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PubMed1985

Biochemical identification of new species and biogroups of Enterobacteriaceae isolated from clinical specimens.

In 1972 there were only 11 genera and 26 species in the family Enterobacteriaceae. Today there are 22 genera, 69 species, and 29 biogroups or Enteric Groups. This paper is a review of all of the new organisms. It has a series of differential charts to assist in identification and a large chart with the reactions of 98 different organisms for 47 tests often used in identification. A simplified version of this chart gives the most common species and tests most often used for identification. The sources of the new organisms are listed, and their role in human disease is discussed. Fourteen new groups of Enterobacteriaceae are described for the first time. These new groups are biochemically distinct from previously described species, biogroups, and Enteric Groups of Enterobacteriaceae. The new groups are Citrobacter amalonaticus biogroup 1, Klebsiella group 47 (indole positive, ornithine positive), Serratia marcescens biogroup 1, and unclassified Enteric Groups 17, 45, 57, 58, 59, 60, 63, 64, 68, and 69.

Adult↗

PubMed1991

Enterosistem 18-R: description and comparative evaluation with conventional methods for identification of members of the family Enterobacteriaceae.

The efficiency and accuracy of Enterosistem 18-R (Liofilchem s.r.l., Roseto degli Abruzzi, Teramo, Italy) were compared with those of conventional biochemical methods to identify 360 members (38 species) of the family Enterobacteriaceae. Overall, 329 strains (91.3%) were correctly identified (percentage of identification, greater than or equal to 90.0), with 37 (11.2%) requiring additional tests for complete identification. For 11 isolates (3.1%), Enterosistem 18-R gave only genus identifications, and for 14 (3.9%), the strains did not correspond to any key in the codebook and could not be identified by the manufacturer's computer service. Only six isolates (1.7%) were misidentified. The new system accurately identified common and several newly described isolates of the family Enterobacteriaceae, such as Enterobacter gergoviae, Providencia rustigianii, Serratia odorifera, and Serratia rubidaea. The system is highly reproducible, simple to perform, easy to handle, and inexpensive. With adjustments in supplementary code numbers for some strains, Enterosistem 18-R is a suitable alternative for identification of members of the Enterobacteriaceae in clinical laboratories.

Bacteriological Techniques↗

PubMed2005

Extended-spectrum-beta-lactamase-producing Enterobacteriaceae in Yaounde, Cameroon.

Organisms producing extended-spectrum beta-lactamases (ESBLs) have been reported in many countries, but there is no information on the prevalence of ESBL-producing members of the family Enterobacteriaceae in Cameroon. A total of 259 Enterobacteriaceae strains were isolated between 1995 and 1998 from patients at the Yaounde Central Hospital in Cameroon. Enterobacterial isolates resistant to extended-spectrum cephalosporin and monobactam were screened for ESBL production by the double-disk (DD) synergy test. Thirty-one (12%) of these Enterobacteriaceae strains were shown to be positive by the DD synergy test, suggesting the presence of ESBLs. Resistance to oxyimino-cephalosporins and monobactams of 12 (38.7%) of the 31 strains-i.e., 6 Klebsiella pneumoniae, 4 Escherichia coli, 1 Citrobacter freundii, and 1 Enterobacter cloacae strain-was transferred to E. coli HK-225 by conjugation. Resistance to gentamicin, gentamicin plus trimethoprim-sulfamethoxazole, or trimethoprim-sulfamethoxazole was cotransferred into 6, 2, and 1 of these transconjugants, respectively. All 12 transconjugants were resistant to amoxicillin, piperacillin, all of the cephalosporins, and aztreonam but remained susceptible to cefoxitin and imipenem. Crude extracts of beta-lactamase-producing transconjugants were able to reduce the diameters of inhibition zones around disks containing penicillins, narrow- to expanded-spectrum cephalosporins or monobactams when tested against a fully susceptible E. coli strain but had no effect on such zones around cefoxitin, imipenem, and amoxicillin-clavulanate disks. The beta-lactamases produced by the 12 tranconjugants turned out to be SHV-12 by DNA sequencing. Therefore, the ESBL SHV-12 is described for the first time in Cameroon.

Anti-Bacterial Agents↗

PubMed2000

Identification by 16S ribosomal RNA gene sequencing of an Enterobacteriaceae species from a bone marrow transplant recipient.

AIMS: To ascertain the clinical relevance of a strain of Enterobacteriaceae isolated from the stool of a bone marrow transplant recipient with diarrhoea. The isolate could not be identified to the genus level by conventional phenotypic methods and required 16S ribosomal RNA (rRNA) gene sequencing for full identification. METHODS: The isolate was investigated phenotypically by standard biochemical methods using conventional biochemical tests and two commercially available systems, the Vitek (GNI+) and API (20E) systems. Genotypically, the 16S bacterial rRNA gene was amplified by the polymerase chain reaction (PCR) and sequenced. The sequence of the PCR product was compared with known 16S rRNA gene sequences in the GenBank database by multiple sequence alignment. RESULTS: Conventional biochemical tests did not reveal a pattern resembling any known member of the Enterobacteriaceae family. The isolate was identified as Salmonella arizonae (73%) and Escherichia coli (76%) by the Vitek (GNI+) and API (20E) systems, respectively. 16S rRNA sequencing showed that there was only one base difference between the isolate and E coli K-12, but 48 and 47 base differences between the isolate and S typhimurium (NCTC 8391) and S typhi (St111), respectively, showing that it was an E coli strain. The patient did not require any specific treatment and the diarrhoea subsided spontaneously. CONCLUSIONS: 16S rRNA gene sequencing was useful in ascertaining the clinical relevance of the strain of Enterobacteriaceae isolated from the stool of the bone marrow transplant recipient with diarrhoea.

Adult↗

PubMed2002

Development of oligonucleotide primers for the specific PCR-based detection of the most frequent Enterobacteriaceae species DNA using wec gene templates.

Oligonucleotide primers were designed for the PCR-based detection of the wec gene cluster involved in the biosynthetic pathway leading to the production of enterobacterial common antigen (ECA). Escherichia coli DNA was detected using wec A, wec E, and wec F gene primers. The wec A primers were specific for E. coli. The wec E and wec F primers enabled the detection of the most frequent species of the Enterobacteriaceae found in blood and urine specimens as well as in water. The sensitivity of the assay was approximately 1.2 x 102 bacteria/mL of water. Thus, these primers represent an important step in the molecular diagnosis of major Enterobacteriaceae infections. Their role in the routine testing of contamination in drinking water and food may prove to be very useful. The DNA of Enterobacteriaceae species is detected in a first step PCR, followed by specific identification of important pathogens like E. coli O157, Shigella spp., Salmonella spp., and Yersinia spp.

Blood↗

PubMed2005

[Comparison of three microbiological methods for detection of expanded-spectrum betalactamases in Enterobacteriaceae isolated in Santa Fe (Argentina)].

INTRODUCTION: Expanded-spectrum betalactamases (ESBLs) are the main source of resistance to oxyimino cephalosporins and monobactams in Enterobacteriaceae. Most of them derive from TEM or SHV, however the incidence of other families like CTX-M, OXA and PER has increased. In Argentina, the most frequent ESBL in Enterobacteriaceae is CTX-M-2. This specific circumstance, which differs from the situation in the Northern Hemisphere, motivated us to study new diagnostic strategies for the detection of ESBLs in our region. METHOD: Microbiological ESBL detection was performed by double-disk synergy tests, cefotaxime and ceftazidime disks with and without clavulanic acid (NCCLS), and cefotaxime and ceftazidime disks in Müeller-Hinton agar supplemented with lithium clavulanate (MH-cla). Betalactamases were characterized by isoelectric focusing, hydrolysis profile and PCR amplification. RESULTS: Among 575 clinical isolates of Enterobacteriaceae, 14% were oxyimino cephalosporin-resistant. Two different ESBLs were detected in 31 resistant strains: CTX-M-2 (28) and PER-2 groups (3). The double-disk synergy test was the least sensitive method for ESBL detection. ESBLs were detected by the other two methods in all isolates with the use of cefotaxime disks, but not with ceftazidime disks. CONCLUSION: The microbiological method employing MH-cla with cefotaxime disks had a sensitivity and specificity comparable to the referral test using the same antibiotic proposed by the NCCLS for the detection of ESBLs.

Argentina↗

PubMedDate not supplied

Prevalence of extended-spectrum beta-lactamases in Enterobacteriaceae, Pseudomonas and Stenotrophomonas as determined by the VITEK 2 and E test systems in a Kuwait teaching hospital.

OBJECTIVE: To determine the prevalence of extended-spectrum beta-lactamase (ESBL)-producing members of the Enterobacteriaceae using VITEK 2 and E test systems. MATERIALS AND METHODS: A total of 3,592 consecutive gram-negative isolates (single isolate per patient) of the family of Enterobacteriaceae and Pseudomonas adjudged to be clinically relevant to the patient's infection were studied for ESBL production over a period of 1 year at Mubarak Al-Kabeer Hospital, Kuwait. Two methods were used: the automated VITEK 2 system and E test ESBL, a manually manipulated plastic strip containing various gradients of beta-lactam antibiotics. These tests and interpretative criteria for the results were performed according to the manufacturer's instructions. RESULTS: Of the 3,592 bacterial isolates, 264 (7.5%) and 185 (5.2%) were positive for ESBL production by the VITEK 2 and E test, respectively. All the ESBL-producing Pseudomonas aeruginosa identified by VITEK 2 gave indeterminate results by E test. Prevalent ESBL producers, identified by the VITEK 2 versus E test, respectively, were: Citrobacter spp. (15 vs. 3.2%), K. pneumoniae (12.2 vs. 11.4%), Enterobacter spp. (12 vs. 3%), E. coli (6.5 vs. 5.6%), P. aeruginosa (6.5 vs. 0%) and Morganella spp. (2 vs. 1%). The most common infection associated with ESBL-producing pathogens was urinary tract infection (68.2%), followed by wound infection (14.4%) and bloodstream infection (6.1%). CONCLUSION: The result of this study showed a relatively high prevalence of clinically significant ESBL producers among the Enterobacteriaceae and Pseudomonas spp. at our teaching hospital. The VITEK 2 identified a higher prevalence of ESBL strains than the E test.

Anti-Bacterial Agents↗

PubMed2026

Hypervirulence-associated pseudo-compound transposons as fundamental mobile units driving cross-species virulence dissemination in Enterobacteriaceae.

BACKGROUND: The rapid global spread of hypervirulence in Enterobacteriaceae, particularly in carbapenem-resistant Klebsiella pneumoniae, poses a significant public health threat. However, the key genetic vehicles and mechanisms driving horizontal transfer of hypervirulence-associated genes (iucA, iroB, rmpA, rmpA2, and peg-344) remain poorly defined, limiting effective surveillance. METHODS: We performed a large-scale genomic survey of 2,869 virulence-associated plasmid sequences and 2,337 complete Enterobacteriaceae chromosomes. Using comparative genomics and evolutionary analyses, we systematically identified and characterized Hypervirulence-associated Pseudo-Compound Transposons (Hva-PCTs), defined as structured mobile elements in which hypervirulence-associated genes are flanked by insertion sequences. RESULTS: Our results demonstrate that hypervirulence-associated genes are transmitted primarily as discrete IS-bounded units, which we term Hva-PCTs. We identified 29 distinct plasmid-borne Hva-PCTs (pHva-PCTs) and 30 chromosomal Hva-PCTs (cHva-PCTs). These modules show clear species-specific patterns: iucA/iroB-associated Hva-PCTs mainly originate in Escherichia coli and spread through IncFIB-containing multi-replicon plasmids (commonly combined with IncFIC(FII) and/or IncFII, while rmpA/rmpA2/peg-344-containing modules originate in K. pneumoniae and are disseminated via IncHI1B/repB plasmids. Three Hva-PCTs were detected on both plasmids and chromosomes (xHva-PCTs). In one clinical K. pneumoniae isolate (LS356), the identical composite module was present on both replicons. Simpler sub-modules, such as ISKqu3-rmpA2-iucA_1-IS102 and IS102-rmpA-peg-344-iroB_1-IS1A, frequently co-occur on the same plasmid; when positioned in tandem, they reconstitute the full composite structure. This assembly pattern is further supported by a partial duplication event in plasmid pP901. CD-HIT clustering (80% nucleotide identity and 90% coverage) showed that 13 of 22 major clusters contained both plasmid and chromosomal copies, with intra-cluster identities >80% across multiple sequence types and host species. CONCLUSION: Hypervirulence-associated genes in Enterobacteriaceae are disseminated mainly as IS-flanked Hva-PCTs rather than solely through intact virulence plasmids. These modules exhibit strong but not absolute host specificity. The presence of identical Hva-PCTs on plasmids and chromosomes suggests inter-replicon mobility, while their stepwise assembly from simpler sub-modules highlights modular accretion as a key evolutionary process. Tracking Hva-PCTs as distinct mobile units may complement existing plasmid- and gene-centric surveillance approaches for hypervirulent and convergent strains. Experimental validation of their transposition activity and phenotypic effects is still required.

Virulence↗

PubMed2004

Nursing home residents and Enterobacteriaceae resistant to third-generation cephalosporins.

Limited data identify the risk factors for infection with Enterobacteriaceae resistant to third-generation cephalosporins among residents of long-term-care facilities. Using a nested case-control study design, nursing home residents with clinical isolates of Enterobacteriaceae resistant to third-generation cephalosporins were compared to residents with isolates of Enterobacteriaceae susceptible to third-generation cephalosporins. Data were collected on antimicrobial drug exposure 10 weeks before detection of the isolates, facility-level demographics, hygiene facilities, and staffing levels. Logistic regression models were built to adjust for confounding variables. Twenty-seven case-residents were identified and compared to 85 controls. Exposure to any cephalosporin (adjusted odds ratio [OR] 4.0, 95% confidence interval [CI] 1.2 to 13.6) and log percentage of residents using gastrostomy tubes within the nursing home (adjusted OR 3.9, 95% CI 1.3 to 12.0) were associated with having a clinical isolate resistant to third-generation cephalosporins.

Aged↗

PubMed1992

Virulence properties of Enterobacteriaceae isolated from the small intestine of children with diarrhea.

Enterobacteriaceae isolated from the duodena of Peruvian children with persistent diarrhea (PD) have been examined for virulence factors and compared with Enterobacteriaceae isolated from children with acute diarrhea, those convalescent from PD and diarrhea-free controls. Escherichia coli were isolated from 42 of 186 (23%) of the aspirates. All 11 children with PD in whom multiple E. coli colonies were examined were colonized by a single serotype. DNA probes identified enterotoxigenic E. coli in 2 of 89 (2.2%) PD aspirates and 2 of 38 (5.3%) acute diarrhea aspirates and enteroaggregative E. coli in one PD and one control aspirate. Strains positive with the enteropathogenic E. coli adherence factor probe were identified from 2 of 89 (2.2%) patients with PD and 1 of 34 (2.9%) controls. A subset of 12 E. coli strains failed to show adhesion to human duodenal enterocytes although 5 of 9 showed sparse but polar attachment to ileal cells from a child with short bowel syndrome and PD. Three of 10 Enterobacteriaceae (two E. coli, one Klebsiella species) caused diarrhea in the reversible ileal tie adult rabbit model. Colonization with virulent Enterobactericeae did not explain the majority of episodes of PD. Examination of these duodenal bacteria in the rabbit model revealed some that caused diarrhea but were not recognized pathogens.

Bacterial Toxins↗

PubMed2006

Prevalence of extended-spectrum beta-lactamases among Enterobacteriaceae isolated from blood culture in a tertiary care hospital.

OBJECTIVE: To determine the prevalence of extended spectrum beta-lactamase among Enterobacteriaceae isolated from blood culture in a tertiary care hospital. METHODS: We carried out this study at the Armed Forces Hospital, Riyadh, Kingdom of Saudi Arabia during the period between January 2003-December 2004. We tested a total of 601 isolates of the family Enterobacteriaceae from blood culture for the prevalence of extended spectrum beta-lactamase (ESBL) production by the standardized disc diffusion method and confirmed by the ESBL E test strips. RESULTS: Ninety-five (15.8%) of the isolates were ESBL producers. Among these, 48.4% were Klebsiella pneumoniae (K. pneumoniae) followed by 15.8% of both Escherichia coli (E. coli) and Enterobacter cloacae (Ent. cloacae). Other isolates produced ESBL in low numbers. CONCLUSION: Klebsiella pneumoniae produced ESBL in significant numbers. Extended spectrum beta-lactamase gram-negative bacilli present significant diagnostic and therapeutic challenges to the management of infections due to these organisms. Microbiology laboratories should start reporting ESBL producing Enterobacteriaceae organism due to their importance in respect to antibiotic therapy and infection control aspects.

Enterobacteriaceae↗

PubMed2006

Occurrence of extended spectrum beta-lactamases among Enterobacteriaceae spp. isolated at a tertiary care institute.

Increasing resistance to third generation cephalosporins has become a cause for concern especially among Enterobacteriaceae that cause nosocomial infections. The prevalence of extended spectrum beta-lactamases (ESBLs) among members of Enterobacteriaceae constitutes a serious threat to current beta-lactam therapy leading to treatment failure and consequent escalation of costs. A detailed study was initiated to identify the occurrence of ESBLs among the Enterobacteriaceae isolates at a tertiary care hospital using the double disk potentiation technique. Antibiogram profiles were determined to commonly used antibiotics and confirmation of ESBLs production was carried out by the disk diffusion assay using ceftazidime and cefotaxime in the presence and absence of clavulanic acid. Our results indicate that the majority of ESBLs were expressed in Escherichia coli.

Anti-Bacterial Agents↗

PubMed1989

[The role of mechanically purified city sewers in the spread of antibiotic-resistant bacteria of the Enterobacteriaceae family].

The aim of this study was to evaluate a degree of contribution of mechanically cleansed municipal sewage in a spread in on environment of bacteria of Enterobacteriaceae family with special regard to antibiotic resistant strains. High number of bacteria of Enterobacteriaceae family was found in 1 ml of sewage and the number of antibiotic-resistant bacteria was 0.5-50 X 10(3)/ml. Among the strains tested the resistance to more than one antibiotics was encountered. 78.3% of strains transferred antibiotic resistance to E. coli recipient strain, what indicate a participation of potentially pathogenic bacteria from Enterobacteriaceae family in a spread of antibiotic resistance in a environment.

Anti-Bacterial Agents↗

PubMed1979

[An oral enteritis-vaccine composed of twelve heat inactivated Enterobacteriaceae. 1. Communication: Theoretical and epidemiological considerations (author's transl)].

The infectious diseases of the human intestinal tract which are caused by bacteria must be distinguished into two groups on account of their different pathogenesis: the cyclic infections (typhoid fever, parathyphoid fever) and the local infections (cholera, dysentery, Salmonella enteritis, dyspepsia coli infections). The local infections of the intestine do not cause a systemic but only a local immunity of the intestinal mucosa. It is necessary therefore to induce local immunity as active immunoprophylaxis by orally administering inactivated antigens. The twelve-fold enteritis vaccine consists of full antigens of 6 Salmonella strains, 2 Shigella strains, and 4 enteropathogenic coli strains pretreated by heat-inactivation (3 min/100 degrees C). The following should be considered as indication to effect active immunoprophylaxis against enteritis: Travelling into tropical and subtropical countries, people in emergency areas, children in developing countries, workers in food industries, secondary hospital infections, and carriers. The active mouse protection test revealed that oral immunization with enterobacteriaceae does not only deliver the well-known specific effect but also a non-specific effect which included the protection against other related enterobacteriaceae. Moreover, the specific component of the combined vaccine is enhanced by heterologous components. The resulting synergism or the adjuvantal effect, respectively, allows to employ a relatively limited number of germs which are selected on the basis of high pathogenicity, good immunogenicity, and great frequency. The first field trial with the twelve-fold vaccine was completed successfully: Following an infection with Salmonella which affected the employees of a fowl slaughtery, eight different species could be demonstrated; the above described polyvalent vaccine was orally administered and proved to be successful. The latter case clearly demonstrates the fast-acting effect of the vaccine on account of the heterologous bacterial antigens contained therein. 51 out of 60 Salmonella carriers excreted germs of a different antigen pattern not contained in the vaccine. However, the good results obtained showed that the species chosen for the vaccine were still sufficiently effective to cover the wide spectrum of other species of related enterobacteriaceae.

Administration, Oral↗

PubMed1983

[Cefotaxime, moxalactam and ceftriaxone: comparison of in vitro activity against hospital strains of Enterobacteriaceae belonging to the 4 principal phenotypes of sensitivity to beta-lactams].

MIC of ceftriaxone, moxalactam and cefotaxime is determined for 827 strains of Enterobacteriaceae isolated in the Central Laboratory of the Pitié-Salpêtrière Hospital between december 1981 and september 1982. Results are distributed according to the species involved and the pattern of sensitivity (S) and resistance (R) to ampicillin (A), carbenicilline (Ca) and cephalotin (Ct). Among the strains ASCaSCtS and ARCaRCtS cefotaxime and ceftriaxone have the lowest MICs. Among the most sensitive strains ARCaSCtR and ARCaRCtR cefotaxime, ceftriaxone and moxalactam have the similar MICs, whereas among the less sensitive ones moxalactam has the lowest MICs. The latter might be the cephalosporin of choice for the treatment of serious infection due to the less sensitive Enterobacteriaceae. On the other hand, cefotaxime and ceftriaxone might be the cephalosporins of choice for the treatment of serious infections due to the most sensitive Enterobacteriaceae.

Anti-Bacterial Agents↗

PubMed1982

Association of Enterobacteriaceae septicemia in the immediate postpartum period and asymptomatic bacteriuria.

In an 8-year period, 16 cases of parturitional septicemia due to the Enterobacteriaceae in the immediate postpartum period were identified that were not due to pyelonephritis. Fourteen of the 16 patients had more than 100,000 colonies per milliliter of urine of the same member of the Enterobacteriaceae as was present in the blood. Twelve of the 16 patients had concomitant endometrial cultures. In 11 patients the same isolate was recovered from urine and endometrium as had been recovered from the intravascular compartment. The data suggest an etiologic relationship between asymptomatic bacteriuria and septicemia due to the Enterobacteriaceae in which the maternal implantation site affords the principal portal of infection.

Bacteriuria↗

PubMed1994

Transferable drug resistance (R-factor) among the enterobacteriaceae in urinary tract infections: a study at an urban hospital in Bangladesh.

Prevalence and patterns of drug resistance were studied among Enterobacteriaceae, isolated from the cases of urinary tract infection (UTI) attending at an outpatient department of an urban hospital in Dhaka. Out of 90 Enterobacteriaceae isolated, 95.5% were resistant to the different antimicrobials tested. The most common resistance pattern observed was against ampicillin (A), trimethoprim (Tm), sulphamethoxazole (S), tetracycline (T) and chloramphenicol (C) in all four genera of Enterobacteriaceae. Transferable drug resistance (R(+)-factor) was detected in 68.5% Escherichia coli (E. coli), 60% Klebsiella, 66.6% Proteus and 50% Citrobacter strains. By using a resistance transfer factor (RTF) mobilizing strain, resistance factors were transferred from 3 (11.3%) out of 26 non-autotransferable strains. The study revealed that transferable drug resistance is common in organisms isolated from UTI in Bangladesh.

Anti-Bacterial Agents↗

PubMed1984

Enterobacteriaceae as indicators of good manufacturing practices in rendering plants.

Finished products and samples from the environment of the production line in rendering plants were checked for Enterobacteriaceae and salmonellae. Improvements in hygiene and measures taken to limit multiplication of microorganisms in the dry area of the production lines resulted in reduction of both numbers of Enterobacteriaceae in environmental samples and frequency of their occurrence in finished products. Simultaneously, there was an equivalent reduction of salmonellae positives in environmental samples and finished products. Consequently, the determination of Enterobacteriaceae can be used as an effective tool to assess the improvements in good manufacturing practices.

Dust↗