Detection Of Inducible Clindamycin Resistance Research Articles

Nasal carriage of methicillin and inducible clindamycin resistant Staphylococcus aureus among healthcare workers in a tertiary care hospital, Kathmandu, Nepal

Introduction and Objectives: Transmission of methicillin-resistant Staphylococcus aureus (MRSA) from healthcare workers is one of the most frequent causes of nosocomial infections globally. There is a significant burden of nosocomial MRSA infections in low and low-middle income countries (LMICs), including Nepal. The present study investigated the rate of nasal carriage of MRSA among the healthcare workers in a tertiary care hospital, in Kathmandu, Nepal with emphasis on inducible macrolide-lincosamide-streptogramin B (iMLSB) resistance. Material and method: The study was conducted at Star Hospital, Lalitpur, Nepal, from September 2022 to November 2022. Healthcare workers (HCWs) working at the diffeerent departments of the hospital were enrolled. Nasal swabs from both anterior nares of HCWs were collected aseptically and cultured on Mannitol Salt agar. S. aureus was identified by Gram stain and standard biochemical tests. Antibiotic susceptibility of S. aureus was performed by disc diffusion method. MRSA isolates were detected phenotypically by disc diffusion method using cefoxitin disc (30 µg), and inducible clindamycin resistance was detected phenotypically by the D-zone test. Results: Total 105 HCWs were enrolled in the study. Out of 105 HCWs, 14 (13.3%) were positive for S. aureus among which 6 (5.7%) were MRSA carriers. The nasal carriage of MRSA was highest among doctors (16.7%) and the HCWs of the post-operative department (14.3%). All the isolated MRSA were susceptible to chloramphenicol and vancomycin. Inducible MLSB resistance was detected in 33.3% MRSA while the rate was 21.4% in all isolated S. aureus. Conclusion: The study demonstrated that HCWs could be the potential source of nosocomial infection by methicillin and inducible clindamycin resistant S. aureus. Thus, preventive measures should be initiated to mitigate the risk of its spread and the test for detection of inducible clindamycin resistance should be incorporated into the routine antibiotic susceptibility testing in hospital settings. IMC J Med Sci. 2024; 18(1):005. DOI: https://doi.org/10.55010/imcjms.18.005 *Correspondence: Gaurab Pandey, Non-Communicable Disease Laboratory, National Public Health Laboratory, Teku, Kathmandu, 44600, Nepal; E-mail: pandeygaurab67@gmail.com

Agreement between Azithromycin and Erythromycin to Determine Inducible Clindamycin-Resistant Phenotypes in Staphylococcus aureus Isolates

Abstract Objectives To evaluate agreement in the detection of inducible clindamycin resistance by test method using azithromycin disk with reference method using erythromycin disk and to determine prevalence of inducible clindamycin-resistant phenotypes among Staphylococcus aureus isolates. Materials and Methods A total of 133 nonduplicate isolates of S. aureus from clinical samples were included in this prospective study. Agreement between erythromycin (reference method) and azithromycin (test method) disks for detection of inducible clindamycin resistance in S. aureus isolates was assessed. Statistical Analysis Chi-square test was used for analyzing categorical variables (p < 0.05 was considered significant). Results The prevalence of inducible clindamycin resistance (iMLSB) was 15.8%. A 100% agreement was recorded between reference and test methods for detecting inducible clindamycin-resistant phenotypes. For the determination of constitutive-resistant phenotypes (cMLSB) among S. aureus isolates, the test method demonstrated an agreement of 94.1%. Conclusion The present study demonstrated an agreement in the identification of inducible clindamycin-resistant phenotypes among S. aureus isolates by both erythromycin and azithromycin disks.

Phenotypic characterization and Molecular detection of Inducible and Constitutive Clindamycin resistance among Staphylococcus aureus isolates in a Tertiary Care Hospital

Background: Staphylococcus aureus is Gram positive cocci. The pyogenic bacteria which is responsible for a variety of diseases that ranges in severity from mild skin and soft tissue infections to life-threatening conditions such as endocarditis, pneumonia, and sepsis. There is a scenario of increasing Methicillin-resistant Staphylococcus aureus (MRSA) infections, the macrolide-lincosamide-streptogramin B (MLSB) group of antibiotics they have different structure with same mechanism of action which serves as one good alternative. There is a frequency of increasing Methicillin Resistant Staphylococcus aureus (MRSA) infections and their change in antimicrobial resistance pattern. There is a concern about use of this antibiotic in the presence of Erythromycin resistance because of the possibility of inducible resistance among the members of Macrolide, lincosamide, Strepto-gramin B (MLSB) group. The invitro resistance exhibited by Staphylococcus aureus to erythromycin, Clindamycin, and other drugs of MLSB groups is due to the expression of ribosomal methylases(erm) genes. The detection of inducible Clindamycin resistance can limit the effectiveness of these drugs. Objective of the study: To isolate of Staphylococcus aureus from various clinical samples to differentiate between Methicillin resistant Staphylococcus aureus (MRSA) and Methicillin sensitive Staphylococcus aureus (MSSA) by conventional methods. To detect inducible and constitutive Clindamycin resistance in Staphylococcus aureus isolates by D test. To detect ermA gene responsible for resistance by PCR. Methodology: This cross sectional study was done for a period of six months. Totally 106 Staphylococcus aureus isolates was obtained various clinical samples were processed using standard guidelines. Result: From the 106 isolates of Staphylococcus aureus 67(63.3%) were MSSA and 39(36.7%) were MRSA. D-test was positive in n=9 of the n=21 MRSA and n=17 of the n=85 MSSA, which denotes inducible Clindamycin resistance. N- 9 of MRSA and n=13(22%) of MSSA showed Constitutional Clindamycin resistance. The statistics show that there is a significant Difference in constitutive resistance between MRSA and MSSA. In India ermA gene is most prevalent, out of 22 d-test positive n=13 ermA gene were detected (n=3-MRSA and n=10-MSSA) by using conventional PCR. Conclusion: The MLSB family of antibiotics is one such alternative and CD is preferred. Clinical microbiology laboratories should report inducible Clindamycin resistance in Staphylococcus aureus and D-test can be used as a simple, auxiliary and reliable method to Delineate inducible and constitutive Clindamycin resistance in routine clinical laboratories.

INDUCTION OF CLINDAMYCIN RESISTANCE IN CLINICAL ISOLATES OF STAPHYLOCOCCUS AUREUS FROM A TERTIARY CARE HOSPITAL.

Nowadays in Staphylococcus aureus isolates resistant to lincosamide, macrolide and streptogramin B (MLSB) group of antibiotics are expanded. Therefore, clindamycin is preferred drug for the treatment of infections caused by S. aureus, but due to change in sensitivity patterns of clindamycin it is leading to treatment failure. The three resistance phenotypes of MLSB antibiotics are iMLSB (inducible resistance) and cMLSB (constitutive resistance) that are resistant to macrolides, lincosamides and streptogrammins B antibiotics, whereas MS resistance that is sole resistant to macrolides and streptogramins B antibiotics. Erythromycin ribosome methylase (erm) genes are responsible for expressing inducible clindamycin resistance among S. aureus. In the present investigation, a Double disc approximation/Disc induction test (D-test) and PCR were used. Out of 428 strains the prevalence of iMLSB, cMLSB and MS phenotypes were 36 (8.41%), 47 (10.98%) and 48(11.21%) respectively. It is concluded that D-test should be routinely done to avoid treatment failure due to clindamycin resistance. In addition, PCR is a simple, quick, reliable and sensitive method that could also be used in the detection of inducible clindamycin resistance. The reason for the lower prevalence of iMLSB phenotype in the present study could be due to the reason that samples included in this study were mostly from the rural areas as the exposure of antimicrobial agents is less. Keywords: Clindamycin resistance, D-test, ermA, ermC, iMLSB, S. aureus

Phenotypic Detection of Inducible Clindamycin Resistance among Clinical Isolates of Staphylococcus aureus in Bharatpur Hospital

Background: Clindamycin is regarded as a reserve drug in the treatment of staphylococcal infections. Among few therapeutic alternatives available for treatment of erythromycin-resistant Staphylococcus aureus infections, clindamycin has several advantages but major limitation in its use is the development of resistance resulting in treatment failure. Routine clindamycin susceptibility test may fail to detect such inducible resistance which can be detected by Double disc diffusion test (D-test). The present study was undertaken to determine the incidence of inducible clindamycin resistance among clinical isolates of S. aureus in a tertiary care hospital in central Nepal. Methods: A cross-sectional study was carried out among the patients visiting Bharatpur Hospital from September to November 2019. A total of 1279 clinical samples were examined for the identification of S. aureus by standard microbiological procedures. Antibiotic susceptibility testing of the isolates was done by Kirby-Bauer disc diffusion method and all the erythromycin-resistant isolates were subjected to D-test for the phenotypic detection of inducible clindamycin resistance according to CLSI guidelines (2016). Results: S. aureus was recovered from 4.5% (58/1279) samples of which 35 isolates were Methicillin-Resistant Staphylococcus aureus (MRSA) and 23 were multi-drug resistant (MDR). Tetracycline was found to be the most effective antibiotic whereas erythromycin was the least effective. D-test revealed that 39.7% isolates showed iMLSB phenotype, 3.5% showed cMLSB phenotype and 56.8% showed MS phenotype. The percentage of inducible and constitutive resistance was seen higher amongst MRSA isolates compared to Methicillin-Sensitive Staphylococcus aureus (MSSA) isolates. Incidence of S. aureus was found higher among females and in the age group 20-30 years and in pus samples (p<0.01). Conclusions: Routine testing of inducible clindamycin resistance is suggested among the clinical isolates of erythromycin-resistant Staphylococci to avoid treatment failure.

Detection of Inducible clindamycin resistance in nasal carriers of Staphylococcus aureus among healthcare workers

Staphylococcus aureus () is recognized as one of the most common microrganisms causing nosocomial and community-acquired infections. Nasal carriage of Staphylococcus aureus is becoming an increasing problem among healthcare workers and in the healthy community individuals. General populations with persistent Staphylococcus aureus nasal carriage rates at 10% to 20%, and up to 50% are intermittent carriers. Furthermore, carrier levels of 25% have been reported among healthcare workers(HCW’s). Strains with inducible clindamycin resistance (ICR) are difficult to detect in the routine laboratory as they appear to be resistant to erythromycin and sensitive to clindamycin in vitro when not placed adjacent to each other. In such cases, in vivo treatment with clindamycin may select constitutive erm mutants leading to clinical therapeutic failure. 100 nasal swabs samples were collected during January 2019 to November 2019. Isolates were identified using standard microbioloical procedures and MRSA determined by the disk diffusion method. The D-test was performed for detection of Inducible clindamycin resistance isolates with Clinical Laboratory Standard Institute guidelines.: Out of 18 isolated, 33.3 were MRSA. Of 18 isolates tested for ICR by D-test, 6 (33.3%) yielded inducible resistance. Inducible clindamycin resistance was found to be significantly higher among MRSA than MSSA isolates. Beside personal hygiene practices of healthcare workers, regular implementation of infection control practices, including screening of nasal carriages and microbial flora in our hospital are necessary to prevent spread of MRSA. It is also advisable to perform routine nasal decolonization of healthcare workers using mupirocin ointment to prevent transmission of these organisms.

In Vitro Study of Constitutive and Inducible Clindamycin Resistance in Staphylococcus Aureus with Reference to Methicillin Resistant Staphylococcus Aureus: Experience From Tertiary Care Hospital in Punjab

Backround: Serious infections due to methicillin resistant Staphylococcus aureus (MRSA) have become a major clinical challenge. Globally Macrolide-lincosamide streptogramin B family of antibiotics are commonly used to treat such infections as an alternative to vancomycin. The study was to conducted to find out the presence of inducible clindamycin resistance among Staphylococcus aureus and their association with methicillin resistance. Method: The study conducted over one year (Jan 2016 - Dec 2016) in microbiology department of Guru Gobind Singh Medical College, Faridkot. Two hundred fifteen S.aureus isolates were included in the study. Methicillin resistance was detected by cefoxitin (30μg) disc diffusion method and inducible clindamycin resistance by erythromycin and clindamycin disc approximation test (D-Test). Results: Of the 215 clinical isolates of S. aureus , 140 (65.11%) were MRSA. Erythromycin and clindamycin resistance was seen in 79.06%(170/215) and 49.30% ( 106/215) respectively. Resistance to erythromycin and clindamycin were higher in MRSA than MSSA (erythromycin resistance:100%v s 22.5% and Clindamycin resistance:70.1% vs 10.6%). Both iMLSB and cMLSBphenotypes are predominant in MRSA. Conclusion: Detection of MRSA in our study shows the need to improve health care practices and to formulate new infection control policies to control MRSA infections. Inducible and constitutive resistance is comparatively higher in our study in MRSA .So It is necessary to perform D-test for detection of inducible clindamycin resistance among MRSA in routine antibiotic sensitivity testing so that therapeutic failures can be avoided.

Detection of inducible clindamycin resistance among staphylococcus isolated from patients attending a tertiary care hospital in South India

Detection of inducible clindamycin resistance among staphylococcus isolated from patients attending a tertiary care hospital in South India

Methicillin and Inducible Clindamycin-resistant Staphylococcus aureus Isolates from Clinical Samples in Abia State

Staphylococcus aureus is a major bacterial pathogen that causes different community and hospital-acquired infections. S. aureus resistant to methicillin has become a big and expanding problem of concern in many developing countries. Clindamycin has also been discovered to be a preferred therapeutic alternative for the treatment of both methicillin susceptible and resistant staphylococcal infections. This study examined the prevalence of Methicillin-resistant Staphylococcus aureus (MRSA) in clinical samples of patients in Abia state, Nigeria using standard recommended procedures. A total of 750 clinical specimens of blood and urine samples, wound, ear, nasal, high vaginal and ear swabs were collected from three major health facilities in Abia state, Nigeria. Each sample was cultured for bacterial isolates and examined for colonial and cellular morphology while biochemical identification was performed. Antimicrobial susceptibility test was performed on Mueller-Hinton agar (MHA) by disc diffusion method and MRSA screening was done using cefoxitin disc. A total of 265 (35.3%) S. aureus isolates were recovered, out of which 126(47.5%) were from males and 139(52.5%) were from females, however there was no association between the prevalence and gender (p-value = 0.05) and also prevalence and age (p-value = 0.52). Of the 265 S. aureus isolates recovered, 164(61.9%) were MRSA. All 100% of the MRSA were susceptible to vancomycin, 120(73.2%) to clindamycin, 92(56.1%) to gentamycin. All 100% were resistant to ceftazidine, 157(95.7%) to cloxacillin, 146(89.0%) to augmentin, 136(82.9%) to ceftriaxone and 103(61.6%) to erythromycin. The MRSA strains showed much higher resistance rate than their MSSA counterparts to all tested antibiotic except clindamycin. 64(39.0%) of the MRSA were resistant to 4 classes of antibiotics indicating multi drug resistance (MDR). The overall prevalence of inducible clindamycin resistance among methicillin resistant isolates was 29(17.7%). This implies that 17.7% could have been misidentified as clindamycin susceptible by Kirby-Bauer disk diffusion method. In conclusion prevalence of MRSA was high and it is important to routinely carry out the D-test for detection of inducible clindamycin resistance if clindamycin is considered as a treatment option.

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.

Inducible clindamycin resistance among Staphylococcal clinical isolates from Tripoli Central Hospital, Libya

Abstract Background: The resistance to antimicrobial agents among Staphylococci is an increasing problem. This has led to a renewed interest in the usage of macrolide-lincosamide-streptogramin B (MLSB) antibiotics to treat staphylococcal infections. Clinical failure has been reported due to multiple mechanisms that confer resistance to clindamycin antibiotics. The present study was to investigate the inducible clindamycin resistance among isolates of methicillin resistant Staphylococci by the D-test method. MATERIALS & METHODS: This study was conducted on 218 staphylococcal isolates obtained from different clinical specimens of outpatients and inpatients admitted to Tripoli Central Hospital (TCH), Libya. Methicillin resistance was detected by oxacillin, cefoxitin disc diffusion test (Kirby Bauer method) and confirmed by other biochemical tests. Detection of inducible clindamycin resistance was performed by D-test using erythromycin and clindamycin. Results: Eighty-six out of 218 staphylococcal isolates were resistant to erythromycin,26 (11.9%) isolates were D-test positive indicating inducible (iMLSB) phenotype, 24 (11%) isolates exhibited constitutive (cMLSB) phenotype, while 36 (16.5%) showed true sensitivity to clindamycin indicating (MS) phenotype. The distribution of isolates showing iMLSB phenotype was 12 (19.4%) for methicillin-resistant Staphylococcus aureus (MRSA), 8 (17.0%) for methicillin-resistant coagulase-negative Staphylococci (MRCNS), 6 (6.4%) for methicillin-sensitive Staphylococcus aureus (MSSA) and 0 (0%) for methicillin-sensitive coagulase-negative Staphylococci (MSCNS). Conclusion: Higher prevalence of iMLSB phenotype was mainly associated with methicillin-resistant than methicillin-sensitive isolates. We recommend that D-test should be performed to facilitate the appropriate treatment of patients infected with Staphylococci.

Erm gene distribution among Norwegian Bacteroides isolates and evaluation of phenotypic tests to detect inducible clindamycin resistance in Bacteroides species

The aims of this study were to describe the distribution of the most common erm genes in a collection of Norwegian Bacteroides isolates and to investigate whether the phenotypic tests for determining inducible clindamycin resistance among Bacteroides species recommended by EUCAST, NordicAST and the manufacturer of E-test®, are effective.We investigated 175 unique Bacteroides isolates for the presence of erm(B), erm(F) and erm(G) genes, determined their minimum inhibitory concentrations (MICs) to clindamycin and categorised their susceptibility according to EUCAST breakpoints. 27 isolates were resistant to clindamycin. Furthermore, we investigated whether these recommended methods could detect inducible resistance in the Bacteroides isolates: 1) EUCAST recommendation: Dissociated resistance to erythromycin (clindamycin susceptible with erythromycin MIC > 32 mg/L), 2) NordicAST recommendation: Double disk diffusion test (DDD) or 3) Manufacturer of E-test®’s recommendation: prolonged incubation of clindamycin E-test® for 48 h.erm genes were detected in 30 (17%, 95% CI 12%–23%) of 175 Bacteroides isolates with erm(F) as the dominating gene. There were six (4%, 95% CI 1%–7%) of 148 clindamycin susceptible isolates harbouring erm genes, they were considered inducibly resistant to clindamycin. None of the methods for phenotypic detection of inducible clindamycin resistance performed satisfactory with sensitivities of 33%, 17% and 0% and specificities of 90%, 99% and 97% for dissociated resistance, DDD and prolonged incubation of clindamycin E-test®, respectively.In our view, the scientific basis for investigating every Bacteroides isolate for inducible resistance to clindamycin is weak. Molecular detection of erm genes may prove a better option than the phenotypic methods we evaluated.

Antibiotic resistance and biofilm production among the strains of Staphylococcus aureus isolated from pus/wound swab samples in a tertiary care hospital in Nepal

BackgroundThe increasing drug resistance along with inducible clindamycin resistance, methicillin resistance and biofilm production among the strains of Staphylococcus aureus are present as the serious problems to the successful treatment of the infections caused by S. aureus. So, the main objectives of this study were to determine the antimicrobial susceptibility patterns along with the rates of inducible clindamycin resistance, methicillin resistance and biofilm production among the strains of S. aureus isolated from pus/wound swab samples.MethodsA total of 830 non-repeated pus/wound swab samples were processed using standard microbiological techniques. The colonies grown were identified on the basis of colony morphology, Gram’s stain and biochemical tests. Antimicrobial susceptibility testing was performed by Kirby–Bauer disc diffusion technique. Detection of inducible clindamycin resistance was performed by D test, while detection of methicillin resistant S. aureus (MRSA) was performed by determination of minimum inhibitory concentration of oxacillin by agar dilution method. Similarly, detection of biofilm formation was performed by microtiter plate method. Strains showing resistance to three or more than three different classes of antibiotics were considered multidrug resistant.ResultsTotal 76 samples showed the growth of S. aureus, among which 36 (47.4%) contained MRSA and 17 (22.4%) samples were found to have S. aureus showing inducible clindamycin resistance. Among the S. aureus isolated from outpatients, 41.9% were MRSA. Highest rates of susceptibility of S. aureus were seen toward linezolid (100%) and vancomycin (100%). Similarly, S. aureus isolated from 35 (46.1%) samples were found to be biofilm producers. Higher rate of inducible clindamycin resistance was seen among MRSA in comparison to methicillin susceptible S. aureus (MSSA). Similarly, higher rates of multidrug resistance and methicillin resistance were found among biofilm producing strains in comparison to biofilm non producing strains.ConclusionsThe rate of isolation of MRSA from community acquired infections was found to be high in Nepal. Increased rate of inducible clindamycin resistance as compared to previous studies in Nepal was noted. So for the proper management of the infections caused by S. aureus, D test for the detection of inducible clindamycin resistance should be included in the routine laboratory diagnosis. Further, detection of biofilm production should also be included in the routine tests. Linezolid and vancomycin can be used for the preliminary treatment of the serious infections caused by S. aureus.

Characterisation of Streptococcus pyogenes on the basis of pyrotoxin exotoxin genes in north India

Introduction: Scarlet fever and toxic shock syndrome are two major clinical entities caused due to the action of pyrogenic exotoxin. We screened the clinical isolates of Streptococcus pyogenes for the presence of major exotoxin encoding genes SpeA, SpeB and SpeC. Materials and Methods: Isolates of S. pyogenes obtained from clinical samples were characterised on the basis of pyrogenic exotoxin encoding genes SpeA, SpeB, and SpeC. The sample was cultured and identified by conventional biochemical test and further confirmed by latex agglutination test kit (Remel, USA). On confirmed group A streptococci isolates, deoxyribonucleic acid extraction and polymerase chain reaction were performed. Antimicrobial susceptibility testing and detection of inducible clindamycin resistance for all clinical isolates were performed using Clinical and Laboratory Standard Institute guidelines by Kirby–Bauer disk diffusion method. Results: Thirty-one confirmed isolates of S. pyogenes were tested; out of which, the respective prevalence values of SpeB and SpeC genes were 80.6 and 35.5%. SpeA gene was detected in only single isolate. All the isolates were susceptible to penicillin, but resistance was seen with erythromycin, tetracycline and levofloxacin. Inducible clindamycin resistance was seen in two isolates. Conclusion: The present study found that the genes encoding pyrogenic exotoxin is circulating in the S. pyogenes isolates present in north India and have the potential of causing scarlet fever that is not reported so far from the country. A significant percentage of drug resistance was noted for the alternative drugs required for the treatment of penicillin allergic patients. The recent upsurge in the cases of scarlet fever in south-east Asia warns us to keep a check on gene profile of these isolates in the community.

Antibiotic resistance of Streptococcus agalactiae isolated from pregnant women in Garankuwa, South Africa.

BackgroundThis study was undertaken to determine the susceptibility profile and the mechanism of antibiotic resistance in Group B streptococcus (GBS) isolates detected in vaginal and rectal swabs from pregnant women attending Dr George Mukhari Academic Hospital, a University Teaching Hospital in Pretoria, South Africa.MethodsThe samples were collected over an 11-month period, cultured on selective media (colistin and nalidixic acid agar and Todd-Hewitt broth), and GBS positively identified by using different morphological and biochemical tests. The susceptibility testing was done using the Kirby–Bauer and E test methods according to CLSI guidelines 2012. The D test method was used for the detection of inducible clindamycin resistance. Multiplex PCR with specific primers was used to detect different genes coding for resistance.ResultsOut of 413 samples collected, 128 (30.9 %) were positive with GBS. The susceptibility testing revealed that 100 % of isolates were sensitive to penicillin, ampicillin, vancomycin and high level gentamicin. Erythromycin and clindamycin resistance was 21.1 and 17.2 %, respectively, in which 69 % had harboured constitutive macrolide, lincosamide and streptogramin B (MLSB), 17.4 % had inducible MLSB. The M and L phenotypes were present in 6.8 % each. The methylation of target encoded by ermB genes was the commonest mechanism of resistance observed in 55 % of isolates, 38 % of isolates had both ermB and linB genes and efflux pump mediated by mefA genes was also distributed among the isolates.ConclusionsThe study reaffirmed the appropriateness of penicillin as the antibiotic of choice for treating GBS infection. However it identified the challenges of resistance to macrolides and lincosamides used as alternative drugs for individuals allergic to penicillin. More GBS treatment options for penicillin allergic patients need to be researched on.

Epidemiological and Inducible Resistance in Coagulase Negative Staphylococci.

Background and Objectives:Coagulase negative staphylococci (CNS) are potential pathogens with the increased use of implants in hospitals. Macrolide, lincosamide and streptogramin B (MLSB) are used in the treatment of staphylococcal infections. The aim of this study was to molecular detection of inducible clindamycin resistance and genetic pattern in CNS isolates and their transmission between hospitals.Materials and Methods:110 CNS strains, isolated from hospitalized patients in the intensive care unit and infectious wards of Besat and Toohid hospitals, Sanandaj. Methicillin resistance was done by agar screen test and the resistance inducible Clindamycin by the D-Test. Multiplex PCR was performed, using primers specific for erm (A, B, C, and TR) genes. Diversity of strains was determined by ERIC–PCR technique based on the similarities between DNA fingerprints by using Jaccards coefficient in the SAHN program of the NTSYS-pc software.Results:Of the 110 isolates, 64(58.2%) were methicillin -resistant CNS (MRCNS), 48(43.6%) were resistant to erythromycin (ERCNS). Out of 48 Erythromycin-resistant strains 5 (10.4%) were iMLSB phenotypes that 4 isolates showed genes erm by Multiplex PCR. The ERIC–PCR profiles allowed typing of the 110 isolates into 90 ERIC-types which were grouped into fourteen main clusters (C1–C14).Conclusion:The results of this study also showed that most of CNS isolated produced different genomic fingerprint patterns, therefore, source of infection is differen t.

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.

Performance of Vitek-2 System for Detection of Inducible Clindamycin Resistance among Clinical Isolates of Staphylococci in Comparison to the D-Test

Background: Clindamycin resistance among clinically significant staphylococcal isolates is now increasing. Routine testing of staphylococcal isolates for inducible clindamycin resistance (ICR) is advocated by the Clinical Laboratory Standards Institute (CLSI). Automated system Vitek 2 offers a panel that detects inducible clindamycin resistance directly. it is easy and more cost-effective than the more labor-intensive CLSI reference methods. Objectives: The aim of this study was to assess the performance of Vitek-2 system for ICR detection against the reference D-test, as well as to detect the presence of erm-A and erm-C genes among these isolates. Methodology: 22 clinical staphylococcal isolates (15 Staph aureus and 7 coagulase negative Staph (CoNS) were examined for ICR both by D- test and Vitek-2 system. multiplex PCR was performed for the isolates to detect ermA and ermC genes. Results: Out of the 22 isolates, ICR was detected by Vitek-2 in 6 isolates (27.7%). five of the 6 isolates were confirmed by D-test. sensitivity, specificity, positive and negative predictive values were calculated as 100%, 94.1%, 83.33% and 100% respectively. ermC gene was detected in 20/22 isolates, 5 isolates were positive for both genes. Conclusion: Vitek-2 is considered a potentially reliable test for detection of ICR, further studies are recommended on large number of isolates.

Detection of inducible clindamycin resistance in staphylococcus aureus and CONS at tertiary care hospital

Background: The increasing prevalence of Methicillin resistant among staphylococci (MRSA) is an increasing problem. Increasing incidence of infections due to MRSA has led to emphasis on the need for safe & effective agents to treat both systemic & localized Staphylococcal infections. Clindamycin has been used to treat pneumonia & soft tissue and musculoskeletal infections due to MRSA. One important issue in Clindamycin treatment is the risk of clinical failure during therapy caused by MLSB inducible resistance. Objectives: To isolate and identify Staphylococcus aureus and CONS from all clinical samples & to determine the inducible Clindamycin resistance among the Staphylococcus aureus and CONS. Methods: A total of 100 isolates of Staphylococcus aureus and CONS from various samples were isolated. Methicillin resistance was detected by using a 1 μg Oxacillin disc. The D-test was performed using the discs of Clindamycin (CL)(2μg) and Erythromycin (ER)(15μg) placed at a distance of 15mm (centre to centre) along with routine antibiotic susceptibility testing. Results: Among Staphylococcus aureus, MSSA isolates were 32(47.05%) compared to MRSA isolates, 26(38.24%) and among CNS, MSCONS isolates were 8(11.77%) compared to MRCONS 2(2.9%).A total of 12(17.64 %) isolates showed iMLSB, of which 8(11.77%) were MRSA, 2(2.9%) were MSSA and 2(2.9%) MRCONS isolates. Conclusion: Prevalence of inducible Clindamycin resistance among Staphylococcal isolates was significant. Hence the implementation of this D-test routinely, which is simple, reliable & inexpensive will reveals the iMLSB & cMLSB phenotype & prevents the therapeutic failure of Clindamycin. Keywords: Methicillin resistant Staphylococcus aureus (MRSA), Inducible Clindamycin resistance, D-test, Erythromycin, iMLSB phenotype

D-Zone test for detection of inducible clindamycin resistance using SirScan paper disks and Rosco Neo-Sensitabs at 25 and 15 mm distances

Clindamycin is a possible antibiotic treatment of infections by Gram-positive cocci. However, its use can be limited by inducible clindamycin resistance. To screen for the presence of this type of resistance, the D-zone test is used. The aim of this study was to compare the performance of SirScan paper disks with that of Rosco Neo-Sensitabs for the D-zone test at distances according to dispensers provided by the manufacturers (25 mm) and when the disks are placed at a distance of 15 mm. We studied 364 Gram-stain-positive cocci representing clinical isolates that were resistant to erythromycin and susceptible to clindamycin. Out of these isolates, 207 (57%) gave a positive D-zone test result at 25 mm distance using SirScan paper disks. When the test was repeated with the same disks placed 15 mm from the 157 (43%) isolates that had previously given a negative result, 58 (36.9%) gave a positive D-zone test result. The same isolates were also found to test positive when Rosco Neo-Sensitabs were used. Placing the disks at a distance of 15 mm instead of 25 mm led to an 84.3% increase in positive D-tests among Staphylococcus aureus, 43.8% among group B streptococci (GBS) and 6.4% among coagulase-negative staphylococci (CNS). In conclusion, the SirScan paper disks are equivalent to Rosco Neo-Sensitabs in screening for inducible resistance to clindamycin. The D-test needs to be performed at a shorter distance (15 mm) to prevent false-negative reporting.