Pyocin Typing Research Articles

Pyocin typing of Pseudomonas aeruginosa.

Over the last 10 years, pyocin typing has been a useful tool for the epidemiological fingerprinting of Pseudomonas aeruginosa. The widely used scrape-andstreak method of Gillies and Govan, although simple to perform, has not been sensitive enough in differentiation of strains. Use of additional indicator strains might correct this deficiency. The growth-in-broth method of typing has shown promise; because it is easily automated, it may become the method of choice when very sensitive results are required. The value of pyocin typing appears to be well established in the study of nosocomial infections; however, in some situations it may give misleading results. Further studies are required for demonstration of the relative value and relationships of serological, pyocin, and bacteriophage typing.

Properties of R Plasmids Determining Gentamicin Resistance by Acetylation in Pseudomonas aeruginosa

Two clinical isolates of Pseudomonas aeruginosa, one a pyocin type 5 strain from Atlanta, could transfer gentamicin resistance by conjugation. Donor and recipient strains inactivated gentamicin by acetylation. The R plasmids, pMG1 and pMG2, also determined resistance to sisomicin, another substrate of gentamicin acetyltransferase I, sulfonamides, and streptomycin, but not resistance to kanamycin, neomycin, tobramycin, butirosin, or BB-K 8. They were transmissible to many strains of P. aeruginosa, including a Rec(-) strain, but not to Escherichia coli or other enterobacteriaceae. These R plasmids were compatible with R plasmids transmissible to P. aeruginosa from E. coli, including members of C, N, P, and W incompatibility groups. From a strain carrying pMG1 and a compatible plasmid, pMG1 was transferred independently but transfer of the second plasmid often resulted in cotransfer of pMG1. In contrast, pMG1 and pMG2 were incompatible with pseudomonas R plasmids R931 and R3108, and with R931 they readily formed recombinant plasmids. The four plasmids in this incompatibility group determine additional biological properties, including resistance to inorganic and organic mercury compounds, to ultraviolet light, and to certain deoxyribonucleic acid phages. pMG1 and pMG2 also phenotypically inhibited pyocin production. Consequently such R plasmids alter the phage and pyocin types of their host strains.

Resistance of Pseudomonas aeruginosa to Gentamicin and Related Aminoglycoside Antibiotics

This study was undertaken to investigate biochemical, genetic, and epidemiological aspects of resistance to aminoglycoside antibiotics among 650 consecutive isolates of Pseudomonas aeruginosa from Parkland Memorial Hospital, Dallas, Tex. In 364 strains, minimal inhibitory concentrations were 25 mug/ml or greater for gentamicin (G), tobramycin (T) or kanamycin (K). Four patterns of resistance were noted: (A) G, T, K (four strains), (B) G, K (23 strains), (C) T, K (one strain), and (D) K (336 strains). Gentamicin acetyltransferase (GAT) activities were associated with resistance to gentamicin in strains of groups A and B, whereas kanamycin phosphotransferase activity was found in strains of group D. The GAT from group B strains acetylates both gentamicin and tobramycin. Resistance to gentamicin and susceptibility to tobramycin may reflect the fact that the K(m)'s for tobramycin (25 to 44 mug/ml) of GAT activities in these group B strains are much greater than the K(m)'s for gentamicin (1.9 to 2.7 mug/ml) and exceed the minimal inhibitory concentrations for tobramycin (1.25 to 7.5 mug/ml). GAT from strains of group A was associated with resistance to G, T, and K. Gentamicin acetyltransferases can be distinguished by their specificities for aminoglycoside substrates. The substrate specificity of GAT from group B strains is similar to that reported for GAT(I), but the specificity of GAT from group A strains differs from those described for GAT(I) and GAT(II). Conjugal transfer of gentamicin or tobramycin resistance from our strains of P. aeruginosa to various potential recipient strains was not observed. Pyocin typing showed that many, but not all, of the strains resistant to gentamicin were similar, and retrospective epidemiological investigation revealed that these strains were isolated almost exclusively from patients in the adult and pediatric burn intensive care units and geographically continguous areas of the hospital.

Gentamicin Resistance in Pseudomonas aeruginosa : R-Factor-Mediated Resistance

By disk diffusion antimicrobial susceptibility testing, 11% of 313 consecutive strains of Pseudomonas aeruginosa, examined during July to October 1973, were resistant to gentamicin (minimal inhibitory concentration 12.5 to >100 mug/ml), and a further 31% were moderately resistant (6.25 to 12.5 mug/ml) to gentamicin at the University of Alberta Hospital in Edmonton, Canada. Of 45 gentamicin-resistant strains from that hospital, none possessed R-factors or gentamicin-inactivating enzymes. Eight of 13 strains obtained from three American sources, which contained gentamicin-acetylating (12 strains) or -adenylating (1 strain) activity, conjugally transferred both gentamicin resistance and antibiotic-inactivating activity. P. aeruginosa recipients were much more effective for detection of transferable gentamicin resistance than Escherichia coli recipients, although not all P. aeruginosa were equally as effective as recipients. One strain, POW 151, transferred resistance to both carbenicillin and gentamicin as well as to several other antibiotics. R-factors detected belonged to P-2 and P-3 (Com 6, C) incompatibility groups. Expression of gentamicin resistance due to acetylation of gentamicin was subject to marked phenotypic lag, especially in recipient strain P. aeruginosa 280. This was shown to result in the failure to detect gentamicin resistance transfer if the concentration of gentamicin in selection media was too high (>2.5 mug/ml for strain 280). Some but not all recipients were changed in pyocine type upon acquisition of R-factors.

SIGNIFICANCE OF PYOCINE TYPING IN CHRONIC PULMONARY DISEASE

While pulmonary infection in cystic fibrosis (CF) is most often initially due to S.aureus, P.aeruginosa often emerges as the major pathogen. The latter may be typed by susceptibility to pyocines, antibacterial substances produced by certain P.aeruginosa and active only against certain other P.aeruginosa. To understand the role of this organism in the bacterial ecology of the respiratory tract, pyocine typing, utilizing NIH indicator strains, was performed on multiple P.aeruginosa isolates from 100 chronic pulmonary disease patients with and without CF, classified according to clinical condition. No specific types were characteristic of non-CF patients, but N-7, N-9, N-ll, N-13, and N-27 were most common to CF patients. Types N-7 and N-ll were found most frequently in those with severe impairment or exacerbation of pulmonary disease, while N-1 and/or N-4 was associated with improvement. Of CF patients in good clinical condition, 33% had N-1 and/or N-4, compared to only 15% of CF patients with severe impairment. Pyocines produced by N-1 and N-4 P.aeruginosa in vitro inhibit N-7 and N-11, but pyocines produced by N-7, N-9, N-11, N-13, and N-27 do not inhibit N-1 and N-4. It is concluded, therefore, that the presence of N-1 and/or N-4 P.aeruginosa may inhibit colonization by P.aeruginosa characteristic of more severe disease as can occur among staphylococci in other clinical conditions.

Aeruginocine typing of Pseudomonas aeruginosa.

Aeruginocine typing using eight indicator strains of Wahba on Bacto tryptone-glucose yeast extract Agar (Difco) with an incubation temperature of 32 degrees C was found to be a reproducible and easy method which could be readily adopted by a diagnostic clinical laboratory. The results of aeruginocine typing of 1500 strains of Ps. aeruginosa suggest that hospitals differ in the range and patterns of aeruginocine types of strains isolated in them. In addition to representatives of nine of the 10 pyocine types of Wahba, a large number of strains isolated in India were found to fall into other groups not described in Wahba's system. Hence, 20 new inhibition patterns (aeruginocine types) are proposed.

Susceptibility of 1,500 isolates of Pseudomonas aeruginosa to gentamicin, carbenicillin, colistin, and polymyxin B.

A series of 1,500 strains of Pseudomonas aeruginosa was collected from a variety of sources to provide a group of strains which would truly represent the species. All of them were pyocine typed, and a wide range of types was included among the isolates from each source. The gentamicin, carbenicillin, colistin, and polymyxin minimal inhibitory concentration of each strain was measured by the agar dilution method employing the Steers inocula replicator. Over 99% of strains were inhibited by 8 mug of gentamicin per ml, by 256 mug of carbenicillin per ml, and by 4 mug of colistin per ml. The small number of strains more resistant to each antibiotic comprised a variety of different pyocine types. Few strains were found to be susceptible to tetracycline, chloramphenicol, kanamycin, or streptomycin at the single concentration tested.

Agricultural Plants and Soil as a Reservoir for Pseudomonas aeruginosa

Pseudomonas aeruginosa was detected in 24% of the soil samples but in only 0.13% of the vegetable samples from various agricultural areas of California. The distribution of pyocin types of soil and vegetable isolates was similar to that of clinical strains, and three of the soil isolates were resistant to carbenicillin. Pseudomonas aeruginosa multiplied in lettuce and bean under conditions of high temperature and high relative humidity (27 C and 80-95% relative humidity) but declined when the temperature and humidity were lowered (16 C, 55-75% relative humidity). The results suggest that soil is a reservior for P. aeruginosa and that the bacterium has the capacity to colonize plants during favorable conditions of temperature and moisture.

Introduction of Pseudomonas Aeruginosa into a Hospital via Vegetables

Pseudomonas aeruginosa was isolated from tomatoes, radishes, celery, carrots, endive, cabbage, cucumbers, onions, and lettuce obtained from the kitchen of a general hospital, with tomatoes yielding both highest frequencies of isolation and highest counts. Presence of P. aeruginosa on the hands of kitchen personnel and cutting boards and knives which they used suggests acquisition of the organism through contact with these vegetables. It is estimated that a patient consuming an average portion of tomato salad might ingest as many as 5 × 103 colony-forming units of P. aeruginosa. Pyocine types of P. aeruginosa isolated from clinical specimens were frequently identical to those recovered from vegetables, thus implicating tomatoes and other vegetables as an important source and vehicle by which P. aeruginosa colonizes the intestinal tract of patients.

Pyocin-sensitivity testing as a means of typing Pseudomonas aeruginosa.

Summary Pyocin-sensitivity testing is a useful adjunct to a routine pyocin-typing scheme for Pseudomonas aeruginosa, permitting the subdivision of many groups of strains that belong to the same pyocin type, and also reducing the frequency of untypable strains.

EPIDEMIOLOGICAL MARKERS FOR PSEUDOMONAS AERUGINOSA

The mutual interrelationship between bacteriophage susceptibility of Pseudomonas aeruginosa and serogroup and pyocine type of the bacterial strains have been investigated. A possible interrelationship has been found only for a few phages to the effect that the phages may have preference for certain serogroups. Bacteria of the pyocine type 5 tended to be lysed more efficiently by high avidity phages than other pyocine types. Only one of the 113 phages seemed to have any preference for a given pyocine type. There was no tendency for given serogroups or pyocine types on the other hand to be lysed more frequently by certain phages than would be expected from the avidity of the phages on the entire strain collection.

EPIDEMIOLOGICAL MARKERS FOR PSEUDOMONAS AERUGINOSA

Experience with serogrouping and pyocine typing of Pseudomonas aeruginosa has been presented. The Habs serogrouping system was compared with the schemas of Homma et al., of Lányi, and of Sandvik. All the reference strains of Homma et al. were groupable by the Habs set, likewise most of the Lányi strains. The bovine Sandvik serogroup reference strains all had a Habs counterpart, except O:II which was incorporated in the Habs system as O:13. The bovine serogroup O:VIII corresponded to Habs O:8. It was considered justified to recognize the Wahba O:14 as a separate entity. The pyocine typing method of Gillies & Govan was suitable since it rendered a reasonably reproducible result. With this procedure, 96.7 per cent of the strains were typed. The major disadvantage of the method was its insufficient subdivision of the P. aeruginosa strains. Only three types constituted 65.3 per cent of the material. The data suggested a correlation between certain serogroups and pyocine types.

EPIDEMIOLOGICAL MARKERS FOR PSEUDOMONAS AERUGINOSA

On epidemiologically heterogeneous pseudomonas strains, have been compared the use of bacteriophage typing by two procedures, serogrouping and pyocine typing. The new phage typing procedure of the author was demonstrated to be preferable to a previous phage typing procedure which is extensively used. A combination of serogrouping and pyocine typing renders a good alternative typing procedure to phage typing for the bacteriological laboratories with a relatively modest load of Pseudomonas aeruginosa. Phage typing is preferable to other typing procedures in terms of rendering a high degree of differentiation and demonstrating strain relatednes in serial cultures from the same sites.

Pyocine typing of mucoid strains of Pseudomonas aeruginosa isolated from children with cystic fibrosis.

SUMMARY The relationship between mucoid and non-mucoid strains of Pseudomonas aeruginosa isolated from the sputum of children with cystic fibrosis was investigated by typing the strains by pyocine production. The mucoid strains were usually untypable by the standard technique, but extraction and assay of the pyocines produced in liquid cultures showed that the strains belonged to recognised pyocine types. When mucoid and non-mucoid strains occurred simultaneously, they were of the same pyocine type; it is suggested that they are variants of the same strain.

An epidemiological study of Pseudomonas aeruginosa in cattle and other animals by pyocine typing.

The high incidence (80.1%) of Pseudomonas aeruginosa pyocine type 1 in bovine mastitis in Israel suggested some degree of selectivity under local conditions. Contrary to other reports, cattle and calves showed a high rate of faecal carriage of this organism. The water supply on farms was often contaminated. The presence of certain pyocine types in the udder, gut or water occasionally led to their transmission from one reservoir to another; however, many types did not seem to spread.P. aeruginosa was found in association with infections in various animals and was present in many locations such as a mouse breeding house and a chick hatchery.

Intensive care unit reservoirs for pseudomonas investigated by pyocine typing

Teres, D MD; Schweers, P. MD; Bushnell, L. S. MD; Hedley-Whyte, J. MD Author Information

SOURCES OF PSEUDOMONAS ÆRUGINOSA INFECTION IN A RESPIRATORY/SURGICAL INTENSIVE-THERAPY UNIT

Monitoring of pseudomonas pyocine types from 640 patients and their environment was undertaken in a respiratory/surgical intensive-therapy unit (R.S.I.T.U.) during a nineteen-month period. Forty of fifty-six sputum or throat isolates of pseudomonas were clearly hospital acquired and at least 10 of the 16 patients who had Pseudomonas œruginosa on first culture were suspected of having hospital-acquired organisms. Pyocine types 1 and 10 were the "resident" strains; type-10 outbreaks occurred in clusters. Both types were regularly cultured from only one environmental source (the sinks), even during one to two week intervals during which no patients in the R.S.I.T.U. were colonised with pseudomonas. It is suggested that the sinks provide reservoirs of pseudomonas infection and that the hands of personnel are the vehicles of transmission.

Variability of pyocine type and pyocine sensitivity in some strains of Pseudomonas aeruginosa.

Summary: In a study of pyocine typing of 274 strains of Pseudomonas aeruginosa isolated from the same hospital, evidence of instability in 2 pyocine indicator strains and in the pyocine type of 19% of the isolates was found. An alternative approach to pyocine typing, using purified pyocine preparation, is suggested.

Epidemiology of Pseudomonas infections in a pediatric intensive care unit.

Two outbreaks of Pseudomonas infections involved 14 patients in a pediatric intensive care unit during a six-month period. Organisms of the same pyocine type were isolated from three of four patients infected during the second outbreak. Introduction of Pseudomonas aeruginosa to the unit was suspected to have occurred by patients transferred from outlying hospitals. Epidemiologic studies failed to reveal a contaminated fomes, and hospital personnel likely served as intermediaries to spread the organism within the unit. Statistically, newborn infants wre much more likely to become infected and to die from Pseudomonas infections than older patients. This report stresses the epidemic potential inherent in pediatric intensive care units, particularly those dealing with neonates. A suggested scheme for surveillance is presented.

Introduction of Pseudomonas aeruginosa into a hospital via vegetables.

Pseudomonas aeruginosa was isolated from tomatoes, radishes, celery, carrots, endive, cabbage, cucumbers, onions, and lettuce obtained from the kitchen of a general hospital, with tomatoes yielding both highest frequencies of isolation and highest counts. Presence of P. aeruginosa on the hands of kitchen personnel and cutting boards and knives which they used suggests acquisition of the organism through contact with these vegetables. It is estimated that a patient consuming an average portion of tomato salad might ingest as many as 5 x 10(3) colony-forming units of P. aeruginosa. Pyocine types of P. aeruginosa isolated from clinical specimens were frequently identical to those recovered from vegetables, thus implicating tomatoes and other vegetables as an important source and vehicle by which P. aeruginosa colonizes the intestinal tract of patients.