Clindamycin Resistance In Staphylococci Research Articles

PHENOTYPIC DETECTION OF INDUCIBLE CLINDAMYCIN RESISTANCE IN STAPHYLOCOCCUS SPECIES ISOLATED FROM CLINICAL SAMPLES IN A TERTIARY CARE HOSPITAL

Introduction: Clindamycin is an effective drug used as an alternative to Vancomycin to treat skin and soft tissue infections caused by Staphylococcus spp. Reporting Staphylococcus as susceptible to Clindamycin without checking for inducible Clindamycin resistance may lead to therapeutic failure. Aim: To detect inducible Clindamycin resistance (MLSBi) among clinical isolates of Staphylococci by using a simple double-disc diffusion test (D-test). Methods: It was a prospective study conducted for 6 months from June 2022 to November 2022. All the Staphylococcal isolates from various samples were taken . Inducible clindamycin resistance (MLSBi) was detected by Erythromycin and Clindamycin disc approximation test (D-test) following CLSI guidelines. Results: A total of 216 Staphylococcus species were isolated from different samples. Out of the total samples Staphylococcus aureus were 42% and Coagulase negative Staphylococcus (CoNS) were 58%. Sensitivity to vancomycin, linezolid and teicoplanin were 100%. Methicillin resistance is seen in 21% of Staphylococcus aureus and 23% of CoNS. The different susceptibility patterns to clindamycin in both Staphylococcus aureus and CoNS were noted. Constitutive (MLSBc) phenotype was most prevalent (48%) followed by MS phenotype (43%) and inducible (MLSBi) phenotype (9%) among Erythromycin resistant Staphylococcus isolates. Sensitive phenotype (S) is detected in 27%. MLSBi was more frequent in Methicillin Resistant Staphylococcus aureus (MRSA) (28%) and MRCoNS (10%) than in MSSA (4%) and MSCoNS (2%). Conclusion: D-test should be included as a mandatory method in routine disc diffusion antimicrobial testing to detect inducible Clindamycin resistance in Staphylococci for the optimum treatment of patients.

Determination of Inducible Clindamycin Resistance Amongst Clinical Isolates of Methicillin-Resistant Staphylococcus aureus in Kaduna, Nigeria

For quite a long time, mainly due to fewer treatment options, Clindamycin have been regarded as an alternative drug to effectively manage all Staphylococcus aureus infections. Strains with inducible clindamycin resistance (iMLSB phenotype) raise concerns because therapeutic failure may occur during treatment. Clindamycin is mostly regarded in treating serious infections that cannot be treated by other antibiotics, as it may cause colitis or mild diarrhea. A double disc diffusion test (D-test) for detecting inducible resistance to clindamycin in erythromycin-resistant methicillin-resistant S. aureus was performed by placing a 15µg erythromycin disc in proximity to a 2µg clindamycin disc in adjacent positions. For erythromycin-resistant isolates, D-test can help to determine whether clindamycin could be used as a therapeutic option (reported as susceptible when the D-test is negative or reported as resistant when the D-test is positive). Twenty (20) out of the 30 (thirty) isolates collected were confirmed to be determined by D-test as per CLSI guidelines. Fifteen (15) isolates were D-test Negative, 5 were resistant to both Erythromycin and Clindamycin, and none was D-test positive. D-test should be included as a mandatory method in routine disc diffusion testing to detect inducible clindamycin resistance in staphylococci for the optimum treatment of patients.

Prevalence of Inducible Clindamycin Resistance in Staphylococcus: A Study from a Rural Teaching Tertiary Care Hospital in Southern Haryana

Introduction: Clindamycin is the most commonly prescribed Macrolides, Lincosamides and Streptogramin-B (MLSB) antibiotics to treat staphylococcal infections. It has excellent pharmacokinetic properties. Staphylococcus species shows either constitutive (MLSBc) or inducible (MLSBi) clindamycin resistance. Routine D-test recommended by Clinical Laboratory and Standard Institute (CLSI) can detect MLSBi phenotype and prevent treatment failure. Aim: To identify inducible clindamycin resistance in Staphylococci in a rural teaching Tertiary Care Hospital. Materials and Methods: It was a prospective, cross-sectional study. The clinical samples were cultured on blood agar and MacConkey agar. Staphylococcus isolates were identified based on their colony characteristics, gram stain and standard biochemical test. Antimicrobial susceptibility test was performed by Kirby Bauer’s disc diffusion method. To detect Methicillin resistance Cefoxitin disc (30 μg) was used. The isolates that were Erythromycin resistant and Clindamycin sensitive were further subjected to D test. CLSI 2019 guidelines were followed for performing the tests and its interpretation. Epi-info (version 7.2.3.1) Centre for Disease Control and Prevention (CDC), Atlanta, Georgia was used to analyse the data and interpretation of the results. Results: Total 150 Staphylococci were isolated from different samples. Staphylococcus aureus were 70% and Coagulase negative Staphylococcus (CoNS) were 30%. Pus was the most common specimen from which 43% Staphylococci was isolated. Sensitivity to vancomycin and linezolid were 100%. Staphylococcus aureus (38%) and CoNS (33%) were Methicillin resistant. Overall (63%) of staphylococcus isolates were resistant to erythromycin. The different susceptibility patterns to clindamycin in both Staphylococcus aureus and CoNS were noted. MLSBc phenotype was most prevalent (37.3%) followed by MS (13.4%) and MLSBi (12%) among erythromycin resistant Staphylococcus isolate. Sensitive (S) phenotype was detected in 56 (37%). MLSBi was more frequent in Methicillin Resistant Staphylococcus aureus (MRSA) (23%) and MRCoNS (27%) than in MSSA (5%) and MSCoNS (7%). Conclusion: D-test should be performed routinely to avoid false susceptible results leading to treatment failure.

Phenotypic and genotypic identification of <i>Staphylococcus aureus</i> resistant to clindamycin in Mansoura University Children Hospital, Egypt

Background : Clindamycin has been a good alternative drug to penicillins in the treatment of infections caused by Staphylococcus aureus but resistance to this agent has led to therapeutic failure. Inducible clindamycin resistance in staphylococci carrying erm genes may not be detectable by routine disk diffusion test. The objective of this study is to phenotypically detect clindamycin resistance in clinical S. aureus isolates and determine the prevalence of ermA, ermB and ermC carriage among these isolates. Methodology : A total of 230 non-duplicate S. aureus were isolated from children admitted to Mansoura University Children Hospital during the period January 2016 and June 2017 by conventional microbiology method. Invitro antibiotic susceptibility to selected antibiotics including erythromycin was performed by the disk diffusion technique. The „D-zone‟ test was used to phenotypically detect inducible clindamycin resistance. The presence of ermA, ermB and ermC genes was confirmed by multiplex polymerase chain reaction (m-PCR) assay. Results : One hundred and seven (46.6%) isolates were phenotypically resistant to erythromycin while 109 (47.3%) were methicillin (cefoxitin) resistant S. aureus (MRSA). The macrolidelincosamin-streptograminB (MLSB) phenotypes among the erythromycin resistant isolates were 47 (44%) inducible MLSB and 46 (43%) constitutive MLSB, while 14 (13.0%) were MS phenotype. Although, the MLSB phenotype was more predominant in MRSA (n=60, 56.1%) than MSSA (n=33, 30.7%) while the MS phenotype was more predominant in MSSA (n=9, 8.4%) than MRSA (n=5, 4.6%) isolates, the difference was not statistically significant (p=0.0777). The ermA (29.0%, n=31) and ermC (18.7%, n=20) were the most prevalent genes carried by the isolates while ermB was carried by a few (4.7%, n=5). Forty six (43%) isolates did not carry any detectable erm gene. Conclusion : In this study, both inducible and constitutive clindamycin resistance phenotypes were common among S. aureus isolates. Although the genetic basis for this may be attributed to carriage of ermA, ermB and ermC genes, a number of the resistant isolates did not carry any of these genes. Keywords : phenotypic, genotypic, macrolide-lincosamide-streptogramin B, S. aureus, children,

Inducible Clindamycin Resistance in Methicillin Resistant Staphylococcus aureus

The resistance to antimicrobial agents among staphylococci is an increasing problem. This has led to renewed interest in the usage of macrolide-lincosamide-streptogramin B (MLSB) antibiotics to treat Staphylococcus aureus infections. In vitro routine tests for clindamycin susceptibility may fail to detect inducible clindamycin resistance thus necessitating the need to detect such resistance by a simple D-test on routine basis. The objective of this study was to investigate S. aureus collected isolates for MLSB phenotypes, in particular inducible clindamycin resistance (MLSBi). Methods: Four hundred and forty six S.aureus isolates from samples were evaluated and inducible resistance to clindamycin was detected by D-test as per CLSI guidelines (2012). Results: Among 224 isolates of staphylococci studied, 101 (21.4%) were methicillin-resistant S. aureus (MRSA) and 123 (26.1%) were methicillin-sensitive Staphylococcus aureus (MSSA). Of the 224 staphylococcal isolates 62 (27.7%) were resistant to erythromycin of which 10 (4.46%) showed inducible clindamycin resistance and belonged to the MLSBi phenotype. Among the 10 MLSBi phenotype 7 (6.93%) were MRSA and 3 (2.44%) were MSSA. Conclusion: D-test should be included as a mandatory method in routine disc diffusion testing to detect inducible clindamycin resistance in staphylococci for the optimum treatment of patients.

Inducible clindamycin resistance among clinical isolates of Staphylococcus aureus

Objective: The aim of the study was to detect the presence of inducible clindamycin resistance among clinical isolates of Staphylococcus aureus. Background: The resistance to antimicrobial agents among staphylococci is an increasing problem. This has led to renewed interest in the usage of macrolide–lincosamide–streptogramin B (MLSB) antibiotics to treat S. aureus infections. The resistance to macrolide can be mediated by the msrA gene coding for efflux mechanism or by the erm gene encoding for enzymes that confer inducible or constitutive resistance to MLSB antibiotics. Materials and methods: Ninety staphylococcal isolates were collected and were tested for antibiotic susceptibility using the disk diffusion method. Inducible resistance to clindamycin in S. aureus was tested by using the double disk diffusion test as per CLSI guidelines. Results: Inducible MLSBresistance (EryRClinInd) was seen in 7/90 (7.7%) isolates, the constitutive phenotype of MLSBresistance (EryRClinR) was detected in 6/90 (6.6%) isolates, and the MSBphenotype (EryRClinS) was seen in 34 (37.7%) isolates. In these isolates, inducible clindamycin resistance was detected in 4.3% (3/70) of S. aureus and 20% (4/20) of coagulase-negative staphylococci. Conclusion: This study showed that the double disk diffusion test should be used as a mandatory method in routine disk diffusion testing to detect inducible clindamycin resistance in staphylococci for the optimum treatment of patients.

A Study of Inducible Clindamycin Resistance in Staphylococci in a Tertiary Care Hospital in Western Uttar Pradesh

Aim: The aim of this study was to determine inducible clindamycin resistance in erythromycinresistant, clindamycin-sensitive staphylococcal strains isolated from clinical specimens. Material and Method: A total of 108 erythromycin-resistant, clindamycin-sensitive staphylococcal isolates from various clinical specimens were tested using D-test according to CLSI guidelines. Result: A total of 23 (21.3%) staphylococcal isolates were found to be D-test positive and demonstrated inducible clindamycin resistance (iMLSB phenotype). MRSA isolates showed highest percentage (25.8%) of inducible clindamycin resistant phenotypes. Conclusion: Inducible clindamycin resistance should be checked in staphylococcal isolates before administering clindamycin therapy in staphylococcal infections as it can lead to clinical failure.

Inducible clindamycin resistance among clinical isolates of Staphylococcus aureus

Introduction: The resistance to antimicrobial agents among staphylococci is an increasing problem. This has led to renewed interest in the usage of macrolide-lincosamide-streptogramin B (MLSB) antibiotics to treat Staphylococcus aureus infections. Clinical failure has been reported due to multiple mechanisms that confer resistance to MLSB antibiotics. The present study was aimed to detect inducible clindamycin resistance among S. aureus isolates and to study the relationship between clindamycin and methicillin resistance. Materials and Methods: During a period of 1 year, a total of 593 S. aureus isolates from various clinical specimens were included in the study. Antimicrobial susceptibility test was done by Kirby-Bauer's disc diffusion method as per Clinical and Laboratory Standards Institute (CLSI) guidelines. For detection of inducible clindamycin resistance, D test using erythromycin and clindamycin as per CLSI guidelines was performed, and three different phenotypes were interpreted as methicillin-sensitive (MS) phenotype (D test negative), inducible MLSB (iMLSB) phenotype (D test positive), and constitutive MLSB phenotype. Results: Of the total 593 S. aureus isolates, majority were obtained from pus (31.1%) followed by blood and body fluids (27.3%). All the isolates were sensitive to vancomycin, teicoplanin, and linezolid. Out of 306 (51.7%) erythromycin resistant isolates, 280 (91.5%) were methicillin-resistant S. aureus (MRSA) and 26 (8.5%) were methicillin-sensitive S. aureus (MSSA). iMLSB phenotype in 33.3%, MS phenotype in 44.8%, and constitutive MLSB phenotype was observed in 21.9% of isolates. Inducible clindamycin resistance was almost equal among MRSA and MSSA isolates. Conclusion: D test should be included as a mandatory method in routine disc diffusion testing to detect inducible clindamycin resistance in staphylococci for the optimum treatment of patients.

Inducible clindamycin resistance in staphylococcus isolates from a tertiary care hospital in Eastern India

Purpose: The increasing resistance to antimicrobial agents among Staphylococci has led to renewed interest in the usage of macrolide-lincosamide-streptogramin B (MLS B ) antibiotics to treat Staphylococcus aureus ( S. aureus ) infections. The resistance to macrolide can be mediated by msr A gene coding for the efflux mechanism or via erm gene encoding for enzymes that confer inducible or constitutive resistance to MLS B antibiotics. In vitro routine tests for clindamycin susceptibility may fail to detect inducible clindamycin resistance due to erm genes resulting in treatment failure, thus necessitating the need to detect such resistance by a simple D test on a routine basis. Materials and Methods: One hundred and ninety-five S. aureus isolates were subjected to routine antibiotic susceptibility testing including cefoxitin (30 μg) by a modified Kirby Bauer disk diffusion method. Inducible resistance to clindamycin in S. aureus was tested by the D test as per CLSI guidelines. Results: Thirty-three (16.9%) isolates showed inducible clindamycin resistance, 45 (23%) showed a constitutive resistance while remaining 33 (16.9%) showed the MS phenotype. Inducible resistance and constitutive resistance were found to be higher in MRSA compared to MSSA (22.6%, 35.5%, and 11.8%, 11.8%, respectively). Conclusion: Clindamycin is kept as a reserve drug and is usually advocated in severe MRSA infections depending upon the antimicrobial susceptibility results. This study showed that a D test should be used as a mandatory method in routine disk diffusion testing to detect inducible clindamycin resistance in Staphylococci for the optimum treatment of patients.

Inducible clindamycin resistance in Staphylococci: Should clinicians and microbiologists be concerned?

The increasing incidence of a variety of infections due to Staphylococcus aureus and the expanding role of community-associated methicillin-resistant S. aureus has led to an emphasis on the need for safe and effective agents to treat both systemic and localized Staphylococcal infections. Several newer antimicrobial agents are available for treatment of systemic Staphylococcal infections, but their use may be limited by the relatively high cost of these agents or the need forparenteral administration. Clindamycin has been used successfully to treat soft-tissue and musculoskeletal infections due to MRSA, in adults and children. However, concern over the possibility of the emergence of clindamycin resistance during therapy has discouraged some clinicians from prescribing that agent. Simple laboratory testing (e.g., the erythromycin-clindamycin 'D-zone' test) can separate strains that have the genetic potential (i.e., the presence of erm genes) to become resistant during therapy, from strains that are fully susceptible to clindamycin.

Prevalence of inducible clindamycin resistance in clinical isolates of coagulase negative staphylococci at a tertiary care hospital

Background : Coagulase negative staphylococci (CoNS) are an important group of multi-drug resistant nosocomial pathogens. Clindamycin resistance in staphylococci can be either constitutive or inducible. Clindamycin has been used successfully to treat pneumonia, soft-tissue and musculoskeletal infections due to methicillin-resistant CoNS (MRCoNS) in adults and children, but this matter is complicated by the possibility of inducible macrolide-lincosamide streptogramin B resistance (MLSBi). Aims: The present study was aimed to determine the incidence of inducible clindamycin resistance in CoNS isolates in our hospital using D-test, relationship between MRCoNS and MLSBi isolates, association of MLSBi isolates with community or nosocomial setting and treatment options for these isolates. Materials and Methods : A total of 250 consecutive, non-duplicate strains of CoNS were isolated from various clinical specimens, both from indoor and outdoor patients. After determining methicillin resistance, D-test was performed on all erythromycin-resistant and clindamycin-sensitive isolates to detect inducible clindamycin resistance. Results : Among 250 CoNS isolates, 89 (35.6%) were found to be MRCoNS and 20% had MLSBi phenotype. MRCoNS showed higher inducible as well as constitutive resistance (p Conclusions : Clindamycin is a useful drug in the treatment of staphylococcal infections. Hence, routine testing of staphylococcal isolates for inducible clindamycin resistance is strongly recommended.

Collaborative Evaluation of an Erythromycin-Clindamycin Combination Well for Detection of Inducible Clindamycin Resistance in Beta-Hemolytic Streptococci by Use of the CLSI Broth Microdilution Method

Constitutive or inducible clindamycin resistance can occur in beta-hemolytic streptococci due to the presence of an erm gene. The Clinical and Laboratory Standards Institute (CLSI) has recommended a disk approximation test (D-zone test) with erythromycin and clindamycin disks and a single-well broth test combining erythromycin and clindamycin for detection of inducible clindamycin resistance in staphylococci, but only a disk approximation test for the beta-hemolytic streptococci. This collaborative study assessed two different erythromycin and clindamycin concentration combinations in single wells (1 μg/ml + 0.25 μg/ml [erythromycin plus clindamycin] and 1 μg/ml + 0.5 μg/ml) with three different brands of Mueller-Hinton broth supplemented with 3% lysed horse blood for testing of frozen panels prepared for this study. All labs performed the D-zone test as described by the CLSI. A total of 155 nonduplicate streptococcal isolates (50 group A, 48 group B, 28 group C, and 29 group G isolates) were tested; 99 isolates showed inducible resistance by the D-zone test. There were some differences noted based upon the test medium. The sensitivity of the erythromycin plus clindamycin combination of 1 μg/ml + 0.25 μg/ml was 91 to 100%, while the sensitivity of the combination of 1 μg/ml + 0.5 μg/ml was 95 to 100%. Specificity overall was 98%. The slightly higher sensitivity of the combination of 1 μg/ml + 0.5 μg/ml is recommended. This study has demonstrated that a single-well microdilution test incorporating erythromycin and clindamycin in combination is a sensitive and specific indicator of inducible clindamycin resistance and could be included in routine test panels.

Inducible Clindamycin Resistance in Staphylococcus aureus Isolated from Clinical Samples

Introduction:The resistance to antimicrobial agents among Staphylococci is an increasing problem. This has led to renewed interest in the usage of Macrolide-Lincosamide-Streptogramin B (MLSB) antibiotics to treat Staphylococcus aureus (S. aureus) infections. The resistance to macrolide can be mediated by msr A gene coding for efflux mechanism or via erm gene encoding for enzymes that confer inducible or constitutive resistance to MLSBantibiotics. In vitro routine tests for clindamycin susceptibility may fail to detect inducible clindamycin resistance due to erm genes resulting in treatment failure, thus necessitating the need to detect such resistance by a simple D test on a routine basis.Materials and Methods:One hundred and ninety S. aureus isolates were subjected to routine antibiotic susceptibility testing including oxacillin (1 µg) and cefoxitin (30 µg) by modified Kirby Bauer disc diffusion method. Inducible resistance to clindamycin in S. aureus was tested by ‘D test’ as per CLSI guidelines.Results:Twenty (10%) isolates showed inducible clindamycin resistance, 18 (9%) showed constitutive resistance while remaining 16 (8%) showed MS phenotype. Inducible resistance and constitutive resistance were found to be higher in MRSA as compared to MSSA (20%, 16% and 6%, 6%, respectively).Conclusion:Clindamycin is kept as a reserve drug and is usually advocated in severe MRSA infections depending upon the antimicrobial susceptibility results. This study showed that D test should be used as a mandatory method in routine disc diffusion testing to detect inducible clindamycin resistance in Staphylococci for the optimum treatment of patients.

Performance of the VITEK2 System for Detection of Inducible Clindamycin Resistance in Staphylococci

Background: The Clinical and Laboratory Standards Institute (CLSI) recommends testing for inducible clindamycin resistance in clindamycin non-resistant and erythromycin resistant (CNR-ER) staphylococci by using a D-zone test. Recently, the VITEK2 system was developed to detect inducible clindamycin resistance in staphylococci. We evaluated the performance of the VITEK2 system by comparing it with a D-zone test. Methods: In detecting inducible clindamycin resistance, a total of 142 clinical isolates of staphylococci were tested by using the VITEK2 Antimicrobial Susceptibility Test (AST)-P601 card (bioMerieux, Marcy l’Etoile, France) and the D-zone test. Of the 142 isolates of staphylococci tested, 114 were CNR-ER staphylococci [40 coagulase-negative staphylococci (CoNS), 74 Staphylococcus aureus] and 28 were staphylococci, either resistant or susceptible to clindamycin and erythromycin (1 CoNS and 27 S. aureus). Results: Of the 114 CNR-ER staphylococci, 98.6% (73/74) of S. aureus and 32.5% (13/40) of CoNS were inducible clindamycin resistant according to the Dzone test. Overall sensitivity and specificity of the VITEK2 system were 98.8% (85/86) and 98.2% (55/56) respectively, and the agreement between the VITEK2 system and the D-zone test was 98.6% (140/142). Conclusion: The VITEK2 system shows high concordance with a D-zone test. The inducible clindamycin resistance in staphylococci can be detected easily and conveniently by the VITEK2 system. (Korean J Clin Microbiol 2010;13:157-161)

Detection and prevalence of inducible clindamycin resistance in staphylococci

Staphylococcus aureus and coagulase-negative staphylococci (CNS) are recognized as causing nosocomial and community-acquired infections in every region of the world. The resistance to antimicrobial agents among staphylococci is an increasing problem. Clindamycin (CL) is considered to be one of the alternative agents in these infections. This study demonstrates a simple, reliable method (double-disc diffusion test) for detecting inducible resistance to CL in erythromycin-resistance (ER-R) isolates of S. aureus and CNS. A total of 883 (52.3%) isolates of S. aureus and 804 (47.7%) isolates of CNS were selected from recent (2003-2005) clinical isolates recovered in the laboratory of the authors; duplicate isolates were not included. A total of 214 (12.6%) S. aureus and 308 (18.3%) CNS isolates were selected based on ER-R and CL sensitivity using standard National Committee for Clinical Laboratory Standards disc diffusion testing. A total of 1687 staphylococcal isolates were included, consisting of 27.5% meticillin-resistant S. aureus, 24.8% meticillin-sensitive S. aureus, 36.1% meticillin-resistant CNS and 11.6% meticillin-sensitive CNS isolates: 30.9% of staphylococcal isolates (214 S. aureus and 308 CNS) that were erythromycin resistant and CL sensitive were tested for inducible resistance using the D-test. A D-shaped zone around the CL was observed for 70.9% of staphylococcal isolates (81.8% of S. aureus isolates and 63.3% of CNS isolates) with an ER-R and a clindamycin-sensitive (CL-S) phenotype. The organism was positive for inducible clindamycin resistance (CL-R). There was a 21.9% level of inducible macrolide-lincosamide-streptogramin B resistance phenotype among all the staphylococcal isolates. When the S. aureus and CNS strains among all the staphylococcal isolates were compared statistically, inducible CL-R in CNS strains was determined to be 23% more positive (P=0.028, odds ratio 0.77, 95% confidence interval 0.61-0.98). When a statistical comparison was performed among ER-R but CL-S staphylococcal isolates inducible CL-R in S. aureus strains was determined to be 2.6 times more positive (P=0.000, odds ratio 2.6, 95% confidence interval 1.68-4.04). A simple, reliable method of detecting inducible resistance to CL in ER-R isolates of S. aureus and CNS is described. Clinical microbiology laboratories should use the double-disc diffusion test as standard practice with all ER-R staphylococci. CL should not be used in patients with infections caused by inducibly resistant staphylococcal isolates. Therapeutic failures may thus be avoided.

Prevalence of Inducible Clindamycin Resistance in Staphylococcal Isolates at a Korean Tertiary Care Hospital

Clindamycin resistance in Staphylococcus species can be either constitutive or inducible. Inducible resistance cannot be detected by the conventional antimicrobial susceptibility test. In this study, we determined the prevalence of inducible clindamycin resistance in staphylococcal isolates at a Korean tertiary care hospital. Between February and September 2004, 1,519 isolates of Staphylococcus aureus and 1,043 isolates of coagulase-negative staphylococci (CNS) were tested for inducible resistance by the D-zone test. Overall, 17% of MRSA, 84% of MSSA, 37% of MRCNS, and 70% of MSCNS were susceptible to clindamycin. Of the erythromycin non-susceptible, clindamycin-susceptible isolates, 32% of MRSA, 35% of MSSA, 90% of MRCNS, and 94% of MSCNS had inducible clindamycin resistance. Inducible clindamycin resistance in staphylococci was highly prevalent in Korea. This study indicates importance of the D-zone test in detecting inducible clindamycin resistance in staphylococci to aid in the optimal treatment of patients.

Incidence of inducible clindamycin resistance in staphylococci: first results from Turkey

In total, 408 staphylococcal isolates were tested for inducible clindamycin resistance (ICR) by the disk-diffusion induction test (D-test). ICR was detected in 5.7% of 105 methicillin-resistant Staphylococcus aureus (MRSA) isolates, 3.6% of 111 methicillin-susceptible S. aureus isolates, 30.8% of 94 methicillin-resistant coagulase-negative staphylococcal (CoNS) isolates, and 11.2% of 98 methicillin-sensitive CoNS isolates. All MRSA isolates that were erythromycin-resistant and clindamycin-susceptible were positive by the D-test. The same results were obtained with an azithromycin instead of an erythromycin disk. All isolates were susceptible to quinupristin-dalfopristin. The cost-benefit of the d-test should be evaluated locally after determining the incidence of the different resistance phenotypes.

Selection of Strains for Quality Assessment of the Disk Induction Method for Detection of Inducible Clindamycin Resistance in Staphylococci: a CLSI Collaborative Study

A nine-laboratory collaborative study was conducted to select positive and negative quality assessment control strains for the detection of inducible clindamycin resistance in staphylococci. Four strains of Staphylococcus aureus were tested as unknowns on 10 different days in each laboratory using the recently recommended CLSI (formerly NCCLS) disk diffusion method and the inoculum purity control method. Strains contained either macrolide-lincosamide-streptogramin B (MLSB) resistance genes encoded by erm(A) or erm(C) or a macrolide resistance efflux pump encoded by msr(A). Based upon the results of this study, strain UT 32 (now designated ATCC strain BAA-977) containing erm(A) is recommended as the positive control organism for inducible clindamycin resistance. Strain UT 25 (now designated ATCC BAA-976), which harbors the efflux pump encoded by msr(A), is recommended as the negative control organism.

Inducible Clindamycin Resistance in Staphylococci: Should Clinicians and Microbiologists be Concerned?

The increasing incidence of a variety of infections due to Staphylococcus aureus--and, especially, the expanding role of community-associated methicillin-resistant S. aureus (MRSA)--has led to emphasis on the need for safe and effective agents to treat both systemic and localized staphylococcal infections. Unlike most previously noted strains of health care-associated MRSA, community-acquired MRSA isolates are often susceptible to several non- beta -lactam drug classes, although they are usually not susceptible to macrolides. Several newer antimicrobial agents and a few older agents are available for treatment of systemic staphylococcal infections, but use may be limited by the relatively high cost of these agents or the need for parenteral administration. Inexpensive oral agents for treatment of localized, community-acquired MRSA infection include clindamycin, trimethoprim-sulfamethoxazole, and newer tetracyclines. Clindamycin has been used successfully to treat pneumonia and soft-tissue and musculoskeletal infections due to MRSA in adults and children. However, concern over the possibility of emergence of clindamycin resistance during therapy has discouraged some clinicians from prescribing that agent. Simple laboratory testing (e.g., the erythromycin-clindamycin "D-zone" test) can separate strains that have the genetic potential (i.e., the presence of erm genes) to become resistant during therapy from strains that are fully susceptible to clindamycin.

Detection of inducible clindamycin resistance of staphylococci in conjunction with performance of automated broth susceptibility testing.

This study has shown that inducible clindamycin resistance in staphylococci can be detected by disk testing on sheep blood agar inoculum purity plates used with the bioMerieux VITEK 2. Tests of 150 erythromycin-resistant isolates correlated with standard D-zone tests on Mueller-Hinton agar and with PCR for erm(A), erm(C), and msr(A).