From 1997 to 2000, Mycobacterium tuberculosis was diagnosed in two Asian elephants ( Elephas maximus ), three Rocky Mountain goats ( Oreamnos americanus ), and one black rhinoceros ( Diceros bicornis ) in the Los Angeles Zoo. DNA fingerprint patterns suggested recent transmission. An investigation found no active cases of tuberculosis in humans; however, tuberculin skin-test conversions in humans were associated with training elephants and attending an elephant necropsy.

While evaluating quinolone resistance in a sample of Campylobacter isolates recovered from patients with campylobacteriosis in Los Angeles County, California, in 1998, we discovered that the second most frequently isolated species was Campylobacter upsaliensis (6 [4%] of 155 isolates). The ability of laboratories to recover this species may be dependent on the culture conditions and the media used. Three dogs living in the households of 2 of these 6 patients had C. upsaliensis isolated in their stool specimens.

Preventing transmission of multidrug-resistant tuberculosis is critical because of treatment toxicity, cost, and the lack of effective therapy for latent infection. We attempted to determine the extent of transmission in Los Angeles County by comparing relatedness of multidrug-resistant tuberculosis cases using restriction fragment length polymorphism and by cross-matching contact information to the Tuberculosis Registry. Strain typing was done on isolates of 102 pulmonary multidrug-resistant cases identified between August 1993 and 1998. Seventy-one (70%) of the cases had cavitary lesions on chest radiograph, and 94 (92%) had sputa smear-positive for acid fast bacilli. Fifteen (15%) of the cases were known to be infected with human immunodeficiency virus. Four molecular clusters of two cases each and one closely related pair were identified among the 102 cases; contact investigation successfully identified all clusters but one. Among 946 contacts identified and cross-matched with the county's Tuberculosis Registry, one secondary case due to drug-resistant Mycobacterium bovis was found. To summarize, a very high proportion of pulmonary multidrug-resistant tuberculosis cases in Los Angeles County were infectious. Molecular strain typing indicated limited spread of disease, although it underestimated transmission compared with contact investigation. We believe aggressive surveillance and case management were critical to limiting the spread of multidrug- resistant tuberculosis.

An epidemiological and microbiological investigation of a cluster of eight cases of Legionnaires' disease in Los Angeles County in November 1997 yielded conflicting results. The epidemiological part of the investigation implicated one of several mobile cooling towers used by a film studio in the centre of the outbreak area. However, water sampled from these cooling towers contained L. pneumophila serogroup 1 of another subtype than the strain that was recovered from case-patients in the outbreak. Samples from two cooling towers located downwind from all of the case-patients contained a Legionella strain that was indistinguishable from the outbreak strain by four subtyping techniques (AP-PCR, PFGE, MAb, and MLEE). It is unlikely that these cooling towers were the source of infection for all the case-patients, and they were not associated with risk of disease in the case-control study. The outbreak strain also was not distinguishable, by three subtyping techniques (AP-PCR, PFGE, and MAb), from a L. pneumophila strain that had caused an outbreak in Providence, RI, in 1993. Laboratory cross-contamination was unlikely because the initial subtyping was done in different laboratories. In this investigation, microbiology was helpful for distinguishing the outbreak cluster from unrelated cases of Legionnaires' disease occurring elsewhere. However, multiple subtyping techniques failed to distinguish environmental sources that were probably not associated with the outbreak. Persons investigating Legionnaires' disease outbreaks should be aware that microbiological subtyping does not always identify a source with absolute certainty.

In 2002, we investigated a cluster of patients with Alcaligenes xylosoxidans bloodstream infections by conducting a matched case-control study and a prospective study. Pulsed-fi eld gel electrophoresis (PFGE) was performed on blood culture isolates, and 1 explanted central venous catheter (CVC) was tested for biofi lm. We identifi ed 12 cases of A. xylosoxidans bloodstream infection. Case-patients were more likely than controls to have had a CVC (7/7 [100%] vs 4/47 [8.7%], respectively; p<0.0001). Ten case isolates were indistinguishable by PFGE analysis, and A. xylosoxidans biofi lm from the CVC matched the outbreak strain. We observed multiple breaches in infection control, which may have caused contamination of multidose vials used to fl ush the CVCs. Our study links A. xylosoxidans with CVC biofi lm and highlights areas for regulation and oversight in outpatient settings.