Gram-negative Bacillary Isolates Research Articles

Bacterial isolates in traumatic globe ruptured patients in a peripheral tertiary medical college and hospital

Background: Ocular trauma can lead to access of bacteria to the intra ocular contents. So the information of the bacterial contaminants is crucial to institute empirical antibiotic therapy to prevent the development of endophthalmitis. Aims & Objectives: To isolate the bacterial contamination following traumatic globe ruptured patients in a peripheral tertiary medical college and hospital. Materials and Methods: This prospective study was conducted in the department of Ophthalmology, Burdwan Medical College, over a period of one year from April 2013- March 2014. A detailed history was taken and ophthalmological workup was done for each open globe injury cases. At the time of repair, we took three samples for bacteriological culture. Those samples were collected as conjunctival swab from inferior fornix, aqueous sample, and vitreous tap respectively. The collected samples were labeled properly and immediately sent to the department of microbiology for bacteriological culture and sensitivity. The culture report was studied and recorded. Results: The study included 75 cases, of which, 57were males, and 18 were females. Age of the study population was ranging from 18 – 54 years. Fifty seven (77.33%) study population belonged to rural areas, and eighteen (24%) were of urban area. Most common etiologic agent responsible for traumatic rupture of globe was stone chip followed by road traffic accident. Bacteria were isolated from 50 (66.66%) of the 75 eyes studied. Of these 50 eyes, a single isolate was detected in 39 (78%) eyes, while there were two isolates in 7 (14%) eyes, three and or more isolates in 4 (8%) eyes. In more detail, there were 33 strains of Gram-positive cocci, accounting for 66.0% of all isolates, of which most common was staphylococcus epidermidis (46%). Among 8 Gram-positive bacilli isolates (16%), all were of the genus Corynebacterium. There were 9 (18%) Gram-negative bacillary isolates, including 3 (6%) Escherichia coli; 2 (4%) isolates of Pseudomonas aeruginosa, and one isolate (2%) each of Proteus vulgaris, Enterobacter aerogenes, Klebsiella, and Haemophilus influenzae. Conclusion: Isolation of bacteria from eyes with open globe injuries, and their subsequent antibiotic sensitivity pattern, provides an insight into selection of appropriate prophylactic drugs for prevention of development of endophthalmitis.

Rapid and Simultaneous Detection of Genes Encoding Klebsiella pneumoniae Carbapenemase ( bla KPC ) and New Delhi Metallo-β-Lactamase ( bla NDM ) in Gram-Negative Bacilli

We present a duplex, real-time PCR assay for detection of Klebsiella pneumoniae carbapenemase (blaKPC) and New Delhi metallo-β-lactamase (blaNDM) genes. Accuracy was assessed with 158 Gram-negative bacillary isolates, including 134 carbapenemase producers. The assay had 100% sensitivity and specificity compared with reference methods and a turnaround time of 90 min.

Conjunctival sac bacterial flora isolated prior to cataract surgery

ObjectiveTo determine the trends of conjunctival sac bacterial flora isolated from patients prior to cataract surgery.Subjects and methodsThe study comprised 579 patients (579 eyes) who underwent cataract surgery. Specimens were collected by lightly rubbing the inferior palpebral conjunctival sac with a sterile cotton swab 2 weeks before surgery, and then cultured for isolation of bacteria and antimicrobial sensitivity testing. The bacterial isolates and percentage of drug-resistant isolates were compared among age groups and according to whether or not patients had diabetes mellitus, hyperlipidemia, dialysis therapy, oral steroid use, dry eye syndrome, or allergic conjunctivitis.ResultsThe bacterial isolation rate was 39.2%. There were 191 strains of Gram-positive cocci, accounting for the majority of all isolates (67.0%), among which methicillin-sensitive coagulase-negative staphylococci was the most frequent (127 strains, 44.5%), followed by methicillin-resistant coagulase-negative staphylococci (37 strains, 12.7%). All 76 Gram-positive bacillary isolates (26.7%) were from the genus Corynebacterium. Among the 16 Gram-negative bacillary isolates (5.9%), the most frequent was Escherichia coli (1.0%). The bacterial isolation rate was higher in patients >60 years old, and was lower in patients with dry eye syndrome, patients under topical treatment for other ocular disorders, and patients with hyperlipidemia. There was no significant difference in bacterial isolation rate with respect to the presence/absence of diabetes mellitus, steroid therapy, dialysis, or a history of allergic conjunctivitis. Methicillin-resistant coagulase-negative staphylococci showed a significantly higher detection rate in diabetic patients than nondiabetic patients (20.3% versus 7.0%, P < 0.05). The percentage of all isolates resistant to levofloxacin, cefmenoxime, and tobramycin was 14.0%, 15.2%, and 17.9%, respectively, with no significant differences among these drugs.ConclusionThe high bacterial isolation rate in patients >60 years old and the high methicillin-resistant coagulase-negative staphylococci isolation rate in patients with diabetes are important to consider for prevention of perioperative infections.

A Flavobacterium meningosepticum outbreak among intensive care patients

A Flavobacterium meningosepticum outbreak, involving 12 infected and 47 colonized intensive care patients during the months of February through July 1990, was investigated. F. meningosepticum was isolated from tap water and ice, but these environmental strains eventually proved to be distinct from those colonizing patients. A review of newly colonized patients' charts revealed that a common factor among the patients was daily changes of ventilator tubing pasteurized in the hospital's central sterile department. More than 90% of patients in the outbreak had been on ventilators that used the pasteurized tubing. An investigation of the pasteurization process found that two pasteurizer tanks had been operating at suboptimal temperatures (< 62° C). Cultures of water from the tanks and droplets of water found in the pasteurized tubing grew species of Acinetobacter, Moraxella, and Pseudomonas but did not grow F. meningosepticum. After deficiencies in the pasteurization process were corrected, the outbreak terminated. Despite the failure to culture F. meningosepticum, an analysis of gram-negative bacillary isolates showed that the deficiency in the pasteurization process was a major contributor to colonization of ventilated patients by bacteria ubiquitous in tap water.

Aminoglycoside resistance and aminoglycoside usage: ten years of experience in one hospital

For 10 years the 700-bed Minneapolis Veterans Affairs Medical Center has conducted a policy of carefully controlled aminoglycoside usage and monitoring of resistance of over 25,000 aerobic and facultative gram-negative bacillary isolates to the aminoglycosides. On two occasions during the 1980s, our experience of introducing amikacin at a high level of usage was associated with a significant reduction in resistance to gentamicin and tobramycin among gram-negative bacilli. Rapid reintroduction of gentamicin usage in 1982 after the first amikacin period was associated with a significant and rapid increase in gentamicin and tobramycin resistance. However, in 1986, gentamicin was again reintroduced to this institution at an initially modest level, and the percentage of usage of gentamicin was gradually increased over a 15-month period without a significant change in resistance to gentamicin, tobramycin, or amikacin while maintaining an overall 68% gentamicin usage and 30% amikacin usage. Aminoglycoside usage (measured as patient days) rose steadily from under 2,000 patient days per quarter in 1980 and 1981 to over 3,000 days per quarter in 1985. Since 1985, usage has declined to under 2,500 patient days per quarter in 1990. This usage rise and fall occurred during a steadily declining daily patient census that was 590 in 1980 and 465 in 1989. A move to a new hospital building in June 1988 was associated with an additional significant decline in resistance to all aminoglycosides (P less than 0.05), continuing a trend that was evident for the year preceding the move. Resistance to aminoglycoside antibiotics is now at the lowest level in 10 years at this institution, with only one gram-negative organism, Pseudomonas aeruginosa, that exhibits more than 5% resistance to gentamicin and no gram-negative species that are more than 5% resistant to amikacin and tobramycin.

Reassessment of susceptibility test interpretive criteria for ticarcillin and ticarcillin-clavulanic acid.

There are at least four different existing or proposed interpretive criteria for the disk diffusion susceptibility testing of ticarcillin and ticarcillin plus clavulanic acid (T/C). To assess these criteria, 570 gram-negative bacillary isolates were tested for susceptibility to ticarcillin and T/C by both disk diffusion and broth microdilution methods. These included 53 strains of the family Enterobacteriaceae selected for ticarcillin resistance and high-level beta-lactamase production. The broth microdilution test results were more influenced by increased beta-lactamase production than were disk diffusion results. In the absence of published data indicating which of the two standardized test methods better predicts clinical response, we conclude that until such data are available the more conservative National Committee for Clinical Laboratory Standards tentative criteria for tests with members of the Enterobacteriaceae are appropriate. Our data do not support the use of separate T/C interpretive criteria for Pseudomonas spp. and members of the Enterobacteriaceae. The appropriateness of different interpretive criteria needs further evaluation.

In-vitro susceptibility of nosocomial Gram-negative bloodstream pathogens to quinolones and other antibiotics—a statistical approach

We examined the in-vitro activity of 12 antibiotics against Gram-negative bacillary isolates from 141 distinct episodes of nosocomial bloodstream infection occurring from July 1984 through November 1986. At least ten strains of each of the seven most frequently encountered species were tested. Relative potency was carefully assessed by extending the concentrations from 0.004 to 64 mg/l in microdilution tests performed in duplicate. We estimated MIC50 and MIC90 and, importantly, calculated 95% confidence intervals (CI95) for MIC90. Against all isolates, ciprofloxacin, the most potent antibiotic, had an MIC50 of 0.03 and an MIC90 of 0.13 (CI95 0.11 to 0.16 mg/l). Norfloxacin and enoxacin had MIC90 of 0.50 and 0.71 mg/l, respectively. Imipenem, ceftazidime, aztreonam, and cefoperazone had MIC90 of 1.0, 2.0, 5.3, and 5.7 mg/l, respectively. Both cefotaxime and ceftriaxone had MIC90 of 16 mg/l (CI95 13-19.7 mg/l). For tobramycin, gentamicin and amikacin, the MIC90 values were 1.4, 5.7, and 8 mg/l, respectively. Against Pseudomonas aeruginosa (n = 26), Serratia marcescens (n = 19), and Klebsiella pneumoniae (n = 26), the CI95s about the MIC90 for ciprofloxacin were 0.31-0.81, 0.07-0.23, and 0.04-0.10 mg/l, respectively. For optimal comparison of antibiotics used to treat hospital-acquired bacteraemias, only clinically significant nosocomial bloodstream isolates should be studied with regard to their antibiotic susceptibilities; the isolates should be unique (only one isolate per episode of bacteraemia occurring over a defined period of time); an adequate number of isolates of a particular species should be studied; MICs should be determined over a wide range of concentrations; and both the MIC90 and the CI95 should be reported.

Bacterial and mycotic otological infections in Singapore

This paper describes a microbiological study of 84 young adult men with clinical otitic infections. Gram-negative aerobic bacilli were frequently isolated from these patients diagnosed as having otitis externa or chronic suppurative otitis media, of which Pseudomonas species predominated. Staphylococcus aureus, S. epidermidis and aerobic Corynebacterium species (diphtheroids) were also found. About 40% of ear infections were attributed to otomycoses, chiefly from Aspergillus species and Candida parapsilosis. Antimicrobial susceptibility testing of the bacterial isolates revealed that Pseudomonas species were generally resistant to antibiotics commonly employed in general practice: ampicillin, erythromycin, co-trimoxazole, tetracycline and cephaloridine. However, polymyxin B, gentamicin and neomycin were active against some Pseudomonas isolates. Other Gram-negative bacilli were also mainly sensitive to gentamicin, neomycin as well as co-trimoxazole. Disc diffusion and minimum inhibitory concentration studies demonstrated good activity of ceftazidime, cefoperazone, tobramycin and carbenicillin against strains of Pseudomonas species and other Gram-negative rods. Cefotaxime and cefoxitin were active against Gram-negative bacilli other than Pseudomonas species. Beta-lactamase production did not appear to be the main mechanism of resistance in these community-acquired Gram-negative bacillary isolates. The antimicrobial therapy of otological infections is reviewed.

Enterobacter mediastinitis following cardiac surgery.

Eight cases of sternal/mediastinal infection due to Enterobacter species were seen in postoperative cardiac patients during 1980 to 1981. The attack rate was 14.5% (8/55), compared to 3.7% (2/54) for an identical period in 1979 to 1980 (p less than 0.05). Cases varied in severity from fulminant, acute bacteremic infections (one death) to less severe wound infection. Late complications or recurrences were not seen. There was a hospital-wide increase, relative to all other gram-negative bacillary isolates, in Enterobacter laboratory isolations, but no increased rate of infection in any other specific surgical condition. No personnel, materials, or techniques were associated with the outbreak, and all but two environmental cultures were negative. Case-control analysis suggested that surgical complications and prophylactic cephalosporins were associated with infection. Prospectively, an additional 85 cardiac surgery patients had increased Enterobacter skin/wound colonization following perioperative prophylaxis with cephalosporin antibiotics. After introduction of barrier isolation and restriction of contacts no further mediastinitis occurred in 100 subsequent cardiac surgery patients. This study indicates that Enterobacter may be major pathogens causing post-cardiac-surgery infection not prevented by cephalosporin prophylaxis.

In vitro activity of LY127935, a new 1-oxa cephalosporin, against aerobic gram-negative bacilli.

A total of 434 clinical aerobic gram-negative bacillary isolates were tested against LY127935, a new 1-oxa cephalosporin, and compared with other cephalosporins, penicillins, and aminoglycosides by a broth microdilution technique. Cefotaxime (HR756), a new semisynthetic cephalosporin, and LY127935 were more active, and showed lower minimum inhibitory concentrations (ranges, less than or equal to 0.12 to 2.0 micrograms/ml), than cefamandole, cefoxitin, and cefazolin against Escherichia coli, Klebsiella spp., Enterobacter spp., Proteus mirabilis, indole-positive Proteus spp., Serratia marcescens, Providencia spp., and Citrobacter spp. Against P. aeruginosa, pepercillin, azlocillin, and mezlocillin were the most active beta-lactam agents; 64 micrograms/ml inhibited 99, 93, and 87% of the isolates, respectively. LY127935 and cefotaxime at 16 micrograms/ml inhibited 71% of Pseudomonas isolates, whereas the aminoglycosides gentamicin, tobramycin, and amikacin at a concentration of 4 micrograms/ml inhibited 84, 88, and 93%, respectively. Minimum bactericidal concentrations were determined for all isolates and were generally the same as the minimum inhibitory concentrations.

Comparison of the In Vitro Activity of Several Cephalosporin Antibiotics Against Gram-Negative and Gram-Positive Bacteria Resistant to Cephaloridine

The in vitro activity of each of two oral [cefatrizine (BL-S640), cephalexin] and three parenteral (cefamandole, cefazolin, cephapirin) cephalosporin antibiotics was compared with that of cephalothin against 168 clinical isolates of gram-negative and gram-positive bacteria selected as resistant to 20 mug of cephaloridine per ml on the basis of agar dilution susceptibility test data. Each of the five other cephalosporins inhibited a greater percentage of gram-negative bacillary isolates than did cephalothin or cephaloridine, with minimal inhibitory concentration values ranging 2- to 50-fold lower. Significant differences between minimal inhibitory concentrations of the compounds tested were also observed in tests against strains of Streptococcus faecalis and of methicillin-resistant Staphylococcus aureus. Potential advantages of including more than a single cephalosporin antibiotic in the panel of antibiotics used for routine susceptibility testing, suggested by these observations, are discussed.