The unique structure of bacterial polysaccharides - Immunochemical studies on the O-antigen of Proteus penneri 4034-85 clinical strain classified into a new O83 Proteus serogroup.

The serological classification scheme of the opportunistic Proteus bacilli includes a number of Proteus penneri strains. The tested P. penneri 4034-85 strain turned out to be serologically distinguished in ELISA and Western blotting. The O-polysaccharide was obtained by mild acid degradation of the lipopolysaccharide of this strain and studied by sugar and methylation analyses and dephosphorylation along with 1H and 13C NMR spectroscopy, including 2D 1H,1H COSY, TOCSY, ROESY, 1H,13C HSQC, HMBC, and HSQC-TOCSY experiments, The O-polysaccharide was found to have a linear repeating unit containing glycerol 1-phosphate and two residues each of Gal and GlcNAc. The following O-polysaccharide structure was established, which, to our knowledge, is unique among known bacterial polysaccharide structures.

AcrIF9 tethers non-sequence specific dsDNA to the CRISPR RNA-guided surveillance complex.

Bacteria have evolved sophisticated adaptive immune systems, called CRISPR-Cas, that provide sequence-specific protection against phage infection. In turn, phages have evolved a broad spectrum of anti-CRISPRs that suppress these immune systems. Here we report structures of anti-CRISPR protein IF9 (AcrIF9) in complex with the type I-F CRISPR RNA-guided surveillance complex (Csy). In addition to sterically blocking the hybridization of complementary dsDNA to the CRISPR RNA, our results show that AcrIF9 binding also promotes non-sequence-specific engagement with dsDNA, potentially sequestering the complex from target DNA. These findings highlight the versatility of anti-CRISPR mechanisms utilized by phages to suppress CRISPR-mediated immune systems.

The New Structure of Core Oligosaccharide Presented by Proteus penneri 40A and 41 Lipopolysaccharides.

The new type of core oligosaccharide in Proteus penneri 40A and 41 lipopolysaccharides has been investigated by ¹H and 13C NMR spectroscopy, electrospray ionization mass spectrometry and chemical methods. Core oligosaccharides of both strains were chosen for structural analysis based on the reactivity of LPSs with serum against P. penneri 40A core oligosaccharide-diphtheria toxoid conjugate. Structural analyses revealed that P. penneri 40A and 41 LPSs possess an identical core oligosaccharide.

Classification of Proteus penneri lipopolysaccharides into core region serotypes.

The frequency of P. penneri isolation from hospital patients, mostly from urine and wounds, keeps on growing, and numerous isolates are multi-drug resistant. P. penneri rods produce lipopolysaccharide (LPS), which may lead to the septic shock. Until now, O-specific polysaccharide has been the best structurally and serologically characterized region of P. penneri LPS. It is worth having an insight into the serological specificity of both poly- and oligosaccharide parts of P. penneri LPS. The P. penneri core region is less structurally diverse than OPS, but still, among other enterobacterial LPS core regions, it is characterized by structural variability. In the present study, the serological reactivity of 25 P. penneri LPS core regions was analyzed by ELISA, passive immunohemolysis and Western blot technique using five polyclonal P. penneri antisera after or without their adsorption with the respective LPSs. The results allowed the assignment of the tested strains to five new core serotypes, which together with published serological studies led to the creation of the first serotyping scheme based on LPS core reactivities of 35 P. penneri and three P. mirabilis strains. Together with the O types scheme, it will facilitate assigning Proteus LPSs of clinical isolates into appropriate O and R serotypes.

Classification of a Proteus penneri clinical isolate with a unique O-antigen structure to a new Proteus serogroup, O80.

Proteus penneri is an opportunistic pathogen, which may cause severe diseases, most frequently urinary tract infections in immunocompromised patients. P. penneri Br 114 exhibiting a good swarming growth ability as an S-form strain was isolated from a wound of a patient in Lódz, Poland. Serological studies using ELISA and Western blotting and chemical analyses along with (1)H and (13)C NMR spectroscopy showed that the O-antigen (O-polysaccharide) of this strain is unique among the known Proteus serotypes O1-O79. It possesses a linear pentasaccharide repeating unit containing a partially O-acetylated amide of D-glucuronic acid (GlcA) with L-serine having the following structure: [structure: see text]. These data are a basis for creating a new Proteus serogroup, O80, so far represented by the single Br 114 isolate. The O80 is the 21st O-serogroup containing P. penneri strains and the fourth serogroup based on Proteus spp. clinical isolates from Lódz, Poland.

Extended spectrum beta lactamase producing Proteus penneri: a rare missed pathogen?

Indole negative Proteus species are invariably incorrectly identified as Proteus mirabilis, often missing out isolates of Proteus penneri. We report a case of extended spectrum beta lactamase producing and multidrug-resistant P. penneri isolated from pus from pressure sore of a patient of road traffic accident. Correct and rapid isolation and identification of such resistant pathogen are important as they are significant nosocomial threat.

The amide of galacturonic acid with lysine as an immunodominant component of the lipopolysaccharide core region from Proteus penneri 42 strain.

Most Proteus lipopolysaccharides (LPSs) contain uronic acids or their amides with different amino acids, which together with other negatively charged components account for the acidic character of such LPS molecules. Previous studies have shown the significance of an amide of galacturonic acid with lysine [D-GalA(L-Lys)] for serological specificity of O-antigens from few P. mirabilis strains. In this work, the immunodominant role of GalALys was indicated for the P. penneri 42 LPS core region. The studies also showed the serological identity of core oligosaccharides from P. penneri 42 (O71), P. mirabilis 51/57 (O28) and R14/S1959 strains.

Identification of a Proteus penneri isolate as the causal agent of red body disease of the cultured white shrimp Penaeus vannamei and its control with Bdellovibrio bacteriovorus.

Bacteriosis has become a major economic problem in the farming of the Pacific white shrimp Penaeus vannamei. However, no definitive data are available about Proteus penneri infection in cultured P. vannamei and its control. In this study, a virulent strain NC was isolated from diseased P. vannamei suffering from red body disease and identified as a P. penneri isolate through phylogenetic analysis and ATB 32GN system. A phylogenetic constructed tree using the neighbour-joining method identified the NC isolate as a P. penneri strain. In addition, Bdellovibrio bacteriovorus conferred significant protection against P. penneri: it exhibited significant bacteriolytic effects on the pathogenic P. penneri, had a wide prey range towards Proteus pathogens, and displayed a good protective efficacy on experimental P. penneri infection in P. vannamei. To the best of our knowledge, this is the first report of farmed P. vannamei infected with P. penneri and its control with B. bacteriovorus.

Serological studies of Proteus penneri strains determining qualification to appropriate O-serogroup.

Our Department of General Microbiology created a wide collection of P. penneri isolates and classified most of them into 19 different O-serogroups. This work describes the classification of 12 remaining P. penneri strains. The lipopolysaccharides extracted from P. penneri strains were tested in an enzyme-linked immunosorbent assay (ELISA) with selected O-antisera against Proteus sp. strains. Homologous and cross-reacting systems were checked in: passive immunohemolysis (PIH), inhibition of ELISA and PIH and Western blot procedure. These studies led to the qualification of tested P. penneri strains to five Proteus sp. O-serogroups, thus completing the serological classification of the whole collection.

Swarming growth and resistance of Proteus penneri and Proteus vulgaris strains to normal human serum.

BACKGROUND: Proteus sp. strains isolated from patients with urinary tract infection (UTI) are often insensitive to the bactericidal action of normal human serum (NHS) which poses a clinical problem. The swarming phenomenon is an especially important factor in cases of UTIs gained through the ascending route. Both these virulence factors are connected with the cell surface components of bacteria, including lipopolysaccharide (LPS). OBJECTIVES: The resistance of Proteus bacilli to the bactericidal activity of NHS and the swarming phenomenon were investigated as well as the possible relationships between these virulence factors and the chemical structure of LPS. MATERIAL AND METHODS: The research was carried out on P. penneri and P. vulgaris species. Two preparations of sera were tested with respect to the bactericidal action of NHS. The ability of bacteria to swarm was checked on broth agar plates. The length of the O-specific part of LPS was estimated after poliacrylamide gel electrophoresis (PAGE) and staining with silver nitrate. RESULTS: Among the 62 tested Proteus strains, over 62% of Proteus vulgaris and 50% of Proteus penneri strains were sensitive to the bactericidal action of NHS. However, the number of resistant strains grew dramatically when serum with blocked complement activation via the alternative pathway was used. From 102 of the Proteus sp. Strains, only few were unable to swarm over the solid surface of the media. The remaining showed diverse ability to translocate. CONCLUSIONS: There was no definite correlation between the chemical structure of the O-specific chains of lipopolysaccharides and sensitivity or resistance of the Proteus sp. strains to NHS. Also, no significant relationships were found between the length or the chemical structure of the O-specific chains of the bacterial LPSs and the swarming phenomenon.

Isolation, identification & characterization of Proteus penneri--a missed rare pathogen.

BACKGROUND & OBJECTIVES: Indole negative Proteus species are invariably incorrectly identified as P. mirabilis, missing isolates of Proteus penneri. P. penneri is an invasive pathogen capable of causing major infectious diseases still seldom reported in individual cases. We report here the isolation, differentiation, characterization and typing of P. penneri from patients with different clinical infections. METHODS: Urine, pus and body fluids collected from patients in intensive care units, wards and out patients departments of a tertiary health care institute from north India were cultured. A total of 61 indole negative Proteus isolates were subjected to extended biochemical tests to differentiate and identify P. penneri from P. mirabilis including failure to produce ornithine decarboxylase (by 0% strains of P. penneri and 100% strains of P. mirabilis) besides P. penneri being uniformly salicin negative, non-utilizer of citrate but ferments sucrose and maltose. Antibiograms and Dienes phenomenon were performed to characterize and type P. penneri isolates besides screening for ß-lactamase production. RESULTS: Eight isolates of P. penneri were identified; four from urine, three from abdominal drain-fluid and one from diabetic foot ulcer. P. penneri was isolated as the sole pathogen in all patients having underlying disease; post-operatively. Swarming was not seen in the first strain on primary isolation and was poor in strain-4. All eight isolates were biochemically homologous but multi-drug resistant (MDR) with resistance to 6-8 drugs (up to 12). ß-lactamase production was seen in three of five isolates while Dienes phenomenon found four distinct types and discriminated strains differing in resistance even with a single drug. INTERPRETATION & CONCLUSIONS: A few additional biochemical tests identified P. penneri isolates; it infected patients with underlying disease and strains were MDR and heterogenous.

Fournier's gangrene in a child with congenital genitourinary anomalies.

Fournier's gangrene is a rare urologic emergency in childhood that requires prompt diagnosis to deliver definitive and supportive care. Host susceptibility risk factors differ between adult and pediatric age groups with affected children usually otherwise systemically healthy. We present a case of Fournier's gangrene in a 2-year-old, from a genitourinary source of sepsis secondary to previously unreported genitourinary anatomical anomalies of congenital buried penis and hypospadias. Illustrative applied anatomy identifies the pathogenesis of this case, aiding recognition and understanding of this rapidly progressive and destructive pathology.

Characterization of epitope specificity of Proteus penneri 7 lipopolysaccharide core region.

To extend the knowledge on the fragments of Proteus penneri lipopolysaccharide core regions, which determine the cross-reactions with specific antibodies, serological studies were performed by use of P. penneri 7 core-specific antiserum and Proteus sp. lipopolysaccharides. Different reactivity of the tested antiserum with three groups of antigens suggested differences in their core regions' epitope specificity. Comparing the results of the serological investigations with the previously determined structures of the core regions of the tested P. penneri lipopolysaccharides allowed distinguishing two potential tri- and tetrasaccharide epitopes and a third fragment which could not be determined precisely.

Application of two different kinds of sera against the Proteus penneri lipopolysaccharide core region in search of epitopes determining cross-reactions with antibodies.

INTRODUCTION: Proteus penneri lipopolysaccharide (LPS) core regions are characterized by a greater structural variability than that observed in other Enterobacteriaceae. This fact and the small amount of published data concerning the serological activity of this part of P. penneri LPS prompted an examination of which fragment might determine cross-reactions with antibodies. To date, such epitopes have been found in the LPS core regions of P. mirabilis and P. vulgaris strains. MATERIALS AND METHODS: Proteus sp. LPSs were tested with unabsorbed rabbit antisera by enzyme-linked immunosorbent assay (ELISA), sodium dodecyl sulfate polyacrylamide gel electrophoresis and Western blot, and once again by ELISA or passive immunohemolysis after the absorption of these antisera with selected LPSs. RESULTS: The serological studies of P. penneri 8 LPS demonstrated antibodies in the tested antisera recognizing a common epitope located in the core regions of six of the LPSs, i.e. P. penneri 8, 34, 133, 7, 14, and 15. Additionally, another type of antibody directed against some fragment of P. penneri 13 and the core regions of other LPSs investigated was observed in one antiserum. CONCLUSIONS: A distal, trisaccharide fragment of the P. penneri 8 LPS core region is suggested to determine the cross-reactions of the tested antisera with the six P. penneri LPSs.

Serological classification and epitope specificity of Proteus vulgaris TG 251 from Proteus serogroup O65.

INTRODUCTION: Proteus rods are currently subdivided into five named species, i.e. Proteus mirabilis, P. vulgaris, P. penneri, P. hauseri, and P. myxofaciens, and three unnamed Proteus genomospecies 4 to 6. Based on the serospecificity of the lipopolysaccharide (LPS; O-antigen), strains of P. mirabilis and P. vulgaris were divided into 49 O-serogroups and 11 additional O-serogroups were proposed later. About 15 further O-serogroups have been proposed for the third medically important species, P. penneri. Here the serological classification of P. vulgaris strain TG 251, which does not belong to these serogroups, is reported. Serological investigations also allowed characterization of the epitope specificity of its LPS. MATERIALS AND METHODS: Purified LPSs from five Proteus strains were used as antigens in enzyme immunosorbent assay (EIA), SDS/PAGE, and Western blot and alkali-treated LPSs in the passive immunohemolysis (PIH) test, inhibition of PIH and EIA, and absorption of the rabbit polyclonal O-antisera with the respective LPS. RESULTS: The serological studies of P. vulgaris TG 251 LPS indicated the identity of its O-polysaccharide with that of P. penneri O65. The antibody specificities of P. vulgaris TG 251 and P. penneri O65 O-antisera, were described. CONCLUSIONS: P. vulgaris TG 251 was classified to the Proteus O65 serogroup. Two disaccharide-associated epitopes present in P. vulgaris TG 251 and P. penneri O65 LPSs are suggested to be responsible for cross-reactions with three heterologous Proteus strains.

Serological and structural characterization of the O-antigens of the unclassified Proteus mirabilis strains TG 83, TG 319, and CCUG 10700 (OA).

INTRODUCTION: Lipopolysaccharide (endotoxin, LPS) is an important potential virulence factor of Proteus rods. The serological specificity of the bacteria is defined by the structure of the O-polysaccharide chain (O-antigen) of the LPS. Until now, 76 O-serogroups have been differentiated among Proteus strains. MATERIALS AND METHODS: LPSs were isolated from Proteus mirabilis TG 83, TG 319, and CCUG 10700 (OA) strains by phenol/water extraction. Antisera were raised by immunization of rabbits with heat-killed bacteria. Serological investigations were performed using enzyme immunosorbent assay, passive immunohemolysis, inhibition of both assays, absorption of antisera, and Western blot. RESULTS: The cross-reactive epitope shared by these strains and P. penner O72a,O72b is located on the O-polysaccharide and is most likely associated with an alpha-D-Glcp-(1-->6)-beta-D-GalpNAc disaccharide fragment. The serological data indicated the occurrence of two core types in the LPSs studied, one characteristic for P. mirabilis TG 319 and CCUG 10700 (OA) and the other for P. mirabilis TG 83 and O57. CONCLUSIONS: The serological and structural data showed that P. mirabilis TG 83, TG 319, CCUG 10700 (OA), and O57 have the same O-antigen structure and could be qualified to the Proteus O57 serogroup.

[Proteus penneri]. / Proteus penneri.

Proteus penneri, formerly P. vulgaris biogroup 1, was recognized as a new species in 1982. This species is associated with clinical processes similar to those involving P. mirabilis and P. vulgaris and expresses similar pathogenic determinants. In clinical samples, P. penneri is mainly isolated from urine (50%), wound and soft tissue exudates (25%), and blood cultures (15%), mostly of nosocomial origin. Although P. penneri is easy to identify, it can be misidentified as P. vulgaris by automatic systems that do not include the indol test result in the identification process. This species has a characteristic susceptibility profile, essentially due to the production of the chromosomal inducible beta-lactamase HugA, which presents a high homology (86%) with CumA from P. vulgaris. HugA is inhibited by clavulanic acid and determines resistance to aminopenicillins and first- and second-generation cephalosporins, including cefuroxime, but does not affect cephamycins or carbapenems, and is inhibited by clavulanic acid. HugA is derepressed due to mutational processes in gene regulators, affecting the activity of cefotaxime and, to a much lesser extent, that of ceftazidime and aztreonam. This phenotype resembles the production of an extended spectrum beta-lactamase. Like other Proteus species, P. penneri is resistant to tetracyclines and should be considered resistant to nitrofurantoin.

Proteus penneri / Proteus penneri

Proteus penneri, anteriormente denominado Proteus vulgaris biogrupo 1, fue reconocido como especie nueva en 1982. Se asocia a procesos similares a los que producen Proteus mirabilis y Proteus vulgaris y comparte con ellos factores de patogenicidad. En muestras clínicas, se aísla esencialmente de orina (50%), exudados de piel y tejidos blandos (25%) y hemocultivos (15%), sobre todo en infección nosocomial. Su identificación no es problemática, aunque puede confundirse con P. vulgaris en los sistemas automáticos que no utilicen la prueba de indol en los procesos de identificación. Tiene un perfil de resistencia particular debido a la producción de la β-lactamasa cromosómica inducible HugA, con una elevada homología (86%) con CumA de P. vulgaris. HugA determina resistencia a aminopenicilinas y cefalosporinas de primera y segunda generación, incluyendo la cefuroxima, pero no afecta a las cefamicinas ni los carbapénemes, y se inhibe por el ácido clavulánico. La síntesis de HugA se desreprime debido a mutaciones en los genes reguladores, con lo que se afectan la actividad de la cefotaxima y, en mucha menor medida, la de la ceftazidima y el aztreonam. Este fenotipo puede confundirse con la producción de una β-lactamasa de espectro extendido. Al igual que otros Proteus penneri, es resistente a las tetraciclinas y debe considerarse resistente a la nitrofurantoína

Proteus penneri, formerly P. vulgaris biogroup 1, was recognized as a new species in 1982. This species is associated with clinical processes similar to those involving P. mirabilis and P. vulgaris and expresses similar pathogenic determinants. In clinical samples, P. penneri is mainly isolated from urine (50%), wound and soft tissue exudates (25%), and blood cultures (15%), mostly of nosocomial origin. Although P. penneri is easy to identify, it can be misidentified as P. vulgaris by automatic systems that do not include the indol test result in the identification process. This species has a characteristic susceptibility profile, essentially due to the production of the chromosomal inducible β-lactamase HugA, which presents a high homology (86%) with CumA from P. vulgaris. HugA is inhibited by clavulanic acid and determines resistance to aminopenicillins and first- and second-generation cephalosporins, including cefuroxime, but does not affect cephamycins or carbapenems, and is inhibited by clavulanic acid. HugA is derepressed due to mutational processes in gene regulators, affecting the activity of cefotaxime and, to a much lesser extent, that of ceftazidime and aztreonam. This phenotype resembles the production of an extended spectrum β-lactamase. Like other Proteusspecies, P. penneri is resistant to tetracyclines and should be considered resistant to nitrofurantoin

[Enzymatic resistance to beta lactam antibiotics within the genus Proteus and evaluation of Proteus mirabilis phenotypes and genotypes for resistance to third- and fourth-generation cephalosporins]. / Resistencia enzimática a betalactámicos en el género Proteus y evaluación de los fenotipos y genotipos de resistencia a cefalosporinas de tercera y cuarta generación en Proteus mirabilis.

INTRODUCTION: The aim of this study was to evaluate betalactam resistance within the genus Proteus and characterize the betalactamases responsible for this resistance. METHODS: We analyzed 99 strains (87, P. mirabilis; 10 P. vulgaris, and 2, P. penneri) isolated from patients at one University Hospital. Antibiotic susceptibility tests were performed according to NCCLS recommendations. Presence of extended spectrum betalactamases (ESBL) was inferred by both double disk diffusion tests and minimum inhibitory concentration (MIC) of third and fourth generation cephalosporins alone and in the presence of clavulanic acid. Isoelectric points (pI) of the enzymes were estimated by isoelectrofocusing and the presence of the encoding genes was confirmed by polymerase chain reaction (PCR). RESULTS: A broad spectrum betalactamase could be detected in those isolates (28%) resistant to penicillin and first generation cephalosporins while CTX-M-2 enzyme could be detected in P. mirabilis isolates resistant to third and fourth generation cephalosporins (18%). One of the P. vulgaris displayed reduced susceptibility to cefotaxime due to an enzyme of pI 7.4, while resistance to cefotaxime in one P. penneri was related to an enzyme of pI 6.8. Both enzymes were active on cefotaxime (1,000 mg/l) in the iodometric assay. CONCLUSION: The broad extended spectrum betalactamase within genus Proteus was TEM-1, while CTX-M-2 was the ESBL responsible for the third and fourth generation cephalosporins in P. mirabilis. In P. vulgaris and P. penneri this resistance was associated with the hyperproduction of the chromosomal encoded betalactamase.

Resistencia enzimática a betalactámicos en el género Proteus y evaluación de los fenotipos y genotipos de resistencia a cefalosporinas de tercera y cuarta generación en Proteus mirabilis / Enzymatic resistance to betalactam antibiotics within the genus Proteus and evaluation of third and fourth generation cephalosporins resistance phenotypes and genotypes within Proteus mirabilis

INTRODUCCIÓN. El objetivo de este trabajo fue evaluar la resistencia a betalactámicos en el género Proteusy caracterizar las betalactamasas responsables de dicha resistencia. MÉTODOS. Se analizaron 99 cepas (87 P. mirabilis;10 P. vulgaris, y 2, P. penneri) aisladas de pacientes atendidos en un Hospital Universitario. Los ensayos de susceptibilidad a antibióticos se realizaron de acuerdo con las recomendaciones del National Committee for Clinical Laboratory Standards. La presencia de betalactamasas de espectro extendido (BLEE)fue inferida por el método de difusión de doble disco y por la concentración inhibitoria mínima (CIM) de cefalosporinas de tercera y cuarta generación solas y en presencia de ácido clavulánico. Se estimó el punto isoeléctrico (pI) por isoelectro-enfoque y la presencia de los genes codificantes se confirmó por reacción en cadena de la polimerasa (PCR).RESULTADOS. Una betalactamasa de amplio espectro fue detectada en aquellos aislamientos resistentes apenicilinas y cefalosporinas de primera generación (28%),mientras que la enzima CTX-M-2 fue detectada en los aislamientos de P. mirabilis resistentes a cefalosporinas de tercera y cuarta generación (18%). Uno de los P. vulgaris presentó sensibilidad disminuida a cefotaxima debido a una enzima de pI 7,4, mientras que la resistencia a cefotaxima en un P. penneri fue relacionada con una enzima de pI 6,8. Ambas enzimas fueron activas sobre cefotaxima (1.000 mg/l) en el ensayo iodométrico. CONCLUSIÓN. La betalactamasa de amplio espectro en el género Proteus fue TEM-1 mientras queCTX-M-2 fue la BLEE responsable de la resistencia a cefalosporinas de tercera y cuarta generación en P. mirabilis. En P. vulgaris y P. penneri esta resistencia se asoció a la hiperproducción de la betalactamasa cromosómica (AU)

INTRODUCTION. The aim of this study was to evaluate betalactam resistance within the genus Proteus and characterize the betalactamases responsible for this resistance. METHODS. We analyzed 99 strains (87, P. mirabilis;10 P. vulgaris, and 2, P. penneri) isolated from patients at one University Hospital. Antibiotic susceptibility tests were performed according to NCCLS recommendations. Presence of extended spectrum betalactamases (ESBL)was inferred by both double disk diffusion tests andminimum inhibitory concentration (MIC) of third and fourth generation cephalosporins alone and in the presence of clavulanic acid. Isoelectric points (pI)of the enzymes were estimated by isoelectrofocusing and the presence of the encoding genes was confirmed by polymerase chain reaction (PCR).RESULTS. A broad spectrum betalactamase could be detected in those isolates (28%) resistant to penicillin and first generation cephalosporins while CTX-M-2 enzyme could be detected in P. mirabilis isolates resistant to third and fourth generation cephalosporins (18%). One of the P. vulgaris displayed reduced susceptibility to cefotaxime due to an enzyme of pI 7.4, while resistance to cefotaximein one P. penneri was related to an enzyme of pI 6.8. Both enzymes were active on cefotaxime (1,000 mg/l)in the iodometric assay. CONCLUSION. The broad extended spectrum betalactamase with in genus Proteus was TEM-1, while CTX-M-2 was the ESBL responsible for the third and fourth generation cephalosporins in P. mirabilis. In P. vulgarisand P. penneri this resistance was associated with the hyperproduction of the chromosomal encoded betalactamase (AU)