Inducible Clindamycin Resistance and Biofilm Production among Staphylococci Isolated from Tertiary Care Hospitals in Nepal

Resistance to antibiotics, biofilm formation and the presence of virulence factors play important roles in increased mortality associated with infection by staphylococci. The macrolide lincosamide streptogramin B (MLSB) family of antibiotics is commonly used to treat infections by methicillin-resistant isolates. Clinical failure of clindamycin therapy has been reported due to multiple mechanisms that confer resistance to MLSB. This study aims to find the incidence of different phenotypes of MLSB resistance and biofilm production among staphylococci. A total of 375 staphylococci were isolated from different clinical samples, received from two tertiary care hospitals in Nepal. Methicillin resistance was detected by cefoxitin disc diffusion method and inducible clindamycin resistance by D test, according to CLSI guidelines. Biofilm formation was detected by the tissue culture plate method and PCR was used to detect ica genes. Of the total staphylococci isolates, 161 (42.9%) were Staphylococcus aureus, with 131 (81.4%) methicillin-resistant strains, and 214 (57.1%) isolates were coagulase-negative staphylococci, with 143 (66.8%) methicillin-resistant strains. The overall prevalence of constitutive MLSB (cMLSB) and inducible MLSB (iMLSB) phenotypes was 77 (20.5%) and 87 (23.2%), respectively. Both iMLSB and cMLSB phenotypes predominated in methicillin-resistant isolates. The tissue culture plate method detected biofilm formation in 174 (46.4%) isolates and ica genes in 86 (22.9%) isolates. Among biofilm producing isolates, cMLSB and iMLSB phenotypes were 35 (20.1%) and 27 (15.5%), respectively. The cMLSB and iMLSB were 11 (12.8%) and 19 (22.1%), respectively, in isolates possessing ica genes. Clindamycin resistance in the form of cMLSB and iMLSB, especially among MRSA, emphasizes the need for routine D tests to be performed in the lab.

Staphylococcus aureus with inducible clindamycin resistance and methicillin resistance in a tertiary hospital in Nepal

Background Staphylococcus aureus is a global public health issue in both community and hospital settings. Management of methicillin-resistant S. aureus (MRSA) infections are tough owing to its resistance to many antibiotics. Macrolide-lincosamide-streptogramin B (MLSB) antibiotics are commonly used for the management of MRSA. This study was aimed to determine the occurrence of inducible clindamycin- and methicillin-resistant S. aureus at a tertiary care hospital in Kathmandu, Nepal. Methods A total of 1027 clinical samples were processed following standard laboratory procedures and antibiotic susceptibility testing of S. aureus was performed by disc diffusion method. MRSA isolates were detected phenotypically using cefoxitin disc, and inducible clindamycin resistance was detected phenotypically using the D-zone test. Results Of 1027 samples, 321 (31.2%) were culture positive, of which 38 (11.8%) were S. aureus. All S. aureus isolates were susceptible to vancomycin, and 25 (67%) of S. aureus isolates were multidrug-resistant. Similarly, 15 (39.5%) of S. aureus were MRSA and 14 (36.5%) were inducible clindamycin-resistant phenotypes. Conclusion Inducible clindamycin and methicillin resistance were common in S. aureus. This emphasizes that the methicillin resistance test and the D-zone test should be incorporated into the routine antibiotic susceptibility testing in hospital settings.

Inducible Clindamycin Resistant Staphylococcus aureus among Patients Attending Tertiary Care Centre: A Descriptive Cross-sectional Study

Introduction: Staphylococcus aureus, a superbug, resistant to multiple antibiotics led to growing interest in the usage of macrolide-lincosamide-streptogramin B antibiotics, which are now rapidly developing resistance. This study aims to find the prevalence of inducible clindamycin-resistant Staphylococcus aureus among obtained clinical samples from in-patient and out-patient departments of a tertiary care center. Methods: This is a descriptive cross-sectional study done in clinical samples from the in-patient and out-patient departments of a tertiary care center from September 2020-May 2021. Ethical clearance was taken from the Institutional Review Committee (Ref: 068/2077/2078). Staphylococcus aureus were isolated and antibiotic susceptibility tests were performed by disc diffusion method. Inducible clindamycin and methicillin resistance Staphylococcus aureus were detected using D-test and cefoxitin disc according to Clinical and Laboratory Standards Institute guidelines. Convenient sampling was done and the data was analyzed using Statistical Package for Social Sciences version 20. Point estimate at 95% confidence interval was calculated along with frequency and proportion for binary data. Results: Among a total of 141 Staphylococcus aureus isolated, the prevalence of inducible clindamycin resistant phenotype was 41 (29.1%) (21.6-36.59 at 95% Confidence Interval). Whereas, 30 (21.3%) were constitutive clindamycin resistant. The inducible 28 (47.5%) and 19 (32.2%) constitutive clindamycin resistance was higher among methicillin-resistant Staphylococcus aureus. Conclusions: The frequency of inducible clindamycin resistance among methicillin resistant Staphylococcus aureus was high, which alarms the use of macrolide-lincosamide-streptogramin B antibiotics in Staphylococcus aureus infections. Hence, D-test should be performed to detect inducible clindamycin resistance in routine testing to prevent treatment failure.

184. Inducible Clindamycin Resistance Testing on Pediatric Streptococcus pneumoniae Isolates

Background In 2013, the Clinical and Laboratory Standards Institute recommended inducible clindamycin resistance (ICR) testing on macrolide-resistant Streptococcus pneumoniae isolates, which arises due to the ermB gene. Ribosomal methylation by ermB confers resistance to macrolides (high-level resistance), lincosamides and streptogramin B. The goal of our study is to characterize the prevalence of ICR among pediatric pneumococcal isolates. Methods We identified erythromycin-resistant(R) (minimum inhibitory concentration [MIC] ≥ 1 µg/mL) and clindamycin-susceptible(S) (MIC ≤ 0.25 µg/mL) pneumococcal isolates from pediatric patients seen at Children’s Mercy Hospital from 2007 to 2017. Determination of ICR was achieved via disk approximation (D-zone test) with standard erythromycin (15 µg) and clindamycin (2 µg) disks. Isolates with high-level erythromycin resistance (MIC ≥ 32µg/mL) were also tested for ermB gene by PCR. Positive and negative controls were used for D-zone test and ermB PCR. Results We identified 289 erythromycin-R pneumococcal isolates; of those 194 (67.1%) were clindamycin-S (Figure 1). One-hundred and sixty-nine isolates were available for ICR testing, 166 (98%) isolates represented non-invasive disease samples. Median age of patients with erythromycin-R and clindamycin-S isolates was 19 (range 0.1 – 180) months. None of the isolates expressed ICR based on the D-zone test. Thirteen of those isolates (7.7%) expressed high-level erythromycin-R (MIC range 32-128 µg/mL); all were negative for ermB. The most common serotypes/serogroups among erythromycin-R and clindamycin-S isolates were: 15 (n=22), 35B (n=19), 11 (n=16), 6 (n=16), 19A (n=14) and 33 (n=12). Conclusion Erythromycin-R and clindamycin-S pneumococcal isolates did not express ICR and isolates with high-level erythromycin-R did not carry ermB. Multicenter studies are needed to determine if ICR testing is required for macrolide-resistant pneumococcal isolates in the PCV13 era. Disclosures Liset Olarte, MD, MSc, GSK (Research Grant or Support)Merck (Research Grant or Support)Pfizer (Research Grant or Support)Sanofi (Research Grant or Support) Douglas S. Swanson, MD, Merck (Research Grant or Support)Pfizer (Research Grant or Support)Sanofi (Research Grant or Support)

Antibiogram of Staphylococcus aureus in a Tertiary Care Hospital: Changing Trends

Methicillin resistant Staphylococcus aureus (MRSA) is major cause of nosocomial and community infections. Its prevalence varies with country and with hospitals within a country. Therefore, it is important for continuous surveillance in hospitals and other healthcare facilities in order to limit the spread of infections caused by MRSA. To determine the antibiogram of Staphylococcus aureus in a tertiary care hospital and to determine the change in trends in the antimicrobial susceptibility pattern of Staphylococcus aureus. To determine the prevalence of MRSA in a tertiary care hospital. This cross- sectional study was conducted at the Department of Microbiology, SMSR, Sharda University and Hospital. A total of 100 strains identified by morphological and biochemical characteristics were tested for antibiotic susceptibility using Kirby-Bauer disc diffusion method and the Prevalence of Inducible Clindamycin Resistance among the isolates. 100 out of 13,639 isolates clinical comprising samples were obtained Pus (78.6%), Blood (7%), Swab (4.1%), Sputum (4.1%), Urine (4.1%), Semen (2%). Maximum MRSA were obtained from pus samples (81%). However, out of total 7 isolates of Staphylococcus aureus obtained from blood 4 were MRSA and 3 were MSSA. The prevalence of MRSA that is (40%) infections was a high in our setup and is comparable to studies done earlier. This trend is particularly alarming for Staphylococcus aureus because of the severity and diversity of disease caused by this uniquely versatile pathogen.

Detection of Inducible Resistance to Clindamycin among Methicillin Resistant and Sensitive strains of Staphylococcus aureus from India

The resistance to MLSB antibiotics, i.e. Macrolide-Lincosamide-Streptogramin B (MLSB), is an increasing problem among Methicillin-resistant Staphylococci. The resistance to macrolides can be by efflux mechanism or via inducible or constitutive resistance. Unfortunately, routine clindamycin susceptibility testing fails to detect the inducible resistance, which commonly results in treatment failure and necessitates incorporating a simple D-test to detect such resistance. A retrospective observational study was performed on S. aureus isolates from patients. The strains were subjected to antibiotic susceptibility testing followed by detection of mecA gene by a polymerase chain reaction and, the ‘D-test’ was performed to know the inducible resistance to clindamycin. A total of 235 isolates were identified as S. aureus. Antibiotic susceptibility test indicated 190 MRSA and 45 are sensitive to MLSB (MS). Inducible clindamycin resistance was found among 48 (20.4%) isolates and constitutive resistance in 104 (44.2%). MRSA strains had higher inducible and constitutive resistance than MSSA strains (22.1%, 51.6% and 13.3%, 13.3%, respectively). Clindamycin is a commonly used antibiotic in patients with MRSA infections to spare higher-end anti-MRSA antibiotics like linezolid and vancomycin. To detect inducible clindamycin to avoid treatment failures; the study showed the importance of incorporating the D-test in routine testing.

The Prevalence of Inducible Clindamycin Resistance Staphylococcus aureus among Various Clinical Specimens in Khartoum state Sudan

Background : S. aureus is frequently associated with skin infections, pneumonia, surgery wounds, bacteraemia, osteomyelitis and endocarditis, being considered one of the most important pathogens of the human being, both at the community level and at nosocomial infections, and may become serious if caused by antimicrobial resistant strains, especially methicillin-resistant S. aureus (MRSA) strains, which are resistant to most of the antimicrobial agents, methicillin-sensitive S.aureus (MSSA) and isolates with reduced susceptibility and resistance to vancomycin, which is the last drug for the treatment of MRSA infections. So, this study aimed to detect the existence of inducible resistance of S. aureus to Clindamycin in Khartoum-Sudan among patients attended to Suba University Hospital. Methods : The study was performed as cross-sectional one, 53 clinical isolates of S. aureus obtained from (34 females and 19 males) with different clinical condition among patients attended to Suba University Hospital in Khartoum-Sudan from April to August 2017. To detect inducible clindamycin resistant by using D test. In addition to that MRSA / MSSA all the isolates screened for methicillin resistant by using 1 µg oxacillin then examined for inducible clindamycin resistant by D test. In addition to that examine for antimicrobial susceptibility profile which include vancomycin, gentamycin, tetracycline and co-trimoxazole. The data were analyzed using Statistical Package for Social Science, version 22, P. value <0.05 was considered statistically significant Results : out of 53 isolates, 36 S. aureus isolated resistant to Clindamycin, 26 (72.2%) were MRSA and 10 (27.8%) were MSSA by means of D test, while 17 (32.1%) of isolates were sensitive 9 (53%) MRSA and 8 (47 %) MSSA. Comparing Induced clindamycin resistance showed equally distribution among MSSA and MRSA isolates, giving no significant difference as P- value 0.167. Conclusion : This study showed that D.test to detect inducible clundamycin resistance in staphylococcus aureus.