Serotyping of Pseudomonas aeruginosa isolates from patients with cystic fibrosis of the pancreas

Prevalence and analysis of Pseudomonas aeruginosa in chinchillas

Background

Chinchillas (Chinchilla laniger) are popular as pets and are often used as laboratory animals for various studies. Pseudomonas aeruginosa is a major infectious agent that causes otitis media, pneumonia, septicaemia enteritis, and sudden death in chinchillas. This bacterium is also a leading cause of nosocomial infections in humans. To prevent propagation of P. aeruginosa infection among humans and animals, detailed characteristics of the isolates, including antibiotic susceptibility and genetic features, are needed. In this study, we surveyed P. aeruginosa distribution in chinchillas bred as pets or laboratory animals. We also characterized the isolates from these chinchillas by testing for antibiotic susceptibility and by gene analysis.

Results

P. aeruginosa was isolated from 41.8% of the 67 chinchillas included in the study. Slide agglutination and pulsed-field gel electrophoresis discriminated 5 serotypes and 7 unique patterns, respectively. For the antibiotic susceptibility test, 40.9% of isolates were susceptible to gentamicin, 77.3% to ciprofloxacin, 77.3% to imipenem, and 72.7% to ceftazidime. DNA analyses confirmed that none of the isolates contained the gene encoding extended-spectrum β-lactamases; however, 2 of the total 23 isolates were found to have a gene similar to the pilL gene that has been identified in the pathogenicity island of a clinical isolate of P. aeruginosa.

Conclusions

P. aeruginosa is widely spread in chinchillas, including strains with reduced susceptibility to the antibiotics and highly virulent strains. The periodic monitoring should be performed to help prevent the propagation of this pathogen and reduce the risk of infection from chinchillas to humans.

Pseudomonas aeruginosa population structure revisited

At present there are strong indications that Pseudomonas aeruginosa exhibits an epidemic population structure; clinical isolates are indistinguishable from environmental isolates, and they do not exhibit a specific (disease) habitat selection. However, some important issues, such as the worldwide emergence of highly transmissible P. aeruginosa clones among cystic fibrosis (CF) patients and the spread and persistence of multidrug resistant (MDR) strains in hospital wards with high antibiotic pressure, remain contentious. To further investigate the population structure of P. aeruginosa, eight parameters were analyzed and combined for 328 unrelated isolates, collected over the last 125 years from 69 localities in 30 countries on five continents, from diverse clinical (human and animal) and environmental habitats. The analysed parameters were: i) O serotype, ii) Fluorescent Amplified-Fragment Length Polymorphism (FALFP) pattern, nucleotide sequences of outer membrane protein genes, iii) oprI, iv) oprL, v) oprD, vi) pyoverdine receptor gene profile (fpvA type and fpvB prevalence), and prevalence of vii) exoenzyme genes exoS and exoU and viii) group I pilin glycosyltransferase gene tfpO. These traits were combined and analysed using biological data analysis software and visualized in the form of a minimum spanning tree (MST). We revealed a network of relationships between all analyzed parameters and non-congruence between experiments. At the same time we observed several conserved clones, characterized by an almost identical data set. These observations confirm the nonclonal epidemic population structure of P. aeruginosa, a superficially clonal structure with frequent recombinations, in which occasionally highly successful epidemic clones arise. One of these clones is the renown and widespread MDR serotype O12 clone. On the other hand, we found no evidence for a widespread CF transmissible clone. All but one of the 43 analysed CF strains belonged to a ubiquitous P. aeruginosa "core lineage" and typically exhibited the exoS(+)/exoU(-) genotype and group B oprL and oprD alleles. This is to our knowledge the first report of an MST analysis conducted on a polyphasic data set.

Role of alginate in infection with mucoid Pseudomonas aeruginosa in cystic fibrosis

BACKGROUND

Chronic bronchopulmonary infection with mucoid, alginate producing Pseudomonas aeruginosa occurs characteristically in patients with cystic fibrosis. Alginate may be a virulence factor for P aeruginosa infection in such patients.

METHODS

Forced vital capacity (FVC), nutritional state and the antibody response to P aeruginosa were determined at regular intervals from three years before chronic P aeruginosa infection to 10 years afterwards in 73 patients with cystic fibrosis. All patients were treated intensively with antipseudomonal chemotherapy during the study period.

RESULTS

FVC was reduced in all patients who subsequently developed P aeruginosa infection before they acquired the infection, indicating significant pre-existing lung damage when compared with patients who remained free of P aeruginosa. Lung function and nutritional state remained unchanged after 10 years of infection, except in the patients who died of P aeruginosa lung infection. The FVC and height and weight of patients infected with nonmucoid strains of P aeruginosa were similar to those of uninfected patients. Patients infected with mucoid strains had poorer lung function and nutritional state for the first five years after infection compared with patients with nonmucoid strains. Such infection was also associated with greater IgG and IgA antibody responses to P aeruginosa standard antigen compared with nonmucoid infection. Concentrations of antibody to alginate were similar in patients with non-mucoid and mucoid infection. Noticeably increased concentrations of IgA antibodies to P aeruginosa standard antigen were observed early after the onset of infection in patients who subsequently died.

CONCLUSION

Alginate producing P aeruginosa infection is associated with a hyperimmune response and poor clinical condition, suggesting that alginate production is a virulence factor in such infections in patients with cystic fibrosis.

Strain differentiation of nosocomial isolates of Pseudomonas aeruginosa by pyrolysis mass spectrometry

Pyrolysis mass spectrometry (PyMS) was used for rapid interstrain comparison of Pseudomonas aeruginosa isolates from a small outbreak of sternal wound infections in a cardiothoracic surgical ward. The PyMS results were compared with those obtained by conventional O-serotyping. All the isolates were phage non-typable. Evidence obtained from PyMS of identity/non-identity between isolates correlated completely with that obtained by O-typing and correctly identified those isolates comprising the epidemic strain, in one instance in advance of O-serotyping. The speed and versatility of PyMS make it an attractive technique for the initial screening of isolates from nosocomial outbreaks of infection with P. aeruginosa and other organisms.

Pyocin typing of Pseudomonas aeruginosa isolates from children with cystic fibrosis

Pyocin typing and serotyping of 433 strains of Pseudomonas aeruginosa from children with cystic fibrosis (CF) showed that pyocin type 9 was predominant, particularly in association with polyagglutinating serotype. The common pyocin groups, 1, 5 and 10, made up only 20% of these isolates in contrast to reported rates of up to 89% in other studies using non-CF strains. No strains of pyocin type 3 were found. Polyagglutinating strains made up 72% of strains from patients colonized with P. aeruginosa for more than 12 mths. Pyocin type 9 was associated with 93% of polyagglutinating strains. The parallel between pyocin type 9 and polyagglutinating serotype suggests that these may both be characteristics acquired by P. aeruginosa colonizing patients with CF. Because of confounding between duration of colonization and exposure to cross-infection, this study does not allow definition of the role of cross-infection in determining the characteristics of these strains in most patients. In siblings, however, evidence supports a role for cross-infection either between siblings or from a common source. In 6 pairs of siblings studied, each pair had at least 1 pyocin group in common concurrently, either at entry to the study or after an interval of several months. Identical and unusual pyocin groups were recognized in samples obtained on the same day from pairs of siblings. More studies are needed to compare results of pyocin typing with methods such as genome fingerprinting to characterize these strains and determine whether the observed distribution of pyocin groups in CF isolates is related to cross-infection or whether the combination of pyocin type 9 with polyagglutinating serotype is a characteristic of CF strains.

Detection of restriction fragment length polymorphisms in clinical isolates and serially passaged Pseudomonas aeruginosa strains

An 800-base-pair HindIII-PstI fragment that flanks a hot spot for Tn7 insertion was isolated from the chromosome of Pseudomonas aeruginosa and cloned into pUC12. The fragment was used to probe XhoI digests of genomic DNA from 18 P. aeruginosa isolates collected from sputum samples of seven cystic fibrosis patients. Only two XhoI restriction fragment length polymorphisms (RFLPs), of 3.7 and 7.7 kilobases (kb), were detected. Isolate WSU3531-1 (3.7-kb XhoI fragment) and WSU3860 (7.7-kb XhoI fragment), while isolated from the same patient, showed different RFLPs. Serial passages of isolate WSU3531-1 demonstrated that this strain was phenotypically stable. In contrast, colony and pigment variants were readily isolated at a frequency of 1% from serial passages of isolate WSU3860. When XhoI-digested genomic DNA from phenotypic variants of serially passaged WSU3860 were probed with the 800-base-pair HindIII-PstI fragment, the probe hybridized to a 10.4-kb XhoI fragment from three isolates. Restriction analysis of the genomic DNA digested with a variety of restriction enzymes showed that a 2.7-kb insertion occurred in the same region for all three isolates. There appeared to be no correlation between changes in the RFLP and changes in colony morphology.

Pseudomonas aeruginosa empyema in an adult with cystic fibrosis

Pseudomonas aeruginosa is frequently grown from the sputum of adults with cystic fibrosis-related bronchiectasis. A rare case of pseudomonal empyema is reported in this clinical setting. Early diagnosis permitted successful treatment with closed needle aspiration and intravenous antibiotics.

Pseudomonas aeruginosa cross-colonization and persistence in patients with cystic fibrosis. Use of a DNA probe

To investigate cross-colonization with and persistence of Pseudomonas aeruginosa in cystic fibrosis (CF), 181 isolates from 76 CF patients were typed using a P. aeruginosa-specific DNA probe. Whereas sibling pairs predominantly harboured genotypically identical P. aeruginosa strains, all of the other patients harboured different strains. Seventy-nine per cent (22/31) of the infected CF patients harboured the same strains at the beginning and the end of a summer camp. A change of strains was seen in 10% (3/31) of the patients at the end of the camp. Forty-six per cent (6/13) of the patients who were apparently initially uninfected, acquired P. aeruginosa by the end of the period. Genotyping proved that strain change or acquisition was due to cross-colonization in four of nine cases. Very little P. aeruginosa was isolated from the inanimate environment. Persistence of P. aeruginosa after a temporary loss due to antibiotic therapy was seen in 12/16 paired patient strains before and after antibiotic therapy. Thus, suppression followed a flare-up seemed to occur in these patients rather than eradication and a new infection. When 35 patients were followed over a period of 6 months, 7 (20%) changed the strain in their sputum. Only one of 43 patients harboured two different P. aeruginosa strains simultaneously over a long period.

Significance of immunologic factors in cystic fibrosis

We specifically investigated the significance of antibodies directed against pure preparations of lipopolysaccharide antigens and also against elastase of Pseudomonas aeruginosa. Antibodies were detected by an indirect enzyme-linked immunosorbent assay technique both in serum (IgG) and in sputum (sIgA). Patients with cystic fibrosis (CF) chronically infected with Ps. aeruginosa had significantly higher antibody titers both in serum and sputum than CF patients or non-CF persons not colonized with Ps. aeruginosa. There were differences in the antibody spectrum between the colonized CF group and the two non-colonized control group. The sensitivity was highest for homologous O-specific IgG in serum (91.9%), followed by homologous O-specific sIgA in sputum (79.4%) and sIgA anti-elastase in sputum (66.2%). O-specific IgG antibodies in serum indicate a previous contact with various O-antigens of Ps. aeruginosa rather than reflect the present condition of the patient. In the evaluation of the current status sIgA O-specific antibodies in sputum are an appropriate indicator, with titers increasing during acute exacerbations and decreasing to normal values subsequently.

Colonial dissociation and susceptibility to phagocytosis of Pseudomonas aeruginosa grown in a chamber implant model in mice

Pseudomonas aeruginosa strains were grown in 1-cm plastic chambers sealed at both ends with porous Millipore filters and implanted in the peritonea of mice. Mucoid and nonmucoid strains of P. aeruginosa isolated from a patient with cystic fibrosis largely retained their phenotypes when grown for up to 1 year in this in vivo system, although colonial dissociation occurred, as observed in chronic lung infections of patients with cystic fibrosis. In the absence of added opsonins, P. aeruginosa M2 cells taken directly from the in vivo system were significantly more susceptible to phagocytosis than were the same P. aeruginosa cells after being washed in buffer. Phagocytosis of in vivo-grown P. aeruginosa cells could be further enhanced by using a porin protein F-specific monoclonal antibody.

Alginate production by clinical nonmucoid Pseudomonas aeruginosa strains

The slime material from a revertant nonmucoid variant, derived by serial passage of a heavily mucoid Pseudomonas aeruginosa strain isolated from a patient with bacteremia, was found to contain 16% uronic acids, 48.5% carbohydrates, 11% protein, and 2% lipids. Chromatographic analysis by ion exchange chromatography revealed that this extracellular material consisted of three fractions, one uronic acid fraction with properties similar to those of the alginate fraction of the parental strain and two other fractions consisting of neutral sugars and proteins in approximately a 5:1 ratio. In addition, the slime material from six other clinical macroscopic nonmucoid P. aeruginosa strains was found to contain alginate. These results demonstrate that alginate production in various amounts is a property shared by all P. aeruginosa strains.

Hospital epidemiology of Pseudomonas aeruginosa from patients with cystic fibrosis

Pseudomonas aeruginosa colonizes the respiratory tract of most older patients with cystic fibrosis. The means by which these bacteria are acquired and the risk for patient-to-patient spread among subjects with cystic fibrosis are poorly understood. We studied the spread of Ps. aeruginosa within a hospital environment. Pseudomonas was rarely recovered from the inanimate environment surrounding patients with cystic fibrosis or from hand or rectal cultures of patients who were colonized in the oropharynx. There was transient cross-colonization with Ps. aeruginosa between patients with cystic fibrosis sharing a hospital room in three of seven pairs studied. In all cases the "new" isolate was recoverable only once and was not found during a 2-year follow-up. Three of four sibling pairs with cystic fibrosis shared the same Ps. aeruginosa serotype(s). The risk of sustained cross-colonization by Ps. aeruginosa between patients with cystic fibrosis appears to be minimal, except under conditions of prolonged close contact.

Nonfatal bacteremia caused by a mucoid, alginate-producing strain of Pseudomonas aeruginosa

The first case of mucoid Pseudomonas aeruginosa bacteremia is reported in a hospitalized 78-yr-old woman with drug-induced hepatitis attributed to antituberculous therapy. The bacteremia was successfully treated with tobramycin and carbenicillin. Furthermore, the extracellular material of this mucoid strain was extracted, purified, and characterized as an alginate of high molecular weight, similar to that of mucoid Pseudomonas aeruginosa strains from cystic fibrosis.

Does centralized treatment of cystic fibrosis increase the risk of Pseudomonas aeruginosa infection?

Two hundred and forty Danish patients with cystic fibrosis (97% of the total CF population in Denmark) participated in a point-prevalence study of Pseudomonas aeruginosa infection. One hundred and ninety-two patients were treated at the Danish CF centre and 48 patients were treated in other places. The age distribution was significantly different as no patients older than 19 years were found in the non-centre group. Pathogenic bacteria were isolated from the sputum of 96% of the patients. P. aeruginosa was more prevalent in patients from the centre, whereas Staphylococcus aureus was more prevalent in the non-centre group. No difference in serogroup and phage pattern of P. aeruginosa was found. There was a tendency that non-centre treated patients acquired chronic broncho-pulmonary P. aeruginosa infection later, but at the age of 16 years 90% of all patients will be chronically infected. Chronic P. aeruginosa infection was significantly more common in the age group 10-14 years at the centre than outside the centre. It is not possible to prevent chronic P. aeruginosa infection in CF patients treated in small groups and because of the better prognosis of centralized treatment the latter must be recommended.

Pseudomonas aeruginosa isolates: comparisons of isolates from campers and from sibling pairs with cystic fibrosis

Sputum or deep throat specimen cultures were obtained from 47 cystic fibrosis (CF) patients residing together at an eight-day summer camp. Pre-camp, initial day, final day and post-camp cultures were obtained and Pseudomonas aeruginosa isolates were characterized by morphology, serotype, pigment production, serum sensitivity, antibiotic susceptibility patterns, hemolysis on blood agar, and CO2 growth requirement. Of the 47 patients, four were not chronically colonized with Pseudomonas and did not become colonized at camp. Analysis of the isolates from the other 43 revealed no significant alteration in the Pseudomonas colonization pattern. Cultures obtained from four sibling pairs among the campers and from 20 additional pairs of siblings revealed that siblings in 20/24 pairs had at least one identical serotype in common. Of the criteria used for characterization, serotyping was the most definitive method for strain identification. Serotyping by both the Homma system and the International system did not detect any serotype at a frequency of more than 31%. In this study, the predominant P. aeruginosa strain of the colonized patients did not change, and non-colonized individuals did not become colonized with P. aeruginosa.

Proteins of the cystic fibrosis respiratory tract. Fragmented immunoglobulin G opsonic antibody causing defective opsonophagocytosis

In the disease cystic fibrosis (CF), pulmonary infection with Pseudomonas aeruginosa is a common clinical complication that determines most morbidity and almost all excess mortality. We postulated that in this disease a defect in Pseudomonas-reactive IgG antibodies may contribute to chronic Pseudomonas infections. Bronchoalveolar lavages were performed upon 13 patients with CF, 7 patients with chronic bronchitis characterized by recurrent Pseudomonas infections, and 4 normal volunteers. The levels of various proteins important to host defenses and proteases were determined; enzyme inhibition studies were performed. CF respiratory immunoglobulin levels were significantly elevated when compared with both normals and patients with chronic bronchitis (P less than 0.05). Albumin and transferrin levels were decreased in the CF lung fluids. CF elastolytic activity was strikingly elevated (means = 6.02 micrograms/mg total protein) and the inhibitory profile suggested such activity resembled a serine-proteinase. Alpha-1-antitrypsin antigenic levels were not altered in CF respiratory fluids. There was a tendency for the lavage IgG to fall as elastase levels rose (r = -0.29). IgG opsonins for two Pseudomonas immunotypes were isolated with affinity chromatography for functional and immunochemical studies. Bacterial phagocytic rates in the presence of these Pseudomonas-reactive IgG opsonins derived from CF lavage fluid were depressed (0.3% uptake/unit time) when compared with similarly titered positive controls (uptake = 1.3%/unit time, P less than 0.001). Additionally, normal pulmonary macrophage intracellular killing of Pseudomonas was severely altered in the presence of opsonins derived from CF respiratory fluids. At some time points, less than 30% of the bacteria were killed. CF IgG opsonins contain a cleavage fragment (100,000 D, 5S sedimentation coefficient) with antigenic determinants similar to the Fab portion of IgG. The presence of such a fragment was inversely correlated with phagocytic functional activity. Intact IgG comprised as little as 18% of the CF lavage fluid specimens. Aliquots of intact human IgG, when mixed with the CF opsonins, augmented Pseudomonas uptake and improved intracellular killing. Conversely, peptide fragments of IgG opsonins, which are proteolytically derived in vitro, duplicated in our system the defect observed with opsonins derived from CF lung fluids; bacterial uptake was inversely related to the concentration of F(ab')2 and to a greater degree, to Fc present in the opsonic mixture. We concluded that IgG respiratory opsonins are fragmented, inhibiting phagocytosis and serving a permissive role in the chronic Pseudomonas pulmonary infection in the disease CF.

Pseudomonas aeruginosa isolates from patients with cystic fibrosis: a class of serum-sensitive, nontypable strains deficient in lipopolysaccharide O side chains

Twenty-six Pseudomonas aeruginosa strains from patients with cystic fibrosis were typed by the Fisher immunotyping scheme. Only 6 strains were agglutinated by a single typing serum, whereas 15 strains were agglutinated with more than one serum and 5 were not agglutinated by any serum. Neither the polyagglutinable nor the nonagglutinable strains were typable by hemagglutination inhibition or immunodiffusion, suggesting that these polyagglutinable strains did not express multiple serotype antigens, but were instead being agglutinated by antibody to nonserotype determinants. Four typable isolates were resistant to pooled normal human serum, whereas the 12 polyagglutinable and nonagglutinable isolates studied were very sensitive to normal human serum. The outer membranes of 16 strains were isolated and characterized. The data suggested, in general, strong conservation of outer membrane protein patterns. Lipopolysaccharides (LPS) were purified by a new technique which allowed isolation of both rough and smooth LPS in high yields. Three of four typable, serum-resistant strains examined had amounts of smooth, O-antigen-containing LPS equivalent to our laboratory wild type, P. aeruginosa PAO1 strain H103. In contrast, 10 of 12 polyagglutinable or nonagglutinable, serum-sensitive strains had very little or no smooth, O-antigen-containing LPS, and the other two contained less smooth LPS than our wild-type strain H103. In agreement with this data, five independent, rough, LPS O-antigen-deficient mutants of strain H103 were nontypable and serum sensitive. We suggest that the LPS defects described here represent a significant new property of many P. aeruginosa strains associated with cystic fibrosis.

The serum sensitivity, colonial morphology, serogroup specificity, and outer membrane protein of Pseudomonas aeruginosa strains isolated from several clinical sites

Ninety-three strains of Pseudomonas aeruginosa, isolated from 68 patients hospitalized with respiratory tract infections, burns, urinary tract infections, and other illnesses, were examined for: 1) sensitivity to the bactericidal activity of fresh normal human serum (FHS); 2) colonial morphology; 3) serogroup designation; and 4) outer membrane protein (OMP) profile. The purpose of this study was to determine if there was any relationship between any of these microbial characteristics and the propensity of this microorganism to infect a specific clinical site or tissue. The results of this study can be summarized as follows: 1) slime-producing strains were generally more serum-sensitive than non-slime producers, although serum sensitivity was not related to slime production per se; 2) CF strains were much more serum-sensitive than non-CF strains; 3) the clinical isolation site appeared to be the predominant determinant of a strain's sensitivity to FHS; 4) the ability of P. aeruginosa to colonize/infect a specific clinical site or resist the bactericidal activity of FHS was generally unrelated to serogroup specificity; and 5) whereas the OMP profile of a particular strain does not appear to correlate with its response to the bactericidal effect of FHS, it does appear to be related to its clinical isolation site.

Chronic colonization of rat airways with Pseudomonas aeruginosa

Colonization of the airways of rats by Pseudomonas aeruginosa was established by treating the animals with hexamethylphosphoramide (HMPA) and inoculating with P. aeruginosa. Male Sprague-Dawley rats were given tap water (controls) or HMPA in the drinking water at 2 or 4 mg/ml. The ciliated cells of the airway epithelium were denuded, and microulcerative lesions in the epithelium were induced in the HMPA-treated rats. After 2 weeks of treatment, the rats were inoculated by transoral intratracheal instillation with 5 X 10(7) CFU of P. aeruginosa obtained from a cystic fibrosis patient. Two weeks after inoculation, P. aeruginosa was cultured from the airways, and scanning and transmission electron microscopy showed bacilli adhering to or invading the injured airway epithelium. P. aeruginosa was present in tracheal and intrapulmonary tissue homogenates of 9% of the P. aeruginosa-inoculated control rats (n = 22) as compared with 61% of the 2-mg/ml (n = 18) and 65% of the 4-mg/ml (n = 20) HMPA-treated rats (P less than 0.05). No dose-response relationship was found between 2 and 4 mg of HMPA per ml and colonization. Contamination of 47% of all of the rats with Mycoplasma pulmonis, as indicated by a positive enzyme-linked immunosorbent assay for immunoglobulin G, had no discernible significant effect on colonization by P. aeruginosa. These results indicate that colonization of the rat airway by P. aeruginosa can be achieved experimentally by treating the animals with HMPA. This research supports the hypothesis that colonization by P. aeruginosa may occur in airways where the ciliated epithelium has been injured and epithelial lesions exist.

Phenotypic differences among clinically isolated mucoid Pseudomonas aeruginosa strains

Mucoid strains of Pseudomonas aeruginosa isolated from patients with cystic fibrosis or urinary tract infections displayed many phenotypic differences. The ratios of D-mannuronosyl to L-guluronosyl moieties of the extracellular alginate-like polysaccharides produced by the 19 strains examined varied from 99 to 0.8; the acetyl content of the polymers varied from 0.38 to 0.02 mol per mole of uronosyl residue. The strains also differed with regard to the stability of the mucoid phenotype. Of 15 isolates from patients with cystic fibrosis, 7 displayed stable mucoid phenotypes; 8 isolates were unstable and reverted to the nonmucoid phenotype at high frequency. The four strains isolated from patients with urinary tract infections were also unstable. Strains from urinary tract infections expressed the mucoid phenotype on six different media, both minimal and complex, whereas cystic fibrosis-associated strains varied widely with regard to medium-dependent expression of the mucoid phenotype. Of 15 cystic fibrosis strains, 5 were mucoid on each of six different media, 4 were mucoid on five media, 1 was mucoid on four media, 4 were mucoid on three media, and 1 yielded mucoid colonies on only one of the six media tested. There was no obvious correlation among polysaccharide structure, stability of the mucoid phenotype, and medium-dependent expression of the mucoid phenotype for any of the 19 strains investigated. These data suggest that although mucoid strains of P. aeruginosa must share some common property related to their ability to colonize their host, this property seems to be unrelated to polysaccharide composition, medium-dependent expression of the mucoid phenotype, or stability of the mucoid phenotype.

Does pseudomonas cross-infection occur between cystic-fibrosis patients

Over a 12-months period respiratory Pseudomonas aeruginosa isolated from CF patients were typed by serology and pyocin production to determine whether cross-infection was occurring. Results of typing were interpreted in relation to the degree of contact patients had with each other. One strain appeared in 4 unrelated patients. However, since none of these patients had been in contact with each other the strains considered to have been acquired from the environment. Each of six pairs of siblings shared the same strain, but the pairs of strains were distinct from each other. These results suggest that the environment is the most important source of Pseudomonas strains for CF patients and that for cross-infection to occur prolonged intimate contact is required.

Antibody response to Pseudomonas aeruginosa exoproducts in cancer patients

We analyzed sera from 28 patients with various types of malignancies for the occurrence of antibodies against exotoxin A of Pseudomonas aeruginosa and two Pseudomonas proteases. A total of 27 of these individuals were colonized or infected with P. aeruginosa at one time or another during the study, whereas the remaining patient was colonized with four non-P. aeruginosa species of Pseudomonas. Sera were obtained from several of these patients before P. aeruginosa colonization or infection of these individuals was detected, which provided an opportunity to evaluate their responsiveness to pseudomonal exoproducts as they acquired the organism. Exotoxin A was purified from culture supernatant fluids of strain PA-103, and the two proteases were purified from an isolate of strain JR3, a highly proteolytic strain originally recovered from the sputum of a cystic fibrosis patient. Antibodies to the exotoxin A and the two proteases were detected in these sera, and sera which contained relatively high antibody levels to exotoxin A afforded mice complete protection against lethal challenges with this substance. Statistical analyses showed that patients infected with P. aeruginosa had consistently higher antibody levels (P less than 0.005) to the exoproducts than patients who were colonized with this organism. Also, patients colonized with P. aeruginosa possessed significantly higher antibody levels (P less than 0.003) to these three exoproducts than uninfected, hospitalized patients. Parke-Davis type 1 was the strain most commonly isolated from these patients (46%), but colonization or infection due to this organism usually resulted in the production of low levels of antibody to Pseudomonas exoproducts. However, infections with Parke-David type 7 organisms were always associated with intermediate- and high-responder sera to exotoxin A. These results indicated that potentially toxic products were elaborated during the course of cancer-related colonization and infection with P. aeruginosa.

Active immunization with lipopolysaccharide Pseudomonas antigen for chronic Pseudomonas bronchopneumonia in guinea pigs

Chronic respiratory infection with Pseudomonas aeruginosa is a leading clinical problem among patients with cystic fibrosis. Because antimicrobial agents are usually ineffective in eradicating these infections, additional therapeutic or prophylactic measures should be considered. In this study, an experimental guinea pig model of chronic Pseudomonas aeruginosa bronchopneumonia was utilized to determine whether active immunization with lipopolysaccharide (LPS) P. aeruginosa antigen may favorably influence the course of this infection. Experimental pneumonia was established by tracheobronchial instillation of suspensions of microscopic agar beads, which were impregnated with viable P. aeruginosa. After 4 wk of infection, the geometric mean (reciprocal) passive hemagglutinating Pseudomonas antibody titer was 185+/-1.3, and lungs contained 16.8+/-4 x 10(3) colony-forming units Pseudomonas/ml of lung homogenate. Pseudomonas immunization, given prior to a 4-wk infection, resulted in significantly higher passive hemagglutinating titers (474+/-1.4; P < 0.05), lower numbers of viable Pseudomonas in lung tissues (2.4+/-0.6 x 10(3); P < 0.01), and reduced histopathology in lungs. In contrast, providing Pseudomonas immunization to animals 2 wk after pulmonary infection was established, offered no apparent benefit. Likewise, no protection was afforded by prophylactic immunization with a non-Pseudomonas LPS antigen (Escherichia coli J5 vaccine). Using a Raji cell assay, modified to detect circulating immune complexes in vaccinated and infected guinea pig sera, there was no evidence that active immunization increased the frequency of circulating immune complexes in infected guinea pigs. It is concluded that prophylactic immunization with Pseudomonas LPS antigen may confer protection from subsequent Pseudomonas bronchopneumonia, but that immunization during established infection is not beneficial.

Cystic fibrosis pseudomonas opsonins. Inhibitory nature in an in vitro phagocytic assay

Pseudomonas aeruginosa infection plays a primary pathogenetic role in the chronic respiratory tract disease of cystic fibrosis (CF) patients. Despite pronounced humoral immune responses, reflected by high levels of antibodies against Pseudomonas in serum and in sputum, the antibodies do not eliminate this bacterium. In the present study we have used affinity chromatography with a lipopolysaccharide substituted immunoadsorbent gel to isolate high titers (meanCF = 1:256) of immunotype specific Pseudomonas IgG antibodies from the sera of nine CF subjects, and have evaluated the functional ability of these antibodies to promote phagocytosis and intracellular killing of P. aeruginosa in an in vitro human alveolar macrophage culture system. The phagocytic and intracellular bactericidal kinetics revealed that CF IgG antibodies function in an inhibitory fashion. Both the rate of phagocytosis (rateCF = 204 cpm/unit time) and absolute bacterial uptakes maximal at 120 min (uptakeCF = 18 x 10(3) 14C cpm) were inhibited compared with appropriate positive controls (hyperimmune serum, HIS; [rateHIS = 399; uptakeHIS = 29 x 10(3), P less than 0.005]). The ability of such CF-derived opsonins to potentiate macrophage intracellular bactericidal processes was mildly impaired (bacterial survivalCF = 15 x 10(3) colony forming units (CFU)/min, survivalHIS = 9 x 10(3)). Further characterization of this defect, assessed with functional studies of the Fab and Fc portions of the immunoglobulin molecule, revealed an impairment in the attachment of these specific antibodies to the alveolar macrophage membrane Fc gamma receptors. Preliminary studies of the physical-chemical properties of these immunoglobulins were normal. The expression of this inhibitory activity in vivo may facilitate Pseudomonas colonization and the subsequent established infections in the respiratory tracts of CF subjects.

Mucoid Escherichia coli in cystic fibrosis

Patients with cystic fibrosis commonly harbor in their lungs strains of Pseudomonas aeruginosa that have a mucoid coating considered virtually pathognomonic for the disease. We found that strains of Escherichia coli with a morphologically similar mucoid coating were present in the respiratory tracts of eight (11.8 per cent) of 68 patients with cystic fibrosis whose sputum cultures yielded Esch. coli, as compared with none of 89 patients without cystic fibrosis who had Esch. coli in sputum. Mucoid strains of Esch. coli were also recovered from the stools of five (11.1 per cent) of 45 patients with cystic fibrosis, as compared with one (0.7 per cent) of 150 patients without cystic fibrosis. The mucoid substances purified from Esch. coli were biochemically and antigenically distinct from those of P. aeruginosa. We conclude that the respiratory tract in cystic fibrosis offers an environment conducive to the production of a mucoid coating not only by P. aeruginosa but by other gram-negative bacilli as well.

Role of adherence in the pathogenesis of Pseudomonas aeruginosa lung infection in cystic fibrosis patients

A correlation has been demonstrated between the in vitro adherence of Pseudomonas aeruginosa to upper respiratory tract epithelium and colonization of the respiratory tract by this organism. Twenty patients with cystic fibrosis (CF) and 20 age-matched controls were examined in this study. All of the CF patients but none of the controls were colonized with P. aeruginosa at the time of study. P. aeruginosa adherence to isolated epithelial cells, as determined by an in vitro assay, was 19.1 +/- 1.1 bacteria per buccal epithelial cell in the CF patients and 2.3 +/- 0.3 bacteria per cell in the controls (P < 0.01). P. aeruginosa strains of the mucoid colony type adhered in significantly lower numbers to buccal epithelial cells than did strains of the rough colony type (1.8 + 0.1 versus 24.8 +/- 0.9, P < 0.001). This difference might explain the common observation that the initial pseudomonas colonization of the respiratory tract of CF patients is due to organisms of the rough colony type. We have further demonstrated that increased P. aeruginosa adherence in vitro varies directly with the loss of a protease-sensitive glycoprotein, fibronectin, from the cell surface, as well as increased levels of salivary proteases in CF patients. When examined by a direct radioimmune binding assay, buccal cells from CF patients possessed only 17% of the total cell surface fibronectin present on similar cells obtained from controls. Salivary protease levels, as measured by (125)I release from an (125)I-labeled insoluble fibrin matrix, were increased about threefold in CF patients versus controls. Thus, colonization of the respiratory tract by P. aeruginosa in CF patients correlates well with buccal cell adherence of this organism; increased adherence is associated with decreased amounts of fibronectin on respiratory epithelial cell surfaces and increased levels of salivary proteases.

Use of Pseudomonas aeruginosa lipopolysaccharide immunoadsorbents to prepare high potency, mono-specific antibodies

Potent, mono-specific anti-Pseudomonas immunoglobulins were isolated from serum and lung lavage fluid from patients with cystic fibrosis using immunotype specific Pseudomonas aeruginosa lipopolysaccharide (LPS) substituted immunoadsorbent gel. Iodinated monovalent Pseudomonas LPS somatic antigens, Fisher immunotypes, were used as ligands for two different insoluble gel matrices. LPS iodination, using the water insoluble chloroglycoluril reagent, permitted quantitation of the percent LPS bound as a ligand. The coupling efficiencies of epoxy-activated and cyanogen bromide-activated Sepharose matrices for various Pseudomonas immunotype specific LPS preparations were compared. Although each of the 7 LPS somatic antigens produced an equivalent amount of coupling, higher percentages of coupling were found using the cyanogen bromide-activated gel when compared to the epoxy-activated gel. IgG fractions prepared from cystic fibrosis sera and lung lavage fluid were passed through the LPS affinity gels, and Pseudomonas LPS immunotype specific antibodies were eluted. The presence of specific antibody activity against individual Pseudomonas immunotypes was determined with a passive micro-hemagglutination assay. Bronchial lavage fluid seemed to be as effective as serum as a source of Pseudomonas specific antibody. Use of such a LPS substituted gel permits direct recovery of Pseudomonas monospecific antibodies suitable for physical-chemical analyses and for biologic functional assays.

Epidemiology of Pseudomonas aeruginosa infection in patients treated at a cystic fibrosis centre

484 isolates of P. aeruginosa were obtained from the respiratory tract of 45 out of 70 cystic fibrosis (CF) patients of monthly examinations during one year at the Danish CF Centre. All isolates were serogrouped (O-antigens) and phage typed, and in this way 99 per cent of the isolates could be grouped and/or typed. The isolates from CF patients belonged to many different sero-groups, but 55 per cent were polyagglutinable, and most of these belonged to the 0-3/9 complex. This was significantly different from the distribution into O-groups of isolates obtained from non-CF patients. The results of the combined phage typing and sero-grouping of the isolates revealed the occurrence of 13 clusters of distinct epidemiological types of P. aeruginosa among small groups (2-10 individuals) of CF patients. The predominating endemic strain, which was isolated from 10 (22 per cent) of the patients, belonged to the 0-3/9 complex and was lysed by phage 109, either alone or in combination with a few other phages. Furthermore, in a few cases the eradication of another strain of P. aeruginosa by chemotherapy was followed by colonization of the lungs with the above-mentioned predominating strain, and this strain was associated with high lethality. According to these results, measures should be undertaken to identify and eliminate routes of cross-infection in CF centres in order to diminishe the prevalence of P. aeruginosa infection and thereby reduce the lethality of CF patients.

Serotypes and antibiotic susceptibilities of Pseudomonas aeruginosa isolates from single sputa of cystic fibrosis patients

A phenotypic characterization of Pseudomonas aeruginosa from single sputum samples of 21 typical cystic fibrosis patients indicated a high frequency of heterogeneity among isolates on the basis of differences in antibiotic resistance, colony morphology, pigmentation, and serotype. Two or more isolates with different but stable susceptibilities to carbenicillin, gentamycin, streptomycin, tetracycline, chloramphenicol, and sulfamethoxazole plus trimethoprim were detected in 38% of the sputa. Differences generally were independent of the mucoid state of the strain. O-antigen group determination with the Difco typing set showed that two or more serologically distinct strains were present in 10/21 sputum specimens. Nonmucoid derivatives of mucoid isolates almost always retained both the antibiotic susceptibilities and serotype of their parent strain. These data suggest that cystic fibrosis patients may be cocolonized/coinfected by different strains of P. aeruginosa more frequently than generally believed. Alternatively, phenotypically distinct strains from a single patient might arise as phenotypic dissociants from a single infecting strain. Because of the frequency and multiplicity of phenotypically distinct P. aeruginosa isolates which we obtained from our cystic fibrosis patients, it is important to select multiple isolates from sputum cultures for antimicrobial susceptibility testing so as to assess adequately the susceptibility of this organism to antibiotic therapy in cystic fibrosis. We recommend that several colonies of each distinguishable colony type of P. aeruginosa be pooled for the antibiogram.

R-factor inheritance and plasmid content in mucoid Pseudomonas aeruginosa

Eighteen strains of alginate-producing mucoid Pseudomonas aeruginosa were evaluated with respect to plasmid content and the ability to maintain well-characterized R plasmids. The spontaneous loss of alginate production in these strains varied from 0.01 to 0.7% and was not significantly increased by plasmid curing regimens. Examination of cleared lysates of these strains and their isogenic nonmucoid derivatives by agarose gel electrophoresis failed to reveal plasmid DNA. R-plasmid (P-incompatibility-group) transfer to mucoid P. aeruginosa was unaffected by the presence of the alginate capsule. Maintenance and expression of such plasmids in the mucoid strains were confirmed by agarose gel electrophoresis and by verification of plasmid-linked drug resistance and pilus-specific bacteriophage sensitivity. These studies demonstrate that alginate production does not appear to be plasmid linked and that mucoid P. aeruginosa are capable of receiving and donating certain drug resistance plasmids. Since some of the plasmids used here have been shown to mobilize chromosomal DNA, strains constructed in this study should afford the means for exploring the genetic basis of the mucoid phenotype.