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Research Article
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Antimicrobial Susceptibility Pattern of Microorganisms Involved
in the Pathogenesis of Surgical Site Infection (SSI); A 1 Year of Surveillance |
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F. Khorvash,
K. Mostafavizadeh,
S. Mobasherizadeh,
M. Behjati,
A. E. Naeini,
S. Rostami,
S. Abbasi,
M. Memarzadeh
and
F. A. Khorvash
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ABSTRACT
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The aim of this study is to identify the antibiotic sensitivity pattern
of pathogens involved in the process of surgical site infection, in surgical
wards. Changes made in the pattern of antibiotic use will result in different
microorganism susceptibility patterns, which needs correct determination
for precise empiric antibiotic therapy. One thousand patients (62% men
and 38% women, 18-74 years old, with mean age 43±8)) who underwent
surgical treatment, in Alzahra University Hospital, Isfahan University
of Medicine, Isfahan, Iran, were studied from 2005 to 2006. Surgical wound
infections, based on the reported criteria, were aspirated for culturing
within 1 plus gram staining of prepared smears. Minimum Inhibitory Concentrations
(MICs) were determined for samples and all derived data were compared
by SPSS 13 and WHO net 5 software. The prevalence of SSI was 13.3% with
150 positive cultures, totally. Of 150 bacteria, isolated from surgical
site infections Staphylococcus aureus had most frequency (43%).
Resistance of isolated organisms was 41.7% in amikacin, 65 and 78.6% in
ceftazidime, 85.7% in ceftriaxone, 61.5% in ciprofloxacin, 78.8% in gentamicine,
6.4% in imipenem, 13% in meropenem and 70.6% in trimethoprim/sulfamethoxazole,
respectively. 78.9% of Staphylococcus aureus isolates were MRSA
and vancomycine was the most effective antibiotic without any resistance.
Among 10 isolates of coagulase negative Staphylococcus, no vancomycine
resistance was seen, but in contrast all cases were resistant to oxacillin.
The most common gram negative organism was Klebsiella (18 isolates)
in which 100 and 80% were sensitive to imipenem and meropenem, respectively.
Seventeen cases were E. coli, in which the most sensitivity was
to meropenem (80%) and imipenem (77.8%). Thirteen cases of Pseudomonas
were detected, in which 16.7% were resistant to imipenem and 8.3% to meropenem.
Our results demonstrated that the total antibiotic resistance is increasing
among SSIs, with an up sloping pattern, which will contact with a constant
empiric antibiotic therapy. So, precise up to date antibiogram tantalize
us toward balancing the rate of total antibiotic resistance to SSIs.
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How
to cite this article:
F. Khorvash, K. Mostafavizadeh, S. Mobasherizadeh, M. Behjati, A. E. Naeini, S. Rostami, S. Abbasi, M. Memarzadeh and F. A. Khorvash, 2008. Antimicrobial Susceptibility Pattern of Microorganisms Involved
in the Pathogenesis of Surgical Site Infection (SSI); A 1 Year of Surveillance. Pakistan Journal of Biological Sciences, 11: 1940-1944. DOI: 10.3923/pjbs.2008.1940.1944 URL: https://scialert.net/abstract/?doi=pjbs.2008.1940.1944
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INTRODUCTION
Surgical-site infections (SSI) are the most common hospital-acquired
infection among surgical patients and the third most frequent hospital-acquired
infection in the general hospital population (Poulakou and Giamarellou,
2007). They cause significant postoperative morbidity, mortality and prolong
hospital stay (Bratzler, 2006).
However, incorrect use of antibiotics occurs in 25 to 50% of operations
(Bedouch et al., 2004; Pons-Busom et al., 2004). Inappropriate
use of broad spectrum antibiotics or prolonged courses of prophylactic
antibiotics, disposes all patients at even greater infection risk because
of the development of antibiotic-resistant pathogens (Dahms et al.,
1998). According to data from the National Nosocomial Infections Surveillance
System (NNIS), there has been little change in the incidence and distribution
of the pathogens isolated from infections during the last decade.
So, the aim of this study is to identify the antibiotic sensitivity pattern
of pathogens involved in the process of surgical site infection, in surgical
wards.
MATERIALS AND METHODS
During the 12 month period from 2005 to 2006 we studied 1000 patients
(62% men and 38% women, 18-74 years old, with mean age 43±8) who
underwent surgical treatment (abdominal, vascular, orthopedic and reparative
surgery), in Alzahra University Hospital, Isfahan University of Medicine,
Isfahan, Iran. A wound infection was identified by the presence of purulent
discharge from the incision with erythematous cellulitis, induration or
pain and demonstrable fluid collection noted on ultrasound after surgery.
Purulent exudates were obtained from the open discharging wounds with
a sterile cotton swab. Aspirates were obtained by preparing the wound
area with alcohol, inserting a sterile needle through the healing incision
and aspirating fluid into a sterile syringe. Culturing was done within
1 h using standard bacteriological inoculation techniques. For the isolation
of anaerobes, specimens were inoculated onto Columbia blood agar plates
enriched with hemin and menadione, incubated in an anaerobic chamber at
37°C and examined at 48 and 96 h. Any growth was subsequently identified
by standard microbiological methods. Gram stains were also performed and
recorded at the time of culturing. Microscopic examination of gram stained
slides and subsequent identification of bacterial isolates were done by
an experienced senior microbiologist.
Minimum Inhibitory Concentrations (MICs) were determined by Mueller Hinton
plates containing 2% NaCl which inoculated with a direct colony suspension
equivalent to a 0.5 MacFarland standard in accordance with the National
Committee for Clinical Laboratory Standards. The breakpoints mentioned
in the last edition of CLSI (Clinical and Laboratory Standards Institute)
tables M7A6 was used to determine susceptibility
and resistance. The plates were incubated at 35°C for 24 h MIC of
9 antibiotics on isolated bacteria was determined by gradient concentration
method (E-Test®; AB BIODISK Co. Sweden). Quality control was tested
by E. coli ATCC25922 and Staphylococcus ATCC29213. Data
was analyzed by SPSS 13 and WHO net 5 software.
RESULTS
The prevalence of SSI was 13.3% with 150 positive cultures, totally.
Of 150 bacteria, isolated from surgical site infections, 65 (43%) were
Staphylococcus aureus, 27 (18%) were E. coli, 32 (21%) were
Klebsiella sp., 20 (13%) were Pseudomonas sp., 15 (10%)
were Staphylococcus coagulase negative, 8 (5%) were Acinetobacter
spp., 8 (5%) were Enterobacter, 2 (1.3%) were Serratia,
1 (0.6%) was Enterococcus, 2 (1.3%) were Citrobacter and
0% of anaerobic or mixed isolates. According to break point used for susceptibility
meet CLSI M7-A6 (Clinical and Laboratory Standard Institute) criteria,
resistance of isolated organisms was 41.7% in amikacin, 65 and 78.6% in
ceftazidime, 85.7% in ceftriaxone, 61.5% in ciprofloxacin, 78.8% in gentamicine,
6.4% in imipenem, 13% in meropenem, 70.6% in trimethoprim/sulfamethoxazole
respectively. 78.9% of Staphylococcus aureus isolates were MRSA
(MIC of oxacillin >4) and vancomycine was the most effective antibiotic
without any resistance (97.1% sensitivity). The susceptibility of staphylococcus
aureus isolates in rifampin was 85.2% but we could not use this agent
against Staphylococcus alone because of rapidly production resistance
to it. Amikacin and gentamicine resistance were 66.7% and then due to
this high rate of resistance, they should be in combination with other
drugs for synergistic effect. Clindamycin was a relatively nice antibiotic
for this organism too (41.4% sensitivity) but should be used only after
antibiogram detection. Fleurocinolones were not a good choice in our study,
hence ofloxacine resistance was 77.8% and ciprofloxacin resistance rate
was 62.5% in isolates (Table 1). Among 10 isolates of
coagulase negative Staphylococcus, no vancomycine resistance was
seen, but in contrast all cases were resistant to oxacillin. A relative
rifampin resistance (40%) and a high clindamycin (60%) were also seen
(Table 2). The most common gram negative organism was
Klebsiella (18 isolates) in which 100 and 80% were sensitive to
imipenem and meropenem, respectively. 85.7% of them were resistant to
gentamicine. Among cephalosporins, resistant rate to cefepime, ceftazidime
and ceftriaxone was 69.2, 85.7 and 77.8%, respectively. Ofloxacine resistance
was more than ciprofloxacin (66.7 and 33.3%, respectively) (Table
3). 17 cases were E. coli, in which the most sensitivity was
to meropenem (80%) and imipenem (77.8%).
Table 2: |
Antibiotic susceptibility pattern of coagulase negative Staphylococcus
in surgical site infections |
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Table 3: |
Antibiotic susceptibility pattern of Klebsiella in surgical
site infections |
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Table 4: |
Antibiotic susceptibility pattern of E. coli in surgical
site infections |
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Table 5: |
Antibiotic susceptibility pattern of Pseudomonas in surgical
site infections |
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R: Resistant, I: Intermediate, S: Susceptible, MIC:
Minimal Inhibitory Concentration |
Amikacin was more effective than gentamicine (sensitivity rate 73.3 and
10%, respectively). Among cephalosporins, 23.5, 10 and 100% were resistant
to cefepime, ceftazidime and ceftriaxone, respectively. Ofloxacine was more
effective than ciprofloxacin (sensitivity rate 28.6 and 20%, respectively)
( Table 4). 13 cases of Pseudomonas were detected,
in which 16.7% were resistant to imipenem and 8.3% to meropenem. Amikacin
resistance was less than gentamicine among them (60 and 83.3%, respectively).
Cefepime resistance was very high (87.5%), ceftriaxone and ceftazidime resistance
were 88.9 and 57.1%, respectively ( Table 5). 100% of
Enterobacter (8 cases) and Acinetobacter (8 cases) were sensitive
to imipenem and meropenem. Cephalosporins were not effective antibiotic
against them and resistance rate was great, but amikacin was an effective
antibiotic against Enterobacter (83.3% sensitivity rate).
DISCUSSION
SSIs are increasingly becoming an institutional marker of quality assurance.
These infections, representing a global threat, are associated with great
complications (Hedrick et al., 2006). The most important ones for
the patients who experience postoperative complications are increased
hospital length of stay, readmission rates, mortality rates, costs of
care, hospitals and payers (Bratzler, 2006) and most importantly emergence
of multi-drug-resistant bacteria (Poulakou and Giamarellou, 2007). Juristically,
each of these complications has their own disadvantage per se and is related
to each other somehow; increased hospital length will increase costs and
emergence of MDR and vice versa: a vicious cycle. Thinking to global trends
to decreasing the hospital length, we will encounter SSIs after hospital
discharge. Then it seems reasonably that the diagnosis of SSIs is very
important to decreased or prohibit the complications of late diagnosis
hospitalized and post-discharge SSIs. Neglecting the origin of SSI advent,
the problem of antibiotic resistant cases of SSI, is a catastrophe.
Perhaps, different risk factors are associated with different bacterial
colonization of surgical site and therefore different antibiotic resistant
organisms. For example, the great risk factor for SSI following urological
operations is thought to be the presence of a preoperative urinary tract
infection (UTI) (Hamasuna et al., 2004). The above matter attracts
our minds toward this fact that different populations should decide discretely
upon their most usual present risk factors (as obesity, pre-hospitalization
ulcers and more). So, perhaps the presence of a unique preventive strategies
for SSIs incidence and more importantly, antibiotic resistant SSIs, will
be too helpful.
Treatment of infected patients depends on several factors including the
severity of the infection, degree of antibiotic resistance pathogens,
the sensitivity to alternative agents and the achievable concentration
of antibiotic at the site of the infection. Outbreaks of infection have
occurred and various control measures have been suggested in attempts
to limit the spread of resistant strains (Gastmeier, 2007).
Staphylococci and Enterococcus are the most culprit pathogens
in surgical-site (Taylor et al., 2000), so a small fraction of
drug resistance among these gram-positive bacteria will impose great catastrophes
to patients with SSIs. Methicillin/oxacillin resistant SA, continues to
plague hospitals (Marshall et al., 2004), is prevalent in many
of the country`s most prestigious hospitals as demonstrated by adverse
publicity (the superbug) and frequently observed in is often accompanied
by multidrug resistance (Guyot and Layer, 2006). Vancomycine is usually
the drug of choice for infections caused by MRSA, so the emergence of
intermediate vancomycine resistant S. aureus is an important matter
(Rapp, 2000). One strategy to combat the increasing rate of drug-resistant
gram-positive pathogens seems to be prudent use of available antibiotics
(Rapp, 2000). (SSIs), especially antibiotic-resistant ones, are a great
concern for preoperative cares (Plonczynski, 2005). While administration
of the correct antibiotic in its effective dose and in correct optimal
time seems too helpful in preventing or reducing the occurrence of SSIs
and also MDR cases (Plonczynski, 2005), but some important prophylactic
measures are also needed (Chong and Sawyer, 2002): moving away from widespread
antibiotic administration, surgical prophylaxis, new antibiotic guidelines
and researches for antibiotic administration for each specific operation
and new substitute for moderate to sever targets of resistance (which
may only be a short-term answer).
We should also consider that when we decide to use some antibiotics to
reduce the risk of the emergence of resistant to reserved powerful antibiotics,
we may increase resistant to that antibiotic for the other species, for
example use of third generation cephalosporins will decrease the emergence
of VREs but will increase the emergence of MRSA. It`s demonstrated by
Engemann et al. (2003) that the 90-day mortality rate of patients
infected with Methicillin-resistant S. aureus (MRSA) was greater
than patients infected with Methicillin-susceptible S. aureus.
Some simple prophylactic measures such as improved hand hygiene (Marshall
et al., 2004), preoperative skin care (60 min before incision)
(Dohmen, 2006), intranasal Mupirocin application (controversial) for staph.
Carriers (Young and Winston, 2006), avoidance of antibiotic application
after wound closure, appropriate preoperative prophylactic antibiotics
(Zoumalan and Rosenberg, 2008), appropriate catheter application (O`Grady
et al., 2002), screening patients for the presence of preoperative
colonization or perhaps community-acquired MRSA especially when risk factors
are present, decolonization of MRSA strains preoperatively (if present
according to screening measures (Simor and Loeb, 2004) ,screening patients
for the occurrence of post discharge SSIs (Oliveira and Carvalho, 2007)
research for new drugs with the ability to get the depth of wounds with
less concentration and so on.
An overview to the above measures, the rate of SSIs occurrence and sequentially
MDR SSIs will be decreased. But it`s apparent that the overall rates of
SSIs have been slowly decreasing and drug-resistant species continue to
become more prevalent. So, even best tries for decrease SSIs, won`t be
able totally to combat with ever-increasing rate of antibiotic resistance
in nosocomial infections. This fact is associated with problems in empiric
therapy based strategies. Although, risk factor assessment for the present
catastrophes seem well, but some studies showed that the risk factors
were similar to those reported from countries with more resources.
CONCLUSION
Present results demonstrated that the total antibiotic resistance is
increasing among SSIs, with an up sloping pattern, which will contact
with a constant empiric antibiotic therapy. So, precise up to date antibiogram
tantalize us toward balancing the rate of total antibiotic resistance
to SSIs.
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