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Eight strains of an unclassified, oxidase-negative, lactose-fermenting, urease-producing, gram-negative bacillus were isolated from clinical material. With the exception of urease production, the biochemical characteristics of these organisms resembled those of Escherichia coli.
Inoculum size had only a small effect on the results for ampicillin and amoxycillin susceptibility testing of Escherichia coli. In contrast, a difference in inoculum size from 10(6) to 10(8) CFU/ml profoundly affected the results for ampicillin and amoxycillin susceptibility testing of Proteus mirabilis, causing a change from susceptibility to complete resistance. These different effects of inoculum size were observed both when susceptibility was determined by the suppression of a characteristic metabolic product analyzed by head-space gas-liquid chromatography (HS-GLC) and when it was determined by MIC testing in broth. Inoculum size affected the results for ampicillin susceptibility of P. mirabilis determined concurrently with the rapid HS-GLC urine test, because 10(8) CFU/ml may occur in urine specimens. In the rapid test, significant numbers of Escherichia, Klebsiella, Citrobacter, Proteus, Morganella, and Providencia spp. in urine specimens are detected within 4 h by HS-GLC analysis for characteristic metabolic products in cultures. Most P. mirabilis in urine specimens appeared to be ampicillin resistant in the rapid HS-GLC test but were reported to be ampicillin susceptible in hospital laboratory agar dilution tests 2 days later. However, ampicillin susceptibility results for Escherichia, Klebsiella, and Citrobacter spp. agreed with hospital laboratory reports. It was concluded that reports of ampicillin susceptibility or resistance for the commonest cause of urinary tract infections, E. coli, within 4 h of receipt of the specimen would be clinically valuable and that a provisional report of ampicillin resistance for P. mirabilis would not lead to ineffective therapy.
The occurrence of expanded-spectrum-beta-lactamase-producing strains was prospectively studied in 56 patients in an intensive care unit. Ten patients were infected or colonized; some of these patients had asymptomatic intestinal colonization. Four different expanded-spectrum beta-lactamases were identified and used as epidemiological markers to survey nosocomial infections.
The LOGIC identification system (J.D. Perry, M. Ford, N. Hjersing, and F.K. Gould, J. Clin. Pathol. 41: 1010-1012, 1988) for gram-negative rods, performed with microdilution plates instead of tubes, was evaluated for strains isolated from all tested specimens except those obtained from stools (for which a different strategy was followed). Systematically extended with the oxidase test and lactose fermentation, it proved to be very reliable and extremely simple and economical.
The occurrence of extended-spectrum beta-lactamase (ESBL)-producing isolates has increased worldwide. Fecal carriage of ESBL-producing isolates has mainly been detected in nosocomial outbreaks, and few studies have evaluated fecal carriage during nonoutbreak situations and among patients in the community. We have studied the prevalence of ESBLs in 1,239 fecal samples from 849 patients (64.1% of whom were ambulatory) in 1991 and have compared the prevalence data with those obtained in 2003 for 400 fecal samples from 386 patients (75.9% of whom were ambulatory) and 108 samples from independent healthy volunteers. Samples were diluted in saline and cultured in two MacConkey agar plates supplemented with ceftazidime (1 microg/ml) and cefotaxime (1 microg/ml), respectively. Colonies were screened (by the double-disk synergy test) for ESBL production. The clonal relatedness of all ESBL-producing isolates was determined by pulsed-field gel electrophoresis with XbaI digestion; and the ESBLs of all ESBL-producing isolates were characterized by isoelectric focusing, PCR, and sequencing. The rates of fecal carriage of ESBL-producing isolates increased significantly (P < 0.001) in both hospitalized patients and outpatients, from 0.3 and 0.7%, respectively, in 1991, to 11.8 and 5.5%, respectively, in 2003. The rate of occurrence of ESBL-producing isolates among healthy volunteers was 3.7%. All ESBL-producing isolates recovered in 2003 were nonepidemic clones of Escherichia coli. ESBL characterization revealed an increasing diversity of ESBL types: TEM-4 and CTX-M-10 were the only enzymes detected in 1991, whereas TEM-4, TEM-52, SHV-12, CTX-M-9, CTX-M-10, CTX-M-14, and a CTX-M-2-like enzyme were recovered in 2003. The ESBL-producing isolates recovered from outpatients in 2003 corresponded to a CTX-M-9-type cluster (62.5%) and SHV-12 (31.2%), whereas TEM-4 was detected only in hospitalized patients. The frequencies of coresistance in isolates recovered in 2003 were as follows: sulfonamide, 75%; tetracycline, 64.3%; streptomycin, 57.1%; quinolones, 53.5%; and trimethoprim, 50%. The increased prevalence of fecal carriage of ESBL-producing isolates during nonoutbreak situations in hospitalized patients and the establishment of these isolates in the community with coresistance to non-beta-lactam antibiotics, including quinolones, represent an opportunity for these isolates to become endemic.
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A solid-phase radioimmunoassay (RIA) procedure was compared with the indirect fluorescent antibody (IFA) test in a serological study of 76 female adults with urinary tract infections. Relative serum antibody activity was determined against patients' homologous infecting enterobacteria by RIA and IFA and against heterologous enterobacterial common antigen (Escherichia coli O14) by RIA. There was marked correlation between results of the IFA and RIA methods using the homologous system; 22 of 51 patients (43%) with pyelonephritis had significantly elevated serum antibody activity by both IFA (titers greater than or equal to 512) and RIA (binding ratio greater than or equal to 2.0) when compared with normal serum controls; three had significant antibody activity detectable by RIA only. Eighteen (72%) of 25 patients with pyelonephritis had RIA binding ratios of greater than or equal to 2.0 against their homologous bacterial isolates and the enterobacterial common antigen; an additional 6 patients had binding ratios of greater than or equal to 2.0 against the antigen only. All 25 patients with cystitis had low serum antibody levels by IFA and RIA when tested against their own isolate as well as enterobacterial common antigen. The RIA procedure was objective, quantitative, and less tedious to perform than IFA.
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Enterobacterial common antigen (ECA) has attracted considerable interest since the original publication by Kunin in 1962. In the present study we demonstrated this antigen directly in the urine from patients with urinary tract infections (UTI) elicited by enterobacteria. Sheep erythrocytes were incubated with UTI urine; this resulted in their coating with ECA, which was studied by means of hemagglutination by anti-ECA serum. Test tube hemagglutination and the more simple slide hemagglutination were employed and with both procedures similar results were obtained. Positive results were observed in 94-99% of urine specimens from enterobacterial UTI collected in The Buffalo Children's Hospital in the 1960s. ECA in urine could also be demonstrated by hemagglutination inhibition. In this test, antibodies in anti-ECA serum were neutralized as a result of incubation of this serum with urine, and agglutination by the antiserum of sheep erythrocytes coated with a standard ECA preparation was prevented or reduced. By means of this latter test, ECA could be demonstrated in 67-88% of urine specimens from enterobacterial UTI. The possible diagnostic application of these tests has been discussed.
Our study aims to investigate and describe the epidemiology of the intestinal carriage of ESBL-PS in intensive care units of five Lebanese hospitals and to analyze the potential risk factors for the acquisition of these strains. At the same time, we intend to determine the patterns of susceptibility of these strains, exploring therefore the availability of alternative treatment. One thousand, four hundred forty-two fecal samples were collected between January 1, 2003 and March 31, 2003 from 378 patients admitted to the ICUs of five Lebanese tertiary care general hospitals located in different areas of Lebanon. ESBL production was detected by the double disk synergy test and antibiotic susceptibility of ESBL-producing strains as well as minimum inhibitory concentrations were determined. A paired case-control study was undertaken to identify risk factors for carriage of ESBL-PS. One hundred eighteen strains isolated from 72 subjects were identified as ESBL producers, including 95 (80.5%) E. coli, 16 (13.6%) Klebsiella pneumoniae, and 7 (5.6%) Enterobacter cloacae. A higher rate of multiple ESBL-PS carriage was described among these acquisition cases (21 double carriages and 3 triple carriages of ESBL-PS compared to only 1 double carriage of ESBL-PS at admission). In general, similar trends of susceptibility were observed in the different hospitals. As expected, the lowest MIC was observed with imipenem for all E. coli, Klebsiella, and Enterobacter isolates. Ciprofloxacin, followed by trimethoprim-sulfamethoxazole seem to be associated with the lowest susceptibility. In vitro susceptibility to cefoxitin for all isolates was 74.6%; more resistance was associated to ceftazidime (90.7%) than to cefotaxime (69.7%). Our data agree with other national and international reports showing the increase in ESBL-PS carriage in ICU patients. They demonstrate the endemic character of this carriage in Lebanese hospitals and the important risk factors including immunosuppression and evidence of ESBL infection. The highly resistant profile of ESBL-PS to antimicrobial agents available for treatment reflects the severity of this issue. The significance of this study resides in the direct correlation between our results and the nationwide increase in multi-drug resistant bacteria and the continuous change in bacterial resistance epidemiology. Our data may have an important impact on infection control policies in hospitals and on treatment of infectious diseases.
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In a hematology unit in the Netherlands, the incidence of ciprofloxacin-resistant Enterobacter cloacae and Escherichia coli increased from from 1996 to 1999. Clonal spread of single genotypes of both ciprofloxacin-resistant E. coli and Enterobacter cloacae from patient to patient was documented by pulsed-field gel electrophoresis and random amplification of polymorphic DNA. In addition, genetically heterogeneous strains were isolated regularly. Integrons associated with gentamicin resistance were detected in Enterobacter cloacae and E. coli strains. Integron-containing E. coli were detected in all hematology wards. In contrast, in Enterobacter cloacae strains two integron types were encountered only in the isolates from one ward. Although in all patients identical antibiotic regimens were used for selective decontamination, we documented clear differences with respect to the nosocomial emergence of ciprofloxacin-resistant bacterial strains and gentamicin resistance-associated integrons.
The Public Health Laboratory Service receives antibiotic susceptibility data for bacteria from bloodstream infections from most hospitals in England and Wales. These data were used to ascertain resistance trends to ciprofloxacin from 1990 through 1999 for the most prevalent gram-negative agents: Escherichia coli, Klebsiella spp., Enterobacter spp., and Proteus mirabilis. Significant increases in resistance were observed for all four species groups. For E. coli, ciprofloxacin resistance rose from 0.8% in 1990 to 3.7% in 1999 and became widely scattered among reporting hospitals. The prevalence of resistance in Klebsiella spp. rose from 3.5% in 1990, to 9.5% in 1996 and 7.1% in 1999, while that in Enterobacter spp. rose from 2.1% in 1990 to 10.5% in 1996 and 10.9% in 1999. For both Klebsiella and Enterobacter spp., most resistance was localized in a few centers. Resistance was infrequent and scattered in P. mirabilis, but reached a prevalence of 3.3% in 1999.
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OBJECTIVES: The aim of this study was to specify the characteristics of enterobacterial urinary infections producing wide spectrum beta-lactamase (WSBL) and the management strategies for these patients infected in geriatric wards. METHODS: The prevalence, bacteriological characteristics and treatment regimens of enterobacterial urinary infections producing WSBL, diagnosed in a geriatric department of internal medicine from May 1977 to April 2001, were studied retrospectively. RESULTS: Sixty-six enterobacterial urinary infections producing WSBL were diagnosed, with 53 (80%) of them acquired in the ward. They represented 1.6% of admissions and concerned 24 men and 42 women (sex ratio: 0.57), with a mean age of 87 years. Their prevalence was of 20 in the 1st year, 11 in the 2nd, 9 in the third and 26 in the 4th year. The mean duration of hospitalization of infected patients was 4.5-fold longer (90 vs. 20 days) and the mortality rate 2-fold higher (32 vs. 14%). Enterobacter aerogenes were responsible for half (46%) of the WSBL urinary infections. The skin was invaded by enterobacteria in 67% and the feces in 57% of cases. More than one third of the urinary infections treated relapsed, and digestive decontamination was only efficient in half of the patients treated. CONCLUSION: This 4-year study emphasizes the limits of antibiotherapy in eradicating WSBL-producing enterobacteria and the fact that only the strict respect of hygiene by all caregivers (isolation of patients exhibiting WSBL and washing-disinfection of the hands between each patient) limits the incidence of such infections.