effect of antibiotic selective pressure on gram-negative bacilli

Antibiotic resistance among Gram-negative bacilli in relation to antibiotic usage was studied. Antibiotic consumption during the study period was recorded. One hundred Gram-negative bacilli from patients in the adult intensive care unit [ICUA] each in 1996, 1998 and 2000 were identified and tested for susceptibilities to 11 antibiotics. Third generation cephalosporins were the most frequently used group of drugs. The consumption of carbapenems, piptazo, coamoxiclav and ciprofloxacin steadily increased during the period of study. In 1996 and 1998 Pseudomonas aeruginosa, Klebsiella spp., and Escherichia coli were the most frequently isolated strains, while in 2000, P. aeruginosa, Acinetobacter spp, and Stenotrophomonas maltophilia were the most common. In 1996, 94% and 92% of the strains were susceptible to ciprofloxacin and imipenem respectively, but in 1998 sensitivity to imipenem dropped to 69% and to ciprofloxacin to 75%. While strains isolated in 2000 showed similar sensitivities to imipenem and ciprofloxacin to those isolated in 1998, they were more susceptible to amikacin. The isolation of ESBL producing Klebsiella spp. and E. coli steadily declined during the period of study. Resistance appears to be directly related to antibiotic usage and probably also to lapse of infection control procedures

Nasopharyngeal carriage of respiratory pathogens among children in Oman

In order to determine the carriage rate of Streptococcus pneumoniae and heamophilus influenzae and their antibiotic susceptibility patterns among children in Oman, we collected nasopharyngeal swabs from 200 children under the age of 5 years and cultured them for s.pneumoniae and H. influenzae. Antibiotic susceptibilities of the isolates were then performed by disc diffusion. S.pneumoniae was isolated from the nasopharynx of 86 [43%] of the children More than half of the isolates were resistant to at least one antibiotic the most common being penicillin [59.3%] and co-trimoxazole [52.3%]. Seventeen [19.7%] of the isolates were multi-resistant. H. influenzae was recovered from 38 [19%] of the children. Five [13.2%] strains were resistant to ampicillin and were Peta-lactmase poroducers. No risk factors for nasopharyngeal carriage of S. pneumoniae and H. influenzae were identified. With such high prevalence of penicillin resistant pneumococci the clinicians should consider altematives to penicillin when treating pneumococcal infections

Nasopharyngeal carriage of haemophilus influenzae among children in Oman

Nasopharyngeal swabs were collected from 269 children and examined for the presence of Haemophilus influenzae. The isolates were identified and tested for susceptibilities to the commonly used antimicrobial agents. H.influenzae was recovered from the nasopharynx of 45 [16.7%] children, 24 of whom were boys and 21 were girls. H influenzae type b [Hib] was recovered from 4 children [1.5%], all of whom were boys [t = 2.0]. Carriage rate was significantly higher among the age groups 3-5 years [25.9%] and 1 - < 3 years [25.4%] than the age groups < 1 year [8.3%] and > 5 years [9.2%] [t = 2.2]. Hib carriage rate was highest among the groups 1- < 3 years. All strains were sensitive to erythromycin, gentamicin, ciprofIoxacin, cefuroxime and ceftriaxone, but only 40% were sensitive to cephadine. Co-amoxiclav, ampicillin, chloramphenicol and tetracycline inhibited > 95% of the strains. Four strains were multi-resistant to more than 3 antibiotics. Such surveys of antibiotic sensitivities should be regularly carried out. With this carriage of Hib, we strongly recommend that Hib vaccine should seriously be considered for children of < 5 years in Oman

prevalence of penicillin-resistant streptococcus pneumoniae among children in Oman

Streptococcus pneumoniae is the most common cause of respiratory tract infections in children and is a leading cause of meningitis. Since the seventies there has been a steady increase in the incidence of penicillin-resistant pneumococci [PRP] worldwide. In order to determine the carriage rate of penicillin resistant S. pneumoniae among children in Oman, we collected nasopharyngeal swabs from 286 children, who were attending the paediatric clinic at the Royal Hospital. The swabs were cultured and isolates of S. pneumoniae were identified according to standard Microbiology procedures. Sensitivity to penicillin was tested by disc fusion and minimum inhibitory concentration was determined by the E-test. S. pneumoniae was recovered from 108[37.8%]children. The carriage rate was highest among the group 1-<3 years [52.6%], followed by the age group 3-5 years [46.3%] and was lowest among infants of <1 year old[20.8%]. Forty one[38%] pneumococcal strains were resistant to penicillin. Of those, 38 were moderately resistant [MIC 0.1-1.0 [micro] g/ml] and three were highly resistant [MIC >1.0[micro] g/ml]. Oxacillin zone diameter of > 19 mm always correlated with the MIC of < 1 [micro] g/ml, indicating susceptibility to penicillin, but a zone diameter of < 20 mm did not always indicate penicillin resistance. Thus MIC should be determined on strains giving oxacillin zone of diameter of < 20mm. Clinicians should be aware of the high prevalence of PRP in this country and should consider alternatives to penicillin when treating pneumococcal infections

Potent drugs and smart bugs in our intensive care units

Gram-negative bacterial isolates from patients in the intensive care units and their antibiotic susceptibilities together with the consumption of antibiotics in these units were studied. 10,494 grams of antibiotics were consumed in these units, equivalent to 605 days of treatment per 100 hospital discharges. Ampicillin, ceftriaxone, ceftazidime and gentamicin were among the most commonly used drugs. The most frequent isolates were P. aeruginosa, followed by Klebsiella spp., E. coli, Serratia spp., Acinetobacter spp., and Enterobacter cloacae. The most effective antibiotics were ciprofloxacin and imipenem, inhibiting 94% and 92% of the strains, respectively. Only 36% of the strains were susceptible to ceftriaxone, 40% to cefotaxime and 78% to ceftazidime. Resistance to cephalosporins was mostly encountered with Klebsiella spp., E.cloacae and Acinetobacter spp. Piperacillin and piperacillin/tazobactam inhibited 73% and 82% of strains, respectively. Aminoglycosides' activity was similar to that of piperacillin/tazobactam. Some E. cloacae, Serratia spp. and Acinetobacter spp. were multi-resistant to cephalosporins, aztreonam and piperacillin/tazobactam. 41% of Klebsiella spp. were resistant to cephalosporins and aztreonam, probably due to ESBLs. Imipenem resistance occurred with Pseudomonas spp., Acinetobacter spp. and S. multophilia. Overuse of antibiotics, particularly cephalosporins could be behind this high rate of drug resistance. Rational prescribing of antibiotics should be encouraged through educational programmes, surveillance and audit

All about royal hospital bugs

The types and antibiotic sensitivities of microorganisms isolated from routine clinical specimens at Royal Hospital during 1995 were studied. The most common isolates were Escherichia coli, Staphylococcus aureus, Candida spp, Pseudomonas aeruginosa, Haemophilus influenzae and beta -haemolytic Streptococcus group B. 4% of S.aureus were sensitive to penicillin and 81% to cloxacillin, augmentin and cephradine. Beta -haemolytic streptococci were highly sensitive to penicillin, but only 45% of S.pneumoniae strains were penicillin sensitive. Ampicillin inhibited most strains of H. influenzae, Salmonella spp., and Proteus spp., but Enterobacter spp., Klebsiella spp. and Serratia spp. were less susceptible. Augmentin and cephradine were more effective than ampicillin against Enterobacteriacae. Ceftriaxone and ceftazidime activity against E.coli and Klebsiella spp. was similar to that of cephradine, but they were more effective against other Gram negative bacteria. Ceftazidime was superior to ceftriaxone particularly against Pseudomonas and Flavobacterium spp. Imipenem was generally more effective than aztreonam, but both drugs showed high activity against most Gram negative isolates, except Pseudomonas spp and Flavobacterium spp. The sensitivities of Gram negative bacteria to aminoglycosides ranged from 50% to 95% and amikacin was generally more active than gentamicin against most strains. The incidence of antibiotic resistance in Royal Hospital is high compared to other centres