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Introduction: Enterobacteriaceae such as Escherichia coli and Klebsiella pneumoniae are the most prominent bacterial species resistant to almost all commonly used antibiotics. Carbapenem is one of the last resort drugs for treating such emerging multidrug-resistant bacteria. This study aimed to detect carbapenem-resistant blaNDM-1 gene in ESBL producing E. coli and K. pneumoniae isolates., Methodology: A total of 190 E. coli and 350 K. pneumoniae isolates were screened for extended spectrumβ-lactamase (ESBL), carbapenemase and metallo β-lactamase (MBL) production via double-disk synergy test (DDST), modified Hodge test and combined-disk diffusion method. The blaNDM-1 gene was detected by PCR and confirmed via Sanger sequencing method., Results: Of the 540 isolates tested, 71.8% were found to be multidrug-resistant. Overall rate of ESBL-positive isolates were 57.89% E. coli and 31.42% K. pneumoniae. Among ESBL positive isolates, 49.09% E. coli and 40% K. pneumoniae were positive for carbapenemase production whereas MBL production was detected in 29% E. coli and 22% K. pneumoniae isolates. In MBL positive isolates, (37%) E. coli and (40%) K. pneumoniae isolates harboured blaNDM-1 gene. The pair-wise DNA was aligned with the NDM-1 sequence from GenBank. The alignment score was 243 and the blast nucleotide sequencing results showed 97% sequence similarity with the sequences in GenBank for the blaNDM-1 gene., Conclusions: The blaNDM-1 gene was found to be the most prevalent in urine samples. There is a dire need to conduct screening tests in hospitals and communities to find out the exact prevalence of the blaNDM-1 spread in our population., Competing Interests: No Conflict of Interest is declared, (Copyright (c) 2021 Sohni Naeem, Hazrat Bilal, Hafsah Muhammad, Muhammad Asif Khan, Fareeha Hameed, Sher Bahadur, Tayyab Ur Rehman.)

Descriptive study conducted in order to determine the presence of the fimH and afa genes in urinary isolates of extended-spectrum beta-lactamases (ESBL) producing Escherichia coli. Isolates from project TO-06/09 of the Instituto Nacional de Salud del Niño in Lima, Peru were used. A total of 75 urinary isolates of Escherichia coli were included. Gene identification was performed by polymerase chain reaction. From the 75 isolates, 74 (98.7%) were positive for the fimH gene and 6 (8.0%) were positive for the afa gene. Virulence factors produced by the fimH and afa genes were evident in urinary isolates of ESBL producing Escherichia coli.

Biochemical assays that can identify β-lactamase activity directly from patient samples have the potential to significantly improve the treatment of bacterial infections. However, current β-lactamase probes do not have the sensitivity needed to measure β-lactam resistance directly from patient samples. Here, we report the development of an instrument-free signal amplification technology, DETECT, that connects the activity of two enzymes in series to effectively amplify the activity of β-lactamase 40 000-fold, compared to the standard β-lactamase probe nitrocefin., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Background and Aims: To examine antimicrobial resistance of commonly isolated pathogens in elderly hospitalized patients., Methods: Data regarding all clinically significant isolates from blood and urine cultures of patients admitted to a multilevel geriatric hospital during March 2015 to April 2016 were collected. Antimicrobial susceptibility testing was performed according to Clinical and Laboratory Standard Institute guidelines., Results: Escherichia coli, Proteus mirabilis, and Klebsiella pneumoniae were the most common isolates, with proportions of extended spectrum beta-lactamase positivity of 60, 40, and 61% respectively. Adjusted logistic regression models indicated that resistance of Escherichia coli to ceftriaxone [odds ratio (OR) 2.8, 95% confidence interval (CI) 1.5-5.1], ceftazidime (OR 2.8, 95% CI 1.5-5.1), ciprofloxacin (OR 2.2, 95% CI 1.2-4.0), amoxicillin/clavulanic acid (OR 2.3, 95% CI 1.2-4.3), and trimethoprim/sulfamethoxazole (OR 2.4, 95% CI 1.4-4.3) was significantly higher in skilled nursing wards than in acute geriatric wards. Resistance of Proteus mirabilis to ceftriaxone (OR 3.1, 95% CI 1.5-6.4) and Klebsiella pneumoniae to ciprofloxacin (OR 3.2, 95% CI 1.3-7.9) was significantly higher in skilled nursing wards than in acute wards., Conclusions and Discussion: Antimicrobial resistance was found to be high in a multilevel geriatric hospital, especially in skilled nursing wards. These findings call for rethinking of the empirical antimicrobial therapy and of the efforts for prevention of nosocomial infection.

Background: Prevalence of extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-E) has risen in kidney transplant (KT) patients, with no long-term data so far on graft function or survival., Methods: KT patients with ESBL-E-positive urine culture were retrospectively analyzed regarding initial adequate antimicrobial therapy, recurrent infection, transplant function, and survival compared with an ESBL-E-negative KT control cohort., Results: ESBL-E-positive KT patients (n = 93) were older (55.5 ± 16.1 vs 49.5 ± 16.8 y; P = .001), presented with higher trough levels of cyclosporine and tacrolimus (121 ± 71 vs 102 ± 32 ng/mL [P = .04]; and 7.9 ± 3.3 vs 7.0 ± 2.3 ng/mL [P = .04], respectively), higher dosages of mycophenolate (1,533 ± 670 vs 1,493 ± 436; P = .001), and more acute rejection episodes within 3 months before diagnosis (12.9% vs 0.8%; P < .0001) compared with control subjects (n = 591). Five-year patient survival was superior in control subjects compared with ESBL-E-positive patients (91.2% vs 83.5%; P = .034) but long-term graft function was similar. Hospitalization rates were higher in patients presenting with ESBL-E-related urinary tract infection (UTI) compared with control subjects with ESBL-E-negative UTI (60.3% vs 31.3%; P = .002) but 5-year graft survival was superior in patients presenting with ESBL-E-related UTI (88.6% vs 69.8%; P = .035) compared with control subjects with ESBL-E-negative UTI. Recurrence rates were similar in patients with or without ESBL-E-related UTI. Initial antibiotic treatment was adequate in 41.2% of patients presenting with ESBL-E-related urosepsis, resulting in a reevaluation of antibiotic stewardship in our clinic., Conclusions: ESBL-E detection in general was associated with higher mortality, but graft survival in patients with ESBL-E-related UTI was significantly better compared with ESBL-E-negative UTI., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Background: Production of AmpC and extended spectrum beta-lactamases among urinary isolates has created a serious problem to the successful management of the urinary tract infection. The main purpose of this study was to determine the rates of the extended spectrum beta-lactamase (ESBL) production and AmpC beta-lactamase (ABL) production among urinary isolates., Results: Among total 564 urinary isolates, 514 (91.1%) were gram negative bacilli and 50 (8.9%) were gram positive cocci. E. coli (76.1%) was the most common bacteria isolated. Staphylococcus aureus (6.7%) was the predominant gram positive bacteria isolated. 35 (6.8%) of the 514 gram negative bacilli were ESBL producers. Similarly, 14 (2.7%) of the gram negative bacilli were ABL producers. Only one isolate was ESBL and ABL co-producer. Highest rate of susceptibility of gram negative bacteria was seen toward amikacin (97.3%) followed by imipenem (94.4%). Similarly, highest rate of susceptibility among gram positive cocci was seen toward vancomycin (100%) followed by amikacin (93.5%)., Conclusions: Low rates of AmpC and extended spectrum beta-lactamases production in comparison to other previous studies were reported. On the basis of the antimicrobial susceptibility patterns of the bacteria we reported in our study, amikacin, imipenem and nitrofurantoin can be used for the preliminary treatment of urinary tract infections caused by gram negative bacteria and vancomycin and amikacin for treatment of urinary tract infections caused by gram positive bacteria.

A commercially available assay (eazyplex® SuperBug CRE) detecting the most common carbapenemase and ESBL types was evaluated directly on 50 urine samples. Eazyplex® correctly detected ESBL-encoding genes in all 30 urine samples with confirmed ESBL production (sensitivity 100%). Two specimens showed invalid and one specimen false-positive results (specificity 97.9%)., (Copyright © 2015 Elsevier B.V. All rights reserved.)

We conducted a study on molecular epidemiology and clinical implications of metallo-beta-lactamase (MBL)-producing Pseudomonas aeruginosa isolated from urine. Over a 10-year period from 2001 through 2010, a total of 92 MBL-producing P. aeruginosa urine isolates were collected from patients (one isolate per patient) who were admitted to 5 hospitals in Okayama Prefecture, Japan. When cross-infection was suspected in the hospital, pulsed-field gel electrophoresis was performed. In the resulting dendrogram of 79 MBL-producing P. aeruginosa urine isolates, no identical isolates and 7 pairs of isolates with >80% similarity were found. The biofilm-forming capabilities of 92 MBL-producing P. aeruginosa urine isolates were significantly greater than those of 92 non-MBL-producing urine isolates in a medium of modified artificial urine. The imipenem resistance transferred in 16 of 18 isolates tested, and these frequencies were in the range of 10⁻³ to 10⁻⁹. All of 18 isolates tested belonged to internationally spread sequence type 235 and had 3 gene cassettes of antimicrobial resistance genes in the class 1 integron. The strong biofilm-forming capabilities of MBL-producing P. aeruginosa urine isolates could be seriously implicated in nosocomial infections. To prevent spread of the organism and transferable genes, effective strategies to inhibit biofilm formation in medical settings are needed.

Between July 2011 and August 2011, the New Delhi metallo-beta-lactamase 1 (NDM-1) gene was detected in Klebsiella pneumoniae and Escherichia coli isolates obtained from six patients hospitalised in four healthcare facilities in northern Italy. The patient who had been hospitalised in New Delhi, India, from February to May 2011 and subsequently in the Bologna area, Italy, from May to July 2011, may have been the source of the outbreak. Our findings suggest ongoing spread of this carbapenem-resistance gene in Italy and highlight the need for intensive surveillance.

Introduction: The current increase in the incidence of urinary tract infections (UTIs) worldwide caused by extended-spectrum β-lactamase (ESBL)-producing Escherichia coli may be due to the high number of ESBL-producing Enterobacteriaceae carriers in the community. However, whether ESBL-producing bacteria can cause UTIs in carriers remains uncertain., Materials and Methods: In this study, 21 fecal carriers of ESBL-producing Enterobacteriaceae were assessed for UTIs caused by ESBL-producing E. coli. Bacterial isolates obtained from patients' urine and stool specimens were phenotypically and genotypically examined. Clonal similarities of isolates were assessed by multilocus sequence typing (MLST) and random amplified polymorphic DNA (RAPD) fingerprinting., Results: The study revealed that 9 of 21 carriers developed UTIs, and genetic analysis showed that 44% of the UTIs developed were caused by the same ESBL-producing E. coli as that found in the feces of the patients., Conclusions: The ESBL-producing E. coli in carriers can cause UTIs.

New Delhi metallo-β-lactamase-1 (NDM-1) is a recently identified metallo-β-lactamase that confers resistance to carbapenems and all other β-lactam antibiotics, with the exception of aztreonam. NDM-1 is also associated with resistance to many other classes of antibiotics. The enzyme was first identified in organisms isolated from a patient in Sweden who had previously received medical treatment in India, but it is now recognized as endemic throughout India and Pakistan and has spread worldwide. The gene encoding NDM-1 has been found predominantly in Escherichia coli and Klebsiella pneumoniae. We describe the isolation NDM-1-producing organisms from two patients in Toronto, Ontario. To the best of our knowledge, this is the first report of an organism producing NDM-1 that was locally acquired in Canada. We also discuss the evidence that NDM-1 can affect bacterial species other than E. coli and K. pneumoniae, the limited options for treatment and the difficulty laboratories face in detecting organisms that produce NDM-1.

Background: Extended-spectrum β-lactamases (ESBLs) are an increasing challenge in the treatment of urinary tract infections (UTIs), and also in the community. We aimed to investigate the characteristics of patients with UTIs due to ESBL-producing Escherichia coli and to assess the risk factors for ESBLs in community-acquired isolates., Methods: We performed a retrospective study from January 1, 2007 to December 31, 2009 at a tertiary care teaching hospital in Switzerland, comparing patients with community-acquired versus healthcare-associated UTIs due to ESBL-producing E. coli. Additionally, we investigated the antimicrobial susceptibility of these isolates., Results: A total of 123 patients were studied, of whom 79 (64%) had community-acquired and 44 (36%) had healthcare-associated UTIs. Community-acquired isolates were associated with acute uncomplicated UTIs (odds ratio [OR] 6.62, 95% confidence interval [CI] 1.83-36.5, P < 0.001). Risk factors were recurrent UTI (OR 3.04, 95% CI 1.14-9.14, P = 0.022) and female sex (OR 2.46, 95% CI 1.01-6.08). Community-acquired ESBL-producing E. coli urinary isolates showed high resistance rates to most of the currently used oral antimicrobial agents, including β-lactam antibiotics (amoxicillin-clavulanic acid, 69.6% resistance), quinolones (ciprofloxacin, 84.8% resistance; norfloxacin, 83.9% resistance), and trimethoprim-sulfamethoxazole (75.9% resistance), except for nitrofurantoin (15% resistance) and fosfomycin (0% resistance)., Conclusion: UTI due to ESBL-producing E. coli are emerging, and also in a country with low antibiotic use. Because of increasing antibiotic resistance rates of E. coli to current standard therapy and because of the resistance patterns of ESBL-producing E. coli, guidelines for the management of UTIs must be revised. Fosfomycin or nitrofurantoin are recommended for the first-line empirical oral treatment of community-acquired uncomplicated UTIs.

The importance of extended spectrum β-lactamases (ESBL) is increasing worldwide. ESBLs of the CTX-M type are on the rise in Europe, not only in the hospital environment but also in outpatients. Therefore we performed a comparative pilot study including ESBL producing Escherichia coli isolated from outpatients suffering from urinary tract infections, 28 from Innsbruck, Austria, and 34 from Bolzano, Italy. Using established PCR methods we detected in nearly 90% of ESBL producing E. coli isolates CTX-M group 1 enzymes and only a few group 2 or group 9 enzymes. bla (TEM), bla (OXA-1) and aminoacyltransferase aac(6')-lb were significantly more frequent in the Austrian region, where also bla (SHV )was found in one isolate. In 2009 the overall prevalence of ESBL in E. coli causing urinary tract infection in outpatient samples was 7.6% in a local laboratory in Innsbruck and 5% in Bolzano. Additionally, we investigated plasmid-mediated qnr genes which can contribute to quinolone resistance, qnrA was found in an AmpC producing E. coli from Innsbruck and qnrS in two ESBL producers from Bolzano. Data confirmed that ESBL-producing E. coli have emerged as important pathogens in urinary tract infections of outpatients in both regions.

Selective screening media for extended-spectrum beta-lactamase (ESBL)-producing bacteria are needed to guide antibiotic therapy and institute appropriate infection control measures. This study evaluates a selective cefpodoxime-incorporated chromogenic agar (CCA) medium for the detection of ESBLs from clinical specimens. The medium was formulated specifically for this study. For all culture-positive urine samples and wound swabs from intensive care unit (ICU) patients, CCA was compared with standard laboratory testing procedures and HPA/BSAC guidance on ESBL detection. The CCA medium was also evaluated for ESBL faecal carriage from patients on ICU and the haematology ward. These patients had no prior evidence of colonisation or infection with ESBL-producing bacteria. All ESBL isolates underwent minimum inhibitory concentration (MIC) testing to cefpodoxime. The Miles and Misra method and the ecometric methods were used to quality control the microbiological performance of the CCA medium, which proved satisfactory. A total of 750 specimens were examined (690 urines, 40 faeces, 20 wound swabs). From urine cultures, 92 suspect colonies were followed up. Eighteen were cefpodoxime-resistant on routine disc testing and all were confirmed subsequently as ESBL-positive. Conventional laboratory methods identified only two urinary ESBLs. Wound cultures revealed two suspect colonies, both of which were ESBL-positive and were also detected by routine methods. Faecal samples produced 10 suspect colonies, six of which were ESBL-positive. All ESBLs had cefpodoxime MICs >10 mg /L (75% were >256 mg/L). Thus, primary conventional culture methods cannot be relied upon to detect suspect ESBL-producing bacteria.

Objective: To detect CTX-M phenotype utilizing disc diffusion and MIC testing in Escherichia coli isolated from a tertiary care urology setting., Methods: Fifty single, non duplicate ESBL producing isolates from a tertiary care urology hospital were evaluated for the presence of CTX-M phenotype. Initially all the urinary isolates were tested for ESBL production. The isolates were identified by using API 20E galleries and screened for ESBL production by combination disc methods. Representative 4 ESBL isolates were sent to Antibiotic Resistance Monitoring and Reference Laboratory (ARMRL), Health Protection Agency, Colindale, London, UK where those were further subjected to MIC testing by agar dilution and E-test strips., Results: A total of 4 ESBL producing E. coli isolates were characterized to be CTX-M on phenotypic characterization. The overall yield of CTX-M phenotypes was 75%., Conclusion: The emergence of CTX-M from Pakistan is alarming; however, further studies are required to study the epidemiology and genetic characterization of CTX-M types of ESBLs.

We prospectively studied an accelerated phenotypic method by incorporating the double disk synergy test in the standard Kirby-Bauer disk diffusion susceptibility testing, to evaluate a protocol for the rapid detection of extended-spectrum beta-lactamases (ESBL) in urinary isolates of Escherichia coli (E. coli) and Klebsiella pneumoniae (K. pneumoniae). All ESBL-positive isolates were confirmed by the standard Clinical Laboratory Standards Institute (CLSI) confirmatory disk diffusion method. Between November 2004 and December 2005, a total of 6988 urine specimens were analyzed of which, 776 (11%) showed significant growth. They included E. coli in 577 cases (74%) and K. pneumoniae in 199 (25.6%). Of these, 63 E. coli (8%) and 15 K. pneumoniae (7.5%) were positive for ESBL by the accelerated and CLSI methods. Compared to the standard CLSI method, the accelerated method reduced the ESBL detection time from two days to one day. We conclude that the accelerated ESBL detection technique used by us in this study is a reliable and rapid method for detecting ESBL in urinary isolates of E. coli and K. pneumoniae.

Objectives: To describe the epidemiology of urinary tract infections caused by extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli., Methods: We performed three studies: a trend study (1999 to 2004) to assess the evolution and origin of ESBL-producing E. coli isolates from urine samples; a comparison of the susceptibility patterns of ESBL-producing E. coli and a random sample of non-ESBL-producing E. coli isolated in the same interval, and a retrospective chart review to determine the risk factors for acquisition of, and outcomes from, urinary tract infections caused by ESBL-producing E. coli (n = 61) compared with a random sample of non-ESBL-producing E. coli urinary tract infections (n = 61) from patients attending our institution and matched by temporal occurrence., Results: ESBL-producing E. coli significantly increased from 2 (0.20%) to 89 (5.52%) isolates per year (P value for trend = 0.000). Of the 161 patients with urinary tract infections caused by ESBL-producing E. coli, 100 (62%) were attending ambulatory health centers, and 61 (38%) were attending the hospital. ESBL-producing E. coli showed a significant reduction in the susceptibility to most antimicrobials, although carbapenems and fosfomycin retained significant activity. The chart review study showed that previous treatment with fluoroquinolones (odds ratio 12.98, 95% confidence interval 1.81 to 106.51, P = 0.017) and the presence of a urinary catheter (odds ratio 2.64, 95% confidence interval 1.01 to 6.88, P = 0.047) were independent risk factors associated with infections caused by ESBL-producing E. coli., Conclusions: ESBL-producing E. coli is a problem of increasing importance. Our study results may help physicians select appropriate antimicrobial therapy in patients suspected of having urinary tract infections caused by ESBL-producing E. coli.

Background: In this investigation, the urine samples obtained in a single oral-dose pharmacokinetic study were examined for their bactericidal activity against a range of relevant urinary tract pathogens., Methods: Six healthy volunteers received a single oral dose of ten oral antibiotics available in Croatia. Urine samples were taken every 2 h during the whole dosing interval of the particular antibiotic. The urinary bactericidal activity was tested by determination of urinary bactericidal titers., Results: All antibiotics showed a significant urinary bactericidal activity against non-extended spectrum beta-lactamase Escherichia coli and Proteus mirabilis. Fluoroquinolones displayed high and persisting levels of urinary bactericidal activity against all gram-negative bacteria and Staphylococcus saprophyticus., Conclusions: Average urinary bactericidal activity can be predicted from in vitro susceptibility testing, but we expect that there will be patients with a low level of urinary bactericidal activity.

Extended Spectrum beta-Lactamases (ESBLs) producer and multidrug resistant Klebsiella spp. are becoming a major nosocomial pathogen globally. There are no documented reports yet on the occurrence of ESBL enzymes in Klebsiella spp. species from Ethiopia. This study was undertaken to isolate and determine the occurrence of ESBLs and multi-drug resistant Klebsiella spp. in different clinical samples obtained from patients. A cross-sectional survey was conducted in four different hospitals of Harar region (Hiwot Fana, Misrak-Arbegnoch, Police and Army) from December 2003 to February 2004. Three hundred and eighty four clinical specimens (202 sputum, 164 urine and 18 pus) were collected from patients admitted in different wards. Antimicrobial susceptibilities were performed on 57 clinical isolates by standard disk diffusion procedures against eight antimicrobial agents. The ESBLs detection was made by using cefotaxime and ceftazidime alone and in combination with clavulanate. A total of 57 (15%) Klebsiella spp. were isolated from 384 patients. Of the 57 isolates, 33 (58%) were from sputum, 18 (31.5%) from urine and 6 (10.5%) from pus. Of the 57 Klebsiella spp., 54 (94.7%) were identified as K. pneumoniae and 3 (5.3%) as K. oxytoca. Resistance was found against cephalosporins [cefotaxime (39.0%), cefoxitin (39.0%), ceftazidime (40.0%), ceftriaxone (40.0%), cephalothin (42.0%)], chloramphenicol (70.0%), gentamicin (61.0%) and trimethoprim-sulphamethoxazole (65.0%). Analyzed Klebsiella isolates were characterized also by a high degree of multi-resistance (67.0%). In 19/57 (33.3%) of the Klebsiella isolates, ESBL production was detected. Rates of detection of ESBL producers were 42.1, 26.3, 26.3 and 5.3% in Hiwot-Fana, Misrak-Arbegnoch, Police and Army hospitals, respectively. Multi-drug resistant isolates were more prevalent among the ESBLs producers (95.0%) than non-producers (53.0%) (p=0.24). In conclusion, our results show that awareness of ESBL production by Klebsiella spp. is clinically important. In the absence of infection control measures, ESBL producing organisms readily pass horizontally from patient to patient. These strains also transiently colonize the hands of hospital staff members, thereby facilitating patient-to-patient transmission of the organism.

Objective: To compare double disc approximation and combined disc method for their ability to detect extended spectrum b lactamase (ESBL) production in enterobacteriaceae and determine the percentage of isolates which are falsely reported as sensitive in absence of ESBL detection, in a clinical microbiology laboratory of a tertiary care hospital between September-October 2002., Methods: Selected isolates were identified according to standard biochemical tests. Disc susceptibility tests were performed according to NCCLS. ESBL detection by combined disc [cefotaxime (30 ug) versus cefotaxime plus clavulanate (30+10 ug)] was compared with detection using double discs [amoxy-clavulanic acid (20+10 ug) and aztreonam (30 ug) applied 10 mm apart]. Results were interpreted according to NCCLS and analysed on SPSS version 10., Results: ESBL production was detected in 140 (30%) isolates by combined disc method and 139 (29.5%) by double disc method. There was no significant difference between two methods. Of the ESBL positive isolates 41 (29%) gave zone diameters that were within the sensitivity range cutoff and would have been falsely reported as being beta lactam sensitive in absence of ESBL detection., Conclusion: ESBL detection should be routinely performed in clinical laboratories as false reporting would result in treatment failure despite in vitro sensitivity. No difference was found between the combined disc and double disc methods hence either of two could be used.

Oral amoxicillin was taken with and without clavulanic acid by normal subjects and by patients with chronic complicated urinary tract infection to examine the in vitro protective effect of clavulanic acid on amoxicillin degradation. When amoxicillin alone was taken, urinary excretion of the penicilloic acid of amoxicillin in bacteria-positive patients was higher than that in bacteria-negative patients and in normal subjects. There was no comparable change in urinary penicilloic acid excretion in the presence of clavulanic acid. There were significant in vitro protective effects of clavulanic acid on beta-lactamases in the urine.

In vitro enzymatic degradation rate of ampicillin (AB-PC) in urine of patients with complicated urinary tract infection and its protective effect of dicloxacillin (MDI-PC) was studied using a specific fluorometric assay for aminobenzylpenicilloic acid (AB-PA), which is converted from AB-PC by bacterial beta-lactamase. The results showed that average degradation rate of AB-PC in the urine of 10 patients were 12.2%, 21.5%, 34.3% and 48.2% at 15, 30, 60 and 120 minutes, respectively. While MDI-PC prevented the enzymatic transformation of AB-PC in such urinary samples and the average degradation rates at 15, 30, 60 and 120 minutes were considerably reduced to 7.7%, 12.2%, 21.6% and 32.8%, respectively. In vivo urinary excretion rate of AB-PA was compared between a total of 5 patients and 4 healthy volunteers after oral administration of 250 mg AB-PC. It was found that the patients excreted 9.1%, 10.7% and 12.7% of total dose at 0 approximately to 2 hours, 2 approximately to 4 hours, 4 approximately to 6 hours, respectively, while the average excretion rates in healthy volunteers were 1.54%, 2.88% and 7.94%, respectively. In 4 patients cross-over administration study, the combined dose of AB-PC and MDI-PC has been proved to clearly decrease the urinary excretion rate of AB-PA in 2 cases, but there was no significant difference in the average rate between the single and the combined dose.