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).     

Effects of a specific nutrient combination on ESBL resistance

Background and aimExtended-spectrum beta-lactamases are the main cause of resistance in Enterobacteriaceae to beta lactam antibiotics. The aim of this study was to evaluate the antimicrobial effect of EpiQuercican supplement, combined with different antimicrobial agents, on ESBL-producing isolates and determine the underlying molecular mechanism of resistance in these isolates.Materials and methodsEleven ESBL producing Enterobacteriaceae isolates were collected from Saudi Arabia hospitals between 2016 and 2017 and disk diffusion test was performed in accordance with Clinical and Laboratory Standards Institute (CLSI) guidelines to determine the susceptibility of the isolates to 5 different antibiotics in the presence of EpiQuercican supplement. Polymerase chain reaction was performed for detection of ESBL genes, and efflux pump inhibitor was used to study the mechanism of resistance in these isolates.ResultsThe best synergistic effect was obtained when the supplement was combined with carbapenems followed by 4th generation cephalosporins. Either no effect or antagonistic effect was seen with most of the isolates when the supplement was added to the 3rd generation of cephalosporins. Among the tested genes responsible for ESBL production in this study, our results indicated the predominance of TEM genes (73%) followed by CTX-M genes (9%). As for the mechanism of resistance in ESBL isolates, 4 isolates showed to use efflux pumps as their main mechanism of resistance.ConclusionThe EpiQuercican supplement showed some promising results, yet its antibacterial mechanism of action needs to be elucidated further.     

A 5-year epidemiological study of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae isolates in a medium- and long-stay neurological unit

Thirty-eight different strains of extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae (ESBL Kp), isolated from urine and pus samples of 38 patients hospitalized in a medium- and long-stay neurology department between 1 January 1992 and 31 December 1996, were analysed by antibiotic resistance phenotyping, DNA macrorestriction by pulsed-field electrophoresis and isoelectric focusing of beta-lactamases. An epidemiological survey was conducted to identify risk factors for infection by ESBL Kp in this setting. The 38 isolates were distributed into 13 antibiotypes, three of which predominated (13, six and six isolates). The DNA macrorestriction pattern identified 15 genotypes, four of which predominated (11, six, four and four isolates). A combination of the two typing methods revealed several epidemic clones that emerged consecutively. Two main types of ESBL (SHV-2 and CTX-1) were identified by isoelectric focusing, the former predominating. The case-control study showed that the length of hospital stay, degree of malnutrition and dependency, and urinary sphincter status were the main factors significantly associated with ESBL Kp isolation.     

Molecular epidemiology of nosocomial infection by extended-spectrum beta-lactamases-producing Klebsiella pneumoniae

Molecular epidemiology applied to the study of nosocomial infection has been fundamental in formulating and evaluating control methods. From patients in a level 3 Bogota hospital, Klebsiella pneumoniae samples were isolated that produced extended-spectrum beta-lactamases (ESBL). Each of 15 isolates was characterized microbiologically and by molecular characters realized by pulsed field gel electrophoresis (PFGE) and by repetitive-DNA sequences amplification (REP-PCR). Antimicrobial susceptibility and ESBL production was determined in accordance with NCCLS guidelines. The beta-lactamases were evaluated by isoelectric-focusing and PCR. Twelve (80%) of the isolates were associated with nosocomial infection; 11 of them were from intensive care units. The antibiotic susceptibility displayed 13 resistance patterns--87% presented co-resistance to amikacin, 53% to gentamicin, 33% to ciprofloxacin, 40% to cefepime, 67% to piperacillin/tazobactam, 60% to trimethoprim/sulfamethoxazole and 47% to chloranphenicol. All were sensitive to imipenem. Production of TEM and SHV beta-lactamases was detected simultaneously in most isolates by isoelectric focusing and 93.3% produced a ceftazidimase of pl 8.2 of the SHV-5 type. The 15 isolates were grouped into 11 and 12 electrophoretic patterns by PFGE and REP-PCR, respectively. The degree of genetic variability indicated an endogenous origin of the nosocomial infections.     

Occurrence of endemic plasmids causing β-lactam resistance in<Emphasis Type="Italic">Enterobacteriaceae</Emphasis> in children’s university hospital in Munich

Susceptibility of 62 clinical isolates of Enterobacteriaceae to 15 aminoglycosides, beta-lactams and fluoroquinolones was determined. The isolates originating from 3 intensive care units (neonatal, pediatric, and surgical) and the Department of Infant Internal Medicine of the Children's University Hospital City Center in Munich (Germany) were collected in August 1999, and March and October 2000. Transferability of antibiotic resistance from donors to their E. coli transconjugants was also demonstrated. The majority of isolates were resistant to ampicillin, cefoxitin, ceftriaxone, cefotaxime, ceftazidime and azthreonam but they were susceptible to cefepime, meropenem, aminoglycosides and fluoroquinolones. The occurrence of beta-lactamases and extended-spectrum beta-lactamases (ESBL) was also shown. In August 1999 75% of isolates produced beta-lactamases and 15% ESBL, in March 2000 95% of isolates produced beta-lactamases and 9% ESBL; in October 2000 all isolates produced beta-lactamases and only 5% produced ESBL. Plasmid DNA analysis in randomly chosen isolates and their transconjugants revealed the presence of plasmids ranging from 19 to 136 kb; in the majority of isolates a 120-kb plasmid was observed. Further analysis using restriction endonuclease suggested a dissemination and persistence of an endemic plasmid at all 4 wards of the large pediatric hospital in the City Center of Munich which may be responsible for resistance to beta-lactams among Enterobacteriaceae isolates.     

High presence of extended-spectrum beta-lactamases and resistance to quinolones in clinical isolates of Escherichia coli

A study was conducted to detect the presence of extended-spectrum β-lactamases (ESBLs) in 706 isolates of Escherichia coli, largely from outpatients (75.2%). The Clinical and Laboratory Standards Institute (formerly NCCLS)-recommended disk diffusion procedure was used to detect ESBL presence; the VITEK 2 system (bioMérieux, Marcy L’Etoile, France) was used to determine the susceptibility to antibiotics of clinical interest, and the ESBLs were characterized by biochemical study, determining the isoelectric point, and by molecular study with PCR. Clonal distribution was studied in eight hospital isolates. There were 115 ESBL-producing isolates (16.3%), with a predominance of CTX-M9 type (58.3%). We draw attention to the high resistance to quinolones (>70%) in CTX-M9 and SHV enzyme producing isolates and the lower aminoglycoside activity in the latter.     

Investigation of extended-spectrum beta-lactamases produced by clinical isolates of Klebsiella pneumoniae and Escherichia coli in Korea

AIMS: Isolates obtained from various regions in Korea in 2002 were identified and their susceptibility to extended-spectrum cephalosporins, monobactams and/or cephamycins was studied along with any production of extended-spectrum beta-lactamases (ESBLs). METHODS AND RESULTS: Bacteria identified by the conventional techniques and Vitek GNI card were Klebsiella pneumoniae and Escherichia coli. Using disk diffusion and double-disk synergy tests, we found that 39.2% of strains produced ESBLs. About 52% of isolates transferred resistance to ceftazidime by conjugation. Banding patterns of PCR amplification with the designed primers showed that 837- and 259-bp fragments specific to bla(TEM) genes were amplified in 63.3% of strains. 929- and 231-bp fragments (bla(SHV)), 847- and 520-bp fragments (bla(CMY)), 597- and 858-bp fragments (bla(CTX-M)) were amplified in 61.5, 17.3 and 7.7% of strains respectively. About 51.9% of strains contained more than two types of beta-lactamase genes. Especially, one strain contained bla(TEM), bla(CMY) and bla(CTX-M) genes. SIGNIFICANCE: Resistance mechanisms to beta-lactams, comprising mostly ESBL production, lead to the resistance against even recently developed beta-lactams in enterobacteria, which is now a serious threat to antibiotic therapy. The high prevalence of bla(CMY) genes and multidrug-resistant genes may also make therapeutic failure and lack of eradiation of these strains by extended-spectrum cephalosporins or cephamycins.     

Prevalence of extended-spectrum beta-lactamases produced by nosocomial isolates of Enterobacteriaceae in Trakya University Hospital,Turkey

The prevalence of extended-spectrum beta-lactamase (ESBL) production by 194 nosocomial isolates of Enterobacteriacea recovered from 1995 to 1999 was investigated. The ESBL production was determined by the double-disk synergy test and was confirmed by the E-test ESBL strip. Twenty-three isolates (21 Klebsiella pneumoniae, one Escherichia coli, one Providencia rettgeri) were found as ESBL-producers (11.8%). These isolates were also usually resistant to non-betalactam antibiotics. Most of them contained a beta-lactamase with a pI of 7.6. All the strains conjugally transferred their ESBLs to recipient E. coli. Contrary to others, ESBL-producing K. pneumoniae strains isolated in 1999 were resistant to ciprofloxacin, and had the identical plasmid profiles suggestive of an outbreak. Ciprofloxacin resistance in these strains could not be transferred. In conclusion, K. pneumoniae was the main ESBL-producing species among nosocomial isolates of Enterobacteriacae in our hospital.     

Occurrence of extended-spectrum β-lactamases among<Emphasis Type="Italic">Escherichia coli</Emphasis> isolates from hospitalized and healthy children

The prevalence of extended-spectrum beta-lactamases (ESBL) was determined among isolates of Escherichia coli (n = 63) isolated from hospitalized (43) and healthy (20) children. Ten isolates (21%) were ESBL-positive for two screening tests, the double disk-synergy test and the Oxoid Combination Disk method. One ESBL-positive isolate came from a healthy child. The transfer frequency of oxyimino-beta-lactam resistance from ESBL-producing isolates to E. coli K12 C600 recipient strain ranged from 10(-8) to 10(-5) per donor cell. Donor strains and transconjugants displayed susceptibility patterns typical of ESBL producers. They were resistant to oxyimino-beta-lactams but susceptible to clavulanic acid and carbapenems. Seven out of the 10 ESBL-positive isolates were found to produce MR/MS fimbria, which may play an important role in the colonization of the human intestinal mucosa.     

Extended-spectrum β-lactamase-conferring transferable resistance to different antimicrobial agents inEnterobacteriaceae isolated from bloodstream infections

Twenty (18.5%) out of 108 clinical isolates of the family Enterobacteriaceae responsible for bloodstream infection were extended-spectrum beta-lactamase (ESBL)-positive in two screening tests, the double disk synergy test and the Oxoid Combination Disk method. Eleven out of the 20 ESBL-positive isolates transferred oxyimino-beta-lactam resistance to E. coli K12 C600 recipient strain with a frequency of 10(-8) - 10(-1) per donor cell. PCR analysis revealed that the majority of the transconjugants (9 of 11) express CTX-M-type beta-lactamases. Donor strains and their transconjugants displayed susceptibility patterns typical of ESBL producers. They were resistant to oxyimino-beta-lactams but susceptible to clavulanic acid and carbapenems. Resistances to aminoglycosides, tetracycline and mercuric chloride were, in some cases, co-transferred with oxyimino-beta-lactam resistance, suggesting that various resistance determinants were carried by the same conjugative plasmids.     

Plasmid-encoded multidrug resistance: A case study of Salmonella and Shigella from enteric diarrhea sources among humans

Salmonellosis and shigellosis are significant and persistent causes of diarrheal diseases among humans in developing countries. With that in mind, the current study investigates the occurrence of plasmid-encoded multidrug resistances in Salmonella and Shigella from diarrheal cases among humans. The isolates were characterized by serotyping, antimicrobial-susceptibility testing, transfer experiments and curing. The extended spectrum β-lactamase (ESBL) was detected by the double disc diffusion synergy test (DDST). A significant number of the plasmid-encoded multidrug resistant (PEMDR) Salmonella and Shigella isolates were found to harbour transferable plasmid genes resistant to antibiotics like ampicillin, chloramphenicol, trimethoprim-sulfamethoxazole, ceftriaxone, cefuroxime and to a lesser extent to ciprofloxacin and ofloxacin. The conjugative R-plasmids-encoded extended-spectrum β-lactamase also showed resistances to cephalosporins (ceftriaxone and cefuroxime) and ampicillin. Curing experiments showed chromosomal resistances to varied antibiotics. The findings confirmed the presence of PEMDR in Salmonella and Shigella strains as a suitable adaptation to a changing antibiotic environment. The results therefore suggest the limited use of the commonly prescribed/or third generation cephalosporins as an empirical treatment of multidrug resistant Salmonella and Shigella because this may affect therapeutic outcomes.     

Treatment options for extended-spectrum beta-lactamase-producers

A review of antibiotic options for the treatment of infections caused by extended-spectrum beta-lactamase-producing isolates is presented. The use of the third-generation cephalosporin, cefotaxime, for infections caused by isolates producing ceftazidimase-type extended-spectrum beta-lactamases is controversial, despite in vitro susceptibility to the antibiotic in many instances. The fourth-generation cephalosporin, cefipime, although active against most extended-spectrum beta-lactamases, is reported to show a marked inoculum effect. The cephamycins, such as cefoxitin. are generally effective against Enterobacteriaceae producing TEM- and SHV-derived extended-spectrum beta-lactamases, but Klebsella pneumoniae strains are prone to cephamycin resistance as a result of porin loss. The use of beta-lactamase inhibitor combinations is variable. Sulbactam is less effective than clavulanate for the inhibition of SHV-derived extended-spectrum beta-lactamases and a marked inoculum effect has been noted, while the efficacy of tazobactam against SHV-derived extended-spectrum beta-lactamase producers is controversial. Furthermore, extended-spectrum beta-lactamases are often encoded by multi-resistant plasmids carrying genes conferring resistance to aminoglycosides, chloramphenicol, sulfonamides, trimethoprim and other antimicrobials, severely limiting even alternative therapies. Extensive susceptibility testing before the institution of antibiotic therapy is thus vital.     

Antimicrobial Resistance in Invasive Non-typhoid Salmonella from the Democratic Republic of the Congo: Emergence of Decreased Fluoroquinolone Susceptibility and Extended-spectrum Beta Lactamases

Background

Co-resistance against the first-line antibiotics ampicillin, chloramphenicol and trimethoprim/sulphamethoxazole or multidrug resistance (MDR) is common in non typhoid Salmonella (NTS). Use of alternative antibiotics, such as fluoroquinolones or third generation cephalosporins is threatened by increasing resistance, but remains poorly documented in Central-Africa.

Methodology/Principal findings

As part of a microbiological surveillance study in DR Congo, blood cultures were collected between 2007 and 2011. Isolated NTS were assessed for serotype and antimicrobial resistance including decreased ciprofloxacin susceptibility and extended-spectrum beta-lactamase (ESBL) production. In total, 233 NTS isolates (representing 23.6% of clinically significant organisms) were collected, mainly consisting of Salmonella Typhimurium (79%) and Salmonella Enteritidis (18%). The majority of NTS were isolated in the rainy season, and recovered from children ≤2 years old. MDR, decreased ciprofloxacin susceptibility, azithromycin and cefotaxime resistance were 80.7%, 4.3%, 3.0% and 2.1% respectively. ESBL production was noted in three (1.3%) isolates. Decreased ciprofloxacin susceptibility was associated with mutations in codon 87 of the gyrA gene, while ESBLs all belonged to the SHV-2a type.

Conclusions/Significance

Presence of almost full MDR among NTS isolates from blood cultures in Central Africa was confirmed. Resistance to fluoroquinolones, azithromycin and third generation cephalosporins is still low, but emerging. Increased microbiological surveillance in DR Congo is crucial for adapted antibiotic therapy and the development of treatment guidelines.     

Detection of cefotaxime-resistant CTX-M-3 in clinical isolates of<Emphasis Type="Italic">Serratia marcescens</Emphasis>

Strains of Serratia marcescens (isolated in a hospital during April and August 2000) resistant to ampicillin, chloramphenicol, trimethoprim-sulfamethoxazole, streptomycin, tetracycline, and gentamicin were characterized. Out of a total of 34 clinical isolates 6 (17.6 %) exhibited the extended spectrum beta-lactamases (ESBL) resistance; they were also resistant to cefotaxime (minimum inhibitory concentration, MIC > or = 128 microg/mL) but susceptible to imipenem (MIC < or = 0.5 microg/mL). This multidrug resistance was shown to be transferred by a conjugative plasmid. Transconjugants revealed similar MIC profiles when compared to the parental strains. Isoelectric focusing revealed one major transferable beta-lactamase (pI 8.4) which was further identified as CTX-M-3 by PCR and gene sequencing. The presence of strains with this type of ESBL showed the evolution of bla genes and their dissemination among at least three species of the family Enterobacteriaceae isolated within a single hospital. The predominance of CTX-M type enzymes found in this area of Taiwan appeared to be similar to that described in Poland.     

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.     

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%).     

广州地区不动杆菌耐药调查

目的：了解广州地区不动杆菌属的耐药情况,指导临床合理用药。方法：对广州地区12家医院1998年至2001年从临床分离的436株不动杆菌属,严格按照NCCLS规定的标准用纸片扩散法进行药敏试验。结果：对12种抗生素的耐药监测发现,不动杆菌属对亚胺培南、头孢哌酮／舒巴坦、氨苄西林／舒巴坦、替卡西林／克拉维酸和哌拉西林／三唑巴坦耐药率分别为2．8％、5．6％、14．6％、14．6％和27．0％,对其他抗生素耐药率较高。结论：本地区不动杆菌耐药现象较普遍,应引起临床高度重视。     

Prevalence of Escherichia coli strains resistance to antibiotics in wound infections and raw milk

Antibiotic-resistant Escherichia coli strains including extended-spectrum β-lactamase (ESBL) isolates are globally widespread in medical, food, and environmental sources. Some of these strains are considered the most pathogenic bacteria in humans. The present work examined the predominance of antibiotic resistance in E. coli strains in wound infections comparing with E. coli strains isolated from a raw milk as a potential source of those strains. The wound infections included abdomen, anus, arm, back, buttock, chest, foot, hand, head, leg, lung, mouth, neck, penis, thigh, toe, and vagina infections. In total, 161 and 153 isolates identified as E. coli were obtained from wound infections and raw milk, respectively. A Vitek 2 system innovated by bioMérieux, France was applied to perform the identification and susceptibility tests. The E. coli isolates that have ability to produce ESBL were detected by an ESBL panel and NO45 card (bioMérieux). Over half of the E. coli were from abdomen, back, and buttock wound infections. More than 50%of the E. coli isolates obtained from wound infections were resistant to cefazolin, ampicillin, cefuroxime, ciprofloxacin, mezlocillin, moxifloxacin, piperacillin, and tetracycline; 70% of the isolates from wound infections and 0% of the isolates from raw milk were E. coli isolates produced ESBL. The data showed that the strains resistance to multi-antibiotic and produced ESBL are more widespread among wound infections than in raw milk.     

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.     

The antimicrobial susceptibility of Escherichia coli isolated in eastern area of Romania. A surveillance study

To evaluate the resistance trends for Escherichia coli isolates during 1993-1999 period in Eastern Romania to: ampicillin (A), ampicillin-sulbactam (A/S), ceftazidime (CAZ), cefotaxime (CTA), ceftriaxone (CRO), aztreonam (AZT), ofloxacin (OF), ciprofloxacin (CIP), tetracycline (T) and chloramphenicol (C). We tested 2012 clinical isolates obtained from faeces and urine. MICs were determined by a dilution method in Mueller-Hinton agar (NCCLS guidelines). Resistance rates were analyzed using the NCCLS breakpoints for the fully susceptible category (moderately susceptible strains were classified as resistant). No significant differences were observed in susceptibility of E. coli to ampicillin and ampicillin/sulbactam in the last years. The high percentage of resistant isolates was observed in 1995 for ampicillin (89.7%). Higher incidences of resistance were detected for A, A/S, T; the addition of sulbactam restored A susceptibility only for a small percent. CAZ, CTA, CRO, AZT, OF and CIP resistance among E. coli isolates was progressively increased in the last period.