L forms of Staphylococcus aureus

Abstract

SUMMARYAll but four of twenty-five strains of Staphylococcus aureus exposed to concentrations of 60 pg. benzylpenicillin/ml. (or 100-500 pg. methieillin/ ml. for penicillinase-producing strains) on nutrient agar media containing 3.5 % (w/v) sodium chloride and 10 yo (v/v) horse serum, gave rise to typical L colonies. The L forms were subcultured on nutrient agar and in broth containing 3.5 % sodium chloride and were found to be corn.pletely resistant to the penicillins, cycloserine, ristocetin, vancomycin and cephalosporin, but to be sensitive to other antibiotics, often in slightly lower concentrations than the parent cocci. The L forms produced coagdase and, in two of three strains tested, were lysogenic although resistant to phage lysis. In studies of the transformation of staphylococci to L forms, it was noted that a variable but often very large proportion of the early L microcolonies failed to develop into typical colonies.

Antibiotic Inhibition and Binding Studies with a Group A Streptococcal L-Form

“…Although several antibiotics are known inhibitors of bacterial cell-wall biosynthesis, only penicillin and D-cycloserine (Krawitt & Ward, 1963) and bacitracin (Rotta, Karakawa & Krause, 1965) have been found capable of inducing 'L-phase variant' formation. The present work confirms the earlier results of others with certain group A streptococci (Ward et al 1958;Rotta et al 1965), staphylococci (Williams, 1963;Krawitt & Ward, 1963;Kagan et al 1964;Molander et al 1964) and their respective L-forms and expands upon these comparisons. The affinity for penicillin of the L-form and its parent group A streptococcus, S. pyogenes, with regard to the inability of the L-form to synthesize the rigid cell wall is discussed.…”

“…Some information is available about the sensitivity of bacteria and their derived L-forms or protoplasts to various antibiotics (Ward, Madoff & Dienes, 1958;Shockman & Lampen, 1962;Williams, 1963;Molander et al 1964;Kagan, Zolla, Busser & Liepnieks, 1964). The mode of action of such antimicrobial agents examined thus far has ranged from inhibition or disruption of a specific anatomical component (e.g.…”

Cell-Wall Deficiencies in L-forms of Staphylococcus aureus

“…Since the report of Dienes & Sharp (1956) on the isolation of various organisms in the L-phase by using a medium containing a high salt concentration, serum and penicillin, there have been several studies on the biology of the L-forms, including those of Staphylococcus aureus (Schonfeld, 1959(Schonfeld, , 1961 ; Marston, 1961 a, b; Williams, 1963). Although these reports, particularly the last, gave indirect evidence, such as osmotic fragility, phage and antibiotic insensitivity, for the lack of cell-wall material, no direct evidence was presented.…”

“…The solid and liquid media used for growth of the penicillin-induced L-forms were those described by Williams (1963). The media used for L Rogers were essentially the same except that more sodium chloride was added to give a final concentration of 4.5 % (w/v) and the penicillin was replaced by D-cycloserine (Lilly) 500 ,ug./ml.…”

“…The present paper reports some attempts to demonstrate cell-wall components in L-forms of Staphylococcus aweus. Williams (1963), were used. A fourth strain, L Rogers, isolated from a penicillinase-producing staphylococcus (phage type 42 E) by growth in the presence of D-cycloserine, was also used.…”