Gene Ther Mol Biol Vol 9, 263-268,
2005
The prevalence of antibiotic resistance in
anaerobic bacteria isolated from patients with skin infections
Gita Eslami*, Fatemeh Fallah, Hossein Goudarzi and Masoumeh
Navidinia
Microbiology
Department, Medical Faculty Shaheed Beheshti University of Medical Science
& Pediatric Infectious Research Center Tehran- Iran __________________________________________________________________________________
*Correspondence: Gita Eslami Ph.D, Associate Professor, Microbiology Department,
Medical Faculty of Shaheed Beheshti University, Evin Street, Charman High way,
Tehran-Iran; Tel: 0098-21-23872556; Fax: 009821-2413042; E-mail:
g_eslami@yahoo.com
Key words: Antibiotic resistance, anaerobic bacteria,
skin infection
Summary
Antibiotic
resistance in Anaerobic bacteria and the lack of proper outline to treatment of
anaerobic infections have been increased in recent years, In this study 100
patients with skin infections (10-60 years old) were considered. Specimens were
collected in the sterile condition and transported and cultured in the
Thioglycolate media. After growing and staining of bacteria (gram staining)
from selective media, bacteria were cultured in the differentiated media.
Strains that were isolated, undergone antibiogram test (Kirby bauer method).
Skin infections are usually polymicrobial involving aerobic and anaerobic
bacteria. Common aerobic and anaerobic facultative bacteria contained:
Staphylococcus aureus (37.3%), non coagolase Staphylococci (8.5 %), group A
streptococci (16.3 %), group D enterococci (5.7%), E.coli (15.6 %),
enterobacter-spp (5.6%), citrobacter-spp (0.8%), Pseudomonas aeruginosa (6.9%),
proteus-spp (2.7%), others (0.6%). Predominant anaerobic bacteria contained:
Peptostreptococcus-spp (42.5%), pigmented prevotella and Porphyromon-spp
(5.4%), Fusobacterium (7.6%) Bacteroides-spp (23.2%), Clostridium-spp (18.4%),
Propionebacteriom acnes (2.1%), others (0.8%). Atibiogram test was done on
aerobic-anaerobic facultative bacteria. Susceptibility of these bacteria were
as following: Cefizoxim100%, Ciprofloxcin 98%, Ceftazidim 82%, Tobramycin 47%,
and Amikacin 33%. And their resistance to Gentamycin was 97%, Penicillin 93%,
Cloxacillin 86%, and Erythromycin 62%. In anaerobic bacteria, susceptibility to
Ciprofloxacin was 100%, Ceftyzoxim 100, Ceftazidim 91% Rifampin 76%, Colistin
67%, and their resistance to Penicillin was 95%, Erythromycin 83%, Cloxacillin
85%. Susceptibility of both anaerobic and aerobic bacteria to Ceftizoxim was
100 %, so we suggest this drug for treatment of many skin infections.
Anaerobic bacteria are important because
they dominate the diagnose flora. They are commonly found in different
infections. Some of these infections are serious and have high mortality rate
(Brook, 1995; Finegold, 1995; Summanen et al, 1995). It has to be paid more
attention to anaerobic infections because special precautions are needed for
appropriate collection and transport of specimens. Isolation and identification
of anaerobic bacteria can be complex, difficult, labor-intensive, and
expensive. The majority of these infections have caused mixtures of numerous strains
of aerobic and anaerobic bacteria. Interpreting culture to establish the
extent, to which any one particular anaerobe in the mixture is contributing to
infection, is difficult (Brook et al, 1997; Wexler and Finegold, 1998).
Treatment considerations for these mixed anaerobic infections are difficult and
causing even more problem with increasing resistance among these groups of
organisms. A number of antimicrobials have poor or no activity against some
bacteria (Wexler et al, 1998; Chau, 1999; Nichols et al, 1999). Failure to
provide antibacterial coverage against the anaerobes in a mixed
aerobic-anaerobic infection may lead to inadequate response. This could, of
course, be attributed to another factor such as the possibility of an untrained
abscess (Holten and Onusko, 2000). The therapeutic approach in anaerobic
infections is complex and involves modification of the local environment of the
infected site and the use of appropriate antibacterial agents.
Surgical
management, particularly drainage and debridement is an important aspect of
treatment of the most anaerobic infections. In a large number of soft tissue
infections, anaerobes may play an important role. Among these are superficial
infections of the skin and skin structures such as cellulites, infected
cutaneous ulcer, infected sebaceous or inclusion cysts, hidradenitis
supportive, pyoderma, paronychia, and tropical ulcer (Goldstein et al, 2002). The choice of
single-agent therapy of mixed infections is ideally based on local data of
susceptibility patterns of the bacteria involved in these infections.
This descriptive study was performed at faculty of medicine
in medical university of shaheed Beheshti and medical sciences from March 2002
through 2003. In this research, 100 patients with skin infections including
samples of ulcer (in foot, gluteal, nose, under breast, knee elbow), abscesses
(from inguinal, neck, perianal, nose), pastula, acnes and bullea were examined.
Collecting was done with syringe and
swabs. All of specimens were transferred to transport media. Swab specimens
were homogenized in a small amount of broth. Aspirates were thoroughly mixed
before inoculation. For transport media Tripticase soy broth for aerobic
bacteria and Thioglycolate broth for anaerobic bacteria were used. Then we
cultured these specimens in blood agar, (with L-cysteine, yeast extract vitamin
k and hemin), selective media bile-esculin agar which is anaerobic blood agar
containing Kanamycin to inhibit facultative gram negative rods and Vancomycin
to inhibit gram positive bacteria, chocolate agar and Mac conkey agar, for
first screening. Therefore, we used 6 plates for each specimen; 3 plates for
aerobic condition that were examined after 24 h and 3 plates for anaerobic.
Plates must be immediately placed in anaerobic jars condition (jar with gas
pack generates H2 gas and a cold palladium catalyst converts
remaining O2 to water) and examined after 48-72 h. After growing of
the colonies, we stained colonies of bacteria with gram staining and determined
shape of bacteria. Then we used specific culture and test for identifying type
of bacteria. In the mean time we used aerobic and anaerobic condition. When we
identified type of bacteria which caused infections, we performed antibiogram
test by Kirby-Bauer method (gel diffusion test) in blood or chocolate agar with
Muller-Hinton base agar. After 24 h for aerobic and 48-72 h for anaerobic
bacteria, we reported susceptibility of bacteria to antibiotic disk.
We examined 100
samples from patients with ulcer (in foot, Gluteal, nose, under breast, knee,
and elbow), abscesses (from inguinal, neck, perianal, nose), pastula, acnes,
bullea. In our research, we examined 58 specimens from women (Figure 1) and 42 specimens from men
with age between 10-60 years old (Figure
2). Common aerobic and anaerobic facultative bacteria (Figure 3) were: Staphylococcus aureus (37.3%), non coagolase
Staphylococci (8.5 %), group A Streptococci (16.3 %), group D Enterococci
(5.7%), E.coli (15.6 %), Enterobacter-spp (5.6%), Citrobacter- spp (0.8%),
Pseudomonas aeruginosa (6.9%), Proteus-spp (2.7%), others (0.6%) (Figure 4).
Figure 1. The symptoms in infectious
skin in women
Figure 2. The age of patients with
skin infection
Figure 3. Microbiology of specimens
from patients with skin infection
Figure 4. The prevalence of aerobic
bacteria isolated from patients with skin infection
Predominant anaerobic
bacteria were: Peptostreptococcus-spp (42.5%), pigmented Prevotella and
Porphyromon-spp (5.4%), Fusobacterium (7.6%) Bacteroides-spp (23.2%),
Clostridium-spp (18.4%), Propionebacteriom acnes (2.1%), others (0.8%) (Figure 5).
Atibiogram test was
done on aerobic-anaerobic facultative bacteria.
Susceptibility
of these bacteria were as following: Cefizoxim100%, Ciprofloxcin 98%,
Ceftazidim 82%, Tobramycin 47%, and Amikacin 33%. And their resistance to
Gentamycin was 97%, Penicillin 93%, Cloxacillin 86%, and Erythromycin 62% (Figure 6). In anaerobic bacteria,
susceptibility to Ciprofloxacin was 100%, Ceftyzoxim 100, Ceftazidim 91%
Rifampin 76%, Colistin 67%, and their resistance to Penicillin was 95%,
Erythromycin 83%, Cloxacillin 85% (Figure
7). Susceptibility of both anaerobic and aerobic bacteria to Ceftizoxim was
100 %, so we suggest this drug for treatment of many infections.
Figure 5. The prevalence of anaerobic
bacteria isolated from patients with skin infection
Figure 6. The prevalence of antibiotic
susceptibility aerobic bacteria isolated from patients with skin infection
Figure 7. The prevalence of antibiotic susceptibility anaerobic bacteria isolated from patients with skin infection
Expecting exact correlation of laboratory
results with clinical outcome is not realistic. Infections involving anaerobes
are typically polymicrobial (Caceres et al, 1999; Bryskier, 2001;
Ueno et al, 2002); It is often not necessary to eradicate
all of the organisms to gain a cure. Appropriate surgical manipulation, the
patients general health status, and the microenvironment at the site of the infection
will have a significant impact on the outcome, regardless of whether a
particular isolate is susceptible to the antimicrobial. The aims of this study
were to determine the antimicrobial susceptibility pattern and to study the
role of bacteria which had been isolated from the cultures which had been taken
from different skin infections.
In many studies of skin and soft tissue,
Staphylococcus aureus was the most common pathogen. Group A Streptococci ranks
as a second common pathogen in gram positive cocci (Caceres et al, 1999; Chau,
1999; Goldstein et al, 2002; Ueno et al, 2002). In our study we found S.aureus (37.3%)
and streptococcus pygenes (16.3%). Other reports showed that the isolation
rates of Bacteroides Fragilis group organism have recently been increasing in
both primary and post operative infection (Caceres et al, 1999; Bryskier, 2001; Goldstein et al, 2002) and Peptosterptococci typically are the
most common isolated anaerobic bacteria (Wexler and Finegold, 1998; Wexler et
al, 1998; Chau, 1999). We isolated Peptostreptococci (43%) and Bacteroides
group organism (23.2%), which is as same as the other reports. Nevertheless,
accurate information regarding the efficacy of a certain agent in inhibiting or
killing the organism will certainly give useful clinical information for choice
of a therapeutic agent. A consensus group of infectious disease clinicians
concluded that in the most serious infections involving anaerobes,
susceptibility test results correlate with the clinical response. The mechanisms
by which anaerobic bacteria become resistant to blactames antibiotics are similar to those
described in aerobes and include the production of b lactames, changes in penicillin G binding
proteins, and changes in outer membrane permeability to b lactames (Holten and Onusko, 2000; Bryskier, 2001). Antibacteria therapy must cover
the key pathogens. Some compounds have significant activity against both
aerobic and anaerobic microorganisms (Caceres et al, 1999; Chau, 1999; Goldstein et al, 2002; Ueno et al, 2002). The antibiogram test of anaerobic and
aerobic isolated from Iranian patients with skin infection was determined by
using the most common antimicrobial agents used in Iran.
In our
survey, it was shown that anaerobic and aerobic facultative bacteria resistance
rate were: Cloxacillin (86%), Penicillin (93%), Gentamycin (97%) and
susceptibility were Ceftizoxim (100%), Ciprofloxacin (98%).
In anaerobic bacteria, resistance to
penicillin were (95%), Cloxacillin (85%), Erthromycin (83%), and susceptibility
to Ciprofloxacin, Ceftyzoxim were (100%), Ceftazidim (91%).
We concluded that, in skin infections
which are composed of both aerobic and anaerobic bacteria, Ciprofloxacin,
Ceftyzoxim were highly active drugs that could eradicate the major pathogens
bacteria found from skin infection in Iranian patients.
In conclusion, the results of the present
investigation show a high level of resistance in aerobes and anaerobes
bacteria. This may be the result of the extensive antibiotic used in patients.
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