Attempt in classification of catalase-positive staphylococci and micrococci

Methicillin-resistant Staphylococcus aureus (MRSA) isolated from small and exotic animals at a university hospital during routine microbiological examinations

Clinical specimens of small animals (n=869) were screened for the occurrence of methicillin-sensitive and methicillin-resistant Staphylococcus aureus (MSSA; MRSA) during routine microbiological examinations, and results were confirmed by a multiplex PCR strategy. The genetic relatedness of all mecA-positive S. aureus isolates was further investigated by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), PCR for Panton-Valentine leukocidine genes (PVL) and staphylococcal cassette chromosome mec-typing (SCCmec). A total of 61 S. aureus isolates were found during a 20-month period of investigation, 27 (44.3%) of them harbouring the mecA gene for methicillin-resistance. The majority of MRSA were isolated in specimens from dogs (n=18) and cats (n=4). One guinea pig and one rabbit were found to be positive for an MRSA infected site. Similarly, three exotic animals, a turtle, a bat and a parrot, were found to be infected with MRSA. PFGE and MLST analysis revealed a certain genotype ("A" and "A-1") dominating the isolate collection (23 of 27). Furthermore, one isolate showed homologous PFGE pattern to the German epidemic strain Barnim ("BE") and another one ("BE-1") was considered to be closely related. A third genotype ("B") was detected in two cases. Two different sequence types (ST) were identified among the 27 MRSA isolates. PFGE type "A" and both strains related to the Barnim epidemic strain were assigned to ST22, whereas ST239 was associated to PFGE profile "B". The present data show that certain MRSA genotypes are capable of infecting a wide spectrum of small and exotic animals, especially in clinical facilities.

Evaluation of latex agglutination and microtube coagulase tests for detection of Staphylococcus aureus

In a blind study, a latex agglutination test (Serostat Staphylococcus, Scott Laboratories) and a microtube coagulase test (Staphase, API) were evaluated for their ability to detect Staphylococcus aureus. Of 289 isolates of catalase-positive, gram-positive cocci, 122 were identified as S. aureus based on positive reactions in at least three of the following tests: tube coagulase, slide coagulase, DNase production, or anaerobic fermentation of mannitol. The latex agglutination test gave positive reactions for all S. aureus isolates and 10 (6%) non-S. aureus isolates. The slide coagulase test was positive for 121 S. aureus isolates and three (2%) non-S. aureus isolates. The microtube coagulase test detected 53, 90, and 98% of the S. aureus isolates after 2, 4, and 24 hr, respectively. In contrast, the conventional tube coagulase test detected 97% of the S. aureus isolates after 2 hr, and 98% after 4 and 24 hr. Two isolates of S. aureus gave negative tube coagulase reactions at 37 degrees C, but positive reactions at room temperature after 24 hr. The combination of tube and slide coagulase tests provided the most reliable results. The slide and tube coagulase tests gave more reliable results than the latex agglutination and microtube coagulase tests, respectively.

Comparison of rapid identification assays for Staphylococcus aureus

A total of 137 strains of Staphylococcus species were blindly tested by four rapid serological assays, and the results were compared with those of the tube coagulase assay. For the S. aureus isolates, the Sero-STAT Staph assay gave six false-negative results, four of which were for methicillin-resistant strains. The Accu -Staph, Staphylatex , and Staphyloslide assays identified all the coagulase-positive strains as Staphylococcus aureus. Among the coagulase-negative staphylococci, false-positive results were seen with strains of S. capitis. S. saprophyticus, and S. cohnii. The overall accuracy of the kits compared with the tube coagulase test ranged from 95.1 to 100%.

Rapid distinction between micrococci and staphylococci with furazolidone agars

Furazolidone agar proved to be a suitable medium for separating strains of the genera Micrococcus and Staphylococcus. 720 isolates (including 24 type strains) of gram- and catalase-positive cocci were tested for growth on tryptone soya and peptone agar with the addition of 50 microgram/ml furazolidone. The results were compared with the classification obtained by the standard-O/F-test and by the test system of Schleifer and Kloos. For routine identification and separation of staphylococci from micrococci a peptone agar with 20 microgram furazolidone/ml is recommended.

The identification of staphylococci in clinical and food microbiology laboratories

A comprehensive review of the methods which have been utilized for the identification of staphylococci is presented. Biochemical characteristics which have assisted in the primary isolation of staphylococci, such as pigmentation, hemolytic activity, the egg yolk phenomenon, and deoxyribonuclease and coagulase production, are also analyzed. The potential applicability of advanced techniques to identify staphylococci, such as the detection of enterotoxin production, base ratio analysis, cell wall analysis, phage typing, and serology, is discussed. The following procedures are recommended for routine use: Idnetification of Staphylococcus sp. (clinical laboratories): microscopic observation, catalase activity, coagulase production, lysostaphin sensitivity, and (optional) facultative growth in thioglycolate medium. Identification of Staphylococcus aureus (food laboratories): microscopic observation, catalase activity, coagulase production, thermonuclease production, and (optional) lysostaphin sensitivity.

Reassessment of the coagulase and thermostable nuclease tests as means of identifying Staphylococcus aureus

A total of 91 enterotoxigenic strains of Staphylococcus auerus isolated from foods and tested for production of coagulase and thermostable nuclease and the ability to ferment glucose and mannitol showed, with the exception of four strains, a complete correlation among these properties. A similar correlation was observed with 103 cultures of S. aureus isolated from clinical material. In all instances, the coagulase reactions were sufficiently strong to be scored at either the 3+ or 4+ levels. Presumptive staphylococcal cultures isolated during routine examination of foods and yielding 2+ coagulase reactions or lower were invariably negative for thermostable nuclease production. It is suggested that the thermostable nuclease test be performed on cultures with doubtful coagulase reactions before classifying them as S. aureus.

Coagulase and deoxyribonuclease activities of staphylococci isolated from clinical sources

A total of 504 clinical isolates of the family Micrococcaceae were tested for coagulase, deoxyribonuclease, clumping factor, and phosphatase to determine whether there is a correlation between the results of these tests and the pathogenicity of staphylococci. In the tests for coagulase production, it was found that either human or rabbit plasma could be used with broth cultures, whereas rabbit but not human plasma was satisfactory when microorganisms removed from solid culture medium were used. Deoxyribonuclease production correlated better than the fermentation of mannitol with coagulase production. The use of methyl green, Toluidine Blue O, or acridine orange offered no advantage over the use of HCl for detecting the production of deoxyribonuclease. Neither the presence of clumping factor nor the production of phosphatase correlated well with coagulase production. Strains of staphylococci that did not produce coagulase and deoxyribonuclease were isolated as frequently as, and from a greater variety of clinical sources than, strains which produced these substances. It is concluded that the production of coagulase and deoxyribonuclease are properties of staphylococci which are not necessarily indicative of potential pathogenicity of the organisms for man.

Coagulase-negative strains of Staphylococcus pyogenes

The isolation of two coagulase-negative strains of Staphylococcus pyogenes is reported, and their biochemical characteristics are given. The reliability of coagulase tests alone in the identification of Staph. pyogenes is discussed, and the deoxyribonuclease test is recommended as a useful confirmatory test.

Enterotoxigenicity of Staphylococcus aureus cultures isolated from acute cases of bovine mastitis

To determine whether staphylococci causing bovine mastitis are potential causes of human intoxications, 142 cultures identified as etiological agents of acute cases and 18 cultures causing chronic cases of staphylococcal mastitis were obtained from investigators in the United States and Canada, examined microscopically, and tested for carbohydrate utilization, terminal pH, catalase, coagulase, egg yolk hydrolysis, gelatin hydrolysis, cytochrome oxidase, urease production, nitrate reduction, micrococcal nuclease, phage type, and enterotoxin production. Three cultures were not confirmed as Staphylococcus aureus. Of the 157 S. aureus cultures, 23 produced staphylococcal enterotoxins. Although a direct relationship between staphylococcal mastitis and outbreaks of staphylococcal food poisoning was not proved, results indicated that staphylococcal infections of the bovine mammary gland represent a significant reservoir of enterotoxigenic strains of S. aureus.

Enumeration of Bacillus cereus in foods

For the enumeration of vegetative cells and spores of Bacillus cereus in foods, a mannitol-egg yolk-phenol red-agar has been developed which exploits the failure of B. cereus to dissimilate mannitol, and the ability of most strains to produce phospholipase C. When a high degree of selectivity was required, polymyxin B sulfate in a concentration of 10 ppm appeared to be the most effective selective additive. Useful characteristics for the identification of presumptive isolates of B. cereus were found to be: morphology, dissimilation of glucose mostly to acetyl methyl carbinol under anaerobic conditions, hydrolysis of starch and gelatin, reduction of nitrate, and growth on 0.25% chloral hydrate agar.

Deoxyribonucleic acid base composition of some members of the Micrococcaceae

Auletta, Angela E. (Catholic University, Washington, D.C.), and E. R. Kennedy. Deoxyribonucleic acid base composition of some members of the Micrococcaceae. J. Bacteriol. 92:28-34. 1966.-Thirty-seven strains from the genera Micrococcus, Staphylococcus, Gaffkya, and Sarcina were examined for deoxyribonucleic acid base composition and biochemical activity. Organisms were tested for production of catalase, coagulase, deoxyribonuclease, oxidase, phosphatase, hydrogen sulfide, indole, and acetoin; nitrate reduction; gelatin, starch, and urea hydrolysis; citrate and ammonium phosphate utilization; NaCl tolerance; growth at 10 and 45 C, and growth in litmus milk. They were tested for production of acid from dextrose and mannitol under anaerobic conditions, and for aerobic production of acid from dextrose, mannitol, lactose, sucrose, raffinose, maltose, xylose, and glycerol. Organisms could be divided into two groups on the basis of guanine-cytosine (GC) content. Group I had an average GC content of 32%, and included all organisms which produced acid from dextrose. Group II had an average GC content of 62%, and included those organisms incapable of producing acid from dextrose under anaerobic conditions. Sarcina ureae had a GC content of 43%.

Deoxyribonucleic acid base composition of some members of the Micrococcaceae

Auletta, Angela E. (Catholic University, Washington, D.C.), and E. R. Kennedy. Deoxyribonucleic acid base composition of some members of the Micrococcaceae. J. Bacteriol. 92:28-34. 1966.-Thirty-seven strains from the genera Micrococcus, Staphylococcus, Gaffkya, and Sarcina were examined for deoxyribonucleic acid base composition and biochemical activity. Organisms were tested for production of catalase, coagulase, deoxyribonuclease, oxidase, phosphatase, hydrogen sulfide, indole, and acetoin; nitrate reduction; gelatin, starch, and urea hydrolysis; citrate and ammonium phosphate utilization; NaCl tolerance; growth at 10 and 45 C, and growth in litmus milk. They were tested for production of acid from dextrose and mannitol under anaerobic conditions, and for aerobic production of acid from dextrose, mannitol, lactose, sucrose, raffinose, maltose, xylose, and glycerol. Organisms could be divided into two groups on the basis of guanine-cytosine (GC) content. Group I had an average GC content of 32%, and included all organisms which produced acid from dextrose. Group II had an average GC content of 62%, and included those organisms incapable of producing acid from dextrose under anaerobic conditions. Sarcina ureae had a GC content of 43%.

COMPARATIVE PHYSIOLOGY OF ANTIBIOTIC-RESISTANT STRAINS OF STAPHYLOCOCCUS AUREUS

Brown, Ruby L. (North Carolina State College, Raleigh) and James B. Evans . Comparative physiology of antibiotic-resistant strains of Staphylococcus aureus . J. Bacteriol. 85: 1409–1412. 1963.—A collection of antibiotic-resistant strains of Staphylococcus aureus isolated from clinical sources was studied with respect to nutritional requirements and common diagnostic tests. Contrary to numerous reports in the literature indicating changes in these characteristics in antibiotic-resistant mutants, the present cultures were typical members of the taxonomic species S. aureus . They were coagulase-positive, fermented both glucose and mannitol under anaerobic conditions, produced acetoin from glucose, grew and produced black colonies on tellurite glycine agar, required both thiamine and nicotinic acid, and did not require other vitamins or purines. It is suggested that in most instances these cultures from clinical sources represent spontaneous mutants having genetic changes limited largely to loci concerned with antibiotic resistance. Most reports of extensive changes in physiology and nutritive requirements by antibiotic-resistant strains of S. aureus are based on studies of resistant strains selected after exposing a large population of the parent sensitive strain to toxic levels of antibiotics, chemical mutagens, or irradiation. Such isolates may have widespread genetic damage at other loci in addition to those concerned with their antibiotic resistance.