Antibiotic susceptibility and occurrence of ESBL, IBL and MBL in Pseudomonas aeruginosa strains

The aim of this study was to evaluate the drug susceptibility of P. aeruginosa strains and to detect strains producing inducible beta-lactamases (IBL), extended-spectrum beta-lactamases (ESBL), and metallo-beta-lactamases (MBL). During 6 month (October 2005 - March 2006), 66 strains of P. aeruginosa strains were cultured from clinical specimens obtained from patients of two of hospitals in Siedlce and from patients of outpatient clinics. All the strains were identified in the automatic ATB (bio Mérieux). The susceptibility of bacteria to antibiotics was tested by standard disc diffusion method. The majority of strains were susceptible to meropenem (89.4%), piperacillin combined with tazobactam (84.8%), ciprofloxacin (84.8%) and piperacillin (83.3%). Many of our strains were resistant to carbenicillin (69.7%), mezlocillin (45.5%), gentamicin (42.4%) and netylmicin (30.3%). 6 strains (9.1%) were multidrug-resistant (MDR). Inducible beta-lactamases were detected with the use double disc method according to Sanders and Sanders. ESBL-producing strains were detected with double disc test (DDST) according to Jarlier et al. These strains were identified as ESBL-positive on the basis of the DDST were also determined using a double disc (DD) test according to Appleton. Production of metallo-beta-lactamases (MBL) was examined with the use of Etest MBL (AB Biodisk, Sweden) and the double disc test according to Arakava et al. Sixty-five IBL-producing strains (98.5% of all strains) and three strains (4.5%) with MBL activity were detected. Strains producing extended beta-lactamases (ESBL) were not found.     

Antibiotic susceptibility and occurrence of ESBL in Pseudomonas aeruginosa strains isolated from different clinical specimens

The aim of this study was to evaluate the drug susceptibility of 132 P. aeruginosa strains isolated from patients hospitalized in SPSK University Hospital in Bialystok. The isolates were obtained from clinical specimens over an 11-month period in 2001 and 2002. All the strains were identified in automatic ATB system using API 20 NE strips, and their susceptibility to antibiotics was tested by standard disc-diffusion method and agar dilution method. The minimal inhibitory concentration (MIC) was determined for five antibiotics: piperacillin, amikacin, ceftazidime, imipenem and ciprofloxacin. The majority of strains were susceptible to ceftazidime (91.7%), piperacillin combined with tazobactam (85.6%), amikacin (80.3%), meropenem and imipenem (81.8%). Many of our strains were resistant to cefotaxime (73.5%), ticarcillin (53%) and ciprofloxacin (48.5%). Also, the trial was undertaken to detect strains producing extended-spectrum beta-lactamases (ESBL) and inducible beta-lactamases (IBL) among P. aeruginosa rods isolated from different specimens. ESBL-producing strains were detected with double disc test (DDST) and combination double disc (CD) test. Clavulanate was applied as the inhibitor of these beta-lactamases. Strains producing ESBL were not found. On the other hand, as many as 127 P. aeruginosa strains (96.2%) produced inducible beta-lactamases (IBL).     

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.     

Contribution of Pseudomonas Aeruginosa strains to infections in patients of specialistic outpatients clinics of the SP ZOZ in Nidzica

The aim of this study was to examine a frequency of isolation and analysis of drug susceptibility o P. aeruginosa strains cultured from clinical specimens obtained from patients treated in specialistic outpatient clinics of the Samodzielny Publiczny Zespó? Opieki Zdrowotnej (SP ZOZ) in Nidzica durin 40 months (01. 09. 2000 - 31. 12. 2003). Ninety six P. aeruginosa strains were cultured out of 829 clinical samples collected from ambulatory patients and processed in the Bacteriological Laboratory of SP ZOZ in Nidzica during over three years. P. aeruginosa strains were isolated from 11.6% of examined specimens. The greatest number of strains (49.0%) were cultured from urine samples obtained from children. Identification of strains was performed using biochemical tests (Becton Dickinson, Emapol, bio-Merieux). Susceptibility of strains to antimicrobial agents was determined with disc diffusion method according to NCCLS recommendations. Special tests were applied to detect extended-spectrum beta-lactamases (ESBL). The most active in vitro against isolated P. aeruginosa strains was a carbapenem - imipenem. All strains were susceptible to this antibiotic. Ciprofloxacin (94.8% of susceptible strains), ceftazidime (89.6%), gentamicin (86.5%), piperacillin (84.4%) and aztreonam (76.0%) were active against the majority of P. aeruginosa strains isolated from ambulatory patients. Six strains (6.25% of all strains) producing extended--spectrum beta--lactamases (ESBL) were detected. It is alarming, that the majority of P. aeruginosa strains from outpatients were cultured out of pediatric samples (61.5%). Because of an increase in resistance and appearance of new mechanisms of resistance to antibiotics/chemotherapeutics in P. aeruginosa strains, it is necessary to monitor a drug susceptibility of these strains causing infections in ambulatory patients.     

High effectiveness of the method with cefpirome in detection of extended-spectrum beta-lactamases in different species of gram-negative bacilli

Gram-negative bacilli were examined for ESBL production by using four methods: double-disc synergy diffusion test (DDST), and three tests of combined discs with cefpodoxime, ceftazidime and cefotaxime alone and the same cephalosporins with clavulanic acid. Strains determined as ESBL-negative with all these tests were examined by using fifth method with cefpirome. 47,5% from 178 negative in other methods strains, appeared ESBL-positive in this test. The examined strains belonged to 16 different species. Most of them were Enterobacter cloaceae, Serratia marcescens, Pseudomonas aeruginosa and Acinetobacter baumanii. It seems that the combined discs method with cefpirome may be usefull for phenotypic detection of ESBL producing bacteria also in the case of strains where ESBL production is camouflaged with derepressed chromosomal AmpC beta-lactamases.     

Determination of beta-lactamase types of clinical strains of bacteria using a modified microiodometric method

The substrate profiles and sensitivity to dicloxacillin inhibition were studied in the enzymes of the clinical strains of Pseudomonas aeruginosa and the transconjugants of E. coli carrying the plasmids discovered earlier in P. aeruginosa. The study was performed with a modified microiodometric method for determination of the activity of beta-lactamases. According to the M. Richmond classification of beta-lactamases the enzymes detected in P. aeruginosa strains 4529, 5290 and 9902 may correspond to the 5th class, the enzymes of P. aeruginosa strain 8208 to the 2nd class and the beta-lactamases of the E. coli transconjugants to the 3rd class. Two different beta-lactamases were detected in P. aeruginosa strain 10294.     

In vitro activity of cefepime against ESBL-positive clinical strains of gram-negative rods

The aim of this study was to determine an in vitro activity of cefepime against ESBL-positive clinical strains of Gram-negative rods isolated from hospitalized patients. Experiments were performed with 100 ESBL-positive strains of Gram-negative rods isolated from clinical samples in 2004. Strains were identified with the use of automatic ATB Expression system and biochemical ID 32 GN tests (bioMdrieux sa). Extended-spectrum beta-lactamases (ESBLs) were detected by means of disc diffusion methods: the double-disc synergy test (DDST) and the diagnostic disc test (DD, Oxoid Ltd, UK). Susceptibility in vitro of ESBL producers to 4th generation--cefepime was determined with gradient diffusion method Etest (AB Biodisk, Solna, Sweden). MIC value of cefepime was assessed for each strain. Among 100 ESBL-producing strains, 94--belonged to enteric rods and 6--to nonfermentative rods. The greatest number of strains belonged to the species Serratia marcescens (27% of all strains) and next--to the species Enterobacter cloacae (21%). Fourteen strains were susceptible (S) in vitro to cefepime, 12--intermediately susceptible (I) and 74--resistant (R). Application of cefepime in a therapy of infections caused by ESBL-positive strains of Gram-negative rods highly susceptible in vitro to this antibiotic, should be considered.     

Occurrence of beta-lactamase types ESBL and AmpC among gram-negative rods isolated from food

The aim of the study was to isolate extended spectrum beta-laktamases (ESBL) and chromosomal beta-laktamases AmpC producing strains from food products. A total of 739 Gram-negative bacteria were tested with double disc diffusion method using cefotaxim, ceftasidim and amoxycillin with clavulanic acid. One strain producing ESBL and belonging to Stenotrophomonas maltophilia was detected from the ice cream (0.14% of all strains). From different food products a total of 14 microorganisms (1.9%) having AmpC enzymes have been isolated. They belonged to Enterobacter spp, Hafnia spp, Morganella spp, Citrobacter, Acinetobacter, and Cedecea. Appearance of strains producing beta-laktamases ESBL and AmpC among microorganism isolated from food make it necessary to monitor enzymes activity during routine microbiological control of foods.     

Drug susceptibility of Pseudomonas aeruginosa strains isolated from patients of a hospital and specialistic outpatients clinics of the SP ZOZ in Nidzica

The aim of this study was to evaluate a frequency of isolation and antimicrobial susceptibility testing (AST) of Pseudomonas aeruginosa strains cultured from clinical specimens collected from patients hospitalized in wards and specialistic outpatients clinics of a hospital in Nidzica (01. 09. 2000 -31. 12. 2003). During over three years 392 Pseudomonas aeruginosa strains were cultured from 16346 clinical samples provided to bacteriological laboratory. P. aeruginosa strains were isolated from 2.5% of examined specimens. Susceptibility of Pseudomonas aeruginosa strains to antimicrobial agents was tested. The highest in vitro activity against clinical P. aeruginosa strains demonstrated imipenem. One strain was resistant to imipenem. This strain was isolated from a patient of a surgical department. Metalo-beta-lactamase was not detected (MBL-negative strain).Twenty nine strains were ESBL producer (7.4% of all strains). The contribution of Pseudomonas aeruginosa strains to the etiology of nosoconial and ambulatory infections increases. In vitro activity of antibacterial agents against P. aeruginosa strains should be monitored during therapy of infections. Resistance to antibiotics/chemothe-rapeutics may be acquired during treatment with antibacterial agent to which P. aeruginosa strain was susceptible according to the antibiogram.     

Metallo-beta-lactamase-producing gram-negative rods isolated from inpatients and outpatients, detected using Etest MBL

The aim of presented study was to detect MBL-positive strains in a group of clinical carbapenem-resistant strains isolated from inpatients and outpatients during last four years. From the beginning of November 2001 to the end of October 2005, one hundred and four strains resistant to carbapenem antibiotics--imipenem and meropenem were cultured from clinical samples obtained from patients of the Infant Jesus Clinical Hospital Centre for Trauma Treatment in Warsaw and from patients of outpatient clinics. Strains were identified and their susceptibility to antibacterial agents was determined in the automatic ATB Expression system (bioMérieux). Resistance to imipenem and meropenem was confirmed with a disc diffusion method. Production of metallo-beta-lactamases (MBL) was examined with the use of Etest MBL (AB Biodisk, Sweden), and extended-spectrum beta-lactamases (ESBL) by means of following procedures: DDST and / or DD (four variants) (Oxoid Ltd., England). MBL-positive strains (36) were cultured in cases of infections in adult patients (35 strains) and in a child (1 strain). Majority of strains belonged to the species P. aeruginosa (27), several strains - to the species P. putida (6) and remaining strains--to P. stutzeri, A. xylosoxidans, and E. cloacae (1 strain of each species). Four strains were producers of MBL-type and ESBL-type beta-lactamases. According to our knowledge and accessible literature described strains (except one paediatric strain) are the first MBL-positive strains isolated from adult hospitalized patients and adult ambulatory patients in Poland. Additionally, MBL-positive E. cloacae strain is probably the first MBL producer isolated in Poland, which belongs to the group of enteric rods. MBL-producing strains of Gram-negative rods, detected by phenotypic Etest MBL method, will be verified with genetic procedures.     

Comparison of the results of disc diffusion methods applied for detection of ESBL-positive strains of gram-negative rods

Examinations were undertaken to compare the results of disc diffusion tests applied for detection of strains producing extended-spectrum beta-lactamases (ESBLs). A total of 120 clinical strains were used in experiments. These strains were determined as ESBL-positive on the basis of consistent results of two methods: the double disc synergy test (DDST) according to Jarlier et al. (1988) and the diagnostic disc test (DD, version CPD/CD 01) according to Appleton (1999). In the next step examined strains were analysed in two further tests, which are variants of DD method: CAZ/CD 02 test with discs containing ceftazidime and ceftazidime/clavulanic acid, and CTX/CD 03 test with the use of cefotaxime and cefotaxime/clavulanic acid discs. ESBL-positive strains first of all belonged to the species E. coli and K. pneumoniae. In the case of seven analysed strains consistent results of determinations were not obtained with the use of different disc diffusion methods. Application of several disc diffusion methods to determine ESBL-positive strains of gram-negative rods increases the probability of their proper identification.     

Susceptibility and frequency of selected groups of bacteria isolated in 2001 from patients at the Holy Cross Cancer Center

The aim of the presented study was the analysis of microbiological data obtained from patients hospitalized in The Holly Cross Cancer Center in Kielce in 2001. The frequency of important nosocomial pathogens in selected specimens and their susceptibility to antibiotics were determined. The strains were identified by using commercial tests (bioMerieux) and their antibiotic susceptibility patterns were performed by disc diffusion technique. The most prevalent bacteria were Gram-negative rods of Enterobacteriaceae family (43%), mainly Escherichia coli. Only 2.7% strains of isolated Escherichia coli isolated from clinical specimens collected from hospitalized patients were beta-lactamase--positive (ESBL+). The second important group of microorganisms were Staphylococci, followed by Enterococcus spp., Pseudomonas aeruginosa and Candida spp. About twenty eight percent of Staphylococcus aureus isolates were resistant to methicillin.     

Extended-spectrum beta-lactamases in Enterobacteriaceae: related to age and gender

The prevalence of extended-spectrum beta-lactamases producing Enterobacteriaceae (ESBLPE) among nosocomial and community acquired isolates was studied (September, 1999 - August, 2000). Nosocomial and OPD isolates (200 each) were collected from OPD and different wards of the Pakistan Institute of Medical Sciences (PIMS) Islamabad, Pakistan, and tested for the production of ESBLs using the double disc diffusion technique. The prevalence of ESBL was highest in nosocomial isolates among the patients of age group III (50-60 years) (48%) with Escherichia coli as the most prevalent organism. ESBL positive isolates were mostly reported in males (65.33%) compared to females (34.67%).     

沈阳地区铜绿假单胞菌药物敏感性测定及质粒图谱分析

目的 测定铜绿假单胞菌对22种药物的敏感性,帮助临床选择用药。并对分离株进行质粒图谱分析以了解耐药菌株的流行情况。方法 药物敏感性实验采用纸片琼脂扩散法,质粒指纹图谱分析采用碱变性法提取质粒DNA,限制性内切酶切割后进行凝胶电泳分析。结果 铜绿假单胞菌对头胞哌酮、氧派酸、丁胺卡那霉素、壮观霉素、多粘菌毒和头孢三嗪的敏感率在84％－100％之间。所有菌株对其他16种抗性素均有不同程度的耐药。质粒DNA图谱分析显示,12株被检测菌株中有11株含有质粒DNA,其中8株含有23kb质粒DNA。结论 铜绿假单胞菌对头胞哌铜、氟派酸、丁胺卡那霉素、壮观霉素、多粘菌素敏感;多数耐药菌株含23kb质粒DNA。     

Drug resistance and proticinogenic types of Proteus mirabilis isolated from urinary tract infections

Proteus mirabilis strains (88 isolates) from hospitalised patients with urinary tract infection were tested for antibiotic susceptibility, ESBL production and their ability to produce proticin or on their susceptibility to proticin. Antibiotic susceptibility test was performed by standard disc diffusion method according to NCCLS. Proticin typing was made by the standard strain set from the B. W. Senior collection. Most (59%) strains belonged to ESBL producers and were more resistant to antibiotics than ESBL-negative strains. Predominant proticin patterns among the ESBL (+) strains were: P1,2(6)/SO (23%), P1,2/SO (13.5%). Among the ESBL-negative strains more frequent were P6/SO (16.6%), P1,2/SO (13.8%) and P3,6/SO (13.8%) proticin types.     

First description of Escherichia coli producing CTX-M-15- extended spectrum - lactamases (ESBL) in outpatients from south-eastern Nigeria

ABSTRACT: We studied the presence of extended spectrum beta lactamases (ESBLs) in 44 clinical isolates of Escherichia coli collected from two university teaching hospitals in South-Eastern Nigeria. Species identification was performed by standard microbiology methods and re-confirmed by MALDI-TOF technology. Phenotypic characterization of ESBL enzymes was done by double disc synergy test and presence of ESBL genes was determined by specific PCR followed by sequencing. Transfer of plasmid DNA was carried out by transformation using E. coli DH5 alpha as recipient strain. Phenotypic characterization identified all isolates to be ESBL positive. 77% of strains were from urine, 13.6% from vaginal swabs and 9.0% from wound swabs. 63.6% were from female patients, 68% were from outpatients and 95.5% from patients younger than 30 years. All ESBL producers were positive in a PCR for blaCTX-M-1 cluster, in exemplary strains blaCTX-M-15 was found by sequencing. In all strains ISEcp1 was found upstream and ORF477 downstream of blaCTX-M. PCR for blaTEM and blaOXA-1 was positive in 93.1% of strains, whereas blaSHV was not detected, aac(6')-Ib-cr was found in 97.7% of strains. RAPD analysis revealed seven different clonal groups named A through G with the majority of the strains (65.9%) belonging to clone A. Transfer of an ESBL plasmid with co-resistance to gentamicin, kanamycin, tobramycin, doxycycline and trimethropim-sulfamethoxazole was successful in 19 (43.2%) strains. This study showed a high rate of CTX-M-1 cluster - ESBLs in South-Eastern Nigeria and further confirms the worldwide spread of CTX-M ESBL in clinical isolates. KEYWORDS: Outpatients, ESBL, CTX-M, Escherichia coli.     

ChromID ESBL选择性显色平板对产ESBLs肠杆菌科细菌筛选效果的评价

目的评价ChromID ESBL选择性显色平板对产超广谱β-内酰胺酶(ESBLs)肠杆菌科细菌的筛选效果。方法选取临床分离的371株肠杆菌科细菌进行ESBLs的检测,用ChromID ESBL选择性显色平板做筛选试验,同时用纸片确证法做确证试验,采用Kappa检验对两者结果进行一致性分析。结果两种方法对371株肠杆菌科细菌ESBLs检测的总Kappa值为0.761。ChromID ESBL选择性显色平板法的总灵敏度为95.2%,总特异度为83.5%。对大肠埃希菌、肺炎克雷伯菌、奇异变形杆菌分别统计,其Kappa值分别为0.832、0.514、0.778;ChromID ESBL选择性显色平板法对其检测灵敏度分别为95.7%、91.3%、100.0%,特异度分别87.6%、72.9%、90.9%。另外有6株大肠埃希菌在该显色平板上显非特征色。结论 ChromID ESBL选择性显色平板对产ESBLs肠杆菌科细菌的筛选效果与纸片确证法总体的一致性较好,其灵敏度和特异度较高,可应用于临床。但该显色平板对产ESBLs肺炎克雷伯菌的筛选效果与纸片确证法一致性一般,其特异度也较低;对大肠埃希菌存在一定的假阴性,对于该显色平板上生长的绿色和白色菌落需要作进一步鉴定确认。     

PER-1 is still widespread in Turkish hospitals among Pseudomonas aeruginosa and Acinetobacter spp

PER-1 type beta-lactamases were screened among ceftazidime-resistant clinical isolates of Acinetobacter spp. and Pseudomonas aeruginosa. A total of 176 non-repetitive isolates (84 Acinetobacter spp. and 92 P. aeruginosa) were collected during a three month surveillance period. Isolates were obtained from seven intensive care units of seven university hospitals. All strains were screened for bla(PER-1) alleles by PCR. Of the strains, 31% and 55.4% of Acinetobacter spp. and P. aeruginosa were positive for bla(PER-1) type genes, respectively.     

Resistance pattern of extended-spectrum beta-lactamase producing Enterobacteriaceae isolates

Gram-negative pathogens harboring extended-spectrum beta-lactamases (ESBL) are becoming an increasing therapeutic problem in many wards. The aim of our work was to study ESBL production by Enterobacteriaceae strains from Eastern Romania and their antimicrobial resistance. We selected 54 clinical isolates among 1068 enterobacteria according to their susceptibility spectrum (National Committee for Clinical Laboratory Standards, 1999). Antimicrobial susceptibility tests were performed using the Rapid ATB E gallery of mini API system (BioMérieux) and by a macrodilution method in Mueller-Hinton agar following standard procedure of the National Committee for Clinical Laboratory Standards (NCCLS). ESBL production was established by using both double disk synergy test (DDT) and Expert computer program of mini API. The isoelectric point (pI) was determined by isoelectric focusing in polyacrylamide gel and revealed by nitrocefin. As references we used beta-lactamases with known pI. The Expert computer program of mini API confirms the positive DDT test for all selected strains. Almost all strains displayed resistance to ampicillin, ampicillin/sulbactam or third generation cephalosporins and aztreonam. By IEF we identified 51 strains which have a unique enzyme. IEF pattern showed presence of two enzymes in three Escherichia coli strains. According to our results, the ESBL TEM-type are the most common for the studied isolates. The production of extended-spectrum beta-lactamases and the presence of the multiresistant of antimicrobial agents reflect, probably, the over use of third generation cephalosporins in Eastern Romania.     

ESBL-positive strains of the Bacteroides fragilis group isolated from patients at the regional hospital center in Płock (Poland)

The aim of this study was to confirm a presumptive qualification of clinical B. fragilis group strains isolated in P?ock as ESBL-positive strains and to determine some properties of these strains. Twenty four clinical strains belonging to the B. fragilis group, isolated first of all from surgical patients, were received for testing. Identification of strains was performed in the automatic ATB Expression system (bioMerieux sa, France) using biochemical API 20 A strips. Strains were tested for the production of catalase (ID Color Catalase test, bioMerieux sa) and beta-lactamase (Cefinase, BBL, Becton Dickinson, USA). Susceptibility of strains to four antimicrobial agents: clindamycin, metronidazole, amoxicillin/clavulanic acid and imipenem was determined by Etest (AB Biodisk, Sweden). ESBLs were detected with the use of two disc diffusion methods: the double-disc synergy test (DDST) according to Jarlier et al. and the diagnostic disc (DD) test according to Appleton. Seventeen of examined strains belonged to the species Bacteroides fragilis, three--to B. ovatus/thetaiotaomicron, two--to B. distasonis, one--to B. uniformis and one--to B. stercoris/eggerthii. One strain (B. uniformis) did not produce catalase, whereas all strains produced beta-lactamases. Examined strains were susceptible in vitro to metronidazole, amoxicillin/clavulanic acid and imipenem. One clindamycin-resistant strain was detected (B. fragilis). Occurrence of ESBL-type enzymes was confirmed in 22 strains of following species: B. fragilis (17 strains), B. ovatus/thetaiotaomicron (3), B. distasonis (1) and B. uniformis (1). Clinical strains of the B. fragilis group with a new mechanism of resistance to beta-lactam antibiotics appeared during last years in Poland. They produce extended-spectrum beta-lactamases (ESBLs), so they are resistant to penicillins, cephalosporins and monobactams. Monitoring of infections caused by these threatening strains in hospital patients is very important.