Frequency of isolation of enterotoxigenic staphylococci from milk of nursing mothers in Kaduna, Nigeria.

Milk samples from 251 nursing mothers were screened for enterotoxigenic staphylococci. The incidence of staphylococci in milk samples was 71.3%. Two hundred and sixteen strains were isolated from 179 mothers. Eighty-six (39.8%) of the 216 strains were found to be toxigenic. Enterotoxin type A (SEA) predominated, with 41 strains (19.0%) elaborating it. Twenty-one strains (9.7%) produced enterotoxin B (SEB) while only eight (3.7%) produced enterotoxin C (SEC). Ten strains (4.6%) produced all three types. Enterotoxigenic strains usually produced coagulase, thermonuclease and alpha haemolysin. In this series breast-feeding alone was more common than combined breast and bottle feeding, especially among mothers less than 30 years old. The incidence of reported infantile diarrhoea decreased with increasing age of the mother. Of 16 babies with diarrhoea, 10 (62.5%) had mothers whose milk yielded staphylococci. Six of these were toxigenic. Although no direct relationship between enterotoxigenic staphylococci in the milk of nursing mothers and infantile diarrhoea could be demonstrated, these findings reveal a potential health risk to these infants.

Reliability of thermonuclease production for the identification of human and animal Staphylococcus aureus.

A total of 314 clinical and non-clinical isolates of the genus Staphylococcus was tested for coagulase production and glucose and mannitol fermentation. The isolates were tested for thermonuclease production and agglutination by sera 17H and 61218, which were specific for human and canine S. aureus biotypes, respectively. All produced coagulase and fermented glucose. A majority fermented mannitol anaerobically except for the canine isolates. A majority of human isolates produced thermonuclease (64.3%) and most were agglutinated by serum 17H. There was good correlation between thermonuclease production and agglutination by serum 17H of human and bovine clinical isolates (86.6 and 80%, respectively). This was also true of clinical canine isolates agglutinated by serum 61218, of which 75% were thermonuclease-positive. Over half of canine isolates (52.8%) were thermonuclease-positive and most were agglutinated by serum 61218. Bovine and caprine isolates were 34.1 and 25% thermonuclease-positive, respectively, while ovine isolates were only 14.2% thermonuclease-positive. Isolates from these ruminant sources were also poorly agglutinated by either serum. It was concluded that a greater number of clinical human and canine biotypes of S. aureus produced thermonuclease than their non-clinical isolates, and that a majority of other animal isolates were negative for thermonuclease. Therefore, the thermonuclease test may not be very useful for confirming the animal origin of S. aureus isolates.

Studies on possible cross transmission of mercuric chloride resistant Staphylococcus aureus between dogs and kennel attendants.

Ten S. aureus strains were each introduced into the nostrils of each of 10 dogs. The dogs retained the strains of S. aureus for the period of the experiment (eight weeks). Five of them with human strains of s. aureus, and the two control dogs acquired strains of canine origin during the period, but no human strain was detected in the nostrils of those into which canine strains were introduced. One of the dogs (dog 4) died during the period of the experiment and both human and canine S. aureus were isolated from its nostrils after the animal had been frozen for about 18 hours. One attendant acquired both canine and human S. aureus during the course of the experiment while one attendant working in the veterinary clinic but had no direct contact with the experimental dogs acquired human S. aureus during the third week of the experiment. It was concluded that contaminated environment jointly being shared by man and animals is the common source of cross contamination by the various biotypes of S. aureus.

Studies on possible cross transmission of mercuric chloride resistant Staphylococcus aureus between dogs and kennel attendants.

Ten S. aureus strains were each introduced into the nostrils of each of 10 dogs. The dogs retained the strains of S. aureus for the period of the experiment (eight weeks). Five of them with human strain of S. aureus, and the two control dogs acquired S. aureus of canine origin during the period, but no human strain was detected in the nostrils of those into which canine strains were introduced. One of the dogs (dog 4) died during the period of the experiment and both human and canine S. aureus were isolated from its nostrils after the animal had been frozen for about 18 hours. One attendant acquired both canine and human S. aureus during the course of the experiment while one attendant working in he veterinary clinic but had no direct contact with the experimental dogs acquired human S. aureus during the third week of the experiment. It was concluded that contaminated environment jointly being shared by man and animals is the common source of cross contamination by the various biotypes of S. aureus.

Experimental study of the effects on rabbits of strains of Staphylococcus aureus which are resistant to mercuric chloride.

3 mercuric chloride resistant strains of Staphylococcus aureus of human, canine and bovine origin were inoculated into rabbits which were then caged with clinically healthy rabbits. All rabbits were observed twice daily for evidence of infection. The human strain of S. aureus produced the severest lesion and the bovine strain the least severe lesion. Only 1 of 16 healthy rabbits developed a lesion similar to those of the infected rabbits in its group and from which identical S. aureus was isolated. It was concluded that the human biotype was more virulent in rabbits than the canine and bovine biotypes, and that infection in a rabbit colony by mercuric chloride resistant members of the 3 biotypes may not cause epidemic staphylococcosis.

Effect of biotin deficiency on some properties of Staphylococcus aureus isolates from humans and other animals.

Staphylococcus aureus isolates from humans and other animals were grown in biotin assay medium containing 12 mug of biotin per liter and compared to isolates from the same sources grown concurrently in medium containing adequate biotin. The two cultures were tested for production of coagulase, phosphatase, and fibrinolysin enzymes and for responses to various antimicrobial agents and bacteriophages. Organisms grown in biotin-deficient medium produced less phosphatase; coagulase and fibrinolytic activity was reduced, and they were more susceptible to antimicrobial agents than were normal organisms, but phage susceptibility was not greatly affected.