Extracellular enzymes of fecal strains ofPseudomonas aeruginosa

During a three year study 67 strains ofPseudomonas aeruginosa were isolated from stools of 67 patients with gastroenteritis. Serotypes 3 and 6 were the most frequent. The three strains that were serotype 11 were also the only-galactosidase producers. All strains were strongly pigmented. Over 90% of the isolates produced hemolysin, gelatinase, protease (caseinase), fibrinolysin, lecithinase and elastase. Fecal carriers ofPseudomonas aeruginosa can be considered a source of dissemination of potentially virulent and invasive strains.     

Resistant strains ofPseudomonas aeruginosa isolated after exposure to several beta-lactam antibiotics

Successive transfer of three clinical isolates ofPseudomonas aeruginosa in liquid medium containing serial dilutions of several beta-lactam antibiotics was used to isolate resistant variants. The alpha-carboxy-penicillins (carbenicillin and ticarcillin), the acylureidopenicillins (piperacillin and azlocillin) and cephalosporins (moxalactam, cefoperazone, cefsulodin and ceftazidime) were used as the selective antibiotics. Resistant variants were isolated from two of the three strains (strains 27 and 45), using an inoculum size of 10⁴–10⁵ CFU/ml, which showed a mean 5 to 8-fold increase in MIC for most of the selected antibiotics. The 27-carbenicillin and 27-cefsulodin resistant variants showed beta-lactamase production similar to that of the parent. However, alterations were found in outer-membrane proteins and lipopolysaccharides. With azlocillin, moxalactam and ceftazidime as the selective antibiotics, resistant variants were isolated from strains 27 and 45 which showed a stable increased constitutive beta-lactamase production. From the third strain, 9150, the only variants isolated showed a two dilution-step increase in MIC to the antibiotics tested. The betalactamase production, outer-membrane proteins and lipopolysaccharides of these variants were similar to those of the parent.     

Characteristics ofPseudomonas aeruginosa strains causing septicemia in a Spanish hospital 1981–1990

The epidemiological and biochemical characteristics ofPseudomonas aeruginosa strains causing septicemia in a Spanish hospital over a ten-year period (1981–1990) were analyzed. A total of 207 episodes, corresponding to 0.7 episodes per 1,000 inpatients and 3.2 % of the total number of episodes of septicemia, were registered. Males were more often affected than females (rate 3.2:1). The respiratory (24.6 %) and urinary (21.2 %) tracts were the main portals of entry, while haematologic and solid tumours (15.4 %) were the most frequent underlying diseases. More than 86 % of the strains were susceptible to ceftazidime, mezlocillin, piperacillin and amikacin. Seventy strains were subjected to typing and analysis of virulence factors. Serotypes O:6, O:11 and O:2 could be considered endemic (each present in more than 11.4 % of strains). Pyocin typing, antibiotyping and resistotyping were preferred as secondary typing methods to phage typing and plasmid profile analysis. The combination of methods revealed a large diversity of strains although some cluster predominated. More than 80 % of the strains produced several exoenzymes, possessed pyoverdin and showed haemolytic activity, and all except one showed serum resistance. All strains were susceptible to silver and more than 80 % to mercury and boron, but all were resistant to iodine.     

Multilocus sequence typing compared to pulsed-field gel electrophoresis for molecular typing of Pseudomonas aeruginosa

For hospital epidemiologists, determining a system of typing that is discriminatory is essential for measuring the effectiveness of infection control measures. In situations in which the incidence of resistant Pseudomonas aeruginosa is increasing, the ability to discern whether it is due to patient-to-patient transmission versus an increase in patient endogenous strains is often made on the basis of molecular typing. The present study compared the discriminatory abilities of pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) for 90 P. aeruginosa isolates obtained from cultures of perirectal surveillance swabs from patients in an intensive care unit. PFGE identified 85 distinct types and 76 distinct groups when similarity cutoffs of 100% and 87%, respectively, were used. By comparison, MLST identified 60 sequence types that could be clustered into 11 clonal complexes and 32 singletons. By using the Simpson index of diversity (D), PFGE had a greater discriminatory ability than MLST for P. aeruginosa isolates (D values, 0.999 versus 0.975, respectively). Thus, while MLST was better for detecting genetic relatedness, we determined that PFGE was more discriminatory than MLST for determining genetic differences in P. aeruginosa.     

Molecular epidemiological analysis ofPseudomonas aeruginosa strains causing failure of antibiotic therapy in cystic fibrosis patients

A combination of esterase electrophoretic typing and analysis of the restriction fragment length polymorphism of ribosomal DNA regions (ribotyping) was used to compare 27Pseudomonas aeruginosa strains isolated before and after two-week courses of anti-pseudomonal treatment in seven cystic fibrosis patients. A total of 12 courses of therapy were studied in which ciprofloxacin, ceftazidime, azlocillin or imipenem were used alone or in combination with tobramycin. Isolates at a count of 10⁶ cfu/ml of sputum were collected when there was evidence of therapeutic failure on the basis of persistence of isolates whether or not they were resistant to the antibiotic used for therapy. Emergence of resistance was observed in ten cases and failure to eradicate sensitive strains in five cases. Among the 27 isolates, eight zymotypes and five ribotypes were identified. With this typing approach, resistant post-therapy isolates were found to be identical to pre-therapy isolates in all cases but one. However, in one case an additional resistant strain was isolated after therapy besides that initially present. In all five cases in which susceptibility was still observed after treatment, pretherapy and post-therapy isolates were indistinguishable. Using this molecular typing approach, all the strains were typable. Thus combination of esterase typing and ribotyping should improve the analysis of therapeutic failure in cystic fibrosis patients.     

Multilocus enzyme electrophoresis analysis of the Mycobacterium avium complex and other mycobacteria.

Multilocus enzyme electrophoresis analysis was used to evaluate the Mycobacterium avium complex (MAC), M. paratuberculosis, and nine other mycobacterial species. The average number of alleles per locus was 2.8 for the 35 MAC and 2 M. paratuberculosis strains which represented 24 electrophoretic types (ETs) and two distinct groups. The M. avium group was resolved into 17 ETs and contained the M. paratuberculosis ET. The M. intracellulare group consisted of six ETs. There was complete agreement between Gen-Probe identification and group placement by multilocus enzyme electrophoresis. The mean genetic diversity per locus for the 24 MAC ETs was 0.38. This procedure subdivided some serovars and, if implemented, should prove to be a powerful epidemiologic tool for the MAC. Eleven additional ETs were formed after the data for the other mycobacterial species were pooled with those for the MAC.     

Evaluation of ciprofloxacin in the treatment ofPseudomonas aeruginosa infections

The efficacy and safety of ciprofloxacin in the treatment ofPseudomonas aeruginosa infections was evaluated in 72 patients suffering from upper urinary tract infection (19 patients), deep soft tissue infection (16), chronic osteomyelitis (12), abscess (7), chronic otitis media (6), otitis externa (3) and bronchopneumonia (9). Forty-eight patients received an oral dose of 500 mg or 750 mg b.i.d. and five patients an i.v. dose of 200 mg b.i.d., while 19 patients were given both oral and parenteral doses. The duration of therapy ranged from seven days to more than four months. The MICs of ciprofloxacin for thePseudomonas aeruginosa strains isolated were in the range < 0.06–2 mg/l; 36% of the strains were resistant to all other available antibiotics. At follow-up after a minimum of six months the clinical success rate was 75% and the infecting organism was permanently eradicated in 49% of the patients. In nine patients the organism developed resistance, particularly when the initial MIC was higher than 0.5 mg/l. No significant adverse reactions were observed. Ciprofloxacin is the first antipseudomonal antimicrobial agent which can be administered orally and therefore fulfills a need in chemotherapy.     

Use of ciprofloxacin in the treatment ofPseudomonas aeruginosa infections

The therapeutic efficacy and safety of ciprofloxacin was studied in 30 patients withPseudomonas aeruginosa infections. In 20 patients ciprofloxacin was given alone and in 10 patients (including 8 compromized hosts) in combination with an aminoglycoside (9) or azlocillin (1). Ciprofloxacin was given in doses of 500 mg orally or 200–300 mg i. v. every 12 h. In patients receiving only ciprofloxacin clinical cure with eradication of bacteria was obtained in 15 patients (75%) with infections of bone and joint (6), skin and soft tissue (4), lung (2), middle ear (2) and CSF (1). Two patients with lymphoma andPseudomonas aeruginosa pneumonia died. In patients receiving combination therapy a definite therapeutic success was achieved in four (40%). Three patients withPseudomonas aeruginosa septicemia died. In seven patients nine bacterial strains with decreasing susceptibility of ciprofloxacin (increase in MIC from 0.5g/ml to 2–16 g/ml) were selected (6Pseudomonas aeruginosa, 1Enterobacter cloacae, 1Serratia marcescens, 1Staphylococcus aureus). Ciprofloxacin was well tolerated. This new quinolone seems to be suitable for single drug treatment ofPseudomonas aeruginosa infections in patients with normal host defense mechanisms, while its therapeutic potential in compromized hosts requires further evaluation.     

Determination of the O-serovars ofPseudomonas aeruginosa by slide coagglutination

Determination of the somatic (O-) antigens ofPseudomonas aeruginosa by conventional slide agglutination is frequently complicated by the barely discernible, slow reaction of native cells. For diagnostic purposes a more practical procedure, a coagglutination test, has been developed in which protein A bearingStaphylococcus aureus (ATCC 12598) cells are added to the agglutination process occurring between specific anti-O serum and nativePseudomonas aeruginosa. Compared to the conventional method, slide O-coagglutination yields larger agglutinates in a shorter mean reaction time, i.e. one minute vs four minutes. Moreover, strains not reacting in the O-agglutination method or reacting only with polyvalent anti-O serum can be grouped by O-coagglutination, and cross reactions between reference strains of different O-groups do not occur. This method facilitates O-grouping ofPseudomonas aeruginosa in epidemiological investigations.     

Preformed enzyme profiles of reference strains of gram-positive anaerobic cocci

The preformed (constitutive) enzyme profiles of 30 type strains and reference strains of gram-positive anaerobic cocci were determined with two commercial systems, RapID ANA and a prototype system from API. Both systems identified Peptostreptococcus anaerobius, Ps. asaccharolyticus, Ps. indolicus, Ps. magnus and Ps. micros accurately, except for one strain of Ps. magnus misidentified as Ps. micros by the RapID ANA system. The indole-negative, butyrate-producing cocci (classified at present as Ps. prevotii and Ps. tetradius) produced several different, unique patterns with the prototype API system, but the results with RapID ANA were often misleading. Eight strains of Hare group cocci produced previously described profiles. Four strains of streptococci produced profiles easily distinguished from those of the gram-positive anaerobic cocci. We conclude that most gram-positive anaerobic cocci can be identified rapidly and reliably to the species level by their preformed enzyme profiles, providing that their underlying classification is sound. Problems were encountered with the butyrate-producing cocci, which appear to be a more heterogeneous group of organisms than is currently acknowledged; further taxonomic studies on these organisms are required.     

Effect of hemoglobin on the development ofPseudomonas aeruginosa infection

The disease caused by injection ofP. aeruginosa suspension in a hemoglobin solution was more severe (greater weight loss and larger abscesses in primary foci) than that induced by the same dose of the microbe in Hanks' solution (control). It was supposed that in the control the viability of the microorganisms was suppressed by iron deficiency in surrounding tissues, which was particularly pronounced upon accumulation in a limited space of great numbers of bacterial cells competing with each other for iron. Iron released from hemoglobin provides better conditions for the development ofP. aeruginosa. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 125, No. 3, pp. 351–352, March, 1997     

Epidemiological analysis of Candida albicans strains by multilocus enzyme electrophoresis.

Genotypic diversity in a collection of 98 isolates of Candida albicans was assessed by multilocus enzyme electrophoresis. Four of the 10 enzyme loci studied were polymorphic. The electrophoretic patterns observed were compatible with those expected for a diploid organism. The 98 isolates were assigned to 14 electrophoretic types, each of which was represented by from 1 to 21 isolates. Samples from various clinical sites of seven bone marrow transplant patients treated in the same unit within a 13-month period were obtained repeatedly. Three patients were found to be colonized with more than one strain. In one patient, flucytosine-resistant strains were isolated after systemic antifungal treatment was started. These isolates had electrophoretic types different from those of the strains that colonized the patient before treatment. There was no evidence that cross-infection between these patients occurred in the hospital. The population structure of C. albicans is discussed in regard to the multilocus genotype data.     

Multilocus enzyme analysis of Legionella dumoffii.

Variability among 29 clinical and environmental strains of Legionella dumoffii was investigated by multilocus enzyme analysis by use of starch gel electrophoresis. Based on results of analysis at 20 enzyme loci, the strains were separated into five closely related electrophoretic types (ETs), which were clearly distinguished from 53 strains representing 53 ETs of L. pneumophila. DNA hybridization results (hydroxyapatite method, 60 and 75 degrees C) for representative strains confirmed that all L. dumoffii ETs were a single genetic species. Although multilocus enzyme analysis indicated that L. dumoffii was genetically a quite uniform species, sufficient variability existed to warrant electromorph fingerprinting for epidemiologic studies.