Colin M. MacLeod

A “Sulfapyridine-Fast” Strain of Pneumococcus Type I

Summary A strain of pneumococcus Type I has been made “sulfapyridine-fast” by repeated transfers in broth containing increasing concentrations of sulfapyridine. “Sulfapyridine-fastness” is demonstrable both in vitro and in vivo. The alteration is not associated with changes in morphology, virulence, or specific immunological characteristics.

Metabolism of “Sulfapyridine-Fast” and Parent Strains of Pneumococcus Type I

Summary The acquisition of “sulfapyridine-fastness” by a strain of pneumococcus Type I is associated with a marked diminution in the production of hydrogen peroxide in cultures of this strain. Cell suspensions of the parent and drug-fast strains dehydrogenate glucose equally well. On the other hand, the acquisition of sulfapyridine-fastness is associated with a marked loss of dehydrogenaseactivity for certain 3-carbon compounds (glycerol, lactate, and pyruvate). When sulfapyridine is added directly to the reacting system the dehydrogenase-activity of the parent cells for the same 3-carbon compounds is likewise much decreased.

Toxicity for Dogs of a Bactericidal Substance Derived from a Soil Bacillus

Summary A study has been made of the toxicity for dogs of a protein-free preparation of the bactericidal substance described by Dubos when injected by the intravenous route. Seven of the 8 animals which received 0.4 mg/kg or more daily died as a result of the injections, and in 6 of these death occurred before the course of 10 daily injections was completed. All animals receiving 0.3 mg/kg or more snowed well-marked acute or chronic changes in the liver, spleen, kidneys, heart and lungs. Animals which received daily 0.2 mg/kg or less for 10 days showed only minor evidence of toxicity.

Hypoaminoacidemia in Patients with Pneumococcal Pneumonia

Summary Observations on the plasma amino acid nitrogen of 6 patients with pneumococcal pneumonia are presented. In each instance luring the acute phase of the disease the patient showed a plasma amino acid concentration significantly below the average normal value. During convalescence there was a gradual rise in the concentration of plasma amino acid nitrogen, with a return to a normal level on complete recovery from the disease. Present data indicate the normal average value to be 4.50 mg per 100 cc.

Bacteriological Diagnosis of Pneumonia in Relation to Chemotherapy

THE introduction of various sulfonamide compounds has contributed greatly to the therapy of pneumonia. Important as this contribution is, it leaves unanswered the fundamental question-that of prevention. The development of therapeutic measures serves to emphasize the fact that the prophylaxis of pneumonia still remains an unsolved problem. Cole has pointed out that lobar pneumonia is not a single disease but rather

Relation of the Carrier State to Pneumococcal Peritonitis in Young Children with the Nephrotie Syndrome

Summary In 6 young children with the nephrotic syndrome who developed pneumocoecal peritonitis, the type of pneumococcus recovered from the nasopharynx was the same as that causing peritonitis. Evidence is presented which indicates that peritonitis may be caused by a strain of pneumococcus of the same specific type as that of the organism known to have been carried in the nasopharynx for a considerable time before the development of the infection; this carrier-state may persist for a prolonged period after recovery from peritonitis.

Effect of a Heat-Resistant Enzyme Upon the Antigenicity of Pneumococci

Rabbits immunized by the intr a cutaneous injection of heat-killed encapsulated pneumococci fail to develop the type-specific carbohydrate antibodies which result from the intravenous injection of the same antigen. 1 An attempt was made to follow the fate of pneumococci injected into the skin, in the hope of determining the cause of this lack of type-specific antigenic response. Heat-killed cells of pneumococcus Type I were injected at several sites into the skin of a rabbit. The injected areas were excised at different intervals of time and films made from the tissue fragments were stained by the Gram technic. There was, of course, a pronounced polymorphonuclear infiltration at the site of injection. The pneumococci were seen to undergo a process of extracellular digestion which began within 24 hours after injection and was completed in 4 to 5 days; many bacteria became Gram negative before being engulfed by the leucocytes. These observations suggested that leucocytes produce ferments capable of attacking heat-killed pneumococci. To demonstrate the existence of these enzymes, a polymorphonuclear exudate was obtained by injecting aleuronate into the pleural cavity of a rabbit. The washed cells extracted with N/10 HQ yielded a soluble principle which has the property of rendering pneumococci Gram negative. Active extracts, with similar properties, were obtained from the organs—especially the liver, pancreas, spleen, and lungs—of several animal species. The same enzyme was also prepared from the pleural exudate from a tuberculous patient, who developed empyema following secondary infection with H. influenza. The active enzyme present in these extracts is heat-resistant, especially at slightly acid reactions. Its rate of activity upon pneumococci increases with temperature up to 75°C.; the range of pH activity lies between pH 5.5 and pH 9.5. The enzyme appears to be a protein which is rapidly destroyed by pepsin but is completely resistant to trypsin and chymotrypsin.