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PubMed2002

Rapid detection of phylloplane bacterium Enterobacter cloacae based on chitinase gene transformation and lytic infection by specific bacteriophages.

AIMS: To establish a rapid and efficient method for detecting Enterobacter cloacae based on chitinase gene transformation and lytic infection by virulent bacteriophages. METHODS AND RESULTS: A phylloplane strain of E. cloacae was isolated from tomato leaves and transformed with a chitinase gene. Transformed bacteria were collected from single colonies and infected with newly isolated, virulent bacteriophages in the presence of the chitinase substrate 4-methylumbelliferon (4MU)-(GlcNac)3. To assay chitinase activity in the lysates, the product 4MU was measured spectrofluorophotometrically or visibly detected under u.v. irradiation. Chitinase gene-transformed bacteria obtained from single colonies could be specifically identified in 30 min by the emission of 4MU fluorescence following lysis caused by phage infection. CONCLUSIONS: The chitinase gene was used as a reporter gene to construct a new system for easy and rapid monitoring of transgenic strains of E. cloacae released in the environment, in combination with specific recognition by virulent bacteriophages. SIGNIFICANCE AND IMPACT OF THE STUDY: The assay is simple, rapid, inexpensive, easy to perform and applicable to other strains. The system can be used for the routine monitoring of bacteria, which is important because of the increased use of transgenic strains of E. cloacae as an antagonistic biological control agent for plant diseases.

Bacteriophage Typing↗
PubMed2000

Enterobacter cloacae sepsis outbreak in a newborn unit caused by contaminated total parenteral nutrition solution.

OBJECTIVE: The study aimed to investigate an outbreak caused by Enterobacter cloacae in a neonate intensive care unit. DESIGN: A descriptive study of an outbreak of sepsis in high-risk neonates was used. SETTING: The study was set in a tertiary care university teaching hospital. PATIENTS: The patients were 11 neonates infected with Enterobacter cloacae whose symptoms and signs of sepsis developed during a 16-hour period. All but one neonate received parenteral nutrition. Isolates from blood cultures, in-use parenteral nutrition solutions, and control aliquots of parenteral nutrition solution were typed by pulsed-field gel electrophoresis. RESULTS: Enterobacter cloacae was found in the refrigerated aliquots of parenteral nutrition solution, in blood cultures from infected newborns, and from in-use parenteral nutrition solutions. All these strains of Enterobacter cloacae had the same antibiotic susceptibility pattern and the same genomic DNA profile. The strain isolated from the one patient who did not receive parenteral nutrition presented a different susceptibility profile and genotype. CONCLUSION: The source of the nosocomial sepsis was the parenteral nutrition solution in 10 neonates. This contamination apparently occurred during preparation of the parenteral solution.

Disease Outbreaks↗
PubMed2000

Enterobacter cloacae bloodstream infections traced to contaminated human albumin.

In August 1996, a patient in Kansas developed an Enterobacter cloacae bloodstream infection (BSI) shortly after receiving Albuminar, a brand of human albumin. Albuminar contamination was suspected. A case-control study of patients with primary gram-negative bacterial BSIs showed that patients with E. cloacae BSIs were significantly more likely than patients with non-E. cloacae gram-negative BSIs to have received Albuminar within 3 days of developing their BSIs (3 of 5 vs. 0 of 9; OR, undefined; P=.03). The E. cloacae isolate from the Kansas patient was found by pulsed-field gel electrophoresis to be identical to the isolate from the patient's Albuminar vial, to isolates from 2 previously unopened Albuminar vials, and to an isolate from a Wisconsin patient who had received Albuminar. A worldwide recall of approximately 116,000 Albuminar vials took place. This multistate outbreak was detected because of clinical astuteness and prompt reporting. Combined epidemiological and laboratory approaches are valuable when investigating potentially contaminated blood components and plasma derivatives.

Adult↗
PubMed1992

Molecular analysis provides evidence for the endogenous origin of bacteremia and meningitis due to Enterobacter cloacae in an infant.

We analyzed the restriction fragment length polymorphism (RFLP) of total DNA and of ribosomal DNA regions (ribotyping) to document the occurrence of endogenous, systemic bacteremia and meningitis due to Enterobacter cloacae in a newborn. Five strains of E. cloacae were isolated from this newborn. Three of these strains were recovered from stool at counts of 10(8), 10(9), and 10(9) organisms/g of feces, respectively; one strain was isolated from blood; and one strain was isolated from cerebrospinal fluid. In addition, five epidemiologically unrelated strains of E. cloacae were studied for comparison. Our study clearly shows the genetic relatedness of the strains isolated sequentially from cultures of stool, blood, and cerebrospinal fluid. RFLP analysis of total DNA and ribotyping seem particularly well suited to the study of the epidemiology of nosocomial E. cloacae strains.

Bacteremia↗
PubMed1993

Effect of ampicillin versus cefuroxime on the emergence of beta-lactam resistance in faecal Enterobacter cloacae isolates from neonates.

Enterobacter cloacae strains dominated the aerobic faecal flora of 8.3% of 953 infants discharged from 32 Swedish neonatal intensive care units and the susceptibility of these strains to seven beta-lactam antibiotics was determined. Isolates from infants treated with cefuroxime showed slightly increased MICs only to ampicillin, cephalexin and cephalothin as compared to isolates from untreated infants matched for ward and time of sampling (P = 0.02). In contrast, E. cloacae isolates from ampicillin treated infants showed markedly elevated MICs of all agents tested including piperacillin, cefuroxime, cefotaxime and ceftazidime as compared to those from control neonates (P values between 0.001 for ampicillin and 0.017 for cefotaxime). Thus, E. cloacae with cefotaxime MICs as high as 512 mg/L were isolated only after ampicillin therapy. The resistant strains were negative in a colony DNA hybridization assay using gene probes for the plasmid beta-lactamases TEM-1, OXA-1 and SHV-1. The resistant strains also showed only one beta-lactamase band when crude cell sonicates were analysed by isoelectric focusing, and were not found in other infants in the same ward. The results indicate that the selection of chromosomal E. cloacae mutants, presumably with stably derepressed beta-lactamase production, in the faecal flora of neonates is rare during treatment with cefuroxime and more common during ampicillin therapy.

Ampicillin↗
PubMed1997

Detection of mutations in the gyrA and parC genes in quinolone-resistant clinical isolates of Enterobacter cloacae.

We have determined partial sequences of the gyrA and parC genes of Enterobacter cloacae type strain including the regions analogous to the quinolone resistance-determining region of the Escherichia coli gyrA gene. The deduced 65- and 49-amino acid sequences of the determined regions of the E. cloacae gyrA and parC genes were identical to the corresponding regions of the E. coli GyrA and ParC proteins, respectively. We examined 40 clinical strains of E. cloacae isolated from patients with urinary tract infection for susceptibilities to nalidixic acid and ciprofloxacin. Based on the nalidixic acid and ciprofloxacin MICs, these isolates were divided into 19 quinolone-susceptible strains (MICs of nalidixic acid, 3.13-25 mg/L; MICs of ciprofloxacin, < or = 0.025 mg/L) and 21 quinolone-resistant strains (MICs of nalidixic acid, 400 to > 800 mg/L; MICs of ciprofloxacin, 0.39-100 mg/L). We analysed five quinolone-susceptible and 21 quinolone-resistant strains for alterations in GyrA and ParC. The five quinolone-susceptible strains had amino acid sequences in GyrA and ParC identical to those of type strain. Of the 21 quinolone-resistant isolates, three (MICs of nalidixic acid, 400 to > 800 mg/L; MICs of ciprofloxacin, 0.39-3.13 mg/L) had a single amino acid change at the position equivalent to Ser-83 in the E. coli GyrA protein and no alterations in ParC; one (MIC of nalidixic acid, > 800 mg/L; MIC of ciprofloxacin, 3.13 mg/L) had a single amino acid change at Ser-83 in GyrA and a single amino acid change at the position equivalent to Glu-84 in the E. coli ParC protein; two (MIC of nalidixic acid, > 800 mg/L; MIC of ciprofloxacin, 25 mg/L) had double amino acid changes at Ser-83 and Asp-87 in GyrA and no alterations in ParC; and 15 (MICs of nalidixic acid, > 800 mg/L; MICs of ciprofloxacin, 25-100 mg/L) had double amino acid changes at Ser-83 and Asp-87 in GyrA and a single amino acid change at Ser-80 or Glu-84 in ParC. This study suggests, that in clinical isolates of E. cloacae, DNA gyrase is a primary target of quinolones, that only a single amino acid change at Ser-83 in GyrA is sufficient to generate high-level resistance to nalidixic acid and to decrease susceptibility to ciprofloxacin, and that the accumulation of amino acid changes in GyrA and the simultaneous presence of the ParC alterations play a central role in developing high-level resistance to ciprofloxacin.

Amino Acid Sequence↗
PubMed2002

Mutation of rpiA in Enterobacter cloacae decreases seed and root colonization and biocontrol of damping-off caused by Pythium ultimum on cucumber.

Strains of Enterobacter cloacae show promise as biocontrol agents for Pythium ultimum-induced damping-off on cucumber and other crops. E. cloacae A145 is a mini-Tn5 Km transposon mutant of strain 501R3 that was significantly reduced in suppression of damping-off on cucumber caused by P. ultimum. Strain A145 was deficient in colonization of cucumber, sunflower, and wheat seeds and significantly reduced in colonization of corn and cowpea seeds relative to strain 501R3. Populations of strain A145 were also significantly lower than those of strain 501R3 at all sampling times in cucumber, wheat, and sunflower rhizosphere. Populations of strain A145 were not detectable in any rhizosphere after 42 days, while populations of strain 501R3 remained at substantial levels throughout all experiments. Molecular characterization of strain A145 indicated mini-Tn5 Km was inserted in a region of the E. cloacae genome with a high degree of DNA and amino acid sequence similarity to rpiA, which encodes ribose-5-phosphate isomerase. In Escherichia coli, RpiA catalyzes the interconversion of ribose-5-phosphate and ribulose-5-phosphate and is a key enzyme in the pentose phosphate pathway. Ribose-5-phosphate isomerase activity in cell lysates from strain A145 was approximately 3.5% of that from strain 501R3. In addition, strain A145 was a ribose auxotroph, as expected for an rpiA mutant. Introduction of a 1.0-kb DNA fragment containing only the rpiA homologue into strain A145 restored ribose phosphate isomerase activity, prototrophy, seedling colonization, and disease suppression to levels similar to those associated with strain 501R3. Experiments reported here indicate a key role for rpiA and possibly the pentose phosphate pathway in suppression of damping-off and colonization of subterranean portions of plants by E. cloacae.

Cucumis sativus↗
PubMed2003

Long-term gynecological outcome of patients with persistent cloaca.

PURPOSE: Persistent cloaca is a complex malformation that remains a difficult reconstructive challenge, and data on long-term outcome are scarce. Gynecological abnormalities are common with cloaca but may remain asymptomatic until puberty or adult life. We evaluate long-term gynecological sequelae in these patients with persistent cloaca. MATERIALS AND METHODS: The records and radiographs of postpubertal patients (mean age 16.8 years, range 10 to 32) treated for cloacal malformation at 1 institution from 1970 to 2001 were retrospectively reviewed. Outcome data at puberty were available in 41 patients. Of the patients 24 are currently older than 16 years and outcome data for sexual activity were available in 21 with 3 lost to followup. RESULTS: All 41 patients were evaluated at puberty, and 28 (68%) had uterine function, 13 (32%) were menstruating normally and 15 (36%) presented with hematometra/hematocolpos. All 15 girls with an obstructed uterus required surgery, which included hysterectomy in 2, partial hysterectomy with vaginoplasty in 3 and vaginoplasty in 9. There was 1 complex case of fistula. Etiology of the obstructed uterus was vaginal stenosis after reconstruction in 3 cases, stenosis of persistent urogenital sinus (no previous reconstruction) in 11 and cervical stenosis in 1. Ten patients experienced primary amenorrhoea, which was confirmed in 8 (20%) while 2 (5%) continue to be followed for possible cryptic obstruction. In 10 girls the diagnosis of absent/vestigial uterus was made at early laparotomy but this was erroneous in 6 in whom uterine function developed at puberty. Of the 21 older girls (age at review 17 to 32 years, mean 24) 12 are or have been sexually active and 6 have been examined by a gynecologist and have an adequate vagina but are not sexually active. To date 4 patients have required revision vaginal surgery in adulthood to facilitate intercourse (re-do vaginoplasty in 3, introitoplasty in 1). One woman has postponed vaginal reconstructive procedures and 2 others are currently being followed. There have been no pregnancies in this series to date. CONCLUSIONS: Patients born with persistent cloaca have a high incidence of gynecological problems at the onset of menses and in early adult life. Therefore, it is necessary to reassess these girls at early puberty by ultrasound/magnetic resonance imaging and vaginoscopy. Additional surgery may then be necessary to create a vagina for menstruation and sexual intercourse.

Adolescent↗
PubMed1997

[Study of septicemia due to Enterobacter cloacae in a neonatal intensive care unit].

A study was made of Enterobacter cloacae septicemia in 15 newborns in the neonatal intensive care unit (NICU) of the Asahikawa Kosei Hospital from April, 1979 to March, 1996. Their gestational age was 29.7 +/- 4.5 (mean +/- SD) weeks and their birth weight was 1,270 +/- 562 g. The age at the onset of septicemia was 10.3 +/- 7.2 days. Four infants died and the mortality was 26.7%. These infants died within 72 hours after onset of septicemia. Thrombocytopenia (< 50,000/microliter) in the patients who died was significantly more than in the patients who improved (p < 0.05). Antibiotic susceptibilities were determined by the Kirby-Bauer method. Three E. cloacae strains isolated in 1982 were sensitive to ampicillin (ABPC) and cefotaxime (CTX), 4 strains between 1983 and 1984 were resistant to ABPC and were sensitive to CTX, 5 strains between 1985 and 1992 were resistant to ABPC and CTX, and 3 strains between 1993 and 1995 were resistant to ABPC and were sensitive to CTX. These results suggested that the emergence of resistant E. cloacae was related to the use of corresponding antibiotics. Our observations showed that E. cloacae was one of the potential pathogens seen in nosocomial infections which is becoming progressively common in newborns and routine bacteriological surveillance is very important in the NICU.

Bacteremia↗
PubMed1993

Fate of Enterobacter cloacae JP120 and Alcaligenes eutrophus AEO106(pRO101) in soil during water stress: effects on culturability and viability.

A sandy loam soil near field capacity moisture content (psi = -0.050 MPa) or air dried (psi = -300 MPa) was inoculated with about 3 x 10(7) CFU of Enterobacter cloacae JP120 and Alcaligenes eutrophus AEO106(pRO101) per g and incubated in 40-g portions at 17 degrees C in closed or open Erlenmeyer flasks. In the field-moist soil, selective plating, direct viable counts, and DNA hybridization showed only minor changes in the numbers of E. cloacae and A. eutrophus cells with time (14 days), and the results obtained with the three detection methods generally agreed. In the air-dried soil, the majority of both bacteria were found as intact DNA-carrying cells that were neither culturable nor viable by the methods employed in this study. The numbers of culturable E. cloacae and A. eutrophus cells dropped to 10(5) and 10(2) CFU/g, respectively, 2 h after inoculation. Direct viable counts showed that only about 1% of the cells detected by immunofluorescence microscopy were viable, but a fraction of viable nonculturable cells of both bacteria was present. A. eutrophus did not tolerate desiccation as well as E. cloacae. Only a minor fraction of the two test organisms regained their culturability or viability after rewetting of the air-dried soil; the number of total heterotrophic culturable bacteria, however, increased more than 10-fold and reached 73% of the level found in the field-moist soil at day 14.

Alcaligenes↗
PubMed1995

Characterization of rhizosphere colonization by luminescent Enterobacter cloacae at the population and single-cell levels.

A bioluminescence marker system was used to characterized colonization of the rhizosphere by a bacterial inoculum, both in terms of population activity and at the single-cell level. Plasmid pQF70/44, which contains luxAB genes under the control of a strong constitutive phage promoter, was introduced into the rhizobacterium and model biocontrol agent Enterobacter cloacae. Light output from the lux-modified strain was detected by luminometry of samples from growing cultures of E. cloacae and from inoculated soil and wheat root samples. The minimum detection limits for fully active cells under optimum conditions were 90 and 445 cells g-1 for liquid culture and soil, respectively. The metabolic activities of the lux-marked population of E. cloacae, characterized by luminometry, contrasted in rhizosphere and nonrhizosphere soil. Cells in the rhizosphere were active, and there was a linear relationship between light output and cell concentration. The activity of cells in nonrhizosphere coil could not be detected unless the soil was supplied with substrate. Novel use of a charge-coupled device is reported for the spatial characterization of rhizosphere colonization by E. cloacae (pQF70/44) at the single-cell and population levels. Used macroscopically, the charge-coupled device identified differences in colonization due to competition from indigenous soil organisms. The lux-marked bacterium was able to colonize all depths of roots in the absence of competition but was restricted tot he spermosphere in the presence of competition (nonsterile soil).(ABSTRACT TRUNCATED AT 250 WORDS)

Biomarkers↗
PubMed1998

Occurrence of virulence-associated properties in Enterobacter cloacae.

Enterobacter cloacae is not a primary human pathogen but has been considered to be an important cause of nosocomial infections. Even so, there are almost no reports on its ability to produce recognized virulence-associated properties. In this study, we show that most of the E. cloacae strains examined were resistant to serum bactericidal activity and were able to produce aerobactin and mannose-sensitive hemagglutinin, and all of them could adhere to and invade HEp-2 cells. Since E. cloacae is part of the normal intestinal floras of many individuals, we believe that infectious disease due to endogenous E. cloacae might be a result of both host predisposing factors and the bacterial virulence determinants that we have detected in this survey.

Bacterial Adhesion↗
PubMed1992

Bacteriophage lytic patterns for identification of salmonellae, shigellae, Escherichia coli, Citrobacter freundii, and Enterobacter cloacae.

A series of bacteriophages specific for Escherichia coli (E-1, E-2, E-3, and E-4), Citrobacter freundii (phi I, phi II, and phi III), Enterobacter cloacae (Ent), and Shigella spp. (Sh) have been isolated from hospital sewage. These bacteriophages, in combination with Felix Salmonella phage O-I, were used as a diagnostic phage typing set which included seven phage preparations: O-I, C (phi I and phi III), Sh, E (E-1 and E-2), CE (phi II and E-3), E-4, and Ent. After 20,280 cultures of 27 species and 9 biogroups of 15 genera of the family Enterobacteriaceae and 276 cultures of 8 species of 6 genera outside the Enterobacteriaceae were tested, it was shown that most strains of salmonellae, E. coli, C. freundii, and E. cloacae can be identified accurately. The sensitivities of identification were 83.6% for E. cloacae, 88.8% for C. freundii, 90.3% for E. coli, and 95.76% for salmonellae. The specificities were 99.78% for salmonellae, 99.84% for E. cloacae, 99.89% for E. coli, and 99.97% for C. freundii. The results of bacteriophage lytic patterns were highly correlated with Shigella serotypes. Therefore, such a phage typing set may be used routinely in public hygiene and clinical laboratories.

Bacteriophage Typing↗
PubMed2006

Extensive hospital-wide spread of a multidrug-resistant enterobacter cloacae clone, with late detection due to a variable antibiogram and frequent patient transfer.

A hospital-wide increase in the number of patients with aminoglycoside-resistant Enterobacter cloacae (AREC) isolated from clinical cultures was detected in December 2002 using a classical surveillance system (CSS). CSS refers to a strategy based on the recognition of an increased incidence of a species with a particular antibiogram at certain wards in a limited period. Since clonal spread was suspected, hospital records were reviewed for E. cloacae culture-positive patients. Based upon genotyping of 139 clinical E. cloacae isolates from 80 patients, it was concluded that 53 patients had had clinical cultures with a single AREC clone since April 2001. Determinants for unnoticed spread were investigated retrospectively, as was the possibility that a computer-assisted surveillance method would have detected this outbreak at an earlier stage. Determinants associated with late detection of clonal spread were the following: (i) the absence of a hospital-wide increase in incidence of E. cloacae cases for 1.5 years, (ii) the long time interval between cases, (iii) the hospital-wide occurrence of new cases, due to a high number of patient transfers between wards, (iv) the large variety of clinical sites, and (v) the high variability of antibiograms (n = 33). Retrospective application of a recently described computer-assisted surveillance method as well as an "in-house"-developed algorithm resulted in earlier detection of the outbreak of 6 and 12 months, respectively. These findings suggest that computerized tools for surveillance may recognize resistance trends that are too complex to be detected by manual review and indicate the need for prospective evaluation of such algorithms.

Algorithms↗
PubMed2001

Isolation and characterization of the Enterobacter cloacae cheR mutant defective in phosphate taxis.

A chemotaxis-defective mutant of Enterobacter cloacae IFO3320, designated EC1, was isolated after N-methyl-N'-nitro-N-nitrosoguanidine (NTG) mutagenesis. Computer-assisted capillary assays showed that EC1 failed to show chemotactic responses to peptone and inorganic phosphate (Pi). Cloning and sequence analysis showed that EC1 is a cheR mutant, suggesting that Pi taxis by E. cloacae is dependent on a methyl-accepting chemotaxis protein(s) (MCP). EC1 was further mutagenized with NTG to construct cheR pstS and cheR pstA double mutants. A recombinant plasmid pECT01.2, which contained the E. cloacae cheR gene, restored the ability of these double mutants to show chemotaxis toward peptone but not Pi. These results suggest that the phosphate-specific transport (Pst) system, together with a MCP(s), is required for detecting Pi in E. cloacae.

Chemotaxis↗
PubMedDate not supplied

Molecular epidemiology of a nosocomial outbreak due to Enterobacter cloacae and Enterobacter agglomerans in Campinas, São Paulo, Brazil.

A total of 73 isolates (57 Enterobacter cloacae and 16 Enterobacter agglomerans), recovered during an outbreak of bacteremia in the Campinas area, São Paulo, Brazil, were studied. Of these isolates, 61 were from parenteral nutrition solutions, 9 from blood cultures, 2 from a sealed bottle of parenteral nutrition solution, and one was of unknown origin. Of the 57 E. cloacae isolates, 54 were biotype 26, two were biotype 66 and one was non-typable. Of 39 E. cloacae isolates submitted to ribotyping, 87.2% showed the same banding pattern after cleavage with EcoRI and BamHI. No important differences were observed in the antimicrobial susceptibility patterns among E. cloacae isolates exhibiting the same biotype, serotype and ribotype. All E. agglomerans isolates, irrespective of their origin, showed same patterns when cleaved with EcoRI and BamHI. The results of this investigation suggest an intrinsic contamination of parenteral nutrition solutions and incriminate these products as a vehicle of infection in this outbreak.

Bacterial Typing Techniques↗
PubMedDate not supplied

[Resistance to cefepime in Enterobacter cloacae isolates from hospitals in Bogotá, Colombia].

OBJECTIVE: The aim of this research was to detect the presence of genes encoding beta-lactamases which can confer cefepime resistance on Enterobacter cloacae isolates, meaning that this antibiotic may be considered an important therapeutic alternative. MATERIALS AND METHODS: 28 E. cloacae isolates collected from 4 hospitals in Bogotá during 2003 were analysed. Extended spectrum beta-lactamases and cephalosporinase production were phenotypically determined. The presence of extended spectrum beta-lactamase genes was determined by PCR amplification. Mating assays were done to determine the possible transfer of bla-genes encoding cefotaximases. RESULTS: Microbiological tests detected 57% of extended-spectrum beta-lactamase-producing isolates. blaTEM, blasHv and blacTX-M genes were detected by PCR in 82% of the isolates. 7 out of 9 isolates carrying group 1 blacTX-M genes were in the resistant or intermediate range for cefepime. These isolates produced cefotaxime-resistant transconjugants. CONCLUSION: A relationship was found between resistance to cefepime and the presence of cefotaximases in E. cloacae. blacTx-M genes were present in 32% of the isolates, indicating an significant spread in the hospitals being studied. The facility of these genes' transfer between other species and Enterobacteria genera becomes an important reason for detecting them and controlling their spread in hospital settings. These results suggest a cautious use of cefepime for treating infection caused by E. cloacae strains which might produce CTX-M enzymes.

Anti-Bacterial Agents↗
PubMed2000

Effect of new quaternary bisammonium compounds on the growth and cell surface hydrophobicity of Enterobacter cloacae.

The effect of new quaternary bisammonium salts (QBAS) of series A: 1, 10-[bis(alkyldimethyl-diammonium)]-4,7-dioxo-3,8-dioxoundecandi bromides and series B: alpha-omega[bis(dodecyldimethyl-diammonium)]-3,x-dioxo-4,y- dioxoalcandibromides on the growth and surface hydrophobicity of E. cloacae strain was studied. The compounds of series A possess changing side substituent and the inhibition of growth displayed evident dependence of effect on length of alkyl with optimum at C9-C11 (cut off effect). In series B are compounds with changing joining chain between two ammonium cations where the mentioned effect was not observed. The cell surface hydrophobicity of tested strain was determined by the method of adhesion to hydrocarbon--xylene (BATH) and in salt aggregation test of ammonium sulphate (SAT). The effect of 1/4 of the MIC compounds series A with nonyl, decyl and undecyl reduced the adhesion of E. cloacae cells below 50% against the control. These compounds at sub-MICs decreased salt-aggregative ability of E. cloacae cells. The influencing of cell surface hydrophobicity was not found after affecting of compounds at sub-MIC from series B with the exception of moderate decrease at compound with joining chain of C7. The length of chain connecting two symmetrical parts of molecule has slight impact on the effect of bisammonium salts. The influence of QBAS at sub-MICs on cell surface hydrophobicity can interfere with pathogenic potential of E. cloacae.

Alkanes↗