cMLSB Phenotype Research Articles

Prevalence of inducible clindamycin resistance in methicillin-resistant Staphylococcus aureus: the first study in Jordan.

A high rate of infections with methicillin-resistant Staphylococcus aureus (MRSA) has been documented, in both hospital- (HA-MRSA) and community-acquired (CA-MRSA) diseases in Jordan. Erythromycin and clindamycin are considered treatments of choice. However, resistance to erythromycin with false susceptibility to clindamycin in vitro may lead to therapeutic failure. Hence, it is mandatory to study the prevalence of inducible resistance to macrolide-lincosamide-streptogramin B (iMLSB) antibiotics conferred by erm genes in those bacteria. S. aureus isolates were identified morphologically and biochemically, and MRSA were appraised using standard procedures. Induction in resistance to MLSB antibiotics among MRSA isolates was detected phenotypically using the D-test, and the presence of erm genes was revealed by polymerase chain reaction (PCR). Of 126 collected Staphylococcus isolates, 71 (56.3%) isolates were S. aureus, of which 55 (77.5%) were MRSA. A total of 43 (78.2%) MRSA-discordant isolates were resistant to erythromycin, of which 33 (76.7%) exhibited the iMLSB (D-test positive), 2 (4.7%) the MSB (D-test negative), and 8 (18.6%) the constitutive resistant (cMLSB) phenotypes. Induction of clindamycin resistance was 1.6 times greater in CA-MRSA than in HA-MRSA. Furthermore, ermA and ermC were significantly prevalent in HA-MRSA and CA-MRSA, respectively. Continuous surveillance of the MLSB resistance is important and required before the prescription of clindamycin to treat MRSA infections.

English

Widespread use of Macrolide, lincosamide and Streptogramin B (MLSB) family of antibiotics in the treatment of Staphylococcus aureus (S. aureus) has led to an increased resistance to MLSB antibiotics. The purpose of this study was to determine the frequency of MLSB resistance among clinical isolates of methicillin sensitive S. aureus (MSSA) and Methicillin resistant S. aureus (MRSA) from Mansoura University Children Hospital (MUCH), Egypt, phenotypically by using D‑test and genotypically by detection of erm genes by PCR. Different microbiological samples were collected under complete aseptic condition from patients in MUCH according to the site of infection over a period of 9 months from March 2016 to November 2016. S. aureus isolates were identified using standard microbiological methods. MRSA was detected by growth on oxacillin screen agar plate and cefoxitin disk screen test. Antimicrobial susceptibility of the isolates was determined by Kirby-Bauer disk diffusion method. S. aureus isolates that were found to be erythromycin resistant were further studied for inducible clindamycin resistance using D-zone test according to CLSI recommendations. erm genes in S. aureus isolates were detected by PCR. Among 230 S. aureus isolates, 164 were MSSA (71.3%) and 66 were MRSA (28.7%). Twenty-five MSSA (15.2%), and 37 MRSA (56.1%) isolates were erythromycin resistant. Constitutive MLSB phenotype (cMLSB) (30.3 and 4.2%) and inducible MLSB phenotype (iMLSB) (22.7 and 7.9%) were observed in MRSA and MSSA, respectively by D-zone test. The rate of iMLSB phenotype and cMLSB phenotype in MRSA was significantly higher than in MSSA isolates. The frequency of ermA, ermB and ermC genes were 72.9, 5.4 and 13.5% in MRSA isolates and 60, 4 and 12% in MSSA isolates, respectively. Screening test for of iMLSB‑resistant strains is very important by double disk diffusion test (D‑test). This phenotypic test is simple, accessible and reliable method that can be done in every laboratory and research facility, without the need of costly genetic tests. Since the treatment of patients infected with S. aureus with iMLSB phenotype with clindamycin can lead to the expansion of constitutive resistance (cMLSB) and therapy failure. Key words: Clindamycin, cMLSB, erm genes, iMLSB phenotype, MRSA, MSSA, S. aureus.

Molecular detection of genes responsible for macrolide resistance among Streptococcus pneumoniae isolated in North Lebanon.

In recent years, the increased use of macrolides was linked with the emergence of resistance Streptococcus pneumoniae worldwide. The main aim of this study was to determine the prevalence of S. pneumoniae resistant to macrolides and to identify the macrolide resistance genotypes among clinical isolates collected in North Lebanon. Disk diffusion susceptibility method was performed for 132 strains of S. pneumoniae isolated over a period of 5 years in North Lebanon. Polymerase Chain Reaction followed by pyrosequencing was carried out for confirmation of phenotypic diagnosis. The macrolide resistance genotypes were also identified by using PCR amplification of genes implicated in this resistance: erm(A), erm(B), erm(C), msr(A), lin(A) and mef(A/E). Macrolide resistance was found in 34.1% of S. pneumoniae isolates. We observed that the cMLSB phenotype (31/45, 68.9%) was the most common in these pneumococci and erm(B) was the most common resistance gene (32/45, 71.1%). This study shows that macrolide resistance in S. pneumoniae in North Lebanon is mainly related to target site modification with predominance of cMLSb phenotype but is also mediated by efflux pumps. lin(A) gene was reported for the first time in one S. pneumoniae strain in combination with erm(B) and mef(A/E) genes.

Phenotypic and Genotypic Study of Inducible Clindamycin Resistance in Clinical Isolates of Staphylococcus aureus in Tabriz, Northwest Iran

Background: Resistance to macrolide, lincosamide, and streptogramin B (MLSB) antibiotics is mediated by erm and msrA genes in Staphylococcus aureus. The expression of these genes can lead to three phenotypes, namely constitutive resistance (cMLSB), inducible resistance (iMLSB), which are resistant to macrolide, lincosamide, and streptogramin B antibiotics, and MSB phenotype, which is resistant only to macrolide and streptogramin B. Inducible clindamycin resistance is an important concern because it is not detected in routine laboratory tests. Objectives: The aim of this study was to determine the frequency of MLSB phenotypes and genotypes among 215 clinical isolates of S. aureus and then, examine their resistance to antibacterial agents, which is recommended for methicillin-resistant S. aureus (MRSA) isolates. Methods: Two hundred and fifteen non-repetitive clinical isolates of S. aureus were collected. Resistance to antibacterial agents was determined by disk diffusion and E-test methods. Susceptibility to clindamycin and erythromycin was tested by D-test. All isolates were screened by PCR for the presence of nucA, mecA, ermA, ermB, ermC, and msrA genes. Results: The prevalence of iMLSB, cMLSB and MSB phenotypes among all the isolates was determined as 10.69%, 34.42%, and 0%, respectively. In our study, iMLSB was prevalent more in methicillin susceptible S. aureus (MSSA) (11.71%) than MRSA (9.19%) isolates (P = 0.557). In contrast, the rate of cMLSB was significantly higher in MRSA (79.31%) than MSSA (3.90%) isolates (P = 0.000). No MSB phenotype was detected in our study. The most prevalent genes were ermC and ermA with 39% and 21.5% frequencies, respectively. Six isolates showed D phenotype, while the PCR results of erm genes were negative. All 215 isolates of S. aureus were negative for the presence of ermB and msrA genes. Conclusions: The rate of iMLSB in S. aureus isolates is relatively high in the Northwest Iran. Since isolates with inducible resistance may mutate and change to constitutive resistance, to prevent clinical treatment failure, D-test should be performed along with routine antibiotic susceptibility tests. In this study, ermC gene was the predominant genetic determinant for the expression of MLSB resistance. This predominance is probably due to the spread of distinctive clones (which carry ermC gene) in our region.

Streptococcus pyogenes as the cause of vulvovaginitis and balanitis in children.

Streptococcus pyogenes (group A Streptococcus) is the etiological agent of perineal infection in children, consisting of perianal infection, vulvovaginitis and balanitis. If it is not properly diagnosed and treated, it can persist for many months and can cause severe complications. Furthermore, treatment with penicillin can be followed by failures and recurrences. We report here the prevalence of S. pyogenes isolates in genital tract specimens from girls (n = 1692) with symptoms of vulvovaginitis and from boys (n = 52) with balanitis in the municipality of Nis, Southeast-Serbia (the Western Balkans) in a 10 year period, and the seasonal distribution, patient age and sensitivity to bacitracin and antimicrobial drugs used in the treatment of streptococcal infection. Streptococcal vulvovaginitis was diagnosed in 2.30% of examinees. Of those cases, 64.10% were detected from April to September, and it was most common (71.79%) in girls aged 3-7 years. Streptococcal balanitis was diagnosed in two instances: in a 4-year-old boy and in a 7-year-old boy. S. pyogenes strains resistant to bacitracin were identified in five girls. Two isolates with M phenotype and five isolates with cMLSB phenotype were identified. Streptococcal vulvovaginitis was diagnosed less often in the present study, but it was still far more common than streptococcal balanitis in childhood. Bacitracin resistance of S. pyogenes strains should be taken into account in routine microbiological identification, and the detection of S. pyogenes isolates resistant to erythromycin requires surveillance in the present geographical territory.

Molecular Characteristics of Erythromycin-Resistant Streptococcus pyogenes Strains Isolated from Children Patients in Tunis, Tunisia.

The aims of our study were to characterize phenotypically and genotypically erythromycin-resistant Streptococcus pyogenes or group A streptococci (ERGAS) isolates, to evaluate macrolide resistance and to analyze the association between emm types and virulence factors. Included in this study were all ERGAS strains isolated from 2000 to 2013 at the Children's hospital of Tunis. Antimicrobial susceptibility was performed according to the CA-SFM guidelines. Macrolide resistance genes were revealed by polymerase chain reaction (PCR) method. Virulence factor genes (pyrogenic exotoxin genes and superantigen gene) were detected by PCR, and the emm types were defined by the sequencing of the variable 5' end of the emm gene. Among the 289 GAS isolates collected, 15 (5.2%) were resistant to erythromycin; 7 of the strains were assigned to the cMLSB phenotype (46.6%); 5 harbored ermB gene alone (33.3%); and 2 strains coharbored ermB and mefA (13.3%). The remaining (53.4%) were assigned to the M phenotype and harbored the mefA gene. The frequency of detection of each toxin gene among ERGAS was 13.4% for speA (2 strains), 53.4% for speC (8 strains), and 13.4% for ssa (2 strains). Emm types 1, 58, 11, and 78 were the most frequent among ERGAS strains. The distribution of the cMLSB and M phenotypes changed over the period of investigation with a decrement of cMLSB phenotype and ermB gene that predominated between 2000 and 2006 and an increase of M phenotype and mefA gene between 2007 and 2013, but this difference was nonstatistically significant because of the low number of resistant strains. Emm types 1, 58, and 4 were only present among strains assigned to the M phenotype. However strains assigned to the cMLSB phenotype were associated to emm11, emm22, emm28, emm78, or emm76. There was diversity in emm distribution in ERGAS between the two study periods. There was diversity in emm distribution among ERGAS particularly in 2000-2006. Indeed, from 2000 to 2006, the 6 ERGAS belonged to 5 different emm types (22, 28, 76, 11, and 4), while between 2007 and 2013, seven among the nine ERGAS belonged to only 2 emm types 58 and 1. The speA gene was present only among emm1 isolates, and the ssa gene was associated with emm4 and emm78 types. All emm78, emm28, and emm11 strains harbored speC gene. Our study revealed a low frequency of ERGAS and few emm types were associated with these strains.

Serotypes, antimicrobial resistance and genotypes of Streptococcus pneumoniae associated with infections in cancer patients in Brazil

We sought to characterize pneumococcal isolates associated with bacteremia, pneumonia and meningitis in cancer patients and to estimate the coverage of the available pneumococcal vaccines. Fifty isolates recovered from 49 patients attending a cancer reference center over a 1-year period were analyzed. The prevalent serotypes were: 23F (12%), 6A (8%), 3, 4, 20, and 23A (6% each). All isolates were susceptible to chloramphenicol, levofloxacin, rifampicin, and vancomycin. Resistance or reduced susceptibility to penicillin made up 14%, and one isolate was also intermediately resistant to ceftriaxone. The three (6%) erythromycin-resistant isolates presented the M or cMLSB phenotypes and harbored the mef(A/E) gene exclusively or along with the erm(B) gene. Twenty-two (44%) isolates were closely related to 11 international clones, being strongly associated with penicillin non-susceptibility. Combined immunization with the 13-valent conjugate and the 23-valent polysaccharide vaccines might contribute to reduce (76%) the burden of the pneumococcal infections in the population investigated.

Prevalence of inducible clindamycin resistance in erythromycin resistant clinical isolates of Staphylococcus aureus and CONS at tertiary care hospital

Background & Objectives: The objective of this study was to isolate and identify Staphylococcus species from different samples clinical samples and to determine the current trend regarding the incidence and distribution of inducible clindamycin resistance in clinical isolates of Staphylococcus aureus and CONS.Materials & Methods: A total of 264 isolates of staphylococcus species were isolated from various clinical samples. Clinical samples were cultured and Staphylococcus species were identified using standard microbiological methods recommended by the American Society for Microbiology (ASM). Methicillin resistance was confirmed using cefoxitin and oxacillin disks. Inducible clindamycin resistance was identified using D-zone test.Results: Among 264 erythromycin resistant staphylococcus species, 213 (80.6%) were S. aureus and 51 (19.3%) were CONS. Out of 213 erythromycin resistant isolates of S. aureus, 140 (65.7%) were MRSA and 73 (34.2%) were MSSA whereas out of 51 erythromycin resistant isolates of CONS, 28 (54.9%) were MRCNS and 23 (45%) were MSCNS. Constitutive MLSB phenotype and Inducible MLSB phenotype was higher among both MRSA and MRCNS isolates. MS phenotype was more predominant among 11 (5.1%) MSSA and 5 (9.8%) MSCNS isolates compared to 9 (4.2%) in MRSA and 2 (3.9%) in MRCNS.Conclusion: The prevalence of constitutive & inducible clindamycin resistance in staphylococcus isolates was high among both MRSA and MRCNS. Hence the implementation of D-test routinely, will reveal the iMLSB & cMLSB phenotype & will guide the clinicians whether to use clindamycin in staphylococcal infections when erythromycin resistance is present.

Molecular epidemiology, antimicrobial susceptibility, and characterization of macrolide-resistant Streptococcus pyogenes inJapan.

Here we report the molecular epidemiology of macrolide-resistant Streptococcus pyogenes (group A streptococci, GAS) isolated from children with pharyngotonsillitis between 2011 and 2013 in Japan. In 299 isolates, 124 (41.5%) isolates were macrolide-resistant. We characterized the isolates by emm typing, multilocus sequence typing (MLST), and pulsed-field gel electrophoresis (PFGE). Of 299 isolates, 124 (41.5%) were macrolide-resistant isolates, 76 (61.3%) possessed mefA and 46 (37.1%) possessed ermB. All 76 isolates with mefA possessed msrD. There were no isolates possessed ermTR in this study. Eight emm/MLST types were observed. The predominant type was emm1/ST28 (57 isolates, 46.0%), which possessed the mefA/msrD complex, presenting as the M phenotype. The second most predominant type was emm12/ST467, which possessed ermB, presenting as the cMLSB phenotype. Of the cMLSB phenotype isolates, types emm28/ST52 and emm12/ST36 had multiple genetic backgrounds. We found high proportions of macrolide-resistant GAS in the southwestern areas of Japan.

Phenotypic and molecular characterization of resistance to macrolides, lincosamides and type B streptogramin of clinical isolates of Staphylococcus spp. of a university hospital in Recife, Pernambuco, Brazil

IntroductionThere is a mechanism of macrolide resistance in Staphylococcus spp. which also affects the lincosamides and type B streptogramins characterizing the so-called MLSB resistance, whose expression can be constitutive (cMLSB) or inducible (iMLSB) and is encoded mainly by ermA and ermC genes. The cMLSB resistance is easily detected by susceptibility testing used in the laboratory routine, but iMLSB resistance is not. Therapy with clindamycin in cases of infection with isolated iMLSB resistance may fail. ObjectiveTo characterize the phenotypic (occurrence of cMLSB and iMLSB phenotypes) and molecular (occurrence of ermA and ermC genes) profiles of MLSB resistance of clinical isolates of susceptible and methicillin-resistant Staphylococcus aureus and CNS (coagulase-negative Staphylococcus) from patients of a university hospital, in Pernambuco. MethodsThe antimicrobial susceptibility of 103 isolates was determined by the disk diffusion technique in Mueller–Hinton agar followed by oxacillin screening. The iMLSB phenotype was detected by D test. Isolates with cMLSB and iMLSB phenotypes were subjected to polymerase chain reaction (PCR) for the detection of ermA and ermC genes. ResultsThe cMLSB and iMLSB phenotypes were respectively identified in 39 (37.9%) and five (4.9%) isolates. The iMLSB phenotype was found only in four (10.8%) methicillin-susceptible S. aureus and one (4.5%) methicillin-resistant S. aureus. In the 44 isolates subjected to PCR, four (9.1%) only ermA gene was detected, a lower frequency when compared to only ermC 17 (38.6%) gene and to one (2.3%) isolate presenting both genes. ConclusionIn the Staphylococcus spp. analyzed, the ermC gene was found more often than the ermA, although the iMLSB phenotype had been less frequent than the cMLSB. It was important to perform the D test for its detection to guide therapeutic approaches.

The prevalence of genotypes that determine resistance to macrolides, lincosamides, and streptogramins B compared with spiramycin susceptibility among erythromycin-resistant Staphylococcus epidermidis.

Coagulase-negative staphylococci, particularly Staphylococcus epidermidis, can be regarded as potential reservoirs of resistance genes for pathogenic strains, e.g., Staphylococcus aureus. The aim of this study was to assess the prevalence of different resistance phenotypes to macrolide, lincosamide, and streptogramins B (MLSB) antibiotics among erythromycin-resistant S. epidermidis, together with the evaluation of genes promoting the following different types of MLSB resistance:ermA, ermB, ermC,msrA, mphC, and linA/A’. Susceptibility to spiramycin was also examined. Among 75 erythromycin-resistantS. epidermidis isolates, the most frequent phenotypes were macrolides and streptogramins B (MSB) and constitutive MLSB (cMLSB). Moreover, all strains with the cMLSB phenotype and the majority of inducible MLSB (iMLSB) isolates were resistant to spiramycin, whereas strains with the MSB phenotype were sensitive to this antibiotic. The D-shape zone of inhibition around the clindamycin disc near the spiramycin disc was found for some spiramycin-resistant strains with the iMLSB phenotype, suggesting an induction of resistance to clindamycin by this 16-membered macrolide. The most frequently isolated gene was ermC, irrespective of the MLSB resistance phenotype, whereas the most often noted gene combination wasermC, mphC, linA/A’. The results obtained showed that the genes responsible for different mechanisms of MLSB resistance in S. epidermidis generally coexist, often without the phenotypic expression of each of them.

Antimicrobial Resistance and Molecular Characteristics of Nasal Staphylococcus aureus Isolates From Newly Admitted Inpatients.

Staphylococcus aureus, or methicillin-resistant S. aureus (MRSA), is a significant pathogen in both nosocomial and community infections. Community-associated MRSA (CA-MRSA) strains tend to be multi-drug resistant and to invade hospital settings. This study aimed to assess the antimicrobial resistance and molecular characteristicsof nasal S. aureus among newlyadmitted inpatients.In the present study, 66 S. aureus isolates, including 10 healthcare-associated MRSA (HA-MRSA), 8 CA-MRSA, and 48 methicillin-sensitive S. aureus (MSSA) strains, were found in the nasal cavities of 62 patients by screening 292 newlyadmitted patients. Antimicrobial resistance and molecular characteristics of these isolates, including spa-type, sequence type (ST) and SCCmec type, were investigated. All isolates were sensitive to linezolid, teicoplanin, and quinupristin/dalfopristin, but high levels of resistance to penicillin and erythromycin were detected. According to D-test and erm gene detection results, the cMLSB and iMLSB phenotypes were detected in 24 and 16 isolates, respectively. All 10 HA-MRSA strains displayed the cMLSB phenotypemediated by ermA or ermA/ermC, while the cMLSB CA-MRSA and MSSA strains carried the ermB gene. Molecular characterization revealedall 10 HA-MRSA strains were derived from the ST239-SCCmec III clone, and four out of eight CA-MRSA strains were t437-ST59-SCCmec V. The results suggest that patients play an indispensable role in transmitting epidemic CA-MRSA and HA-MRSA strains.

Prevalence of Clindamycin resistance among Staphylococcus aureus in a tertiary care hospital in South India

Background: Staphylococcus aureus, a pyogenic bacterium, causes a wide spectrum of diseases, ranging from minor skin infections to fatal necrotizing pneumonia. The emergence and spread of MRSA (Methicillin Resistant Staphylococcus aureus), VISA (Vancomycin Intermediate Staphylococcus aureus) and VRSA (Vancomycin Resistant Staphylococcus aureus) has left us with very few antibiotics to treat Staphylococcal infections. Clindamycin is the most important antibiotic to treat infections with Methicillin Resistant Staphylococcus aureus (MRSA). In vitro routine diagnostic tests for Clindamycin susceptibility fail to detect inducible Clindamycin resistance due to erm genes resulting in treatment failures and Clindamycin sensitive strains possess msr gene. Such resistance is detected by phenotypic methods like D – test and Agar dilution method and genotypic methods like PCR detect the ermA, ermC and msrA gene. Methods: A total of 200 Staphylococus aureus isolates from various clinical samples were subjected to study by D - Test and Agar Dilution as per CLSI guidelines and gene detection was done by PCR. Result: Among the 200 Staphylococcus aureus isolates, 103 (51.5%) were erythromycin resistant. Out of which, 72 (69.9%) were MRSA and 31 (30.1%) were MSSA. Among the 72 MRSA isolates 30 (41.7%) were iMLSB phenotype, 17 (23.6%) were cMLSB phenotype and 25 (34.7%) were MS phenotype. Among the 31 (30.1%) MSSA, 14 (45.3%) were iMLSB phenotype, 15 (48.3%) were MS phenotype and 2 (6.4%) were cMLSB phenotype. Among the 63 (31.5%) Clindamycin resistant isolates 43 (68.2%) showed the presence of ermA gene and 20 (31.2%) had ermC gene. Among the 40 MS phenotype, 36 (90%) showed msrA gene. Conclusion: Keeping the mode of action, adverse reactions and pharmacokinetics of certain antibiotics like Vancomycin in mind, Clindamycin should be preferred as the drug of choice for the treatment of severe and resistant Staphyloccous aureus infections. Key Words: Inducible Clindamycin Resistanc

Distribution of erm genes among Staphylococcus aureus isolates with inducible resistance to clindamycin in Isfahan, Iran.

Background:The rising frequency of methicillin resistant Staphylococcus aureus (MRSA) has led to an increased use of antibiotics such as macrolide, lincosamide, streptogramin B (MLSB) for the treatment of S. aureus infections. Resistance to MLSB in S. aureus is commonly encoded by erm genes, which can be constitutive MLSB (cMLSB) or inducible MLSB (iMLSB). The purpose of this study was to determine the frequency of cMLSB, iMLSB, and MS phenotypes using D-test and polymerase chain reaction (PCR) methods.Materials and Methods:A total of 215 isolates of S. aureus were collected from January 2010 to May 2012 from Al-Zahra Hospital in Isfahan. PCR was performed for detection of mecA gene on all isolates using specific primers. The frequency of MLSB-resistant isolates was determined using D-test, and then a multiplex PCR was performed for detection of ermA, ermB, and ermC genes.Results:Among 215 S. aureus isolates examined, 82 (40.9%) were MRSA, and iMLSB, cMLSB, and MS resistance phenotypes had a frequency of 9 (4.18%), 58 (26.9%), and 11 (5.1%), respectively. Among nine isolates with iMLSB resistance phenotype, four isolates contained ermC gene, two isolates ermB gene, and one isolate ermA gene. Two isolates did not have any erm gene.Conclusion:In the current study, cMLSB was the most frequent phenotype and ermC was the most common gene in iMLSB resistant phenotypes.

Group A beta-hemolytic streptococcal pharyngitis and carriage rate among Egyptian children: a case-control study.

BACKGROUNDImproper prescription of antibiotics for treatment of acute pharyngitis predisposes to emergence of a carrier state and antibiotic-resistant strains of group A streptococci (GAS). We sought to identify the frequency and antimicrobial susceptibility patterns of group A streptococci among Egyptian children with acute pharyngitis compared with asymptomatic children.DESIGN AND SETTINGCase-control study conducted from September 2013 to August 2014 at a pediatric outpatient clinic in Egypt.PATIENTS AND METHODSThroat swabs were collected from children with acute pharyngitis and from asymptomatic children. We evaluated the accuracy of McIsaac scores and the rapid antigen detection test (RADT) for diagnosis of GAS pharyngitis with throat culture as a reference test. Antimicrobial susceptibility testing of GAS isolates was done by the disc diffusion method.RESULTSOf 142 children with acute pharyngitis (cases) and 300 asymptomatic children (controls) (age range, 4–16 years), GAS pharyngitis was diagnosed in 60/142 children (42.2%); 48/300 (16%) were found to be carriers. All GAS isolates in the case group were sensitive to penicillin; however, an MIC90 (0.12 μg/mL) for penicillin is high and an alarming sign. The resistance rate to macrolides was 70% with the cMLSB phenotype in 65.1%. The sensitivities and specificities were 78.3% and 73.2% for McIsaac score of ≥4 and 81.1% and 93.9% for RADT, respectively. GAS isolates in the control group were 100% sensitive to penicillin, while 12.5% and 37.5% were resistant to macrolides and tetracycline, respectively.CONCLUSIONAn increased MIC90 for GAS isolates to penicillin is an alarming sign. A high frequency of resistance to macrolides was also observed.

Decline in macrolide resistance rates among Streptococcus pyogenes causing pharyngitis in children isolated in Italy.

Macrolides are often used to treat group A streptococcus (GAS) infections, but their resistance rates reached high proportions worldwide. The aim of the present study was to give an update on the characteristics and contemporary prevalence of macrolide-resistant pharyngeal GAS in Central Italy. A total of 592 isolates causing pharyngitis in children were collected in the period 2012–2013. Clonality was assessed by emm typing and pulsed-field gel electrophoresis (PFGE) for all macrolide-resistant strains and for selected susceptible isolates. Genetic determinants of resistance were screened by polymerase chain reaction (PCR). Forty-four GAS were erythromycin-resistant (7.4 %). Among them, 52.3 % and 50 % were clindamycin- and tetracycline-resistant, respectively. erm(B)-positive isolates (52.3 %) expressed the constitutive cMLSB phenotype. mef(A) and its associated M phenotype were recorded in 40.9 % of the cases. The remaining erm(A)-positive isolates expressed the iMLSB phenotype. Seventeen tetracycline-resistant isolates carried tet(M) and five isolates carried tet(O). Twenty-five emm types were found among all strains, with the predominance of emm types 12, 89, 1, and 4. Eleven emm types and 12 PFGE clusters characterized macrolide-resistant strains, with almost two-thirds belonging to emm12, emm4, and emm11. Macrolide-susceptible and -resistant emm types 12, 89, 11, and 4 shared related PFGE profiles. There was a dramatic decline in macrolide resistance in Central Italy among pharyngeal GAS isolates in 2012–2013 when compared to previous studies from the same region (p < 0.05), although macrolide consumption remained stable over the past 15 years. We observed a decrease in the proportion of macrolide-resistant strains within emm types commonly associated with macrolide resistance in the past, namely emm12, 1, and 89.

Clinical significance of serotype V among infants with invasive group B streptococcal infections in South Korea

Group B Streptococcus (GBS) strains are classified by the polysaccharide capsule, which is an important virulence factor and stimulator of antibody-associated immunity. As GBS infections in neonates may be life-threatening, GBS screening and intrapartum antibiotic prophylaxis have been implemented for prevention. In Korea, there are few reports on the GBS serotype distribution and antibiotic resistance patterns because GBS screening and intrapartum prophylaxis are not done routinely. The serotype distribution and antibiotic resistance of GBS in infants in Korea with invasive bacterial infections were examined for the 19-year period 1995-2013. Isolates obtained previously from hospitals located in three different regions were analyzed for capsular serotype by PCR and sequencing and for antimicrobial susceptibility. Among 56 isolates serotyped, the most common serotypes were III (44.6%) and V (28.6%), followed by Ia (14.3%), Ib (10.7%), and VI (1.8%). No penicillin-resistant strains were detected, however 51.8% of the strains had resistance to erythromycin and 55.4% showed clindamycin resistance. Resistance was highest (93.8%) to both erythromycin and clindamycin for serotype V; all 15 isolates resistant to erythromycin were cMLSB phenotype and had a high level of resistance to both erythromycin and clindamycin with MIC levels >256μg/ml, and all but one were positive for ermB. In this study in Korea, serotype V was identified in a relatively large proportion of GBS isolates and this serotype showed a high level of resistance to erythromycin and clindamycin in a statistically significant majority. Continuous monitoring of changes in clinical disease and molecular characteristics is important for the treatment and prevention of invasive GBS disease in infants.

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

Study of Serotypes, Susceptibility to Macrolide and Virulence and Resistance Molecular Profiles in Invasive Strains of &amp;lt;i&amp;gt;Streptococcus agalactiae&amp;lt;/i&amp;gt; in Two Argentine Provinces

A study of invasive strains of Streptococcus agalactiae (GBS) from Cordoba and Misiones, Argentina; was conducted to determine serotypes, the susceptibility to macrolides and molecular profiles of virulence and resistance. We studied 17 strains, recovered from cerebrospinal fluid, blood and cellulite and, a strain of trophoblastic remnants from Misiones. The serotypes were determined by agglutination with sera and phenotypes of resistance to macrolide-lincosamide-streptogramin B (MLSB), were determined with the double-disk test (D-test). The confirmation was performed by E-test by ERI and CLI respectively that determined the minimum inhibitory concentration (MIC). Results were interpreted as recommended by the Clinical and Laboratory Standards Institute (CLSI) 2013. Resistance genes: ermB, ermTR and mefA and the virulence genes: bac, bca, rib, lmb, hylB, scpB, fbsA, fbsB and cylB were investigated by conventional PCR. Serotype III (50%) and Ia (50%) were detected in Cordoba. One strain showed cMLSB phenotype, confirmed by MIC. The same strains showed a resistance gene ermB. All studied virulence genes were detected in 100% of these strains. In Misiones, serotypes were III (72.7%), Ia (18.2%) and Ib (9.1%). All strains were susceptible to CLI and ERI by D-test, confirmed by MIC. None of the strains showed resistance genes. Virulence genes bca, rib, hylB, lmb, fbsA, fbsB and cylB were detected in 100% of the strains, bac in 81.8% and scpB in 90.9%. Our results are in accordance with international data, associating higher frequency of serotype III of invasive neonatal disease followed by Ia. The presence of serotype Ib could indicate a regional difference for Misiones. We highlight the macrolides susceptibility in strains of Misiones and consistency in the results for D-test, MIC and PCR for the single strain resistant phenotype cMLSB from Cordoba. The virulence genes studied were presented with high frequency as expected for invasive strains.

Determination of antimicrobial resistance profile and inducible clindamycin resistance of coagulase negative staphylococci in pediatric patients: the first report from Iran.

Currently, coagulase negative staphylococci (CoNS) have got much attention as a serious health problem especially in neonates and children. High incidence of antibiotic resistance, in particular methicillin resistance, has complicated the treatment of these organisms. The aim of this study is to determine the susceptibility to different antimicrobial agents and the prevalence of macrolideslincosamides-streptogramins B (MLSB) resistance in CoNS isolates obtained from pediatric patients. Totally 157 CoNS isolates from various clinical samples were examined for antibiotic resistance using disk diffusion and E-test methods. Double-disk test was applied to detect constitutive and inducible MLSB resistance (cMLSB and iMLSB) phenotypes. Resistance to methicillin was seen in 98 (62.4%) isolates. All isolates were susceptible to vancomycin and linezolid. The prevalence of resistance to antibiotics tested was as follows: fusidic acid (n=58, 36.9%), gentamicin (n=73, 46.5%), ciprofloxacin (n=81, 51.6%), clindamycin (n=112, 71.3%), erythromycin (n=129, 82.2%) and trimethoprim/sulfamethoxazole (n=133, 84.7%). iMLSB phenotype was seen in 14 (8.9%) isolates, and 18 (11.5%) and 98 (62.4%) isolates showed MS and cMLSB phenotypes, respectively. We observed that high overall antibiotic resistance rates were associated significantly with methicillin resistance. Conversely, iMLSB phenotype was correlated neither with methicillin resistance nor with invasiveness. Given the similarity observed between the prevalence of iMLSB and MS phenotypes, the performance of disk diffusion induction test is strongly recommended in our region.