Practical genetic approaches have been helpful in the diagnosis, epidemiology, and taxonomy of bacterial pathogens encountered in our laboratory at the Centers for Disease Control. There are many examples in which plasmid profiles have been used to define epidemic strains of enteric bacteria, staphylococci, pseudomonads, vibrios, and other pathogenic bacteria. Current methodologies should allow the microbiology laboratory to use plasmid profiles routinely and to identify plasmids associated with bacterial pathogenesis.

Simplified DNA-DNA hybridization procedures have been used in our laboratory to survey or “probe” thousands of Escherichia coli colonies for the presence of enterotoxin genes, eliminating traditional tissue culture or animal assays. Research scientists continue to develop gene probes for a number of bacterial toxins and hemolysins and for the identification of pathogens such as legionellae and salmonellae. These and other probes as well as hybridization “kits” may be commercially available to diagnostic laboratories within the next few years.

In sera obtained between the 6th and the 30th day from 16 Austrian and 26 Hong Kong patients with culturally verified typhoid fever, agglutinating antibodies (microagglutination test) at significant titers were detected in 93% of the Austrian (median titer: 640) but in only 50% of the Hong Kong patients (median titer: 240). Similar results (93% and 54% positive sera respectively) were obtained for specific IgM as assessed by the enzyme-linked immunosorbent assay (ELISA) using lipopolysaccharide of S. typhi as antigen (median relative titer: 0.32 and 0.21 respectively). In contrast, specific IgG at significant concentrations were found in only 69% of the Austrian (median relative titer: 0.16) but 88% of the Hong Kong sera (median relative titer: 0.71). The (IgM-detecting) microagglutination test may be sufficiently diagnostic for typhoid fever in nonendemic areas such as Austria. In endemic regions like Hong Kong, however, tests indicative for early specific IgG are indispensable for serological diagnosis of the disease. The ELISA proved useful and is an example for such tests.

Eight cases of sternal/mediastinal infection due to Enterobacter species were seen in postoperative cardiac patients during 1980 to 1981. The attack rate was 14.5% (8/55), compared to 3.7% (2/54) for an identical period in 1979 to 1980 (p<0.05). Cases varied in severity from fulminant, acute bacteremic infections (one death) to less severe wound infection. Late complications or recurrences were not seen. There was a hospital-wide increase, relative to all other gram-negative bacillary isolates, in Enterobacter laboratory isolations, but no increased rate of infection in any other specific surgical condition.

No personnel, materials, or techniques were associated with the outbreak, and all but two environmental cultures were negative. Case-control analysis suggested that surgical complications and prophylactic cephalosporins were associated with infection. Prospectively, an additional 85 cardiac surgery patients had increased Enterobacter skin/wound colonization following perioperative prophylaxis with cephalosporin antibiotics. After introduction of barrier isolation and restriction of contacts no further mediastinitis occurred in 100 subsequent cardiac surgery patients. This study indicates that Enterobacter may be major pathogens causing post-cardiac-surgery infection not prevented by cephalosporin prophylaxis.

All patients at the new British Columbia's Children's Hospital with chickenpox or Herpes zoster are nursed with appropriate precautions in single-bed rooms provided with negative pressure ventilation. Over a period of 1 year, no nosocomial infections were detected on follow-up of 110 susceptible patients who had been on wards at the same time as six cases of chickenpox and one immunocompromised patient with cutaneous dissemination of Varicella zoster. In a preceding study at the previous hospital, with similar staff, control measures, and patient population, in an isolation facility without negative pressure ventilation, nosocomial infections occurred in seven out of 41 susceptible patients who were on the same ward as two patients with chickenpox. These findings suggest that a simple negative pressure ventilation system without air locks is a useful adjunct in the control of cutaneous Varicella infections.

In August 1983 a Symposium was held in Vancouver to discuss Q fever as a hazard to humans in contact with infected sheep. On the basis of new preliminary information presented and discussion at the Symposium, an attempt has been made in this document to supplement published guidelines for the conduct of sheep research.

The genus Enterobacter belongs to the tribe Klebsielleae found in the family Enterobacteriaceae. Members of this genus had previously been referred to as Aerobacter. The clinical importance of this genus as a separate entity was not fully appreciated until the 1960s. Until that time, the differentiation of Enterobacter from Klebsiella was not routinely performed, which resulted in many infections reported as being caused by the Klebsiella-Aerobacter group. Added confusion occurred at this time with the taxonomy change of Aerobacter to Enterobacter.