Carbapenemases: A worldwide threat to antimicrobial therapy

Carbapenems are potent β-lactams with activity against extended-spectrum cephalosporinases and β-lactamases. These antibiotics, derived from thienamycn, a carbapenem produced by the environmental bacterium Streptomyces cattleya, were initially used as last-resort treatments forsevere Gram-negative bacterial infections presenting resistance to most β-lactams but have become an empirical option in countries with high prevalence of Extended Spectrum β-lactamase-producing bacterial infections. Imipenem, the first commercially available carbapenem, was approved for clinical use in 1985. Since then, a wide variety of carbapenem-resistant bacteria has appeared, primarily Enterobacteriaceae such as Escherichia coli or Klebsiella pneumoniae(K. pneumoniae), Pseudomonas aeruginosa and Acinetobacter baumannii, presenting different resistance mechanisms. The most relevant mechanism is the production of carbapenem-hydrolyzing β-lactamases, also known as carbapenemases. These enzymes also inactivate all known β-lactams, and some of these enzymes can be acquired through horizontal gene transfer. Moreover, plasmids, transposons and integrons harboring these genes typically carry other resistance determinants, rendering the recipient bacteria resistant to almost all currently used antimicrobials, as is the case for K. pneumoniae carbapenemase- or New Delhi metallo-β-lactamases-type enzymes. The recent advent of these enzymes in the health landscape presents a serious challenge. First, the emergence of carbapenemases limits the currently available treatment options; second, these enzymes pose a risk to patients, as some studies have demonstrated high mortality associated with carbapenemase-producing bacterial infections; and third, these circumstances require an extra cost to sanitary systems, which are particularly cumbersome in developing countries. Therefore, emphasis should be placed on the early detection of these enzymes, the prevention of the spread of carbapenemase-producing bacteria and the development of new drugs resistant to carbapenemase hydrolysis.

Detection of the Production of Klebsiella Pneumoniae Carbapenemase, New Delhi Metallo-Beta-Lactamase and Oxacillinase-48-Type Carbapenemases by Gram-Negative Bacilli in Resource-Limited Setting

Background: The increasing resistance of bacteria to various antibiotics is a worldwide public health issue. Carbapenems that have elicited great hope in treating infections caused by multidrug-resistant germs have seen their efficacy narrowed over time with the emergence of other novel resistance mechanisms, notably the production of Carbapenemases. Methods: A prospective cross-sectional study was conducted from May 2017 to May 2018 in Douala (Cameroon) to detect carbapenemase-producing Gram-negative bacilli. Isolated strains were identified using the Vitek2TM system. Antimicrobial susceptibility testing was performed using the Kirby-Bauer disk diffusion method on agar plates with 20 selected commercially available antibiotic discs. The bacterial strains were tested for the production of three Carbapenemases (OXA-48, NDM, KPC), using an immuno-chromatographic technique, with the “RESIST-3 O.K.N. K-SeT” rapid detection kit. Results: During the study period, 1687 strains of Gram-negative bacilli were isolated in selected laboratories with a total of 200 multi-resistant strains identified (11.9%). Among the multi-resistant strains, E. coli was the species most represented in Enterobacteriaceae (27.5%) followed by K. pneumoniae (15.5%) and the non-fermenting Gram-negative bacilli were predominantly P. aeruginosa (20.5%). These strains mainly came from urine and pus, i.e. 41% and 32% respectively. Thirty-two (16%) strains produced one of the Carbapenemases with a higher frequency at the General Hospital (84%). NDM-type carbapenemase was the most frequently identified (8.5%), OXA-48 type 7.5%, and no KPC production was observed. Among the Enterobacteriaceae 22.9% produced Carbapenemases and only 5.1% of the non-fermenting bacilli produced these enzymes. The isolates strains were completely resistant to all antibiotics except Amikacin and Fosfomycin. The strains producing the NDM-type carbapenemase showed higher rates of resistance to almost all of the antibiotics tested. Conclusion: Multidrug-resistant strains are experiencing an increase in evolution. The apparition of strains producing Carbapenemases prominently, the NDM and OXA-48 favor this increase. The activities of antibiotics with high efficacies on these strains are low.

Phenotypic Characterization of Extended Spectrum Beta-Lactamase, Class C Cephalosporinase and Carbapenemase-Producing Klebsiella Species Isolated from Patients Consulted at Four Yaounde-Based Hospitals

Background: Klebsiella spp. are bacteria of medical importance for their role in opportunistic infections which are often difficult to treat because of resistance to one or several antimicrobials. The aim of this study was to determine antimicrobial resistance due to Extended Spectrum Beta-lactamase (ESBL), Class C cephalosporinase (AmpC) and carbapenemase enzymes in Klebsiella spp. isolated from patients consulted at four hospitals. Methodology: The study was cross-sectional and descriptive. A total of 4190 non-repetitive patients specimens from 13 types of clinical specimens were analysed from February to November 2020. Two hundred and twenty-five (225) Klebsiella spp isolates were identified using API 20E and antimicrobial susceptibility testing done according to the Kirby Bauer disc diffusion method. ESBL and AmpC phenotypes were determined by the combination disc method and carbapenemases by double disc synergy method, referenced by EUCAST guidelines for the resistance testing. Results: The frequency of the species was Klebsiella pneumoniae (69%, 155/255), K. oxytoca (14%, 31/255), K. ozaenae (12%, 27/225) and K. rhinoscleromatis (5%, 11/225). Isolates were most resistant to sulphomethoxazole trimethoprim (84%, 189/225), cepaholosporins (80%, 180/225), and least resistant to carbapenems (10.7%, 24/225). Two K. oxytoca and one K. pneumoniae were resistant to all antibiotics tested. Klebsiella pneumoniae had the most multidrug resistant isolates (59.4%, 134/225). Most isolates (83.6%, 188/225) expressed at least one enzyme, while 63.6% (143/225) of the isolates expressed at least two enzymes. Some isolates were ESBL (71.6%, 161/225), carbapenemase (10.7%, 24/225) and AmpC (6.6%, 15/225) producers. Three carbapenemases (Klebsiella pneumoniae carbapenemase-KPC, Metallo-Beta Lactamase-MBL and OXA-48) were detected. Conclusion: These results revealed that resistance of Klebsiella spp. to cephalosporins is high and this may be exacerbated by co-expression of AmpC and carbapenemases aggravating associated patient morbidity and mortality. Monitoring of antimicrobial resistance of local strains is necessary for informed decisions on empirical treatment. .

Molecular Detection of Extended-Spectrum Beta Lactamase and Carbapenemase Genes in Escherichia coli and Salmonella spp. Isolated from Chickens Consumed Outdoors in Ouagadougou, Burkina Faso

This study was carried out to assess the prevalence of resistance genes in strains of Escherichia coli and Salmonella spp. isolated from free-range chickens in Ouagadougou, where resistant bacteria can be transmitted to humans via faeces or contaminated meat. A total of 280 strains of Escherichia coli and 129 strains of Salmonella spp. resistant to at least one beta-lactam or carbapenem antibiotic were used in this study. PCR analyses revealed the presence of ESBL (extended spectrum beta lactamase) resistance genes in Escherichia coli isolates, with 3.21% (9/280) possessing the CTX-M (Cefotaximase) gene, 15.35% (43/280) had the SHV (Sulfhydril Variable) gene, and 11.42% (32/280) had carbapenemase resistance genes, more specifically IMP (Imipenemase metallo-beta-lactamase). As regards Salmonella spp. strains, only the presence of the SHV (Sulfhydril Variable) gene was identified in 2.32% (3/129) of isolates belonging to the ESBL family, while 26.35% (34/129) and 13.95% (18/129) of isolates respectively possessed the IMP (Imipenemase metallo-beta-lactamase) and NDM (New Delhi metallo-β-lactamase) genes, both of the carbapenemase type. The significant prevalence of resistance genes in bacterial strains isolated from chickens sold outdoors in Ouagadougou raises major public health concerns, due to the possible transmission of these resistant strains to humans through the consumption of contaminated meat, thus complicating the treatment of bacterial infections.

Phenotypic Detection of Enterobacterales Strains Susceptible of Producing OXA-48 Carbapenemase

Background: Nowadays, emergence of Carbapenemase-Producing Enterobacterales (CPE) throughout the world has become a public health problem, especially in countries with limited resources. In recent years, CPE of type OXA-48 (Ambler class D) have been identified in Dakar. The aim of this study was to evaluate the phenotypic detection of OXA-48 CPE using a temocillin disc (30 μg). Methodology: A retrospective study was carried out at Medical Biology Laboratory of Pasteur Institute in Dakar on Ertapenem-Resistant Enterobacterales (ERE) strains isolated from 2015 to 2017. These strains were then tested with a 30 μg temocillin disc. Any strain resistant to temocillin (inhibition diameter Results: Forty-one ERE isolated during the study period were tested, of which 34 (82.9%) were OXA-48 based on phenotypic detection using temocillin disc and confirmed by PCR (100%). OXA-48 CPE strains detected were composed of Klebsiella pneumoniae (n = 14;41.2%), Enterobacter cloacae (n = 8;23.5%), Escherichia coli (n = 7, 20.5%), Citrobacter freundii (n = 3;8.8%), Cronobacter sakazakii (n = 1;3%) and Morganella morganii (n = 1;3%). Conclusion: Temocillin resistance has a good positive predictive value for detecting OXA-48 CPE by phenotypic method, confirmed by PCR. Temocillin is therefore a good marker for detection of OXA-48 CPE except Hafnia alvei.

1例混合耐药机制碳青霉烯类耐药肺炎克雷伯菌肺部感染治疗实践

目的 为碳青霉烯类耐药肺炎克雷伯菌(CRKP)感染的临床诊疗提供参考。方法 整理医院收治的1例存在生物膜形成、产超广谱β内酰胺酶(ESBLs)、产肺炎克雷伯菌碳青霉烯酶(KPC)、产NDM型B类金属碳青霉烯酶等混合耐药机制CRKP肺部感染病例的诊疗资料,结合文献总结并分析其治疗策略。结果 入院后结合患者初始治疗失败原因及CRKP感染流行病学特征,首先予注射用头孢他啶阿维巴坦经验性治疗,患者炎性指标大幅下降、(代谢性)酸中毒症状迅速纠正;入院第5-6天,因痰培养见生物膜形成和细菌分离示产金属酶肺炎克雷伯菌(产NDM酶型),加用注射用阿奇霉素、注射用替加环素联合治疗,患者临床症状、炎性指标持续好转;入院第10天,参照药物敏感性试验(简称药敏)结果调整为注射用替加环素、注射用阿奇霉素、硫酸阿米卡星注射液联合序贯治疗,辅以对症支持治疗、气道廓清术、体位引流等处理;入院第22天,患者病情好转出院。结论 临床应充分认识CRKP的耐药机制,对不同抗菌药物的耐药特性、流行病学特征,做好初始经验治疗药物选择,结合临床症状改善与细菌培养药敏结果综合评估调整治疗方案,同时辅以积极的对症处理。

大肠埃希菌的临床分布、耐药性及碳青霉烯耐药株基因序列分析

目的分析大肠埃希菌的临床分布、耐药性及碳青霉烯耐药株基因序列。方法选取2021年1月至2023年12月山东省潍坊市中医院送检标本中分离的1837株大肠埃希菌为研究样本,分析大肠埃希菌的临床科室分布、样本类型分布、抗菌药物耐药情况、碳青霉烯类耐药情况以及碳青霉烯类耐药基因检测结果。结果1837株大肠埃希菌主要分布在泌尿外科(13.4%),主要样本类型为尿液(43.3%)。大肠埃希菌对阿米卡星、呋喃妥因、亚胺培南、美罗培南、哌拉西林/他唑巴坦、厄他培南的敏感性较高,对氨苄西林、环丙沙星、左氧氟沙星的耐药率较高。1038(56.5%)株为产超广谱β-内酰胺酶(ESBLs)阳性,有57株(3.1%)为耐碳青霉烯类大肠埃希菌(CREC)。基因序列分析发现,耐药基因存在碱基序列的缺失和/或增加,可能对菌株的抗菌药物敏感性产生影响。结论大肠埃希菌广泛分布于医院各科室,其对青霉素和β-内酰胺类抗菌药物呈现出一定的耐药性。

铜绿假单胞菌耐药特点及产碳青霉烯酶菌株基因检测

目的了解某院铜绿假单胞菌耐药特点和产碳青霉烯酶菌株的基因型,为临床抗感染治疗提供参考。方法收集2022年8月至2023年10月福建医科大学附属泉州第一医院临床分离的铜绿假单胞菌的耐药性及临床特征,通过改良碳青霉烯酶灭活试验和碳青霉烯酶抑制剂增强试验检测碳青霉烯类耐药铜绿假单胞菌(CRPA)碳青霉烯酶表型,采用聚合酶链反应扩增碳青霉烯酶基因。结果共分离328株铜绿假单胞菌,其中痰液标本184株(56.10%),创面分泌物标本60株(18.29%),尿液标本45株(13.72%),静脉全血标本24株(7.32%),胸腔积液和腹水标本10株(3.05%),组织标本4株(1.22%),导管标本1株(0.30%)。菌株来自21个科室,其中重症医学科111株(33.84%)、烧伤科34株(10.37%)、泌尿外科29株(8.84%)、呼吸科26株(7.93%)、综合病房17株(5.18%)、神经外科14株(4.27%)、血液内科11株(3.35%)、肝胆外科11株(3.35%)、心血管外科11株(3.35%)、骨科10株(3.05%)、神经内科10株(3.05%)、儿科8株(2.44%)、感染科6株(1.83%)、胃肠外科6株(1.83%)、内分泌科6株(1.83%)和肾内科5株(1.53%),其他科室13株(3.96%)。检出22株(6.71%)多重耐药铜绿假单胞菌。药敏试验结果显示,铜绿假单胞菌对多黏菌素B敏感率达100.00%,对阿米卡星、庆大霉素、头孢哌酮-舒巴坦、哌拉西林-他唑巴坦、环丙沙星的敏感率较高,分别为97.26%、89.33%、83.23%、81.10%和81.71%;对氨曲南、左氧氟沙星、头孢吡肟和头孢他啶耐药率较高,分别为22.26%、17.07%、16.77%和16.16%;对亚胺培南和美罗培南的耐药率分别为9.15%和7.93%。分离CRPA菌株30株,分离自重症医学科(63.34%,19/30)、神经外科(13.33%,4/30)、呼吸科(10.00%,3/30)和其他科室(13.33%,4/30);标本来源于痰液(86.67%,26/30)、分泌物(6.67%,2/30)、尿液(3.33%,1/30)和静脉全血(3.33%,1/30)。结论本研究MDR-PA和CRPA检出率较低,CRPA菌株主要产VIM-2型和IMP-9型金属β内酰胺酶。

A Five-year Surveillance of Carbapenemase-producing Klebsiella pneumoniae in a Pediatric Hospital in China Reveals Increased Predominance of NDM-1

Objective To characterize carbapenem （CPM）-non-susceptible Klebsiella pneumoniae （K. pneumoniae） and carbape-nemase produced by these strains isolated from Beijing Children＇s Hospital based on a five-year surveillance. Methods The Minimal Inhibition Concentration values for 15 antibiotics were assessed using the Phonixl00 compact system. PCR amplification and DNA sequencing were used to detect genes encoding carbapenemases. WHONET 5.6 was finally used for resistance analysis. Results In total, 179 strains of CPM-non-susceptible K. pneumoniae were isolated from January, 2010 to December, 2014. The rates of non-susceptible to imipenem and meropenem were 95.0% and 95.6%, respectively. In the 179 strains, 95 （53.1%） strains carried the blalMP gene, and IMP-4 and IMP-8 were detected in 92 （96.8%） and 3 （3.2%） IMP-producing isolates, respectively. 65 （36.3%） strains carried the blaNDM_1 gene. 6 （3.4%） strains carried the blaKpc gene, and KPC-2 were detected in 6 KPC-producing isolates. In addition, New Delhi-Metallo-1 （NDM-1） producing isolates increased from 7.1% to 63.0% in five years and IMP-4 producing isolates decreased from 75.0% to 28.3%. Conclusion High frequencies of multiple resistances to antibiotics were observed in the CPM-non-susceptible K. pneumoniae strains isolated from Beijing Children＇s Hospital. The production of IMP-4 and NDM-1 metallo-13-1actamases appears to be an important mechanism for CPM-non- susceptible in K. pneumoniae.

High prevalence of multidrug-resistance in Acinetobacter baumannii and dissemination of carbapenemase-encoding genes bla_(OXA-23-like),bla_(OXA-24-like)and bla_(NDM-1) in Algiers hospitals

Objective:To assess and characterize antibiotic resistance in Acinetobacter baumannii strains recovered from 5 health-care facilities in Algiers.Methods:Antibiotic susceptibility testing was performed by agar diffusion and agar dilution methods,resistance genes were identified by PCR and sequencing,and molecular typing of isolates was carried out by enterobacterial repetitive intergenic consensus-PCR(ERIC-PCR).Results:Among 125 tested isolates,117(93.6% ) were multidrug-resistant.of which 94(75.2% ) were imipenem resistant.The bla_(ADC)and bla_(OXA-51-like) genes were detected in all isolates,in association with ISAba I sequence in 84% and 8% (imipenem resistant) of isolates,respectively.The bla_(OXA-23-like) and bla_(OXA-24-like)carbapenemase genes were delected in 67.02% and 20.21% of imipenem-resistant isolates,respectively.The bla_(OXA-23-like) gene is linked to ISAba1 or ISAba4 elements.The metallo-β-lactamase NDM-1 gene was found in 10(10.6% ) imipenem-resisianl strains from three hospitals,it is linked to ISAba125 clement in nine strains.Extended spectrum β-lactamases production was not detected.Imipenem and cefotaxime resistance phenolypes could not be transferred to Escherichia coli by conjugation.Outer membrane protein CarO gene was not delected in four imipenem-resisianl isolates.The aac(6')-1b.sul1,sul2,tetA and tetB genes were present in 5.31% .36.17% .77.65% .1.06% and 65.92% of strains,respectively.Class 1 integrons were detected in 23.4% strains.KRIC-PCR typing showed a genetic diversity among bla_(OXA-23-like) and bla_(OXA-24-like) positive strains,while clonality was observed among bla_(NDM-1)positives.Conclusions:This study highlighted the high prevalence of imipenem resistance in Acinetobacter baumannii in Algiers hospitals mediated mainly by bla_(OXA-23-like),bla_(OXA-24-like),and bla_(NDM-1) genes.

Genomic and Phenotypic Diversity of Carbapenemase-Producing Enterobacteriaceae Isolates from Bacteremia in China: A Multicenter Epidemiological, Microbiological, and Genetic Study

Carbapenemase-producing Enterobacteriaceae(CPE) isolates are recognized as one of the most severe threats to public health. However, the population structure and genetic characteristics of CPE isolates among bloodstream infections(BSIs) are largely unknown. To address this knowledge gap, in this study,we included patients with clinically significant BSIs due to Enterobacterales isolates, recruited from 26 sentinel hospitals in China(2014–2015). CPE isolates were microbiologically and genomically characterized,including their susceptibility profiles, molecular typing, phylogenetic features, and genetic context analysis of carbapenemase-encoding genes. Of the 2569 BSI Enterobacterales isolates enrolled, 42(1.6%) were carbapenemase-positive. Moreover, among the 2242 investigated isolates, 1111(49.6%) extendedspectrum β-lactamase(ESBL)-producing isolates were identified in Escherichia coli(E. coli), Klebsiella pneumoniae(K. pneumoniae), Proteus mirabilis(P. mirabilis), and Klebsiella oxytoca. Whole genome sequencing analysis showed the clonal spread of K. pneumoniae carbapenemase(KPC)-2-producing K. pneumoniae sequence type(ST) 11 and New Delhi metallo-β-lactamase(NDM)-5-producing E. coli ST167 in our collection. Plasmid analysis revealed that carbapenemase-encoding genes were located on multiple plasmids. A high prevalence of biofilm-encoding type 3 fimbriae clusters and yesiniabactin-associated genes was observed in K. pneumoniae isolates. This work demonstrates the high prevalence of ESBLs and the wide dissemination of CPE among BSI isolates in China, which represent real clinical threats. Moreover, our findings first illustrate a more comprehensive genome scenario of CPE isolates among BSIs. The clonal spread of KPC-2-producing K. pneumoniae ST11 and NDM-5-producing E. coli ST167 needs to be closely monitored.

Dissemination and Genetic Structure of Carbapenemase Encoding Genes (bla_OXA-23and bla_OXA-24) in <i>Acinetobacter baumannii</i>from Southern Texas

Acinetobacter baumannii is one of the most important human pathogens causing a variety of nosocomial infections. Carbapenem antibiotics have been primarily used to treat the A. baumannii infections. However, carbapenem resistant A. baumannii producing carbapenemases causes serious treatment problems worldwide. Outbreaks of carbapenem resistant isolates have reported in some area of the United States, but their dissemination and genetic structure of the carbapenemase encoding genes are currently little known. To understand outbreaks, dissemination, and genetic structure of the carbapenemase encoding genes in Southern Texas, 32 clinical isolates collected from Austin and Houston, TX were characterized. Twenty-eight of 32 isolates were resistant to all tested β-lactam antibiotics including carbapenem (imipenem and meropenem). Three of them carried blaOXA-23 as a part of Tn2008 integrated into a known plasmid (pACICU2) and all others carried blaOXA-24 flanked by XerC/XerD-like recombinase binding sites that were adjoined by DNA sequences originated from multiple plasmids. Genotype analysis revealed that the 25 isolates carrying blaOXA-24 were all identical genotypes same as a representative isolate carrying blaOXA-24 from Chicago, IL but the 3 isolates carrying blaOXA-23 was a distinct genotype as compared with isolates carrying blaOXA-23 from Chicago, IL and Washington, D.C. Each of the blaOXA-23 and blaOXA-24 was transferred to carbapenem susceptible A. baumannii and E. coli with similar minimal inhibitory concentration (MIC) of carbapenem as that of their parental isolates but significantly lower levels of MIC in E. coli. Overall results suggest that a unique strain carrying blaOXA-23 and a similar strain carrying blaOXA-24 as seen in other geographic areas are currently disseminated in Southern Texas.

Phenotypic Characterization of Carbapenemase-Producing Enterobacteriaceae Strains in a Referral Teaching Hospital in Yaoundé, Cameroon

Background: Carbapenemase-producing Enterobacteriaceae (CPE) are an important and increasing threat to global health. They are nowadays more encountered routinely in hospitals and cause high morbidity and mortality due to limited therapeutic alternatives. This study sought to determine the prevalence of CPE in Yaoundé teaching hospital, Cameroon, and the associated risk factors. Materials and Method: To achieve this goal, a descriptive cross-sectional study coupled to an analytical component with consecutive collection of Enterobacteria strains was carried out during a three-month period (from 27th July to 24th October 2018) in the University Teaching Hospital of Yaoundé, Cameroon. The oxidase and biochemical identification tests using a miniaturized Api 20 E system were performed on colonies grown on Eosin Methylene Blue (EMB) medium and subcultured on nutrient agar. Drug susceptibility testing was carried out according to the Antibiogram Committee of the French Society of Microbiology (CA-SFM 2018.V.2.0). The detection of carbapenemase production was performed by the CA-SFM 2018 algorithm for the screening of carbapenemase-producing enterobacteriaceae and its classification by inhibitory synergy tests. Results: Out of the 104 isolates, Escherichia coli (50%) was the most prevalent species, followed by Klebsiella pneumoniae (37.5%) and Citrobacter frendii (12.5%). Drugs susceptibility patterns showed a high resistance to penicillins group (97.4% to amoxicillin), cephalosporins (68.4% to cefotaxim, 58.1% to cefixim, 60.7% to ceftazidim, 57.1% of cefoxitin) and aztreonam (55.7%). However, 11.9% carbapenems related resistance was noticed: 14.4% to imipenem, 13.8% to ertapenem and 7.5% to meropenem. Numerous co-resistance to quinolones (65.8%), fluoroquinolones (49.6%), aminoglycosides (49.6%) and cotrimoxazole (71.8%) were also observed. From 104 isolates, AmpC production represented 23.08% (25/104) and 36.54% (38/104) were ESBL-isolates. The overall prevalence of CPE was 25% (26/104) with K.pneumoniae predominant (61.53%). Besides, Class A and class B carbapenemase were mainly produced with respectively 20% (21/104) and 5% (5/104). Univariate analysis revealed a significant association of carbapenemase production to Klebsiella pneumoniae (p = 0.01), ESBL and AmpC production ((P = 0.01 and P = 0.001 respectively) while that association was only significant to Klebsiella spp (p = 0.04) and AmpC production (p = 0.02) in multivariate analysis. Conclusion: The multi-resistance of Enterobacteriaceae to antibiotics in Cameroon has considerably increased. More attention should be paid to those bacteria to stall antimicrobial resistance spread.

Colistin Resistance Profiles, Molecular Investigation of mcr-1 and mcr-2 Plasmid Genes and Investigation of Carbapenemase Production in Pseudomonas and Acinetobacter Strains

Background and Purpose: The reintroduction of colistin as a last resort treatment against multi-resistant Gram-negative bacilli, is currently challenged by the emergence of colistin-resistant bacteria. The aim of this study was to assess the susceptibility of Pseudomonas and Acinetobacter strains to colistin, to identify carbapenemase production, and to investigate the plasmid genes involved in colistin resistance and carbapenemase production. Methodology: In order to establish the susceptibility profiles of 17 strains of Pseudomonas and Acinetobacter to colistin, their Minimum Inhibitory Concentrations (MICs) were determined using the liquid microdilution method. The possible production of carbapenemases was investigated with the modified Carbapenem Inactivation Method (mCIM). The search for genes encoding carbapenemases (blaOXA, blaIMP, blaCarba) and those responsible for plasmid resistance to colistin (mcr-1 and mcr-2) was performed by conventional PCR. Results and Conclusion: Ninety-four percent (94%) (16/17) of the strains were resistant to colistin. Intraspecies distribution was 50% (8/16), 31% (5/16), 13% (2/16) and 6% (1/16) for Acinetobacter baumannii, Pseudomonas aeruginosa, Pseudomonas luteola, and Pseudomonas fluorescens, respectively. Twenty-nine percent (29%) (6/17) of the strains produced carbapenemases. No mcr-1 and mcr-2 plasmid genes were detected. On the other hand, 17.6% (3/17) of the strains possessed the carbapenemase genes distributed as follows: Carba type (60%), OXA type (40%) and IMP type (0%). The results of this study highlight a high resistance to colistin in strains belonging to the genera Acinetobacter and Pseudomonas, and some of these strains produce carbapenemases.

Phenotypic Characterization and Prevalence of Carbapenemase-Producing Acinetobacter baumanii Isolates in Four Health Facilities in Cameroon

Background and Objective: Nowadays, the clinical utility of carbapenems is threatened by the emergence of resistant bacteria, favored by its increasing use. According to the WHO, Acinetobacter baumannii: nosocomial infection agent, tops the list of priority antibiotic-resistant pathogens, considered to be the riskiest for humans. This study sought to determine the prevalence of carbapenemase-producing Acinetobacter baumannii strains in four health facilities in the Center and Littoral regions of Cameroon and the associated risk factors. Materials and Method: An analytical cross-sectional study was conducted over a six-month period from January to June 2022. All suspicious A. baumanii isolates obtained from pathological samples at the bacteriology laboratory of the different health facilities were systematically collected and re-identified. Re-identification and antimicrobial susceptibility Testing (AST) were performed using the VITEK 2 System and the Kirby-Bauer method according to the guidelines of the Clinical and Laboratory Standards Institute (CLSI). Detection and phenotypic characterization of carbapenemases was performed according to adequate standard procedures. Results: A total of 168/226 clinical isolates of Acinetobacter baumannii were confirmed after re-identification, among which 52.69% derived from male patients, 55.09% from participants aged between 10 - 39 years old, and 46.71% from pus samples. A very high resistance rates to all families of antibiotics was noted, except to colistin (10.2%). 40.12% of these isolates produced carbapenemase, represented by 62.69% of class B and 37.31% of class A. Carbapenemase production was observed only at HMR1, Centre region and at Laquintinie hospital, Littoral region with 53.33% and 50% respectively, even if there is no significant difference (P = 0.81). In addition, frequent hospitalisation was significantly associated to the production of carbapenemase among A. baumanii (Adjusted-OR = 16.53, P-value 0.0001). Conclusion: This study highlighted the emergence of carbapenemase-producing Acinetobacter baumannii which is increasingly growing. Continuous drug-resistant monitoring and preventive measures could help to prevent and curb the dissemination of A. baumanii resistance genes, especially in health settings.

一株多重耐药大肠杆菌全基因组测序及其耐药性分析

为了解大肠杆菌携带的粘菌素耐药基因并筛选敏感药物,解决多重耐药和动物临床无药可选的困局,采用16S rRNA菌种全基因组测序,PCR筛查mcr-4、mcr-5、blaTEM和AmpC酶耐药基因,应用BLAST和MEGA软件进行生物信息学和系统进化树分析,并对该菌株进行了78种抗生素抗菌药物敏感性测试及4种天然植物提取物(黄藤素、黄连素、黄芩苷和博落回)的抑菌、杀菌效果试验。结果表明,从2021年(1—12月)和2022年(1—6月)猪临床腹泻病例肠道中分离鉴定的145株大肠埃希菌(Escherichia coli,E.coli)中,鉴定出1株同时携带粘菌素耐药基因(mcr-4,mcr-5)和β内酰胺酶blaTEM、AmpC基因的猪源大肠埃希氏菌临床菌株HN2149。78种抗生素药敏试验结果显示,HN2149菌株对头孢吡肟、头孢地嗪、磷霉素、头孢克肟、头孢唑林、头孢哌酮、美洛培南、头孢西丁、头孢呋辛、头孢曲松、头孢噻肟、头孢他啶、替卡西林/克拉维酸、头孢哌酮/舒巴坦、氨曲南、哌拉西林/他唑巴坦、头孢噻肟/克拉维酸、头孢唑肟、头孢美唑、头孢他啶/克拉维酸和头孢他美敏感,对其余57种抗菌药物表现为耐药。4种植物提取物的药敏结果显示,博落回对菌株HN2149的抑菌、杀菌效果较好,其余3种提取物均对该菌株无抑菌和杀菌效果。以上研究结果为猪大肠杆菌病的防控提供参考。

产KPC肺炎克雷伯菌感染治疗的研究进展

近年来全国耐碳青霉烯类肺炎克雷伯菌(CRKP)分离率逐年上升,且由于其多重耐药、病死率高的特点,给临床治疗带来了严峻挑战。CRKP耐药最主要机制为产碳青霉烯酶,在CRKP中常见的碳青霉烯酶类型为Ambler A、B、D类,C类少见。碳青霉烯酶中最常见的是肺炎克雷伯菌碳青霉烯酶(KPC),属于A类。产KPC肺炎克雷伯菌(KPC-KP)在全球范围内广泛扩散,临床有效治疗药物非常有限。本文就KPC-KP感染治疗的研究进展进行总结,以期为临床治疗提供借鉴意义。

青海省碳青霉烯类耐药肠杆菌目细菌的分子流行病学分析

目的通过研究2022年7月至2023年5月青海省5家医院分离的碳青霉烯类耐药肠杆菌目细菌(CRE)的分布、基因型及耐药性,为临床CRE感染的治疗、院内感染防控,以及抗菌药物制订和评价提供数据支持。方法采用基质辅助激光解析电离飞行时间质谱仪进行细菌鉴定,采用VITEKⅡcompact进行细菌药敏试验,采用碳青霉烯酶抑制剂增强试验进行产酶表型鉴定,采用聚合酶链反应检测碳青霉烯酶基因(blaKPC、blaNDM、blaIMP、blaVIM和blaOXA-48)。对分离出的优势菌株进行多位点序列分型(MLST)和同源性分析。结果共分离出59株CRE,其中50株分离自临床标本,9株分离自患者所处的环境;59株CRE中阴沟肠杆菌23株,肺炎克雷伯菌22株,大肠埃希菌7株,产酸克雷伯菌5株,弗氏柠檬酸杆菌和布氏柠檬酸杆菌各1株。CRE主要分离于重症监护病房、烧伤科、肝胆科。标本来源主要为伤口分泌物、痰液、血液。59株CRE对酶抑制剂复合制剂、头孢菌素类、氨曲南及碳青霉烯类等抗菌药物均具有较高的耐药率(87.5%~100.0%),对阿米卡星和替加环素的耐药率相对较低,分别为30.4%和15.5%。最常见的碳青霉烯酶基因型是blaNDM(59.32%,35/59),其次是blaKPC(32.20%,19/59),肺炎克雷伯菌中blaKPC-2检出率最高(72.73%,16/22),阴沟肠杆菌中blaNDM-1检出率最高(69.57%,16/23)。MLST结果显示,肺炎克雷伯菌ST分型主要为ST11型(68.18%,15/22),阴沟肠杆菌ST分型主要为ST97型(26.09%,6/23),9株从患者所处环境中分离出的CRE与临床菌株的ST型一致。结论青海省5家医院分离的CRE耐药率普遍较高,主要以阴沟肠杆菌和肺炎克雷伯菌为主,碳青霉烯酶基因以blaNDM和blaKPC为主,耐药问题严重,临床应加强CRE的筛查及控制,预防其在院内传播。

CRAB的耐药性分析与OXA-51和OXA-23型碳氢酶烯酶检测在临床中的应用

目的分析该院分离的耐碳青霉烯酶鲍曼不动杆菌(CRAB)临床分布特点、耐药性以及blaOXA-51和blaOXA-23基因的携带情况,探讨CRAB耐药性与治疗策略,为临床合理使用抗菌药物提供依据。方法收集该院2020年3月至2021年3月期间79例疑似CRAB感染患者的临床资料,分别采用荧光定量PCR法(FQ-PCR)与质谱仪对菌株进行鉴定,用VITEKⅡ和纸片法检测CRAB对11种抗菌药物的耐药率。结果79株CRAB菌株标本来源主要为痰(84.8%),感染者主要来自呼吸科病房(67.1%),其次为神经外科科和神经内科科,分别占12.7%和10.1%;79份标本有46株blaOXA-51基因阳性,有48株blaOXA-23基因阳性,有45株blaOXA-51和blaOXA-23基因均阳性。32株用培养法鉴定的鲍曼不动杆菌有30株亚胺培南为耐药,同时这些鲍曼不动杆菌表现为多重耐药,具体的耐药情况为:对头孢曲松、头孢吡肟、亚胺培南、环丙沙星、氨苄西林/舒巴坦和头孢他啶抗菌药物耐药率均高于80.0%,对头孢唑啉的耐药率高达100.0%。结论32株鲍曼不动杆菌有较高的耐药水平,提示该院鲍曼不动杆菌耐药情况严重,OXA-51和OXA-23均为主要的耐药基因型别,且两种基因型别混合感染的情况较严重。

建立一种适合本实验室快速检测产KPC酶肺炎克雷伯菌的方法

目的运用基质辅助激光解吸电离飞行时间质谱技术(MALDI-TOF MS)检测产肺炎克雷伯菌碳青霉烯酶(KPC)耐碳青霉烯类肺炎克雷伯菌(CRKP),筛选并验证其特征峰,建立一种适用于本实验室快速检测产KPC酶型CRKP的方法。方法收集临床耐碳青霉烯类肺炎克雷伯菌39株,运用PCR方法检测出其中23株产KPC酶,再采用MALDI-TOF MS技术检测KPC酶阳性CRKP菌株,得到质谱图后用Flex Analyst软件分析筛选出其中特征峰,并进行重复性实验和临床验证评估。结果综合筛选出产KPC酶CRKP最佳特征峰为m/z 6432,特征峰验证实验和重复性实验的特异性和敏感性分别为96.67%和100%。临床验证评估特异性和敏感性分别为92.31%和100%。结论利用MALDI-TOF MS技术可检出产KPC酶CRKP的最佳特征峰为m/z 6432,经实验证实该特征峰特异性和敏感性高,可为临床快速诊断和治疗产KPC酶CRKP提供理论基础。