cMLSB Phenotype Research Articles

Molecular Basis of Antimicrobial Resistance in Group B Streptococcus Clinical Isolates from Saudi Arabia.

Published data on the molecular mechanisms underlying antimicrobial resistance in Group B Streptococcus (GBS) isolates from Saudi Arabia are lacking. Here, we aimed to determine the genetic basis of resistance to relevant antibiotics in a collection of GBS clinical isolates (n = 204) recovered from colonized adults or infected patients and expressing serotypes Ia, Ib, II, III, V, and VI. Initial susceptibility testing revealed resistance to tetracycline (76.47%, n = 156/204), erythromycin (36.76%, n = 75/204), clindamycin (25.49%, n = 52/204), levofloxacin (6.37%, n = 13/204), and gentamicin (2.45%, n = 5/204). Primers designed for the detection of known resistance determinants in GBS identified the presence of erm(A), erm(B), mef(A), and/or lsa(C) genes at the origin of resistance to macrolides and/or clindamycin. Of these, erm(B) and erm(A) were associated with the cMLSB (n = 46) and iMLSB (n = 28) phenotypes, respectively, while mef(A) was linked to the M phenotype (n = 1) and lsa(C) was present in isolates with the L phenotype (n = 8). Resistance to tetracycline was mainly mediated by tet(M) alone (n = 112) or in combination with tet(O) (n = 10); the remaining isolates carried tet(O) (n = 29), tet(L) (n = 2), or both (n = 3). Isolates resistant to gentamicin (n = 5) carried aac(6')-Ie-aph(2')-Ia, and those exhibiting resistance to levofloxacin (n = 13) had alterations in GyrA and/or ParC. Most isolates with the erm gene (93.24%, n = 69/74) also had the tet gene and were therefore resistant to erythromycin, clindamycin, and tetracycline. Overall, there were no clear associations between serotypes and resistance genotypes except for the presence of erm(B) in serotype Ib isolates. Dissemination of antibiotic resistance genes across different serotypes represents a public health concern that requires further surveillance and appropriate antibiotic use in clinical practice.

Surveillance of antimicrobial resistance in Streptococcus agalactiae isolated from pregnant women and newborns in 2010–2022

Objective. To study the dynamics and molecular mechanisms of resistance of Streptococcus agalactiae strains isolated from pregnant women and newborns in St. Petersburg in 2010–2022. Materials and Methods. The strains of S. agalactiae (n = 248) were obtained by analyzing the clinical material of pregnant women and newborns who were hospitalized at Research Institute of Obstetrics, Gynecology and Reproductology named after D.O. Ott in 2010–2011 and 2020–2022. Determination of susceptibility to antibacterial drugs was evaluated by disk diffusion method. The detection of resistance genes to macrolides and lincosamides (mef and ermB) was performed by real-time PCR using reagents «Resistom MLSB-Streptococcus» (Litech, Russia). Results. All isolates S. agalactiae (n = 248) were sensitive to penicillin and vancomycin. Compared to 2010–2011, the resistance of S. agalactiae to erythromycin increased from 18.4% to 42.1% and to clindamycin from 15.6% to 39.3%. Among S. agalactiae strains (n = 71) resistant to erythromycin and clindamycin, cMLSB phenotype was predominant (59.1%); iMLSB (31%) and M-phenotype (9.9%) were less common. The results of detection of genes encoding resistance to erythromycin and clindamycin showed that in 38 (53.5%) and 9 (12.7%) isolates of S. agalactiae resistance genes ermB and mefA were detected as one resistance determinant, respectively, association of two ermB/mefA genes was detected in 2 (2.8%) strains; resistance genes were not detected in 22 (31%) isolates. Conclusions. Penicillin and vancomycin are effective drugs for the treatment and prevention of infections caused by S. agalactiae. The increase in resistance to macrolides and lincosamides reflects the global trend of increasing resistance to these antibiotics. Regular monitoring of antibiotic resistance of the pathogen is necessary to update the clinical recommendations.

Prevalence of methicillin and clindamycin resistant Staphylococcus species at a tertiary hospital in Tanzania: Implications for antibiotic stewardship and infection management

Methicillin and clindamycin resistance (constitutive and inducible) pose a common clinical challenge in treating Staphylococcal infections. This cross-sectional study, conducted at Muhimbili National Hospital (MNH) in Tanzania from April to June 2023, to assess the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) and clindamycin-resistant Staphylococcus (S.) species by using a cefoxitin disk (30 μg) and the D-test method as per CLSI 2022 guidelines. Of the 361 clinical samples, 125 (34.6%) were culture-positive. Among Staphylococcus spp., S. aureus was 6% (12/125), while 33.6% (42/125) were coagulase-negative staphylococci (CoNS). Among the isolated S. aureus, 75% were resistant to methicillin, while 66.7% of the CoNS were resistant to methicillin. Further, 92% (11/12) of the S. aureus isolates were resistant to erythromycin, and 50% (6/12) were resistant to clindamycin. Among the CoNS, 83% (35/42) were resistant to erythromycin, and 52% (22/42) were resistant to clindamycin. The proportion of inducible macrolides lincosamide streptogramin B resistance (iMLSB), constitutive macrolides lincosamide streptogramin B resistance (cMLSB), and macrolides lincosamide streptgramin B methicillin susceptible (MS) phenotypes among S. aureus isolates was 16.7%, 41.7%, and 33.3%, respectively, and among CoNS was 19%, 35.7%, and 28.6%, respectively. The overall prevalence of iMLSB and cMLSB phenotypes was 18.5% (10/54) and 37% (20/54), respectively. Comparatively, MRSA had more resistance to ciprofloxacin than methicillin-susceptible S. aureus (MSSA) (88.9% vs. 33.3% p = 0.027), while methicillin-resistant coagulase-negative staphylococci (MR-CoNS) had significantly higher resistance to gentamicin (35.7% vs. 7.1% p= 0.005), and trimethoprim-sulfamethoxazole (78.6% vs. 50% p=0.007) than methicillin-susceptible coagulase-negative staphylococci (MS-CoNS). The high prevalence of methicillin and inducible clindamycin resistance in this study points out a potential rise in treatment failures, prolonged hospitalization, and limited treatment options. Thus, emphasizes the importance of antibiotic stewardship and laboratory-guided antibiotic decisions. To address the growing challenge of antibiotic resistance in Tanzania, it is advisable to implement stringent public health measures, including monitoring antibiotic usage, conducting educational initiatives, and raising awareness among patients and healthcare professionals.

Distribution of Macrolide, Lincosamide, and Streptogramin B and Detection of erm Genes in Staphylococcus aureus from Wounds in Uyo, Nigeria

The increasing resistance to macrolide, lincosamide, and streptogramin B (MLSB) among methicillin-resistant Staphylococcus aureus (MRSA) is a challenge. The study determined the constitutive and inducible MLSB resistance and erm genes in S. aureus from wounds using the erythromycin-clindamycin D-zone test and a multiplex polymerase chain reaction assay, respectively. Of the 260 patients recruited in the study, S. aureus was isolated from the wounds of 102 patients, giving a prevalence rate of 39.2%. Of the 102 S. aureus isolates, 32.4% were methicillin-sensitive S. aureus (MSSA), and 67.6% were MRSA. The prevalence of S. aureus in wounds was higher in females (39.8%) than in males (38.4%). The highest prevalence of S. aureus was found in divorce patients (59.1%) and those residing in urban areas (39.7%). There was no statistical difference between the occurrence of MRSA and MSSA in wounds based on the sex (p = 0.97), age (p = 0.08), and marital status (p = 0.41) of the patients. All (100%) MRSA were resistant to Cefoxitin, and chloramphenicol, while ˂ 50% of MRSA were resistant to Tetracycline, Ciprofloxacin, and Gentamycin. Of the 69 MRSA isolates from the wounds, 21.7% and 26.1% were iMLSB and cMLSB phenotypes, respectively. Nine (9) MSSA were iMLSB phenotypes, and eight MSSA were cMLSB phenotypes. Among the 12 representative isolates, three (3) MRSA and one (1) MSSA isolate possessed the ermC gene. This study has revealed that screening tests for iMLSB-resistant S. aureus strains are critical for the therapeutic management of wound infections caused by S. aureus.

Prevalence, capsular types, antimicrobial resistance and risk factors associated with pneumococcal carriage among children after long-term 10-valent pneumococcal conjugate vaccine use in Brazil.

The 10-valent pneumococcal conjugate vaccine (PCV10) was introduced for childhood vaccination in Brazil's National Immunization Program in 2010. After nine years of PCV10 use, we investigated the carriage prevalence, capsular types, antimicrobial resistance and risk factors among children living in Niterói city, RJ, Brazil. Between September and December 2019, we conducted a cross-sectional study and recruited children under 6years of age. Antimicrobial susceptibility was evaluated by the disk-diffusion method and MICs to beta-lactams and macrolides were determined by E-test®. Capsular types were deduced by multiplex PCR. Logistic regression was used to predict risk factors for pneumococcal carriage. Seventy-five (17.4%) of the 430 children were pneumococcal carriers. The most frequent capsular types were 6C/D (14.7%), 11A/D (13.3%), and 23B (9.3%). PCV10 serotypes represented 5.3%. All isolates were susceptible to levofloxacin, linezolid, rifampicin, and vancomycin. Penicillin non-susceptible pneumococci (PNSP) made up 37.3%, with penicillin and ceftriaxone MICs ranging from 0.12 to 4.0μg/ml and 0.064-4.0μg/ml, respectively. Of the 19 (25.3%) erythromycin-resistant (ERY-R) isolates (macrolide MICs of 6 to>256μg/ml), most had the cMLSB phenotype (84.2%) and carried the erm(B) gene (73.7%). We detected 17 (22.6%) multidrug-resistant (MDR) isolates, strongly associated with serotype 6C/D. Presence of any symptoms, chronic diseases, childcare center attendance, living with young siblings, slum residence, and unstable income were predictors of pneumococcal carriage. Long-term universal childhood use of PCV10 has nearly eliminated carriage with PCV10 serotypes, but the high frequency of MDR isolates, especially associated with serotype 6C/D, remains a concern. Replacing PCV10 with PCV13 should reduce the proportion of ERY-R isolates and PNSP by at least 14% and 18%, respectively.

The antimicrobial activity of cethromycin against Staphylococcus aureus and compared with erythromycin and telithromycin

BackgroundThis study aims to explore the antibacterial activity of cethromycin against Staphylococcus aureus (S. aureus), and its relationship with multilocus sequence typing (MLST), erythromycin ribosomal methylase (erm) genes and macrolide-lincosamide-streptogramin B (MLSB) phenotypes of S. aureus.ResultsThe minimum inhibitory concentrations (MICs) of cethromycin against 245 S. aureus clinical isolates ranged from 0.03125 to ≥ 8 mg/L, with the resistance of 38.8% in 121 methicillin-resistant S. aureus (MRSA). This study also found that cethromycin had strong antibacterial activity against S. aureus, with the MIC ≤ 0.5 mg/L in 55.4% of MRSA and 60.5% of methicillin-sensitive S. aureus (MSSA), respectively. The main MLSTs of 121 MRSA were ST239 and ST59, and the resistance of ST239 isolates to cethromycin was higher than that in ST59 isolates (P = 0.034). The top five MLSTs of 124 MSSA were ST7, ST59, ST398, ST88 and ST120, but there was no difference in the resistance of MSSA to cethromycin between these STs. The resistance of ermA isolates to cethromycin was higher than that of ermB or ermC isolates in MRSA (P = 0.016 and 0.041, respectively), but the resistance of ermB or ermC isolates to cethromycin was higher than that of ermA isolates in MSSA (P = 0.019 and 0.026, respectively). The resistance of constitutive MLSB (cMLSB) phenotype isolates to cethromycin was higher than that of inducible MLSB (iMLSB) phenotype isolates in MRSA (P < 0.001) or MSSA (P = 0.036). The ermA, ermB and ermC genes was mainly found in ST239, ST59 and ST1 isolates in MRSA, respectively. Among the MSSA, the ermC gene was more detected in ST7, ST88 and ST120 isolates, but more ermB genes were detected in ST59 and ST398 isolates. The cMLSB phenotype was more common in ST239 and ST59 isolates of MRSA, and was more frequently detected in ST59, ST398, and ST120 isolates of MSSA.ConclusionCethromycin had strong antibacterial activity against S. aureus. The resistance of MRSA to cethromycin may had some clonal aggregation in ST239. The resistance of S. aureus carrying various erm genes or MLSB phenotypes to cethromycin was different.

Antibiotic resistance pattern, capsular types, and molecular characterization of invasive isolates of Streptococcus pneumoniae in the south of Tunisia from 2012 to 2018

BackgroundStreptococcus pneumoniae remains a leading cause of morbidity and mortality worldwide. In this study, we sought to analyze serotype distributions, antibiotic resistance, and genetic relationships of 106 clinical invasive pneumococcal isolates recovered in Tunisia between 2012 and 2018, prior to the routine use of pneumococcal conjugate vaccines (PCV).MethodsWe used multiplex PCR, the disk diffusion method and/or E-test, and multi-locus sequence typing (MLST).ResultsThe most frequent serotypes were 14 (17%), 19F (14.2%), and 3 (11.3%). Of the 106 S. pneumoniae isolates, 67.9% were penicillin non-susceptible (29.4% were resistant), 45.3% were amoxicillin non-susceptible (17% were resistant), and 16% were cefotaxime non-susceptible. For antibiotics other than β-lactams, resistance rates to erythromycin, tetracycline, cotrimoxazole, and chloramphenicol were 62.3, 33, 22.6, and 4.7%, respectively. Two isolates were non-susceptible to levofloxacin. Among 66 erythromycin-resistant pneumococci, 77.3% exhibited the cMLSB phenotype, and 87.9% carried ermB gene. All tetracycline-resistant strains harbored the tetM gene. The potential coverage by 7-, 10-, and 13-valent pneumococcal conjugate vaccines were 55.7, 57.5, and 81.1%, respectively. A multilocus sequence typing analysis revealed great diversity. Fifty different sequence types (STs) were identified. These STs were assigned to 10 clonal complexes and 32 singletons. The most common STs were 179, 2918, 386, and 3772 – related mainly to 19F, 14, 6B/C, and 19A serotypes, respectively.ConclusionsThis study demonstrated that the majority of the serotypes of invasive pneumococci in the Tunisian population were 14, 19F, and 3. Moreover, we noted a high degree of genetic diversity among invasive S. pneumoniae isolates. The highest proportions of antibiotic non-susceptible isolates were for penicillin, erythromycin, and tetracycline. Further molecular characteristics are required to monitor the genetic variations and to follow the emergence of resistant pneumococci for the post-vaccination era in Tunisia.

Carriage prevalence, serotype distribution, antimicrobial resistance, pspA typing and pilus islets of Streptococcus pneumoniae isolated from adults living in a Brazilian urban slum.

For Brazilian adults, pneumococcal vaccines have been usually taken only by those who are at higher risk for development of pneumococcal diseases. Since populations from lower socioeconomic status are at high risk of acquiring pneumococcal infections, we investigated the carriage prevalence, colonization risk factors, capsular and surface protein types, and antimicrobial resistance among pneumococcal isolates recovered from adults living in a Brazilian urban slum. Between September-December 2016, we conducted a cross-sectional study among individuals aged≥18years who attended a public primary clinic in Niterói/RJ, Brazil. Pneumococci were isolated by culture on sheep blood agar plates with and without gentamicin. Antimicrobial susceptibility was determined for all isolates. We used PCR to determine capsular types, PspA families (Fam) and pilus islets (PI). Of 385 adults, 32 (8.3%) were pneumococcal carriers. Three carriers had two different pneumococci, totaling 35 isolates. After multivariate analysis, smoking, previous hospitalization, alcohol consumption and co-habitation with children aged<6years increased the odds of pneumococcal carriage, but antibiotic use in the previous 2weeks was found to be a protective factor. Fourteen different serogroups/serotypes were detected and the prevalent ones were 9N/L, 10A, 15B/C and 35F/47F (n=3; 8.6% each). Non-typeable (NT) isolates made up 31.4%. All isolates were susceptible to chloramphenicol, levofloxacin and vancomycin. We found eight (22.9%) penicillin non-susceptible pneumococci (PNSP) with minimum inhibitory concentrations (MICs) of 0.38-1.5μg/mL. The two (5.7%) erythromycin-resistant isolates had MIC>256μg/mL, cMLSB phenotype and the erm(B) gene. Twelve (34.3%) and 17 (48.6%) isolates had PspA Fam1 and Fam2, respectively. Three (8.6%) isolates had genes for pilitwo PI-1 and one PI-2. We detected a low frequency of pneumococcal carriage among the adult population, but a high diversity of serotypes. Frequencies of PNSP and NT isolates resistant to antimicrobial agents are concerning.

Molecular Typing of Streptococcus agalactiae- cMLSB Phenotype Isolates by Enterobacterial Repetitive Intergenic Consensus-PCR (ERIC-PCR) in Isfahan, Iran

Molecular Typing of Streptococcus agalactiae- cMLSB Phenotype Isolates by Enterobacterial Repetitive Intergenic Consensus-PCR (ERIC-PCR) in Isfahan, Iran

Human enterococcal isolates as reservoirs for macrolide-lincosamide-streptogramin and other resistance genes.

According to recent studies, the importance of MLS (macrolide-lincosamide-streptogramin) resistance phenotypes and genes in enterococci are reflected in the fact that they represent reservoirs of MLS resistance genes. The aim of this study was to investigate distribution of MLS resistance genes and phenotypes in community- and hospital-acquired enterococcal isolates and to determine their prevalence. The MLS resistance phenotypes (cMLSb, iMLSb, M/MSb, and L/LSa) were determined in 245 enterococcal isolates were characterized using the double-disc diffusion method. Specific primers were chosen from database sequences for detection of the MLS resistance genes (ermA, ermB, ermC, msrA/B, lnuA, lnuB, and lsaA) in 60 isolates of enterococci by end-point PCR. There was no linezolid-resistant enterococcal isolate. Only one vancomycin-resistant (0.6%) isolate was found and it occurred in a community-acquired enterococcal isolate. The most frequent MLS resistance phenotype among enterococcal isolates was cMLSb (79.7% community- and 67.9% hospital-acquired). The most common identified MLS resistance genes among enterococcal isolates were lsaA (52.9% community- and 33.3% hospital-acquired) and ermB (17.6% community- and 33.3% hospital-acquired). The most prevalent MLS gene combination was lnuA + lsaA (five enterococcal isolates). The ermB gene encoded cMLSb phenotype, and it was identified in only one isolate that displayed iMLSb resistance phenotype. Based on the results obtained, we can conclude that the most frequent MLS resistance phenotype among enterococcal isolates was cMLSb. Surprisingly, a vancomycin-resistant enterococcal isolate was identified in a community-acquired enterococcal isolate. This study shows that enterococci may represent a major reservoir of ermB, lsaA, and lnuA genes.

Molecular Characteristic, Antibiotic Resistance, and Detection of Highly Immunoreactive Proteins of Group B Streptococcus Strains Isolated From Urinary Tract Infections in Polish Adults.

Group B streptococcus (GBS) is one of the uropathogens that causes urinary tract infections (UTIs). The aims of this article were molecular characterization, an analysis of antimicrobial susceptibility profiles, adherence to bladder endothelial cells, and the detection of immunoreactive proteins of 94 clinical strains of GBS isolated from adult Polish patients with UTI. Antibiotic susceptibilities were determined by disk diffusion. Serotyping and Alp family genes detection were studied using multiplex PCR. Genetic profiles were determined by pulsed-field gel electrophoresis. The adherence ability of the studied strains was estimated by incubation on human bladder microvascular endothelial cell line. Immunoreactive proteins were studied by immunoblotting. Antibiotic susceptibility investigation revealed that 22% of GBS strains were resistant to erythromycin, whereas 18% demonstrated resistance to clindamycin. cMLSB was present in 76% of the resistant strains, M phenotype was detected in 14%, whereas iMLSB was present for 10%. The most common serotype was serotype III (31%), followed by serotype V (27%), and serotype Ia (17%). The genes that dominated among other Alp genes were: epsilon (29%), alp2 (27%), and rib (23%). The most common co-occurring serotypes and Alp genes were: Ia and epsilon, III and rib, III and alp2, V and alp2, and V and alp3 (p < 0.001). The PFGE method showed high clonality for serotype V and cMLSB (p < 001). The PFGE method showed high clonality for serotype V. Furthermore, this serotype was significantly associated with the cMLSB phenotype (p < 0.001). The most common immunoreactive proteins demonstrated masses of 50 kDa and 45–47 kDa. Although examined GBS isolates showed high genetic diversity, immunoreactive proteins were common for most of the studied GBS isolates, which may indicate their conservation, and allows to consider them as potential immunodiagnostic markers. Although the examined GBS isolates showed high genetic diversity, immunoreactive proteins were shared by most of the studied GBS isolates. It may indicate their conservation, thus allowing to consider them as potential immunodiagnostic markers.

MecA and ermA Gene Discrepancy from Their Phenotypic Profile in Staphylococcus aureus Isolates

Objectives: Staphylococcus aureus is one of the most important bacterial pathogens in clinical practice and a primary diagnostic focus for the routine microbiology laboratory. The aim of this study was to find out the phenotypic and genotypic variations in Staphylococcus aureus isolates at a tertiary care center in Lucknow. Methods: 140 clinical isolates of S. aureus were taken in the study. Kirby–Bauer disc diffusion method was performed to identify antibiotic susceptibility testing, phenotypically methicillin-resistant Staphylococcus aureus (MRSA) were identified by using cefoxitin disc (30 μg), and inducible clindamycin resistance was identified by the presence of D-shaped zone around clindamycin and by using conventional PCR method mecA and ermA genes were identified. Results: Out of 140 clinical isolates S. aureus, 93 (66.4%) were MRSA, and 47 (33.6%) were methicillin-sensitive Staphylococcus aureus (MSSA). Phenotype iMLSb was 41 (29.3%), cMLSb phenotype was 37 (26.4%), mecA gene was present in 84 (60%), and none of the samples showed ermA gene positivity. Conclusion: As we know, the presence of the mecA gene is the major evidence for the detection of MRSA isolates. Their presence in low numbers opens the door to search for other mechanisms that may compete with mecA gene in producing resistance phenomenon. The absence of ermA gene in strains S. aureus with iMLSb and cMLSb phenotypes concluded that some other erm gene is responsible for this MLS type of resistance. Due to the frequency of MRSA strains showing the iMLSb phenotype, the use of clindamycin in erythromycin-resistant strains cannot be recommended due to the high possibility of failure in treatment with this antibiotic. J Microbiol Infect Dis 2021; 11(4):6-11.

New update on molecular diversity of clinical Staphylococcus aureus isolates in Iran: antimicrobial resistance, adhesion and virulence factors, biofilm formation and SCCmec typing.

Staphylococcus aureus is often considered as a potential pathogen and resistant to a wide range of antibiotics. The pathogenicity of this bacterium is due to the presence of multiple virulence factors and the ability to form biofilm. SCCmec types I, II and III are mainly attributed to HA-MRSA, while SCCmec types IV and V have usually been reported in CA-MRSA infections. In this study, we performed a cross-sectional study to determine the antimicrobial resistance, adhesion and virulence factors, biofilm formation and SCCmec typing of clinical S. aureus isolates in Iran. S. aureus isolates were identified using microbiological standard methods and antibiotic susceptibility tests were performed as described by the Clinical and Laboratory Standards Institute (CLSI) guidelines. Inducible resistance phenotype and biofilm formation were determined using D-test and tissue culture plate methods, respectively. Multiplex-PCRs were performed to detect adhesion and virulence factors, antibiotic resistance genes, biofilm formation and SCCmec typing by specific primers. Among 143 clinical samples, 67.8% were identified as MRSA. All isolates were susceptible to vancomycin. The prevalence of cMLSB, iMLSB and MS phenotypes were 61.1%, 22.2% and 14.8%, respectively. The TCP method revealed that 71.3% of isolates were able to form biofilm. The predominant virulence and inducible resistance genes in both MRSA and MSSA isolates were related to sea and ermC respectively. SCCmec type III was the predominant type. Data show the high prevalence rates of virulence elements among S. aureus isolates, especially MRSA strains. This result might be attributed to antibiotic pressure, facilitating clonal selection.

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.

Prevalence of Inducible Clindamycin Resistance and Nanotechnological Control of Staphylococcus aureus Clinical Isolates

Staphylococcus aureus (S. aureus) is one of the pathogens that may cause a wide range of infections in humans. Clindamycin has been considered as an important medication in treating these infections especially skin and soft tissue infections. Inducible clindamycin resistance (ICR) is a complication in treating S. aureus infections in humans. It is difficult to detect S. aureus strains expressing ICR by using standard susceptibility test methods. Recently, there is an increasing need to find alternatives to antibiotics. Nanoparticles, especially silver nanoparticles, were reported as potential alternatives for traditional antibiotics (or in combination with traditional antibiotics) against the emergence of bacterial multidrug resistance. This research aimed to study the prevalence of ICR among S. aureus clinical isolates and investigate the antibacterial effects of AgNPs solely and in combination with clindamycin against these isolates with evaluation of the acute toxicity of intraperitoneal administrated silver nanoparticles (AgNPs). Out of one hundred isolates of S. aureus studied over a period of one year, 70 isolates were identified as MRSA and 30 isolates were MSSA. Results revealed that the percentage of cMLSB, iMLSB, and MS phenotypes were 40%, 10% and 9% respectively. Overall, 41% isolates of S. aureus showed susceptibility to Erythromycin. Both iMLSB and cMLSB phenotypes were the most predominated among MRSA isolates. AgNPs was found to have strong antibacterial effect with MIC of 1μg/ml and partially synergistic activity with clindamycin towards S. aureus. Intraperitoneal administration of AgNPs was found to be moderately toxic.

Phenotypic characterization of Macrolide-Lincosamide-Streptogramin B resistance in Staphylococcus aureus

Staphylococcus aureus (S.aureus) is a prevalent organism causing infections in the community and hospital. A variety of antibiotics are used, including the Macrolide-Lincosamide-StreptograminB (MLSB) family of antibiotics in which clindamycin is the preferred agent. Widespread use of these antibiotics leads to resistance to these MLSB antibiotics; a D-test can characterize the different MLSB phenotypes. This study was taken up with an objective to perform a double disc diffusion test for detecting different phenotypes in S.aureus with particular reference to inducible clindamycin resistance. Out of a total of 174(100%) strains of S.aureus, 98(56.32%) were MRSA, and 76(43.68%) were MSSA. All isolates were tested by D-test. A total of 47(27.01%) were of cMLSB phenotype, 31(17.82%) were of iMLSB phenotype, and 96(55.17%) were of MS phenotype. The majority of MRSA strains were cMLSB phenotype(76.60%) and iMLSB phenotype (64.52%) in comparison to MSSA isolates. Although iMLSB phenotypes are present in both MRSA and MSSA, iMLSB was more in MRSA isolates. Appropriate susceptibility data is essential for a clinician to start clindamycin therapy to prevent therapeutic failures with inducible MLSB resistance in S.aureus isolates. It will be appropriate for all the clinical laboratories to report inducible Clindamycin resistance in S.aureus strains (both MRSA and MSSA), for which D-test is a reliable testing method.

MACROLIDE-LINCOSAMIDE-STREPTOGRAMIN B RESISTANCE AMONG STAPHYLOCOCCUS AUREUS IN CHITWAN MEDICAL COLLEGE TEACHING HOSPITAL, NEPAL

Objectives: Staphylococcus aureus is often linked with human infection. Clindamycin is one of the key substitute antimicrobial agents in the treatment of S. aureus, especially in methicillin-resistant S. aureus (MRSA) infections. Inducible macrolide-lincosamide-streptogramin B (iMLS B) resistance is a crucial factor in antimicrobial susceptibility testing. The intention of the research was to identify S. aureus from distinct clinical specimens and investigate the prevalence of inducible clindamycin resistance among them and also study their association with MRSA.&#x0D; Methods: A descriptive cross-sectional study was accomplished in the Dept. of Microbiology CMC-TH, Nepal from January 2018 to December 2020 with 525 non-repeated S. aureus obtained from a different clinical specimen. Antibiotic susceptibility test was performed by Kirby–Bauer disc diffusion method. MRSA was detected using cefoxitin (30 μg) and results were interpreted as stated by CLSI. “D-Test” was done by applying erythromycin (15 μg) and clindamycin (2 μg) as per CLSI guidelines. Data were analyzed using SPSS IBM version 20.&#x0D; Results: Among 525 isolates, there were 315 (60.00%) MRSA. Results of D test analysis showed that 280 (53.33%) were MLSB sensitive while 245 (46.67%) were MLSB resistant; where 80 (15.24%) iMLSB with D zone, 100 (19.05%) constitutive MLSB (cMLSB) phenotype, and 65 (12.38%) MS phenotype. Of a total of 80 iMLSB, a significant proportion of 64 (80.00%) was MRSA (p&lt;0.001). All the isolates were sensitive to vancomycin, teicoplanin, and linezolid. The prevalence of both iMLSB and cMLSB was high among MRSA.&#x0D; Conclusion: In this study, cMLSB phenotype was predominant (19.05%) followed by iMLSB phenotype (15.25%) and then MS phenotype (12.38%). Inducible iMLS B phenotypes, as well as cMLSB, are higher among MRSA. It is advisable to include “D-Test” as a part of regular antibiotic susceptibility testing to detect iMLSB resistance among S. aureus.

Have Methicillin Resistant Staphylococcus aureus clinical isolates to be also resistant to Streptogramins?

Background: Methicillin Resistant Staphylococcus aureus (MRSA) is a significant pathogen causing high morbidity and mortality. The extensive misuse of antibiotics has led to the willing of using older compounds like macrolide, lincosamides, and streptogramin (MLS) antimicrobials family. This study aimed to detect phenotypic and molecular characterization of macrolide, lincosamides, and streptogramins resistance in MRSA clinical isolates.Methods: Antimicrobial susceptibility testing of 50 MRSA clinical isolates to MLS agents and quinupristin-dalfopristin (Q -D) was performed using disk diffusion method. Besides, polymerase chain reaction was conducted for amplification of genes related to streptogramins resistance (ermA, ermB, ermC, msrA, vatA, vatB, vatC, vgaA and vgbA).Results: MLSB resistance phenotypes detected were cMLSB 9(18%), iMLSB 5(10%), MSB 8(16%), and 3(6%) isolates were LSA phenotype. No resistance to Q-D was detected in any of the tested isolates .The most prevalent MLSB resistance genes were ermC in the cMLSB and msrA in the MSB. The 3 (6%) LSA phenotype isolates expected to be SA resistant, and the 22(44%) isolates expected to be SB resistant, were sensitive to Q-D. Genes related to Q-D resistance (vatA, vatB, vatC, vgaA and vgbA genes) were not detected confirming the susceptibility of all the tested isolates to Q-D by disk diffusion method. . Conclusion: Accurate identification of phenotypic and genotypic MLSB resistance is a crucial approach to decrease the antibiotic resistance rates. The study revealed a high prevalence of the cMLSB phenotype and the most prevalent resistance determinants was ermC.

Molecular characterization of Staphylococcus aureus strains isolated from hospitalized patients based on coagulase gene polymorphism analysis: High frequency of vancomycin-intermediate S. aureus and the emergence of coagulase type II in Iran

Staphylococcus aureus is a leading cause of nosocomial infections and a significant contributor to economic and societal cost. There has been a worldwide increase in infections related to S. aureus especially with those expressing a multi-drug resistance that makes the management of the infections difficult. In the current study, it is aimed to investigate the coa gene polymorphism, prevalence, resistance and virulence pattern in S. aureus strains. A total of Ninety-five clinical S. aureus strains were investigated in the study. Antibiogram analysis was done by disk diffusion test method except for vancomycin and mupirocin (broth microdilution). Methicillin resistance was determined by using the cefoxitin disk diffusion test and subsequently PCR of the mecA gene was done. Inducible resistance to clindamycin was identified by D-test. The genetic background was characterized by coagulase typing. The overall prevalence of methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) was 67.4% and 32.6%, respectively. The multidrug resistance (MDR) rate for MRSA isolates was higher than MSSA (87.5% vs 77.4%). Intermediate resistance to vancomycin in S. aureus (VISA) was detected in 11.6% of strains which all were MRSA and isolated from intensive care unit (ICU). Resistance to mupirocin was confirmed in 30.5% of strains which of these 34.5% and 65.5% exhibited resistance to mupirocin in high and low level respectively. The overall prevalence of cMLSB, iMLSB, and MS phenotype was 45.3%, 23.2%, and 3.1% respectively. Both iMLSB and cMLSB phenotypes predominated in MRSA strains. A total of seven coa type were found in this study. coa type II was the most prevalent type (44.2%). Isolates of coa type II had higher detection of pvl and tst genes than those of other types identified. The MRSA-coa II expressed the greatest MDR while coa IVb and VIII were susceptible to all applied antibiotics. Present data revealed that spreading seven coa types of S. aureus with a high prevalence of VISA strains which is a serious threat in our region. Our study supported careful monitoring of vancomycin treatment to prevent the further spread of VISA and VRSA strains.

Inducible Clindamycin resistance and MRSA amongst Staphylococcus aureus isolates: A phenotypic detection

Now a days clinicians switch over to drug Clindamycin to treat infections. Clindamycin is belonging to lincosamide group. As frequent use of this Clindamycin develops resistance among patients and ultimately treatment failure. This present research is done to identify type of resistance like inducible or constitutive macrolide lincosamide – streptogramin B (iMLSB /cMLSB) resistance and MS (Macrolide lincosamide streptogramin) phenotypes among isolated from various samples received in Microbiology laboratory of tertiary care hospital of south Gujarat. Among various samples total 232 were isolated. And all these isolates were subjected to routine antibiotic sensitivity testing by kirbey bauer disc diffusion method. Methicillin resistance (MRSA) detected by using Cefoxitin disc. D test is performed as per Clinical and laboratory standards institute (CLSI) guidelines on all isolates. Total of 232 were isolated, among them 109 were Methicillin sensitive (MSSA) and 123 were Methicillin resistant (MRSA). Prevalence of iMLSB, cMLSB and MS phenotype were 59.34% ,15.44% and 13% in MRSA while 12.84%, 14.67% and 22.93% respectively in MSSA. This research helps to detect Clindamycin resistance among and role of D test before starting the treatment with Clindamycin. By these knowledge clinician can choose correct treatment and we can prevent a treatment failure.