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Biomedical subjects

Rifat Nadeem Ahmad

Publications and source records attributed to Rifat Nadeem Ahmad.

10 recordsLinked to original sources
PubMed2006

Validity of nalidixic acid screening in fluoroquinolone-resistant typhoid salmonellae.

OBJECTIVE: To validate the screening of low-level fluoroquinolone resistance in typhoid salmonellae by using nalidixic acid (30 mg) disk providing an acceptable zone of inhibition. DESIGN: Quasi-experimental study. PLACE AND DURATION OF STUDY: The Department of Microbiology, Armed Forces Institute of Pathology, Rawalpindi, Pakistan from July 2002 to June 2003. MATERIALS AND METHODS: Antimicrobial susceptibility of 225 clinical isolates of S. typhi (n=126) and S. paratyphi A (n=99) against nalidixic acid and ciprofloxacin was determined by the modified Kirby-Bauer disk diffusion and agar dilution techniques of NCCLS. The relationship between the zone sizes and the MICs of the two quinolones was plotted in the form of scattergrams and nalidixic acid MICs and zone of inhibition sizes were correlated with those of ciprofloxacin by regression analysis. RESULTS: One hundred and ninety-five isolates were nalidixic acid-susceptible (MIC <16 microg/mL) and approximately 30 were nalidixic acid-resistant (MIC >32 microg/mL). All the nalidixic acid-susceptible isolates had ciprofloxacin MIC of <0.064 microg/mL. Among the nalidixic acid-resistant isolates approximately 20 had ciprofloxacin MIC > or =0.125 microg/mL and approximately 10 had ciprofloxacin MIC < or =0.03-0.064 microg/mL. The diameter of inhibition zone around a 30 mg nalidixic acid disk of nalidixic acid-resistant isolates was < or =13 mm (range 6-16 mm, mean 10.3 mm + SD 3.5 mm), while among nalidixic acid-susceptible isolates it ranged from 14 to 30 mm (mean 23.8 mm + SD 2.2 mm). The diameter of inhibition zone around a 5mg ciprofloxacin disk of nalidixic acid-resistant isolates ranged from 26 to 35 mm (mean 29.8 mm + SD 3.1 mm), while in nalidixic acid-susceptible isolates it ranged from 32 to 42 mm (mean 36.6 mm + SD 1.9 mm). With ciprofloxacin MIC > or =0.125 microg/mL taken as a breakpoint, a zone of <or =33 mm around a 5 microg ciprofloxacin disk to detect low susceptibility strains had a sensitivity of 100% and a specificity of 82%. Screening for nalidixic acid resistance (inhibition zone diameter of < or =13 mm) in isolates with ciprofloxacin MIC 0.125 microg/mL using a 30 microg nalidixic acid disk yielded a sensitivity of 100% and a specificity of 95%. CONCLUSION: Screening for nalidixic acid resistance with a 30 microg nalidixic acid disk is a reliable and cost-effective method for detection of low-level fluoroquinolone resistance in typhoid salmonellae.

Anti-Infective Agents↗
PubMed2005

Emergence of metallo-beta-lactamase producing Pseudomonas aeruginosa in Pakistan.

We report a case of urinary tract infection due to metallo-beta-lactamase producing Pseudomonas aeruginosa resistant to carbapenems. This report signals an ominous development. Unless curbed by judicious use of antibiotics and early detection by screening tests, spread of this plasmid-mediated resistance can render the carbapenems ineffective.

Carbapenems↗
PubMed2004

Genus and species-specific IgG and IgM antibodies for pulmonary tuberculosis.

OBJECTIVE: To evaluate three different enzyme immunoassays for serological diagnosis of pulmonary tuberculosis and to compare their diagnostic accuracy in different combinations. DESIGN: A non-interventional comparative study. PLACE AND DURATION OF STUDY: The study was carried out at the Department of Microbiology, Armed Forces Institute of Pathology, Rawalpindi between April and September 2001. SUBJECTS AND METHODS: Sera from patients suffering from pulmonary tuberculosis (n=94) with sputum positive for acid fast bacilli (AFB) and sera from control group of healthy individuals (n=90) with sputum negative for AFB were tested by Pathozyme-Myco G EIA, Pathozyme-TB Complex Plus EIA and Pathozyme Myco M EIA kits for the genus-specific IgG and IgM, and the species-specific IgG antibodies against antigens of Mycobacterium tuberculosis. RESULTS: The detection of IgG against genus-specific antigens by Pathozyme-Myco G had a sensitivity of 46% and a specificity of 93%, of IgG against species-specific antigens by Pathozyme-TB Complex Plus had a sensitivity of 64% and specificity of 97% and of IgM against genus-specific antigens by Pathozyme Myco M had a sensitivity of 67% and specificity of 98%. When the results of these immunoassays were evaluated in combination, their sensitivity improved. Combination of genus-specific IgM and species-specific IgG yielded best results with a sensitivity of 87% and specificity of 93%. CONCLUSION: The sensitivity of serological diagnosis of tuberculosis is low, but it can be increased by utilizing a combination of several antigens.

Antibodies, Bacterial↗
PubMed2004

Central venous catheter-related bloodstream infections in cancer patients.

OBJECTIVE: To determine the frequency of central venous catheter-related bloodstream infections (CR-BSI) in cancer patients and the antimicrobial susceptibility pattern of the isolates. DESIGN: A cross-sectional study. PLACE AND DURATION OF STUDY: The study was conducted between April 2002 and March 2003 at the Armed Forces Institute of Pathology, Rawalpindi in collaboration with Oncology Units of Armed Forces Bone Marrow Transplant Centre and Combined Military Hospital, Rawalpindi. SUBJECTS AND METHODS: Cancer patients requiring short or long-term central venous catheterization at the time of admission or thereafter were included. Catheter tips on removal were cultured quantitatively; specimens of blood and pus were cultured qualitatively. Isolates were identified and antimicrobial susceptibility testing was performed by standard techniques. RESULTS: Eighty-nine patients were included in the study. The frequency of CR-BSI was 17%. Out of the 19 organisms isolated, 10 (53%) were Gram-positive cocci, 8 (42%) were Gram-negative rods and 1 (5%) was a fungus. Coagulase negative staphylococci (27%) were the predominant pathogens. Among the staphylococci, 46% of the isolates were methicillin-resistant. All Gram-positive isolates were susceptible to glycopeptides. Gram-negative rods were resistant to most of the commonly used antimicrobial groups. CONCLUSION: Central venous catheter is an important source of bloodstream infections in cancer patients. Most of the infections are caused by Gram-positive cocci. Rigorous infection control measures and continuous surveillance are required to curb the frequency of these infections.

Adolescent↗
PubMed2003

Ciprofloxacin treatment failure in typhoid fever case, Pakistan.

We report a case of ciprofloxacin treatment failure in a typhoid fever patient at a tertiary care hospital in Rawalpindi, Pakistan. This case shows not only the emergence of fluoroquinolone resistance in typhoid salmonellae but also the inadequacy of the current laboratory guidelines for detection of this resistance.

Adolescent↗
PubMed2003

An update on the diagnosis of tuberculosis.

Tuberculosis (TB) continues to be the bane of mankind. Early diagnosis is the cornerstone of tuberculosis control strategies. Recent years have seen major advances in the fields of biotechnology and molecular biology with introduction of several new diagnostic techniques for tuberculosis and improvement in the existing ones. The new automated culture techniques have appreciably reduced the time required for detection and antimicrobial susceptibility testing. The molecular amplification techniques like the Polymerase Chain Reaction (PCR) have made the same-day diagnosis a reality. Improvements in serology and introduction of novel new techniques like the bacteriophage assays have also shown a lot of promise. However, most of these new techniques are too expensive and sophisticated to be of any practical benefit to the vast majority of TB patients living in underdeveloped countries like Pakistan for whom an early and inexpensive diagnosis remains as elusive as ever. In this article various existing modalities as well as the new advances in TB diagnostics are reviewed.

Clinical Laboratory Techniques↗
PubMedDate not supplied

Bloodstream infections in febrile neutropenic patients: bacterial spectrum and antimicrobial susceptibility pattern.

BACKGROUND: Bacterial infections are the major cause of morbidity and mortality among neutropenic patients. Prompt administration of empiric antimicrobial therapy for febrile neutropenic patients is considered vital. Before putting neutropenic patients on empiric antimicrobial regimens, it is essential to be aware of the spectrum of locally prevalent pathogens and their susceptibility pattern. METHODS: We studied the bacterial spectrum and antimicrobial susceptibility pattern of organisms causing bloodstream infections in febrile neutropenic patients in Armed Forces Bone Marrow Transplant Centre, Rawalpindi and the Department of Oncology, Combined Military Hospital, Rawalpindi over a period of nine months from January to September 2002. RESULTS: Blood specimens for culture and susceptibility testing were collected from 158 febrile patients with neutropenia. Eighty-three organisms were isolated from 60 patients. Thirty-six (43%) isolates were Gram-positive cocci and forty-seven (57%) were Gram-negative rods. Among the Gram-positive cocci, coagulase negative staphylococci (CoNS) were the predominant pathogens (26%), followed by Staphylococcus aureus (8%). Among Gram-negative rods, Escherichia coli was the predominant isolate (13%) followed by Klebsiella pneumoniae (10%). Acinetobacter johnsonii (10%) and Pseudomonas aeruginosa (7%). Nine specimens yielded polymicrobial growth. Forty percent of Staphylococcus aureus and 55% of CoNS were resistant to methicillin. All the Gram-positive isolates were susceptible to vancomycin and teicoplanin. Among the Gram-negative rods, there was 100% resistance to ampicillin, 65% to gentamicin, 47% to amikacin and 66% to third generation cephalosporins. All the gram-negative isolates were susceptible to imipenem. CONCLUSION: The spectrum of isolates among febrile neutropenic patients in our population appears to be shifting towards Gram-positive microorganisms. Due to increasing levels of drug resistance among the isolates, a glycopeptide in combination with a carbapenem would be a prudent choice as empiric therapy in high-risk cases.

Adult↗