Identification of gram-negative aerobic fermentors in a clinical bacteriological laboratory

Construction and characterization of attenuated delta aroA delta virG Shigella flexneri 2a strain CVD 1203, a prototype live oral vaccine

We engineered an oral Shigella vaccine prototype that can invade intestinal epithelial cells but cannot undergo extensive intracellular replication or extend to adjacent epithelial cells. Strain CVD 1203, derived from wild-type Shigella flexneri 2a by introducing deletions in chromosomal aroA and invasion plasmid virG, was highly attenuated in the Sereny test. Two 10(9)-CFU orogastric doses (2 weeks apart) stimulated production of secretory immunoglobulin A antibodies to S. flexneri 2a and protected against conjunctival sac challenge with virulent S. flexneri 2a.

Transferable trimethoprim resistance in urinary tract pathogens isolated in Finland and Sweden

The incidence of trimethoprim resistance (MIC greater than 4 micrograms/ml) among urinary pathogens from inpatients was earlier shown to be 1.6-3.6% in Stockholm and 31-49% in Turku in 1977-1978. In strains from this study trimethoprim resistance could be transferred from 13/51 donor strains. Resistance to streptomycin was co-transferred in all matings but 2, and to tetracycline, ampicillin, carbenicillin and chloramphenicol in some cases. Sulphonamide resistance was co-transferred in 2 cases. In all matings but 1 at least 1 plasmid was transferred. A plasmid with similar molecular weight was transferred from 5 Turku and 4 Stockholm donor strains. Restriction enzyme digestion of this plasmid DNA showed many common bands after electrophoresis. In DNA-DNA duplex studies, using 3H-labelled Col E 1::Tn 7 as the probe, the presence of Tn 7 DNA sequences was confirmed in the 5 donor strains from Turku and 1 from Stockholm. Electrophoresis of plasmid DNA with and without digestion with restriction enzymes together with DNA-hybridization were thus useful methods to investigate the presence of genetic determinants for trimethoprim resistance in 2 areas. Other determinants than transposon Tn 7 were also present.

Trimethoprim resistance in hospitals

During November 1980 to April 1981, 1561 urinary tract pathogens were collected from Turku City Hospital, Turku University Central Hospital, and Kuopio University Central Hospital. Resistance of the strains was tested by agar-plate dilution against trimethoprim, sulphamethoxazole-trimethoprim, sulphamethoxazole, ampicillin, and nitrofurantoin. Resistance to trimethoprim (greater than 8 mg/l) occurred in 8.6-12.2% of strains from the university hospitals (Pseudomonas excluded) and 38.3% of strains from Turku City Hospital. Resistance of Escherichia coli occurred in 4.1-6.2% of strains from the university hospitals and 21% of strains from Turku City Hospital. Proteus mirabilis was the most resistant of the clinically important bacterial species with resistance to trimethoprim in 29-78%. Attention is called for in defining the type of hospital used for a particular study: bacterial resistance in different hospitals cannot be compared direct and one hospital is not necessarily representative for a whole country. After seven years' use of plain trimethoprim the prevalence of resistance in the two university hospitals in Finland was similar to that in a London hospital just before plain trimethoprim was registered for use in Britain.

Ceftazidime in the treatment of urinary tract infection

Twenty-nine patients with urinary tract infection were treated with ceftazidime intramuscularly, at a dosage of 1000 mg twice daily for 7 days. The patient series was predominantly geriatric, with a mean age of 70.9 years and including 17 patients over 75 years. Nine had an in-dwelling catheter and azotaemia was found in 14 cases. In this clinically difficult group, a positive bacteriological response to treatment was obtained in 72.9% and, if patients with in-dwelling catheters are excluded, 90% were cured. Ceftazidime-resistant Streptococcus faecalis was cultured before treatment in 6 of the 8 unsuccessful cases. In the remaining 2 treatment failures, Streptococcus faecalis was isolated immediately after treatment. In terms of clinical response to therapy all patients were cured or improved. Treatment with ceftazidime was well tolerated. No subjective side-effects occurred. One patient developed a distinct but transient elevation of liver enzymes, and in 2 cases a negative direct Coombs test was temporarily positive.

Effect of trimethoprim or trimethoprim/sulphamethoxazole usage on the emergence of trimethoprim resistance in urinary tract pathogens

The frequency of trimethoprim (TMP)-resistant bacteria isolated from urine was studied in hospitals, in Stockholm, Sweden, and Turku, Finland. TMP has been in clinical use in Finland since 1973, whereas in Sweden TMP was available only in combination with sulphamethoxazole (SMZ) at the time for this study. All samples were collected solely from in-patients at 4 different occasions during a 20-month period 1977-78. The frequency of TMP-resistant strains (MIC greater than or equal to 8 micrograms/ml) in Turku increased from 31 to 49%, whereas it remained at a low level (1.6-3.6%) in Stockholm during the whole period. Also the frequency of TMP/SMZ-resistant strains (MIC greater than or equal to 64 micrograms/ml) increased in Turku from 24 to 45% but remained at the same level, 0-4% in Stockholm. In Turku there was also an increased frequency of resistance to SMZ (MIC greater than or equal to 512 micrograms/ml), ampicillin (MIC greater than or equal to 32 micrograms/ml) and nitrofurantoin (MIC greater than or equal to 64 micrograms/ml), while these frequencies remained at their initial levels in Stockholm. The distribution of bacteria was different in the two areas. In Turku there was also a change towards more nosocomial strains during the observation period. Since antibacterial agents are used more frequently in Turku than in Stockholm, this might be one explanation to the increase of resistance in Turku.

Gentamicin resistance in gram-negative bacilli: occurrence of modifying enzymes and their influence on susceptibility testing

Among 272 gram-negative bacilli, regarded as strains with reduced susceptibility to gentamicin by the disc test, 156 strains were resistant (greater than or equal to f microgram/ml) by the agar dilution method. Altogether 76% of the 156 strains were cross-resistant to tobramycin, kanamycin, streptomycin and amikacin. Amikacin showed the highest antibacterial activity in vitro. 32 of the resistant strains produced acetylating or adenylylating enzymes, which caused resistance. The production of enzymes was not limited to any genera. Complete cross-resistance to aminoglycoside antibiotics was recorded in 45%, 98% and 22% respectively, of Pseudomonas aeruginosa, Ps. maltophilia and other gram-negative rods. Enzyme-producing strains were not cross-resistant to all aminoglycosides. Changes in MICs and inhibition zones with different inocula among enzyme-producing strains emphasize the importance of standardized inocula in susceptibility testing.

Cefuroxime in soft tissue infections and septicaemia

Data are presented on the absorption, antibacterial activity, clinical efficacy and side effects of cefuroxime in 33 cases with proven bacterial infection in soft tissues and in patients with septicaemia. The drug was administered mainly intramuscularly (i.m.) but also intravenously (i.v.). Peak serum concentrations 1 h after an injection of 750 mg cefuroxime i.m. were between 16-25 mug/ml. After 8 h the levels were mostly < 4 mug/ml in patients with normal renal function. I.v. injection gave only slightly higher maximum serum level obtained was approximately 40 mug/ml. No accumulation of the drug occurred in patients with normal renal function. Cefuroxime was active against all the gram-positive bacteria isolated from our patients as well as most of the gram-negatives. The clinical effect was satisfactory in 96%. The drug was well tolerated. Side effects were slight and relatively few.

Laboratory approaches to the identification of Enterobacteriaceae

There are numerous approaches to the identification of the Enterobacteriaceae in the clinical laboratory. Accuracy in identifying organisms is related directly to the skill and experience of the user and to the number of tests inoculated. Many of the commercially available kits offer reproducibility, convenience, accuracy, and ease of storage, particularly for smaller hospital laboratories that have neither the facilities nor the expertise to prepare and exert quality control over microbiologic media. However, none of the kits offers the accuracy and few offer the flexibility available through the use of conventional media, the variety and duration of incubation of which are virtually unlimited. The proper use of any system requires training because accurate identification requires the concurrent examination of colonial morphology and biochemical reactions-manufacturer's flow charts, reaction tables, or printed recognition systems notwithstanding. Microbiologists should be wary of new systems before impartial evaluations have been performed and published in scientific journals; manufacturers' technical literature and salesmen's presentations are, for obvious reasons, seldom objective.

Four hour-test for the identification of Enterobacteriaceae

A set of 12 rapid biochemical tests--lysinedecarboxylase, ornithinedecarboxylase, beta-galactosidase, urease, hydrogensulphide, indole, acetoin, deoxyribonuclease, esculin, mannitol, raffinose and sorbitol--were selected from an original set of 13 tests and were found to give 98% accurate reactions within 4 hrs of incubation for the identification of bacteria belonging to Enterobacteriaceae. This set permits identification on the genus and/or species level for Escherichia, Shigella, Citrobacter, Salmonella, Klebsiella, Enterobacter, Serratia and Proteus.