Detection of campylobacter species: a comparison of culture and polymerase chain reaction based methods

AIMS

To investigate the optimal method for the detection of campylobacters from stool samples by comparing selective culture with membrane filtration and the polymerase chain reaction (PCR).

METHODS

Three hundred and forty three stool samples were investigated by each of the three methods mentioned above. Selective culture was performed with charcoal cefoperazone desoxycholate agar plates. Membrane filtration was performed using cellulose triacetate membranes with 0.45 micro m pores placed on blood agar plates. Enteropathogenic campylobacters were detected using a PCR identification algorithm, consisting of screening PCRs and species identification using a PCR enzyme linked immunosorbent assay (PCR-ELISA), both based on the 16S rRNA gene.

RESULTS

Of the 343 samples tested, 23 were positive by one or more method. Of these, 17 were positive by selective culture, 12 by membrane filtration, and 20 by the PCR identification algorithm. A total of 18 of 23 positives were identified as C jejuni and/or C coli by the PCR identification algorithm, compared with 14 identified to the genus level by selective culture, and 10 by membrane filtration. Among the remaining five positive samples, one C hyointestinalis was detected only by the PCR identification algorithm; one C upsaliensis was detected only by the PCR identification algorithm; one Campylobacter sp was detected by membrane filtration and selective culture and later identified as C concisus; one Campylobacter sp was detected by membrane filtration alone and later identified as Arcobacter sp; and one Campylobacter sp detected only by selective culture was lost to study and therefore not speciated. There was no significant difference between detection by selective culture and the other two methods. However, detection by PCR was significantly better than by membrane filtration (0.05 > p > 0.02).

CONCLUSION

The PCR identification algorithm can detect and identify Campylobacter spp to the species level and the result is obtained on the same day. However, PCR is expensive, labour intensive, and does not provide an isolate for further identification or typing. Selective culture is as good as the PCR identification algorithm for the detection of the two most common species, C jejuni and C coli, and it is cheap and practical. However, it does miss the less common species, results take 48 hours, and identification is only to the genus level. Membrane filtration showed a low sensitivity compared with the other methods and is not appropriate for the diagnostic laboratory, although it was the only method to detect the Arcobacter sp. The optimum method for the detection of campylobacters from stool samples in the diagnostic laboratory remains selective culture.

A one-year survey of gonococcal infection seen in the genitourinary medicine department of a London district general hospital

The results of a one-year clinical, epidemiological and microbiological survey of gonococcal infection presenting to the Patrick Clements Clinic (PCC), a London district general hospital (DGH) genitourinary medicine (GUM) clinic, are presented. Clinical and epidemiological patient data were collected by a combination of questionnaire and retrospective case-note review. Microscopy performance within the PCC, outcome of treatment, return for tests of cure and efficacy of contact tracing were assessed. Isolates were tested for susceptibility to penicillin, tetracycline and ciprofloxacin. The study showed the PCC continues to diagnose and treat over 200 cases of gonorrhoea per year. High level resistance to penicillin, tetracycline and ciprofloxacin was documented among the year's isolates and antibiotic resistance was linked to acquisition of gonorrhoea overseas. Despite interviewing 183 patients concerning health advice and contact tracing issues, only 55% of new episodes re-attended for a first test of cure. In addition, only 29% of reported sexual contacts attended GUM clinics for investigation and treatment.

Detection of campylobacter in gastroenteritis: comparison of direct PCR assay of faecal samples with selective culture

The prevalence of campylobacter gastroenteritis has been estimated by bacterial isolation using selective culture. However, there is evidence that certain species and strains are not recovered on selective agars. We have therefore compared direct PCR assays of faecal samples with campylobacter culture, and explored the potential of PCR for simultaneous detection and identification to the species level. Two hundred unselected faecal samples from cases of acute gastroenteritis were cultured on modified charcoal cefoperazone deoxycholate agar and subjected to DNA extraction and PCR assay. Culture on CCDA indicated that 16 of the 200 samples contained 'Campylobacter spp.'. By contrast, PCR assays detected campylobacters in 19 of the 200 samples, including 15 of the culture-positive samples, and further identified them as: C. jejuni (16), C. coli (2) and C. hyointestinalis (1). These results show that PCR offers a different perspective on the incidence and identity of campylobacters in human gastroenteritis.

High level ciprofloxacin resistant gonorrhoea imported from Russia

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Carriage of Staphylococcus aureus in the elderly

The point prevalence and incidence of Staphylococcus aureus (methicillin-sensitive and -resistant) carriage by inpatients on acute elderly care wards was estimated. The relationship to body site and to previous admissions to hospital or other institutions was determined. Fifty-five patients were included in the point prevalence study and 136 in the incidence study, which was performed over a two-month period. One in three patients carried S. aureus and 1 in 20 was infected. The incidence rate for MRSA was 2.9%. No endemic strain was found. Nostrils were significantly associated with carriage, and skin break isolates were significant in the point prevalence survey. Screening these sites alone would be most cost effective.

Internal audit in a microbiology laboratory

AIM

To set up a programme of internal laboratory audit in a medical microbiology laboratory.

METHODS

A model of laboratory based process audit is described. Laboratory activities were examined in turn by specimen type. Standards were set using laboratory standard operating procedures; practice was observed using a purpose designed questionnaire and the data were analysed by computer; performance was assessed at laboratory audit meetings; and the audit circle was closed by re-auditing topics after an interval.

RESULTS

Improvements in performance scores (objective measures) and in staff morale (subjective impression) were observed.

CONCLUSIONS

This model of process audit could be applied, with amendments to take local practice into account, in any microbiology laboratory.

Experience of HIV disease in a London District General Hospital

The aim of this paper is to describe and discuss the experience of HIV disease in Central Middlesex Hospital, London up to June 1993. A retrospective study of the total number of HIV-positive patients cared for was performed. In addition, prospectively collected data as part of local epidemiological surveillance from January 1987 to June 1993 on all HIV test requests was analysed. Between January 1987 and June 1993 3695 individuals were tested for HIV-1 antibody at Central Middlesex Hospital. Of these, 101 HIV-1 seropositive individuals were identified and have attended this District General Hospital. Seven HIV-1 seropositive individuals were identified from before December 1986. Sixty (56%) had acquired their infection heterosexually. Thirty-eight (35%) originated from the UK and 47 (44%) from sub-Saharan Africa; the remaining 23 (21%) originated from the rest of Europe, South America and the Caribbean. Thirty-four (31%) of the patient group developed AIDS during follow-up at the hospital and in 26 individuals AIDs developed within 2 months of their first positive HIV result. The mean survival of 20 patients after AIDS-defining diagnoses was 7 months 18 days. This unselected group of HIV-1 seropositive patients present late in the course of their HIV disease and survival following AIDS is poor.

The value of serum C-reactive protein levels as a marker of sepsis in intensive care unit patients

A one-year prospective study was carried out to assess the value of routine serum C-reactive protein (CRP) measurement in the early diagnosis of infection in ICU patients of a District General Hospital. Ninety-one patients were included in the study. Sixty-eight patients yielded 28 proved and 77 suspected episodes of infection. Control data were drawn from 23 uninfected ICU patients. Both absolute values and percentage rates of change were examined for the following variables: serum CRP, maximum daily temperature and peripheral white blood cell count. Neither absolute CRP levels nor rates of change in CRP were found to relate significantly to proved infection. In the group in whom infection was suspected but not proved, absolute CRP levels were higher than controls on the day before the suspected infection (p = 0.019), but were not significantly raised on the day of infection nor the day after. The only significant rises in CRP (> 25%) were found in the suspected infection group from the day before to the day of infection, when compared with controls (p = 0.04). Traditional markers of infection--maximum temperature and peripheral white blood cell count--were significantly associated with infection. Maximum temperature was significantly higher in both proved and suspected infection on the day before infection (p = 0.000 and 0.001), and on the day of infection (p = 0.025 and 0.03), compared with controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Gonorrhoea: signs, symptoms and serogroups

Over 19 weeks, 104 male patients attending a genitourinary medicine clinic with gonococcal urethritis were asked to complete a questionnaire detailing symptoms. Sixty-seven questionnaires were duly completed. The examining nurse documented signs. Ninety-one isolates of Neisseria gonorrhoeae were serogrouped and auxotyped, 55 of these were from patients who had completed a questionnaire. Patients presented earlier if they had a past history of gonorrhoea (p = 0.02). The serogroup of N. gonorrhoeae did not influence the amount of discharge, the presence of meatal inflammation, dysuria or penile tip irritation or the delay in presentation after appearance of discharge. Auxotype AHU was not associated with asymptomatic gonorrhoea.

Possible induction of systemic lupus erythematosus by human parvovirus

A 59 year old woman presented with an influenza-like illness preceding signs and symptoms strongly suggestive of systemic lupus erythematosus (SLE), which progressed over several months. Owing to these influenza-like symptoms, a viral cause of her illness was sought. Human parvovirus B19 serology was positive and antibodies to DNA were detected by two different methods. This patient is believed to be the first report of human parvovirus B19 infection coinciding with the onset of SLE. The evidence for B19 virus and the part it plays in autoimmunity and arthritis is discussed.

Duodenal intubation as a source of typhoid fever

Typhoid fever developed in three patients during a period of 13 weeks. Although each of these patients was admitted to a different London hospital, the patients became ill approximately 10 days after undergoing duodenal intubation in one gastroenterology unit. All other patients who had undergone duodenal intubation in the unit during that period of time were investigated. Salmonella typhi was isolated from bile and feces of two out of the 20 other patients (carriers). In each of the three patients who developed typhoid fever, intubation followed within two days of intubation of one of the carriers. After use in each patient, the polyvinyl tubes had been thoroughly washed with disinfectant and detergent. There were no further cases of typhoid fever when a new tube was used for each patient.

Antibody capture radioimmunoassay for anti-rubella IgM

An M-antibody capture radioimmunoassay (MACRIA) for anti-rubella IgM was developed. Under optimum conditions positive serum specimens bound up to 20 times as much radioactivity as negative specimens. Positive reactions were expressed in arbitrary units/ml by comparison with a calibration curve derived from results obtained with dilutions of a standard serum. The specificity of the assay was confirmed by testing IgM and IgG rich fractions of positive sera. One hundred and forty specimens from blood donors, patients whose sera contained rheumatoid factor and patients with acute, non-rubella, virus infections were tested by MACRIA. No significant non-specific reactions were detected. Paired sera from acute rubella (25 patients) and individual sera from suspected rubella (69 patients) were tested for anti-rubella IgM by MACRIA and by haemagglutination inhibition following sucrose-density-gradient fractionation. There was close agreement between the two methods. The capture assay was more sensitive and could be used to detect the weak IgM response in women given RA 27/3 vaccine. After the natural infection, the MACRIA was strongly positive for two months and remained weakly so for a further two months. Repeat testing of sera demonstrated good reproducibility of the assay. MACRIA proved a simple, sensitive and specific test for anti-rubella IgM and compared favourably with currently used techniques.

Rapid reading and recording of complement fixation tests by means of a microtitre plate scanner

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Rubella antibody measured by radial haemolysis. Characteristics and performance of a simple screening method for use in diagnostic laboratories

A simple method for preparing radial haemolysis gels for rubella antibody screening is described. In use it gave clear zones of haemolysis when a standard serum was tested at dilutions down to 5.6 i.u./ml rubella antibody. In five laboratories 8404 sera were screened by the method and the results were read by comparing zones of haemolysis with that of a standard serum diluted to contain 15 i.u/ml antibody. A zone greater than or equal to 15 i.u./ml, indicating immunity, was given by 7433 (88.4%) of the sera. No zone indicating susceptibility was seen with 748 (8.9%) sera. Small zones, less than 15 i.u./ml standard, were given by 189 (2.2%) sera, and in only 34 cases (0.4%) did non-specific haemolysis interfere with the test readings. Further testing of the radial haemolysis interfere with the test readings. Further testing of the radial haemolysis negative and low positive sera by the haemagglutination inhibition test gave rise to some discrepant results which are discussed.

Experience with radial haemolysis for rubella antibody screening

Twelve hundred and thirty three sera were tested in parallel by the single radial haemolysis (SRH) and by the simplified haemagglutination inhibition (HAI) technique in routine use in this laboratory. In 1203 (97.6%) of these sera the results were in agreement. The remaining 30 (2.4%) sera were re-tested by both methods because on initial testing the results obtained by the two methods did not agree; only three specimens remained discrepant. The SRH is a simple test to perform and discriminates clearly between positive and negative sera. It is particularly suitable for screening large batches of sera.

Determination of antimicrobial MIC by paper diffusion method

Because they are cumbersome, tests to determine the quantitative susceptibility of organisms to antimicrobial drugs are not performed routinely in many diagnostic laboratories. This paper describes a simple method of incorporating the antimicrobial drug in agar. It is an adaptation of the Rolinson and Russell technique which allows the determination of minimum inhibitory concentrations (MIC) of antimicrobial drugs for a large number of organisms. Results are comparable with those obtained when the standard agar dilution method is used. Strains of aerobic Gram-negative bacilli were tested by both methods using ampicillin (86 strains), cephaloridine (72 strains), trimethoprim (72 strains), and gentamicin (72 strains). Of the 302 tests thus performed, a difference in MIC of more than one double dilution was noted in only 11 tests. With one strain of Pseudomonas aeruginosa, however, it was not possible to detect ampicillin resistance by the method described in this paper.

Controlling infection in a district general hospital

The way in which hospital-acquired infection has been brought under control over a three-year period in a district general hospital is described. The main success has been achieved in reducing sepsis caused by Staph. aureus, especially methicillin-resistant strains, and Pseudomonas aeruginosa. These reductions were achieved in spite of inadequate ward isolation and operating theatre facilities, and before there was any marked change in patterns of prescribing antibiotics. Our experiences indicate the significant improvements that can be made in controlling nosocomial sepsis even without structural or other major alterations in a hospital, providing that the problem is fully appreciated and the infection control team are concerned enough to act vigorously in influencing their clinical colleagues.