Classification and biological characteristics of coagulase-positive Staphylococci isolated from animals

A total of 165 coagulase-positive staphylococcal strains of different origin (142 S. aureus strains and 23 S. intermedius strains) were subjected to biological typing in accordance with the schemes of Hajek-Marsalek and Meyer-Witte. The former of these schemes permitted to identify 68% and the latter 18% of S. aureus strains. The cultures isolated from swine and chickens had the most uniform composition: 85-86% of the strains belonged to biotype B. 44% of the strains isolated from cows and sheep belonged to biotypes C (ecovars bovis and ovis) and A (ecovar hominis); the rest of the strains could not be identified. 96% of the strains isolated from minks were made up of S. intermedius, more than a half of them belonging to biotype E (ecovar canis). In 80% of S. aureus strains and 48% S. intermedius cultures protein A was detected. Only 9% of S. aureus strains of animal origin were found capable of producing enterotoxins (A-D). The expediency of working out a unified scheme for the biotyping of coagulase-positive staphylococci is discussed.     

Isolation of strains of a new ecological variant of Staphylococcus aureus from asses

47 coagulase-positive staphylococcal strains were isolated from the nasal smears of 175 healthy donkeys. In accordance with the schemes of Akatov--Devriese and Mayer-Witte--Akatov, 10.6% of the cultures were classified with the coagulase-positive species S. hyicus and 89.3%, with the species S. aureus. Out of S. aureus strains, 11.9% were found to have the characteristics of ecovar hominis, while 16.2% of the cultures could not be classified with definite ecovars. Most of the strains (71.4%) were found to differ from the known ecovars of S. aureus in their biological properties. For this reason, the above strains were classified with the new ecovar asinae. The authors propose to make the existing S. aureus identification scheme (the scheme of Mayer-Witte--Akatov) more complete by adding the tests for hyaluronidase and phosphatase.     

Antiseptic resistance of clinical strains of Staphylococcus aureus

To evaluate the activity of antiseptics and the sensitivity-resistance of bacteria to antiseptics, a number of characteristics has been used, including the minimum inhibiting concentration for different strains, the frequency of statistical and clinical resistance, the antiseptic activity index. A wide spread of S. aureus strains isolated from patients with hospital infections has been revealed. Differences in the resistance of bacterial strains have been established, depending on the type of the antiseptic and the ecovar of bacteria: among hospital ecovars, resistant strains occur more frequently and can resist a wider range of antibiotics. In staphylococcal hospital ecovars the occurrence and level of resistance to a number of widely used antiseptics increase with time. In connection with a wide spread of staphylococcal hospital strains resistant to antiseptics, measures on the control of the circulation of such strains should be introduced into hospitals, and the data thus obtained should be used for the periodic reevaluation of antiseptics used in medical practice and for the choice of preparations to be used for individual therapeutic and prophylactic antisepsis.     

Phage typing of the coagulase-positive staphylococci isolated from various species of animals

More than 200 coagulase-positive strains of animal origin have been studied by means of Staphylococcus aureus typing phages, belonging to two international sets and intended for typing staphylococci isolated from large cattle and humans, and experimental "chicken" phage A 1591. Among S. aureus strains the cultures isolated from swine, cows, chickens, and belonging to biotypes B1, C1, B2, respectively, have been mostly (in 78.5-90.0% of cases) determined by phage typing. The strains belonging to one biotype have proved to be sensitive predominantly to the same phages. In this connection further differentiation of staphylococci within individual biotypes by means of the phages used in these experiments seems to be impracticable. S. intermedius strains have been found to be completely resistant to the above phages, which confirms that S. intermedius is rightly considered to be an independent species of coagulase-positive staphylococci.     

Species characteristics of coagulase-negative staphylococci of animal origin

The specific identification of 271 strains of coagulase-negative staphylococci isolated from different animals (cows, sheep, swine, hens, monkeys, minks, sables, foxes, etc.) was carried out according to the scheme of Akatov--Devriese. Species could be determined in 77.5% of the strains. The representatives of S. sciuri (55.5%) and S. xylosus (11.4%), very seldom occurring in humans, prevailed among the identified cultures. In 31.4% of coagulase-negative strains of animal origin the presence of protein A was established. The study of the time of glucose fermentation in the cultures and the type of colonies formed on agar with crystalline violet permitted the additional characterization of the majority of the strains of coagulase-negative staphylococci. Only in 4.8% of cases the strains under study could be lyzed by typing phages Holmberg and belonged to 6 phage types; of these, 117 A was the most numerous one (7 out of 13 typed cultures). No relationship between the phage type and the species of the strains was established.     

Sensitivity to vancomycin and teicoplanin of coagulase-negative staphylococci isolated from clinical specimens

The frequency of resistance and elevated resistance to teicoplanin and vancomycin among 689 strains of coagulase-negative staphylococci isolated in one year from clinical specimens was determined. Using ATB.STAPH test, a resistance was shown mainly among strains of S. epidermidis and S. haemolyticus. The elevated resistance to teicoplanin was much more frequently observed than to vancomycin. About 27% of isolated strains of S. haemolyticus and 6.8% of S. epidermidis were classified as resistant. Among other species only single strains were recognised as resistant: one strain of S. xylosus, one of S. cohni and one of S. intermedius. 94.7% of S. epidermidis and 100% of S. haemolyticus strains classified as resistant to teicoplanin in ATB showed MIC values 14 mg/l. Moreover it was shown that 26.3% of these strains of S. epidermidis and 33.3% of S. haemolyticus had MBC of teicoplanin values equal to or higher than 32 mg/l.     

Frequency of the isolation of staphylococci from domestic animals and strain identification

Staphylococci occur in donkeys more frequently than in other animals, and only from donkeys coagulase-negative staphylococci, characteristic of humans (S. hominis, S. capitis, S. cohnii), were isolated. Least frequently staphylococcal carrier state was registered in cats; in these animals only coagulase-negative strains were found to occur. From 30 donkeys coagulase-positive staphylococci belonging to 47 S. aureus strains were isolated. These strains differed from known ecological variants in their biological properties, thus suggesting the existence of S. aureus ecovar specific for donkeys. These strains did not coagulate human, bovine and ovine plasma, but coagulated rabbit plasma in 100% of cases and donkey plasma only in 53% of cases; at the same time they relatively often produced delta hemolysin, rarely phosphatase and hyaluronidase and never fibrinolysin. These strains were typed by KPC phages, mainly 116 and 117.     

Resistance of different strains of pathogenic staphylococcus to unfavorable environmental factors]

A study was made of the resistance to drying the UV-irradiation, the action of furacillin and chloramine displayed by 60 stains of S. aureus differing by origin (hospital and extrahospital), by the source of discharge (the upper respiratory tracts of carriers and the discharge of the purulent-inflammatory foci of surgical patients), relation to the antibiotics (polyresistant and sensitive) and phage-group reference. It was found that the resistance of staphylococci to the unfavourable factors was not always associated with the listed signs of the strains. In respect to drying a marked resistance was expressed by the hospital strains in comparison with the extrahospital ones, polyresistant in comparison with the sensitive ones, staphylococci of III and I+III phage groups in comparison with the strains of other bacteriophage groups. Strains of the III phage group proved to be the most resistant to the UV-irradiation. Strains isolated from carriers were more resistant to furacillin than staphylococci isolated from the purulent-inflammatory foci. Strains of the III phage group and nontyping had analogous advantages over the cultures of other phage groups.     

Coagulase-Negative,Novobiocin-Resistant Staphylococci on the Skin of Animals and Man,on Meat and in Milk

The occurrence of coagulase-negative, novobiocin-resistant staphylococci, i.e. Staphylococcus cohnii, Staphylococcus saprophyticus, Staphylococcus sciuri and Staphylococcus xylosus, on the skin of animals and man has been studied. On cultures from cats, cows, dogs, guinea pigs, mice, rabbits and sheep studied, such organisms were predominant among the coagulase-negative staphylococci. From the skin of the hands of 21 of 38 persons whose professions brought them into contact with animals, e.g. inséminât ors, slaughterhouse workers and veterinarians, coagulase-negative, novobiocin-resistant staphylococci were isolated. This finding contrasted with that regarding 50 persons lacking such contacts, of whom only 1 harboured such bacteria. S. saprophyticus was isolated only from those slaughterers presenting with wounds on their hands. Coagulase-negative, novobiocin-resistant staphylococci were also isolated from every second specimen collected from the surface of meat at a slaughterhouse. No difference in the culture results could be demonstrated from specimens collected before and after cutting-up of the carcasses. Of 26 strains of coagulase-negative, DNase-negative staphylococci isolated from milk with pathological CMT, all but 5 were novobiocin-resistant. Fifteen were classified as S. xylosus, 4 as S. sciuri and 1 as S. cohnii. Of another 15 DNase-positive strains, 3 were resistant to novobiocin. Finally, clinical infections with coagulase-negative, novobiocin-resistant staphylococci in man, e.g. urinary tract infections caused by S. saprophyticus, are considered in relation to possible contagious reservoirs and modes of spread.     

Interspecies lysogenization in staphylococci: transfer of bacteriophage converting enterotoxin A from a clinical strain of Staphylococcus aureus to Staphylococcus intermedius

The ability of lysogenization was examined of 50 S. intermedius strains and of 77 strains belonging to 14 different species of coagulase-negative staphylococci using 8 enterotoxin A converting bacteriophages isolated from S. aureus. All the examined bacteriophages showed lytic activity against at least 1 of 11 susceptible strains of S. intermedius to them. Lytic activity towards coagulase-negative staphylococci was observed for 6 of 8 examined bacteriophages. Two bacteriophages were active against 1 of 9 examined S. capitis strains, one against 1 of 11 examined S. haemolyticus strains, four against 1 of 6 examined S. lugdunensis strains, three against 1 of 6 examined S. warneri strains and one against 1 of 5 examined S. xylosus strains. Lysogenization with bacteriophage f421-1 able to convert positively enterotoxin A and staphylokinase and negatively beta-haemolysin of one S. intermedius strain was successful. S. intermedius lysogenized with phi 421-1 was able to produce both enterotoxin A and staphylokinase and lost ability to produce beta-haemolysin. Our results showed a broad lytic spectrum and interspecies host range of some S. aureus bacteriophages and the ability of interspecies transfer of bacteriophages between S. aureus and S. intermedius.     

Antiseptic sensitivity of clinical strains of Pseudomonas aeruginosa

MICs, the frequency of clinical and statistic resistance and the antiseptic activity index were studied in complex on out-of-hospital and hospital ecovars of P. aeruginosa. The forms resistant to a number of antiseptics, i.e. chloramine B, chlorhexidine, decamethoxine and dioxidine whose frequency eventually increased were shown to be widely distributed. The antiseptic sensitivity spectrum was more narrow and more heterogeneous than that of other bacteria, the heterogeneity level being dependent on the antiseptic type and bacterial ecovar. The activity of pervomur, phenol, resorcin and boric acid was higher against the clinical strains of P. aeruginosa while iodopyrin, sulfacetamide sodium and dioxidine were less active. The P. aeruginosa strains had natural resistance to cetylpyridinium chloride, rokkal, ethonium, sodium laurate and laurylsulfate and rivanol. It was recommended to assay antiseptic sensitivity of agents causing purulent inflammatory infections and to control circulation of antiseptic resistant variants of bacteria in hospitals.     

Bacterial resistance to disinfectants containing quaternary ammonium compounds

Quaternary ammonium compounds (QAC) are widely used as disinfectants in both medical and food environments. Microbial contaminants are, therefore, regularly exposed to their action and the isolation from clinical and food sources of resistant bacteria continues to be reported in many countries. Resistance to QAC in clinical strains of staphylococci is encoded by one of at least three resistance genes, designated qacA, qacB and qacC. Using hybridisation analysis, we have shown that these QAC resistance genes are also distributed among staphylococcal strains in the food industry. In addition, we have discovered two new resistance determinants in these food isolates, which are now being characterised and sequenced. Although the general level of resistance of pure cultures is low, the resistant strains have originally been isolated after exposure to the recommended user concentration of a commercial brand of QAC.We have also studied resistance to QAC in pseudomonads isolated from the food industry. Their level of resistance is much higher than that found in staphylococci. About 30% of the collected strains were able to grow in 200 μg·ml⁻¹ benzalkonium chloride, the lowest recommended use concentration for this commonly used type of QAC.     

Antagonistic action of Pseudomonas aeruginosa against Staphylococci, coliform bacilli and various types of Proteus

Antagonistic activity of 2 fresh isolates and 3 collection strains of Pseudomonas aeruginosa against 177 microbial strains was determined with the method of late antagonism. Among the microbial strains there were 56 staphylococcal strains isolated from patents and carriers. 38 nontypable colon bacilli isolated from healthy persons, 59 enteropathogenic colon bacilli of various serogroups, 12 strains of Proteus and 12 colon bacilli, carriers of multiple drug resistance factors (R factors). All the cultures were sensitive to the antagonistic action of 5 or at least 3 strains of Pseudomonas used in the study. The most active antagonists were the fresh isolates of Pseudomonas as compared to the collection strains. Among the staphylococci S. aureus proved to be the most resistant to the antagonistic action of Pseudomonas as compared to S. epidermidis, the same as the strains isolated from carriers as compared to the strains isolated from patients. As for the enteric bacilli the most resistant were the strains of Proteus. Acquiring of transmissive R factors by the colon bacilli markedly increased their sensitivity to the antagonistic action of Pseudomonas.     

Characteristics of staphylococci isolated from man, poultry and some other animals

Of 281 strains of staphylococci isolated from man and animals 36 (12.8%) were coagulase-positive and 245 (87.2%) were coagulase-negative. Staphylococcus aureus and Staph. intermedius were the commonest coagulase-positive staphylococci isolated from the hosts examined. Of the 20 strains that remained unclassifiable, 14 were isolated from sheep and goats.     

Staphylococcus schleiferi subsp. coagulans subsp. nov., isolated from the external auditory meatus of dogs with external ear otitis

A new subspecies, Staphylococcus schleiferi subsp. coagulans, was isolated from the external auditory meatus of dogs suffering from external ear otitis and is described on the basis of studies of 21 strains. Phenotypic studies showed that these strains are more closely related to Staphylococcus intermedius than to other staphylococci, but DNA hybridization studies indicated that they are closely related to Staphylococcus schleiferi N850274T. On the basis of biochemical distinctiveness (positive test tube coagulase test and different carbohydrate reactions) and the etiological importance (frequent isolation from otitis specimens from dogs) of these strains, we propose to classify them as a subspecies of S. schleiferi. The strains of this new subspecies are coagulase tube test, beta-hemolysin, and heat-stable nuclease positive but clumping factor negative. A simple scheme for the differentiation of S. schleiferi subsp. coagulans from the other coagulase-positive staphylococci is presented. The type strain is GA211 (= JCM 7470).     

Susceptibility to antimicrobial agents of bacteria isolated from pregnant, postpartum women, and newborns from zones with high irradiation risk]

Susceptibility of 350 strains of staphylococci, isolated from pregnant women, puerperal and newborns and of 170 strains, isolated from obstetrical hospital environment at the region with high risk of radiation after accident was determined. The tested bacterial strains were the following: 56--Staphylococcus aureus, 152--S. epidermidis, 142--S. saprophyticus, isolated from women and newborns; strains isolated from hospital environment included 120 strains of S. saprophyticus and 50 strains E. coli. The tested antimicrobial factors were the following: 22 antibiotics, 2 bioantibiotics of the breast milk and blood (lysozyme, betalysin) not separated from the substrate and tested on test-cultures of M. luteus and B. subtilis, and 5 desinfectants. Analysis was performed by common disk-diffusion method and by contact method elaborated before. High resistance of staphylococci to many antibiotics, bioantibiotics and disinfectants was demonstrated. The resistance is considered to be due to high radiation background because it is much higher than resistance frequency of the similar strains isolated at the safe areas. The resistance to antimicrobial factors was higher among the opportunistic and saprophyte staphylococci along with appearance of pathogenic factors and activation of persistence properties.     

Antibiotic sensitivity of staphylococci isolated from the surface of the skin of the breasts in pregnant women

Nine hundred and fourty coagulase-positive and coagulase-negative strains of staphylococci isolated from the skin surface of the mammary glands of 94 pregnant women were tested by the disc agar diffusion method for their sensitivity to five antibiotics. The highest number of the isolates were sensitive to erythromycin and lincomycin (87.7 and 89.7 per cent, respectively). The highest number of moderately resistant strains were detected with respect to methicillin. 19 out of 42 cultures of Staph. aureus were resistant to benzylpenicillin and 24 cultures were resistant to tetracycline. Among staphylococci 130 strains or 13.8 per cent were polyresistant.     

In vitro susceptibility of staphylococci to linezolid and other antimicrobial agents

Linezolid is a member of the new class of antibacterial agents called oxazolidinones that are active against Gram positive organisms and exert their action by protein synthesis inhibition. In this study we investigated the in vitro activity of linezolid versus the other agent against clinical strains of staphylococci: Staphylococcus aureus (n = 82) and S. epidermidis (n = 32) collected in 2002 from hospitalized patients and healthy individuals, isolated from different biological samples. Agar dilution minimum inhibitory concentrations (MICs) were determined by using Mueller-Hinton agar according to the guidelines established by the National Committee for Clinical Laboratory Standards. Linezolid demonstrated excellent in vitro activity against all isolates tested, with MICs values in the range of susceptibility (< or = 8 microg/ml). No associated resistance between linezolid and other agents tested was observed. The resistance among Gram positive bacteria continues to spread and for many patients infected with these resistant organisms antimicrobial therapy is ineffective and linezolid may be a new alternative treatment.     

Characteristics of staphylococci isolated from man, poultry and some other animals

Of 281 strains of staphylococci isolated from man and animals 36 (12–8%) were coagulase-positive and 245 (87–2%) were coagulase-negative. Staphylococcus aureus and Staph. intermedius were the commonest coagulase-positive staphylococci isolated from the hosts examined. Of the 20 strains that remained unclassifiable, 14 were isolated from sheep and goats.     

Staphylococci in orthopaedic surgical wounds.

From 50 infected surgical wounds of orthopaedic patients, 43 (86%) staphylococcal strains were isolated. 34 of all these staphylococci belonged to Staphylococcus aureus species (i.e. 68 % of all isolates from surgical wounds; 79% of staphylococcal isolates); 9 were coagulase-negative staphylococci (i.e. 21% of all isolates from surgical wounds; 18% of staphylococcal isolates). Among microorganisms isolated from the wounds we also found 2 (4%) of the Enterobacteriaceae family; 2 (4%) of the Pseudomonas genus; 3 (6%) of the Streptococcus genus. Thus, orthopaedic surgical wounds were infected by staphylococci (mainly S. aureus) more frequently than by other micro-organisms. All the staphylococcal strains were screened for methicillin resistance by agar disk diffusion testing and for the presence of mecA gene responsible for methicillin resistance by PCR. 32% of the S. aureus and 33% of the S. epidermidis strains resulted methicillin resistant and mecA-positive. The data confirm the diffusion of methicillin resistant S. aureus in surgical site infections and shows that the so-called "new pathogens", i.e. S. epidermidis and other coagulase-negative staphylococci, also exhibit a frequent and hazardous methicillin-resisting ability.