Nasopharyngeal carriage of Streptococcus pneumoniae and serotypes indentified among nursing home residents in comparison to the elderly and patients younger than 65 years living in domestic environment
Article Category: Original scientific article
Published Online: May 26, 2017
Page range: 172 - 178
Received: Jan 25, 2016
Accepted: Mar 23, 2017
DOI: https://doi.org/10.1515/sjph-2017-0023
Keywords
© National Institute of Public Health, Slovenia
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.
Elderly living in nursing homes represent 5% of the total elderly population in Slovenia (1). Among them respiratory tract infections are the second most prevalent and represent one of the most frequent causes of morbidity, mortality and hospital admissions (1-3). In this group, pneumonia is regarded a special category due to advanced age, numerous co-morbidities and non-specific, but often severe disease course, which all contribute to a high (30%) mortality rate (2). One of the main pathogens causing pneumonia in the group of elderly is S.
The estimated incidence of pneumonia among nursing home residents in the United States is 365/1000 residents per year and it is significantly higher in comparison to elderly living in domestic environment (20-40/1000) (13). Due to frequent and sometimes unjustified use of antibiotics, numerous antibiotic resistant pneumococcal strains develop (4, 13), representing an increasing problem worldwide (5, 14).
The incidence of invasive pneumococcal disease in Slovenia was 11.9/100,000 in year 2012 (most frequently pneumonia) (15). The highest rates were among children under 5 years of age (46.2/100,000) and among elderly over 65 years of age (27/100,000) (15). Among adults most prevalent serotypes, causing invasive pneumococcal disease, were 3, 9V, 14, 4, 1, 23F and 19F (15). Similar data was found in United States, German and Czech studies (16-18).
Although pneumococcal pneumonia is an important cause of morbidity and mortality among nursing home residents and represents great cost for the society (19), pneumococcal vaccination rates remain low (6, 13, 20). In situations where vaccination rates within a closed population, such as in a nursing home, are less than 5%, there is a greater risk for pneumococcal infection outbreak (6). Pneumococcal vaccination represents effective protection from pneumococcal pneumonia for an individual and vaccination of critical number of individuals can lead to herd immunity effect (6, 21).
So far, there is little data available on pneumococcal vaccination rates (20) and no data on asymptomatic NPCR and serotypes in the population of nursing home residents in comparison to adults living in domestic environment in Slovenia. Therefore the goal of this research is to gain these data.
We performed a cross sectional epidemiological study, in which two swabs were taken from all the participants (one swab every year) in two consecutive years (February 2013 – November 2013 and February 2014 – November 2014).
The study included 151 nursing home residents from “Dom upokojencev center” in Ljubljana, 152 elderly living in domestic environment and 38 adults less than 65 years, all visiting General practitioners in the same region (“Zdravstveni dom Ljubljana Center”). Due to lack of data, 2 of the participants in the first year, both from the group of elderly living in domestic environment, and one participant in the second year, from the group of nursing home residents, were excluded from the analysis.
Inclusion criteria were i) no sign of acute respiratory infection, ii) living in a defined geographical region in a domestic environment or retirement home and iii) informed consent form signed by the patient or patient’s legal representative.
Exclusion criteria were i) ongoing acute respiratory infection, ii) living outside defined geographical region, iii) refusal to sign informed consent form by patient or patient’s legal representative, iv) the use of antibiotics in the two weeks prior to taking the swab, and v) immunocompromised patients (hematological malignancies, inherited immunodeficiency, HIV, post splenectomy status, cancer chemotherapy).
Recruitment of participants started in the nursing home. We asked all the residents from “unit Poljane” to participate. On-site recruitment approach, with the possibility to turn down the participation was used. This was previously identified as one of more successful approaches (22). 95 out of 168 decided to join the study. We continued in “unit Tabor”, where the random number method was used until we included the expected number of participants. The same method was used to select the participants among elderly patients and adults less than 65 years from different General practitioner offices at “Zdravstveni dom Ljubljana Center”. These were contacted by telephone.
Case report form was filled in for each participant. It included patient’s identification number, gender, age, preceding vaccination data against influenza and pneumococcal infections, preceding antibacterial therapy (from three months up to two weeks prior to taking the swab), data on preschool children contacts, corticosteroid or immunosuppressant treatment and data on chronic diseases. This data was collected by reviewing patient medical files and by taking patient history.
We used R Sterile Copan swab (Copan, Brescia, Italy) with a universal transport medium to take a sample from nasopharynx. Nasopharyngeal space is currently defined as the most appropriate spot for
The swabs were transferred to the National Laboratory of Health, Environment and Food, Centre for Medical Microbiology, Department for Public Health Microbiology, Laboratory for Public Health Bacteriology, Ljubljana, Slovenia no later than 24h after specimen collection, where the identification and serotyping of S. pneumonia was performed.
The cultures were grown on Columbia blood agar with 5% sheep blood and Blood agar with bovine blood, both manufactured at the laboratory, and incubated on 35±2 °C in the 5% CO2 for 48h. The plates were checked for the presence of suspected
The collected data was analyzed with SPSS, version 20.0.0. Pearson Chi Square test was used to test the differences between different groups of participants. A value of p<0.05 was used as a limit to describe significant scientific differences between groups.
In the group of nursing home residents, the average age was 85.24 years (range 67-105 years), 120 (79.4%) were females and 31 (20.6%) were males.
In the group of elderly from domestic environment, the average age was 82.07 years (range 65-97 years), 115 (76.7%) were females and 35 (23.3%) were males.
In the group of adults less than 65 years the average age was 55.34 years (range 47-64 years), 19 (50%) were females and 19 (50%) were males.
NPCR were low in groups of elderly studied in two consecutive years. In the group of adults less than 65 years NPCR were higher, in the second year NPCR in this group was significantly higher, compared to others (p<0.05) (Table 1).
Number of positive swabs in different groups in two consecutive years. p<0.05Nursing home residents Elderly domestic environment Adults < 65 years 2 (1.3%) n=151 1 (0.7%) n=150 2 (5.3%) n=38 2 (1.6%) n=129 1 (1%) n=104 3 (8.8%) n=34
71 participants were eliminated from the study after the first year; 42 participants turned down the second swab (1 from nursing home residents, 38 elderly from domestic environment and 3 adults less than 65 years) and 29 due to death (20 nursing home residents, 8 elderly from domestic environment, 1 adult less than 65 years).
There were five positive swab results in the first year (Table 2) and six in the second (Table 3). Serotype 6B and a nontypeable
Characteristics of participants with positive swab result and in the previous season in the last 5 years in the last month NT, non-typeable; /, not applicable Characteristics of participants with positive swab result and in the previous season in the last 5 years in the last month /, not applicableParticipant Nr. 1 Participant Nr. 2 Participant Nr. 3 Participant Nr. 4 Participant Nr. 5 88 years 78 years 80 years 47 years 58 years Female Male Female Male Male Nursing Home Nursing Home Domestic Environment Adults <65 years Adults <65 years No Yes No No No No Yes No No No No No No No Yes No No No No Yes No Yes No No Yes / / / No Yes / / Yes No / Yes Yes / No / No Yes No No No No / No No No Participant Nr. 1’ Participant Nr. 2’ Participant Nr. 3’ Participant Nr. 4’ Participant Nr. 5’ Participant Nr. 6’ 86 years 77 years 80 years 47 years 58 years 60 years Male Female Female Male Male Female Nursing Home Nursing Home Domestic Environment Adults <65 years Adults <65 years Adults <65 years No No No No No No No No No No No No No No No No Yes No No No No No Yes Yes No No No No Yes No / / / No Yes No Yes Yes Yes No / No / / / No / No
The rate of influenza vaccination was significantly lower in the group of adults less than 65 years, compared to both groups of elderly, the rate of influenza vaccination was significantly higher in the group of nursing home residents, compared to elderly from domestic environment (Table 4). The rate of pneumococcal vaccination was low in all the groups, there was no statistically significant difference (Table 4). There was also no difference considering preschool children contacts and immunosuppressant therapy. Antibiotic consumption rate was significantly higher in both groups of elderly, compared to adults less than 65 years and the number of comorbidities (≥3) was significantly higher in the group of nursing home residents, compared to others. Death incidence was significantly higher among nursing home residents, compared to the other two groups, whereas the rate of second swab refusal, was significantly higher in the group of elderly living in domestic environment, compared to others.
Characteristics of participants with negative swab results in two consecutive years. p<0.05 – see discussion p<0.05 – see discussion p<0.05 – see discussion p<0.05 – see discussion p<0.05 – see discussion p<0.05 – see discussion p<0.05 – see discussion a in the previous season, b in the last 5 years, c in the last monthNursing home residents Elderly domestic environment Adults <65 years First year Second year First year Second year First year Second year Yes 50 (33.6%) 23 (18.1%) 31 (20.8%) 20 (19.4%) 2 (5.6%) 2 (6.4%) No 99 (66.4%) 63 (49.6%) 118 (79.2%) 56 (54.4%) 34 (94.4%) 28 (90.3%) Unknown / 41 (32.3%) / 27 (26.2%) / 1 (3.3%) Yes 4 (2.7%) 4 (3.1%) 9 (6%) 8 (7.8%) 0 / No 145 (97.3%) 123 (96.9%) 139 (93.3%) 94 (91.2%) 36 (100%) 31 (100%) Unknown / / 1 (0.7%) 1 (1%) / / Yes 43 (28.9%) 37 (29.1%) 19 (12.8%) 12 (11.7%) 5 (13.9%) 4 (12.9%) No 106 (71.1%) 90 (70.9%) 130 (87.2%) 91 (88.3%) 31 (86.1%) 27 (87.1%) Unknown / / / / / / Yes 29 (19.5%) 26 (20.5%) 38 (25.5%) 28 (27.2%) 14 (38.9%) 12 (38.7%) No 119 (79.9%) 100 (78.7%) 111 (74.5%) 75 (72.8%) 22 (61.1%) 19 (61.3%) Unknown 1 (0.6%) 1 (0.8%) / / / / Yes 9 (6%) 6 (4.7%) 6 (4%) 4 (3.9%) 0 / No 140 (94%) 121 (95.3%) 143 (96%) 99 (96.1%) 36 (100%) 31 (100%) Unknown / / / / / / Yes 38 (25.5%) 35 (27.6%) 64 (43%) 43 (41.7%) 11 (30.6%) 10 (32.3%) Yes 50 (33.6%) 42 (33.1%) 43 (28.9%) 28 (27.2%) 5 (13.9%) 4 (12.9%) Yes 47 (31.6%) 38 (29.9%) 21 (14.1%) 14 (13.6%) 4 (11.1%) 3 (9.7%) Yes 19 (12.8%) 8 (5.4%) 1 (2.8%) No 130 (87.2%) 141 (94.6%) 35 (97.2%) Yes 1 (0.7%) 38 (25.6%) 3 (11.2%) No 148 (99.3%) 111 (74.4%) 32 (88.8%)
Swab analysis in two consecutive years in nursing home residents showed a NPCR of 1.45% on average, which is similar to the data found in the United States study among retirement community residents (25). Some characteristics of nursing home residents in our study, such as a higher number of patients with two or more comorbidities in the group of nursing home residents and a more common use of antibiotics in this group, were similar to the data found in studies by Lee and Sundvall (26, 27). An average NPCR in the group of elderly living in domestic environment in two consecutive years was 0.85%, which also correlates to some studies conducted among the elderly, where NPCR were 0.32% and 5.3%, respectively (28, 12). Most of the pneumococci isolated were serotyped, some of them were non-typeable, which means they did not have the polysaccharide capsule.
6B and 9N serotypes are present, along with other serotypes, in the 23-valent polysaccharide pneumococcal vaccine (PPV23); moreover, 6B is also present in the 13-valent conjugate pneumococcal vaccine (PCV13). The one
Although NPCR among the elderly are low, this group represents a high risk population for invasive pneumococcal disease. This might implicate that longterm pneumococcal carriage among the elderly is rare, and that newly acquired pneumococci are responsible for invasive pneumococcal disease (31, 32). Seasonality also affects pneumococcal carriage rates - pneumococci are transmitted better during cooler and drier months (33).
The nasopharyngeal swab analysis among adults less than 65 years old showed that pneumococcal carriage rates were higher in this group in comparison to the elderly population – 5.3% in the first year and 8.8% in the second year. This may be because the participants from this group have more preschool children contacts (39.5%), compared to the groups of the elderly, although statistically significant difference was not confirmed in this case. Adults less than 65 years old carried 35 F (chronic carrier), 18C, 3 and a non-typeable serotype. None of the participants were vaccinated with either of pneumococcal vaccines.
The strong side of this study is that it is the first study addressing the topic of pneumococcal carriage and serotype identification among nursing home residents and the elderly living in domestic environment in Slovenia, and that the results of this study (low NPCR and serotype diversity) are consistent with foreign studies (34). There are also some limitations to this study. The first is that the sample is not representative, since it includes only participants from one nursing home and one community health center in the same region, and as the number of participants is not very high. The second limitation is that the study was not conducted in the coolest and driest months of the year, which might have influenced our results.
Although the NPCR among nursing home residents are low, the incidence of pneumonia (3) and the mortality rate in this population are significantly higher in comparison to the group of the elderly living in domestic environment (30% vs.16.7%) (2). In 2012, 81% of invasive pneumococcal infections in the population >65 years of age in Slovenia were caused with serotypes included in the PCV13 vaccine and 95% with serotypes included in the PPV23 vaccine (15). Pneumococcal vaccines are important means of invasive disease prevention, and are related to a lower mortality rate from pneumococcal pneumonia (6); nevertheless, the vaccination rates remain low also according to our data (3.3% in nursing home residents and 6% in the elderly from domestic environment).It is necessary to increase the number of vaccinated elderly.
Our data suggests that NPCR among the elderly are low and not significantly different in nursing home residents, compared to the elderly living in domestic environment. We identified different serotypes in all groups, only one person was a chronic carrier (serotype 35F). Our data also shows that pneumococcal vaccination rates are low in all compared groups, despite the benefits the vaccination brings.