Evaluation of the Sirscan automated zone reader in a clinical microbiology laboratory.

We compared readings of Kirby-Bauer plates by the Sirscan, an automated image analyzer that measures zone diameters, to those of experienced clinical microbiologists measuring zones with a hand-held caliper interfaced to a computer and with a ruler. To read plates of Escherichia coli, Morganella morganii, and Pseudomonas aeruginosa containing 12 antibiotic disks the Sirscan took 11 s; technologists took 28 s by caliper and 39 s by ruler. Reading times of four different technologists ranged from 22 to 44 s with the caliper and 10 to 12 s with Sirscan. Upon repeated testing zone size variation rarely exceeded 3 mm by caliper and 1 mm by Sirscan. Over a 4-month period, 368 clinical isolates were tested prospectively by both methods in the Clinical Microbiology Laboratory of the Miriam Hospital. There was good correlation of zone sizes for most antibiotics, but Sirscan zone diameter measurements tended to be 3 to 5 mm larger than caliper readings for ciprofloxacin, norfloxacin, aztreonam, erythromycin, clindamycin, and trimethoprim-sulfamethoxazole. Very major errors (resistant by caliper and susceptible by Sirscan) occurred with 10 of 3,770 readings (0.3%), mainly where breakpoint criteria lacked an intermediate zone. They occurred in testing staphylococci with amoxicillin-clavulanate (5 of 127 isolates, 3.9%), pseudomonas with piperacillin (1 of 28, 3.6%), coagulase-negative staphylococci with oxacillin (2 of 74, 2.7%), gram-negative bacilli with cefuroxime (1 of 209, 0.5%), and mixed species with trimethoprim-sulfamethoxazole (1 of 366, 0.3%). The Sirscan zone reader facilitates accurate, fully quantitative susceptibility testing in clinical microbiology laboratories.

Early settlements in Newfoundland and the scourge of scurvy.

Two important archeological investigations currently underway in the Avalon Peninsula of Newfoundland, at Cupids (established 1610) and Ferryland (1621), help to focus questions on health and health care in early seventeenth-century English settlements. This review looks at one aspect only, the problem of scurvy and what treatments were tried. In adding to our understanding of early colonial settlements and on how new medicinal plants were "discovered," the Newfoundland story reveals a considerable interest in local plants as substitutes for scurvy grass. Suggestions are offered on how they may have been chosen and the rationales behind their use.

Evolution of extended-spectrum beta-lactam resistance (SHV-8) in a strain of Escherichia coli during multiple episodes of bacteremia.

Nine isolates of Escherichia coli were recovered from seven blood cultures over a period of 3 months from a 19-month-old female with aplastic anemia. Initial isolates were susceptible to extended-spectrum cephalosporins, including ceftazidime (MIC, < or = 0.25 microgram/ml), but gradually became resistant to this drug (MICs, > or = 128 micrograms/ml) and other cephalosporins and the monobactam aztreonam. Molecular typing methods, including plasmid profile analysis, pulsed-field gel electrophoresis, and arbitrarily primed PCR, indicated that the nine isolates were derived from a common ancestor. Dot blot hybridization and PCR analysis of total bacterial DNA using blaSHV- and blaTEM-specific DNA probes and primers identified the presence of a blaTEM beta-lactamase gene in all of the isolates and a blaSHV gene in the isolates with elevated ceftazidime MICs. Isoelectric focusing analysis of crude lysates showed that all nine isolates contained an enzyme with a pI of 5.4 corresponding to the TEM-1 beta-lactamase, and those isolates containing an SHV-type beta-lactamase demonstrated an additional band with a pI of 7.6. The first of the ceftazidime-resistant isolates appeared to hyperproduce the SHV enzyme compared to the other resistant isolates. DNA sequencing revealed a blaSHV-1 gene in the first ceftazidime-resistant isolate and a novel blaSHV gene, blaSHV-8, with an Asp-to-Asn substitution at amino acid position 179 in the remaining four isolates. Three of the ceftazidime-resistant isolates also showed a change in porin profile. The patient had received multiple courses of antimicrobial agents during her illness, including multiple courses of ceftazidime. This collection of blood isolates from the same patient appears to represent the in vivo evolution of resistance under selective pressure of treatment with various cephalosporins.

Comparative susceptibility of clinical isolates producing extended spectrum beta-lactamases to ceftibuten: effect of large inocula.

BACKGROUND: Infections caused by Enterobacteriaceae producing extended-spectrum beta-lactamases (ESBLs) are a growing clinical problem. However, there is wide variation in the level of resistance to third generation beta-lactams conferred by these enzymes. METHODS: We studied 33 Klebsiella pneumoniae and 4 Escherichia coli isolates producing ESBLs obtained from outbreaks in 14 different hospitals and a nursing home in the United States. Microdilution testing with standard (10(4-5) colony-forming units/ml) and large (10(6-7) colony-forming units/ml) inocula, was used to compare the minimum inhibitory concentrations (MICs) of ceftibuten, a novel oral oxyimino beta-lactam, with those of other third generation beta-lactams (cefotaxime, ceftazidime, aztreonam, cefixime, cefpodoxime and cefoxitin). RESULTS: Twenty-seven of the clinical isolates had well-characterized ESBLs of 10 different types, 7 of which produced TEM-1; 1 isolate also produced LXA-1. Two strains produced more than 1 ESBL. The remaining 10 strains produced 8 as yet uncharacterized types of ESBL. With large inocula 73% tested susceptible to ceftibuten, whereas 8 to 22% tested susceptible to the other third generation beta-lactam antibiotics. Ceftibuten MICs increased with higher inocula when tested against strains producing SHV-4 or SHV-5 and, to a lesser extent, strains producing multiple beta-lactamases. Only cefoxitin showed a smaller inoculum effect. CONCLUSION: Ceftibuten merits clinical evaluation in infections caused by bacteria that produce ESBLs.

Medical books: for information or learning? Reflections on the books of three Newfoundland physicians, c.1860 to c.1970.

This study describes the medical books of three physicians in rural Newfoundland who followed each other chronologically. Spanning the years c.1860 to c.1970, the nearly 300 books prompt a variety of questions about the physicians themselves, their practices, and their reading habits. These enquiries raise further questions about the extent to which medical books are read for factual information or for contemplating more general issues about the nature of disease and the nature of the individual.

A public health response to cancer clusters in Missouri.

A protocol was developed in 1984 by the Missouri Department of Health to provide a systematic method for responding to citizen reports of cancer clusters. This protocol integrates public health and environmental expertise and includes two stages: the preliminary review and the investigation. The preliminary review is focused on problem definition and hypothesis generation. Cancer mortality and incidence data are reviewed. Information is gathered and verified through the efforts of citizens, local health officials, environmental staff, and the cancer program staff. Epidemiologic factors evaluated include type of cancer, temporal and spatial relations, population at risk, community profile, and possible environmental and occupational factors. The investigation is an expanded analytic study. Resources are focused on cancer inquiries that appear most likely to involve manageable common exposures. Program experience and protocol development highlights, including surveillance system improvement and educational programming, are described.

The role of user's perceived control in interface design, employing verbal protocol analysis.

This paper outlines some general strengths and weaknesses of using psychological theoretical approaches beyond their original domains, focusing on Rotter's (1966) Internal and External (I/E) Locus of Control construct. Rotter's theory examines perceived locus of control of individuals during their social interactions. The issues of why and how I/E may be a useful theoretical approach to human-computer interaction (HCI) are addressed. Specific problems encountered in importing I/E into HCI are then described. An interface evaluation experiment is discussed. First, the system used for evaluation purposes is described, as well as the verbal protocol technique used, and the methods of analysis. Finally, the conclusions about the interface are presented. In this contact, I/E as an interface evaluation tool is discussed, as are related issues of importing psychological theories into HCI.

Report of an illness outbreak at the Harry S Truman State Office Building.

An acute epidemic of headache, mucosal irritation, fatigue, odd taste, and dizziness involving several hundred state government employees occurred in June 1986 in an office building in Missouri that housed 2,500 employees. A survey of 305 ill and 131 well employees demonstrated that ill employees were more likely to have perceived unusual odors and inadequate air flow in their work areas. The building has eight floors, seven of which are divided in half by an atrium, and 17 separate air handling systems. A total of 87% of the ill employees were concentrated in only three of the "half floors." Extensive investigation revealed no toxic substances or other direct causes for the illnesses, but several factors were identified that may have reduced air quality in the affected areas. These included a low proportion of outside air, associated with crowding, blocked vents, smoking, and use of office chemicals. This pattern of illness suggests epidemic anxiety state triggered by poor air quality.

Possible factors influencing distribution and prevalence of Echinococcus granulosus in Utah.

A descriptive epidemiologic study was designed to test an impression that infections of Echinococcus granulosus in dogs, sheep, and human beings were concentrated in central Utah, and to determine when and how the parasite was introduced into the state, which factors were involved in the distribution of the cestode, and which factors increased either a person's risk of infection of the number of people at risk. Data were secured by review of available records, interviews, questionnaires, and field observations. It was found that 37 of 39 infections in human beings, and seven of eight counties with endemic hydatid disease in dogs and sheep, are located in central Utah. Possible factors responsible for the increasing number of people at risk were use of local people as herders, the existence of community herds, and specific dog management practices. Determinants such as trailing sheep between seasonal pastures, association of sheepmen from several counties on winter range, and sheep marketing practices undoubtedly influence distribution of infections in dogs and sheep.