The results of serotyping of 10 953 salmonella isolates from humans over a 10-year period, 1973-82 at the Bacteriology Division, Institute for Medical Research, Malaysia are presented. A total of 104 serotypes from 22 'O' groups were encountered; 95 isolates were considered untypable. The three most predominant serotypes, namely Salmonella typhi, S. typhimurium and S. weltevreden together accounted for 54.1% of all isolates whilst the 25 most frequent serotypes accounted for 93.6% of the total. Whilst the commoner serotypes occurred regularly throughout the study period, the rarer ones tended to appear only in one year, when they might be associated with an outbreak, and never again. The pattern of serotypes, though quite similar to the one seen in neighbouring Singapore, is different from those experienced in other places such as Hong Kong, Jakarta, Bangladesh and Manchester.
During the period 1971-1982, 57 salmonella strains other than S. typhi and S. paratyphi were isolated from sites other than stools and blood. Cerebrospinal fluid was the commonest specimen followed by urine and pus. The commonest serotypes of the 22 encountered were S. typhimurium and S. enteritidis. Twenty-four of the 57 patients were children under one year of age. These findings highlight the need to remember the unusual manifestation of salmonellosis in differential diagnoses.
The pattern of phage types of 2553 strains of Salmonella typhi isolated over the 10-year period 1970-9 was studied. During the period 29 different phage types were encountered, not including the categories of 'untypable strains', 'degraded Vi-strains' and Vi negative strains. For the period as a whole, the commonest phage types encountered were A (20.9%), E1 (14.8%), D1 (10.3%), degraded Vi positive strains (10.3%), untypable Vi strains (7.3%), C4 (7.1%), D2 (4.4%), E2 (3.9%) and type 25 (2.6%). There were phage types which appeared in the early years of the period and then disappeared (types B2, D9 and D1-N). Others only made their appearance in recent years (K1 and 53). Notable differences were also seen in the predilection of some phage types for certain geographical areas.
The efficacy of Cary Blair medium was compared with that of Selenite 'F'in the isolation of enteropathogens from 805 cases of diarrhoea. It was shown that use of the Cary Blair medium resulted in a significantly higher rate of isolation. Not only were organisms found which were not isolated from the Selenite 'F' but there was a much higher isolation rate of Salmonella from Cary Blair medium althougn Selenite 'F' is generally considered as an enrichment medium for
Salmonella. The findings indicate that it would be advantageous to introduce Cary Blair medium as the sole transport medium for the isolation of enteropathogensfrom cases ofdiarrhoea.
Vibrio parahaemolyticus was isolated from 47 of 2,699 stools examined primarily for the exclusion of cholera. All strains grew well in alkaline peptone water containing 0.5% NaCl and in Monsur's medium. Serotyping showed them to be of various types. Adults were mainly affected. The importance of looking for V. parahaemolyticus in clinical specimens from cases of diarrhea is emphasized.
During the period 1979-1982, 70 strains of atypical mycobacteria isolated from clinical material were identified as belonging to species or species complex. Twenty-eight out of 61 strains isolated from pulmonary specimens were identified as M. avium-intracellulare. This frequency of association of M. avium-intracellulare with sputa of patients with pulmonary symptoms points to its potential importance and the need for further investigation.
Enterobacteriaceae isolated from clinical sources were examined for antibiotic resistance and the ability to transfer resistance to Escherichia coli. Twenty-nine out of 80 strains tested transferred part or all oftheir resistance genes. The strains carrying R plasmids included the genera Escherichia, Klebsiella, Salmonella, Enterobacter, Proteus, Providencia and Citrobacter. These results indicate that R plasmids possibly play a major role in the emergence of antibiotic resistance among clinical isolates of Enterobacteriaceae.
Four strains of S. typhi isolated in Malaysia were found to show resistance to chloramphenicol and other antibiotics. In two of these strains it was possible to show that this resistance was transferable.
This problem which is widespread in neighbouring countries and undetected in Malaysia till recently has now been shown to exist in this country. Fears that the incidence of such strains will increase in the future are expressed and the need for vigilance is emphasised.