Constitutive Clindamycin Resistance Research Articles

Spectrum of constitutive and inducible clindamycin resistance in Staphylococcus spp isolated from clinical samples and its relation with methicillin resistance.

Backgound: Increasing Staphylococcal infections with changing patterns of antimicrobial resistance has led to renewed interest in macrolide-lincosamide-streptogramin group B (MLS B ) antibiotic. Misuse of MLS B antibiotics has increased resistance of Staphylococcusspp. to these drugs. Failure to detect inducible clindamycin resistance leads to therapeutic failure. Determine the prevalence of constitutive and inducible clindamycin resistance in clinical isolates of Staphylococcus spp. Ascertain the relationship between methicillin-resistance in Staphylococcus spp with constitutive and inducible clindamycin resistance. Methods: Prospective study was carried over a period of six months with 722 clinical specimens. A total of 184 Staphylococcal isolates were identified. Staphylococcal isolates were speciated as S aureus, S epidermidis and S saprophyticus. Antibiotic susceptibility testing was done by Kirby-Bauer’s disc diffusion method using cefoxitin, erythromycin, and clindamycin. A disc approximation test was performed for detection of inducible clindamycin resistance for all strains resistant to erythromycin but sensitive to clindamycin. Results: Out of 184 staphylococcal isolates, 128 (69.5%) S aureus and 56 (30.4%) Coagulase negative Staphylococcus spp were identified. 114 (61.9%) of the isolates were susceptible to both clindamycin and erythromycin. Overall 70 (38.04%) isolates were resistant to erythromycin. Out of these,38 (54.2%%) of strains depicted cMLS B phenotype being resistant to both erythromycin and clindamycin.20 (28.5%) isolates showed inducible clindamycin resistance while 12(17.1%) isolates indicated MS phenotype. Percentage of both constitutive and inducible clindamycin resistance was found to be higher in methicillin resistant staphylococcal isolates than methicillin sensitive isolates. Conclusions: We recommend that the clinical microbiology laboratories should test the isolates for inducible clindamycin resistance by D test, for all isolates that appear erythromycin resistant and clindamycin susceptible in vitro.

High prevalence of clindamycin resistance in Staphylococcus aureus blood culture isolates in São Paulo, Brazil.

BACKGROUND:Clindamycin has become an important antimicrobial option for the treatment of Staphylococcus aureus. However, little is known about the current patterns of clindamycin-susceptibility in S. aureus invasive isolates, both in our country and in other developing countries in the world.AIMS:The aim of this study was to determine the prevalence of constitutive and inducible clindamycin resistance in methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) blood culture isolates in São Paulo, Brazil.MATERIALS AND METHODS:From July 2011 to June 2012, all S. aureus isolates from blood cultures collected at our hospital were included in the study. Antimicrobial susceptibility testing was performed according to recommendations of the Clinical and Laboratory Standards Institute.RESULTS:Total prevalence of clindamycin resistance was 68%, including 7.2% with inducible resistance. In MRSA resistance rate was 90.8% whereas in MSSA the rate was 32.7%.CONCLUSIONS:Our high prevalence of clindamycin resistance highlights the importance of performing D-test in a routine base, as well of maintaining continued surveillance for the prevalence of clindamycin resistance.

Prevalence of methicillin-resistant Staphylococcus aureus carriage on admission among patients attending regional hospitals in Dar es Salaam, Tanzania

BackgroundMethicillin-resistant Staphylococcus aureus (MRSA) is a major pathogen responsible for hospital and community acquired infection. Colonization with MRSA is associated with a high risk of developing infection. This study aimed to determine the rate of MRSA carriage on admission and the associated risk factors among patients attending regional hospitals, in Dar es Salaam, Tanzania.ResultsA total of 258 patients were included in this study. Nasal swabs were collected on admission to the hospital and after 48 h of hospital stay for detection of MRSA. Of 258 patients enrolled, 89 (34.5%) were colonized with S. aureus and out them 22 (24.7%) were carriers of MRSA, giving an overall MRSA nasal carriage rate of 8.5% (22/258). One patient acquired MRSA while admitted in the hospital. Most of the S. aureus isolates 85 (95.5%) were resistant to penicillin. Resistance to gentamycin, ciprofloxacin, kanamycin, linezolid and mupirocin were 14.6, 11.2, 11.2, 3.4 and 1.1%, respectively. The prevalence of inducible clindamycin resistance, constitutive clindamycin resistance, MS phenotype (resistance to erythromycin alone), and multidrug resistance was 21.3, 3.4, 12.4, and 16.9%, respectively. We observed a statistically significant association between MRSA and multiple drugs resistance among S. aureus isolates (p = 0.001). Of the risk factors investigated none were statistically significant associated with MRSA.ConclusionThere is a high prevalence of MRSA among patients on admission at the two municipal hospitals in Dar es Salaam. The high prevalence of MRSA and the increased rates of resistance to commonly used antimicrobials among MRSA isolates call for attention to the importance of including the screening of MRSA in our hospitals setting in order to prevent further spread of MRSA strains to other patients and to the communities. Control and prevention strategies should be emphasized including decolonization.

Prevalence of Inducible Clindamycin Resistance of Staphylococcus aureus in Hospitalized Patients in Tertiary Care Hospital

Background: Methicillin resistant Staphylococcus aureus (MRSA) has emerged as one of the most common pathogen isolated from patients with very few drugs available for their treatment. Clindamycin is a good alternative optional drug for the treatment of these infections. In vitro routine testing may fail to detect such resistance. Thus it is important to detect such resistance by simple D test. Material and Methods: 300 staphylococcal isolates where isolated from clinical samples by conventional microbiological methods. Of these 208(69.33%) were identified as Staphylococcus aureus. Methicillin resistance and inducible clindamycin resistance was detected by cefoxitin disk diffusion method and D test as per CLSI guidelines respectively. Results: 135 (64.9%) were MRSA and 73 (35.09%) were Methicillin sensitive Staphylococcus aureus (MSSA), 45(21.63%) isolates showed inducible clindamycin resistance, 19(9.1%) showed constitutive clindamycin resistance, 112(53.84%) showed MS phenotype whereas 32(15.38%) were erythromycin sensitive. Inducible clindamycin resistance and constitutive clindamycin resistance was higher in MRSA than in MSSA (25.92%, 11.11% and 13.69%, 5.47% respectively). Conclusion: D test should be done as routine test in all Microbiology laboratory for detection of true resistance of clindamycin among staphylococcal isolates.

Phenotypic study of Macrolide-Lincosamide-Streptogramin B Resistance in Staphylococcus aureus and their relationship with Methicillin-Resistant Staphylococcus aureus (MRSA) at Tertiary Care in Eastern Nepal

Background Resistance to antimicrobial agents is prevalent among Staphylococci. This has led to wide uses of macrolide-lincosamide-streptogramin B (MLSB) antibiotics to Staphylococcus aureus (S. aureus) infections. MLSB though chemically distinct, have similar target site and mode of action. The multiple mechanisms are responsible for resistance to MLSB antibiotics which can lead to clinical failure. The aim of the study was to investigate the frequency of inducible and constitutive clindamycin resistance among clinical isolates of S. aureus and their relationship with Methicillin-resistant Staphylococcus aureus (MRSA).Material & Methods A total of 336 unique Staphylococcus aureus isolates from different clinical samples obtained from patients were studied. Antibiotic susceptibility test was performed by Kirby- Bauer disc diffusion method. “D test” was performed to detect inducible clindamycin resistance as per CLSI guidelines. MRSA was detected using Cefoxitin (30μg) and results were interpreted according to CLSI criteria.Results Inducible clindamycin resistance was seen in 45 (13.39%), constitutive clindamycin resistance was seen among 58 (17.26%) while MS phenotype was observed among 38(11.30%) of isolates. Inducible resistance as well as constitutive resistance was higher among MRSA as compared to MSSA (21.11%, 4.48% and 21.11%, 12.82%respectively).Conclusion The Successful use of clindamycin for the treatment of infection caused by S. aureus can be predicted based on the result of simple and inexpensive D test.Journal of Nobel Medical CollegeVolume 5, Number 1, Issue 8, January-July 2016, 1-5

Detection of inducible and constitutive clindamycin resistance among Staphylococcus aureus isolates in a tertiary care hospital, Eastern India.

Introduction:Clindamycin is an excellent drug for skin and soft tissue Staphylococcus aureus infections, but resistance mediated by inducible macrolide-lincosamide-streptogramin B (iMLSB) phenotype leads to in vivo therapeutic failure even though they may be in vitro susceptible in Kirby–Bauer disk diffusion method.Objective:The study was aimed to detect the prevalence of iMLSB phenotype among S. aureus isolates by double disk approximation test (D-test) in a tertiary care hospital, Eastern India.Materials and Methods:A total of 209 consecutive S. aureus isolates were identified by conventional methods and subjected to antimicrobial susceptibility testing by Kirby–Bauer disk diffusion method. Erythromycin-resistant isolates were tested for D-test.Results:From 1282 clinical specimens, 209 nonrepeated S. aureus isolates were obtained. Majority of isolates 129 (61.7%) were methicillin-resistant S. aureus (MRSA). There was statistically significant difference between outpatients 60.1% and inpatients 39.9% (P < 0.0001). From 209 S. aureus isolates, 46 (22%) were D-test positive (iMLSB phenotype), 41 (19.6%) were D-test negative (methicillin sensitive [MS] phenotype), and 37 (17.7%) were constitutively resistant (constitutive macrolide-lincosamide-streptogramin B phenotype). The incidence of inducible, constitutive, and MS phenotype was higher in MRSA isolates compared to MS S. aureus (MSSA). The constitutive clindamycin resistance difference between MSSA and MRSA isolates were found to be statistically significant (P = 0.0086).Conclusion:The study revealed 22% of S. aureus isolates were inducible clindamycin resistant, which could be easily misidentified as clindamycin susceptible in Kirby–Bauer disk diffusion method. Therefore, clinical microbiology laboratory should routinely perform D-test in all clinically isolated S. aureus to guide clinicians for the appropriate use of clindamycin.

Antibiotic Resistance Patterns and Related Mobile Genetic Elements of Pneumococci and β-Hemolytic Streptococci in Thai Healthy Children.

Transmission of antibiotic resistance genes among Streptococcus pneumoniae and beta-hemolytic streptococcus (BHS) was generally associated with transmissible genetic elements. The objectives of this study were to investigate carriage rate, antibiotic resistance and related mobile genetic elements of pneumococci and BHS from school-children. The pneumococci and BHS were recovered from 220 Thai school-children, and then tested for antibiotic susceptibility pattern by disc diffusion. Antibiotic resistance genes and related genetic elements were detected by PCR with specific primers. A total of 77 pneumococcal isolates were resistant to erythromycin (42%), tetracycline (44%), clindamycin (8%), or penicillin (3%). Fifty-four BHS isolates were resistant to erythromycin (28%), tetracycline (52%), or clindamycin (13%). All isolates tested were 100% sensitive to penicillin and levofloxacin. Among erythromycin-resistant streptococcal isolates showed different phenotypes of clindamycin resistance. It was found that isolated pneumococci showed constitutive clindamycin resistance (19%), and inducible clindamycin resistance (12%). The BHS isolates exhibited constitutive clindamycin resistance (40%), and inducible resistance (20%) phenotypes. The predominant erythromycin resistance genes in pneumococci and BHS were mefE and ermB, while the most common tetracycline resistance gene in this population was tetM. Furthermore, almost all erythromycin- and tetracycline-resistant streptococci (97%) mainly contained various genetic elements, including mega elements and six different transposon types (Tn2009, Tn2017, Tn917, Tn3872, Tn6002 and Tn916). Therefore, carriages of pneumococci and BHS with multidrug resistance in children might be important reservoirs of antibiotic-resistance genes carried by transposons. Tn916-like elements could lead to dissemination of the antibiotic resistance genes among genus streptococcus in human oral cavity and nasopharynx.

Clindamycin resistance among Staphylococcus aureus strains in Israel: implications for empirical treatment of skin and soft tissue infections.

The objectives of this study were to characterize isolates of Staphylococcus aureus obtained from skin and soft tissue infections in the community in Israel and to document the sensitivity patterns for commonly used antimicrobial agents. The susceptibilities of S. aureus isolates from skin and soft tissue infections in the community in Israel were reviewed to determine the appropriate empirical therapy for these infections. A total of 7221 isolates were collected during the period 2009-2012; 39% were from children (age 0-18 years). In children, S. aureus oxacillin resistance dropped from 8.4% to 3.8% (p=0.073). While inducible clindamycin resistance increased slightly from 20% to 25%, there was a prominent increase in constitutive clindamycin resistance from 0.1% to 26.8% (p=0.012). In adults, oxacillin resistance increased from 16% to 23% (p<0.001) and constitutive clindamycin resistance increased notably from 5% to 29% (p<0.001). These findings demonstrate a dramatic increase in clindamycin resistance among S. aureus isolates and suggest against the usage of clindamycin as empirical treatment for suspected S. aureus infections in Israel. Beta-lactam anti-staphylococcal agents may be given as empirical treatment for children, but should be considered according to risk factors for adults in Israel.

Inducible and constitutive clindamycin resistance in Staphylococcus aureus in a northeastern Indian tertiary care hospital.

Staphylococcus aureus is one of the most common pyogenic bacteria. They are notorious for developing prompt resistance to newer antimicrobials. With increasing incidence of methicillin-resistant S. aureus (MRSA) isolates, the treatment options are also becoming limited. Clindamycin is an excellent drug for skin and soft tissue infections, but resistance mediated by the inducible phenotype (iMLS(B)) leads to in vivo therapeutic failure even though there may be in vitro susceptibility. The double disk approximation test (D-test) can reliably detect the presence of such isolates. This study was aimed to detect and report the prevalence of the iMLS(B) phenotype in NEIGRIHMS, a tertiary care center in Northeast India. A total of 243 consecutive isolates were subjected to routine identification tests followed by antimicrobial sensitivity testing. Erythromycin-resistant isolates were tested for inducible resistance phenotype by the D-test. Among strains tested, 95 (39%) were erythromycin resistant. Twenty-six (10.7%) isolates were D-test positive (iMLS(B) phenotype), 41 (16.88%) were constitutively resistant (cMLS(B) phenotype), and 28 isolates (11.52%) were found to be negative by D-test. The incidence of both inducible and constitutive phenotypes was higher in MRSA isolates compared to methicillin-sensitive S. aureus (MSSA) isolates. This study revealed a moderate prevalence of the inducible clindamycin phenotype in the staphylococcal isolates tested. Clinical microbiology laboratories in areas of high MRSA prevalence should consider performing the D-test routinely. This will help prevent prescription of drug(s) whose therapeutic efficacy is doubtful.

Prevalence of Mupirocin Resistance Among Staphylococci, its Clinical Significance and Relationship to Clinical Use.

Introduction:Mupirocin competitively inhibits bacterial isoleucyl transfer-RNA synthetase and inhibit bacterial protein synthesis. Widespread usage and over the counter availability of the drug has resulted in resistance among Staphylococcus species.Objectives:This study aimed to determine the overall prevalence of mupirocin resistance among staphylococci. Correlate clinical significance of mupirocin resistance and its relationship to clinical use.Methods:Consecutive, nonrepetitive, clinical isolates of Staphylococcus aureus (n = 98), and coagulase-negative staphylococci (CoNS) (n = 45) from skin and soft-tissue infections between January 2014 and June 2014 were studied. Antibiotic susceptibility testing was done according to Clinical and Laboratory Standards Institute guidelines. Low- and high-level mupirocin resistance was screened by using 5 µg and 200 µg discs respectively and confirmed by agar dilution. Annual consumption of mupirocin was studied and correlated with resistance.Results:High-level mupirocin resistance was found in 8.2% S. aureus and 15.6% of CoNS, while low-level mupirocin resistance was found in 17% S. aureus and 8.9% CoNS. High-level mupirocin resistance was more common in methicillin-sensitive S. aureus isolates when compared with methicillin-resistant S. aureus isolates (P < 0.05). Mupirocin resistant S. epidermidis were associated with methicillin resistance and constitutive clindamycin resistance.Conclusion:High prevalence of mupirocin resistance was found in the present study. Increased prevalence of mupirocin resistance among community-acquired staphylococci demands the judicious use of the drug in the community.

Inducible and constitutive clindamycin resistance in Staphylococcus aureus: an experience from Western Nepal

Abstract Objective: This study aimed to determine prevalence of inducible and constitutive clindamycin resistance among clinical S. aureus isolates and also study their association with methicillin resistance. Methods: A cross-sectional study including 140 non-duplicate isolates of S. aureus was done. Isolates were identified by standard microbiological methods and methicillin resistance was detected by cefoxitin disc diffusion method. Inducible clindamycin resistance was detected by D-test. Results: Prevalence of inducible and constitutive clindamycin resistance was 12.10% and 7.90% respectively. Constitutive and inducible resistance was associated with MRSA. An unusual phenotype, erythromycin sensitive and clindamycin resistance, was detected in 2 MRSA isolates. Conclusions: Inducible and constitutive clindamycin resistance is low in our setting. Constitutive and inducible resistance was associated with MRSA. However the trends in resistance vary in different places. D-test reporting should be done routinely which will allow clinicians to opt for clindamycin judiciously and avoid potential treatment failure. Keywords: Clindamycin resistance, MLSBi, D-test, MRSA, Nepal

STUDY OF COMMUNITY AND HOSPITAL ASSOCIATED METHICILLIN RESISTANT STAPHYLOCOCCUS AUREUS WITH SPECIAL REFERENCE TO INDUCIBLE CLINDAMYCIN RESISTANCE IN A TERTIARY CARE HOSPITAL

MRSA has been considered a major nosocomial pathogen in healthcare facilities but recently it has been observed emerging in t he community as well. Clindamycin is a preferred therapeutic option in the treatment of both methicillin susceptible and resistant staphylococcal infections. The present study was aimed to determine the incidence of constitutive and inducible clindamycin resistance among Community - associated methicillin - resistant Staphylococcus aureus (CA - MRSA) and Hospital - associated methi cillin - resistant Staphylococcus aureus (HA - MRSA) isolates. A 600 staphylococcal strains were isolated from various clinical specimens. Antibiotic susceptibility tests were performed using standard method. Methicillin resistance was detected by cefoxitin (3 0 ug) disc diffusion test using Mueller - Hinton Agar. D - test was performed on all erythromycin resistant and clindamycin sensitive isolates to detect inducible clindamycin resistance. MRSA was documented in 28 % amongst 600 isolates of S. aureus. Out of the se 64.66 % and 35.33 % isolates of S. aureus were hospital associated and community associated respectively . Among these, 216 S. aureus were resistant to Erythromycin, 61 isolates were MRSA. Out of these 42 (68.85 %) were HA - MRSA and 19 (31.14) were CA - MRS A. We observed 3 (15.78 %), 16 (84.21 %), 0 % were iMLSB, MS phenotype and cMLSB in CA - MRSA respectively. 18 (42.85 %) iMLSB, 21 (50 %) MS phenotype and 3 (7.14 %) cMLSB observed in HA - MRSA. Our study suggested that MLSB resistance in S. aureus should be u nder constant surveillance in every country and region. The D - test for detection of iMLSB resistance should be carried out routinely in laboratories so as to prevent therapeutic failures.

Induced and Constitutive Clindamycin Resistance in Staphylococcus spp. Strains Isolated from a Neonatal Intensive Care Unit

Induced and Constitutive Clindamycin Resistance in Staphylococcus spp. Strains Isolated from a Neonatal Intensive Care Unit

Inducible Clindamycin Resistance among Clinical Isolates of Staphylococcus aureus from Sub Himalayan Region of India.

Clindamycin is an alternative antibiotic in the treatment of Staphylococcus aureus (S.aureus) infections, both in infections by methicillin susceptible and resistant (MSSA and MRSA) strains. The major problem of use of clindamycin for staphylococcal infections is the presence of inducible clindamycin resistance that can lead to treatment failure in such infections. To determine inducible and constitutive clindamycin resistance among clinical isolates of S. aureus in a tertiary care centre of sub Himalayan region of India. A total of 350 isolates of S. aureus from various clinical samples were subjected to routine antibiotic sensitivity testing by Kirby Bauer disc diffusion method. Methicillin resistance was detected by cefoxitin (30μg) disc. All isolates were subjected to inducible clindamycin resistance was by Clinical Laboratory Standards Institute (CLSI) recommended D test. Among 350 S.aureus isolates, 82 (23.42%) were MRSA and 268 (76.57%) were MSSA. Erythromycin resistance was detected in 137 (39.14%) isolates. Erythromycin resistance in MRSA and MSSA was 71.6% and 29.36% respectively. Overall clindamycin resistance was seen in 108 (30.85%) isolates. Constitutive MSLB phenotype predominated (29.62% MRSA; 13.38% MSSA) followed by iMLSB (28.39% MRSA; 9.29% MSSA) and MS phenotypes (13.58% MRSA; 6.69%MSSA). Both inducible and constitutive clindamycin resistance was significantly higher (p=0.00001, 0.0008 respectively) in methicillin resistant strains than in methicillin susceptible strains. The present study gives a magnitude of clindamycin resistance among clinical isolates of S. aureus from this region of the country. Our study recommends routine testing of inducible clindamycin resistance at individual settings to guide optimum therapy and to avoid treatment failure.

Phenotypic detection and incidence of inducible clindamycin resistance among Staphylococcus aureus from tertiary care hospital

Background: Among few therapeutic alternatives available for treatment of erythromycin resistant Staphylococcus aureus infections, clindamycin has several advantages but major barrier in its usage is development of resistance especially inducible resistance due to erm genes resulting in treatment failure. In vitro routine tests for clindamycin susceptibility may fail to detect such resistance which can be detected by simple D test. Hence the present study was undertaken to detect incidence of inducible resistance to clindamycin in erythromycin resistant S. aureus isolates by D test and to study the relationship between clindamycin and methicillin resistance. Methods: 330 S. aureus isolates were subjected to routine antimicrobial susceptibility test by Kirby-Bauer’s disc diffusion method using various antimicrobial agents. Erythromycin resistant isolates were studied for detection of inducible and constitutive clindamycin resistance by D test according to CLSI guidelines. Results: Out of 152 erythromycin resistant S. aureus , 46 (30.2%) isolates showed inducible clindamycin resistance, 54 (35.5%) showed constitutive resistance while 52 (34.2%) showed MS phenotype. The percentage of inducible and constitutive resistance was more among MRSA (33.3% and 46.6%) than MSSA (25% and 19.3%) while the percentage of MS phenotype was more among MSSA (54.8%) than MRSA (20%). Conclusions: D test should be used in routine disc diffusion testing for the detection of inducible clindamycin resistance for the proper treatment of the patient.

Patterns of Constitutive and Inducible Clindamycin Resistance in Staphylococcus aureus Isolated from Clinical Samples by D-test Method, Shiraz, Southwest of Iran

Background: Macrolides, Lincosamides and type B Streptogramins (MLSB) are commonly used for the treatment of Staphylococcal infections. Inducible MLSB resistance (iMLSB) cannot be identified by standard methods of antibiotic susceptibility testing. D-test appears to be a reliable indicator of iMLSB strains. The aim of this study was to determine the prevalence of Clindamycin resistance phenotypes in Staphylococcus aureus (S.aureus) isolated from clinical samples in Shiraz, southwest of Iran.Materials and Methods: This cross-sectional study was performed on a total of 302 S. aureus isolates which were collected from two teaching hospitals in Shiraz during 2012. Methicillin resistant Staphylococcus aureus (MRSA) were screened based on their resistance to 30μg Cefoxitin disk. 168 Methicillin-sensitive Staphylococcus aureus (MSSA) and 134 MRSA isolates were tested in this study. The isolates were tested for susceptibility to Clindamycin (2 µg) and Erythromycin (15 µg) by Clinical and Laboratory Standards Institute (CLSI) recommended disk diffusion test.Results: Of 302 collected S. aureus isolates, 134 (44.4%) were MRSA and 168 (55.6%) were MSSA. Inducible MLSB resistance was observed in 10.4% of all recovered MRSA and 3% of all MSSA isolates. The majority of MRSA isolates (77.6%) constituted MLSB phenotype (cMLSB); this phenotype was seen in 4.1% of our tested MSSA isolates. Finally, 12.0% of MRSA isolates and 89.9% of MSSA showed sensitivity to both Erythromycin and Clindamycin.Conclusion: Different resistance patterns in hospitals indicated that performing routine D-test for S. aureus infections is highly recommended for each medical center. [GMJ. 2014;3(4):216-21]&#x0D;

High Nasal Carriage of Methicillin-ResistantStaphylococcus aureusAmong Healthy Tanzanian Under-5 Children

This study aimed to determine the prevalence of Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) carriage, risk factors of colonization and antimicrobial susceptibility patterns of S. aureus strains. The study was conducted at the Muhimbili National Hospital in Dar es Salaam, Tanzania. Nasal swabs were obtained from children and S. aureus was isolated and identified using conventional culture methods. MRSA was screened and confirmed using the cefoxitin disk and multiplex real-time polymerase chain reaction, respectively. Antibiotic susceptibility was performed using the Kirby-Bauer disk diffusion method. MRSA isolates were further characterized by pulsed field gel electrophoresis (PFGE) profiling. Of 285 children included in the study, S. aureus was detected in 114 (40%). Of the 114 isolates, 12 (10.5%) were MRSA. PFGE results showed that these MRSA isolates are epidemiologically unrelated. Resistance of all S. aureus to trimethoprim-sulfamethoxazole, tetracycline, gentamicin, and ciprofloxacin was 65.8%, 23.7%, 27.2%, and 4.4%, respectively. No resistance to vancomycin was found. The prevalence of inducible clindamycin resistance, constitutive clindamycin resistance, MS phenotype (resistance to erythromycin alone), and multidrug resistance was 16.7%, 1.8%, 14.0%, and 16.8%, respectively. None of the risk factors examined was found to be significant. This is the first report of S. aureus and nasal carriage of MRSA and a high rate of S. aureus carriage was found in Tanzanian under-5 children. The study findings support the need for proper health education and effective infection control measures for healthcare workers.

Presence of Inducible Clindamycin Resistance Phenotype andermGenes in FoodborneStaphylococcus aureusIsolates

The resistance of foodborne Staphylococcus aureus isolates to antimicrobial agents is an increasing problem. In this study, 154 S. aureus food isolates were examined on the basis of inducible clindamycin resistance and the presence of ermABC genes. Furthermore, the genetic relatedness of S. aureus strains having inducible and constitutive clindamycin resistance was investigated by pulsed-field gel electrophoresis. Inducible clindamycin resistance was determined in five strains using the D-test. Only S. aureus strain HE7A showed constitutive resistance. Polymerase chain reaction results demonstrated that all constitutive and inducible clindamycin resistant strains contained only the ermC gene. However, the presence of the ermC gene was also detected in three strains without inducible or constitutive resistance. Nucleotide variations on the sequences of ermC genes were also determined. Pulsed-field gel electrophoresis analysis of two groups of S. aureus strains (S4BY, PY62A, PY38BY/S and S35A, S35B) with inducible resistance demonstrated 100% homology, but the other susceptible and ermC gene carrying S. aureus strains showed different band patterns with 44-88% homology. This is the first study reporting inducible clindamycin resistance in foodborne S. aureus isolates in Turkey.

Incidence of constitutive and inducible clindamycin resistance among hospital-associated Staphylococcus aureus.

Clindamycin is one of the important alternative antibiotics in the therapy of Staphylococcus aureus infections. Clinical failure of clindamycin therapy has been reported due to multiple mechanisms that confer resistance to macrolides, lincosamides and Streptogramin B (MLSB) antibiotics. In vitro routine tests for clindamycin susceptibility may fail to detect inducible clindamycin resistance due to erm genes, resulting in the treatment failure. Although data from the developed countries have shown to be enormity of the problem, data from the developing countries are lacking. The aim of the study was to distinguish different resistance phenotypes in erythromycin-resistant S. aureus by a simple double-disc diffusion test (D test). A total of 153 S. aureus isolates were subjected to routine antibiotic susceptibility testing, including cefoxitin disc (30 μg) and by oxacillin screen agar. Inducible clindamycin resistance was tested by ‘D test’ as per CLSI guidelines. Odds ratios (OR) and 95 % confidence intervals (95 % CI) were calculated. P values were calculated using SPSS (version 18). Among 153 S. aureus isolates, 42 (27.45 %) were resistant to methicillin, whereas 111 (72.54 %) were methicillin susceptible. Out of the 63 (41.17 %) erythromycin-resistant S. aureus isolates, 14 (9.15 %) showed inducible resistance [P = 0.0002, odds ratio (OR) 18.30; 95 % confidence interval (CI) 8.72–25.77), 20 (13.07 %)] showed constitutive resistance (P = 0.002, OR 14.38, 95 % CI 5.33–21.49), while the remaining 29 (18.95 %) showed inducible phenotype. Inducible and constitutive resistance was found to be higher in MSSA when compared with MRSA. Clinical laboratories should perform D test routinely to guide the clinicians about the inducible clindamycin resistance and to prevent misuse of antibiotics.

The prevalence of Inducible and Constitutive Clindamycin Resistance Among the Nasal Isolates of Staphylococci

One of the important sources of Staphylococci which causes nosocomial infections, is the nasal carriage of Staphylococci among Health Care Workers (HCWs). The commonest antibiotic which is preferred for the treatment of the methicillin and multi drug resistant Staphylococcal infections is clindamycin. The inducible clindamycin resistance in Staphylococci is not detected by the routine antibiotic susceptibility testing and it results in treatment failures. The present study was undertaken to know the prevalence of constitutive and inducible clindamycin resistance and its correlation with the methicillin resistance among the nasal isolates of Staphylococci which were obtained from different HCWs. Nasal swabs were collected from 206 HCWs and they were processed. The Staphylococci which were isolated were tested for methicillin resistance by using cefoxitin (30 μg) discs. The inducible clindamycin resistance was tested by using erythromycin (15 μg) and clindamycin (2μg) discs and the D test according to the CLSI guidelines. Inducible clindamycin resistance was seen in 21(16.40%) of the S.aureus and 14 (7.56%) of the coagulase negative Staphylococcal isolates. Constitutive clindamycin resistance was seen in 23(17.96%) of the S.aureus and 43(23.24%) of the coagulase negative Staphylococcal isolates. The inducible and constitutive clindamycin resistance was more common among the methicillin resistant Staphylococcal isolates. The prevalence of inducible and constitutive clindamycin resistance in the nasal Staphylococcal isolates which were obtained from the HCWs was high, especially among the methicillin resistant Staphylococci. The D test which is recommended by the CLSI should be routinely done to detect inducible clindamycin resistance, to prevent treatment failures.