ARCHIVED - Streptococcus pneumoniae outbreak in a rural Regina community

15 August 2006

Volume 32

Number 16

M Hennink, MB ChB, M Med (1), Z Abbas, MBBS, MPH (1), RR McDonald, MSc (2), E Nagle (2), KL Montgomery, BSc (2), T Diener, MB ChB, DCH, M Med, MPA (1), GB Horsman, MD, FRCPC (2), PN Levett, PhD, ABMM, FCCM (2)

1. Regina Qu'Appelle Health Region, Regina, Saskatchewan

2. Provincial Laboratory, Saskatchewan Health, Regina, Saskatchewan

Introduction

Bacterial conjunctivitis is caused by a wide range of Grampositive and Gram-negative organisms, including Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae, Neisseria
gonorrhoeae and Chlamydia trachomatis¹. Non-serotypeable Streptococcus pneumoniae is reported as a frequent cause of bacterial conjunctivitis².

A pharmacist from a small rural community (Community ‘A') within the Regina Qu'Appelle Health Region (RQHR) contacted the Population and Public Health Services, RQHR, on 9 March, 2005, to report a large number of people presenting at the local pharmacy with symptoms of conjunctivitis. The pharmacist reported selling more than 40 non-prescription over the counter (OTC) eye medications in the past 2 weeks, whereas he usually sold an average of one OTC eye medicine in a 4 week period.

An investigation to determine the extent of the outbreak, confirm the cause, identify the mode of transmission and implement control measures was initiated on 9 March, 2005. This investigation demonstrates the usefulness of molecular subtyping to identify related cases of conjunctivitis.

Methods

A case of conjunctivitis was defined as a resident of Community ‘A' and surrounding area with a clinical diagnosis of conjunctivitis or an episode of one of the following symptoms: red or itchy eyes, pain, eye lid edema, morning crusting or an exudate from one or both eyes with onset of symptoms after 1 January, 2005.

To identify additional cases of conjunctivitis, RQHR contacted area physicians and requested them to look for symptomatic patients, to obtain swabs for viral and bacterial culture and to report all cases to RQHR. Local elementary and high schools were requested to report any children or staff with conjunctivitis. Area pharmacists were also asked to advise symptomatic cases to submit swabs for bacterial and viral culture.

RQHR staff conducted interviews of all individuals with onset of symptoms of conjunctivitis between 9 March and mid-April 2005. The questionnaire included items regarding demographic information as well as signs and symptoms. Questions regarding potential risk exposures included exposure to other symptomatic individuals and exposure to recreational waters and common gatherings.

All identified cases were asked to have swabs taken for bacterial and viral culture at the Provincial Laboratory. Culture swabs were obtained from cases presenting to area physicians after 9 March, 2005, and were also sent to the Provincial Laboratory for culture.

On 24 March, 2005, a questionnaire to identify children and staff members with conjunctivitis was sent to elementary and high schools in Community ‘A' and surrounding area. The schools were asked to report cases of conjunctivitis among students and staff since January 2005.

To limit transmission of infection RQHR issued the following recommendations:

• Patients were encouraged to wash their hands frequently and thoroughly using soap and water.
• Household members and other contacts of cases were encouraged to practice proper hand hygiene and to avoid sharing eye make-up and eye medications.
• The area schools were advised to thoroughly clean and disinfect shared items, door knobs and gym equipment.
• The schools were also advised to exclude symptomatic children until evaluated and cleared for readmission by a health care provider.
• Students at the local schools were encouraged to seek treatment for symptoms of conjunctivitis.

Schools were provided with fact sheets regarding conjunctivitis.

Following isolation of S. pneumoniae from conjunctivitis cases, a selection of isolates was subtyped by fluorescence-based amplified fragment length polymorphism analysis (fbAFLP)³. An additional eight non-serotypeable isolates collected between 1997 and 2005 (and presumed to be epidemiologically unrelated) were included in the fbAFLP analysis along with the outbreak isolates. Four outbreak isolates were sent to the National Centre for Streptococcus Reference Laboratory for serotyping.

Results

A total of 47 cases of conjunctivitis were identified in Community ‘A' and surrounding area with onset of symptoms between 9 March and 14 April, 2005 (Figure 1). Symptoms included red eyes (36/47, 77%), pain (19/47, 40%), eyelid edema (26/47, 55%) and exudate (31/47, 66%). The median age was 16 years (range: 3 months to 58 years), and 27 cases (57%) were female. Approximately 60% of cases presented with, or developed, bilateral eye involvement. Purulence was noted in over 60% of the cases. The average duration of symptoms was < 10 days. There was no concurrent pneumonia. There were no hospitalizations and no deaths. All cases were treated with topical penicillin.

Figure 1. Conjunctivitis cases with known date of onset Community ‘A' and surrounding areas, 9 March to 14 April, 2005

A further 65 cases were identified retrospectively by the elementary and high schools in the area. At these two schools, 59 cases were reported among students and six cases among staff.

Specimens for culture were obtained from 47 cases of conjunctivitis. S. pneumoniae was isolated from eye cultures in 18 (38%) of the Community ‘A' residents. All isolates of S. pneumoniae were susceptible to penicillin, erythromycin, clindamycin, chloramphenicol and fluoroquinolones. Haemophilus influenzae was isolated from three cases, of whom two also yielded S. pneumoniae. Viral cultures were uniformly negative.

Table 1. Summary of conjunctivitis cases in Community ‘A' residents,
9 March to 14 April, 2005

Four representative isolates referred to the National Centre for Streptococcus were non-serotypeable. fbAFLP molecular fingerprinting clustered 27 S. pneumoniae isolates into two distinct clusters consisting of three (cluster B) and 24 (cluster A) isolates each (Figure 2). Two isolates did not generate suitable fingerprint patterns and were not comparable. Each cluster included at least one isolate that was non-serotypeable. None of the eight additional non-serotypeable isolates showed significant similarity to either of the two outbreak clusters.

Figure 2. Dendrogram depicting fbAFLP analysis of S. pneumoniae isolates. Clusters A and B denote outbreak cases

Non-serotypable = Non sérotypable; Blood = Sang; Ear = Oreille; Eye = Oeil

 

Discussion

This outbreak of conjunctivitis continued for approximately 3 months and involved residents of Community ‘A' and surrounding areas. Cases were identified and cultures obtained after local physicians were notified of the outbreak. Interviews with cases late in the course of the outbreak indicated that the transmission had occurred in both household and school settings. Mucopurulent discharge was the most commonly reported symptom in this outbreak. More than half of the cases had bilateral involvement. Laboratory investigations performed in the late course of the outbreak indicated that a majority of the cases were due to S. pneumoniae. H. influenzae was the only other potential pathogen detected, but was isolated from only three cases.

Non-serotypeable S. pneumoniae caused the majority of cases of conjunctivitis. Molecular subtyping indicated that most of outbreak isolates of S. pneumoniae were genetically very similar to each other. A second strain appears to have been circulating at the same time in the same region, and was recovered from three patients.

Outbreaks of pneumococcal conjunctivitis are almost invariably associated with nontypeable strains of S. pneumoniae, which are usually nonencapsulated². A range of molecular typing approaches has been applied to non-typeable strains from sporadic cases and outbreaks, including pulsed field gel electrophoresis⁴, multilocus sequence typing^1,5 and BOX-PCR fingerprinting ⁶. Essentially, all these approaches, including the fbAFLP approach used in this investigation, confirm that outbreak strains of S. pneumoniae are clonal and are genetically unrelated to isolates from sporadic cases.

The reports of new cases of conjunctivitis declined markedly in mid April. It is unknown if recommendations for infection control practices issued by RQHR contributed to halting this outbreak or the start of Easter break contributed to mitigating the spread of the pneumococcal conjunctivitis.

In summary, we report an outbreak of pneumococcal conjunctivitis, from which the majority of isolates were shown to be clonal by molecular typing using fbAFLP.

 

Acknowledgements

The authors wish to thank the staffs of Population and Public Health Services, Regina Qu'Appelle Health Region; Provincial Laboratory, Saskatchewan Health; and the National Centre for Streptococcus in Edmonton.

References

1. Crum NF, Barrozo CP, Chapman FA et al. An outbreak of conjunctivitis due to a novel unencapsulated Streptococcus pneumoniae among military trainees. Clin Infect Dis 2004;39:1148-54.

2. Shayegani M, Parsons LM, Gibbons WE et al. Characterization of nontypable Streptococcus pneumoniae-like organisms isolated from outbreaks of conjunctivitis. J Clin Microbiol 1982;16:8-14.

3. Antonishyn NA, McDonald RR, Chan EL et al. Evaluation of fluorescence-based amplified fragment length polymorphism analysis for molecular typing in hospital epidemiology: Comparison with pulsed-field gel electrophoresis for typing strains of vancomycin-resistant Enterococcus faecium. J Clin Microbiol 2000;38:4058-65.

4. Martin M, Turco JH, Zegans ME et al. An outbreak of conjunctivitis due to atypical Streptococcus pneumoniae. New Engl J Med 2003;348:1112-21.

5. Berron S, Fenoll A, Ortega M et al. Analysis of the genetic structure of nontypeable pneumococcal strains isolated from conjunctiva. J Clin Microbiol 2005;43:1694-8.

6. Barker JH, Musher DM, Silberman R et al. Genetic relatedness among nontypeable pneumococci implicated in sporadic cases of conjunctivitis. J Clin Microbiol 1999;37:4039-41.