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Methicillin-resistant Staphylococcus aureus (MRSA) in the
community – laboratory based study
Selma Uzunović-Kamberović1, Suad Sivić2 1 Laboratory for Sanitary and Clinical Objective To determine the occurrence and antibiotic resis-
Microbiology, 2 Department of social medicine, tance of community-acquired methicillin-resistant Staphylo- Cantonal Public Health Institution Zenica, coccus aureus (MRSA) isolates. Methods used In 2003-2005,
Bosnia and Herzegovina consecutive samples of nasal, throat, eye, ear and genitouri- nary tract s�abs, s�abs of �ound infections and soft and skin tissue infections and samples of sputum obtained from out- patients submitted to the Laboratory �ith clinical indications �ere analyzed for the presence of Staphylococcus aureus. The Corresponding author: disc diffusion method using Mueller-Hinton agar (Oxoid, Selma Uzunović-Kamberović, Besingstoke, UK) �as used to test against nine antimicrobi- Cantonal Public Health Institution, als. Oxacillin-resistance �as confirmed by E-test (AB Biodisc, Laboratory for Sanitary and Clinical Solna, S�eden). Results A total of 1583 (11.3%) nonduplicate
S. aureus isolated from 13 937 samples. MRSA �as detected Fra Ivana Jukića 2, 72000 Zenica, in 63 (4.1%) of S. aureus isolates. MRSA isolates more fre- Bosnia and Herzegovina quently from infected genitourinary tract and �ounds than other sites (p<0.0001). The patients in both age groups ≥65 and 0-6 years of age �ere more frequently infected �ith MRSA than patients of other age groups (p=0.02). Statisti- cal y significant differences in susceptibility rates bet�een MSSA and MRSA isolates �ere found for all antibiotic tested (p=0.0053 to p<0.000). MRSA isolates �ere more frequently multidrug resistant (MDR) than MSSA isolates (p=0.0009). SCCmec type IV or V phenotype �as detected in 30 (47.6%) of MRSA isolates. Conclusion Although lo� MRSA prevalence
�as noted, the presence of SCCmec type IV/V phenotypes in the community is of particular concern. Effective control of dissemination of MRSA throughout the community �ill likely require effective control and monitoring of nosocomial MRSA transmission.
Received: 25. 02. 2007.
Key words: S. aureus, MRSA, MSSA, SCCmec, Resistance,
Accepted: 24. 05. 2007.
Acta .Medica .Academica .2007; .36: .3-9 defined CA-MRSA strains carry SCCmec type IV or V (14), �hereas the majority of Methicillin-resistant S. aureus (MRSA) has HA-MRSA strains carry SCCmec type I, II traditional y been considered a hospital- or III (13).
acquired pathogen (HA-MRSA) in patients Recently t�o MRSA strains isolated �ith established risk factors (recent hospi- from the noses and hands of food handlers talization or surgery, dialysis, residence in a prompted a retrospective revie� of Labora- long-term care facility, and presence of a per- tory outpatient records identifying patients manent ind�elling catheter or percutaneous from �hom S. aureus �as isolated from any medical device) at the time of culture) (1, 2). site in the period 2003-2005. The objective But more recently MRSA has emerged as a of this study �as to report the frequency of highly virulent organism in the community S. aureus isolation in outpatients from the of patients �ithout established risk factors Zenica-Doboj Canton, Bosnia and Herze- for the acquisition of MRSA (3-5). More- govina, according to methicillin resistance, over, the spread of community-acquired origin of isolates, age and gender of patients, methicillin resistant S. aureus (CA-MRSA) and to determine the antibiotic susceptibil- into hospitals has been reported, causing ity patterns. For comparison, S. aureus iso- nosocomial infections (6, 7). lates obtained from food handlers and food Most studies have been based on hospi- products (routinely analysed in the Labora- talized patients, or patients upon admission tory during 2003-2004) �ere also included to hospital, �hich has probably resulted in in the study.
an overestimation of the true prevalence of CA-MRSA (8, 9). Accordingly, epidemio- logical definitions of CA-MRSA have com- monly been based on the timing of isolation of MRSA in relation to the time of admission The Laboratory for Sanitary and Clinical to hospital, so that MRSA isolates �ere clas- Microbiology of the Cantonal Public Health sified as community-acquired if they �ere Institution in Zenica covers a population isolated �ithin the first 48-72 h of hospital- of 331,229 in the Zenica-Doboj Canton ization, or if they �ere isolated in a commu- (112,471 males and 218,758 females). In the nity setting (10). 2003-2005 period, 13,937 consecutive sam- Reported prevalence rates of CA-MRSA ples of nasal, throat, eye, ear and genitouri- vary �idely among studies, in part because nary tract s�abs, s�abs of �ound infections of the use of different definitions used to and soft and skin tissue infections (SSTIs) distinguish bet�een CA-MRSA and HA- and sputum obtained from outpatients sub- MRSA, but also because of the different set- mitted to the Laboratory �ith clinical indi- tings in �hich studies have been performed. cation, �ere analyzed for the presence of S. Only a limited number of studies has been performed in outpatient settings and among Sterile cotton s�abs �ere used. S�abs randomly selected healthy community �ere streaked onto sheep blood agar (5% members (4, 5, 11, 12). columbia agar base) for detection of gram- A combination of molecular typing tech- positive bacteria, and incubated overnight niques �ith good resolving po�er provides a at 37°C. Morphological y distinct colonies reliable means of analysing isolates of MRSA �ere tested for the production of bound to determine their genetic relatedness (13, coagulase (Staphylase Test, Oxoid, Basing- 14). Recent studies have indicated that �ell- stoke, UK) and identified as S. aureus.
Selma .Uzunović-Kamberović .et .al .: .MRSA .in .the .community The disc diffusion method using Muel- ler-Hinton agar (Oxoid, Besingstoke, UK) �as used to test against nine antimicrobials A total of 1583 (11.3%) nonduplicate S. au- (Oxoid, UK). Clinical and Laboratory Stan- reus isolates from 13 937 consecutive outpa- dards Institute (CLSI) criteria �ere used tients presented to the Laboratory because of different clinical symptoms �ere collected for the interpretation of antibiotic sensitiv- during 2003-2005. MRSA �as detected in 63 ity testing results (15). Oxacillin-resistant (4.1%) of S. aureus isolates and in 0.6% of strains �ere further tested by the E-test submitted samples. S. aureus �as identified (AB Biodisc, Solna, S�eden). Isolates �ere in 322 out of 4439 (7.3%) nasal s�abs of food considered resistant to oxacillin if the MIC handlers, five of �hich �ere MRSA (1.6%). exceeded 4 mg/L. The isolates characterized MRSA �as isolated in 0.1% of submitted as intermediate by both disk diffusion and food handler samples. Thirty five S. au- E-test �ere considered susceptible. Staphy- reus strains �ere isolated from 6517 (0.5%) lococcus aureus ATCC 25923 control strains food samples, and t�o of them (5.7%) �ere �ere used. Isolates resistant to oxacillin and MRSA. All S. aureus isolated from ice cream susceptible to gentamicin, clindamycin, and samples obtained from local patisseries and trimethoprim-sulfamethoxasole �ere des- fast food restaurants.
ignated as having a SCCmec type IV or V Table 1 sho�s the distribution of methi- cillin susceptible S. aureus (MSSA) and The name, surname, ID, address, gender MRSA isolates according to the origin of and age of the patient (0-6, 7-14, 20-64, >64 years), date of isolation, specimen number, MRSA isolates �ere more frequently iso- source of isolates and susceptibility results lated from genitourinary tract and �ounds of Staphylococcus aureus isolates �ere re- than from other sites (p<0.0001). corded, as �ell as the number of specimens The patients in age groups ≥65 and 0-6 submitted during the study.
years of age �ere more frequently infect- For comparison, S. aureus strains isolated ed �ith MRSA than patients of other age from 4439 successive nasal s�abs of food- groups (p=0.02) (Table 2). Female patients handlers and 6517 samples of food collected �ere significantly more often infected �ith during routine mandatory examination in MRSA than male patients (p=0.003) (data the Laboratory during 2003-2004 �ere also not sho�n). The median age of patients in- included in this study. Microbiological anal- fected �ith MRSA and MSSA �as 30.09 and ysis of food products �as performed accord- ing to the standards and legal regulations of Statistical y significant differences in sus- the Republic/Federation of Bosnia and Her- ceptibility rates bet�een MSSA and MRSA zegovina. Routine antimicrobial susceptibil- clinical isolates �ere found for all antibiotic ity testing of S. aureus isolates from these tested (p=0.0053 to p<0.0001) (Table 3). No samples �as terminated at the end of 2004, resistance to vancomycin or ciprofloxacin and for that reason the data for 2005 �ere �as detected in MRSA isolates. MRSA iso- not available.
lates �ere more frequently multidrug resis- The significance of differences in resis- tant (MDR) than MSSA isolates (p=0.0009). tance rates �as determined by means of According to origin, MDR �as more often the χ2 test and Fisher exact test for indepen- detected in �ound infection isolates, 28.6%, dence. A statistical y significant difference than in isolates from GU tract and nose, �as defined as a p value of <0.05 and 95% 12.5% and 0.6%, respectively, but �ith no statistical y significant difference (data not Acta .Medica .Academica .2007; .36: .3-9 Table .1 .Distribution .of .MRSA .and .MSSA .clinical .isolates .of .different .origin .in .the .2003-2005 .period .
Origin .of .
No .of .MRSA .with . Total Site .of .isolation No .of .samples .
No .of .MSSA No .of .MRSA SCCmec .IV .or .V .
S . aureus .(% .of .
submitted .samples) Genito-urinary .tract Food .handlers Nose Table .2 .Distribution .of .MRSA .and .MSSA .clinical .isolates .according .to .age .groups Number .(%) .of .patients Table .3 .Antimicrobial .resistance .patterns .of .MSSA .and .MRSA .isolates .in .the .2003-2005 .of .different .origin Percentage .of .resistance .to .antimicrobial .agents* Origin .of .isolates TET CIP CLI SXT CHL 1091 .(71 .8%) 429 .(28 .2) 23 .(1 .5) food .handlers .(317) 47 .(74 .6) 10 .(15 .9) food .handlers .(5) MSSA, .methicillin-sensitive .Staphylococcus aureus; .MRSA, .methicillin-resistant .Staphylococcus aureus; .S, .susceptible; .
R, .resistance .to .one .or .more .antimicrobials; .MDR .(multidrug .resistance), .resistance .to .three .or .more .antimicrobials .
*Antimicrobial .agents .tested: .vancomycin .(VAN), .gentamicin .(GEN), .kanamycin .(KAN), .erythromycin .(ERY), .tetracycline .
(TET), .ciprofloxacin .(CIP), .clindamycin .(CLI), .trimethoprim-sulfamethoxasole .(SXT), .chloramphenicol .(CHL) sho�n). No MDR �as detected in MSSA famethoxasole) �as detected in 30 (47.6%) and MRSA isolated from food handlers or of MRSA isolates. These MRSA phenotypes food products.
�ere significantly more often isolated from SCCmec type IV or V phenotype (isolates GU tract, �ounds and nose than from eyes resistant to oxacillin and susceptible to genta- (p=0.0005), but they �ere not isolated from micin, clindamycin, and trimethoprim-sul- throat, sputum or ear (Table 1). Selma .Uzunović-Kamberović .et .al .: .MRSA .in .the .community Susceptibility results for MRSA demon- The finding of 30 MRSA isolates sho�ing strated that the prevalence of resistance to good sensitivity to antibiotics other than ciprofloxacin and erythromycin �as as high beta-lactams and the lo� prevalence of as 80% and 90%, respectively (22, 23). Fluo- multidrug resistance (MDR) in MRSA sug- roquinolone resistance emerged very rapidly gests the presence of true CA-MRSA in our in HA-MRSA in the years after �idespread population (2-4, 16) Multidrug resistance utilization of these agents (23-25). No resis- characterizes nosocomial y acquired MRSA tance to fluoroquinolones �as noted in this strains isolated from patients �ith identified study in MRSA isolates of any origin inves- tigated, but interestingly, it �as detected in Nasal carriage of S. aureus is an impor- MSSA isolated from clinical samples and tant risk factor for infections by this organ- ism in both community and hospital settings We found 47.6% MRSA isolates having (16). Health-care exposure is significantly the SCCmec type IV / V phenotype, �hich is associated �ith MRSA carriage (10, 18). In typical for CA-MRSA isolates (7). All MRSA our study MRSA �as detected in 0.6% of isolated from food handlers and food prod- clinical samples submitted to our Laborato- ucts (ice cream) �ere SCCmec type IV or ry, �hich is in agreement �ith colonization V phenotype. SCCmec type IV/V type has reported among community members �ith- increased mobility and therefore greater out healthcare contacts in the USA (0.2%) potential for horizontal spread to diverse S. and Europe (0.7%) (10, 19). aureus genetic backgrounds, compared �ith It has been documented that CA-MRSA other SCCmec types (13, 14). We did not infections have been increasing among adults perform genotype confirmation of SCCmec and children (4, 20). The results of the pres- type IV or V phenotype, but according to ent study have also sho�n that MRSA more the high correlation bet�een the genotype often infected the oldest (≥65) and youngest and phenotype �e could assume that at least (0-6) age groups of patients than other age some of these MRSA strains are generated in groups. Therefore, microbiologic culture and antimicrobial susceptibility testing �ould be Our investigation has some limitations. recommended to guide treatment.
This is a retrospective study �ith a relatively The prevalence of colonization of both small sample size and accordingly, a small S. aureus and MRSA in food handlers and number of MRSA �ere analysed. Addition- their appearance in food products �as lo� al y, molecular analysis �as not perfomed and in agreement �ith the prevalence of S. and a risk factors involved in acquisition of aureus and MRSA infections in our region. MRSA infections �re not investigated. Also, Reportedly, MRSA-contaminated food can data on the prevalence of HA-MRSA in this be a vehicle of outbreaks affecting lo�-risk region are missing. But, since �e found that persons �ithin the community and the food 25.4% (16/63) MRSA isolates �ere ful y �as contaminated by an asymptomatic car- susceptible to all antibiotic tested and 30 rier (21). There �ere no S. aureus foodborne (47.6%) MRSA isolates had SCCmec IV/V outbreaks noted in this period.
phenotype �e could estimate that MRSA The spectrum of illness is similar for generated in the communitya might be pres- MRSA and MSSA infections in our com- ent in this region.
munity, but �e found that MRSA �ere more The origin of CA-MRSA strains is still the often isolated from the GU tract and �ound subject of debate. Only studies based on ap-
infections than from other sites.
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