A field comparison of four samplers for enumerating fungal aerosols I. Sampling characteristics

This study compared the performance of four bioaerosol samplers, the Reuter Centrifugal Air Sampler, the Andersen N6 single stage, the Surface Air System 90, and the Air-o-Cell, in measurements for airborne fungal propagules collected in 75 public building sites without prior knowledge of water damage or mold problems in British Columbia, Canada. The samplers had differences in detection limits, reproducibility, and overall yield. However, high and significant correlations between samplers (indoor samples: Pearson r = 0.60-0.85, P < 0.001) suggest that relative performances between samplers were reasonably consistent. These results indicate that fungal airborne concentration data are dependent on the methods used for assessment, and introduce additional variability in exposure assessment studies.

PRACTICAL IMPLICATIONS

In the absence of a standard protocol for sampling bioaerosols, the interpretation of aerosol data reported in indoor air quality studies is entirely dependent on an appreciation of the sampling characteristics of commonly used instrumentation. Although a number of comparative studies have been undertaken in the laboratory, only a few studies have made reported comparison data under field conditions. This study compared three culturable sampling devices, the Andersen N6, SAS 90, and RCS, and one particulate sampling device, the Air-o-Cell, in offices and public areas in a variety of buildings, under conditions of forced air or natural ventilation. The concentrations of fungal aerosols collected during simultaneous sample collection were highly correlated, yet varied by orders of magnitude. The performance of these devices must be carefully considered before a standard protocol can be promulgated.

Transmission of tuberculosis from smear negative patients: a molecular epidemiology study

BACKGROUND

While smear positive patients with tuberculosis (TB) are considered more infectious than smear negative patients, the latter can also transmit TB.

METHODS

In a molecular epidemiology study of 791 patients in the Greater Vancouver regional district, the number of episodes of TB transmission from two groups of smear negative clustered patients by RFLP (assumed to be involved in recent transmission) was estimated after assessing for potential bias. Group 1 (n = 79) included patients with pulmonary TB or pulmonary + extrapulmonary disease (PTB or PTB+EPTB); group 2 (n = 129) included all patients in group 1 + extrapulmonary cases alone.

RESULTS

In the total sample the mean (SD) age was 51 (21) years, 54.3% were male, and 17.0% of patients were clustered. Compared with smear negative patients, smear positive patients were more likely to be in a cluster (OR = 2.0, 95% CI 1.1 to 3.6) and to have had a history of ethanol abuse (OR = 2.7, 95% CI 1.0 to 6.7), diabetes mellitus (OR = 2.8, 95% CI 1.1 to 7.0), injection drug use (OR = 3.1, 95% CI 1.1 to 8.3), and to have had a previous hospital admission (OR = 8.5, 95% CI 5.1 to 14.0). The proportion of episodes of transmission from smear negative clustered patients ranged from 17.3% to 22.2% in group 1 and from 25% to 41% in group 2.

CONCLUSION

In Greater Vancouver, smear negative cases appear responsible for at least one sixth of culture positive episodes of TB transmission.

Patient selection: indications and contraindications

Patient selection is critical to the success of PLDD. In general, the herniation must have continuity with the parent disc; rupture of the annulus is not a contraindication. Several other orthopedic conditions constitute absolute or relative contraindications. All patients must be individualized. Our criteria for inclusion is undergoing continuing change. What is unacceptable now may, with modifications, become acceptable in the future. It is important not to adopt a fixed position at this early stage of PLDD.

A neurosurgical perspective on PLDD

This paper discusses the evolution of PLDD and its risks and complications, and points out some advantages and disadvantages. It presents data from a clinical study of 81 patients in which three technologies--automated percutaneous discectomy, KTP, and Nd:YAG laser instruments--were used. The study concludes that PLDD is safe and cost-effective. If the patients are properly chosen PLDD can be a good choice for treatment of herniated lumbar discs.

Pulmonary penicillosis marneffei: report of the first imported case in Canada

A 57-year-old female, born in Laos and who had lived in Thailand prior to immigrating to Canada in 1989, was seen by her physician with a chief complaint of cough and dyspnea. Her chest X-ray showed bilateral pulmonary air fluid levels. A fungus, with a diffusible red pigment, tentatively identified as Penicillium marneffei, was isolated from the patient's bronchial washings and sputum specimens. At 37 degrees C, the fungus converted to a yeast form when cultured on brain heart infusion agar. Microscopic examination of this culture revealed yeast cells that reproduced by fission. The identity of the patient's isolate was confirmed as P. marneffei with an exoantigen test. The patient's serum demonstrated specific antibodies to P. marneffei antigen. Treatment with amphotericin B and ketoconazole resulted in clinical improvement, clearing of chest X-rays and conversion to sero-negativity. Our case is the first recorded diagnosis of imported penicillosis marneffei in Canada. The minimal inhibitory concentrations recorded for the patient's isolate to fluconazole, 5-fluorocytosine, itraconazole and miconazole were 12.5, 0.39, < 0.195 and < 0.195 micrograms/ml, respectively.

Mutations in the catalase-peroxidase gene from isoniazid-resistant Mycobacterium tuberculosis isolates

Isoniazid resistance in Mycobacterium tuberculosis has been associated with total deletion of the katG gene, which codes for catalase-peroxidase production. To determine whether this is a common mechanism of drug resistance, 9 isolates of isoniazid-resistant and 1 of isoniazid-sensitive M. tuberculosis were analyzed by polymerase chain reaction amplification of a 237-bp sequence of the katG gene. Amplification was observed in the isoniazid-sensitive isolate and in 8 resistant isolates; in only 1 isoniazid-resistant isolate was there no amplification of the expected band, suggesting gene deletion. DNA sequencing showed that 8 of the 9 isolates had point mutations, deletions, or insertions of 1-3 bases. Evidence corroborating the presence of mutations in the katG gene was obtained by single-strand conformation polymorphism analysis in these 8 isolates. Thus, mutations as well as insertions and deletions in the katG gene can account for inactive catalase peroxidase, leading to isoniazid resistance; gene deletion occurs only infrequently, in approximately 11% of cases.

Need for treatment of gonorrhea to be effective against Chlamydia trachomatis

Men and women with gonorrhea or contact to gonorrhea are frequently co-infected with Chlamydia trachomatis. To assess the importance of using treatment regimens active against both Neisseria gonorrhoeae and C trachomatis, tetracycline 500 mg orally four times daily for five days, with activity against both organisms, was compared with ceftriaxone, 250 mg once intramuscularly, with activity against only N gonorrhoeae. N gonorrhoeae microbiological failure occurred in six of 148 patients (4%) on tetracycline and zero of 85 on ceftriaxone. Microbiological failure for C trachomatis occurred in zero of 27 on tetracycline and 10 of 12 (83%) on ceftriaxone (P<0.001). In addition, 14 others on ceftriaxone had C trachomatis first isolated after treatment. When all types of microbiologialc and clinical failures are included, outcome was significantly better on tetracycline (P<0.001). Optimal treatment of patients with gonorrhea must include regimens with activity against both C trachomatis and N gonorrhoeae.

Intrathoracic paediatric tuberculosis: a report of 202 cases

Until recently paediatric tuberculosis rates were in decline in developed countries, but more recently there has been a significant change in these trends. Tuberculosis in British Columbia (BC) is centralized and all paediatric cases diagnosed between 1979 and 1988 were reviewed. There were 252 notifications during the study period but 50 cases were excluded (31 extrapulmonary cases, 11 with missing records and 8 because of incorrect diagnoses). There were 109 (54%) female patients. The age range was 4 months-15 years (6.4 +/- 4.1 years). 52% were 5 years old or less. 75 (37.1%) were aboriginal Canadians, 61 (30.2%) were Asian, 50 (24.8%) were Caucasian and 16 (8%) were included in miscellaneous or unknown groups. Primary pulmonary disease occurred in 197 (97.5%); the remaining 5 had post-primary disease. A history of close contact was elicited in 158 children (78.2%). All but 8 (4%) had a positive PPD response to 5TU. 40% of children had symptoms, the most frequent being cough (51%) and fever (28.4%). Mycobacteriology was carried out in 169 (83.7%) children. Bacteriologic confirmation was achieved in 45 patients (22.2%). Chest X-rays were reviewed in 186 cases. Lymphadenopathy occurred in 93.5%, with hilar (34%) and combined hilar-paratracheal (26%) being the commonest findings. The majority of patients were treated with isoniazid and rifampin, with a minority receiving streptomycin or pyrazinamide in the initial intensive phase. 14 (6.9%) children had adverse reactions to their drugs but these were rapidly reversed with the withdrawal of the responsible drug. Response to therapy was excellent and there were no deaths.

Characterization of a DNA probe for detection of Mycobacterium tuberculosis complex in clinical samples by polymerase chain reaction

We cloned and sequenced a DNA fragment from Mycobacterium tuberculosis for use in the identification of members of the M. tuberculosis complex. The DNA probe for culture confirmation had a sensitivity and a specificity of 100%. By using primers developed from this probe, the polymerase chain reaction detected 20 mycobacteria by ethidium bromide staining. This polymerase chain reaction system demonstrated 98% sensitivity and 100% specificity for detection of the M. tuberculosis complex in 200 sputum specimens.

Comparison of in vitro antimicrobial susceptibilities of Mycobacterium avium-M. intracellulare strains from patients with acquired immunodeficiency syndrome (AIDS), patients without AIDS, and animal sources

Difloxacin, A-56620, cefazolin, cefotaxime, ceftizoxime, cephapirin, SK&F 88070, and spectinomycin were used to compare the in vitro susceptibilities of Mycobacterium avium-M. intracellular isolates from patients with acquired immunodeficiency syndrome (AIDS), patients without AIDS, and diseased animals. Against the isolates from humans without AIDS, the quinolone compounds difloxacin and A-56620 were found to be the most effective, each inhibiting 50% of strains at a concentration of 2 micrograms/ml. The remaining antimicrobial agents had MICs for 50% of strains tested of at least 32 micrograms/ml. Statistically significant differences were observed in the antibiogram patterns among the M. avium-M. intracellulare strains from each of the three sources.

In vitro susceptibilities of Mycobacterium tuberculosis to 10 antimicrobial agents

After preliminary in vitro screening of 10 antimicrobial agents against Mycobacterium tuberculosis, the MICs of the 6 most promising agents against 27 clinical isolates were determined by agar dilution. The two quinolone compounds tested (difloxacin and A-56620) were the most active, each inhibiting 50% of the strains at concentrations of 4 micrograms/ml. M. tuberculosis strains previously shown to be resistant to isoniazid, streptomycin, rifampin, or ethambutol were as susceptible to these quinolone compounds as susceptible strains.

Botulism from chopped garlic: delayed recognition of a major outbreak

Diagnosis of botulism in two teenaged sisters in Montreal led to the identification of 36 previously unrecognized cases of type B botulism in persons who had eaten at a restaurant in Vancouver, British Columbia, during the preceding 6 weeks. A case-control study implicated a new vehicle for botulism, commercial chopped garlic in soybean oil (P less than 10(-4)). Relatively mild and slowly progressive illness, dispersion of patients over at least eight provinces and states in three countries, and a previously unsuspected vehicle had contributed to prolonged misdiagnoses, including myasthenia gravis (six patients), psychiatric disorders (four), stroke (three), and others. Ethnic background influenced severity of illness: 60% of Chinese patients but only 4% of others needed mechanical ventilation (P less than 10(-3]. Trypsinization of serum was needed to show toxemia in one patient. Electromyography results with high-frequency repetitive stimulation corroborated the diagnosis of botulism up to 2 months after onset. Although botulism is a life-threatening disease, misdiagnosis may be common and large outbreaks can escape recognition completely.

Inner-city survey for tuberculosis: evaluation of diagnostic methods

A total of 1,271 persons living in a socially and economically depressed, inner-city area of Vancouver, British Columbia, voluntarily attended a tuberculosis case-finding campaign. Chest x-ray, on-the-spot specimen of sputum, and tuberculin skin test were offered at the time of the first attendance. All 3 diagnostic methods were found to be well accepted, with 93% of the participants having an x-ray, over 95% producing a sputum specimen, and almost 95% having a tuberculin test (a quarter of these did not, however, report for reading of the test). Eight cases of bacteriologically confirmed pulmonary tuberculosis were found: 6 suspected on x-ray (the remaining 2 films were abnormal but not diagnostic of tuberculosis), and 6 being positive on smear and/or culture of the initial on-the-spot sputum specimen. Examination of a second specimen of sputum diagnosed all of the 8 active cases identified by the survey. These results suggest that, in this particular setting, a chest radiogram taken by a transportable chest x-ray apparatus or examination of 2 sputum specimens might be equally successful at detecting all cases of active pulmonary tuberculosis within the time required for sputum culture. Examination of the sputum smear immediately identifies all the more infectious cases of pulmonary tuberculosis. The prevalence rate of 629 per 100,000 among those presenting themselves to this campaign illustrates the high-yield which might be achieved by active case-finding projects in known high-incidence segments of a generally low-incidence population.

Endemic institutional strongyloidiasis in British Columbia

The incidental finding in 1984 of Strongyloides stercoralis larvae in a resident of a chronic care institution who had a vague clinical illness prompted a review of the other residents. Five other cases were identified after exhaustive laboratory investigations. Fecal-oral spread was considered the most likely manner of the spread of infection. The possibility of endemic strongyloidiasis in institutions should be considered, even in temperate climates, when there is unexplained persistent illness or high eosinophil counts. Serologic testing is a useful adjunct to fecal examination in such situations.

In vitro activity of Ro 15-8074, Ro 19-5247, A-56268, and roxithromycin (RU 28965) against Neisseria gonorrhoeae and Chlamydia trachomatis

In vitro Ro 15-8074 and Ro 19-5247 (T2525), two new oral cephalosporins, were active against 410 penicillin-susceptible and -resistant isolates of Neisseria gonorrhoeae. Two new macrolides, A-56268 and to a lesser extent roxithromycin (RU 28965), were active against Chlamydia trachomatis. A-56268 had activity against N. gonorrhoeae similar to that of erythromycin.

In vitro activity of difloxacin hydrochloride (A-56619), A-56620, and cefixime (CL 284,635; FK 027) against selected genital pathogens

Management of sexually transmitted diseases is facilitated by having antimicrobial agents with activity against all of the major genital pathogens. Newer quinolones show promise of being active against Neisseria gonorrhoeae and Chlamydia trachomatis. Two quinolones, difloxacin (A-56619) and A-56620, and an oral cephalosporin, cefixime (CL 284,635; FK 027), were evaluated in vitro. All three were highly active against 400 isolates of N. gonorrhoeae, including penicillinase-producing N. gonorrhoeae, N. gonorrhoeae with chromosomally mediated resistance, and isolates with penicillin MICs of less than 1 microgram/ml. Susceptibilities to one antimicrobial agent were usually strongly correlated with susceptibilities to the other antimicrobial agents evaluated, but isolates with increasing resistance to beta-lactams were least likely to show increasing resistance to quinolones. Difloxacin and, to a lesser extent, A-56620 were active against all 10 strains of C. trachomatis, and both had moderate activity against over 200 strains of Gardnerella vaginalis. Based on in vitro activity, difloxacin and A-56620 merit in vivo assessment for management of both C. trachomatis and N. gonorrhoeae infections, and cefixime shows considerable promise for treatment of N. gonorrhoeae infections.

In-vitro susceptibility of 400 isolates of Neisseria gonorrhoeae in Vancouver, 1982-84

Consecutive isolates of Neisseria gonorrhoeae obtained at a sexually transmitted disease clinic in Vancouver between June 1982 and June 1984 were tested for in-vitro susceptibility to eight antimicrobial agents. Of the 400 isolates 6 (1.5%) were penicillinase-producing N. gonorrhoeae, and for 25 (6.2%) the minimum inhibitory concentrations (MICs) of penicillin were 1.0 to 4.0 micrograms/ml. Ceftriaxone sodium was the most active agent. The MICs were higher than those reported in a Canadian study in 1973-74, except for tetracycline hydrochloride. The patterns of susceptibility of the isolates to one antimicrobial agent correlated significantly with those to each other agent, although the relation was weakest for trimethoprim-sulfamethoxazole and spectinomycin. The results reinforce the need to evaluate local in-vitro susceptibility patterns, especially since the proportion of isolates with relative and absolute resistance to penicillin is increasing.

Strongyloidiasis in Canadian Far East war veterans

A survey was done of Canadians who had been interned by the Japanese during World War II to assess the prevalence of latent infection with Strongyloides stercoralis in this group. Packages containing three mail-in kits and a questionnaire were sent to 992 men, 694 (70%) of whom responded. Larvae were found in the stool specimens of four of the respondents. Examination of stool specimens after formalin-ether concentration was the most successful method of detecting Strongyloides larvae. The Baermann concentration technique yielded negative results in all four men. Three of the four cases of strongyloidiasis were detected after sampling of three fecal specimens. In the fourth case additional specimens were requested on the basis of data derived from the questionnaire. The most frequently cited clinical manifestations were abdominal pain, weight loss, diarrhea and rashes.

Isolation and geographic distribution of Mycobacterium other than M. tuberculosis in British Columbia, 1972-81

It has been suggested that the incidence of infection with mycobacteria other than typical tubercle (MOTT) bacilli is increasing. Laboratory and epidemiologic information relating to MOTT infection in British Columbia between 1972 and 1981 was analysed. Patient records for 1960-81 were also analysed. Of the 313 661 laboratory specimens 13 474 yielded Mycobacterium tuberculosis isolates and 3172, MOTT isolates. Over the 10 years the number of M. tuberculosis isolates declined, whereas the absolute and relative numbers of MOTT isolates increased. Members of the highly drug-resistant MAIS complex (M. avium-intracellulare, M. scrofulaceum and M. simiae) accounted for 73.3% of the 1778 potentially pathogenic MOTT isolates. MAIS isolation rates varied geographically. Analysis of patient records revealed 217 MOTT infections, of which 152 (70%) were due to MAIS organisms. Further studies are needed to determine the source of MAIS organisms in order that the infection and the disease may be more clearly understood.

Microscopic evaluation of sputum specimens submitted for Mycobacterium tuberculosis culture

Using microscopic screening criteria employed in the study of sputum in acute bacterial pneumonia, the authors evaluated 644 sputum samples from 347 patients submitted for mycobacterial bacterial culture. After microscopic examination, these specimens were processed using standard mycobacterial laboratory technics. Salivary specimens accounted for 67.1% of the samples evaluated, and yielded 13 of the total 42 Mycobacterium tuberculosis isolates, as well as 4 of the 21 smear-positive culture-positive specimens. Although specimens from the lower respiratory tract are preferred, specimens of a salivary nature should not be discarded by the Mycobacteriology Laboratory.

Persistent skin and nail infection by an exotic fungus, Hendersonula toruloidea

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Serotyping of Campylobacter jejuni isolated from sporadic cases and outbreaks in British Columbia

Campylobacter jejuni from sporadic cases and outbreaks of gastroenteritis were serotyped on the basis of heat-extracted soluble thermostable antigens identified with the use of the passive hemagglutination technique. A total of 168 isolates were separated into 45 different types. The largest proportion of the isolates fell into three serotypes, each with 11 to 12.5% of the total number. Three less frequently occurring serotypes each included approximately 5%, and the remaining 50% of the isolates were distributed among 39 other serotypes. In most cases, serotyping demonstrated that epidemiologically linked isolates were of the same serotype, but the outbreak strains could belong either to frequently or to infrequently isolated serotypes. The high correlation between clinical findings and serotyping results confirmed the applicability of the serotyping scheme in epidemiological investigations of C. jejuni infections.

System for laboratory proficiency testing in bacteriology: organisation and impact on microbiology laboratories in health care facilities funded by the Ontario Government

The Ministry of Health requires that all medical laboratories in the Province of Ontario participate in a laboratory proficiency testing program (LPTP). In bacteriology compliance has been excellent. Eighty-six laboratories, for various reasons over the period under review, have surrendered their licence or, because of poor performance on LPTP test surveys, have had their licence withdrawn by the Ministry. The highest percentage of withdrawals occurred in small hospitals in isolated areas. In April 1979 there were 249 participating laboratories. Participants' results are first analysed by computer, and, subsequently, approximately 20% of participants' reports are reviewed by the Committee. Various Committee actions ensue: correspondence with the laboratory director regarding errors; an offer of a visit; and possibly a report via a senior LPTP committee to the Ministry that a laboratory is non-proficient and, in LPTP's terms of reference, non-remediable. Subsequent Ministry action might be the withdrawal of a laboratory's licence. However, this last recourse only occurs when educational efforts have proved ineffectual. Overall, performance in LPTP bacteriology surveys has improved over the period 1975-8, with 68% of 263 laboratories achieving a score of 70% or higher and 26% of 263 laboratories scoring less than 60%.

Rapid presumptive identification of Gardnerella vaginalis (Haemophilus vaginalis) from human blood agar media

Presumptive identification of Gardnerella vaginalis from 48-h human blood agar cultures by using a Gram stain, hemolysis, and colonial morphology was highly accurate.

Precipitate produced by Serratia marcescens on MacConkey agar: useful diagnostic test

The production of a precipitate by Serratia marcescens on Oxoid MacConkey agar has proven useful as a laboratory diagnostic test. This phenomenon is specific for Serratia within the Enterobacteriaceae, although precipitate production is also given by Acinetobacter anitratus and some Pseudomonas, Alcaligenes, and Aeromonas species. Precipitate production seems to be specific for certain batches of MacConkey agar, and is probably related to a specific property of some batches of bile salts.

A regional quality control program in microbiology. II. Advantages of simulated clinical specimens

A regional quality control program was established using simulated clinical specimens introduced into the routine workload of participating laboratories in such a way that they were not detected as quality control specimens. Comparison of performance between these specimens and lyophilized cultures showed that additional information was obtainable with the former. In particular, it was observed that common pathogens such as Escherichia coli are poorly identified in clinical material. The examination of urines was inferior to examination of other types of specimens. The implications of these findings for the practice of diagnostic bacteriology are discussed.

A regional quality control program in microbiology. I. Administrative aspects

Conventional proficiency testing programs in microbiology using recognizable materials yield limited information. To assess overall laboratory competence in the handling of routine clinical material, other methods are needed. This report describes the use of "blind," simulated clinical specimens in a regional quality control program. Details of the administration, including technics, costs, logistics, and limitations, are presented.

Compliancy in splint-wearing behaviour of patients with rheumatoid arthritis

Forty-six patients with rheumatoid arthritis affecting their hands were questioned to establish whether or not they complied with the medical specialist's instructions about wearing splints. Only one-third of the patients appeared to comply. A high extraversion score (measured on the EPI questionnnaire) identified half of the patients who did not comply. All patients scored significantly lower then the population norm on the introversion-extraversion dimension, indicating that this dimension may be involved in the psychosomatic aspect of rheumatoid arthritis.

A practical system of bacterial nomenclature

It is unlikely that any serious attempt will be made to standardize bacterial nomenclature on a national or international scale until the implementation of the proposed revision of the International Code of Nomenclature of Bacteria on 1 January 1980. In the meantime, the lack of such standardization poses major problems in communication between the laboratory and the clinican and also causes difficulties in the latter's reading of the bacteriology literature. The present communication proposes interim regional voluntary standardization of bacterial nomenclature as a solution, and outlines a system of nomenclature which could be used on such a regional basis. The system is specifically designed to demonstrate clearly the relationships between bacteria.

Carriage of potentially pathogenic bacteria in the hair

Using an improved technique for sampling, the carriage rate of Gram-negative bacilli and Staphylococcus aureus in the hair was studied in two groups of surgical inpatients and two control groups drawn from the hospital stag and a hospital outpatients' clinic. No significant differences in the hair carriage rate of Gram-negative bacilli were observed between the patients and the control groups, or between patients with and without Gram-negative wound infection. The hair carriage rate of Staph. aureus was highest in the hospital staff group, and was significantly higher also in the outpatient control group than in the inpatient groups. The potential implications of these findings on hospital infection are discussed.

Establishing tokens as conditioned reinforcers with long-stay psychiatric patients

Tokens were swiftly established as conditioned re-inforcers for a large group of long-stay psychiatric patients. The method involved exchanging tokens, immediately they were received, for the back-up reinforcement. This was found to be efficient when compared to a previous study and resulted in considerably greater increases in response rates. The target behaviour was verbal participation in a social activity and the increases in participation were maintained when the exchange of tokens for back-up reinforcement was delayed. The method is especially useful for setting up token programmes.

The effect of token reinforcement on verbal participation in a social activity with long stay psychiatric patients

A token reinforcement programme was set up to increase verbal participation in a weekly quiz for a ward of 38 male long term psychiatric patients. Response rates were measured and it was found that the amount of participation increased markedly when reinforced but returned to the original low level when reinforcement was discontinued. The study demonstrates that a token reinforcement procedure is effective in increasing the patients& verbal participation in a social activity.

Gentamicin blood agar used as a general-purpose selective medium

The potential value of a blood agar medium containing a final concentration of 5.5 mug of gentamicin per ml was assessed in a diagnostic laboratory over an 8-week period. The medium gave increased isolation rates of beta-hemolytic streptococci, other streptococci, Bacteroides, clostridia, and yeasts. It also proved valuable in detecting gentamicin-resistant gram-negative bacilli when these were present in heavy mixed culture.

A technique for bacteriological sampling of hair

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Gentamicin as a selective agent for the isolation of beta haemolytic streptococci

The isolation of beta haemolytic streptococci was compared using Columbia sheep blood agar with and without gentamicin in a final concentration of 5.5 micrograms per ml. The inclusion of gentamicin gave greatly improved results whenever the isolation of this organism in pure culture was complicated by overgrowth with Gram-negative bacilli or staphylococci.

Search for Serratia

During a four-month period an intensive effort was made to isolate and identify every Serratia marcescens strain present in the clinical material received for bacteriological assessment in the laboratory. Ten strains were isolated from eight patients, the organism possibly being responsible for infection in five of these patients. Serratia marcescens is thus commoner than expected and it is difficult to explain the fact that there are so few references to it as a pathogen in the British literature.

Evaluation of three methods using deoxyribonuclease production as a screening test for Serratia marcescens

Deoxyribonuclease (DNase) produced by Serratia marcescens is a characteristic feature which is useful in distinguishing this organism from closely related members of the Enterobacteriaceae. In an assessment of three methods of performing the DNase test as a screening procedure for Serratia marcescens, the conclusion was reached that the standard test was most suitable for use in the clinical bacteriology laboratory.

Sensitivity of Nocardia to trimethoprim and sulphonamides in vitro

Studies in vitro of the sensitivity to trimethoprim and sulphonamides of nine strains of N. asteroides, two strains of N. caviae, and one of N. blackwellii are presented. No unequivocal evidence of synergism was found. Despite this, the inclusion of trimethoprim in the drug regime when sulphonamides are used in the treatment of nocardiosis is suggested on empirical grounds.