R M Baird

Media used in the detection and enumeration of Staphylococcus aureus

Over the years a range of selective and diagnostic media have been developed to assist in the detection and enumeration of Staphylococcus aureus in routine food surveillance programmes and food poisoning investigations and these are reviewed here. Baird-Parker agar remains, however, the medium of choice for direct plating and enumeration of S. aureus in both Europe and the US. This paper also reports on a comparison of the productivity and selectivity of trypticase soy broth with 10% NaCl and 1% sodium pyruvate (PTSBS) with trypticase soy broth (TSB) for the isolation of S. aureus. Using three strains of S. aureus and a strain of S. hyicus the productivity ratio of PTSBS to TSBS ranged from -0.17 to 0.57. In the recovery of heat-injured cells of S. aureus, PTSBS offered little or no improvement over TSB with sodium chloride but no pyruvate in a three-tube MPN assessment. Of the seven other bacterial cultures tested, none grew well on the PTSBS. Selectivity ratios of 4.4-7 were found.

Contaminated medicaments in use in a hospital for diseases of the skin.

Topical medicaments used by patients with diseases of the skin were examined for microbial contamination. Ps. aeruginosa was isolated from stock pots of a diluted emulsifying ointment used as a soap substitute in the bath. Cross-contamination between patients and medicament was subsequently shown to have occurred.

Pseudomonas thomasii in a hospital distilled-water supply.

Summary The distilled water supply in a pharmacy was found to be contaminated with Pseudomonas aeruginosa and P. thomasii Disinfection of the piping system proved impracticable, and use of the water from this supply was discontinued.

Bacteriological contamination of products used for skin care in babies

Two hundred and thirty‐two products used in the skin care of babies were examined for bacterial contamination. Contamination rates were compared between unused samples collected from homes, those used in the home, and those used in the maternity wards of a local hospital. Products used and unused, originating from the home had a low incidence of contamination and small bacterial populations. One product used in hospital was found to be susceptible to contamination; several samples were contaminated with Gram‐negative rods. The significance of these contaminants in products used on babies is discussed and proposals are put forward for avoiding in‐use contamination.

IN‐USE CONTAMINATION OF INTRAVENOUS FLUIDS

In this study intravenous fluid systems were examined after use for microbial contamination. Factors affecting contamination rates were also examined. At the same time the techniques used by the staff in handling these systems were observed.

Microbial contamination of topical medicaments used in the treatment and prevention of pressure sores

Topical medicaments used in the treatment and prevention of pressure sores in patients in three hospitals were examined for Pseudomonas aeruginosa and Staphylococcus aureus contamination. Contamination rates were found to vary between hospitals and were affected by differences in the packaging of the product and in the method of application used by the nursing staff.

Microbial contamination of pharmaceutical products in the home

One thousand, nine hundred and seventy-seven pharmaceutical products used in the home were examined for microbial contamination. Viable micro-organisms were recovered from 14.0% of samples. Medicines used in the home are apparently not exposed to the same opportunities for contamination as those used in hospital.

A statement from the IUMS-ICFMH working party on culture media I

A categorization system for monographs on culture media is outlined which will lead to more rapid publication and a formal division into three classifications; draft, proposed and approved. This should assist the quality assurance and accreditation processes in food microbiology laboratories.

A COMPARISON OF TWO INCUBATION TEMPERATURES FOR THE ISOLATION OF GRAM-NEGATIVE CONTAMINANTS FROM RAW MATERIALS AND NON-STERILE PHARMACEUTICALS

Selective and non‐selective broth enrichment techniques may be used in the isolation of microbial contaminants from pharmaceutical products. A non‐selective method may give better recovery rates for damaged organisms. A trial was carried out to determine whether the recovery of Gram‐negative contaminants could be improved by using an incubation temperature of 30°C for 48 h, rather than the more widely used 37°C for 24 h. Contaminants were isolated from 3.2% of samples incubated at the lower temperature compared with 0.8% at the higher temperature. The recovery rate from raw materials improved noticeably (9.0% compared with 0.9%).

Pharmacopoeia — step one

Abstract A proposal is put forward to compile a pharmacopoeia listing common methods of monitoring and the most important media used in food microbiology. The purpose, format and design of the pharmacopoeia are discussed in detail.