisis to clinical treatment . It is worth noting that the United States has found the bacteria resistant to antibiotic carbapenem in 2001, and reports appeared in China in 2009 which showed antibacterial drugs resistant to carbapenems had gradually lost its advantage [12-14]. But it is worth mentioning that, in this study, we have not detected bacteria’s drug tolerance to carbapenem antibiotics such as imipenem, meropenem and ertapenem, the results of which was consistent with Xu  and other study results, so that this kind of drug can also be used for clinical promotion and replacement. The clinical study found that Enterobacteriaceae produced multiple drug resistance and cross resistance to quinolones and aminoglycoside, which may be related to irregular use of antibiotic, so that the corresponding laws should be formulated to curb this situation .
In summary, in the clinical research of antibacterial drugs, detection of bacterial resistance is an important way to observe the clinical rational use of drugs, the laboratory should establish a routine method to make timely detection of them, and make rational clinical guided medication by using the results from this study as well as control the spread of drug resistant strains. Thus, in clinical treatment, drug resistance of the pathogen plays a particularly important role in the course of treatment, and with the increase of antimicrobial resistance of common bacteria, the rational use of antimicrobial drugs is an important way to control bacterial infection and outbreak.
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