Bacterial etiology of bloodstream infections and antimicrobial resistance in Dhaka, Bangladesh, 2005–2014
Ahmed et al. Antimicrobial Resistance and Infection Control
Bacterial etiology of bloodstream infections and antimicrobial resistance in Dhaka, Bangladesh, 2005-2014
Dilruba Ahmed 0
Md Ausrafuggaman Nahid 0
Abdullah Bashar Sami 0
Farhana Halim 0
Nasrin Akter 0
Tuhin Sadique 0
Md Sohel Rana 0
Md Shahriar Bin Elahi 0
Md Mahbubur Rahman 0
0 International Centre for Diarrhoeal Disease Research , Bangladesh (icddr,b), Dhaka 1212 , Bangladesh
Background: Bloodstream infections due to bacterial pathogens are a major cause of morbidity and mortality in Bangladesh and other developing countries. In these countries, most patients are treated empirically based on their clinical symptoms. Therefore, up to date etiological data for major pathogens causing bloodstream infections may play a positive role in better healthcare management. The aim of this study was to identify the bacterial pathogens causing major bloodstream infections in Dhaka, Bangladesh and determine their antibiotic susceptibility pattern. Methods: From January 2005 to December 2014, a total of 103,679 single bottle blood samples were collected from both hospitalized and domiciliary patients attending Dhaka hospital, icddrb, Bangladesh All the blood samples were processed for culture using a BACT/Alert blood culture machine. Further identification of bacterial pathogens and their antimicrobial susceptibility test were performed using standard microbiological procedures. Results: Overall, 13.6% of the cultured blood samples were positive and Gram-negative (72.1%) bacteria were predominant throughout the study period. Salmonella Typhi was the most frequently isolated organism (36.9% of samples) in this study and a high percentage of those strains were multidrug-resistant (MDR). However, a decreasing trend in the S. Typhi isolation rate was observed and, noticeably, the percentage of MDR S. Typhi isolated declined sharply over the study period. An overall increase in the presence of Gram-positive bacteria was observed, but most significantly we observed the percentage of MDR Gram-positive bacteria to double over the study period. Overall, Gram positive bacteria were more resistant to most of the commonly used antibiotics than Gram-negative bacteria, but the MDR level was high in both groups. Conclusions: This study identified the major bacterial pathogens involved with BSI in Dhaka, Bangladesh and also revealed their antibiotic susceptibility patterns. We expect our findings to help healthcare professionals to make informed decisions and provide better care for their patients. Also, we hope this study will assist researchers and policy makers to prioritize their research options to face the future challenges of infectious diseases.
Bloodstream infection; BSI; Antimicrobial resistance; Multidrug-resistance (MDR); Epidemiology; Gram-positive bacteria; Gram-negative bacteria; Dhaka; Bangladesh
Bloodstream infection (BSI) due to bacterial pathogens
is a global concern. It is often associated with increased
length of hospital stay, a significant amount of
healthcare related costs and most significantly, a high rate of
morbidity and mortality . Depending on the age,
severity of infection and other risk factors, the mortality
rate for BSI varies between 4.0 and 41.5% [2–7]. Recent
studies have reported a rapid increase in the number of
bloodstream infections from both community and
nosocomial sources [8, 9]. Staphylococcus aureus, Streptococcus
pneumoniae and Escherichia coli have been found to be
the most commonly isolated pathogens associated with
BSI worldwide [3, 6].
The epidemiology of BSI varies depending on the
geographic location, age and co-morbid illnesses. As an
example, Salmonella enterica is a frequently isolated
pathogen from blood samples in both African and Asian
regions, however their serotypes differ substantially . S.
Paratyphi is the predominant organism in the Salmonella
group in Africa whereas S. Typhi is the most frequently
isolated organism in Asia. Besides their isolation rate, their
antibiotic susceptibility pattern varies substantially . So,
understanding of local epidemiology may play an
important role in making proper empirical treatment choices
before laboratory test results are available. This is especially
true for Bangladesh and other developing countries where
healthcare systems operate on poor hygiene system and
lack proper facilities to contain infections. In these
countries, early treatment is usually based on the patient’s
clinical symptoms rather than diagnostic results. Therefore,
patient’s early prognosis to final outcome might be much
improved by available epidemiologic data for the most
frequently isolated pathogenic organisms. However,
complete data on BSI causing organisms from Dhaka,
Bangladesh is scarce.
In this study, we aimed to identify the most prevalent
bacterial pathogens involved in BSI in hospital and
domiciliary patients from Dhaka, Bangladesh. We also
determined pathogen antibiotic susceptibility patterns to
evaluate the changing trend of antimicrobial
susceptibility in this region.
In this retrospective study, blood samples were obtained
from patients attending out-patient and in-patient
services at Dhaka hospital, icddrb, Bangladesh which is a
primary care hospital with 200 in-patient beds. A total
of 103679 blood samples were processed from January
2005 to December 2014. In the consecutive ten years of
the study 9600, 9364, 9189, 9523, 9523, 11578, 11179,
10822, 10161 and 12740 samples were received and
processed from 2005 to 2014 respectively. All the blood
samples were processed for culture using a BACT/Alert
blood culture machine to identify the presence of
bacterial pathogens. Antimicrobial susceptibility tests were
performed on the isolated pathogens using standard
microbiological procedures .
Collected blood samples were directly inoculated into
adult (more than 12 years of age) and pediatric (up to
12 years of age) FAN blood culture bottle. Bottles were
incubated in the BACT/Alert machine for up to 5 days.
Positive culture samples were directly inoculated onto
MacConkey (MC) agar, chocolate agar and blood agar
(5% sheep blood) plates. MC plates were then incubated
at 35 °C in aerobic condition. Chocolate and blood agar
plates were incubated at 35 °C in microaerophilic
condition (containing 5% CO2). Bacterial pathogens were
identified using standard bacteriological procedures .
API identification strips (bioMérieux, France) were used
as supportive tests for further identification.
Antimicrobial susceptibility testing
Antimicrobial susceptibility tests were performed by
using the disk diffusion method and susceptibility
patterns were determined following CLSI guidelines
[11–14]. The study was begun following CLSI, 2004
guidelines  and later the relevant changes made in
2010, 2012 and 2013 by CLSI were incorporated.
Breakpoint changes made in 2010 and 2013 for carbapenems
in the case of Enterobacteriaceae [12, 13] were adapted,
and also the revised ciprofloxacin breakpoint for
Salmonella in 2012 . Antibiotic susceptibility was
tested for CN (10 μg), SXT (25 μg), Cip (5 μg), CRO
(30 μg), AMP (10 μg), Caz (30 μg), Imp (10 μg), Net
(30 μg), Ak (30 μg), CFM (5 μg), Azi (15 μg), Pen G
(10 μg), E (15 μg), C (30 μg), Van (30 μg) and Tet (30 μg).
All the antibiotic disks were obtained from Oxoid, UK. E.
coli ATCC 25922 and Pseudomonas aeruginosa ATCC
27853 were used as quality control strains.
We were not able to find any standard definition of
multidrug-resistance (MDR) and observed that many
previous studies have used the definition of MDR as
resistance against three or more classes of antibiotics both
for Gram-positive [15–17] and Gram-negative [18–21]
bacteria. Consequently, the definition of MDR as
acquired non-susceptibility against at least three classes of
antibiotics was adopted. Salmonella species were tested
against six classes of antibiotics; penicillin and
cephalosporin (AMP, CRO, CFM), aminoglycosides (CN), fluor/
quinolones (Cip, NA), sulfonamides (SXT), macrolides
(Azi) and chloramphenicol. Other Gram-negative
bacteria were tested against seven classes of antibiotics;
penicillin and cephalosporin (AMP, CRO, CFM, Caz),
carbapenems (Imp, Mem), aminoglycosides (CN, Net,
Ak), fluoro/quinolones (Cip, NA), sulfonamides (SXT),
macrolides (Azi) and chloramphenicol. Gram-positive
bacteria were tested against seven classes of antibiotics;
penicillin and cephalosporin (AMP, Pen G, Oxa, CRO,
CFM), carbapenems (Imp), aminoglycosides (CN), fluor/
quinolones (Cip), sulfonamides (SXT), macrolides (Azi, E)
and others (C, Van, Rif ).
Blood-borne pathogen trends for isolation and
antimicrobial susceptibility over the last ten years was
determined using χ2 (chi-square) test for trend in SPSS
version 16.0. P value ≤ 0.05 was considered significant.
Standard error of the mean (SEM) was calculated for
mean isolation rates. Odd ratios for age and sex were
calculated to show their association with infection by
particular organisms, and SPSS version 16.0 was used
for this purpose. For age, an odds ratio greater than 1.0
indicated the association of a pathogen with age group
of less than five years old, and an odds ratio of less than
1.0 indicated the association of a pathogen with age
group of more than five years old. For sex, an odds ratio
of less than 1.0 indicated the association of a pathogen
with female patient group and an odds ratio of more
than 1.0 indicated an association of that pathogen with
male patient group.
From January 2005 to December 2014, a total of 103,679
blood samples were received from both hospitalized and
domiciliary patients and among them 14015 samples
were found to be culture positive. Over these past ten
years 11.9, 12.2, 13.9, 16.5, 16.0, 17.3, 12.7, 12.9, 10.7
and 11.9% of the samples were found to be culture
positive (P < 0.001) respectively. The mean culture positive
rate was 13.6 ± 0.7%. Table 1 shows the distribution of
organisms found throughout this study period. Blood
samples were received from patients with age range of
1 day to 115 years and the mean age was 18 years. S.
Typhi was the most frequently isolated blood-borne
bacterial pathogen in this study, accounting for 36.9% of the
total isolates. Other frequently isolated pathogens
included coagulase-negative Staphylococcus species (21.5%),
Pseudomonas species (12.5%), S. Paratyphi A, B (8.9%)
and Acinetobacter species (5.1%).
Pseudomonas species and Acinetobacter species were
the two major non-fermenter bacteria isolated between
2005 and 2014. Pseudomonas species showed a sharp
increase in isolation rate, from 40.6 to 79.2% (χ2 = 105.1,
P < 0.001) of the total non-fermenter bacteria, between
2005 and 2010. However, for the next four years their
isolation rate decreased slightly and reached 74.3% in
2014. Acinetobacter species showed a decreasing trend
in their isolation rate over this study period, from
49.8 to 24.4% (χ2 = 95.5, P < 0.001). Salmonella species
accounted for 46.7% of the total blood-borne pathogens.
We observed an overall decreasing trend in their isolation
rate from 2005 to 2014 (χ2 = 306.5, P < 0.001). Besides
nonfermenter and Salmonella species, other Gram-negative
bacteria constituted only 7.7% (χ2 = 72.0, P < 0.001) of the
total blood-borne pathogens. E. coli, Enterobacter species
and Serratia species had a steady isolation rate over the
ten year period, while Klebsiella species showed an
increasing trend in their isolation rate, from 22.6 to 50.9%
(χ2 = 29.1, P < 0.01) of the total Gram-negative bacterial
group (excluding Salmonella species). Gram-positive
bacteria accounted for 27.7% of the total blood-borne
pathogens. Their isolation rate increased from 20.6 to 30.8%
(χ2 = 351.7, P < 0.001) over study period. From 2005 to
2014, Streptococcus pneumoniae showed a decreasing trend
in their isolation rate, from 20.8 to 5.6% (χ2 = 158.7,
P < 0.001) of the total Gram-positive bacteria.
We observed significant associations between different
age groups and infection from specific pathogenic
organisms (Additional file 1: Table S7). Pseudomonas
species (OR: 0.383, 0.341- 0.430, P < 0.001), S. Paratyphi
A, B (0.510, 0.449-0.579, P < 0.001) and Serratia species
(0.592, 0.373-0.941, P < 0.05) had significant associations
with age group of more than five years old. On the other
hand, non-typhoidal Salmonella species (5.082,
3.1718.146, P < 0.001) and S. pneumoniae (3.827, 2.922-5.012,
P < 0.001) had significant association with age group of
less than five years old. We also observed the association
of sex with infection from different pathogenic bacteria
(Additional file 2: Table S8). S. aureus (1.348,
1.0191.783, P < 0.05) infection was significantly associated
with the male patient group, while E. coli (0.705,
0.5810.855, P < 0.001) was more associated with the female
patient group. Seasonal fluctuation was also observed in
the incidence rate of a few pathogens (Fig. 1).
Acinetobacter species (April-May), Enterobacter species (July), S.
aureus (March and November) and S. pneumoniae
(March) showed distinct seasonal peaks.
Acinetobacter species showed an increasing trend of
resistance against gentamicin (χ2 = 101.6, P < 0.001),
ceftriaxone (χ2 = 51.8, P < 0.001) and ciprofloxacin (χ2 = 135.2,
P < 0.001) (Additional file 3: Table S1). Pseudomonas
species also showed an increasing trend of resistance
against gentamicin (χ2 = 127.5, P < 0.001), and
ciprofloxacin (χ2 = 141.7, P < 0.001) (Additional file 4: Table S2).
Additionally, Acinetobacter species and Pseudomonas
species showed an overall 56.2, 47.6, 32.8, 51.4 and 23.0, 17.4,
56.2, 50.8% resistance against ceftazidime, imipenem,
netilmicin and amikacin respectively. Table 2 shows the
distribution of their MDR strains over this study period.
S. Typhi was found to be consistently sensitive to
ceftriaxone and cefixime over this study period; however, a
strain of ESBL S. Typhi was reported . At the same
time, decreasing trends of resistance against ampicillin
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(χ2 = 540.4, P < 0.001) and co-trimoxazole (χ2 = 740.3,
P < 0.001) were observed. S. Paratyphi A, B was found to
be consistently susceptible to ampicillin, co-trimoxazole,
ceftriaxone and cefixime over the ten year period.
Noticeably, both S. Typhi and S. Paratyphi A, B showed a trend
of increasingly reduced susceptibility against ciprofloxacin
(χ2 = 24.3 and 66.1 respectively, P < 0.001) throughout this
study period (Table 3).
E. coli and Enterobacter species showed an increasing
trend of resistance against gentamicin (χ2 = 52.44 and
statistically insignificant respectively, P < 0.001) and
ceftriaxone (χ2 = 52.4 and 16.5 respectively, P < 0.001). A
reducing trend of susceptibility against ciprofloxacin
(χ2 = 89.9 and 86.8 respectively, P < 0.001) was also
observed (Table 4 and Additional file 5: Table S4).
Additionally, E. coli showed an overall increase in resistance, from
69.0 to 90.0%, against co-trimoxazole and ampicillin
between 2005 and 2014. Klebsiella species showed an
increasing trend of resistance against imipenem (χ2 = 79.6,
P < 0.001), and a reducing trend of susceptibility
against ciprofloxacin (χ2 = 36.1, P < 0.001) (Additional
file 6: Table S3). Over the same time period an overall
increase in resistance, from 62.0 to 76.0%, was observed
against gentamicin and ceftriaxone respectively for
Klebsiella species. Additionally, Klebsiella species showed
an overall 86.0, 33.0 and 70.0% resistance against cefixime,
meropenem and azithromycin respectively from 2010
S. pneumoniae was found to be consistently
susceptible to ampicillin and ceftriaxone between 2005 and
2014 (Table 5). Over this period, their resistance to
cotrimoxazole reduced (χ2 = 92.5, P < 0.001). However, it
increased against penicillin G (χ2 = 195.3, P < 0.001) and
erythromycin (χ2 = 293.2, P < 0.001). Also, a trend of
increased susceptibility was observed against ciprofloxacin
(χ2 = 79.2, P < 0.001). Other Streptococcus species
showed an increasing trend of resistance against
gentamicin (χ2 = 44.9, P < 0.001) and erythromycin (χ2 = 70.0,
P < 0.001), while there was a reducing trend in
susceptibility against ciprofloxacin (χ2 = 67.3, P < 0.001)
(Additional file 7: Table S5). S. aureus was found to be
highly resistant to ampicillin (up to 100%) throughout
104 .(02193 .()02236 .()00 .()00 .()3292 .()6508 .()2192 .()7461 .()7262 .()8184 .()2706 .()00 .()3544 .()6393 .()514 .()034 .()325
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210 .(19064 .()20907 .)(00 .)(00 .()2210 .()4505 .()1191 .()9546 .()8619 .()2524 .()4442 .)(009 .()7278 .()2522 .)(031 .)(013 .)(631
2 1 1 0 0 5 3 2 7 3 2 1 9 2 1 3 9 3
110 .(21213 .()28083 .)(70 .)(00 .()1202 .()1843 .()5019 .()0057 .()2515 .()3459 .)(573 .)(175 .()0300 .()0654 .)(96 .)(672 .)(353
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2 2 2 0 0 1 3 6 9 3 4 1 5 3 1 4 1 6
2005 2006 2007 2008 2009 2010 2011 2012 2013 2014
(457)a (595) (571) (600) (483) (643) (451) (527) (354) (509)
AMP 61 62 54 50 41 41 42 24 28 26
Salmonella Paratyphi A, B
2005 2006 2007 2008 2009 2010 2011 2012 2013 2014
(85)a (133) (127) (146) (102) (179) (135) (129) (107) (110)
AMP 1 1 0 1 0 0 1 0 1 0
this study (Table 6). For this species, resistance against
erythromycin increased from 36.0% in 2005 to 75.0% in
2014 (P < 0.09) while susceptibility to ciprofloxacin
reduced (χ2 = 37.2, P < 0.001). S. aureus remained
consistently susceptible to vancomycin for the last five years of
the study and during the same time period they showed
an overall 42.0% resistance against ceftriaxone. E. faecalis
was found consistently susceptible to vancomycin between
2010 and 2014, while this species showed an overall 31.0,
45.0, 60.0, 39.0 and 81.0% resistance against ampicillin,
gentamicin (120), ciprofloxacin, penicillin G and
cotrimoxazole respectively (Additional file 8: Table S6).
In this retrospective study, we aimed to identify the most
prevalent pathogenic organisms involved in bloodstream
infections (BSI) over a ten year period (2005–14) in
patients in Dhaka, Bangladesh. We also aimed to
determine the antimicrobial susceptibility of the isolated
pathogens against multiple antibiotics to achieve a clear
outlook on the changing trend of their antibiotic
S. Typhi, the causative agent of typhoid fever, is a major
public health concern in Bangladesh and other developing
Asian countries. Several studies from Bangladesh have
already identified S. Typhi as a common cause of
bloodstream infection in this region [23–25]. We found
Salmonella species to be responsible for almost half of the
disease burden associated with BSI in Dhaka, Bangladesh
and about 80% of these infections were due to S. Typhi.
However, we have observed an overall decrease in
Salmonella species isolation rate over this study period.
This decrease may be attributed to the improved urban
water management system and sanitation practices in
Dhaka city over the past years.
A significant change in the epidemiology of S. Typhi
was observed in early 1990’s as those years experienced
a dramatic rise of MDR strains in Dhaka, Bangladesh
. By mid-1990s, about half of the S. Typhi strains
were MDR; these were resistant against three first line
antibiotics - ampicillin, cotrimoxazole and
chloramphenicol . Noticeably, after a few years of an initial
epidemic period, a decreasing trend in the isolation rate
of MDR S. Typhi strains was observed . Our study
confirms this trend to continue; from 2005 to 2010, the
percentage of MDR S. Typhi strains isolated declined
from 61.7 to 23.7% (Fig. 2). As indicated by recent studies
from Bangladesh, S. Typhi still shows a high level of
resistance against first line antibiotics . However, we have
observed a steady decrease in resistance against ampicillin
and cotrimoxazole over the ten year study period.
Hopefully, if this trend continues, then using the cheaper, first
line antibiotics again to treat S. Typhi infections might be
a possibility in near future. Ciprofloxacin or ceftriaxone is
Table 4 Percentage of antimicrobial resistance in E. coli strains isolated from blood cultures
AMP ampicillin, SXT cotrimoxazole, CN gentamicin, Cip ciprofloxacin, CRO ceftriaxone, Net netilmicin, Ak amikacin, Imp imipenem, Caz ceftazidime, CFM cefixime,
aValues in parentheses indicate the number of isolates tested each year
AMP ampicillin, SXT cotrimoxazole, Cip ciprofloxacin, CRO ceftriaxone, Pen G
penicillin G, E erythromycin, Azi azithromycin, CFM cefixime. aValues in
parentheses indicate the number of isolates tested each year; − indicates
absence of data in respective years
usually the choice of treatment against MDR Salmonella
strains . We found all Salmonella isolates were
consistently susceptible to ceftriaxone, but a very high level of
reduced susceptibility exists against ciprofloxacin. Studies
suggest that the presence of a mutation in the quinolone
resistance-determining region (QRDR) of the gyrA gene is
responsible for the emergence of this reduced
Non-fermenter Gram-negative bacilli are well known
for their ability to cause nosocomial infections [29, 30].
We identified Pseudomonas species and Acinetobacter
species to be the third (12.6%) and fifth (5.2%) most
prevalent organisms associated with BSI in Dhaka,
Bangladesh. A gradual decrease in the presence of
Table 6 Percentage of antimicrobial resistance in Staphylococcus
aureus strains isolated from blood cultures
2005 2006 2007 2008 2009 2010 2011 2012 2013 2014
(14)a (10) (15) (23) (26) (30) (25) (23) (23) (30)
Amp 100 100 88
AMP ampicillin, SXT cotrimoxazole, C chloramphenicol, E erythromycin, Cip
ciprofloxacin, CN gentamicin, CRO ceftriaxone, Van vancomycin, aValues in
parentheses indicate the number of isolates tested each year; − indicates
absence of data in respective years
Table 5 Percentage of antimicrobial resistance in Streptococcus
pneumoniae strains isolated from blood cultures
2005 2006 2007 2008 2009 2010 2011 2012 2013 2014
(49)a (32) (23) (23) (25) (25) (29) (23) (21) (26)
Acinetobacter species and a significant increase in the
presence of Pseudomonas species were observed over the
study period. This increase in BSI from Pseudomonas
species was possibly from the patients increased access to the
health care facilities over these years. Also noticeably,
Pseudomonas species was found to be more associated
with patients above five years of age; almost 70% of the
infections occurring among adults (≥18 years of age). A
recent study from Bangladesh also suggested that there is
a very low amount of bacteremia cases due to
Pseudomonas species among diarrheal children less than five
years of age .
Acinetobacter species and Pseudomonas species are
well known for their high degree of resistance against all
classes of antibiotics, and the emergence of MDR strains
makes it very difficult to treat them. An aminoglycosides
combined with a β-lactamase-stable β-lactam is the
typical choice of treatment for Acinetobacter species
infection , and carbapenems are known to be most
effective against their MDR strains . We observed
Acinetobacter species to develop increasingly high levels
of antibiotic resistance against all aminoglycosides, and
noticeably, very high levels of resistance against
imipenem (64%). Usually, in the case of resistance against
carbapenems, the expert’s choice of treatment for
Acinetobacter species infections entails colistin and tigecycline
. We found only 3.73% of the MDR Acinetobacter
species strains to be resistant against polymyxin B (300 u),
therefore it might be considered as a good treatment
choice against MDR Acinetobacter species. Colistin and
polymyxin B (300 u) are usually considered as the last
resort for treatment of infections due to MDR Pseudomonas
species , but we observed high levels of resistance
against them. In contrast, we found imipenem to be
consistently effective against all Pseudomonas species so it
might be considered as a good choice of treatment.
Besides non-fermenter and Salmonella species, other
clinically important Gram-negative bacteria were E. coli,
Enterobacter species, Klebsiella species and Serratia
species. E. coli has been reported as the leading cause of
BSI in developed countries ; however, data is relatively
unavailable for Bangladesh. We found E. coli to be
responsible for only 3.05% of the total BSI cases. It is likely
that the presence of E. coli is overshadowed by the
overwhelming presence of Salmonella species in Dhaka,
Bangladesh, so it would be unwise to ignore them as
A recent study from Bangladesh has shown a very high
level of antibiotic resistance and MDR level among E.
coli isolates from environmental samples . In this
study we identified a much higher level of antibiotic
resistance and MDR level (36% MDR in environment
samples vs. 62.38% MDR in our clinical samples) among BSI
causing E. coli strains. We found carbapenems to be the
Fig. 2 Decrease of multidrug-resistant (MDR) Salmonella Typhi isolation rate from blood cultures
most active antibiotics against E. coli. Overall, 3.2%
(including MDR strains) of the E. coli strains showed
resistance against them. So, carbapenems may be considered
as a good choice of treatment for BSI caused by E. coli.
Klebsiella species showed the highest level of resistance
against β-lactams, especially penicillins and third
generation cephalosporins. Previous studies suggested that
carbapenems were highly effective against Klebsiella species
until the early years of 2000s. According to Centers for
Disease Control and Prevention (CDC) in the USA,
Klebsiella species acquired the highest amount of
carbapenem resistance (from 1.6 to 10.4%) in the decade from
2001–2011. In accordance with this finding, we observed
a very dramatic rise in Klebsiella species resistance against
imipenem (0 to 46%) and meropenem (0 to 46.5%) from
2005 to 2014. In fact, we found Klebsiella species to show
the highest level of MDR (68%) among all the isolated
pathogens. Overall, E. coli, Klebsiella species and
Enterobacter species had relatively low prevalence throughout
this study period. However, they should be considered
important as they had the highest amount of MDR strains
and thus the potential to cause serious health threats.
Gram-positive bacteria also pose serious threats as
their incidence in BSI is increasing steadily worldwide.
The problem is particularly acute in nosocomial settings
where methicillin-resistant S. aureus (MRSA) and
vancomycin resistant Enterococcus (VRE) are considered
serious health threats [37, 38]. In this study, we observed
an increasing trend in the isolation rate of
Grampositive bacteria. This trend may be attributed to the
patient’s increased access to the health care facilities where
BSI from Gram-positive bacteria is common. We
identified S. aureus and S. pneumoniae as the two major
Gram-positive pathogenic bacteria associated with BSI
in Dhaka, Bangladesh. S. pneumoniae reportedly kills
about 0.7 to 1 million children under five years of age
every year worldwide and 90% of these deaths occur in
developing countries . Pneumonia is the primary
cause of childhood death in Bangladesh  and studies
suggest that the incidence of pneumonia among
preschool children in Bangladesh is surprisingly higher than
in developed countries [41, 42]. We found almost 75% of
the BSI cases from S. pneumoniae to occur among
children less than five years of age. However, a decreasing
trend in their isolation rate was observed throughout
this study period.
Increasing levels of antibiotic resistance are a big
concern for S. pneumoniae, especially their resistance
against macrolides and β-lactams, which are the first
choice of treatment for most pneumonia cases. One
recent review indicates a very high level of penicillin
resistance among S. pneumoniae strains in different Asian
countries . However, we observed only a small
increase in penicillin resistance in Dhaka, Bangladesh.
Another study from Dhaka indicates the presence of
high level of resistance against ciprofloxacin. However
our study found a much lower level of resistance against
ciprofloxacin and also we observed a decreasing trend in
their susceptibility pattern . Ampicillin and
ceftriaxone were found to be consistently active against S.
pneumoniae, so they might be considered as good treatment
choices for them. Emergence of MRSA strain marks
another very important epidemiological change for the past
few decades . Naturally, S. aureus are susceptible to
commonly used antibiotics. However methicillin
resistance is associated with resistance against a broad range
of antibiotics . Over the study period, we found
overall 50.2% of S. aureus strains to be MDR. In the first five
years of our study, we identified 34.4% of the S. aureus
strains to be oxacillin (a synthetic form of methicillin)
resistant; however, the percentage was much higher
(58.7%) amongst the MDR strains. Vancomycin has been
widely used as the preferred choice of treatment for
MRSA strains , and we also found vancomycin to be
highly effective against all S. aureus strains; only 2.1%
strains were resistant. Linezolid was also found to be
very effective against S. aureus; only one resistant strain
was detected over the study period. Therefore, both
vancomycin and linezolid might be considered as a good
treatment choices against S. aureus which are resistant
to commonly used antibiotics.
Limitations of the study
Due to the lack of resources, we were not able to
differentiate the samples received from our hospital patients
and from domiciliary patients. As a result we could not
show the difference in epidemiology between
nosocomial and community acquired BSI. Also due to lack of
resources, we were not able to collect patient data on
the clinical manifestations or any other patient
characteristics, other than age and sex, which could be
considered as risk factors for BSI. However, we confirm that
each patient was diagnosed with signs of bacteremia by
their respective physicians. Also, we were not able to
perform any molecular tests on received samples due to
lack of required resources.
This study clearly identifies the bacterial pathogens
involved with bloodstream infections (BSI) occurring in
Dhaka, Bangladesh between January 2005 to December
2014. It also reveals their antibiotic susceptibility patterns
for commonly used antibiotics. We expect our findings to
help healthcare professionals to make informed decisions
and provide better care for their patients. Also, we hope
this study to help researchers and policy makers to
prioritize their research options to face future challenges
of infectious diseases both at home and abroad.
Additional file 1: Table S7. Association of two age groups with distinct
bacterial pathogens causing BSI in Dhaka, Bangladesh. (DOC 38 kb)
Additional file 2: Table S8. Association of sex with distinct bacterial
pathogens causing BSI in Dhaka, Bangladesh. (DOC 40 kb)
Additional file 3: Table S1. Percentage of antimicrobial resistance in
Acinetobacter species strains isolated from blood cultures. (DOC 35 kb)
Additional file 4: Table S2. Percentage of antimicrobial resistance in
Pseudomonas species strains isolated from blood cultures. (DOC 35 kb)
Additional file 5: Table S4. Percentage of antimicrobial resistance in
Enterobacter species strains isolated from blood samples. (DOC 33 kb)
Additional file 6: Table S3. Percentage of antimicrobial resistance in
Klebsiella species strains isolated from blood cultures. (DOC 38 kb)
Additional file 7: Table S5. Percentage of antimicrobial resistance in
Streptococcus species strains isolated from blood cultures. (DOC 36 kb)
Additional file 8: Table S6. Percentage of antimicrobial resistance in
Enterococcus faecalis strains isolated from blood cultures. (DOC 36 kb)
FAN: Fastidious antibiotic neutralization; API: Analytical profile index
This research study was funded by core donors which provided unrestricted
support to icddr,b for its operations and research. Current donors providing
unrestricted support include: Government of the People’s Republic of
Bangladesh; Global Affairs Canada (GAC); Swedish International Development
Cooperation Agency (Sida) and the Department for International Development
(UK Aid). We gratefully acknowledge these donors for their support and
commitment to icddr,b’s research efforts. The funders had no role in study
design, data collection and analysis, decision to publish, or preparation of the
manuscript. We also thank Dr. Daniel Leung, from University of Utah, for his
valuable comments on draft versions of this manuscript.
This research study was funded by core donors which provide unrestricted
support to icddr,b for its operations and research. But the funders had no
role in study design, data collection and analysis, decision to publish, or
preparation of the manuscript.
Availability of data and materials
The raw data can be made available to the interested researchers by the
authors of this article if requested.
DA designed the study and reviewed the manuscript for important
intellectual content. MAN analyzed the data and wrote the manuscript. ABS
took part in data analysis and reviewed the manuscript. FH, NA, TS, MSR
performed experimental works. MSBE was responsible for collecting the data.
MMR critically revised the manuscript. All the authors read and approved the
The authors declare that they have no competing interests.
Consent for publication
Ethics approval and consent to participate
The study protocol was approved by the Ethical Review Committee of the
icddr,b (PR-14042). Patient consent for sample handling was not required as
samples were subject of routine management and samples were further
anonymised for research use.
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