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rettgeri. A wide range of serotypes was found, many having been previously reported from nosocomial isolates. A total of 15 % of isolates carried plasmids; six pairs of isolates were identified which had identical serotypes but different patterns of plasmid carriage. The antimicrobial sensitivity of the isolates was generally similar to isolates of Proteeae from humans. Although no truly aminoglycosideresistant isolates were found, some isolates of Prov. stuartii and Prov. rettgeri had MIC's higher than the other isolates to gentamicin and netilmicin, suggesting the presence of low levels of the enzyme AAC 2'. The study demonstrates that there is a considerable diversity of species and types of Proteeae associated with calves and their environment. It seems likely that a potential cause of colonization of the human gut by Proteeae is the consumption of meat.

The in-vitro susceptibilities of 198 isolates of precisely identified Proteeae species to six quinolone antimicrobials were determined. Significant differences in susceptibility patterns among various Proteeae to the quinolones examined were demonstrated. Although Providencia stuartii was found to be the most resistant to quinolones including the very active agent ciprofloxacin, fully speciated Prov. rettgeri were also markedly resistant as well. in contrast Prov. alcalifaciens was extremely sensitive to these agents. Some strains of Proteus penneri were more resistant to the three newer compounds (ciprofloxacin, enoxacin and norfloxacin) than strains of Pr. vulgaris suggesting that recognition of this species may be important in surveys of the in-vitro activity of antibiotics. Pr. mirabilis and Morganella morganii were very sensitive to the newer agents. The patterns of resistance seen in the three newer agents were reflected in the older agents acrosoxacin and cinoxacin. Accurate speciation of Proteeae in surveys of susceptibilities to antimicrobial agents is important if misleading results are not to be reported.

Examination of a series of isolates of Providencia stuartii collected over an 18 month period from a chronic-care patient at Bristol Royal Infirmary revealed the emergence of resistance to carbenicillin. Resistance was mediated by a 47 kb plasmid which transferred by conjugation to a plasmid-free strain of P. stuartii but not to Escherichia coli. Carbenicillin-sensitive isolates were either plasmid-free or contained a 36 kb cryptic plasmid. Restriction endonuclease mapping of this plasmid showed it to be closely related to 32 kb and 34 kb cryptic plasmids reported previously in P. stuartii from Bristol. Mapping of the R plasmid showed it to be derived from the 34 kb cryptic plasmid by transposition of two copies of Tn1.

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