Macrolide-lincosamide-streptogramin B resistance phenotypes and their associated genotypes in Staphylococcus aureus isolates from a tertiary level public hospital of Uruguay / Fenotipos de resistencia a macrólidos lincosamidas-estreptograminas B y sus genotipos asociados en Staphylococcus aureus aislados en un hospital público de nivel terciario en Uruguay

Abstract This study was undertaken to investígate the resistance phenotypes to macrolide-lincosamide-streptogramin B (MLSb) antibiotics and their associated genotypes in isolates of Staphylococcus aureus. We analyzed one hundred, consecutive, non-duplicate isolates (methicillin-susceptible MSSA, n = 53 and methicillin-resistant MRSA, n =47) obtained from var-ious clinical samples between July 2012 to December 2013. The resistance profile to MLSb antibiotics was determined by phenotypic methods and the resistance genes were detected by PCR assays. All of the isolates were subjected to pulsed-field gel electrophoresis (SmaI-PFGE). The overall prevalence of resistance to MLSb antibiotics was 38% and the resistance phenotype distribution was as follows: cMLSb, 22%; iMLSB, 10%; MSb, 5% and L, 1%. We detected ermA, ermC, ermB and mrsA/B genes in these resistant isolates. The single ermA gene was commonly observed mainly in those with a cMLSb R phenotype, whereas the combination ermA and ermC was more commonly observed in isolates with inducible expression. The patterns of SmaI-PFGE suggest a great genetic diversity in both MRSA and MSSA resistant to MLSb antibiotics. The results demonstrate the local presence of S. aureus resistant to MLSb antibiotics and its most frequently described responsible genes. Some of these isolates, especially those with the iMLSB phenotype, may be associated with therapeutic failure. Therefore, efforts should be directed to the correct detection of all MLSb resistant isolates using appropriate laboratory tests. PFGE results reveal a wide spread of resistance genes rather than the circulation of S. aureus clones resistant to MLSb antibiotics.

Resumen Los objetivos de este estudio fueron investigar en Staphylococcus aureus la presencia de fenotipos resistentes a los antibióticos macrólidos, lincosamidas y estreptograminas tipoB (MLSb) y conocer sus genotipos responsables. Analizamos 100 aislamientos consecutivos, no duplicados (53 sensibles a meticilina [MSSA] y 47 resistentes a meticilina [MRSA]), obtenidos entre 2012 y 2013 a partir de diferentes muestras clínicas. El perfil de resistencia a los antibióticos MLSb fue determinado por métodos fenotípicos y los genes de resistencia se detectaron por PCR. Todos los aislamientos fueron comparados por SmaI-PFGE. La prevalencia global de resistencia a los antibióticos MLSB fue del 38% y la distribución de los fenotipos de resistencia fue la siguiente: cMLSB, 22%; iMLSB, 10%; MSB, 5%; L, 1%. Se detectaron los genes ermA, ermC y mrsA/B en los aislamientos resistentes. El gen ermA se observó, sobre todo, en aislamientos con fenotipo resistente constitutivo R (cMLSB), mientras que la combinación ermA y ermC se detectó principalmente en aislamientos con resistencia inducible (iMLSB). Los patrones de Smal-PFGE sugieren una gran diversidad genética en los aislamientos resistentes a los antibióticos MLSb, tanto MRSA como MSSA. Los resultados demuestran la presencia local de S. aureus resistentes a los antibióticos MLSB y de sus genes responsables más frecuentemente descritos. Estos cultivos, especialmente aquellos con fenotipo resistente iMLSB, pueden asociarse con fallas terapéuticas. Por lo tanto, los esfuerzos deben dirigirse a la correcta detección de todos los cultivos resistentes a MLSB utilizando pruebas de laboratorio adecuadas. Los resultados de Smal-PFGE sugieren una amplia diseminación de genes de resistencia, más que la circulación de clones resistentes a los antibióticos MLSB.

Domestic wastewater treatment plants as sources of macrolide-lincosamide-streptogramin B- and penicillin-resistant Staphylococcus aureus in Brazil / Plantas de tratamiento de aguas residuales domésticas como fuentes de Staphylococcus aureus resistente a macrólidos-lincosamida-estreptogramina B- y penicilina en Brasil / Estações de tratamento de águas residuais domésticas como fontes de Staphylococcus aureus resistente a macrolídeo-lincosamida-estreptograma e B- e penicilina no Brasil

SUMMARY Staphylococcus aureus is one of the main bacteria that affect human health. Its reduced susceptibility to beta-lactam antibiotics has driven the clinical use of macrolides and lincosamides. However, the presence of macrolide-lincosamide-streptogramin B (MLSB)-resistant S. aureus strains is increasingly common. Wastewater treatment plants (WWTPs) are the main anthropogenic source of resistance determinants. However, few studies have assessed the importance of this environment on the dissemination of MLSB-resistant S. aureus strains. Thus, we aimed to evaluate the impact of a domestic WWTP on the resistance to MLSB and penicillin in S. aureus in southeast Brazil. Of the 35 isolates tested, 40.6% were resistant to penicillin. Resistance to erythromycin (8.6%) and quinolones (2.8%) was less common. Despite the low rate of resistance to clindamycin (2.8%), many isolates showed reduced susceptibility to this antibiotic (57.1%). Regarding the resistance phenotypes of staphylococci isolates, inducible MLSB resistance (D-test positive) was found in two isolates. In addition, 27 S. aureus isolates showed the ability to produce penicillinase. In this article, we report for the first time the importance of WWTPs in the dissemination of MSLB resistance among S. aureus from southeast Brazil.

RESUMEN Staphylococcus aureus es una de las principales bacterias que afectan la salud humana. Su susceptibilidad reducida a los antibióticos betalactámicos ha impulsado el uso clínico de macrólidos y lincosamidas. Sin embargo, la presencia de cepas resistentes a macrólido-lincosamida-estreptogramina B (MLSB) de S. aureus es cada vez más común. Las plantas de tratamiento de aguas residuales (PTAR) son la principal fuente antropogénica de determinantes de resistencia. Sin embargo, pocos estudios han evaluado la importancia de este entorno en la diseminación de cepas de S. aureus resistentes a MLSB. Nuestro objetivo fue evaluar el impacto de una PTAR doméstica en MLSB y la resistencia a la penicilina en S. aureus en el sureste de Brasil. De los 35 aislamientos analizados, el 40,6% eran resistentes a la penicilina. La resistencia a la eritromicina (8,6%) y quinolonas (2,8%) fue menos común. A pesar de la baja tasa de resistencia a la clindamicina (2,8%), muchos aislamientos mostraron sensibilidad reducida a este antibiótico (57,1%). Con respecto a los fenotipos de resistencia de los aislamientos de estafilococos, la resistencia inducible a MLSB (prueba D positiva) se encontró en dos aislamientos. Además, 27 aislamientos de S. aureus mostraron la capacidad de producir penicilinasa. En este artículo informamos, por primera vez, la importancia de las PTAR en la difusión de la resistencia a MSLB entre S. aureus del sureste de Brasil.

RESUMO O Staphylococcus aureus é uma das principais bactérias que afetam a saúde humana. Sua reduzida suscetibilidade aos antibióticos beta-lactâmicos tem impulsionado o uso clínico de macrolídeos e lincosamidas. No entanto, a presença de cepas de S. aureus resistentes a macrolídeo-lincosamida-estreptogramina B (MLSB) é cada vez mais comum. As estações de tratamento de esgoto (ETEs) são a principal fonte antropogênica de determinantes de resistência. No entanto, poucos estudos avaliaram a importância desse ambiente na disseminação de cepas de S. aureus resistentes ao MLSB. Assim, nosso objetivo foi avaliar o impacto de uma ETE doméstico na resistência ao MLSB e à penicilina em S. aureus no sudeste do Brasil. Dos 35 isolados testados, 40,6% eram resistentes à penicilina. Resistência à eritromicina (8,6%) e quinolonas (2,8%) foi menos comum. Apesar da baixa taxa de resistência à clindamicina (2,8%), muitos isolados apresentaram sensibilidade reduzida a esse antibiótico (57,1%). Em relação aos fenótipos de resistência dos isolados de estafilococos, a resistência induzível ao MLSB (D-teste positivo) foi encontrada em dois isolados. Além disso, 27 isolados de S. aureus mostraram a capacidade de produzir penicilinase. Neste artigo relatamos pela primeira vez a importância das ETEs na disseminação da resistência do MSLB entre S. aureus do sudeste do Brasil.

Detection of inducible clindamycin resistance in Staphylococcus aureus from various samples in a tertiary care hospital

Background: The increasing frequency of MRSA infections and rapidly changing patterns in antimicrobial resistance, led to renewed interest in the usage of Macrolides-Lincosamide-Streptogramin B (MLSB) antibiotics to treat Staphylococcus aureus infection. Clindamycin is an important drug used in the treatment of MRSA and MSSA infection. The aim of this study was to determine inducible and constitutive clindamycin resistance among clinical isolates of Staphylococcus aureus by D-test.Methods: During a period of 6 months from July 2018 to December 2018, a total of 100 Staphylococcus aureus isolated from different clinical samples were subjected to routine antibiotic sensitivity testing by Kirby Bauer’s disc diffusion method. Methicillin-resistance was determined by using the cefoxitin (30 µg) disc. Incidence of MLSBc and MLSBi in Staphylococcus aureus isolates by D-test as per CLSI guidelines.Results: Out of 100 isolates of Staphylococcus aureus obtained from 350 clinical samples, 70(70%) were found to be MRSA and 30(30%) were MSSA. Among 100 Staphylococcus aureus isolates, 40% isolates showed MLSBi resistance, 28% isolates showed MLSBc resistance, 6% isolates showed MS phenotype and 26% isolates showed Sensitive phenotype. MLSBc and MLSBi were found to be higher in MRSA as compared to MSSA (21%, 27% and 7%, 10% respectively). All clinical isolates showed 100% sensitivity to Vancomycin and Linezolid in routine antibiotic susceptibility testing.Conclusions: Continuous surveillance of the MLSB resistance is important and required before the prescription of clindamycin to treat MRSA infections.

Prevalence of Inducible Clindamycin Resistance and Methicillin Resistance among Staphylococcus Species from Various Clinical Samples in a Tertiary Care Hospital of Eastern India

Staphylococcus species is an important cause of nosocomial and community acquired infections worldwide. Clindamycin is an alternative agents used to treat erythromycin resistant Staphylococcal infections. Clinical failure also reported due to various mechanisms of resistance to MLSB antibiotics. Accurate identification of clindamycin resistance is important to prevent therapeutic failure. Unfortunately, inducible Clindamycin resistance is not detected by standard susceptibility tests. Aims: The aim of the present study was to detect the prevalence of inducible clindamycin and methicillin resistance among clinical isolates of Staphylococcal species via antibiotic sensitivity test form various clinical samples. Methods: Total 153 Staphylococcal isolates were tested for antimicrobial susceptibility testing by as per guidelines. For detection of MRSA cefoxitin disc and for inducible clindamycin resistance, D test was performed. Results: Out of 153 samples, 119 were Staphylococcus aureus and 34 were Coagulase negative Staphylococcus (CoNS). Out of which 62.18 % were MRSA and 37.81 % were MSSA. Inducible MLSB phenotype was detected in 31.09 %, MS phenotype and constitutive MLSB phenotype in 42.85 % and 10.08 %. Conclusion: So it can be concluded from our study that D-test should be routinely performed in microbiology laboratory for every Staphylococcal isolates otherwise clindamycin resistance may misinterpreted as clindamycin sensitive resulting in therapeutic failure.

Analysis on effect of blood anti-D antibody detection in infusing RhD positive homotype RBC for patients with RhD negative / 国际检验医学杂志

Objective To investigate the anti-D antibody level after infusing homotype RhD positive RBC in the patient with RhD negative.Methods The clinical data in 20 cases of RhD negative infusing homotype RhD positive RBC in our hospital from January 2010 to January 2016 were collected.The anti-D antibody levels before blood infusion and on 10,20,30,90 d after blood infusion and the titers in the patients with RhD positive were analyzed.Results Among 20 cases of RhD negative infusing RhD positive homotype RBC blood,6 cases were RhD positive within 90 d after blood infusion,in which the RhD positive rates were 25%(3/12) in male and 37.5%(3/8) in female.The anti-D antibody titers in 3 cases of RhD positive were 35,278 and 508 respectively.Conclusion Infusing RhD positive RBC blood in the patients with RhD negative can stimulate the immune mechanism,generates the anti-D antibody at RBC surface.Moreover the RBC phenotype in partial patients with RhD negative may change.

Methicillin resistance & inducible clindamycin resistance in Staphylococcus aureus.

Background & objectives: Methicillin resistant Staphylococcus aureus (MRSA) isolates with inducible clindamycin resistance (iCR) are resistant to erythromycin and sensitive to clindamycin on routine testing and inducible clindamycin resistance can only be identified by D-test. This study was aimed to detect methicillin resistance and iCR among S. aureus isolates, effectiveness of some commonly used antibiotics and correlation between methicillin resistance and iCR. Methods: The present cross-sectional study included 46 S. aureus isolates subjected to Kirby-Bauer’s disk diffusion method for antibiotic susceptibility testing (AST) to estimate MRSA and resistance to some commonly used antibiotics. D-test was employed to detect iCR. Results: Eleven of the 46 (23.9%) isolates tested were MRSA. Overall, 19 (41.3%) isolates showed of iCR. Vancomycin and linezolid were found to be 100 per cent effective. A positive Karl-Pearson’s coefficient of correlation (0.89) between methicillin resistance and iCR was obtained. Interpretation & conclusions: Detection of iCR is important for the use of clindamycin in MRSA infections. Methicillin resistance and iCR appear to be clinically unrelated.

Inducible clindamycin resistance in Staphylococcus aureus: Reason for treatment failure.

Emergence of methicillin resistance in Staphylococcus aureus (S.aureus) has left us with very few therapeutic alternatives available to treat staphylococcal infection. The widespread use of macrolide-lincosamide-streptogramin B (MLSB) antibiotics has led to an increase in number of staphylococcal strains acquiring resistance to MLSB antibiotics. This study was done to investigate the infections by hospital and community acquired “erythromycin- induced clindamycin resistant” strains or D-test positives of clinical isolates of Staphylococcus aureus (S.aureus) in a hospital. Three hundred isolates of S.aureus were subjected to routine antibiotic susceptibility testing including Cefoxitin (30µg) by modified disc diffusion method. Inducible resistance to clindamycin in S.aureus was tested by D-test as per CLSI guidelines. Among 300 S.aureus isolates, 114 (38%) were methicillin resistant Staphylococcus aureus (MRSA) and 186 (62%) methicillin susceptible Staphylococcus aureus (MSSA). Forty one (13.67%) isolates showed induced clindamycin resistance, 49(16.33%) showed constitutive resistance and 94 (31.33%) showed the MS phenotype. Inducible resistance and constitutive resistance were found to be higher in MRSA compared to MSSA (22.81%, 23.68% and 8.1%, 11.8% respectively). D-test should be included as a part of routine antibiotic susceptibility testing to detect induced clindamycin resistance to prevent treatment failure.

Detection of inducible clindamycin resistance and susceptibilities to other antimicrobial agents in clinical isolates of Staphylococcus aureus.

Background: The resistance to antimicrobial agents among staphylococci is an increasing problem. Clindamycin is commonly used for the treatment of skin and soft tissue infections produced by Staphylococcus aureus and its widespread use has led to its resistance by different mechanisms & hence it is important to detect this. In vitro, routine tests may fail to detect inducible clindamycin resistance due to erm genes resulting in treatment failure, thus necessitating the need to detect such resistance by a simple D-test on a routine basis. Objective: To find out the percentage of inducible clindamycin resistance in our hospital using D-test and their susceptibilities to other antimicrobial agents to guide therapy. Methods: One hundred and two S. aureus isolates from various clinical samples were evaluated and methicillin resistance was determined using cefoxitin (30 mcg) disc and inducible resistance to clindamycin was detected by D-test as per CLSI guidelines. Antibiotic susceptibility to other antimicrobial agents was done by Kirby Bauer’s disc diffusion method. Results: Nineteen (18%) isolates showed inducible clindamycin resistance, 12 (11%) showed constitutive resistance and 22 (21%) showed MS phenotype. All the three resistance patterns were higher in Methicillin Resistant Staphylococcus aureus (MRSA) as compared to Methicillin Sensitive Staphylococcus aureus (MSSA). Conclusion: Our study showed, that D-test should be used as a mandatory method in routine disc diffusion testing to detect inducible clindamycin resistance for optimum treatment of patients.

Clindamycin Resistance among Staphylococcus Aureus Isolated at Mbarara Regional Referral Hospital, in South Western Uganda.

Aims: The study was conducted to determine the prevalence of Clindamycin (CL) resistance and antimicrobial susceptibility among clinical isolates of Staphylococcus aureus (S. aureus) from Mbarara Regional Referral Hospital (MRRH) in Southwestern Uganda. Study Design: Laboratory based cross sectional study. Place and Duration of the Study: The study was conducted at the Microbiology department of Mbarara Regional referral hospital between November 2012 and December 2013. Methodology: In our study, we recruited 300 S. aureus isolates that were stored in the laboratory and were obtained from different clinical samples. The isolates were tested for antimicrobial susceptibility by phenotypic methods and for the genotypic expression of Macrolide Lincosamide StreptograminB (MLSB) resistance genes (ermA, ermB, ermC, and msrA). The D-test was also performed. Results: Phenotypically, a total of 109 (36%) S. aureus isolates were resistant to CL, of which 9 (3%) were constitutively resistant while 100 (33.3%) were inducibly resistant. Genotypicaly, 134/300 (44.7%) isolates possessed at least one of the MLSB resistance genes. 23/300 (7.7%) tested positive for ermB, 98/300 (32.7%) tested positive for the ermC and 43/300 (14.3%) tested positive for the msrA genes with none possessing the ermA gene. Isolates were highly resistant to Sulfamethoxazole/trimethoprim, Erythromycin and Oxacillin with moderate resistance to Vancomycin and Imipenem and least resistance to Linezolid Conclusion: S. aureus resistance to CL was high in this set up. There was also high resistance to Sulfamethoxazole/trimethoprim, Erythromycin and Oxacillin but low resistance to Linezolid.

Evaluation of constitutive and inducible resistance to clindamycin in clinical samples of Staphylococcus aureus from a tertiary hospital

Introduction Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) have become common in hospitals and the community environment, and this wide resistance has limited patient treatment. Clindamycin (CL) represents an important alternative therapy for infections caused by S. aureus. Antimicrobial susceptibility testing using standard methods may not detect inducible CL resistance. This study was performed to detect the phenotypes of resistance to macrolides-lincosamides-streptogramin B (MLSB) antibiotics, including CL, in clinical samples of S. aureus from patients at a tertiary hospital in Santa Maria, State of Rio Grande do Sul, Brazil. Methods One hundred and forty clinical isolates were submitted to the disk diffusion induction test (D-test) with an erythromycin (ER) disk positioned at a distance of 20mm from a CL disk. The results were interpreted according to the recommendations of the Clinical and Laboratory Standards Institute (CLSI). Results In this study, 29 (20.7%) of the 140 S. aureus samples were resistant to methicillin (MRSA), and 111 (79.3%) were susceptible to methicillin (MSSA). The constitutive resistance phenotype (cMLSB) was observed in 20 (14.3%) MRSA samples and in 5 (3.6%) MSSA samples, whereas the inducible resistance phenotype (iMLSB) was observed in 3 (2.1%) MRSA samples and in 8 (5.8%) MSSA samples. Conclusions The D-test is essential for detecting the iMLSB phenotype because the early identification of this phenotype allows clinicians to choose an appropriate treatment for patients. Furthermore, this test is simple, easy to perform and inexpensive. .

Evaluation of phenotypic tests for the detection of AmpC beta-lactamase in clinical isolates of Escherichia coli.

Background: AmpC beta lactamases are cephalosporinases that confer resistance to a wide range of beta lactam drugs thereby causing serious therapeautic problem. As there are no CLSI guidelines for detection of AmpC mediated resistance in Gram negative clinical isolates and it may pose a problem due to misleading results, especially so in phenotypic tests. Although cefoxitin resistance is used as a screening test, it does not reliably indicate AmpC production. Materials and Methods: We planned a study to determine the occurrence of AmpC beta lactamase in hospital and community, clinical isolates of Escherichia coli and simultaneously evaluate different phenotypic methods for detection of AmpC beta lactamases. Results: It was observed that 82.76% isolates were ESBL positive and 59% were cefoxitin screen positive. Using phenotypic confi rmatory tests the occurrence of Amp C beta lactamases was found to be 40% and 39% by inhibitor based method using boronic acid (IBM) and modifi ed three dimensional test (M3D) respectively. Conclusion: Both the test showed concordant result. Co-production was observed in 84.62% isolates Screening of ESBL and Amp C can be done in routine clinical microbiology laboratory using aztreonam and IBM respectively as it is a simple, rapid and technically less demanding procedure which can be used in all clinical laboratories.

A report on infection dynamics of inducible clindamycin resistance of Staphylococcus aureus isolated from a teaching hospital in India

<p><b>OBJECTIVE</b>To investigate the infection of hospital- and community-acquired "erythromycin-induced clindamycin resistant" strains or D-test positives of clinical isolates of Staphylococcus aureus (S. aureus) (with and without methicillin resistance) in a hospital.</p><p><b>METHODS</b>Strains of S. aureus isolated from clinical specimens were subjected to D-test and antibiotic profiling.</p><p><b>RESULTS</b>Of the total 278 isolates, 140 (50.35%) were D-test positives and the rest were D-test negatives. Further, of 140 (100%) positives, 87 (62.14%) and 53 (37.85%) strains were from males and females, respectively. Of 140 (100%) positives, 117 (83.57%) were methicillin resistant S. aureus and 23 (16.42%) were methicillin sensitive S. aureus; of 140 strains, 103 (73.57%) strains from persons with and 37 (26.42%) were without related infections; of 140 strains, 91 (65%) and 49 (35%) were from hospital- and community-acquired samples, respectively. In 140 strains, 118 (84.28%) with comorbidities and 22 (15.71%) without comorbidities cases were recorded; similarly, persons with prior antibiotic uses contributed 108 (77.14%) and without 32 (22.85%) positive strains. These binary data of surveillance were analyzed by a univariate analysis. It was evident that the prior antibiotic uses and comorbidities due to other ailments were the determinative factors in D-test positivity, corroborated by low P values, P=0.001 1 and 0.002 4, respectively. All isolates (278) were resistant to 17 antibiotics of nine groups, in varying degrees; the minimum of 28% resistance for vancomycin and the maximum of 97% resistance for gentamicin were recorded. Further, of 278 strains, only 42 (15.1%) strains were resistant constitutively to both antibiotics, erythromycin resistant and clindamycin resistant, while 45 (16.2%) strains were constitutively sensitive to both antibiotics (erythromycin sensitive and clindamycin sensitive). Further, of the rest 191 (68.7%) strains were with erythromycin resistant and clindamycin resistant, of which only 140 (50.35%) strains were D-test positives, while the rest 51 (18.34%) strains were D-test negatives.</p><p><b>CONCLUSIONS</b>In view of high prevalence of D-test positive S. aureus strains, and equally high prevalence of multidrug resistant strains both in community and hospital sectors, undertaking of D-test may be routinely conducted for suppurative infections.</p>

Detection of various types of resistance patterns and their correlation with minimal inhibitory concentrations against clindamycin among methicillin-resistant Staphylococcus aureus isolates.

Purpose: The macrolide lincosamide streptogramin B (MLS B ) family of antibiotics serves as an alternative for the treatment of skin and soft tissue infections caused by methicillin-resistant Staphylococcus aureus (MRSA). However, resistance to clindamycin too has emerged, which is of two types, inducible and constitutive. Therapeutic failure is common with inducible type of clindamycin resistance. This study was done to determine the various clindamycin resistance patterns in MRSA isolates and to compare them with minimal inhibitory concentration (MIC) of clindamycin. Materials and Methods: Fifty MRSA isolates were studied by disc approximation test (D test) to detect inducible iMLS B resistance and MIC by agar dilution technique. Results: Of the 50 isolates, 34 were sensitive to both clindamycin and erythromycin. 16 isolates showed different sensitivity patterns; nine of these were positive for D zone indicating inducible iMLS B resistance, five were positive for constitutive MLS B resistance and two showed possible efflux mechanism for macrolide resistance. Out of the 34 sensitive isolates, 5 showed isolated colonies (subpopulation) inside the clindamycin-sensitive zone. When these sub-populations were tested further, two were constitutive MLS B phenotypes, two were inducible iMLS B and one was HD (hazy D zone), which is D + with growth up to clindamycin disc (which is also considered as constitutive MLS B phenotype). Seven isolates showed an MIC of ≥4 μg/ml to clindamycin in spite of being susceptible to both erythromycin and clindamycin by Kirby Bauer disc diffusion technique. Out of these seven isolates, five were those which grew as subpopulation inside the clindamycin-sensitive zone. Conclusion: Detection of iMLS B resistance among MRSA helps to avoid treatment failure with clindamycin. Studying the subpopulation inside the clindamycin-sensitive zone raises the question of existence of hetero-resistance or some other mechanism, which needs further study.

Acquired Dyschromatopsia among Workers Exposed to Acetone and Isopropyl Alcohol (IPA) / 대한산업의학회지

OBJECTIVES: The purpose of this study was to examine the correlation between exposure to acetone and isopropyl alcohol (IPA) and the acquisition dyschromatopsia. METHODS: A study was performed on exposure group of 116 people exposed to and a group of 36 people not exposed to organic solvents were selected and examined. Their smoking and alcohol habits, symptoms, and exposure history were surveyed through questionnaires and interviews. Then dyschromatopsia was evaluated with the Lanthony D-15 d test in a room with standardized intensity of illumination. RESULTS: The statistical prevalence of dyschromatopsia was significantly higher in the exposed group (30.2%) compared to that found in the control group (19.4%). Out of the 116 subjects in the exposed group, 30 people had acquired dyschromatopsia (25.86%). The variables affecting the color confusion index, such as age, exposure, and the duration of exposure, were statistically significant variables. CONCLUSIONS: He prevalence of dyschromatopsia was found to be not significantly higher in the group with exposure to organic solvents compared to that found in the control group. In addition, a statistically significant correlation was found between exposure to organic solvents and the color confusion index.

Significance of MRSA strains in community associated skin and soft tissue infections.

The study was conducted to determine the antibiotic susceptibility profile of community-associated methicillin resistant Staphylococcus aureus (CAMRSA) strains isolated from infections. S. aureus strains were isolated from clinical specimens using the standard procedures. CDC definition was used to classify CAMRSA. Antibiotic susceptibility test was done using Kirby-Bauer disk diffusion method. Double disk diffusion method (D-test) was used to detect inducible macrolide, lincosamide and streptogramin B resistance (inducible MLS B resistance ) . A total of 83 CAMRSA were isolated from abscesses and other skin infections in persons without known risk factors for MRSA infection. All CAMRSA were susceptible to vancomycin. Out of 83 CAMRSA, 13 (15.65%) were D-test positive (inducible MLS B positive) and 6 (7.23%) were positive for constitutive MLS B resistance. Eight strains (9.63%) were resistant to tetracycline and 26 (31.32%) strains were resistant to erythromycin. Increased rate of inducible clindamycin resistance among CAMRSA indicates the importance of identification of such strains by D test to avoid treatment failure when clindamycin is used.

Clinical Application of D-test in Pseudomonas aeruginosa / 中华医院感染学杂志

OBJECTIVE To investigate the incidence rate of Pseudomonas aeruginosa whose ceftazidime resistance was induced by imipenem and the relationship of excretion pump with sensibility of imipenem and ceftazidime.METHODS The sensibility to 15 antibacterials and ceftazidime resistance induced by imipenem were detected by slip diffusion method,detect these bacteriumas′s MIC to Imipenem and Ceftazidime before and after excretion pump inhibitor hydroxide radical cyanogen chlorine phenylhydrazone(CCCP) were added by agar dilution,detect Ceftazidime′s MIC value which were added different concentration imipenem by agar dilution.RESULTS From 325 strains 116 strains(35.7%) were imipenem induced ceftazidime-resistant drug fast,from them 80.2% were imipenem-resistant and ceftazidime-sensitive,19.8% were imipenem and ceftazidime both sensitive.Sensibility to imipenem and ceftazidime was no marked change before and after CCCP added,MIC value of ceftazidime was step up 4-12 times by imipenem.CONCLUSIONS The incidence rate of ceftazidime-resistant P.aeruginosa induced by imipenem is high,clinical microbiological laboratory should evolve D-test to guide clinician use antibacterials more reasonable.

Monitoring Effect of Two Kinds of B-D Testing Package:A Comparative Study / 中华医院感染学杂志

OBJECTIVE To compare the monitoring effect of 2 kinds of B-D testing package.METHODS 2 kinds of testing package around the air vent of first pot sterilizer before antiseptic every day were used preheating 5 min.Start to move the B-D procedure when the band pressure to achieve above 100 kPa with 3 time of pulsation vacuum,inner chamber pressure of 210 kPa,the temperature of 134 ℃ and time of 3.5 min.RESULTS Except the false negative caused by package factor,the testing accurate rate of disposable B-D testing package was 100%.But the testing accurate rate of repeated uses B-D testing package was 90%.CONCLUSIONS The disposable B-D test package may respond promptly the breakdown of sterilizer and avoid the false negative result which the artificial pack factor creates.The test result is accurate.The disposable B-D testing package for examination of autoclave exhaust cold air degree is obviously better than the self-made cotton fabric testing package.

D-test for Detection of Inducible Resistance to Clindamycin in Staphylococci / 中华医院感染学杂志

OBJECTIVE To apply D-test for detection of inducible resistance of erythromycin to clindamycin in staphylococci and investigate their resistant rate to erythromycin and clindamycin. METHODS According to the standards of NCCLS to detect inducible resistance of erythromycin to clindamycin in staphylococci . RESULTS Co-resistance to erythromycin and clindamycin accounted for 50% and 22.8% in 77 strains of staphylococci (20 of S.aureus and 57 of coagulase-negative staphylococci). The rate of erythromycin resistance and clindamycin sensitivity accounted for 20% and 59.6%. D-test positive rate was 50% and 61.8% of which were erythromycin resistant and clindamycin sensitive respectively. CONCLUSIONS D-test for detection of inducible resistance of erythromycin to clindamycin in staphylococci should be checked in clinical microbiology laboratory in order to help physicians to select MLSb antimicrobial agents correctly.

Resistance of Staphylococcus and Its Mechanism / 中华医院感染学杂志

OBJECTIVE To investigate the clinical practicability of inducible clindamycin resistance and to evaluate the clinical value of cefoxitin disk diffusion method in detecting the mecA gene of meticillin-resistant Staphylococcus(MRS). METHODS Resistant phenotypes were classified with erythromycin and clindamycin discs using the D test method and the cefoxitin disk diffusion method in detecting mecA gene of the staphylococcus. RESULTS Of all 390 Staphylococcus strains,218 strains(55.9 %) were resistant to erythromycin and clindamycin(cMLS).Seventy strains(17.9 %) which were resistant to erythromycin but susceptible to clindamycin showed the positive D test results(iMLS),79 strains(20.3 %) resistant to erythromycin but susceptible to clindamycin showed the negative D test results(MS).From 390 strains of clinical isolated staphylococcus,which using the cefoxitin disk diffusion method,272 strains were MRS. CONCLUSIONS Using the D test method to investigate the inducible resistance to erythromycin and clindamycin in the Staphylococcus strains,which could help the doctors choose correctly the antibiotics such as macrolides and clindamycin.At the same time,cefoxitin disk diffusion method can be used reliably by the clinical laboratory in detecting and conforming MRS.

Failure Causes Analyses and Corrective Actions of Two Different Types of Bowie-Dick Test Pack / 中华医院感染学杂志

OBJECTIVE To analyze the monitoring performance and testing efficacy and reliability of standardized disposable B-D test pack and standard linen test pack,and summarize the corrective actions based on failure analyses for future reference.METHODS The two different test packs were employed to evaluate the vacuum performance of dynamic air removal sterilizer.RESULTS We enrolled 400 standardized disposable B-D test packs and standard linen test packs respectively.The disposable pack failed 4 cases with the success ratio 99%,while the linen pack failed 30 cases with the success ratio 92.5%.CONCLUSIONS The poor conformity of hand-made linen test pack,variation of steam pressure,sterilizer failure,and unprofessionalism of sterilizer operator contribute as main failure causes in B-D test.Standardized disposable B-D test pack can decrease subjective factors significantly,and the test results are more reliable and standardized.