Susceptibility and molecular mechanisms of resistance to cephalosporins of Escherichia coli strains isolated from patients with nosocomial infections

Resistance to wide spectrum of antibiotics was studied and most widespread genetic determinants of resistance to beta-lactam antibiotics were revealed. Susceptibility testing was performed using serial broth microdilution method. Detection of class A expanded spectrum beta-lactamases genes (TEM, SHV, CTX) by polymerase-chain reaction method was performed in 90 strains. Carbapenems remained the most active antibacterial agents with respect to studied E. coli strains. Among the 3rd generation cephalosporins the lowest minimal inhibitory concentrations were observed for inhibition-protected combined agents (ceftazidime/clavulanic acid and cefoperazone/ sulbactam). Alone or in various combinations TEM, SHV, and CTX types of beta-lactamases were found in 58.9%, 14.4%, and 77.8% of strains. Combinations of 2 determinants were detected in 55.6% of the isolates, and all 3 determinants--in 5.6%. Most often E. coli was isolated in patients with urinary tract infections. Carbapenems and inhibition-protected combined 3rd generation cephalosporins are the most active agents against E. coli.     

某三甲医院2007—2011年ICU气管切开术后肺部感染患者208例临床分析

目的：探讨湖南某三甲医院重症监护病房（ICU）患者气管切开后肺部感染病原菌的类型及其耐药性,为临床经验性用药提供帮助。方法：回顾性分析ICU208例气管切开术后并发肺部感染患者的痰细菌培养及药物敏感性测定结果。结果：共分离出420株致病菌,革兰阴性菌293株,占69．76％,其中铜绿假单胞菌98株居首位;革兰阳性菌105株,占25．24％,其中金黄色葡萄球菌47株为最多;真菌占22株,占5．23％。分离出产超广谱B内酰胺酶（ESBLs）菌87株,耐甲氧西林金黄色葡萄球菌（MRSA）24株。所分离致病菌对常用抗菌药物均有不同程度的耐药,且为多重耐药。结论：ICU气管切开患者肺部感染病原菌以革兰阴性菌为主,耐药率高,临床应加强病原学监测,重视细菌的种类分布和耐药趋势,合理使用抗生素。     

Microbiological control of drug resistance of causative agents in suppurative-septic infections in newborn infants

Resistance of the main causative agents of purulent septic infections such as pneumonia, meningitis, sepsis, etc. to 11 chemotherapeutic drugs was studied. The pathogens were isolated from autopsies of 203 newborns who died within 1981 to 1987. Among 2978 isolates belonging to Enterobacteriaceae (2466 strains) and Pseudomonadaceae (512 strains) which constituted 88% of all the isolates, strains with multiple resistance predominated: 90% of the strains resistant to 4 or more antibiotics, 77% of the strains resistant to 6 or more antibiotics and 48% of the strains resistant to 8 or more antibiotics. The highest number of the isolates were resistant to 8 and 9 chemotherapeutics (19 and 20%, respectively). 84% of all the isolates belonged to 4 genera: Klebsiella (34%), Escherichia (21%), Serratia (14%) and Pseudomonas (15%). They were characterized by the highest resistance spectra. In all the cases massive colonization of the intestine by the strains with multiple resistance which caused purulent septic infections was observed. The most frequent variants of the drug resistance combination were determined. In the total frequency of the isolate with multiple resistance no significant differences were detected in 1981 and thereafter. In 1986-1987 the frequency of S. marcescens strains increased 3-5 times with simultaneous broadening of their drug resistance spectra. Strains of S. marcescens and K. pneumoniae with multiple drug resistance endemic for definite hospitals were detected.     

Antimicrobial susceptibility of some streptococci strains of anginosus group isolated from oral and maxillofacial infections

Streptococci strains of the anginosus group isolated from various oral and maxillofacial infections (OMF) were screened for their susceptibility to the following antimicrobial agents: benzylpenicillin, ampicillin, oxacillin, cephalothin, ceftazidime, cefotaxime, cefuroxime, erythromycin, clindamycin, tetracycline, chloramphenicol, vancomycin and trimethoprime-sulphamethoxazole. The isolates were susceptable to: clindamycin, chloramphenicol, vancomycin and all beta-lactam antibiotics, except ceftazidime to which 54.5% of the strains showed intermediate susceptibility. Intermediate susceptibility to tetracycline was found in 11.3% of the strains, whereas resistance to the same antibiotic was demonstrated in 61.4%. Resistance to erythromycin and trimethoprime-sulphamethoxazole was of 2.3% for both. In conclusion, penicillin is the drug of choice in infections caused by streptococci of the anginosus group.     

Aminoglycoside resistance rates, phenotypes, and mechanisms of Gram-negative bacteria from infected patients in upper Egypt

With the re-emergence of older antibiotics as valuable choices for treatment of serious infections, we studied the aminoglycoside resistance of Gram-negative bacteria isolated from patients with ear, urinary tract, skin, and gastrointestinal tract infections at Minia university hospital in Egypt. Escherichia coli (mainly from urinary tract and gastrointestinal tract infections) was the most prevalent isolate (28.57%), followed by Pseudomonas aeruginosa (25.7%) (mainly from ear discharge and skin infections). Isolates exhibited maximal resistance against streptomycin (83.4%), and minimal resistance against amikacin (17.7%) and intermediate degrees of resistance against neomycin, kanamycin, gentamicin, and tobramycin. Resistance to older aminoglycosides was higher than newer aminoglycosides. The most common aminoglycoside resistance phenotype was that of streptomycin resistance, present as a single phenotype or in combination, followed by kanamycin-neomycin as determined by interpretative reading. The resistant Pseudomonas aeruginosa strains were capable of producing aminoglycoside-modifying enzymes and using efflux as mechanisms of resistance. Using checkerboard titration method, the most frequently-observed outcome in combinations of aminoglycosides with β-lactams or quinolones was synergism. The most effective combination was amikacin with ciprofloxacin (100% Synergism), whereas the least effective combination was gentamicin with amoxicillin (53.3% Synergistic, 26.7% additive, and 20% indifferent FIC indices). Whereas the studied combinations were additive and indifferent against few of the tested strains, antagonism was never observed. The high resistance rates to aminoglycosides exhibited by Gram-negative bacteria in this study could be attributed to the selective pressure of aminoglycoside usage which could be controlled by successful implementation of infection control measures.     

Beta-lactamases with a wide substrate spectrum in gram negative strictly anaerobic rods

This study was performed to determine the susceptibility of the clinical strains of Gram-negative strictly anaerobic rods to newer beta-lactam antibiotics. Also, the trial was undertaken to detect strains producing extended-spectrum beta-lactamases (ESBLs) and inducible beta-lactamases (IBLs) among Bacteroides spp. and Prevotella spp. rods isolated from hospitalized patients. One hundred strains of Gram-negative, obligatory anaerobic rods were applied in the study. The strains were identified in automatic ATB system using API 20 A strips. beta-lactamase-positive strains were determined with disc nitrocefin test. ESBL-producing strains were detected with double disc test according to Jarlier et al. (1988). Clavulanate was applied as the inhibitor of these beta-lactamases (AMO/CLAV disc). ESBL-positive strains were confirmed with the use of E test (TZ/TZL strip). Inducible beta-lactamases were determined by double disc method according to Sanders and Sanders (1979). Cefoxitin was the inducer of these beta-lactamases (FOX disc). Among 93 Bacteroides spp. strains and 7 Prevotella spp. strains, 91 strains (91%) produced beta-lactamases. Two ESBL-producing strains (2%) were detected. Strains producing inducible beta-lactamases (IBL) were not found. A high activity of the examined beta-lactam antibiotics against strains of Gram-negative anaerobes was found. The majority of strains were susceptible to piperacillin (95%), piperacillin combined with tazobactam (99%), ticarcillin combined with clavulanic acid (99%), meropenem (97%) and imipenem (99%). The obtained results indicate the necessity of ESBL determination among strains of the genus Bacteroides, isolated from clinical specimens. Newer beta-lactam antibiotics, especially penicillins in combination with beta-lactamase inhibitors and carbapenems, are useful in empiric therapy of infections caused by Bacteroides spp. and Prevotella spp. anaerobic rods.     

Analysis of the etiological structure and dynamics of antibiotic resistance in the causative agents of suppurative inflammatory diseases in the patients at a large general hospital

The structure of the causative agents isolated from patients with pyoinflammatory infections in 1980-1983 was analysed. It was shown that the surgical and urological infections were mainly caused by gram-negative bacteria. The other pyoinflammatory infections were mainly due to gram-positive cocci. A relatively high frequency of the strains of gram-negative bacteria, especially among Pseudomonas spp. and Enterobacter spp., resistant to aminoglycoside antibiotics, such as gentamicin, sisomycin and tobramycin with preserved sensitivity to amikacin and netilmicin in the majority of the strains was shown. Among the beta-lactam antibiotics cephotaxim and cephalotin were most active against gram-negative bacteria and staphylococci, respectively. The majority of the antibiotic resistant strains of gram-negative bacteria had analogous structures and levels of resistance to 7-12 antibiotics which might indicate the occurrence of 1-2 resistance plasmids among the clinical strains.     

A mass-spectrometric analysis of genetic markers of S. pneumoniae resistance to beta-lactam antibiotics

Beta-lactam antibiotics remain the drugs of choice for treatment of S. pneumoniae infections in spite of growing level of resistance. The formation of S. pneumoniae resistance to these drugs is mediated by modifications of the penicillin-binding proteins (PBPs), the targets of the antibiotic action. A new approach to detection of mutations in PBP1A, 2B and 2X genes based on minisequencing reaction followed by MALDI-ToF (Matrix-Assisted Laser Desorption/Ionization Time of Flight) mass spectrometry was developed in this study. The evaluation of these mutations prevalence in clinical S. pneumoniae isolates (n = 194) with different susceptibility level to beta-lactam antibiotics was performed. Twenty-four different combinations of mutations in PBPs (genotypes) were detected. All isolates susceptible to penicillin (n = 49, MIC > or = 0.06 > or = gamma/ml) carried no mutations in all analyzed loci. For 145 S. pneumoniae isolates with reduced susceptibility to penicillin (MIC > 0.06 > or = gamma/ml) the mutations in PBPs were detected in 133 (91.7 %) cases that testify to high diagnostic sensitivity of such approach. The isolates with MIC > or = 4 > or = gamma/ml (n = 20) carried multiple mutations in all analyzed genes that confirms cumulative effects of penicillin resistance formation. However, it was not possible to associate observed mutations in PBPs genes with decrease of susceptibility to cefotaxime that allows suggesting the entire difference in molecular mechanisms of formation of resistance to penicillins and cephalosporins. The offered method of S. pneumoniae genotyping is suitable for susceptibility testing to penicillin of individual isolates and for molecular monitoring of the resistance determinants in population.     

痰液中产ESBL肺炎克雷伯菌Ⅰ、Ⅱ类整合子检测及基因分型研究

目的研究临床痰液分离的产ESBLs肺炎克雷伯菌Ⅰ、Ⅱ类整合子分布情况,并进行基因分型。方法分离临床痰液中100株产ESBLs的肺炎克雷伯菌,用WHONET 5.4分析菌株药敏情况,PCR检测整合酶Ⅰ、整合酶Ⅱ,ERIC-PCR进行基因分型。结果 100株菌对碳青霉烯类敏感率100%,对β-内酰胺类、氨基糖苷类、氟喹诺酮类多数耐药。整合酶Ⅰ检出率为60%,未检出整合酶Ⅱ。100株菌分为72个基因型。结论Ⅰ类整合子广泛存在于产ESBLS肺炎克雷伯菌中,与肺炎克雷伯菌的耐药相关,ERIC-PCR可用于临床分离肺炎克雷伯的基因分型。     

膜孔蛋白改变在鲍曼不动杆菌对亚胺培南耐药中的作用

目的 对鲍曼不动杆菌耐药情况进行分析,探索膜孔蛋白在亚胺培南耐药中的作用,为临床合理用药及控制医院感染提供依据。方法 收集非重复亚胺培南耐药鲍曼不动杆菌63株,亚胺培南敏感鲍曼不动杆菌21株,用K-B纸片法检测上述细菌对16种抗菌药物的敏感性,PCR技术检测carO和oprD膜孔蛋白基因携带情况,并采用DNASTAR软件进行序列对比,对CarO蛋白三维结构建模。结果 亚胺培南耐药鲍曼不动杆菌除对替加环素（3.2%）、头孢哌酮/舒巴坦（28.6%）和米诺环素（30.2%）耐药率低外,对其他抗菌药物耐药率均较高,而亚胺培南敏感菌对多数抗生素均较敏感。PCR扩增显示所检测菌株carO和oprD基因均阳性。进一步系列比对发现亚胺培南耐药株较敏感株carO基因存在有意义突变,蛋白质分子立体结构有明显差别。结论 亚胺培南耐药鲍曼不动杆菌耐药情况严峻,carO膜孔蛋白基因突变发挥重要作用。     

Evaluation of resistance patterns of gram-negative rods from personal clinical materials

1862 clinical specimens from neonates with infection risk factors treated in the Department of Neonatology, University of Cracow were examined. The aim of this study was to investigate the participation of clinically important Gram-negative rods in hospital infections and to check the resistance patterns of these pathogens. The strains were identified in automatic ATB system using ID 32E and ID 32GN strips with biochemical tests. The susceptibility of isolates of antibacterial agents was determined in automatic ATB system using ATB G- and ATB PSE strips. 436 strains of Gram-negative rods were cultured. 289 strains (66.3%) belonging to Entero-bacteriaceae family and 147 strains (33.7%) non-fermenting rods were isolated. Among Gram-negative aerobic fermenting rods (mainly K. pneumoniae and E. cloacae), increasing resistance to aminoglycosides and beta-lactams, due to new broad spectrum and so called inducible beta-lactamases, was observed. The contribution of non-fermenting rods, especially Pseudomonas spp. and Acinetobacter spp. to the aetiology of infections in hospitalized newborns has increased. Carbapenems and fluoroquinolones are highly active in vitro against the examined strains of multiresistant Gram-negative rods.     

Resistance of hospital Staphylococci to beta-lactam antibiotics]

Resistance of hospital Staphylococci to beta-lactam antibiotics was studied. The strains were isolated in two obstetric hospitals during an outbreak of purulent inflammatory infections in them. A modification of the "clover leaf" procedure providing elucidation of the resistance mechanism was used in the study. Development of the resistance to the beta-lactam antibiotics was shown to be mainly due the activity of beta-lactamases which makes it possible to discuss their role in the mechanism of resistance development.     

Antibiotic-resistant gram-negative bacteria in a virtually closed water reticulation system

The effect of the effluent from a chicken meat-processing plant on the antibiotic-resistant bacterial profile was investigated in an almost closed water reticulation system. Of the 273 faecal coliform isolates 256 (93%) were resistant to one or more of the eight antibiotics tested. The most prevalent isolates were for the beta-lactam antibiotics ampicillin and cephalothin followed by the sulphonamides sulphatriad and cotrimoxazole. Eleven different resistance patterns were identified with a single pattern, comprising of ampicillin-, cephalothin-, streptomycin-, sulphatriad-, cotrimoxazole- and tetracyclin-resistant isolates, dominating the meat-processing effluent. An apparent correlation was observed between the specific use of certain antibiotics and the prevalence of the corresponding resistant bacterial isolates. The drugs used to treat the occasional infections, belonging to the beta-lactam and sulphonamide group of antibiotics, seemed to have a more pronounced effect on the antibiotic-resistant bacterial profile in the primary water source than those drugs used as feed additives, oxytetracyclin and the aminoglycoside flavomycin.     

Effect of tannin extract against Pseudomonas aeruginosa producing metallo beta-lactamase

Carbapenems are the most potent beta-lactam agents with a broad-spectrum activity against Gram-negative and Gram-positive bacteria. They are stable in the presence of penicillinases and cephalosporinases. This study was focused on frequency of metallo beta- lactamase (MBL) among Pesudomonas aeruginosa strains isolated in patients with urinary tract infection, effect of tannin against PA positive strains which produced blaVIM or blaIMP and both of these genes (Species). Detection of MBL was performed by phonotypic and genotypic methods. Tannin extract was tested against P. aeruginosa producing MBL. During the study period, 240 P. aeruginosa isolates were identified. Among them 64 (26.6 percent) isolates were imipenem non-susceptible and confirmed by imipenem/EDTA. Our results revealed that the growth of blaVIM positive P. aeruginosa inhibited at 15 microg/ml concentration. The experiment repeated for blaIMP-positive P. aeruginosa and P. aeruginosa which harbored blaIMP and blaVIM, the results showed 35 microg/ml was the best concentration for inhibition of P. aeruginosa-positive blaIMP and also P. aeruginosa blaIMP and blaVIM. In conclusion, tannin was effective against P. aeruginosa producing blaVIM and blaIMP and both of them so it can be substituted with common antibiotics. The result showed significantly P. aeruginosa-harbored blaIMP was more responsible for imipenem resistance than P. aeruginosa-positive blaVIM. Interestingly, tannin was more effective against MBL-P. aeruginosa in comparison with current antibiotics.     

Annual trends in antibiotic resistance of nosocomial Acinetobacter baumannii strains and the effect of synergistic antibiotic combinations

Acinetobacter baumannii is becoming increasingly resistant to antibiotics often requiring combination therapy. Annual changes of resistance to selected antimicrobials of 150 A. baumannii strains, isolated as nosocomial pathogens between 1994 and 2000 were investigated. The synergistic effects of antimicrobials were studied using a microdilution checkerboard technique in eight selected isolates resistant to third-generation cephalosporins and beta-lactam/beta-lactamase inhibitor combinations and to at least one aminoglycoside. Rates of resistance of cefepime, ceftazidime, ampicillin/sulbactam, amikacin and ciprofloxacin (before 1996 and between 1996-2000) were 29.7% - 72.6, 37.8% - 81.4%, 35.1% - 72.6%, 8.1% - 56.6%, 5.4% - 46.0% respectively (p < 0.001 for each one). Synergy was observed in at least one of the combinations of antibiotics from seven of eight isolates (87%), no antagonism was detected with any combination. Ceftazidime-amikacin (50%) and ampicillin/sulbactam-tobramycin (50%) were the most effective combinations. Due to the effectiveness of sulbactams to Acinetobacter, ampicillin/sulbactam-tobramycin combination is recommended as the first line of choice.     

The role of bla(OXA-like carbapenemase) and their insertion sequences (ISS) in the induction of resistance against carbapenem antibiotics among Acinetobacter baumannii isolates in Tehran hospitals

This study aimed to evaluate the occurrence and dissemination of bla(OXA-like) carbapenemase genes and their insertion sequences among Acinetobacter baumannii isolates, taken from different hospitals in Tehran city and also their roles in the induction of resistance to carbapenem drugs. A total number of 100 non duplicate Acinetobacter baumannii with different origins, were isolated from patients with proved nosocomial infections at eight university hospital in Tehran city. Antimicrobial susceptibility of these strains was done by E-test against 7 antimicrobial agents according to CLSI guideline. PCR of bla(OXA-51-like), bla(OXA-23-like), bla(OXA-24-like), bla(OXA-58-like), IS(ABA-1), IS(1133) was carried out by specialized primers and then these strains were typed by REP-fingerprinting. Colistin, imipenem and meropenem were the most sensitive antibiotics against Acinetobacter baumannii isolates with 96%, 51% and 51% sensitivity respectively. All the isolates had a bla(OXA-51-like) intrinsic to these species. The rates of bla(OXA-23), 23 and 58-like were 38%, 32% and 1% respectively. Coexistence of bla(OXA-51/23/24-like) was observed among 16% of these isolates. All bla(OXA-23-like) carbapenemase genes had only one IS(ABA1). REP fingerprinting showed 5 genotypes among carbapenem resistant isolates, 16 of them being genotype A. This study emphasized on the major role of bla(OXA-like) carbapenemase, particularly bla(OXA-23-like) carbapenemase and their IS(ABA1), in the dissemination of carbapenem resistant Acinetobacter baumannii. This study confirmed a presumptive role of IS element neighboring the carbapenemase gene in the elevation of resistance to carbapenem drug among Acinetobacter baumannii isolates for the first time in Iran.     

泌尿外科住院患者泌尿系感染病原菌分布及其耐药性分析

了解泌尿外科住院患者泌尿系感染病原菌的分布及其对常用抗菌药物的耐药情况。对泌尿外科泌尿系感染住院患者的消毒中段尿培养结果进行回顾性分析,尿培养菌株的鉴定、药敏分析和统计分析采用VITEK2全自动微生物仪。3 a中泌尿外科泌尿系感染住院患者共分离到细菌1 233株,其中革兰阴性杆菌772株,占62.61%,革兰阳性球菌353株,占28.63%,真菌82株,占6.65%。菌株数居前5位的细菌依次为:大肠埃希菌、肠球菌属、洋葱伯克霍尔德菌、假丝酵母菌属和变形杆菌。分离大肠埃希菌产ESBLs率为66.18%,粪肠球菌中未发现VRE菌株,屎肠球菌VRE为0.8%。未发现对美洛培南耐药的大肠埃希菌,对肠埃希菌耐药率在10%以下的有亚胺培南、阿米卡星、哌拉西林/他唑巴坦和呋喃妥因。洋葱伯克霍尔德菌和铜绿假单胞菌对所监测的抗菌药物均有不同程度的耐药。未发现对万古霉素、替考拉宁及氨苄西林耐药的粪肠球菌。泌尿系感染的病原菌以大肠埃希菌和肠球菌为主,非发酵革兰阴性杆菌及假丝酵母菌所占比例超过20%,不容忽视,病原菌的耐药率较高,临床医生应根据尿培养和药敏试验结果合理使用抗菌药物。     

Antibiotic resistance of Lactobacillus strains]

One hundred and thirty six Lactobacillus strains isolated from poultry and 23 Lactobacillus strains isolated from long-living persons were tested for their antibiotic sensitivity. Occurrence of some type determinants of resistance to aminoglycoside antibiotics and tetracyclines in the Lactobacillus strains resistant to these antibiotics was studied. The majority of the strains from the both collections were resistant to aminoglycosides (73 and 79 per cent, respectively). The isolates from the poultry were characterized by multiple resistance. The isolates from the long-living persons were most frequently resistant to one of two antibiotics. All the tested Lactobacillus strains isolated from the long-living persons were sensitive to tetracyclines. The species composition of the isolates was different. The antibiotic-resistant strains were detected in all the species involved in the study. By hybridization of Lactobacillus colonies with the probes containing various genes of the resistance it was shown that in 14 per cent of the antibiotic-resistant strains belonging to Lactobacillus the antibiotic resistance was controlled by the genes homologous to resistance genes widely distributed in gramnegative organisms. This indicated a possible wide exchange and heterologous expression of the antibiotic resistance determinants between microorganisms of various taxonomic groups.     

某三甲医院2007-2011 年ICU 气管切开术后肺部感染患者208 例 临床分析

目的:探讨湖南某三甲医院重症监护病房(ICU)患者气管切开后肺部感染病原菌的类型及其耐药性,为临床经验性用药提供帮助。方法:回顾性分析ICU 208例气管切开术后并发肺部感染患者的痰细菌培养及药物敏感性测定结果。结果:共分离出420株致病菌,革兰阴性菌293株,占69.76%,其中铜绿假单胞菌98株居首位;革兰阳性菌105株,占25.24%,其中金黄色葡萄球菌47株为最多;真菌占22株,占5.23%。分离出产超广谱β内酰胺酶(ESBLs)菌87株,耐甲氧西林金黄色葡萄球菌(MRSA)24株。所分离致病菌对常用抗菌药物均有不同程度的耐药,且为多重耐药。结论:ICU气管切开患者肺部感染病原菌以革兰阴性菌为主,耐药率高,临床应加强病原学监测,重视细菌的种类分布和耐药趋势,合理使用抗生素。     

Taking inventory: antibacterial agents currently at or beyond phase 1

At least 18 antibacterial agents are currently undergoing clinical trials for the treatment of infections caused by susceptible and resistant bacteria. The beta-lactam class includes new parenteral carbapenems and cephalosporins with varying spectra of activities. The glycopeptides are antibiotics with in vitro activity primarily against Gram-positive bacteria, including multi-resistant strains. Three quinolones are being investigated for use against a variety of Gram-positive and respiratory Gram-negative organisms. Several other classes of antibacterial agents currently in clinical trials are represented by a glycolipodepsipeptide, a dihydrofolate reductase inhibitor, an oxazolidinone, two peptide antibiotics, a glycylcycline, and a peptide deformylase inhibitor, a member of a new antibacterial class.