Oxacillin-resistant Coagulase-negative Staphylococci Research Articles

Distribution of Bacterial Species and Resistance Patterns in Surgical Site Infection after Prior Administration of Vancomycin and Tobramycin Intrawound Powdered Antibiotic Prophylaxis.

Evaluate the species distribution and resistance patterns of bacterial pathogens causing surgical site infection (SSI) after operative fracture repair, with and without the use of intrawound powdered antibiotic (IPA) prophylaxis during the index surgery. Retrospective cohort study. Academic, level 1 trauma center, 2018-2020. Fifty-nine deep SSIs were identified in a sample of 734 patients with 846 fractures (IPA [n = 320], control [n = 526]; open [n = 157], closed fractures [n = 689]) who underwent orthopaedic fracture care. Among SSIs, 28 (48%) patients received IPA prophylaxis and 25 (42%) of the fractures were open. Intrawound powdered vancomycin and tobramycin. Distribution of bacterial species and resistance patterns causing deep surgical site infections requiring operative debridement. Zero patients developed infections caused by resistant strains of streptococci, enterococci, gram-negative enterics, Pseudomonas , or Cutibacterium species. The only resistant strains isolated were methicillin resistance (19%) and oxacillin-resistant coagulase-negative staphylococci (16%). There was no associated statistical difference in the proportion of bacterial species isolated, their resistance profiles, or rate of polymicrobial infections between the IPA and control group. Most (93%) cases using IPAs included vancomycin and tobramycin powders. There were 59 SSIs; 28 (9%) in the IPA cohort and 31 (6%) in the control cohort ( P = 0.13). The use of local antibiotic prophylaxis resulted in no measurable increase in the proportion of infections caused by resistant bacterial pathogens after operative treatment of fractures. However, the small sample size and limited time frame of these preliminary data require continued investigation into their role as an adjunct to SSI prophylaxis. Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Second-Line Antibiotic Agents in Patient-Reported Penicillin or Cephalosporin Allergy Have No Negative Impact on Antibiotic Resistance After Hip and Knee Arthroplasty

BackgroundThe aim of the present study was to compare causative bacteria and their antibiotic resistance profiles in patients developing a periprosthetic joint infection (PJI) based on preoperative prophylactic antibiotic regimens in primary total hip (THA) and primary total and unicompartmental knee arthroplasty (TKA/UKA). MethodsWe reviewed all cases of PJI occurring after primary THA and primary TKA/UKA, between 2011 and 2020 in a tertiary referral hospital. The standard preoperative prophylactic antibiotic for primary joint arthroplasty was cefuroxime and recommended second-line agent was clindamycin. Patients were divided by the replaced joint and analyzed independently. ResultsIn the THA group, culture-positive PJI was detected in 61 of 3,123 (2.0%) cefuroxime-administered cases and 6 of 206 (2.9%) noncefuroxime-administered cases. In the TKA/UKA group, culture positive PJI was identified in 21 of 2,455 (0.9%) cefuroxime-administered cases and in 3 of 211 (1.4%) noncefuroxime administered cases. The most commonly isolated bacteria in both groups were coagulase negative staphylococci (CNS). There were no statistically significant differences of pathogen spectrum depending on the preoperative antibiotic regimen detected. Antibiotic resistance of isolated bacteria was significantly different in 4 of 27 (14.8%) analyzed antibiotics in THA and in 3 of 22 (13.6%) analyzed antibiotics in TKA/UKA. In all cohorts, a high occurrence of oxacillin-resistant CNS (50.0 to 100.0%) and clindamycin-resistant CNS (56.3 to 100.0%) has been observed. ConclusionThe use of the second-line antibiotic did not influence the pathogen spectrum or antibiotic resistance. However, an alarmingly high proportion of CNS strains was resistant to clindamycin.

Microbiological Trends and Antibiotic Susceptibility Patterns in Patients with Periprosthetic Joint Infection of the Hip or Knee over 6 Years.

We sought to analyze trends of the causative pathogens and their antibiotic susceptibility patterns in patients with periprosthetic joint infections (PJI) of the hip and knee to get better insights and improve treatment. Retrospective evaluation of all consecutive patients with microbiological detection of a causative pathogen at a tertiary endoprothetic referral center between January 2016 and December 2021 in Germany was performed. Overall, 612 different microorganisms could be detected in 493 patients (hip: n = 293; knee: n = 200). Evaluation did not show a change in the relative abundance of pathogens detected, with coagulase-negative staphylococci (n = 275; 44.9%) found frequently, followed by S. aureus (n = 86; 14.1%), Enterococcus species (n = 57; 9.3%), Streptococcus species (n = 48; 7.8%), and Gram-negative bacteria (n = 80; 13.1%). Evaluation of the antibiotic susceptibilities showed increasing rates of oxacillin-resistant coagulase-negative staphylococci (60.4%; 46.8–76.7%) and piperacillin-tazobactam-resistant Gram-negative bacteria (26.5%; 0–57.1%), although statistically not significant. Resistance of Gram-positive bacteria to vancomycin (<1%) and Gram-negative microorganisms to meropenem (1.25%) remained an exception. In summary, coagulase-negative staphylococci, as the most frequent pathogen, displayed a continuously high rate of oxacillin resistance. For the highest antimicrobial coverage in the case of an empiric therapy/unknown pathogen, vancomycin might be chosen. Level of evidence: IV.

1260. In Vitro Activity of Eravacycline Against Clinically Significant Bacteria Isolated from Patients with Cancer

Abstract Background Bacterial infections are common in patients with cancer (PWC). Many bacteria have developed resistance to currently used antibiotics, posing therapeutic challenges. we evaluated the in vitro activity of eravacycline (a novel fluorocycline) against clinical bacteria recently (2018-2019) isolated from PWC. Methods All 565 isolates tested were from blood cultures. CLSI approved broth microdilution method was used. Appropriate ATCC controls were included. MIC50, MIC90, MIC ranges and percent susceptibility calculations were made using FDA breakpoints when available. Eravacycline susceptibility breakpoint for most Gram-positive organisms (GPO) is ≤ 0.06 mg/L and for Enterobacterales is ≤ 0.5 mg/L. Results Eravacycline had potent activity against Staphylococcus aureus (methicillin-susceptible and resistant strains), oxacillin-susceptible coagulase-negative staphylococci (CoNS) including Staphylococcus lugdunensis, viridans group streptococci, beta-hemolytic streptococci. Streptococcus pneumoniae. Bacillus spp., Corynebacterium spp., and Micrococcus spp. It was slightly less active against oxacillin-resistant CoNS, and vancomycin-susceptible Enterococcus faecalis (MIC90 0,125 mg/L respectively) and was moderately active against vancomycin-resistant Enterococcus faecium (MIC50, 0.06, and MIC90. 0.25 mg/L). Eravacycline had potent activity against Escherichia coli (including ESBL producing strains), Citrobacter spp., and non-ESBL Klebsiella spp. Eravacycline inhibited 83% of ESBL positive K. pneumoniae, 83% of Enterobacter cloacae, and 80% of carbapenem-resistant Enterobacteriaceae (CRE) isolates at ≤ 0.5 mg/L. The presence of ESBLs increased MIC90 value no more than 2 fold. Eravacycline was also active against many non-fermentative GNB (Achromobacter spp., Acinetobacter spp., Sphingomonas paucimobilis, and Stenotrophomonas maltophilia). Table 1. Percent Susceptibility of Gram-negative isolates to Eravacycline Table 2. Percent Susceptibility of Gram-positive isolates to Eravacycline Conclusion Our data demonstrate that eravacycline has promising activity against clinically significant bacterial pathogens isolated from PWC including many drug resistant strains such as CRE and non--fermentative GNB. it might play an important role in the treatment of bacterial infections in PWC and warrants clinical evolution in this setting. Disclosures Samuel L. Aitken, PharmD, MPH, BCIDP, Melinta Therapeutoics (Individual(s) Involved: Self): Consultant, Grant/Research Support Kenneth Rolston, MD, Tetraphase Pharmaceuticals (Grant/Research Support)

Environmental survey of Methicillin-Resistant Staphylococci in a Hospital in Japan.

We examined the hospital-wide incidence of methicillin-resistant Staphylococcus contamination in a hospital environment to predict the risk of the nosocomial spread of infection. Samples were also taken different surfaces and medical equipment in a general hospital ward and a staff station. The isolates were identified bacterial strains and analyzed by PCR for detection of the mecA gene and staphylococcal cassette chromosome mec (SCCmec) types (I-V). Overall, out of 146 isolates that were screened, 15.7% of the samples in the hospital wards were contaminated with Staphylococcus aureus and 74.7% were isolated with coagulase-negative Staphylococci (CNS). The methicillin-resistant mecA gene was detected in all oxacillin-resistant S. aureus, and 89% of oxacillin-resistant CNS was identified as methicillin-resistant S. aureus (MRSA) and MRCNS respectively. All S. aureus and CNS from the hospital wards with MRSA patients were detected as MRSA and MRCNS. A widespread distribution of MRSA and MRCNS was detected in the Cuff. The majority of the MRSA and MRCNS isolates in this study were SCCmec type V, which are a community-acquired infection type. The increased incidence and prevalence of community-acquired MRSA and MRCNS, as well as hospital-acquired MRSA, should be recognized as serious healthcare problems.

Antimicrobial susceptibility of isolated pathogens from patients with contact lens-related bacterial keratitis in Crete, Greece: A ten-year analysis

PurposeTo evaluate the bacterial spectrum and antimicrobial susceptibilities of pathogens isolated from contact lens-related bacterial keratitis cases in a large academic Greek hospital. MethodsAll adult patients with positive corneal scrapings or contact lens culture between 2007 and 2016 at the University Hospital of Heraklion, Greece, were retrospectively identified through a local microbiology database and their medical records were reviewed. ResultsA total of 240 isolates were recovered from 131 patients with culture-proven contact lens-associated bacterial keratitis. The most common microorganism identified was Serratia marcescens (17.1% of total isolates), followed by Pseudomonas aeruginosa, Klebsiella spp. and coagulase-negative staphylococci (CoNS). Rates of aztreonam-resistant P. aeruginosa and erythromycin-resistant CoNS decreased in recent years, while the decrease in oxacillin-resistant CoNS was statistically significant (p=0.009). More than 90% of the isolated organisms (S. marcescens, P. aeruginosa, Klebsiella spp. and CoNS) were susceptible to ciprofloxacin or gentamicin. ConclusionGram-negative microorganisms are the most common causative pathogens of contact lens-related keratitis in the region of Crete. Topical antibacterials containing quinolones or gentamicin represent an effective empirical treatment for the majority of the cases. This is quite encouraging, considering that the present study was conducted in a country characterised by high antimicrobial resistance rates. However, culture-driven antimicrobial treatment is mandatory for this sight-threatening infection.

Infections and antimicrobial resistance in an adult intensive care unit in a Brazilian hospital and the influence of drug resistance on the thirty-day mortality among patients with bloodstream infections.

INTRODUCTION: The present study aimed to determine the incidence of health care-associated infections (HCAIs) and identify the main resistant microorganisms in intensive care unit (ICU) patients in a Brazilian university hospital. METHODS: A retrospective cohort study was conducted in a Brazilian teaching hospital between 2012 and 2014. RESULTS: Overall, 81.2% of the infections were acquired in the ICU. The most common resistant pathogenic phenotypes in all-site and bloodstream infections were oxacillin-resistant coagulase-negative staphylococci and carbapenem-resistant Acinetobacter spp. (89.9% and 87.4%; 80.6% and 70.0%), respectively. CONCLUSIONS: There is an urgent need to focus on HCAIs in ICUs in Brazil.

Methicillin-resistant coagulase-negative staphylococci in healthy dogs

The objective of this study was to evaluate the prevalence of coagulase-negative staphylococci in healthy dogs and to determine whether methicillin-resistant staphylococci expressed the mecA gene. Nasal and rectal swab samples were taken from 50 clinically healthy dogs. The prevalence of coagulase-negative staphylococci was evaluated according to phenotypic properties. The agar diffusion method was applied to evaluate antimicrobial resistance and the prevalence of methicillin resistance was determined using PCR analysing the mecA gene. A total of 59 coagulase-negative staphylococcus strains were isolated from the nostrils and rectums of 37 (74%) clinically healthy dogs. The prevalence of coagulase-negative staphylococci in female dogs was significantly higher compared with male dogs (P &amp;lt; 0.05). The results of antimicrobial susceptibility testing showed that 6.7% of the strains were resistant to oxacillin, 23.7% were resistant to penicillin, 22% to ampicillin and 16.9% to erythromycin. The mecA PCR revealed one oxacillin-sensitive and four oxacillin-resistant coagulase-negative staphylococci strains to be mecA carriers. Staphylococcus sciuri (60%) and Staphylococcus warneri (20%) were the most prevalent species among methicillin-resistant coagulase negative staphylococci. High antimicrobial resistance rates for these bacteria were observed against penicillin (100%), ampicillin (100%), oxacillin (80%), erythromycin (80%) and gentamicin (60%). All strains were susceptible to vancomycin and enrofloxacin. It is assumed that methicillin-resistance genes evolved in coagulase-negative staphylococcus and were then horizontally transferred among staphylococci.

Vancomycin heteroresistance in coagulase negative Staphylococcus blood stream infections from patients of intensive care units in Mansoura University Hospitals, Egypt

BackgroundVancomycin heteroresistance in coagulase negative Staphylococci (CoNS) is a recent health concern especially in serious infections like bloodstream infections as it may lead to failure of therapy. Little information is available about the prevalence vancomycin heteroresistance in CoNS causing bloodstream infections in intensive care units (ICUs) patients of Mansoura University Hospitals (MUHs).MethodsThis prospective study enrolled 743 blood samples collected from ICUs patients presented with clinical manifestations of bloodstream infections over the period extending from January 2014 to March 2016. Samples were processed, coagulase negative Staphylococci were identified by routine microbiological methods and the absence of coagulase activity. Species were identified by API Staph 32. Oxacillin resistant CoNS were identified by cefoxitin disc diffusion method. Susceptibility testing of isolated CoNS to vancomycin was carried out using vancomycin agar dilution method. Mec A gene detection by PCR was done for oxacillin resistant isolates. Screening for vancomycin heteroresistance was done on brain heart infusion (BHI) agar containing 4 μg/mL vancomycin. Confirmation of vancomycin heteroresistance was carried out by population analysis profile (PAP).ResultsA total of 58 isolates were identified as CoNS from patients of clinically suspected bloodstream infections. The identified species were 33 (56.9%) Staphylococcus epidermidis, 12 (20.7%) Staphylococcus capitis, 7 (12.1%) Staphylococcus haemolyticus, and 3 isolates (5.2%) Staphylococcus lugdunesis. Three isolates were unidentified by API Staph 32. Forty-four (75.9%) isolates were oxacillin resistant. Mec A gene was detected in all oxacillin resistant isolates. All isolates had susceptible vancomycin MICs by agar dilution. Nine isolates (15.5%) could grow on BHI agar containing 4 μg/mL vancomycin. These isolates showed heterogeneous profile of resistance to vancomycin by population analysis profile.ConclusionsVancomycin heteroresistant CoNS causing bloodstream infections is growing unrecognized health hazard in ICUs patients. These isolates have susceptible vancomycin MICs. Screening methods are recommended and should be considered to improve clinical outcome in these high risk patients.

Antimicrobial resistance of bacteria isolated from patients with bloodstream infections at a tertiary care hospital in the Democratic Republic of the Congo

Bloodstream infection (BSI) is a life-threatening condition that requires rapid antimicrobial treatment. We determined the prevalence of bacterial isolates associated with BSI at Bukavu General Hospital (BGH), South Kivu Province, Democratic Republic of the Congo, and their patterns of susceptibility to antimicrobial drugs, from February 2013 to January 2014. We cultured 112 clinically relevant isolates from 320 blood cultures. Of these isolates, 104 (92.9%) were Gram-negative bacteria (GNB), with 103 bacilli (92.0%) and one coccus (0.9%). Among GNB, Escherichia coli (51.9%), Klebsiella spp. (20.2%), Enterobacter spp. (6.7%), Shigella spp. (5.8%) and Salmonella spp. (4.8%) were the most frequent agents causing BSIs. Other GNB isolates included Proteus spp., Citrobacter spp. and Pseudomonas aeruginosa (both 2.9%), and Acinetobacter spp. and Neisseria spp. (both 0.9%). High rates of resistance to co-trimoxazole (100%), erythromycin (100%) and ampicillin (66.7-100%) and moderate to high resistance to ciprofloxacin, ceftazidime, ceftriaxone, cefuroxime and cefepime were observed among GNB. Furthermore, there were high rates of multidrug resistance and of extended-spectrum β-lactamase (ESBL) production phenotype among Enterobacteriaceae. Gram-positive bacteria included three Staphylococcus aureus isolates (2.7%), four oxacillin-resistant coagulase-negative staphylococci (CoNS) isolates (3.6%) and one Streptococcus pneumoniae (0.9%). No oxacillin-resistant S. aureus was isolated. Among clinically relevant staphylococci, susceptibility to co-trimoxazole and ampicillin was low (0-25%). In addition, 58 contaminant CoNS were isolated from blood cultures, and the calculated ratio of contaminants to pathogens in blood cultures was 1:2. Multidrug-resistant and ESBL-producing GNB are the leading cause of BSI at BGH.

Epidemiology of bacteraemia in Hamad general hospital, Qatar: A one year hospital-based study

Background: Bacteraemia is one of the most common clinical problems confronting physicians worldwide. Data on the epidemiology of bacteraemia in the State of Qatar are still incomplete. Methods: We conducted a one-year prospective study from July 2007 to June 2008 to describe the epidemiology of bacteraemia at Hamad general hospital. Results: During this period, a total of 452 episodes of bacteraemia occurred, which corresponds to a rate of 19/1000 hospital admissions. Most patients 58.8% (266/452) had community acquired bacteraemia, and primary bacteraemia accounted for 62.2% (281/452) of the cases. The most common source of bacteraemia was intravenous catheterization in 19.2% (87/452) but no source was identified in 42.9% (194/452) of the episodes. Gram-negative organisms were isolated in 63.1% (285/452) episodes with Escherichia coli being the most frequent 21.5% (97/452). Multidrug resistance was observed in 33.3% (7/21) of all Pseudomonas aeruginosa isolates, 50% (6/12) of Acinetobacter isolates and 28.6% (6/21) of Enterobacter isolates, whereas all ESBL producing Klebsiella spp. and E. coli were multiresistant. The percentages of oxacillin resistant coagulase negative Staphylococci isolates and methicillin-resistant Staphylococcus aureus isolates were 81.8% (27/33) and 13.2% (7/53) respectively. In hospital mortality was 22.5% (102/452), and inadequate treatment and septic shock were found to be independent predictors of mortality. Conclusion: To reduce the occurence of bacteremia, and cosequently, to minimise the mortality and adverse outcomes, strict infection control measures as well as rational use of antibiotics are to be followed to prevent infections and to reduce drug resistance. Moreover, bloodstream infection surveillance is crucial to produce meaningful guidelines for prevention (e.g., catheter-related) and empirical treatment of bacteraemia in Qatar.

Bacteremias por Staphylococcus coagulase negativos oxacilina resistentes em um hospital escola na cidade de Santa Maria, Estado do Rio Grande do Sul

This study aimed to characterize the prevalence and susceptibility profile to oxacillin-resistant Coagulase-negative Staphylococci strains isolated from blood cultures in a teaching hospital, located in Santa Maria, RS. In addition, different methodologies for phenotypic characterization of mecA-mediated oxacillin resistance were compared with genotypic reference testing. After identification (MicroScan - Siemens), the isolates were tested for antimicrobial sensitivity using disk diffusion and automation (MicroScan - Siemens). The presence of mecA gene was identified by the polymerase chain reaction molecular technique. The most common species was Staphylococcus epidermidis (n=40, 67%). The mecA gene was detected in 54 (90%) strains, while analysis of the sensitivity profiles revealed a high rate of resistance to multiple classes of antimicrobial drugs. However, all isolates were uniformly sensitive to vancomycin and tigecycline. The cefoxitin disk was the phenotypic method that best correlated with the gold standard. Analysis of the clinical significance of CoNS isolated from hemocultures and the precise detection of oxacillin resistance represent decisive factors for the correct choice of antibiotic therapy. Although vancomycin constitutes the normal treatment in most Brazilian hospitals, reduction in its use is recommended.

Epidemiology of bacteraemia in Hamad general hospital, Qatar: A one year hospital-based study

We conducted a one-year observational study from July 2007 to June 2008 to describe the epidemiology of bacteraemia at Hamad general hospital. During this period, a total of 452 episodes of bacteraemia occurred, which corresponds to a rate of 19/1000 hospital admissions. Most patients 58.8% (266/452) had community acquired bacteraemia, and primary bacteraemia accounted for 62.2% (281/452) of the cases. The most common source of bacteraemia was intravenous catheterization in 19.2% (87/452) but no source was identified in 42.9% (194/452) of the episodes. Gram-negative organisms were isolated in 63.1% (285/452) episodes with Escherichia coli being the most frequent 21.5% (97/452). Multidrug resistance was observed in 33.3% (7/21) of all Pseudomonas aeruginosa isolates, 50% (6/12) of Acinetobacter isolates and 28.6% (6/21) of Enterobacter isolates, whereas all ESBL producing Klebsiella spp. and E. coli were multiresistant. The percentages of oxacillin resistant coagulase negative Staphylococci isolates and methicillin-resistant Staphylococcus aureus isolates were 81.8% (27/33) and 13.2% (7/53) respectively. In hospital mortality was 22.5% (102/452), and inadequate treatment and septic shock were found to be independent predictors of mortality. Therefore, bloodstream infection surveillance is crucial to produce meaningful guidelines for prevention (e.g., catheter-related) and empirical treatment of bacteraemia in Qatar.

Long-term epidemiology of bacterial susceptibility profiles in adults suffering from febrile neutropenia with hematologic malignancy after antibiotic change

The aim of this study was to investigate the epidemiology and antibiotic susceptibility profiles of isolated bacterial organisms in relation to empiric treatment of neutropenic fever over a 15-year period. All patients with or at risk for febrile neutropenia and treated in the hematology ward of the Antwerp University Hospital during 1994-2008 were prospectively included. Skin, blood, and urine cultures were taken. Oral quinolone prophylaxis was started in patients with neutropenia without fever. Empiric starting therapy consisted of amikacin in combination with cefepime. A total of 3624 bacteria were isolated. The most common pathogens were coagulase-negative Staphylococci (46%), followed by Escherichia coli (25%), Enterobacteriaceae (15.6%), Staphylococcus aureus (7.2%), and Pseudomonas aeruginosa (3.8%). The balance between Gram-positive and Gram-negative bacteria remained stable, with a majority of Gram-positive bacteria. A shift from oxacillin-sensitive to oxacillin-resistant coagulase-negative Staphylococci was observed. Regarding susceptibility patterns, no vancomycin resistance was detected in coagulase-negative Staphylococci or in S. aureus. The E. coli susceptibility rates remained stable. However, 66% of bloodstream infections were ciprofloxacin-resistant. A reduced susceptibility of P. aeruginosa strains to meropenem was noticed. Improvement in antibiotic susceptibility of inducible Enterobacteriaceae following a switch of empiric antibiotic therapy was maintained 15 years after starting the latter treatment. Further improvement in antibiotic susceptibility of these bacteria to ceftazidime was observed, but continuous vigilance is warranted.

Evaluation of the accuracy of various phenotypic tests to detect oxacillin resistance in coagulase-negative staphylococci

In this study, we determined the accuracy of phenotypic tests (cefoxitin agar dilution, 30 microg-cefoxitin and 1 microg-oxacillin disks) to detect the oxacillin resistance/mecA gene among coagulase-negative staphylococci (CoNS) isolates. The presence of the mecA gene was detected by PCR technique (gold standard). A total of 176 CoNS isolates from blood of hospitalized patients were evaluated. Of these, 138 (78.4%) harbored the mecA gene. Using 30 microg-cefoxitin and 1 microg-oxacillin disks we obtained 100 and 98.3% accuracy, respectively. In addition, when cefoxitin was used as marker in an agar dilution method, the higher accuracy (99.4%) was established with 8 mg cefoxitin per mL breakpoint. Thus, despite of the agar dilution method using cefoxitin as a marker not being standard for this detection, our results suggested that it is an excellent alternative to detect the oxacillin resistance/mecA gene among CoNS isolates.

Evaluation of latex agglutination test and oxacillin resistant screening agar base (ORSAB) medium for the detection of oxacillin resistant coagulase negative Staphylococci (ORCoNS) (Preliminary study)

Coagulase negative Staphylococci (CoNS) are recognized as an important cause of nosocomial infection, especially in neonates and patients with indwelling prosthetic devices. The CoNS resistance rate to oxacillin has been increasing. Therefore, rapid and accurate detection of oxacillin resistance is essential in order to determine the most appropriate antimicrobial therapy. This study aimed to prove that latex agglutination test and oxacillin resistant screening agar base (ORSAB) medium can be used for rapid detection of oxacilllin resistant CoNS (ORCoNS). Latex agglutination test and ORSAB medium compared with the conventional method was conducted in this study toward 30 clinical isolates of CoNS for the detection of ORCoNS. Mc Nemar test was used to analyze the data. The study result revealed that there was no significant difference (P&gt;0.05) in terms of ORCoNS detection between the latex agglutination test and ORSAB medium on the one hand, and the conventional method on the other. It is concluded that latex agglutination test and ORSAB medium can be used for rapid detection of ORCoNS. (Med J Indones 2007; 16:228-32)

Slime production and antibiotic susceptibility in staphylococci isolated from clinical samples

A total of 187 isolates from several clinical specimens were identified to species level as 129 Staphylococcus aureus strains and 58 coagulase-negative staphylococci (CNS) strains by the API Staph System (Biomerieux). Slime production was detected both by the conventional Christensen's method as well as by the Congo red agar method. Seventy-two strains of staphylococci isolates (38.5%) were found to be slime producers by Christensen's test tube method whereas 58 strains (31%) were slime positive with Congo red agar method. There was no statistically significant difference between the two methods for the detection of slime production (P > 0.05). Susceptibility of isolates against antimicrobial agents was tested by the disk diffusion method. Staphylococcal species had resistance to one or more antibiotics. Among the various antimicrobial agents, oxacillin (71.1%) and erythromycin (47.1%) showed higher resistance than most of the agents used against all isolates. Oxacillin resistant S. aureus (ORSA) and oxacillin resistant coagulase-negative staphylococci (ORCNS), 97 (75.2%) and 36 (62.1%) respectively were frequently observed in strains isolated from clinical materials. Among the ORSA strains, two strains were resistant to vancomycin. Moreover, 96 (74.4%) of 129 S. aureus strains were positive for beta-lactamase enzyme. However, 78 (81.25%) of 96 beta-lactamase positive S. aureus strains were beta-lactamase positive ORSA isolates, but none of them had vancomycin resistance.

Evaluation of methods for detecting oxacillin resistance in coagulase-negative staphylococci including cefoxitin disc diffusion

The aim of this study was to evaluate the accuracy of cefoxitin disc diffusion as a prediction of oxacillin resistance in coagulase-negative staphylococci (CoNS), and also to compare genotypic and phenotypic methods for detecting this resistance property. A total of 151 clinical CoNS isolates were tested by PCR for the presence of the mecA gene (gold standard method). The isolate susceptibilities were determined by the disc diffusion method with oxacillin (1 microg) and cefoxitin (30 microg) and by the agar dilution method for cefoxitin and oxacillin. Although none of the techniques showed 100% sensitivity and 100% specificity, the cefoxitin disc diffusion and oxacillin agar dilution were the best methods for detecting resistance to oxacillin among CoNS as these methods produced the best negative and positive predictive values. A combination of methods can be used routinely to identify resistance to oxacillin in CoNS.

Routine antimicrobial susceptibility testing of coagulase-negative staphylococci isolated from blood cultures: is it necessary?

The clinical significance of discontinuing routine antibiotic susceptibility testing (AST) of coagulase-negative Staphylococcus (CNS) isolates from blood cultures was investigated. Prospectively, AST was requested primarily for patients with serious underlying illnesses. Antibiotic use did not change significantly when AST was not performed routinely. Laboratory cost savings were 75% if AST was not performed, but more specimens were submitted from these patients. Oxacillin resistance in coagulase-negative staphylococci from blood cultures has remained > 70% since implementation of this protocol, while annual vancomycin utilisation has shown only small, incremental increases. Therefore, it is suggested that routine AST of CNS isolates from blood culture is not essential.

Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus in Zürich, Switzerland (2003): Prevalence of Type IV SCC mec and a New SCC mec Element Associated with Isolates from Intravenous Drug Users

The majority of methicillin-resistant Staphylococcus aureus (MRSA) isolates, recovered in 2003 at the Department of Medical Microbiology in Zürich, Switzerland, belonged to major clones that are circulating worldwide. Staphylococcal cassette chromosome mec type IV (SCCmec-IV), harbored by half of the isolates, was found in sequence type 217 (ST 217), which is an allelic variant of epidemic MRSA-15 (designated EMRSA-15), in a new local ST 617 descending from clonal complex CC 8 and in low-level oxacillin-resistant strains of multiple genetic lineages characteristic of community-onset MRSA. SCCmec-I, SCCmec-II, and SCCmec-III were in the minority, and four MRSA isolates had complex, rearranged SCCmec elements. A novel SCCmec-N1 of approximately 30 kb, associated with a dfrA gene and a ccr 4-related recombinase complex, was identified in a large number of low-level oxacillin-resistant isolates, which descended from the successful clonal complex CC 45 and are spreading among intraveneous drug users. In contrast, the SCCmec types of oxacillin-resistant coagulase-negative staphylococci (MRCNS) were of completely different composition. SCCmec type I (SCCmec-I) and SCCmec-II were more frequent than in the MRSA, while fewer contained SCCmec-IV. The other MRCNS displayed 11 different, complex patterns, suggesting frequent recombination between different SCCmec elements. With one ccr-negative exception, these strains amplified between one and three different ccr products, indicating either new varied complexes or multiple ccr loci. This suggests the presence of novel SCCmec types in MRCNS and no extensive interspecies SCCmec transfer between MRSA and MRCNS.