Emergence and prevalence of beta-lactamase-producing Klebsiella pneumoniae resistant to cephems in Japan

Forty-six cephem-resistant Klebsiella pneumoniae strains with minimum inhibitory concentrations>8 microg/mL for cefpodoxime and cefmetazole were selected from clinical isolates obtained between 2000 and 2002 from eight hospitals on Northern Kyushu Island, Japan. We investigated the mechanisms of resistance to cephems in these 46 K. pneumoniae isolates. The results of isoelectric focusing of beta-lactamases produced by these isolates, polymerase chain reaction for detection of various Class A, Class B and Class C beta-lactamases, and determination of the sequence of the beta-lactamase structural gene showed that most of these isolates had various types of broad-spectrum beta-lactamases. Of the 46 isolates, 2 were CMY-2 beta-lactamase producers and 41 were DHA-1 beta-lactamase producers. Forty of the 41 DHA-1 beta-lactamase producers simultaneously produced SHV-12 extended-spectrum beta-lactamase (ESBL), and the remaining isolate simultaneously produced SHV-27. Furthermore, one DHA-1 and SHV-12 beta-lactamase producer also produced IMP-1 beta-lactamase. The only broad-spectrum beta-lactamase with another isolate was IMP-1. Chromosomal DNA restriction fragment analysis using XbaI suggested that nosocomial infection due to DHA-1 and SHV-12 beta-lactamase producers had occurred at two centres. This is the first report of nosocomial infection due to DHA-1 beta-lactamase-producing K. pneumoniae including other plasmid-encoded AmpC beta-lactamases in Japan. The mechanisms of resistance of 44 of the 46 isolates to cephalosporins and cephamycins were ESBL production and/or plasmid-encoded AmpC beta-lactamase and/or IMP-1 beta-lactamase production. For two isolates, the mechanism of resistance to could not be identified. These results show that it is necessary to minimise the prevalence of these resistant strains as it will be a very serious problem if organisms producing these broad-spectrum beta-lactamases increase in clinical situations. It is important to detect these strains sooner and to perform rigorous infection control earlier.     

10种中药对产ESBLs大肠埃希菌的体外抑菌活性

目的测定乌梅等10味中药对产超广谱β-内酰胺酶（ESBLs）大肠埃希菌的体外抑菌活性,明确其最低抑菌浓度（MIC）,为临床应用中药治疗产ESBLs大肠埃希菌感染提供参考依据。方法各收集10株产ESBLs和非产ESBLs大肠埃希菌,制备适当浓度的各种中药煎液备用。采用琼脂稀释法进行定量抑菌试验,分别测定和比较各种中药的MIC值。对抑菌作用明显的中药进行产ESBLs和非产ESBLs大肠埃希菌MIC比较。结果中药乌梅、五倍子、黄连、黄芩、黄柏、穿心莲、鱼腥草、重楼、金银花、连翘对产ESBLs大肠埃希菌的MIC值分别为（17．19±4．94）mg／mL、（18．75±6．59）mg／mL、（37．50±10．21）mg／mL、（46．20±15．10）mg／mL、（450±105．41）mg／mL、（475±79．06）mg／mL、（237．50±39．53）mg／mL、（118．75±59．29）mg／mL、（425±88．19）mg／mL、（225±52．70）mg／mL,其中乌梅、五倍子、黄连、黄芩的MIC均值分别为17．19mg／mL、18．75mg／mL、37．50mg／mL、46．20mg／mL,有较好的抑菌效果。乌梅、五倍子、黄连、黄芩对产ESBLs和非产ESBLs大肠埃希菌MIC值经统计学处理,P〉0．05。结论10味中药对产ESBLs大肠埃希菌株均有不同程度的体外抑菌活性。其中乌梅和五倍子效果最强,其次是黄连、黄芩,其余的中药抑菌活性较弱。     

临床常见肠道细菌感染及耐药分析

肠杆菌属、枸橼酸杆菌属等在使用三代头孢菌素治疗期间会产生耐药性,因此原本敏感的菌株可能会在使用抗菌药物治疗3～4日时产生耐药性,抗菌药物的滥用已经发展成为一个影响人类健康和用药安全的社会问题。我国临床抗菌药物的使用状况不容乐观,药物滥用情况较西方发达国家要严重的多,细菌耐药性是困扰全球医务工作者的难题。正确选用抗菌药物不仅可以保证抗感染治疗取得良好的疗效,而且能减少其不良反应,延缓细菌耐药性的产生。     

焦磷酸测序检测产ESBLs革兰阴性菌的SHV基因型

目的探讨一种快速、准确检测产超广谱β-内酰胺酶(ESBLs)革兰阴性菌的ESBLs基因分型方法。方法双纸片法确定产ESBLs的临床分离菌,聚合酶链反应(PCR)扩增ESBLs的SHV基因片段,用焦磷酸测序技术对29株成都市区临床分离的产ESBLs肺炎克雷伯菌和大肠埃希菌进行SHV基因分型研究,检测SHV基因片段中编码35位氨基酸和编码43位氨基酸位点的基因多态性。同时,采用纸片扩散法进行药物敏感性试验。结果焦磷酸测序发现,本地区分离出的29株产ESBLs临床分离菌有21株扩增出SHV基因片段,且在43位氨基酸密码子均没有多态性,35位密码子有基因多态性,核苷酸由T突变为A,亮氨酸变为谷氨酰胺,突变发生率达到42.9%(9/21)。29株产ESBLs的菌株对亚胺培南全部敏感;对头孢西丁、头孢吡肟、头孢他啶耐药率分别为:大肠埃希菌29.4%、11.8%、41.2%;肺炎克雷伯菌50.0%、8.3%、33.3%;对氨苄西林、哌拉西林、头孢唑啉、头孢呋辛和复方磺胺甲口恶唑的耐药性较高,均达到75%以上,对其他药物均有不同程度的耐药性。结论焦磷酸测序技术可快速对临床分离菌产生的ESBLs耐药基因分型,具有准确、快速、实时和高通量等优点。     

Phylogenetic groups and antimicrobial resistance characteristics of Escherichia coli strains isolated from clinical samples in North Iran

Background and study aimExtraintestinal pathogenic Escherichia coli (ExPEC) is one of the most common bacterial pathogens, which causes a remarkable amount of morbidity and mortality. This study was designed to determine the antibiotic resistance profiles, phylogenetic groups, and subgroup analyses among the ExPEC strains isolated from hospitalized patients in north Iran.Patients and MethodsThis cross-sectional investigation was conducted at five educational hospitals in Rasht in north Iran. Using standard microbiological tests, 150 E. coli isolates were identified. The antibiotic susceptibility pattern of all isolates was determined using the disk diffusion method. The double disk phenotypic confirmatory test was performed to detect extended-spectrum β-lactamase (ESBL)-producing isolates. A triplex polymerase chain reaction (PCR) was performed to determine the phylogenetic group of each strain.ResultsThe results of antibiogram pattern showed that E. coli isolates were mostly non-susceptible to ampicillin (79.3%), followed by nalidixic acid (75.3%) and cephalothin (70%), whereas nitrofurantoin (94.7%) was the most effective agent, followed by imipenem (92.7%). The rate of ESBL-producing isolates was 53.3% (80/150). Multiplex PCR screening revealed that the most common phylogroup was the B2 group (97 isolates; 64.6%), followed by the D group (34, 22.7%). In contrast, phylogroup analyses showed that B2₃ (50.7%) and D₂ (16.4%) were the most common subgroups.ConclusionsOur findings indicated a considerable rate of antibiotic resistance and ESBL-producing isolates among E. coli strains isolated from clinical samples. Moreover, we reported a tendency that most isolates belonged to the B2 and D phylogroups. As a result, the detection of genotypic identical or similar isolates indicated that these isolates have an endurance capability in the hospital environment and could be transmitted among patients.     

High frequency of extended-spectrum beta-lactamase-producing Enterobacteriaceae carriers at a Japanese long-term care hospital

IntroductionLong-term care hospitals (LTCHs) are at a high risk for the inflow and spread of antimicrobial resistance (AMR) pathogens. However, owing to limited laboratory resources, little is known about the extent to which AMR organisms are endemic.MethodsWe performed active surveillance for carbapenem-resistant Enterobacteriaceae (CRE) and extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-E) in newly admitted patients at Marugame Medical Center, a nearly 200-bedded LTCH located in Kagawa, Japan. From August to December 2021, we tested stool samples from patients wearing diapers and confirmed the genetic variants using specific PCR assays. We also collected clinical variables and compared them between AMR carriers and non-carriers.ResultsStool samples were collected from 75 patients, with a median age of 84 years. CRE strain was not detected, but 37 strains of ESBL-E were isolated from 32 patients (42.7%). During the study period, 4.9% of in-hospital patients (37 per 756 patients) were identified to be ESBL-E carriers in the routine microbiological processing, suggesting that active surveillance detected approximately 9-fold more ESBL-E carriers. The bla_CTX-M-9 group was the most common (38.5%), followed by the bla_TEM (26.9%). The clinical backgrounds of the ESBL-E non-carriers and carriers were not significantly different.ConclusionOur active screening demonstrated that nearly half of the patients hospitalized or transferred to a Japanese LTCH were colonized with ESBL-E. We highlight the enforcement of universal basic infection prevention techniques at LTCHs where patients carrying AMR pathogens gather.     

Performance of the new FilmArray Blood Culture Identification 2 panel and its potential impact on clinical use in patients with Gram-negative bacteremia

IntroductionRapid diagnostic tests have been developed recently for rapid species or resistance genes identification, offering the potential to improve the selection of appropriate antibiotics. The newly developed FilmArray Blood Culture Identification 2 (BCID2) panel, which can identify more species and resistance genes, such as extended-spectrum beta-lactamase, is expected to make an impact on antimicrobial practice.MethodsThe consecutive 50 inpatients with Gram-negative bacilli bacteremia were enrolled to this retrospective single-center study. In addition to the existing FilmArray Blood Culture Identification (BCID) panel, we have implemented BCID2 panel for positive blood culture. The sensitivity and specificity of BCID and BCID2 panel were respectively calculated, and a simulation study of time to effective, optimal and de-escalation therapy was performed based on BCID or BCID2 result.ResultsA total of 52 Gram-negative organisms in 50 patients were identified from blood cultures. Of these, 45 (87%) organisms were detected by BCID2 panel, which was more than BCID panel (41 organisms, 79%). BCID2 panel detected 5 CTX-M genes, which were concordant with conventional method. The time to effective therapy did not differ between BCID arm and BCID2 arm; however, the median time to optimal therapy (34 h in BCID arm and 26 h in BCID2 arm, P = 0.0007) and the median time to de-escalation therapy (42 h in BCID arm and 22 h in BCID2 arm, P = 0.0005) were significantly shortened.ConclusionsThis simulation study of BCID2 panel showed high sensitivity and specificity, and the potential impact on shortening the time to optimal and de-escalation therapy.     

Estimating the association between antibiotic exposure and colonization with extended-spectrum β-lactamase-producing Gram-negative bacteria using machine learning methods: a multicentre,prospective cohort study

ObjectivesThe aim of the study was to measure the impact of antibiotic exposure on the acquisition of colonization with extended-spectrum β-lactamase-producing Gram-negative bacteria (ESBL-GNB) accounting for individual- and group-level confounding using machine-learning methods.MethodsPatients hospitalized between September 2010 and June 2013 at six medical and six surgical wards in Italy, Serbia and Romania were screened for ESBL-GNB at hospital admission, discharge, antibiotic start, and after 3, 7, 15 and 30 days. Primary outcomes were the incidence rate and predictive factors of new ESBL-GNB colonization. Random forest algorithm was used to rank antibiotics according to the risk of selection of ESBL-GNB colonization in patients not colonized before starting antibiotics.ResultsWe screened 10 034 patients collecting 28 322 rectal swab samples. New ESBL-GNB colonization incidence with and without antibiotic treatment was 22/1000 and 9/1000 exposure-days, respectively. In the adjusted regression analyses, antibiotic exposure (hazard ratio (HR) 2.38; 95% CI 1.29–4.40), age 60–69 years (HR 1.19; 95% CI 1.05–1.34), and spring season (HR 1.25; 95% CI 1.14–1.38) were independently associated with new colonization. Monotherapy ranked higher als combination therapy in promoting ESBL-GNB colonization. Among monotherapy, cephalosporins ranked first followed by tetracycline (second), macrolide (fourth) and cotrimoxazole (seventh). Overall the ranking of cephalosporins was lower when used in combination. Among combinations not including cephalosporins, quinolones plus carbapenems ranked highest (eighth). Among sequential therapies, quinolones ranked highest (tenth) when prescribed within 30 days of therapy with cephalosporins.ConclusionsImpact of antibiotics on selecting ESBL-GNB at intestinal level varies if used in monotherapy or combination and according to previous antibiotic exposure. These finding should be explored in future clinical trials on antibiotic stewardship interventions.Clinical Trial registrationNCT01208519.     

Infections caused by extended-spectrum β-lactamase-producing Enterobacterales after rectal colonization with ESBL-producing Escherichia coli or Klebsiella pneumoniae

ObjectivesInfections as a result of extended-spectrum β-lactamase-producing Enterobacterales (ESBL-E) are considered infections with a high public health burden. In this study, we aimed to identify incidences of and risk factors for healthcare-associated infections (HAIs) after rectal colonization with ESBL-producing Escherichia coli (ESBL-EC) or Klebsiella pneumoniae (ESBL-KP).MethodsThis prospective cohort study was performed in 2014 and 2015. Patients colonized with ESBL-EC or ESBL-KP were monitored for subsequent HAI with ESBL-E and other pathogens. In the case of an ESBL-E infection, rectal and clinical isolates were compared using pulsed-field gel electrophoresis (PFGE), and whole-genome sequencing (WGS) for ESBL-KP isolates. Proportional hazard models were applied to identify risk factors for HAIs, and to analyse competing risks.ResultsAmong all patients admitted to the hospital during the study period, 13.6% were rectally screened for third-generation cephalosporin-resistant Enterobacterales (3GCREB). A total of 2386 rectal carriers of ESBL-EC and 585 of ESBL-KP were included in the study. Incidence density (ID) for HAI with ESBL-E was 2.74 per 1000 patient days at risk (95% confidence interval (CI) 2.16–3.43) among carriers of ESBL-EC, while it was 4.44 per 1000 patient days at risk (95% CI 3.17–6.04) among carriers of ESBL-KP. In contrast, ID for HAI with other pathogens was 4.36 per 1000 patient days at risk (95% CI 3.62–5.21) among carriers of ESBL-EC, and 5.00 per 1000 patient days at risk (95% CI 3.64–6.69) among carriers of ESBL-KP. Cox proportional hazard regression analyses identified colonization with ESBL-KP (HR = 1.58, 95% CI 1.068–2.325) compared with ESBL-EC as independent risk factor for HAI with ESBL-E. The results were consistent over all competing risk analyses.ConclusionsClinicians should be aware of the increased risk of ESBL-E infections among patients colonized with ESBL-KP compared with ESBL-EC that might be caused by underlying diseases, higher pathogenicity of ESBL-KP and other factors.     

2型糖尿病合并感染患者的肺炎克雷伯菌分布及耐药特征分析

目的分析2型糖尿病(T2DM)合并感染患者的肺炎克雷伯菌分布及耐药特征。方法从126例T2DM合并感染患者的痰液、尿液等标本分离肺炎克雷伯菌,全自动微生物分析仪鉴定细菌及药敏试验,测定菌株产超广谱β-内酰胺酶(ESBL)情况。结果126株来自T2DM合并感染患者的肺炎克雷伯菌,在痰液、尿液、血液、脓液及其他标本的构成比分别为45.2%、19.1%、12.7%、9.5%和13.5%;痰液的肺炎克雷伯菌对头孢哌酮/舒巴坦耐药率(31.7%)高于非痰液标本(22.2%)(P<0.01),痰液的肺炎克雷伯菌对庆大霉素耐药率(23.0%)高于非痰液标本(15.9%)(P<0.05);双重耐药、3种及以上药物耐药菌株检出率均高于单一耐药菌株检出率(P<0.01);痰液的产ESBL酶肺炎克雷伯菌检出率(17.5%)高于非痰液标本(6.3%)(P<0.01)。结论T2DM合并感染患者的肺炎克雷伯菌主要分布在痰液和尿液中,菌株交叉耐药现象较严重,产ESBL肺炎克雷伯菌趋于增多。