In-Vitro Efficacy of Cefepime against Multi-drug Resistant Pseudomonas aeruginosa – An Alarming Situation in our Setup.
12 The Open Drug Resistance Journal, 2011, 1, 12-16
1876-5211/11 2011 Bentham Open
In Vitro Efficacy of Cefepime Against Multi-Drug Resistant Pseudomonas
aeruginosa – An Alarming Situation in our Setup
Luqman Satti*,1, Shahid Abbasi2, Tanveer Ahmed Qumar1, Muhammad Shoaib Khan3 and
Zahid Ahmed Hashmi4
1Department of Pathology, Combined Military Hospital, Dera Ismail Khan, Pakistan
2Consultant Microbiologist, Armed Forces Institute of Pathology, Rawalpindi, Pakistan
3Department of Surgery, Combined Military Hospital, Dera Ismail Khan, Pakistan
4Gomal Medical College, Dera Ismail Khan, Pakistan
Abstract: Background: Third generation cephalosporins are still most commonly used antibiotics empirically in our setup
leading to emergence of resistance in this group. In this environment of increasing resistance, empirical use of this group
of antibiotics would be a futile effort. Therefore, this study was conducted to evaluate the in vitro efficacy of fourth
generation cephalosporin cefepime against multi-drug resistant isolates of Pseudomonas aeruginosa from various clinical
specimens in our setup.
Place and Duration of Study: Department of Pathology, Combined Military Hospital Dera Ismail Khan, Pakistan from
January 2011 to May 2011.
Methodology: All the clinical specimens giving growth of Pseudomonas aeruginosa were included in the study. Modified
Kirby-Bauer disk diffusion method was used for sensitivity testing. Isolates resistant to three or more than three groups of
antibiotics were included in the final results.
Results: A total of 100 multi-drug resistant Pseudomonas aeruginosa isolates were cultured from various clinical
specimens. Out of 100 isolates, 71% were resistant to cefepime while resistance rate of amikacin, gentamicin, ceftazidime,
tazobactem/piperacillin, sulbactam/piperacillin, imipenem and polymyxin were 61%, 83%, 72%, 10%, 2%, 45% and 2%
Conclusion: Drug resistance in Pseudomonas aeruginosa is alarming as it is now increasing even in newer generation of
drugs. It is the need of hour to follow strict hospital infection control and antibiotic policies to halt the spread of this
Keywords: Cefepime, multi-drug resistance, Pseudomonas aeruginosa.
fermenter and produces visible pigments, characteristics
which are used for its rapid diagnosis in the laboratory. It is
also a part of normal skin flora of humans but can cause life
immunocompromised hosts . It has been implicated in
diverse group of infections such as otitis externa, burn
wounds, decubitus ulcers, cystic fibrosis, urinary tract
infections, ventilator associated pneumonia (VAP) and
septicemia specially in neutropenic and transplant patients. It
has posed a serious problem in nosocomial infections
specially in intensive care units (ICUs) because of its innate
resistance to many antibiotics . It has also been involved
in biofilm formation particularly in cystic fibrosis patients
with its unique characteristic to develop resistance to all
Pseudomonas aeruginosa is an oxidase positive, non-
infections specially in
*Address correspondence to this author at the Department of Pathology,
Combined Military Hospital, Dera Ismail Khan, Pakistan;
Tel: +923215570838; E-mail: Luqmansatti@hotmail.com
antibiotics with prolonged therapy . In recent years, multi-
drug resistant (MDR) Pseudomonas aeruginosa specially in
burn wounds and decubitus ulcers has emerged rapidly
creating serious problems for the clinicians .
(wrong dose or duration, antibiotics in viral infections)
leading to the emergence of resistant isolates . With the
extensive use of third generation cephalosporins (most
widely prescribed antibiotics) in hospitals, now many
isolates are resistant to even this class of antibiotics .
Cefepime is the most active fourth generation cephalosporin
which was introduced in 1993. It has rapid penetration into
the periplasmic space as compared to third generation
cephalosporins and has more activity against gram positive
and gram negative organisms. It has remarkable activity
against MDR isolates of Pseudomonas aeruginosa,
Klebsiella pneumoniae, Citrobacter spp, Serratia spp,
Proteus mirabilis but is less active against Bacillus fragillis
. It is ineffective against methicillin-resistant strains of
Staphylococcus and Enterococcus spp. It can be used in the
About 50% of the antibiotics prescribed are irrational
In Vitro Efficacy of Cefepime Against Multi-Drug Resistant Pseudomonas aeruginosa The Open Drug Resistance Journal, 2011, Volume 1 13
management of pneumonia, skin and soft tissue infections,
urinary tract infection and neutropenic patients. It is the best
empirical choice for the treatment of hospital acquired
infections specially in intensive care units . Because of its
stability against many beta-lactamases and being a poor
inducer of AmpC beta-lactamases, it can be used against
those Enterobacteriaceae which are resistant to third
cefepime against MDR Pseudomonas aeruginosa. In
Pakistan, to date, no study has been published on the
evaluation of cefepime agaisnt MDR Pseudomonas
aeruginosa. In the background of increasing resistance
pattern, excessive empirical use of third generation
cephalosporins and poor hospital infection control policies in
our set-up, this study was conducted to see the efficacy of
cefepime against MDR Pseudomonas aeruginosa from
various clinical specimens.
Very few studies have been reported on the evaluation of
MATERIALS AND METHODOLOGY
the department of Pathology, Combined Military Hospital
Dera Ismail (D.I.) Khan, Pakistan. A total of 100 MDR
Pseudomonas aeruginosa isolates from various clinical
specimens were included in the five months study period
from January 2011 to May 2011. This hospital receives
specimens for bacterial culture mainly from District
Hospital, and Mufti Mehmood Teaching Hospital D.I. Khan.
Specimens from the patients admitted in Combined Military
Hospital D.I. Khan were also included in our study. Pus/pus
swab specimens were mostly from burn patients, wound
infections, and diabetic foot ulcers. Ear swabs were from
patients suffering from chronic suppurative otitis media
(CSOM). All the sputum specimens were from patients
suffering from COPD while paired blood specimen was
collected for blood culture. Repeat or multiple specimens
from same patients giving growth of Pseudomonas
aeruginosa were excluded from the study.
This laboratory based descriptive study was carried out in
Inoculation and Culture
pus swab, urine, sputum, blood, and tissue) were inoculated
on 5% Sheep Blood Agar (Oxoid, UK), MacConkey agar
(Oxoid, UK) Chocolate Agar (Oxoid, UK) and incubated at
37ºC for 24-48 hours. Blood culture specimens were
incubated in Brain Heart Infusion (BHI) broth (Oxoid, UK)
and subcultured on every alternate day for upto seven days.
Urine samples were inoculated on CLED (Oxoid, UK)
medium and incubated at 37ºC for 24 hours. Gram stain and
rapid oxidase test was performed on all the cultured isolates
for the confirmation of Pseudomonas aeruginosa.
In the protocol followed, all the clinical specimens (pus,
Antimicrobial Susceptibility Testing (AST)
for sensitivity testing and the disks employed were cefepime
30?g (Oxoid, UK), amikacin 30?g (Oxoid, UK), gentamicin
10?g (SPAN Diagnostic, France), ceftazidime 30?g (Oxoid,
UK), tazobactem/piperacillin 10/100?g (Oxoid, UK), sulbac-
tam/piperacillin 30/100?gm (Oxoid, UK), imipenem 10?g
Modified Kirby-Bauer disk diffusion method was used
(Oxoid, UK) and polymyxin B 300units (Oxoid, UK). All
the sensitivity plates were incubated at 37°C for 16-18 hours.
Pseudomonas aeruginosa ATCC 25853 was used as control
to check disks potency.
were measured with a scale in millimeters and each zone size
was compared with known standards . The isolate was
then labelled as sensitive, resistant or intermediate depending
upon the zone size. A Pseudomonas aeruginosa resistant to
three or more group of antibiotics was considered as MDR.
Antibiotics giving zone sizes in the intermediate ranges are
usually not effective against that isolate, however, increased
dose of that antibiotic can be given if there are no other
therapeutic options .
After incubation period, zone diameters around the disks
Pseudomonas aeruginosa, 63 (63%) were from male patients
and 37 (37%) from female patients. The age range was 4-72
years with mean age 38 ± 15.2 years with maximum number
of patients in the fourth decade of life. Maximum number of
isolates were recovered from pus/pus swabs followed by ear
swabs as shown in Fig. (1). Pseudomonas aeruginosa from
pus specimens showed maximum resistance to cefepime as
shown in Table 1.
Out of total 100 specimens yielding growth of
tazobactem/piperacillin. Comparison of sensitivity pattern of
cefepime with other antibiotics is shown in Table 2. Majority
of the isolates were resistant to five antibiotics as depicted in
Fig. (2). There were two isolates from pus which were even
resistant to polymyxin that is pan-resistant Fig. (3).
Most effective drug in our study against Pseudomonas
was sulbactam/piperacillin followed by
pumps specially MexAB-OprM efflux system are the main
mechanisms of resistance in Pseudomonas aeruginosa .
In recent years, methicillin-resistant Staphylococcus aureus,
a so called “Superburg” casuing noscomial infections and
multidrug resistant Pseudomonas aeruginosa infections have
gained much attention among health care professionals .
It is evident from our study that Pseudomonas aeruginosa is
becoming more resistant to even newer generation
cephalosporins such as cefepime. In our study, overall
resistance of cefepime was 71% and pus specimens yielded
majority of the resistant isolates. Sulbactam/piperacillin and
tazobactem/piperacillin were the most effective antibiotics
against Pseudomonas aeruginosa in our study with 98% and
92% susceptibility respectively. Sensitivity of imipenem was
55% while gentamicin was the least sensitive drug in our
study that is only 17% isolates were sensitive. As far as in
vitro efficacy of cefepime is concerned, our results are
comparable to the findings of a study done by Jazani et al. in
which resistance rate of cefepime against Pseudomonas
aeruginosa was 75.4% but imipenem was most effective
drug with resistance rate of only 27% . In another study
done by Gad et al. on 81 clinical isolates of Pseudomonas
Betalactamase production and use of multiple efflux
14 The Open Drug Resistance Journal, 2011, Volume 1 Satti et al.
aeruginosa, resitance rate of cefepime was 29% while
amikacin was the most effective drug (resistance rate 8%)
followed by meropenem (22%) . In another study done
by de Macedo and Santos, imipenem and amikacin were the
most useful antibiotics against Pseudomonas aeruginosa
which is not in line with our results .
common specimens submitted in our laboratory. All the ear
swabs yielding growth of Pseudomonas aeruginosa were
from patients suffering from chronic suppurative otitis media
(CSOM). Out of total 23 isolates of Pseudomonas
aeruginosa from CSOM patients 10 (43.5%) were sensitive
Second to pus specimens, ear swabs were the most
to cefepime while again sulbactam/piperacillin and
tazobactem/piperacillin were most effective drugs. Similarly
out of 14 urine specimens, cefepime was effective in 8
(57.1%) isolates. In a study done by Patel et al., out of total
64 urinary isolates of Pseudomonas aeruginosa, resistance
rate of cefepime was 15.6% .
in which Proteus mirabilis was also cultured along with
Pseudomonas aeruginosa and all of them were also resistant
to cefepime along with Pseudomonas aeruginosa. There was
only one isolate of Pseudomonas aeruginosa which was
isolated from paired blood specimen and the isolate was
In our study, there were 5 specimens from burn patients
Fig. (1). Frequency of isolation of Pseudomonas aeruginosa from various clinical specimens (n=100).
Fig. (2). Analysis of drug resistance pattern against Pseudomonas aeruginosa (n=100).
In Vitro Efficacy of Cefepime Against Multi-Drug Resistant Pseudomonas aeruginosa The Open Drug Resistance Journal, 2011, Volume 1 15
sensitive to cefepime. The patient was later on diagnosed as
a case of chronic myeloid leukemia. Out of a total of 6
sputum specimens from patients with chronic obstructive
pulmonary disease, only 2 (33.3%) isolates were sensitive to
cefepime while all were sensitive to tazobactem/piperacillin
and three were resistant to imipenem. These findings are
again in contrary to the findings of a study done by
Christieson et al. in which out of total 67 Pseudomonas
aeruginosa isolates from cystic fibrosis patients, 92.5% were
sensitive to imipenem while 77.6% were sensitive to
cefepime . An interesting observation in our study was
that 57% of the total isolates were only sensitive to
polymyxin (5-drug resistant). This is an alarming situation as
these three drugs are injectables, costly, and not easily
available in remote settings like ours. The patient had to face
many difficulties in receiving these drugs from larger cities
or they are ultimately referred to tertiary care hospitals.
Fig. (3). A pan-drug resistant isolate of Pseudomonas aeruginosa
from a burn patient.
drugs which have re-emerged in the settings of increased
drug resistance . They are now reserved as last option in
treating MDR Pseudomonas aeruginosa. In our study, there
were 2 isolates from burn patients which were even resistant
to polymyxin (pan-drug resistant). Pandrug resistant isolates
are a major concern for the clinicians as the therapeutic
options are limited and presently the only choice left is
polymyxin. Polymyxin has been used with success in cases
of meningitis and pneumonia, but has been associated with
renal toxicity . The sensitivity pattern in our study shows
that the resistance to even polymyxin is increasing adding to
the miseries of patients.
Polymyxin B and colistin are older antipseudomonal
Table. 1. Sensitivity Pattern of Pseudomonas aeruginosa
Against Cefepime Isolated from Various Clinical
Specimen Type Total Isolates Sensitive Resistant
Ear swab 23 10 13
Pus 56 08 48
urine 14 8 6
sputum 6 2 4
blood 1 1 -
Total 100 29 (29%) 71 (71%)
lethal pathogen in hospital environment specially in burns
and ICU patients is becoming resistant even to newer
antibiotics such as cefepime. It is not only creating a grave
challenge for the clinicians but is also very difficult to
eradicate from the hospital environment. The main reasons
for this critical situation are irrational use of antibiotics, poor
hospital infection control policies, substandard drugs and
lack of knowledge of organism’s innate resistance to
antibiotics. If timely interventions/measures are not taken to
Our study concludes that Pseudomonas aeruginosa, a
Table. 2. Comparison of Sensitivity Pattern of Cefepime Against Pseudomonas aeruginosa with Other Antibiotics (n=100)
Pus/Pus Swab Ear Swabs Urine Sputum Blood
S R S R S R S R S R
Total % of
FEP 8 48 10 13 8 6 2 4 1 - 71
TZP 49 7 21 2 13 1 6 - 1 - 10
SPR 54 2 23 - 14 - 6 - 1 - 2
IMP 25 31 17 6 9 5 3 3 1 - 45
CAZ 14 42 10 13 3 11 1 5 - 1 72
AK 20 36 9 14 6 8 4 2 - 1 61
GM 9 47 4 19 3 11 1 5 - 1 83
Poly 54 2 23 - 14 - 6 - 1 - 2
S = sensitive, R = resistant, FEP = cefepime, TZP = tazobactem/piperacillin, SPR = sulbactam/piperacillin, IMP = imipenem, CAZ = ceftazidime, AK = amikacin, GM = gentamicin,
Poly = polymyxin.
16 The Open Drug Resistance Journal, 2011, Volume 1 Satti et al.
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Received: May 29, 2011
© Satti et al.; Licensee Bentham Open.
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Revised: June 16, 2011 Accepted: June 22, 2011