Staph, aureus

Staph, aureus 1613 Staph, aureus 59N Staph, aureus Ziegler... 

Polyether Staph, aureus KXQXh Sarcina antibiotic No. 6538P lutea 9341 Bacillus sp. E 27859 Bacillus suhtilis 558 Bacillus megaterium 8011 Bacillus sp. EA 27860 Mycobacterium phlei 355 Streptomyces cellulosae 3313 Eaecilomyces varioti 26820... 

The infrared spectrum of this substance showed the presence of an azido group and a 0-lactam system. The substance inhibited the growth of Staph, aureus Oxford at a concentration of 0.25 mcg/ml. 

Lysogeny is an extremely common phenomenon and it seems that most natural isolates of bacteria carry one or more prophages some strains of Staph, aureus have been shown to carry four or five different prophages. 

Different strains of a number of bacterial species can be distinguished by their sensitivity to a collection of phages. Bacteria which can be typed in this way include Stop/ , aureus and Salmonella typhi. The particular strain ol say, Staph, aureus responsible for an outbreak of infection is characterized by the pattern of its sensitivity to a standard set of phages and then possible sources of infection are examined for the presence of that same phage type of Staph, aureus. 

Early cephalosporins were spelt with ph, more recently with T. t Methicillin-resistant Staph, aureus (MRSA) strains are resistant to cephalosporins. t Enterococci are resistant to cephalosporins. 

Other pseudomonic acids (B, C, D) are also produced. Mupirocin is active predominantly against staphylococci and most streptococci, but Enterococcus faecalis and Gramnegative bacilli are resistant There is also evidence of plasmid-mediated mupirocin resistance in some chnical isolates of Staph, aureus. 

Bacteria which are almost always sensitive to the sulphonamides include Strep, pneumoniae, /3-haemolytic streptococci, Escherichia coli and Proteus mirabilis those almost always resistant include Enterococcus faecalis, Ps. aeruginosa, indole-positive Proteus and Klebsiella whereas bacteria showing a marked variation in response include Staph, aureus, gonococci, El. influenzae and hospital strains of E. coli and Pr. mirabilis. 

Microbes responsible for skin infection often arise from the normal skin flora which includes Staph, aureus. In addition Strep, pyogenes, Ps. aeruginosa and anaerobic bacteria are other recognized pathogens. Vimses also affect the skin and mucosal surfaces, either as a result of generalized infection or localized disease as in the case of herpes simplex. The latter is amenable to antiviral therapy in selected patients, although for the majority of patients, vims infections of the skin are self-limiting. 

Bacterial resistance to antibiotics has been recognized since the first drugs were introduced for clinical use. The sulphonamides were introduced in 1935 and approximately 10 years later 20% of clinical isolates of Neisseria gonorrhoeae had become resistant. Similar increases in sulphonamide resistance were found in streptococci, coliforms and other bacteria. Penicillin was first used in 1941, when less than 1 % of Staphylococcus aureus strains were resistant to its action. By 1947,3 8% of hospital strains had acquired resistance and currently over 90% of Staph, aureus isolates are resistant to penicillin. Increasing resistance to antibiotics is a consequence of selective pressure, but the actual incidence of resistance varies between different bacterial species. For example, ampicillin resistance inEscherichia coli, presumably under similar selective pressure as Staph, aureus with penicillin, has remained at a level of 30-40% for mai years with a slow rate of increase. Streptococcus pyogenes, another major pathogen, has remained susceptible to penicillin since its introduction, with no reports of resistance in the scientific literature. Equally, it is well recognized that certain bacteria are unaffected by specific antibiotics. In other words, these bacteria have always been antibiotic-resistant. 

Aminoglycosides staph, aureus (gentamicin) Conforms, pseudomonads... 

Resistance to quinolones by efflux has been described in Staph, aureus and Proteus mirabilis. This gene has been designated nor A in Staph, aureus and is homologous to membrane transport proteins coupled to the electromotive force. These proteins have the ability to remove small amounts of quinolone from cells normally and nor A may have arisen as a result of mutations under selective pressure from quinolone use, resulting in a transport protein with increased affinity for these agents. 

A gene designated msrA has been identified in Staph, aureus which confers resistance to macrolides and streptogramins but not to lincosamides. Its function is unknown but the DNA sequence is homologous to genes coding for known efflux proteins. 

Mupirocin is a topical antibiotic that inhibits isoleucyl tRNA synthetase with the subsequent inhibition of protein synthesis. Mupirocin has become a mainstay in the treatment of Staph, aureus infection and colonization during hospital outbreaks, and it is in this organism that acquired resistance has arisen (Gilbart etal. 1993). 

Acquired resistance to bacitracin has been observed in laboratory strains of Staph, aureus, but resistance has been unstable and no resistant mutants have yet been isolated in vivo. Gram-negative bacteria are intrinsically resistant to bacitracin, which inhibits the transfer of pentapeptide units to petidoglycan. 

The first official test was published by the Food, Drug and Insecticide Administration of the US Department of Agriculture, in which portions of the preparation were placed on the surface of nutrient agar inoculated with Staph, aureus. After incubation the zones of inhibition, if ary, around the preparation were measmed. This test was modified later by incorporating 10% of horse serum in the agar to simulate conditions in a woimd and a control consisting of unmedicated base was also used in each experiment. This test is known as the cup-plate test (see also section 3.6.3 and Fig. 11.5). 

Fig. 11.9 Isobologram ( - ) drawn from minimum growth inhibitory concentrations (MIC values) of chlorocresol and phenylmercuric acetate used alone and in combination against Staph, aureus, showing synergy. A, result if combination was merely additive B, result if combination was antagonistic.

Bacteria grown under different conditions may show wide response to biocides. For example, fattened cells of Staph, aureus obtained by repeated subculturing in glycerol-containing media are more resistant to benzylpenicillin and higher phenols. 

Trachypogon plumosus I O-extract, roots inhib d. E. coli, Bacillus subtilis Staph, aureus, Strep, haemolyticus 118... 

Sample staph. aureus B. subtilis Af. smegmatis C. albicans S. oerevisiae A. niger... 

Similar experiments by Lwoff showed nicotinic acid was an essential growth factor for Hemophilus bacteria and also for Staph, aureus. By the 1940s an aphorism had been coined Growth factors for microorganisms are B vitamins for higher animals. ... 

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