Comparative Efficacy of Ceftaroline with Linezolid against Staphylococcus Aureus and Methicillin Resistant Staphylococcus Aureus

Objective: To compare the in vitro antimicrobial efficacy of ceftaroline with linezolid against Staphylococcus aureus and methicillin resistant Staphylococcus aureus. Study Design: Quasi-experimental study. Place and Duration of Study: Microbiology Department, Army Medical College, Rawalpindi, from January to December 2013. Methodology: Clinical samples from respiratory tract, blood, pus and various catheter tips routinely received in the Department of Microbiology, Army Medical College, Rawalpindi were innoculated on blood and MacConkey agar. Staphylococcus aureus was identified by colony morphology, Gram reaction, catalase test and coagulase test. Methicillin resistant Staphylococcus aureus detection was done by modified Kirby Bauer disc diffusion method using cefoxitin disc [30microg] and the isolates were considered methicillin resistant if the zone of inhibition around cefoxitin disc was = 21 mm. Bacterial suspensions of 56 Staphylococcus aureus isolates and 50 MRSA isolates were prepared, which were st and ardized equal to 0.5 McFarl and 's turbidity st and ard and inoculated on Mueller-Hinton agar plates followed by application of ceftaroline and linezolid disc [Oxoid, UK], according to manufacturer's instructions. The plates were then incubated at 37°C aerobically for 18 - 24 hours. Diameters of inhibition zone were measured and interpretated as per Clinical and Laboratory St and ards Institute [CLSI] guidelines. Results: Out of 106 isolates all of the 56 Staphylococcus aureus [100%] were sensitive to ceftaroline and linezolid. However, out of 50 methicillin resistant Staphylococcus aureus, 48 [96%] were sensitive to ceftaroline whereas, 49 [98%] were sensitive to linezolid. Conclusion: Ceftaroline is equally effective as linezolid against Staphylococcus aureus and methicillin resistant Staphylococcus aureus. Key Words: Ceftaroline. Methicillin resistant Staphylococcus aureus. Linezolid.

In vitro efficacy of doripenem against Pseudomonas aeruginosa and Acinetobacter baumannii by E-Test

Objective: To assess the in vitro efficacy of doripenem against Pseudomonas aeruginosa and Acinetobacter baumannii using Epsilometer strips

Study Design: Cross-sectional study

Place and Duration of Study: Department of Microbiology, Army Medical College, Rawalpindi and National University of Sciences and Technology, Islamabad, from May 2014 to September 2014

Methodology: A total of 60 isolates of Acinetobacter baumannii and Pseudomonas aeruginosa collected from various clinical samples received from Military Hospital were included in the study. The specimens were inoculated onto blood, MacConkey and chocolate agars. The isolates were identified using Gram staining, motility, catalase test, oxidase test and API 20NE [Biomeriux, France]. Organisms identified as Acinetobacter baumannii and Pseudomonas aeruginosa were included in the study. Bacterial suspensions equivalent to 0.5 McFarland turbidity standard of the isolates were prepared and applied on Mueller Hinton agar. Epsilometer strip was placed in the center of the plate and incubated for 18-24 hours. Minimum Inhibitory Concentration [MIC] was taken to be the point where the epsilon intersected the E-strip. MIC of all the isolates was noted

Results: For Pseudomonas aeruginosa isolates, MIC[50] was 12 [micro]g/mL and MIC[90] was 32 [micro]g/mL. For Acinetobacter baumannii MIC[50] and MIC[90] was 32 [micro]g/mL

Conclusion: Doripenem is no more effective against Pseudomonas aeruginosa and Acinetobacter baumannii in our setting

Carbapenem resistant acinetobacter-A major pathogen in a Tertiary Care Hospital

Objective: To determine the frequency of carbapenem resistant Acinetobacter in the Military Hospital Rawalpindi, Pakistan

Study Design: Descriptive study

Place and Duration of Study: Department of Microbiology, Army Medical College, from Oct, 2012 to Feb, 2013

Material and Methods: Clinical specimens like naso-bronchial lavage, blood, pus, sputum and catheter tips were inoculated on blood agar and Mac Conkey agar while the urine samples were inoculated on Cystine Lactose Electrolyte Deficient [CLED] agar. Acinetobacter spp. isolated, were later subjected to antimicrobial susceptibility testing using the modified Kirby-Bauer disc diffusion method on Mueller Hinton agar as per Clinical Laboratory and Standards Institute [CLSI] guidelines

Results: Out of a total of 85 Acinetobacter spp. 62 isolates were found to be carbapenem resistant. They were also found to be 100% resistant to ciprofloxacin and ceftriaxone thus becoming multidrug resistant followed by tazobactam piperacillin [98%] and trimethoprim sulphamethoxazole [92%]. Minimum resistance was seen against tigecycline being 21%

Conclusion: It is concluded from our study that there is a high frequency [72.94%] of resistance to carbapenems in Acinetobacter spp. in our setup which is associated with increased morbidity and mortality due to limited treatment options

Coagulase negative staphylococci - a fast emerging threat

To determine the frequency of isolation of coagulase-negative staphylococci and their resistance to methicillin over a period of time. The descriptive cross-sectional study was carried out at Army Medical College, Rawalpindi, from June 2009 to May 2012, and comprised clinical samples mostly from patients admitted to the intensive care unit. They were inoculated onto appropriate culture media depending upon the specimen. After 24-hour incubation at 35°C, coagulase-negative staphylococci were identified on the basis of colony morphology, gram staining, a positive catalase and a negative tube coagulase test. Methicillin resistance among the isolated staphylococci was determined using a 30microg Cefoxitin disc as per the Clinical and Laboratory Standards Institute protocol. Number of coagulase-negative staphylococci for each year and their methicillin resistance rates were calculated. A comparison was made with methicillin resistant staphylococcus aureus] isolated during the same period. Of the total 1331 specimens studies over three years, 581[43.65%] were coagulase-negative staphylococci. The rate of coagulase-negative staphylococci and methicillin resistance was higher each year; 110[26.6%] in May 2009-Jun 2010, 134[36.5%] in 2011, and 337[61%] in 2012. Methicillin resistance rates also increased from 25[22.7%] to 46[34.3%] and then to 201[59.6%] in 2012.Maximum isolated specimens came from blood 311[53.5%], followed by pus/swabs 204[35.1%]. The frequency of isolation of coagulase-negative staphylococci and its methicillin resistance among hospitalised patients is on the rise