Diagnosis and treatment of community-acquired pneumonia in adults: 2016 clinical practice guidelines by the Chinese Thoracic Society, Chinese Medical Association.

Community-acquired pneumonia (CAP) in adults is an infectious disease with high morbidity in China and the rest of the world. With the changing pattern in the etiological profile of CAP and advances in medical techniques in diagnosis and treatment over time, Chinese Thoracic Society of Chinese Medical Association updated its CAP guideline in 2016 to address the standard management of CAP in Chinese adults. Extensive and comprehensive literature search was made to collect the data and evidence for experts to review and evaluate the level of evidence. Corresponding recommendations are provided appropriately based on the level of evidence. This updated guideline covers comprehensive topics on CAP, including aetiology, antimicrobial resistance profile, diagnosis, empirical and targeted treatments, adjunctive and supportive therapies, as well as prophylaxis. The recommendations may help clinicians manage CAP patients more effectively and efficiently. CAP in pediatric patients and immunocompromised adults is beyond the scope of this guideline. This guideline is only applicable for the immunocompetent CAP patients aged 18 years and older. The recommendations on selection of antimicrobial agents and the dosing regimens are not mandatory. The clinicians are recommended to prescribe and adjust antimicrobial therapies primarily based on their local etiological profile and results of susceptibility testing, with reference to this guideline.

Macrolide-resistant Mycoplasma pneumoniae prevalence and clinical aspects in adult patients with community-acquired pneumonia in China: a prospective multicenter surveillance study.

BACKGROUND: Drug resistant Mycoplasma pneumoniae (MP) is a rising issue in the management of community-acquired pneumonia (CAP). Epidemiological monitoring is essential for identifying resistant patterns of MP isolates against various antibiotics in adult CAP patients. METHODS: This is a prospectively designed multicenter study conducted on adult patients with CAP visiting six teaching hospitals in the cities of Beijing, Shanghai and Guangzhou between September 2010 and June 2012. RESULTS: A total of 520 adult patients (mean age: 45.7±26.2 years) with CAP visiting teaching hospitals in the cities of Beijing, Shanghai and Guangzhou were included. Of the 520 patients, only 75 (14.42%) were confirmed MP positive by means of culture and real-time PCR methods. Quinolones were the most common initially prescribed antimicrobial, followed by ß-lactams and ß-lactams plus quinolones. Macrolide resistance was as high as 80% and 72% against erythromycin (ERY) and azithromycin (AZM) respectively, which were associated with the A2063G transition mutation in domain V of the 23S ribosomal RNA (rRNA) gene. Six strains with mild to moderate ERY-resistant level were still susceptible to AZM. Tetracycline (TET), minocycline (MIN) and quinolones [moxifloxacin (MOX) and fluoroquinolones] had no signs of resistance. CONCLUSIONS: High resistance was observed with macrolides, whereas, none of the MP strains were resistant to fluoroquinolones and TET. Hence, macrolide resistant MP (MRMP)_infections could be well treated with fluoroquinolones. However, few isolated strains had minimal inhibitory concentration (MIC) values on the edge of resistance to quinolones, alarming a quinolone-resistant MP in the near future.

Healthcare-associated Pneumonia: Clinical Features and Retrospective Analysis Over 10 Years.

BACKGROUND: Healthcare-associated pneumonia (HCAP) is associated with drug-resistant pathogens and high mortality, and there is no clear evidence that this is due to inappropriate antibiotic therapy. This study was to elucidate the clinical features, pathogens, therapy, and outcomes of HCAP, and to clarify the risk factors for drug-resistant pathogens and prognosis. METHODS: Retrospective observational study among hospitalized patients with HCAP over 10 years. The primary outcome was 30-day all-cause hospital mortality after admission. Demographics (age, gender, clinical features, and comorbidities), dates of admission, discharge and/or death, hospitalization costs, microbiological results, chest imaging studies, and CURB-65 were analyzed. Antibiotics, admission to Intensive Care Unit (ICU), mechanical ventilation, and pneumonia prognosis were recorded. Patients were dichotomized based on CURB-65 (low- vs. high-risk). RESULTS: Among 612 patients (mean age of 70.7 years), 88.4% had at least one comorbidity. Commonly detected pathogens were Acinetobacter baumannii, Pseudomonas aeruginosa, and coagulase-negative staphylococci. Initial monotherapy with ß-lactam antibiotics was the most common initial therapy (50%). Mean age, length of stay, hospitalization expenses, ICU admission, mechanical ventilation use, malignancies, and detection rate for P. aeruginosa, and Staphylococcus aureus were higher in the high-risk group compared with the low-risk group. CURB-65 ≥3, malignancies, and mechanical ventilation were associated with an increased mortality. Logistic regression analysis showed that cerebrovascular diseases and being bedridden were independent risk factors for HCAP. CONCLUSION: Initial treatment of HCAP with broad-spectrum antibiotics could be an appropriate approach. CURB-65 ≥3, malignancies, and mechanical ventilation may result in an increased mortality.

Immediate and long-term results of bronchial artery embolization for hemoptysis due to benign versus malignant pulmonary diseases.

BACKGROUND: Bronchial artery embolization (BAE) is widely used for the treatment of hemoptysis. The immediate and long-term results of BAE for hemoptysis in patients with benign and malignant pulmonary diseases were inconsistent in previous studies and were thus investigated. METHODS: This was a retrospective review of the clinical records of 154 patients (108 with benign disease and 46 with malignant disease) who received BAE for hemoptysis from January 2005 to June 2011 at the Chinese People's Liberation Army General Hospital. RESULTS: Immediate cessation of hemoptysis was achieved in 98 patients with benign disease (90.7%) and 42 patients with malignancy (91.3%). The long-term control rate of hemoptysis in patients with benign disease was 74.3% (80/108) at 1 year, significantly higher than in patients with cancer (16/46, 35.5%, P < 0.01). The worst outcomes in the benign and malignant groups were observed in patients with aspergilloma and squamous cell lung cancer, respectively. The average number of abnormal vessels on bronchial arteriography was higher in the benign group than in the malignant group (3 ± 1.3 versus 2 ± 1.1, respectively, P < 0.01). Moreover, recurrent hemoptysis was independently associated with the presence of massive hemoptysis and bronchial-pulmonary artery shunt in both groups (P < 0.05). CONCLUSIONS: BAE is a relatively safe procedure for patients with hemoptysis. Immediate control of hemoptysis with BAE is achieved in most cases, but the long-term hemoptysis control rate is worse in malignant lung diseases than in benign conditions, especially among patients with squamous cell lung cancer.

[Assessment of prognostic and influencing factors in elderly patients with multiple organ dysfunction syndrome].

OBJECTIVE: To preliminarily assess the prognosis of patients with multiple organ dysfunction syndrome (MODSE) and analyze their influencing factors. METHODS: The clinical data of 365 MODSE patients admitted into Chinese PLA General Hospital during January 2009 to June 2012 were analyzed retrospectively. According to 28-day outcomes, they were divided into 2 groups (28-day survival and non-survival) while 4 groups according to age. Then these prognosis were evaluated with the current scoring systems ((acute physiology and chronic health evaluation II (APACHEII and III), sample acute physiological score (SAPSII) and multiple organ dysfunction score (MODS)). The predictive powers were compared by receiver operating characteristic (ROC) curve. Finally a binary Logistic regression analysis was performed to evaluate the relevant influencing prognostic factors of MODSE. RESULTS: The mean age was (77.8 ± 9.1) years, mean number of failed organs (3.6 ± 1.2) and a 28-day mortality 45.8%. The ages of non-survival group were older than those of survival group ((78.1 ± 9.1) vs (76.7 ± 11.0) years). The number of organ failures ((4.3 ± 1.1) vs (3.1 ± 1.0)) and scores (APACHEII: (28 ± 7) vs (20 ± 8), APACHE III: (106 ± 27) vs (75 ± 31), SAPSII: (64 ± 16) vs (46 ± 18), MODS: (9 ± 3) vs (6 ± 3)) of non-survivals were significantly higher than that of survivals. The area under ROC curve of these four score systems were 0.790, 0.781, 0.780 and 0.780 respectively. Compared to the above systems, SAPSII had the best performance in sensitivity while APACHEII was more valuable in specificity. All clinical data underwent binary Logistic regression and the results showed that plasma concentration of albumin and mean arterial pressure (MAP) offered beneficial outcomes while age and number of organ failures had unfavorable prognosis. The greater patient age, the higher their mortality. CONCLUSIONS: All four scoring systems have accurate prognostic predictions of MODSE patients. And the predictive power of APACHEII is the best. Plasma concentration of albumin, MAP, age and organ failure number are independent prognostic factors in MODSE patients.

[A clinical analysis of 7 cases of allergic bronchopulmonary aspergillosis].

OBJECTIVE: To study the clinical features, diagnosis and treatment of allergic bronchopulmonary aspergillosis (ABPA). METHODS: The clinical presentations, serologic results, chest radiology, pathological results and treatment of 7 patients with ABPA in Chinese PLA General Hospital were retrospectively analyzed. RESULTS: There were 4 males and 3 females, with a mean age of (33 ± 16) years. Before the diagnosis of ABPA, 6 cases had been misdiagnosed as bronchial asthma, 3 as pulmonary infection, 2 as tuberculosis and 1 as bronchiectasis. The main clinical manifestations included cough (n = 6), sputum production (n = 5), hemoptysis (n = 4), wheeze (n = 3), dyspnea(n = 3) and fever(n = 2). All cases had increased total serum IgE levels (median 3040 U/ml) and peripheral blood eosinophil count (median 0.19). Six of them showed increased peripheral eosinophil count median 1.84 × 10(9)/L, and skin test positive for Aspergillus antigen. Five of them had increased serum IgE antibodies specific to A. fumigatus (22 ± 15) kU/L, and 4 had increased serum IgG antibodies specific to A. fumigatus (108 ± 96) mg/L. The chest CT scan findings included transient or fixed pulmonary opacities, central bronchiectasis and finger-in-glove opacities. Five patients were treated with corticosteroids combined with antifungal therapy. CONCLUSIONS: Clinical features of ABPA include a history of asthma, elevation of the total serum IgE levels, presence of aspergillus IgE antibodies, peripheral eosinophilia, and transient or fixed pulmonary opacities and central bronchiectasis. Patients with asthma complicated with bronchiectasis should be routinely screened for Aspergillus skin test, and measurement of total serum IgE levels and chest CT scan are useful for confirmation of the diagnosis of ABPA. Oral glucocorticoids and anti-fungal drugs are effective in treatment of ABPA. Regular follow-up is needed for prevention of recurrence.

[Adult hospital acquired pneumonia: a multicenter study on microbiology and clinical characteristics of patients from 9 Chinese cities].

OBJECTIVE: To investigate the etiology and clinical characteristics of hospital-acquired pneumonia (HAP) in China and to provide evidence for appropriate therapy. METHODS: We performed a prospective multicenter study in 13 Chinese urban tertiary hospitals. All HAP cases diagnosed at respiratory general ward and respiratory intensive care unit (RICU) from August 2008 to December 2010 were studied. Epidemiological data, etiology and clinical characteristics of enrolled patients were collected. Sputum or tracheal aspirate and blood cultures, Legionella antibodies and Streptococcus pneumoniae urinary antigen tests were performed. Bacteria to antimicrobial susceptibility test was performed. RESULTS: A total of 610 cases of HAP were diagnosed during the study, with an overall incidence of 1.4% among 42 877 hospitalized patients, while the incidence was 0.9% (362/41 261) in respiratory general ward and 15.4% (248/1616) in RICU. 93.9% (573 cases) of patients had at least one underlying disease, and 91.0% (555 cases) had exposure to at least one antimicrobial agent within 90 days prior to HAP diagnosis. Pathogens were identified in 487 patients, with Acinetobacter baumannii [30.0% (183/610)], Pseudomonas aeruginosa [22.0% (134/610)], Staphylococcus aureus [13.4% (82/610)] and Klebsiella pneumonia [9.7% (59/610)] being the most common pathogens. Eighteen patients (3.0%) had infection with fastidious bacteria. A. baumannii and S. aureus were the more frequent pathogens in the ventilator-associated pneumonia (VAP) cases [50.5% (97/192) and 21.4% (41/192)] as compared to non-VAP cases [20.6% (86/418) and 9.8% (41/418), P < 0.01]. A. baumannii and S. aureus were also frequent pathogens in cases with a score of more than 20 by the acute physiology and chronic health evaluation II (APACHEII) scoring [45.7% (69/151) and 20.5% (31/151)], as compared to cases with a score of less than 20 of APACHE II [24.8% (114/459) and 11.1% (51/459), P < 0.01]. A. baumannii showed high resistance rates to carbapenems [more than 70% (109/142)], and the susceptibility to cefoperazone/sulbactam, polymyxin B and tigecycline were 40.8% (58/142), 99.3% (141/142) and 95.8% (136/142) respectively. Resistance rates of P. aeruginosa to meropenem and imipenem were 48.8% (40/82) and 70.7% (58/82) respectively. Methicillin-resistant S. aureus (MRSA) accounted for 87.8% (43/49) in all strains of S. aureus. Mortality rate of VAP cases was 34.5% (61/177), significantly more than that of HAP patients [22.3% (135/605), P < 0.05]. The average hospital stay of patients with HAP was (23.8 ± 20.5) days, significantly more than that of the average for inpatients [(13.2 ± 13.6) days, P < 0.01] during the study period. Mean costs of HAP were (108 950 ± 116 608) yuan, significantly higher than the average hospital costs of respiratory inpatients (17 999 ± 33 364) yuan. CONCLUSIONS: Among Chinese patients hospitalized in urban tertiary medical centers, HAP incidence and mortality rate were high, which increased the patients' hospital stay and the medical costs. Common pathogens were A. baumannii, P. aeruginosa, S. aureus and K. pneumonia. The common bacteria of HAP in China showed high resistance rates to antibiotics.

A clinical study on the effects and mechanism of xuebijing injection in severe pneumonia patients.

OBJECTIVE: To observe the effects of Xuebijing Injection in patients with severe pneumonia, and to explore the mechanism. METHODS: Eighty cases of severe pneumonia are randomly assigned to the Xuebijing treatment (forty cases) and the control group (forty cases), with the same routine therapy provided in both groups. Clinical effective rates, inflammatory factors and organ function were observed in both groups. RESULTS: The effective rate was higher in Xuebijing group than that of the control group (80.0% vs. 67.5%, P < 0.05). As compared with the control group, the LDH, alpha1-AG, alpha1-AT levels and the peak body temperature decreased markedly with the Xuebijing treatment going, and the secretion of TNF-alpha, IL-6, IL-8 was suppressed in Xuebijing group; but no significant difference was found in leptin level. CONCLUSION: Xuebijing Injection may show a protective effect in patients with severe pneumonia. The mechanism is possibly with the decreased secretion of TNF-alpha, IL-6, and IL-8.

[A multicentre retrospective study of pulmonary mycosis clinically proven from 1998 to 2007].

OBJECTIVE: To investigate the pathogens, clinical manifestations, prognosis of and the risk factors for pulmonary mycosis in China. METHODS: All cases of pulmonary mycosis from 16 centers in 10 cities from Jan. 1998 to Dec. 2007 that met the diagnostic criteria were included for clinical, microbiological and radiological analysis. RESULTS: Totally 474 cases of pulmonary mycosis were retrieved. The top 5 pulmonary mycosis was pulmonary aspergillosis (180 cases, 37.9%), pulmonary candidiasis (162 cases, 34.2%), pulmonary cryptococcosis (74 cases, 15.6%), pneumocystis carinii pneumonia (23 cases, 4.8%) and pulmonary mucormycosis (10 cases, 2.1%). The constituent ratio in the last 3 years was similar to that in the former 7 years. The main pathogens of pulmonary candidiasis were Candida albicans (308/474, 65.0%) and Candida tropicalis (57/474, 12.0%), which were sensitive to common azoles. Compared with bacterial pneumonia, pulmonary mycosis showed more symptoms of hemoptysis (147/474, 31.0%) and pleural effusion (95/474, 20.0%), and less radiological specificity. Classical halo sign (4/474, 0.8%) and crescentic sign (17/474, 3.6%) were only shown in several cases of pulmonary mycosis. The most common underlying diseases were tumor (including solid tumor and malignant hematological diseases) (94/474, 19.8%), chronic obstructive pulmonary disease (52/474, 11.0%), pulmonary tuberculosis (50/474, 10.5%) and diabetes (48/474, 10.1%). Compared with the other common pulmonary mycosis, pulmonary cryptococcosis affected younger patients, and more cases were community-acquired, but fewer cases with underlining diseases or compromised immune function, and had a better prognosis. CONCLUSION: The ahead five species of pulmonary mycosis in China were orderly pulmonary aspergillosis, pulmonary candidosis, pulmonary cryptococcosis, pneumocystis carinii pneumonia and pulmonary mucormycosis. The main pathogens of pulmonary candidosis were Candida albicans and Candida tropicalis, which were sensitive to common azoles. Compared with the other common pulmonary mycosis, pulmonary cryptococcosis catch younger patients, had more community-acquired cases, and had better prognosis.

Blastomycosis in China: a case report and literature review.

Blastomycosis is a fungal disease that is endemic in parts of North America. It is very rare in China and also commonly misdiagnosed, often as cancer or other infectious diseases. The clinical profile of a case of disseminated blastomycosis with pulmonary changes and skin ulcers was described. He had been misdiagnosed with tuberculosis, after adequate therapy with a lipid formulation of amphotericin B, followed by itraconazole, the lung and skin lesions improved. Then the five cases reported in China and literatures were reviewed. The aim of this report was to improve the knowledge regarding blastomycosis for physicians in China to avoid delaying adequate therapy.

[Antimicrobial resistance and genotyping of Acinetobacter baumannii in ICU].

OBJECTIVE: To investigate the outbreak of acinetobacter baumannii in the ICU, and to explore the antimicrobial resistance characteristics of pathogens, and therefore to determine the optimal prevention strategies. METHODS: From May to June 2007, most of the cases of infection by acinetobacter baumannii in our ICU were collected. PFGE (pulsed field gel electrophoresis) and standard disk diffusion susceptibility tests were performed on the strains isolated from the patients' body fluids including sputum, blood, urine, secretion and from the ICU environment involving the patients' bed sheet, skin surface and medical staff's hands, humidification water of ventilator tubes. RESULTS: Twelve strains were resistant to imipenem and meropenem. Colistin sulphate and tigecycline showed a high rate of antimicrobial activity against the strains, the rate of susceptibility being 100% and 91.7% respectively. These strains belonged to 3 clones (clone A, B, C) and there were 2 sub-clones (A1, A2) belonging to clone A. The sub-clone A1 was isolated from the surface of unwashed medical staff's hands and patients' body fluids. From intermediate to resistance, the antimicrobial characteristics of clone A and clone B to minocycline changed over a month, and there was one strain that was resistant to tigecycline. CONCLUSION: The outbreak of acinetobacter baumannii in the ICU was caused by carbapenem resistant acinetobacter baumannii (CRAb). The delicate changes of disk diffusion susceptibility in clones A and B occurred in one month. Unwashed hands of medical staff were probably responsible for the outbreak.

[Efficacies of ceftazidime and cefepime in rats with experimental pneumonia caused by extended-spectrum beta-lactamase-producing strain of Klebsiella pneumonia].

OBJECTIVE: To investigate the in vivo activities of ceftazidime and cefepime with susceptibility in vitro in rats with experimental pneumonia caused by extended-spectrum beta-lactamase-producing strain of Klebsiella pneumonia. METHODS: With intratracheal instillation method, 3 Klebsiella pneumonia strains isolated from this hospital were used to produce 3 groups of experimental model of pneumonia in rats. All the 3 strains showed resistant to cefotaxime and susceptible to piperacillin-tazobactam in vitro. To ceftazidime and cefepime, strain 1 was both susceptible. Strain 2 was susceptible to ceftazidime and resistant to cefepime. Strain 3 was resistant to ceftazidime and susceptible to cefepime. The three groups of rats were randomly assigned to one of the following five groups: one control group and four treatment groups. The efficacies were evaluated 96 hours later by the survival rate and the viable bacterial counts of the lungs (lg CFU/g). RESULTS: Group 1: piperacillin-tazobactam, ceftazidime and cefepime significantly improved the survival rate (75.0%, 76.9%, 80.0%) and reduced the bacterial counts [(10.8 +/- 2.8), (11.1 +/- 3.2), (11.0 +/- 3.7) lg CFU/g] compared with cefotaxime and the control group [36.0%, 32.0%; (15.7 +/- 5.6), (16.0 +/- 5.5) lg CFU/g; P < 0.05]. Group 2: piperacillin-tazobactam, ceftazidime significantly improved the survival rate (79.2%, 73.1%) and reduced the bacterial counts [(10.7 +/- 2.3), (11.0 +/- 2.7) lg CFU/g] compared with cefotaxime and the control groups [42.3%, 33.3%; (15.5 +/- 5.4), (15.8 +/- 4.6) lg CFU/g; P < 0.05]. Group 3: the survival rate in piperacillin-tazobactam and cefepime groups (80.8%, 75.0%) were significantly higher and the bacterial counts in piperacillin-tazobactam [(10.4 +/- 2.4) lg CFU/g] were significantly lower compared with the cefotaxime and the control groups [37.5%, 34.6%; (14.2 +/- 5.6), (15.3 +/- 4.9) lg CFU/g; P < 0.05]. CONCLUSION: Cefepime and ceftazidime can reduce the mortality and the number of viable bacteria in rat pneumonia caused by some ESBL-producing Klebsiella pneumonia strains susceptible to either of them and their efficacies were similar to piperacillin-tazobactam.

[Expression of high-level cephalosporinase due to mutation in the AmpC attenuator of a clinical Escherichia coli strain].

OBJECTIVE: To study the resistant phenotype of a clinical strain of Escherichia coli and to explore the effect of its attenuator mutation on AmpC expression. METHODS: A clinical strain of Escherichia coli 20022 (ECO20022) resistant to cefoxitin was isolated clinically. The phenotype was examined by three-dimensional methods, isoelectric focusing (IEF), and microdilution method. The regulator genes of ECO20022 were amplified and sequenced, and the difference between them was analyzed by BLAST method. Then the regulator genes were cloned into pCAT3-basic vector (a promoterless reporter gene vector). Microdilution method was used to detect the minimal inhibitory concentration (MIC) of chloramphenicol and ampicillin to this strain with E. coli ATCC25922 as quality control bacterium. ELISA was used to detect the content of chloramphenicol acetyl transferase (CAT). RESULTS: Compared to the standard E. coli K-12, there were four base substitutions, i.e., 22C-T, 26, 27TA-GT, and 32G-A in the attenuator region of ECO20022. Three-dimensional method showed that this strain was high AmpC-producing. IEF found that it produced three beta-lactamases with the values of PI of 5.4, 8.2, and 9.0 respectively. The beta-lactamase with the PI of 9.0 could be inhibited by cloxacillin but not by clavulanate. The strain was resistant to not only most of third generation cephalosporins, but also to cefepime; however it was still susceptible to carbapenem. The secondary structure of the attenuator RNA of ECO20022 was different from the traditional structure of E. coli K-12. The regulator gene was successfully cloned into pCAT3-basic vector and direct and indirect tests indicated that this regulator gene enhanced the CAT expressing level as much as 10 times that of Escherichia coli K-12. CONCLUSION: AmpC attenuator mutation leads to high AmpC expression in Escherichia coli, resulting in a significant rise of resistance level to beta-lactamase and a great menace to clinical antibiotic therapy.

[DHA-1 type cephalosporinase accompanied with SHV-12 prevailed in clinical isolates of Klebsiella pneumoniae].

OBJECTIVE: To study the prevalence, phenotype and genotype of the AmpC and ESBLs-producing clinical isolate of Klebsiella pneumoniae. METHODS: The clinical isolates of Klebsiella pneumoniae were examined by standard disk diffusion susceptibility tests, three-dimensional methods, isoelectric focusing (IEF) and microdilution methods. The conjugation experiment, multiplex PCR and DNA sequencing methods were used for further analysis. RESULTS: Four out of a total of 86 isolates tested were shown to be highly AmpC-producing by three-dimensional method. IEF showed that these strains produced a AmpC like beta-lactamase with a PI of 7.8, and DNA sequencing showed that the gene which expressed this AmpC like beta-lactamase was identical to DHA-1, a plasmid mediated cephalosporinase gene. These strains also produced an ESBL like beta-lactamase with a PI of 8.2 and the gene which expressed this beta-lactamase was identical to SHV-12. These strains were resistant not only to most of the third generation cephalosporins, but also to cefepime. However they were still susceptible to carbapenem. CONCLUSIONS: Highly AmpC-producing DHA-1 accompanied with SHV-12 in Klebsiella pneumoniae was reported here for the first time. They result in a significant rise in antibiotic resistance, which is regarded as a great challenge for clinical antibiotic therapy.

[A new member of CMY type cephalosporinase prevailing in Escherichia coli].

OBJECTIVE: To study the resistant phenotype and molecular biology character of plasmid mediated high AmpC-producing clinical isolates of Escherichia coli and to find new AmpC genotype. METHODS: The cefoxitin highly resistant clinical isolates of Escherichia coli were studied by K-B method, three-dimensional method, Isoelectric Focusing (IEF) and the MIC of these strains were examined by micro-dilution method. The conjugation experiment, multiplex PCR and DNA sequencing methods were used in further study. RESULTS: Above 719 strains studied, there are 6 isolates were showed as high AmpC-producing by three-dimensional method and IEF found they could produce a beta-Lactamase which PI was 8.9 and could be inhibited by cloxacillin but not by clavulnate. The strains were resistant to most of third generation cephalosporins, but were susceptible to cefepime, meropenem and imipenem. The experiment also showed that the gene which express this AmpC like beta-Lactamase could be transferable. Multiplex PCR indicated they belong to Citrobacter freundii family. Sequencing of corresponding DNA revealed 99% identities of the deduced amino acid sequence with CMY-2 and CMY-7 respectively. It is a new CMY type cephalosporinase. CONCLUSION: A new CMY type cephalosporinase has been found in clinical strains of Escherichia coli in our hospital. It was resistant to many antibiotics and its resistance could be transferred horizontally.