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1
Vélez- GómezDE, etal. BMJ Open 2022;12:e054966. doi:10.1136/bmjopen-2021-054966
Open access
Prevalence of Chlamydia trachomatis
and Neisseria gonorrhoeae in the
homeless population of Medellín,
Colombia: a cross- sectional study
Diego Enrique Vélez- Gómez ,1 Natalia Torres- Vellojín ,1
Juan Camilo Grajales- Zapata ,1 Juan Guillermo McEwen- Ochoa ,1,2
Alonso Martínez ,1 Verónica Ramírez- Lopera ,1 Aracelly Villegas- Castaño 1
To cite: Vélez- GómezDE,
Torres- VellojínN, Grajales-
ZapataJC, etal. Prevalence
of Chlamydia trachomatis
and Neisseria gonorrhoeae in
the homeless population of
Medellín, Colombia: a cross-
sectional study. BMJ Open
2022;12:e054966. doi:10.1136/
bmjopen-2021-054966
►Prepublication history and
additional supplemental material
for this paper are available
online. To view these les,
please visit the journal online
(http://dx.doi.org/10.1136/
bmjopen-2021-054966).
Received 28 June 2021
Accepted 11 February 2022
1Microbiology and Parasitology
Department, Bacteria & Cancer
group, Universidad de Antioquia
- Facultad de Medicina,
Medellin, Colombia
2Cellular and Molecular
Biology Unit, Corporacion para
Investigaciones Biologicas,
Medellin, Colombia
Correspondence to
Dr Diego Enrique Vélez- Gómez;
diegovelezgomez@ gmail. com
Original research
© Author(s) (or their
employer(s)) 2022. Re- use
permitted under CC BY- NC. No
commercial re- use. See rights
and permissions. Published by
BMJ.
ABSTRACT
Objective To determine the prevalence of Chlamydia
trachomatis (CT) and Neisseria gonorrhoeae (NG) in
the homeless population in Medellín, Colombia, using
molecular diagnostic methods. It also intended to develop
a demographic prole, exploring associated factors and
the dynamics of the social and sexual interactions of this
community.
Design Cross- sectional study.
Setting Two homeless care centres in Medellín, Colombia.
Participants Homeless individuals that assisted to the
main homeless care centres of Medellín, Colombia from
2017 to 2019.
Primary and secondary outcome measures The
prevalence of CT and NG in this population using qPCR
detection, factors associated with CT and NG infection, and
the sociodemographic prole of the community.
Results The prevalence of CT infection was 19.2%, while
that of NG was 22.6%. Furthermore, being a female was
signicantly correlated to CT infection p<0.05 (adjusted
OR, AOR 2.42, 95% CI 1.31 to 4.47). NG infection was
signicantly associated with factors such as: sexual
intercourse while having a sexually transmitted infection
p<0.05 (AOR 3.19, 95% CI 1.48 to 6.85), having more than
11 sexual partners in the last 6 months p=0.04 (AOR 2.91,
95% CI 1.04 to 8.09) and having daily intercourse p=0.05
(AOR 3.15, 95% CI 1.02 to 9.74).
Conclusions The prevalence of CT and NG was higher
than that reported in the general population. Additionally,
females had a higher percentage of infection compared
with males.
INTRODUCTION
Sexually transmitted infections (STIs) have
proven to be a global public health problem,
as they are one of the most common acute
conditions that affect populations around the
world. Moreover, they are known to afflict
people of any socio- economic level, age, and
sex who have had contact with an infected
person’s fluids via unprotected intercourse,
blood transfusions or vertical transmission.1
In that matter, Chlamydia trachomatis (CT)
and Neisseria gonorrhoeae (NG) are the second
and third causes of STIs in the world, with an
estimated prevalence of 4.2% in women and
2.7% in men for CT1 and 0.9% in women and
0.7% in men for NG.2 CT is asymptomatic
in 70% of women and 50% of men, and it is
responsible in many cases for pelvic inflam-
matory disease, ectopic pregnancy, endome-
tritis and infertility. NG infection is highly
symptomatic in men, causing dysuria and
purulent discharge, epididymitis, prostatitis
and infertility.3
Regarding Latin America, STIs caused by
CT and NG have proven to be a serious public
health problem, given the lack of resources
in different clinical settings for diagnosis and
treatment, and the scarce epidemiological
research in this region. All of this combined
with the high prevalence of both diseases (CT
Strengths and limitations of this study
►This research uses molecular techniques (qPCR) to
evaluate urine samples to establish the prevalence
of Chlamydia trachomatis (CT) and Neisseria gon-
orrhoeae (NG) in homeless populations of Medellín,
Colombia.
►Risk factors associated with infection from CT and
NG bacteria were established, and a demographic
prole was developed with dynamics of social and
sexual interaction.
►This is the rst study that has used a sample of 500
homeless individuals in order to determine the prev-
alence of NG and CT in Colombia.
►Every piece of data regarding sociodemograph-
ic proles and sexual behaviours was collected
through a primary source.
►The main limitation was that the recruitment of the
sample was carried out solely in homeless shelters
of Medellín by the mayor’s ofce, accommodations
that cover roughly 70% of the target population.
2Vélez- GómezDE, etal. BMJ Open 2022;12:e054966. doi:10.1136/bmjopen-2021-054966
Open access
infection prevalence is 7.6% in women and 1.8% in men,
and NG infection prevalence is 0.8% in women and 0.7%
in men).1
Moreover, CT is a big concern in Colombia, since
it is the most reported STI in the country, with a prev-
alence of 2% in asymptomatic people and 7% to 9.8%
in the general population with lower genital tract symp-
toms. Meanwhile, even though NG prevalence is lower
(1.5% to 3%), chlamydial coinfection with NG has been
reported in 10%–40% of NG infection cases, and it has
been showing increased antibiotic resistance.4 However,
since these infections are not notifiable diseases, there is
little data on the prevalence of these infections stratified
in high- risk populations in Latin America, such as home-
less persons.5
A homeless person is defined as someone whose life
takes place mainly on the street, as a physicalsocial space,
where they solve their vital needs, builds affective rela-
tionships and sociocultural mediations, structuring a life-
style.6 The last census of homeless persons in Medellín,
Colombia, was carried out in 2019 by the National Admin-
istrative Department of Statistics where 3214 people were
reported to live in this situation of which 14.8% were
women and 85.2% were men.7
Additionally, the homeless population is especially
vulnerable to STIs, as their prevalence reaches up to
52.5%.8 This is due to various known high- risk behaviours
that are common in this community (unprotected sexual
intercourse, multiple sexual partners, sex work and the
use of psychoactive substances while engaging in inter-
course.8–11 Currently, there is no in- depth research
regarding CT and NG in the homeless population of
Colombia. Therefore, this study aimed to determine the
prevalence of CT and NG in this community in Medellín,
Colombia, using molecular diagnostic methods. It also
intended to develop a demographic profile exploring
associated factors and the dynamics of the social and
sexual interactions of this community.
MATERIALS AND METHODS
This is a cross- sectional quantitative study, which primarily
used information from a survey of a homeless population
between 15 and 88 years of age, who attended different
institutions of the mayor’s office in Medellín, Colombia.
It also used laboratory testing in urine samples provided
by the study subjects to detect CT and NG.
Sampling methods and recruitment
The sample size was calculated using the finite popula-
tion method,12 and the Centers for Disease Control and
Prevention software, Epi info. This was performed using
information from the census of homeless persons living
Medellín in 2010,13 considering a total homeless popu-
lation of 3381 persons. The sampling error was set at 5%
and the CI was set at 97%. The result of this calculation
was n=413, but it was rounded up to 500.
The information in this study was gathered from
November 2017 to May 2019 in the Medellín homeless
care centres, which are frequented by about 1836 persons
each day,7 from which participants were randomly
selected. In order to ensure unbiased randomisation,
we used the systematic sampling method, in which the
sampling interval was one selected case every seven
persons, with weekly visits over the span of 18 months.
The sample interval was calculated by dividing the total
homeless population in Medellín (N=3381),13 by the
calculated sample size (n=500).
The criteria for eligible participants were: (1) having
ever engaged in sexual activity and (2) being a homeless
individual. They signed an informed consent form; those
under 18 years of age signed an assent form and were
accompanied by the family defender from the institu-
tions where they were being cared for. The subjects were
excluded from the study if they had visible clinical signs
of inebriation or an altered mental state.
Data collection
A structured electronic survey was administered to
each participant by a member of the research team. It
contained 89 questions pertaining to sociodemographics,
sexual behaviours, previous STI infection and treatment,
consumption of psychoactive substances, educational
aspects and general knowledge of sexual health and STIs.
This survey aimed to identify different risk factors and to
establish the population profile. The questions can be
found in online supplemental material 1.
Sample collection
Urine samples were obtained by self- collection. The first
day that the patients were recruited, they received instruc-
tions and 30 mL sample bottles to collect the first urina-
tion of the next day or after 4 hour retention. The staff
of the homeless care centres were aware of the patient’s
participation in the study and made sure that the patients
did not forget the instructions and ensured a correct
urine sample collection. The staff also refrigerated the
samples, which were then shipped by the researchers
early that same morning to the laboratory that is located
less than 2 km away from the centre (<5 min by car).
Laboratory testing
In the laboratory, each sample was tested for CT and NG
infection. The urine was processed for DNA extraction,
using the commercial QIAamp Viral RNA Mini Hand-
book (Qiagen, Germany). Nested PCR was performed to
detect the cryptic plasmid and the MOMP gene from CT.
This procedure was also used to detect the porin protein
gene (por) and transferrin binding protein β subunit
gene from NG. Each PCR run was performed using posi-
tive and negative controls. PCR was considered positive
when at least one of the amplicons was detected. In nega-
tive cases, qPCR was performed with the same primers,
using the Luna Universal qPCR Mix kit (New England
Biolabs, Ipswich, Massachusetts, USA).
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Vélez- GómezDE, etal. BMJ Open 2022;12:e054966. doi:10.1136/bmjopen-2021-054966
Open access
Table 1 Characteristics of all participants
Variables n (%)
Sex
Male 352 (70.4)
Female 148 (29.6)
Age
13–22 50 (10.0)
23–32 162 (32.4)
33–42 146 (29.2)
43–52 75 (15.0)
53–62 59 (11.8)
63–72 7 (1.4)
>73 1 (0.2)
Gender identity
Heterosexual 422 (84.4)
Lesbian 16 (3.2)
Gay 9 (1.8)
Bisexual 43 (8.6)
Transgender 10 (2.0)
Birthplace
Medellín 279 (55.8)
Other 221 (44.2)
Marital status
Single 341 (68.2)
Civil union 94 (18.8)
Married 25 (5.0)
Other 40 (8.0)
Highest educational level (grades)
No education 33 (6.6)
Basic primary (1–5) 177 (35.4)
Basic Secondary (6–9) 158 (31.6)
Secondary (10–11) 100 (20.0)
Technical/technological level 21 (4.2)
Bachelor’s degree 10 (2.0)
Master’s degree 1 (0.2)
Children, n
None 197 (39.4)
<3 208 (41.6)
3–4 64 (12.8)
>4 31 (6.2)
Source of income*
Street sales 217 (43.4)
Recycling 126 (25.2)
Panhandling 114 (22.8)
Running errands 78 (15.6)
Sex work 54 (10.8)
Selling drugs 54 (10.8)
Continued
Variables n (%)
Assistance from family or friends 46 (9.2)
Government assistance 11 (2.2)
Other 38 (7.6)
Daily psychoactive substance consumption*
Tobacco 300 (60.0)
Marijuana 234 (46.8)
Cocaine/cocaine derivatives 312 (62.4)
Alcohol 122 (25.6)
Pills (unspecied) 57 (11.4)
Inhalant abuse 55 (11.0)
MDMA (ecstasy, molly)† 11 (2.2)
Other substances 42 (8.4)
No daily consumption 48 (9.6)
Sexual partners in lifetime
No Answer 20 (4.0)
<50 381 (76.2)
50–100 45 (9.0)
>100 54 (10.8)
Sexual partners in the last 6 months
No answer 22 (4.4)
<11 426 (85.2)
11–50 35 (7.0)
>50 17 (3.4)
Age of rst sexual activity
No answer 5 (1.0)
<10 58 (11.6)
10–14 253 (50.6)
>14 184 (36.8)
Use of contraception*
Females
Condoms 56 (37.8)
Tubal ligation 55 (37.2)
Implants 42 (28.4)
Injections 8 (5.4)
Pills 4 (2.7)
Others 2 (1.4)
None 28 (18.9)
Males
Condoms 260 (73.9)
None 92 (26.1)
Condom use in the last 3 months*
Yes 204 (40.8)
No 296 (59.2)
Committed partner* 173 (58.4)
Casual partner(s)* 203 (68.6)
Table 1 Continued
Continued
4Vélez- GómezDE, etal. BMJ Open 2022;12:e054966. doi:10.1136/bmjopen-2021-054966
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The molecular sensitivity of both PCRs was established
with logarithmic dilutions from 10 ng/µL to 1.0 fg/µL of
the cloned CT and NG DNA fragment and was defined as
the minimum DNA concentration detected by the nested
PCR. Analytical specificity was defined as the ability of
the different CT and NG primers to exclusively identify
the gene from the microorganism of interest with 100%
identity and was determined in silico using the National
Center for Biotechnology Information database.14
Statistical analyses
The data obtained in the questionnaire as well as the
results of the qPCR for each participant were transferred
to the statistical package SPSS version 24 (licensed by the
University of Antioquia—Colombia).
First, a general descriptive analysis was carried out, then
the polytomous variables were recategorised, and a bivar-
iate analysis was performed, in order to calculate the asso-
ciation between variables with χ2, contemplating a p<0.05
as a statistically significant association. The OR was calcu-
lated with 95% CIs for both CT and NG infections.
Finally, to calculate the adjusted OR (AOR), a binary
logistic regression model was carried out, using the vari-
ables that previously had a p<0.05 in the bivariate analysis.
Patient and public involvement
Informative sessions were held in the homeless care
centres of the mayor’s office in Medellín, Colombia, to
present the problem, raise awareness among the popu-
lation, and explain the objectives of the study. Patients
were not compensated monetarily for their participation
in the study, but they were given their PCR results free of
charge and were also directed to governmental health-
care programmes that prescribed medicine and provided
their infections at no cost. Additionally, symptomatic
and clinical follow- up after treatment was performed by
a medical doctor of the institution for every subject in
order to ensure the eradication of the infection.
RESULTS
Study population characteristics
Between November 2017 and May 2019, 500 individuals
that met the inclusion criteria completed the survey
conducted by a professional and provided urine samples
for the detection of CT and NG. The characteristics of all
subjects are shown in table 1.
Additionally, 41.9% of the females and 38.9% of the
males surveyed reported having an STI during their life-
time (p=0.535). Of these past self- reported STIs, gonor-
rhoea was the most common among men (23.3%), and
syphilis among women (33.8%). Furthermore, 37.9%
of heterosexuals, 55.8% of bisexuals, 33.3% of gay men,
37.5% of lesbians and 60% of transgender persons
reported having a past STI in their lifetime. Among the
latter group, 50% reported past syphilis infections.
Sex work was performed by 24.3% of women and 5.1%
of men (p<0.001). A statistically significant difference
was also observed between sexual orientation and sex
work (p<0.001), finding that it was performed by 5.7%
of the heterosexual population, 6.3% of lesbian, 44.4%
of gay men, 34.9% of the bisexual population and 100%
of transgender people. In addition, 25.9% of those who
performed sex work reported an STI in their lifetime. It
was found that 13.1% of men and 0.7% of women paid for
sexual services (p<0.001).
Prevalence of CT and NG by qPCR
The diagnosis of CT and NG was done by qPCR (figure 1).
The results show a 22.6% prevalence of NG infection
(n=113), and a 19.2% prevalence of CT infection (n=96)
Variables n (%)
Consent in past sexual encounters
Females
Non- consensual 64 (43.2)
Consensual 67 (45.3)
No answer 17 (11.5)
Males
Non- consensual 41 (11.6)
Consensual 284 (80.7)
No answer 27 (7.7)
Frequency of intercourse
No answer 44 (8.8)
Daily 37 (7.4)
2–3 times a week 115 (23.0)
2–3 times a month 187 (37.4)
At least once in the last 3 months 73 (14.6)
At least once in the last 6 months 44 (8.8)
*Survey respondents could choose more than one option.
†Methylenedioxymethamphetamine (MDMA), commonly known as
ecstasy or molly.
Table 1 Continued
Figure 1 Prevalence of gonorrhoea and chlamydia
infections by gender.
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Vélez- GómezDE, etal. BMJ Open 2022;12:e054966. doi:10.1136/bmjopen-2021-054966
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Table 2 Factors associated with Chlamydia trachomatis infection—OR
Variable
C. trachomatis qPCR test
Unadjusted OR
(95% CI)
P value
χ2
Positive Negative
n % n %
Sex
Female 45 46.9 103 25.5 2.58 (1.63 to 4.08) <0.001
Male 51 53.1 301 74.5
Children
Yes 71 74 232 57.4 2.11 (1.28 to 3.46) 0.003
No 25 26 172 42.6
Has been taught how to use a condom
No 20 20.8 44 10.9 2.15 (1.2 to 3.86) 0.009
Yes 76 79.2 360 89.1
Consumption of glue/inhalant during intercourse
Yes 13 13.5 25 6.2 2.37 (1.17 to 4.84) 0.015
No 83 86.5 379 93.8
MDMA (ecstasy, molly) consumption during intercourse*
Yes 10 10.4 18 4.5 2.49 (1.11 to 5.59) 0.022
No 86 89.6 386 95.5
Consumption of cocaine during intercourse
Yes 6 6.3 8 2 3.30 (1.12 to 9.75) 0.023
No 90 93.8 396 98
Frequent irritation or discomfort symptoms
Yes 9 9.4 16 4 2.51 (1.07 to 5.86) 0.029
No 87 90.6 388 96
Condom use with casual partner
No 41 62.1 128 47.9 1.18 (1.03 to 3.09) 0.039
Yes 25 37.9 139 52.1
Domestic violence
Yes 29 35.4 91 24.3 1.70 (1.02 to 2.84) 0.040
No 53 64.6 283 75.7
Number of sexual partners in lifetime
>100 16 17.2 38 9.8 1.91 (1.01 to 3.6) 0.043
<100 77 82.8 349 90.2
Urethral discharge
Yes 6 11.8 15 5 2.54 (0.94 to 6.89) 0.059
No 45 88.2 286 95
Consent in past sexual encounters
Non- consensual 25 30.5 80 21.4 1.61 (0.95 to 2.74) 0.076
Consensual 57 69.5 294 78.6
Sleeping in a homeless care centre
Yes 84 87.5 322 79.7 1.78 (0.93 to 3.42) 0.079
No 12 12.5 82 20.3
Heroin consumption
Yes 9 9.4 19 4.7 2.10 (0.92 to 4.79) 0.074
No 87 90.6 385 95.3
Sexual partners in the last 6 months
>50 6 6.6 11 2.8 2.41 (0.87 to 6.71) 0.082
<50 85 93.4 376 97.2
Continued
6Vélez- GómezDE, etal. BMJ Open 2022;12:e054966. doi:10.1136/bmjopen-2021-054966
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for the general population. Moreover, infection caused
by a single agent was 14.6% (n=73) for CT and 18.0%
(n=90) for NG. Coinfection occurred in 4.6% (n=23).
In males, the prevalence of CT and NG was 14.5% and
21.3% respectively, while in females it was 30.4% for CT
and 25.7% for NG. A statistically significant difference
in CT prevalence was found between men and women
(p≤0.001). On the contrary, for NG, this difference was
not significant (p=0.286).
Factors associated with CT and/or NG infection
Table 2 shows the results of different factors associated
with CT infection. It is observed that the consumption
of MDMA (ecstasy), toluene inhalants and cocaine while
having sex increases the chances of infection 2.37, 2.49
and 3.30 times, respectively (p<0.05), in contrast with the
people who did not consume these substances during
intercourse.
Table 3 shows the results of different factors associ-
ated with an NG infection. Among the most relevant, it
is observed that transgender people are 5.37 times more
likely to contract the infection than the rest of the popula-
tion, with a statistically significant difference (p=0.004). A
binary logistic regression model was performed to adjust
the OR of CT infection with the potential associated
factors. Table 4 shows that being a woman significantly
increased the chances of infection (AOR=2.42, 95% CI
1.31 to 4.47), (p=0.00).
For NG, a binary logistic regression model was also
performed (table 4), finding that having intercourse
while having an STI confers 3.19 times more chances
of having an NG infection than those who avoid them.
Another associated factor was having more than 11 sexual
partners during the last 6 months (AOR 2.91, 95% CI 1.04
to 8.09), (p=0.04) and having daily intercourse (AOR
3.15, 95% CI 1.02 to 9.74), (p=0.05).
DISCUSSION
In this cross- sectional study, we determined the prev-
alence of CT and NG in the homeless population of
Medellín, Colombia using molecular diagnostic methods.
We also developed a demographic profile exploring asso-
ciated factors and the dynamics of the social and sexual
interactions of the population. This study identified that
approximately one in five homeless individuals residing
in Medellín, Colombia was infected with CT or NG. It also
found that females had approximately double the preva-
lence of infection by CT compared with males.
The prevalence found for NG and CT in the study
population was 22.6% and 19.2%, respectively; being
higher than that reported in the general population (♀
CT: 4.2%, NG: 0.8%; ♂ CT: 2.7%, NG: 0.6%).1 Also, in
the present research, the coinfection between CT and
NG was 4.6%, which was higher compared with other
papers, where the coinfection prevalence varied from
1.7% in juvenile detention centres in the USA15 to 2.9%
in sex workers.16 All of this can be explained due to the
fact that, unlike other studies, the researched sample
was composed exclusively by homeless persons. This
population presents multiple and simultaneous high- risk
behaviours8–11 17 such as sex work, the lack of condom use,
intercourse while consuming psychoactive substances,
ignorance about STIs and multiple sexual partners. Also,
another study performed in the USA, found a lower prev-
alence on both CT (6.4%–6.7%) and NG 0.3%–3.2% in
homeless persons.8 This is due to the difference both
in the quality of education in STI prevention and the
government’s social assistance programmes focusing on
preventive healthcare between Colombia (a low/middle-
income country) and other highly developed nations.18
The prevalence of CT and NG infection was higher
in women (CT: 30.4% in women and 14.5% in men;
Variable
C. trachomatis qPCR test
Unadjusted OR
(95% CI)
P value
χ2
Positive Negative
n % n %
Condom use
No 39 40.6 145 35.9 1.22 (0.78 to 1.93) 0.387
Yes 57 59.4 259 64.1
Has had Syphilis in their lifetime
Yes 24 25 83 20.5 1.29 (0.77 to 2.17) 0.339
No 72 75 321 79.5
Sex work
Yes 12 12.5 42 10.4 1.23 (0.62 to 2.44) 0.550
No 84 87.5 362 89.6
Cannabis consumption
Yes 60 62.5 294 72.8 0.62 (0.39 to 1.00) 0.047
No 36 37.5 110 27.2
*Methylenedioxymethamphetamine (MDMA), commonly known as ecstasy or molly.
Table 2 Continued
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Table 3 Factors associated with Neisseria gonorrhoeae infection—OR
Variable
Neisseria gonorrhoeae qPCR test Unadjusted
OR
(95% CI)
P value
χ2
Positive Negative
N % N %
Gender identity
Transgender 6 5.3 4 1 5.37 (1.49 to 19.37) 0.00
Non- transgender people 107 94.7 383 99
Last Pap Smear test
>1 year ago 30 81.1 64 61.5 2.68 (1.08 to 6.67) 0.03
<1 year ago 7 18.9 40 38.5
Place for personal hygiene
Public place 107 94.7 341 88.1 2.41 (1.00 to 5.79) 0.04
House, apartment 6 5.3 46 11.9
Had sexual contact while having an STI
Yes 24 57.1 57 36.3 2.34 (1.17 to 4.67) 0.02
No 18 42.9 100 63.7
Frequency of intercourse
Daily 15 13.3 22 6.4 2.23 (1.12 to 4.47) 0.02
Once a week or less 98 86.7 321 93.6
Sexual partners in the last 6 months
>11 partners 19 17.3 33 9 2.12 (1.15 to 3.90) 0.01
<10 partners 91 82.7 335 91
HIV
Positive 6 5.3 10 2.6 2.11 (0.75 to 5.95) 0.09
Negative 107 94.7 377 97.4
Type of sexual intercourse (last time)
Oral and/or anal 17 15 31 8 2.03 (1.08 to 3.83) 0.03
Vaginal 96 85 356 92
Sleeping in a homeless care centre
Yes 99 87.6 307 79.3 1.84 (1.00 to 3.40) 0.05
No 14 12.4 80 20.7
Number of sexual partners in lifetime
>100 18 16.1 36 9.8 1.77 (0.96 to 3.25) 0.07
<100 94 83.9 332 90.2
Sex work
Yes 17 15 37 9.6 1.68 (0.90 to 3.11) 0.10
No 96 85 350 90.4
Last sexual contact
Commercial sex 27 23.9 66 17.1 1.53 (0.92 to 2.54) 0.10
Stable or casual 86 76.1 321 82.9
Domestic violence
Yes 35 31 85 24.8 1.36 (0.85 to 2.18) 0.20
No 78 69 258 75.2
Sex
Female 38 33.6 110 28.4 1.28 (0.82 to 2.00) 0.29
Male 75 66.4 277 71.6
STI, sexually transmitted infection.
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NG 25.7% in women and 21.3% in men). This is consis-
tent with the results reported by the WHO and other
researchers.1 19 20 Similar studies confirm that the CT
prevalence between women and men presents significant
differences, where it was reported in 31.7% of women
and 9.2% of men.21 The higher prevalence in women is
likely due to the predominance of asymptomatic infec-
tions which leads to an alarming rate of subdiagnosis,
subsequently leaving a lot of untreated and chronic cases
among females compared with males.22 On the other
hand, infection by CT in males is more evident, as it is
symptomatic to a greater extent (mainly dysuria, urethral
discharge and testicular pain).23 Therefore, it is possible
that a broader number of infected males had previously
sought medical attention for genital irritative symp-
toms, which were then treated somewhat successfully.
Regarding NG, there is a differential gene expression
between men and women during the infection process, as
well as differences in the pathogenic mechanisms used by
this bacterium to infect the male and female epithelium,
which define the evolution of the infection and the host’s
presentation of symptoms.24 25
Regarding the demographic profile, some variables
such as substance use, income source and the distribution
by age groups and sex, behaved similarly in this study and
in Colombia’s census of homeless persons performed in
2019.7 This study observed that the sample was predom-
inantly composed of males (70.4%), and these results
are comparable to those previously reported locally26 27
and in other countries such as the USA (66.4% homeless
males)8 and Spain (90% homeless males).28
Furthermore, several studies determined risk factors
associated with STIs, such as domestic violence, use
of psychoactive substances, a history of incarceration,
multiple sexual partners, non- use of condoms, lack of
education about STIs, feelings of affection towards the
partner and not prioritising the well- being of their own
or others.8 10 11 Correspondingly, in this study, we found
that 59.2% of the individuals indicated that they did not
use a condom in the 3 months prior to the survey, which
was encountered more frequently when people had inter-
course with a committed partner. This can be explained
because according to the participants, there was trust or
affection with their partner.
Another significant finding in this study was that meth-
ylenedioxymethamphetamine (MDMA) and cocaine use
was significantly associated with CT infection (p=0.02).
This can be attributed to the fact that being under the
influence of psychoactive substances can lead homeless
persons to engage in risky sexual behaviours.29 Addition-
ally, the most frequent STIs in the survey of this study were
syphilis (21.4%), gonorrhoea (19.4%) and HIV (3.2%).
Similar results were found both by national11 27 and inter-
national8 30 31 studies performed in homeless populations.
This research had limitations related to the recruit-
ment of the sample. This was mainly because the appli-
cation of surveys and collection of urine samples was
carried out solely in homeless shelters of Medellín by the
mayor’s office, accommodations that cover roughly 70%
of the target population, according to the 2019 Census.7
This was necessary because of the low- security conditions
in other areas of the city where homeless persons reside.
Finally, it is imperative that governmental entities and
policy- makers implement epidemiological surveillance
programmes performing molecular techniques in non-
invasive samples to improve the diagnosis of STIs in
populations at risk, such as homeless persons. Addition-
ally, future research should focus both on implementing
molecular techniques in the detection of STIs and devel-
oping an ample sociodemographic profile, which allows
the researcher to explore the risk factors more in depth.
Also, future investigations should perform stratified
analyses both in the general population and in high- risk
groups, to have a broader view of the health situation and
consequently implement more focused social assistance
programmes that tackle these sexual health issues directly.
Acknowledgements To the Corporation for Biological Research (CIB), especially
Dr. Óscar Gómez, to the Secretaría de Inclusión Social, Familia y Derechos Humanos
of the mayor’s ofce of Medellín—Colombia and its institutions 'Centro de
Diagnóstico y Derivación' and 'Centro Día', to Dr. Lucas Arias Vélez, leader of the
'Programa de atención al habitante de calle', to the religious community 'Carmelitas
Misioneras' and the ASPERLA ONG, for their support and accompaniment in the
development of this work. To the international advisor, Dr. John Wylie—University of
Table 4 Factors associated with Chlamydia trachomatis and Neisseria gonorrhoeae infection—Adjusted OR
Bacteria Risk factor B
P value
Wald
Adjusted OR
(95% CI)
N. gonorrhoeae Sexual intercourse while having an STI 1.16 0.00 3.19 (1.48 to 6.85)
>11 sexual partners in the last 6 months 1.07 0.04 2.91 (1.04 to 8.09)
Daily sexual relations 1.15 0.05 3.15 (1.02 to 9.74)
C. trachomatis Being a woman 0.88 0.00 2.42 (1.31 to 4.47)
No condom use with casual partners 0.44 0.13 1.56 (0.87 to 2.77)
Children 0.42 0.17 1.52 (0.83 to 2.78)
>100 sexual partners in lifetime 0.42 0.26 1.52 (0.73 to 3.14)
STI, sexually transmitted infection.
9
Vélez- GómezDE, etal. BMJ Open 2022;12:e054966. doi:10.1136/bmjopen-2021-054966
Open access
Manitoba—Canada. We would also like to thank Mr. Cameron Hahn for consulting
the translation of the manuscript.
Contributors DEV- G: guarantor, data collection, statistical data analysis,
methodology design, database management, manuscript writing. NT- V: data
collection, data analysis, manuscript writing. JCG- Z: data collection, laboratory
tests, methodology design, manuscript writing. JGM- O: conceptualisation,
methodology design, laboratory tests, manuscript writing. AM: conceptualisation,
methodology design, project supervision, manuscript writing. VR- L: data collection,
data analysis, manuscript writing. AV- C: conceptualisation, funds and resources
management, methodology design, project administration and supervision, and
manuscript writing.
Funding This work was supported by MINCIENCIAS (Ministerio de Ciencia,
Tecnología e Innovación—Colombia) and the University of Antioquia—Colombia.
Grant number: 111574455752.
Competing interests None declared.
Patient consent for publication Consent obtained directly from patient(s)
Ethics approval The consent, informed assent and survey were previously
approved by the Bioethics Committee of the Faculty of Medicine of the University
of Antioquia—Colombia (Ethics approval number: 2017- 022). This study was
endorsed by the 'Secretaría de Inclusión Social, Familia y Derechos Humanos' of
the mayor’s ofce of Medellín—Colombia. Participants gave informed consent to
participate in the study before taking part.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available on reasonable request. Raw data,
the database and the survey without any identiers are available on reasonable
request, emailing diegovelezgomez@ gmail. com (corresponding author).
Supplemental material This content has been supplied by the author(s). It has
not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been
peer- reviewed. Any opinions or recommendations discussed are solely those
of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and
responsibility arising from any reliance placed on the content. Where the content
includes any translated material, BMJ does not warrant the accuracy and reliability
of the translations (including but not limited to local regulations, clinical guidelines,
terminology, drug names and drug dosages), and is not responsible for any error
and/or omissions arising from translation and adaptation or otherwise.
Open access This is an open access article distributed in accordance with the
Creative Commons Attribution Non Commercial (CC BY- NC 4.0) license, which
permits others to distribute, remix, adapt, build upon this work non- commercially,
and license their derivative works on different terms, provided the original work is
properly cited, appropriate credit is given, any changes made indicated, and the use
is non- commercial. See:http://creativecommons.org/licenses/by-nc/4.0/.
ORCID iDs
Diego EnriqueVélez- Gómez http://orcid.org/0000-0002-6095-3706
NataliaTorres- Vellojín http://orcid.org/0000-0001-9272-1152
Juan CamiloGrajales- Zapata http://orcid.org/0000-0002-1365-2249
Juan GuillermoMcEwen- Ochoa http://orcid.org/0000-0001-8594-9087
AlonsoMartínez http://orcid.org/0000-0003-3619-6087
VerónicaRamírez- Lopera http://orcid.org/0000-0002-3609-8025
AracellyVillegas- Castaño http://orcid.org/0000-0001-7716-8184
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