Plasmids of Staphylococcus aureus associated with live and processed poultry

A series of 23 strains of Staphylococcus aureus originally isolated from processed poultry was screened for the presence of plasmids. Plasmids were more common in strains of Staph. aureus characteristically associated with live poultry than with strains endemic in poultry plants and strains of human origin. Two plasmids with sizes of 1.65 and 18.2 kilobase pairs (kBp) were present in three strains considered typical of Staph. aureus forma specialis 'altilis' and two plasmids with sizes of 1.65 and 17 kBp were present in three of four strains of Staph. aureus var. gallinae. A 1.65 kBp plasmid was present in all seven strains of these poultry biotypes and in three of 14 'endemic' strains. All the 1.65 kBp plasmids were shown by blot hybridization to share sequence homology. There was also some sequence homology between the 18.2 kBp and 17 kBp plasmids. These results were supported by restriction enzyme digest analyses. A study of cured derivatives of strain PS221 f.sp. 'altilis' suggested that the 18.2 kBp plasmid encoded the genetic determinant(s) responsible for caseolysis. Both the 1.65 and the 18.2 kBp plasmids also exerted an effect on the production of acid from lactose. In no other characteristic did cured strains resemble the plasmid-free 'endemic' strains. This was therefore consistent with the notion that the genetic determinants associated with the cultural characteristics of endemic strains are chromosomally located.     

Large plasmids in ruminal strains of Selenomonas ruminantium

The plasmid content of six different isolates of Selenomonas ruminantium from the rumen of sheep, cows or goats was examined by electron microscopy. In addition to small plasmids (< 12 kb) studied previously, all six strains contained at least one plasmid larger than 20 kb. Plasmid sizes of 1·4, 2·1, 2·4, 5·0, 6·2, 20·4, 20·8, 22·7, 23·3, 29·3, 30·7, 34·4 and 42·6 kb were estimated from contour length measurements. DNA-DNA hybridization experiments revealed homology among the large plasmids from five strains, while the 20·8 kb plasmid from a sixth isolate showed no apparent relationship with the plasmids of the other strains.     

Plasmid profiles of Staphylococcus aureus causing bovine mastitis

A. B aumgartner , J. N icolet & M. E ggimann 1984. Plasmid profiles of Staphylococcus aureus causing bovine mastitis. Journal of Applied Bacteriology 56 , 159–163.
Plasmid profiles of Staphylococcus aureus , isolated from herds affected with chronic bovine mastitis, are heterogeneous, as shown by the study of 85 strains from 18 different farms. The strains isolated within a herd sometimes show related plasmid patterns, although even strains isolated from different quarters of the same udder may show variations in their plasmid content. Strains without antibiotic resistance are frequently free of plasmids. Therefore, the existence of mastitis Staph. aureus virulence plasmids is unlikely. Staphylococcus aureus , resistant to penicillin and streptomycin from 9 different farms show related plasmid patterns. This result confirms a geographic spread of certain mastitis Staph. aureus strains.     

Chlorine resistance of Staphylococcus aureus isolated from turkeys and turkey products

When tested in phosphate buffer at pH 7·0, strains of Staphylococcus aureus isolated from turkeys immediately after commercial slaughter were reduced in viability by at least 10000-fold following exposure to 1 mg/1 of free available chlorine for 2 min at 20°C. In contrast, corresponding isolates from samples taken later in the process, and apparently derived from strains capable of colonizing processing equipment ('endemic' strains), were reduced only ca 100-fold; some of these strains survived treatment with 2 mg/1 of free chlorine, when tested under the same conditions. The greater resistance of 'endemic' strains to chlorine may contribute to their persistence in the processing plant.     

Plasmids in Staphylococcus hyicus

Fifty-one strains of Staphylococcus hyicus and six of Staph. chromogenes were collected from porcine and bovine sources in England and Belgium. Antibiotic resistance and plasmid profiles were established. Plasmids associated with resistance to tetracycline, erythromycin and streptomycin were identified in many strains; these plasmids were about the same size as those mediating similar resistances in Staph. aureus of human origin. Many small cryptic plasmids were also seen.     

Plasmids in Staphylococcus hyicus

Fifty-one strains of Staphylococcus hyicus and six of Staph, chromogenes were collected from porcine and bovine sources in England and Belgium. Antibiotic resistance and plasmid profiles were established. Plasmids associated with resistance to tetracycline, erythromycin and streptomycin were identified in many strains; these plasmids were about the same size as those mediating similar resistances in Staph. aureus of human origin. Many small cryptic plasmids were also seen.     

Cadmium-resistance plasmid in Staphylococcus lugdunensis

Plasmids that confer resistance to cadmium (MIC > or = 125 microM), were found in 18 out of 30 independent Staphylococcus lugdunensis strains from clinical specimens. Variants that were cured of their plasmid were cadmium sensitive. Restriction endonuclease sites of a 3.2-kb cadmium-resistance plasmid of S. lugdunensis, designated pLUG10, were similar to those of pOX6, a S. aureus cadmium-resistance plasmid containing the cadB gene. Southern-blot hybridisation was performed with a probe intragenic to cadB. Hybridisation was found with the cadB probe in the cadmium-resistant S. lugdunensis isolates to the 2.9-, 3.2- and 3.7-kb plasmids. These findings suggest that cadmium-resistance in some S. lugdunensis strains is due to a gene sharing homology with the cadB gene of S. aureus.     

In-vitro bacteriocin-mediated antagonism by oral streptococci against human carrier strains of staphylococci

All strains of oral streptococci tested and specially those of Streptococcus mutans, Strep. sanguis and Strep. minor produced more than one distinct bacteriocin-like substance with variable inhibitory activity on 20 indicator staphylococci. Inhibitory activity was comparatively higher on nasal strains of Staph. aureus and Staph. epidermidis than on strains of both species isolated from the mouth. Nineteen of 20 staphylococcal indicators were inhibited by 1–12 of the 12 effector streptococci. Sensitivity of nasal staphylococci to bacteriocins (frequency of positive inhibitory tests and total inhibition zone diameters) was significantly higher ( P < 0·001, χ² test and P < 0·05, t test respectively) than that of oral ones. The sensitivity of nasal over oral Staph. aureus ( P < 0·001 and P < 0·01) and of oral Staph. epidermidis over oral Staph. aureus ( P < 0·01 and P < 0·05) was also significantly higher. The evaluation of variability of inhibitory patterns of bacteriocins produced by streptococci (p-typing), of sensitivity patterns of staphylococci to bacteriocins (s-typing) and of the significantly higher sensitivity of nasal over oral staphylococci to bacteriocins from the epidemiological and ecological veiwpoints are discussed.     

Plasmid profile and antibiotic resistance in coagulase-negative staphylococci isolated from polluted water

Four different species of coagulase-negative staphylococci (CNS) were isolated from polluted waters in Fez, Morocco and found to be Staphylococcus simulans, Staph. lenticus, Staph. hyicus and Staph. xylosus . Eight isolates belonging to these four species were analysed for their plasmid content. Southern blot hybridizations were performed to define the resistance determinants of the plasmids harboured by these species. These determinants were found to be carried mainly by Class I staphylococcal plasmids (1–5 kb). A plasmid (4·3 kb) carrying a tetracycline resistance gene was present in five isolates from all identified species. Plasmids carrying a chloramphenicol resistance gene were more frequently encountered and found to be of different sizes. Plasmids carrying erythromycin, neomycin, and streptomycin resistance genes were less frequent and were the same size. The results indicate that the occurrence of multi-resistant CNS in polluted waters may constitute a reservoir for disseminating antibiotic-resistance into the community.     

Expansion of a plasmid classification system for Gram-positive bacteria and determination of the diversity of plasmids in Staphylococcus aureus strains of human, animal, and food origins

An expansion of a previously described plasmid classification was performed and used to reveal the plasmid content of a collection of 92 Staphylococcus aureus strains of different origins. rep genes of other genera were detected in Staphylococcus. S1 pulsed-field gel electrophoresis (PFGE) hybridizations were performed with 18 representative S. aureus strains, and a high number of plasmids of different sizes and organizations were detected.     

Application of Fluorescent Antibody for Detecting Capsular Substances in Staphylococcus aureus

A fluorescent antibody technique was developed for the determination of the capsular-type of strains of Staphylococcus aureus. It compared favourably with the method using serum-soft agar (Yoshida 1972). With the new technique, many populations of encapsulated and unencapsulated strains were investigated. Of 1421 fresh isolates of Staph. aureus , 54 were encapsulated and among these 54·8% and 48·1% were mono- and polyvalent, respectively. Capsular-type antigens A and B were found in 92·5% and 44·4% of strains respectively; capsular-types C and D were found relatively infrequently. In the other group, of unencapsulated strains, capsular-type antigen production was demonstrated in 125 out of 163 strains examined. Mono- and polyvalent capsular-types (A and B antigen producing strains) comprised 77·6% and 22·4%. respectively. In these capsular-types A and B were found in 54·4% and 62·4%, respectively: capsular-type antigen C and D producing strains were again infrequent. These results indicate that a majority of ordinary Staph . aureus strains produce capsular-type antigens although isolation of the encapsulated strains is infrequent.     

Distribution of plasmids in cyanobacteria of the LPP group

Abstract The distribution of plasmid DNA has been studied in 23 strains and variants of non-heterocystous filamentous cyanobacteria that are susceptible to infection by the LPP-1 cyanophage (archetype). 21 have identical plasmid profiles and contain 3 plasmids of M _rs 0.9, 10 and approx. 12 · 10⁶ respectively. In one strain, Plectonema FS180, the plasmids have been designated pMP1, pMP2, and pMP3, respectively. pMP1 shows sequence homology with pMP2 and pMP3 but not with DNA from an LPP-type cyanophage. Plectonema UTEX 598 lacks the small plasmid only, while Plectonema UTEX 1541 is distinct amongst all these strains with 3 plasmids of M _rs 3, 10, and > 30 · 10⁶, respectively. The findings support the view that the majority of these strains may be independent isolates of a single species.     

Plasmid-determined Transformation of cis-Abienol and Sclareol in Nocardia restricta JTS-162

The cis-abienol-transformable bacterium JTS-162 was identified as Nocardia restricta. This bacterium has three plasmids (pCA1, pCA2 and pCA3). Two types of cured strains were obtained by mitomicin C treatment or growth at the maximum temperature; one type had two plasmids (pCA2 and pCA3) and the other type had no plasmid. These two types of cured strains lost the ability to oxidize C-18 methyl and to split the A-ring of cis-abienol. These two types of cured strains were also devoid of the. ability to oxidize the C-18 methyl of sclareol. From these results, it was considered that C-18 methyl oxidation and A-ring splitting of these labdanes were determined by plasmid pCA1 in N. restricta JTS-162.     

Computerized evaluation procedure for comparing the electrophoretic protein patterns of bacterial strains

Among 46 isolates of Staphylococcus aureus obtained from cattle in the State of Paraíba, Brazil, four were shown to produce antimicrobial substances (AMS). The two best AMS producers carried single plasmids of about 8·0 kbp and 50 kbp, respectively, which were designated pRJ34 and pRJ35. Curing experiments and molecular analysis associated the AMS production with the presence of these plasmids in the cells. The biochemical properties exhibited by the AMS suggested that they might be bacteriocins (Bac). The bacteriocin encoded by pRJ34 showed properties identical to those of the bacteriocins encoded by other small staphylococcal Bac plasmids. However, the bacteriocin encoded by the large plasmid pRJ35 has shown some properties which distinguish it from the other bacteriocins of Staph. aureus described so far, suggesting it may be a new member of the staphylococcal bacteriocin family.     

Antimicrobial substances produced by Staphylococcus aureus strains isolated from cattle in Brazil

Among 46 isolates of Staphylococcus aureus obtained from cattle in the State of Paraíba, Brazil, four were shown to produce antimicrobial substances (AMS). The two best AMS producers carried single plasmids of about 8·0 kbp and 50 kbp, respectively, which were designated pRJ34 and pRJ35. Curing experiments and molecular analysis associated the AMS production with the presence of these plasmids in the cells. The biochemical properties exhibited by the AMS suggested that they might be bacteriocins (Bac). The bacteriocin encoded by pRJ34 showed properties identical to those of the bacteriocins encoded by other small staphylococcal Bac plasmids. However, the bacteriocin encoded by the large plasmid pRJ35 has shown some properties which distinguish it from the other bacteriocins of Staph. aureus described so far, suggesting it may be a new member of the staphylococcal bacteriocin family.     

Molecular analyses of conjugative, gentamicin-resistance plasmids from staphylococcal clinical isolates

Gentamicin-resistant Staphylococcus aureus and Staphylococcus epidermidis strains which were isolated from infants with staphylococcal bacteremia were analyzed for the presence of self-transmissible gentamicin-resistance (Gmr) plasmids. Conjugative GMr plasmids of approximately 43.8-63 kilobases (kb) were found in all S. aureus strains. Inter- and intra-species transfer of Gmr plasmids by conjugation was observed from S. aureus to S. aureus and to S. epidermidis recipient strains. However, neither inter- nor intra-species transfer of gentamicin resistance by conjugation was observed with nine out of nine S. epidermidis donor strains which were mated with either S. epidermidis or S. aureus recipient strains. These conjugative Gmr plasmids were unable to comobilize a smaller (15-kb) plasmid present in all but two S. aureus clinical isolates. Many of the conjugative Gmr plasmids also carried genetic determinants for kanamycin, tobramycin, neomycin, and ethidium bromide resistance, and for beta-lactamase synthesis. EcoRI restriction endonuclease digests of the S. aureus Gmr conjugative plasmids revealed three different digestion patterns. Four EcoRI restriction endonuclease digestion fragments of 15, 11.4, 6.3, and 4.6 kb in size were common to all plasmids. These plasmids and conjugative Gmr staphylococcal plasmids from other geographical regions shared restriction digestion fragments of similar molecular weights. DNA hybridization with biotinylated S. aureus plasmid pIZ7814 DNA revealed a high degree of homology among these plasmids. A 50.9-kb plasmid from one of the nonconjugative S. epidermidis clinical isolates showed homology with the probe DNA but lacked a portion of a 6.3-kb fragment which was present in all conjugative plasmids and believed to carry much genetic information for conjugation.     

Serological characteristics of coagulase-positive staphylococci isolated from man and animals

A simplified method allowed Staphylococcus aureus, Staph. intermedius and coagulase-positive Staph. hyicus subsp. hyicus isolated from humans, dogs, monkey, sheep, poultry, rabbits, giant rats (Cricetomys gambianus) and other animals to be serotyped. The nine coagulase-positive staphylococcal strains of human origin possessed thermolabile and thermostable agglutinogens. Two strains of Staph. intermedius of human and canine origins examined had agglutinogen K1K2. The three Staph. aureus strains isolated from African giant rats (Cricetomys gambianus) had agglutinogens a5 and P common to them. The Staph. aureus strain isolated from a monkey belonged to serotype b1, c1, o and the caprine strain of Staph. hyicus subsp. hyicus was serotype a5, c1.     

Interactive Growth of Staphylococcus aureus Strains with a Poultry Skin Microflora in a Diffusion Apparatus

The growth of different biotypes of Staphylococcus aureus strains isolated from poultry was studied using the NBS Ecologen in which the interacting mixed culture was derived from the microfiora of hen skin and separated from the Staph. aureus culture by a membrane of 0.4 μm pore size. Inhibition of growth of the Staph. aureus cultures occurred with strains from each biotype. Marked inhibition of growth was always accompanied by the production of large numbers (>10⁹/ml) of plaque forming units (phage). In the mixed culture chamber poultry phage group C strains became the predominant Staph. aureus type. The phages produced by the mixed culture showed a wide spectrum of lytic activity for the propagating strains of the human, bovine and poultry phage sets.     

Enterotoxigenicity of Staphylococcus aureus strains isolated from poultry: raw poultry carcases as a potential food-poisoning hazard

Staphylococcus aureus strains were isolated from end-of-lay poultry carcases obtained from a plant at two different stages of processing before and after storage at different temperatures. These strains were supplemented with Staph. aureus strains isolated from poultry from a wide range of sources and biotyped, phage typed, and tested for production of enterotoxins A-E. The isolates were found to consist of poultry and human specific strains and each of these groups contained strains able to produce enterotoxin. Poultry strains produced only enterotoxin D whereas human strains produced enterotoxins A, C and D. The hen carcases used in storage experiments were found to be naturally contaminated with enterotoxin D producing staphylococci. No enterotoxin D could be detected on any of the carcases even after storage at temperatures which allowed multiplication of the organisms to occur (final Staph. aureus counts ranged from 10² to 10⁷/16 cm² of breast skin).