ICU Pathogens: A Continuous Challenge.

OBJECTIVE: To determine the frequency and antibiogram of pathogens in an intensive care unit (ICU). STUDY DESIGN: Cross-sectional, observational study. PLACE AND DURATION OF STUDY: Department of Microbiology, Army Medical College, National University of Science and Technology, Islamabad, from January 2013 to January 2014. METHODOLOGY: Clinical samples, received from patients admitted in ICU, were inoculated on various medias like blood agar, chocolate agar, MacConkey agar and urine samples on CLED. These were then incubated at 37°C for 24 hours. Isolates were identified by colony morphology, Gram reaction, catalase test, oxidase test. Species identification in case of Gram Negative Rods was done by using API 20E (BioMérieux). Antibiotic susceptibility was done by using modified KirbyBauer disc diffusion technique. Bacterial isolates were prepared and inoculated on Mueller-Hinton agar plates followed by application of various antibiotic disc (Oxoid, UK) as per manufacturer's instructions. The plates were then incubated at 37°C aerobically for 18 - 24 hours. Zone diameters were measured and interpreted as sensitive and resistant, according to Clinical and Laboratory Standards Institute (CLSI) guidelines. RESULTS: Out of the 367 positive cultures, 116 (31.08%) were Acinetobacter baumanniisusceptible to minocycline and tigecycline followed by Klebsiella pneumoniae (n=71, 16%) susceptible to tigecycline and meropenem. Others were Pseudomonas aeruginosa, Escherichia coli,Coagulase Negative Staphylococcus, Staphylococcus aureus, Enterococcus spp., Streptococcus spp., Klebsiella oxytoca, Stenotrophomonas maltophilia,and Candida spp. CONCLUSION: Acinetobacter baumanniiwas the most frequently isolated pathogen. Most of the cultures yielding pathogens were from respiratory tract samples. Gram negative isolates were multidrug resistant but most were tigecycline and susceptible to meropenem.

Comparison of urine dipstick test with conventional urine culture in diagnosis of urinary tract infection.

OBJECTIVE: To determine the sensitivity, specificity, Positive Predictive Value (PPV) and Negative Predictive Value (NPV) of Urine Nitrite (NIT) and Leukocyte Esterase (LE) test compared with urine culture for diagnosis of UTI. STUDY DESIGN: Validation study. PLACE AND DURATION OF STUDY: Department of Microbiology, Army Medical College, Rawalpindi, from January 2013 to December 2013. METHODOLOGY: Three hundred fresh uncentrifuged urine samples with suspicion of UTI, were collected and tested for LE and NIT by using (COMBI-10SL, UK) strip. Nitrite was considered as positive if there was a change in color of dipstick from colorless towards pink within 60 seconds. Leukocyte esterase was considered as positive if there was a change in color from off-white towards purple within 2 minutes. Quantitative urine culture was performed by using the strips calibrated to deliver 0.02 ul of urine on Cystine Lactose Electrolyte Deficient (CLED) medium agar. All plates were incubated at 37°C and read after 24 and 48 hours. Culture was considered as gold standard to evaluate the performance of dipstick test. RESULTS: Out of 300 samples, 136 were culture positive and 164 were culture negative. Out of 136 positive culture results, 103 were dipstick positive and 33 were negative. Sensitivity, specificity, positive predictive value and negative predictive value of both nitrite and leukocyte esterase were 75.74%, 68.90%, 66.66% and 77.40% respectively considering culture as gold standard. CONCLUSION: Dipstick test for the detection of leukocyte esterase and nitrite in urine are sensitive and specific and can be used reliably for the detection of UTI in resource limited setup.

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 (30 µg) 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 standardized equal to 0.5 McFarland's turbidity standard 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 Standards 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.

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 µg/mL and MIC(90) was 32 µg/mL. For Acinetobacter baumannii MIC(50) and MIC(90) was 32 µg/mL. CONCLUSION: Doripenem is no more effective against Pseudomonas aeruginosa and Acinetobacter baumannii in our setting.