Antibiotic resistance in Streptococcus pneumoniae and Haemophilus influenzae. Report of a study group on bacterial resistance

Haemophilus influenzae bla(ROB-1) mutations in hypermutagenic deltaampC Escherichia coli conferring resistance to cefotaxime and beta-lactamase inhibitors and increased susceptibility to cefaclor

The clinical use of cefaclor has been shown to enrich Haemophilus influenzae populations harboring cefaclor-hydrolyzing ROB-1 beta-lactamase. Such a selective process may lead to the increased use of extended-spectrum cephalosporins or beta-lactams plus beta-lactamase inhibitors and, eventually, resistance to these agents, which has not previously been observed in H. influenzae. In order to establish which bla(ROB-1) mutations, if any, could confer resistance to extended-spectrum cephalosporins and/or to beta-lactamase inhibitors, a plasmid harboring bla(ROB-1) was transformed into hypermutagenic strain Escherichia coli GB20 (DeltaampC mutS::Tn10), and this construct was used in place of H. influenzae bla(ROB-1). Strain GB20 with the cloned gene was submitted to serial passages in tubes containing broth with increasing concentrations of selected beta-lactams (cefotaxime or amoxicillin-clavulanate). Different mutations in the bla(ROB-1) gene were obtained during the passages in the presence of the different concentrations of the selective agents. Mutants resistant to extended-spectrum cephalosporins harbored either the Leu169-->Ser169 or the Arg164-->Trp164 substitution or the double amino acid change Arg164-->Trp164 and Ala237-->Thr237. ROB-1 mutants that were resistant to beta-lactams plus beta-lactamase inhibitors and that harbored the Arg244-->Cys244 or the Ser130-->Gly130 replacement were also obtained. The cefaclor-hydrolyzing efficiencies of the ROB-1 variants were strongly decreased in all mutants, suggesting that if bla(ROB-1) mutants were selected by cefaclor, this drug would prevent the further evolution of this beta-lactamase toward molecular forms able to resist extended-spectrum cephalosporins or beta-lactamase inhibitors.

beta-Lactamases in laboratory and clinical resistance

beta-Lactamases are the commonest single cause of bacterial resistance to beta-lactam antibiotics. Numerous chromosomal and plasmid-mediated types are known and may be classified by their sequences or phenotypic properties. The ability of a beta-lactamase to cause resistance varies with its activity, quantity, and cellular location and, for gram-negative organisms, the permeability of the producer strain. beta-Lactamases sometimes cause obvious resistance to substrate drugs in routine tests; often, however, these enzymes reduce susceptibility without causing resistance at current, pharmacologically chosen breakpoints. This review considers the ability of the prevalent beta-lactamases to cause resistance to widely used beta-lactams, whether resistance is accurately reflected in routine tests, and the extent to which the antibiogram for an organism can be used to predict the type of beta-lactamase that it produces.

Trimethoprim-sulfamethoxazole

The antimicrobial combination of trimethoprim and sulfamethoxazole is active in vitro against various gram-positive and gram-negative bacteria. Clinically, it is useful for prophylaxis and treatment of selected infections of the genitourinary, respiratory, and gastrointestinal tracts. Trimethoprim-sulfamethoxazole by itself or in combination with other antimicrobial agents is indicated for most Nocardia asteroides infections and is the antimicrobial agent of choice for Pneumocystis carinii pneumonia. The drug is relatively nontoxic in patients who do not have the acquired immunodeficiency syndrome (AIDS) and is available in both oral and intravenous forms. The native compounds and the metabolites of trimethoprim and sulfamethoxazole are excreted primarily in the urine. When the creatinine clearance is less than 30 ml/min, the dosage of trimethoprim-sulfamethoxazole should be adjusted.

Penicillin-resistant pneumococci in a Merseyside hospital

Strains of Streptococcus pneumoniae (N = 915) from clinical specimens were examined for penicillin resistance over a 2-year period. The prevalence of resistance [minimum inhibitory concentration (MIC) greater than 0.1 mg l-1] increased from 1.4 to 2.5% per year during this time. In addition, 83% of penicillin-resistant pneumococci (PRP) showed resistance to chloramphenicol. Most PRP were isolated from uninfected children colonized with the organism, but two out of the three adult cases were clinically infected, one by cross-infection between in-patients. In only two cases was there an association with foreign travel. Three children showed prolonged carriage providing a potential reservoir of infection for other members of the community. The percentage of strains showing high level resistance (MIC greater than 1 mg l-1) increased from 0.7% to 1.9% of all isolates during the 2-year study period. This high prevalence of high level resistance has not been reported previously in the UK and if the trend continues, it will have serious implications for the management of invasive pneumococcal infection, particularly meningitis.

The Second European Collaborative Study on the frequency of antimicrobial resistance in Haemophilus influenzae

In the second European survey of the prevalence of antimicrobial resistance in Haemophilus influenzae, 2529 clinical isolates collected in 1988/89 from 78 laboratories in nine countries (Austria, Belgium, Federal Republic of Germany, France, Italy, The Netherlands, Spain, Switzerland, United Kingdom) were examined. Of these, 23.8% were type b strains. The overall rate of beta-lactamase production was 9.1%, being slightly higher in type b isolates (10.5%) compared to non-type b isolates (8.6%). The MICs of six antimicrobials (ampicillin, cefaclor, chloramphenicol, erythromycin, tetracycline, and cotrimoxazole) were determined by an agar dilution procedure at a single central laboratory. The proportion of isolates resistant to the antimicrobials varied considerably amongst the individual countries. The highest incidence of resistance to all six drugs was observed in strains collected in Spain, whereas resistance was rarely encountered among strains isolated in Austria and the FRG. Resistance to ampicillin (MIC greater than or equal to 4 mg/l) among strains that lacked beta-lactamase activity was uncommon (0.3%). Based on the NCCLS Haemophilus influenzae breakpoints, the rates of susceptibility and resistance to cefaclor, chloramphenicol, tetracycline, and cotrimoxazole were 96.4/1.5, 96.2/2.8, 92.4/4.7, and 87.9/7.3%, respectively. The rate of susceptibility and resistance to erythromycin was 2.3/19.9. Multiple resistance to ampicillin, chloramphenicol, tetracycline, and cotrimoxazole was observed in 15 isolates (0.6%), and resistance to three drugs simultaneously in 72 (1.5%). The incidence of beta-lactamase producing strains was similar to that seen in the first European study performed in 1986 (9.1% vs. 10.9%), and was half that observed in US isolates collected in 1986.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibacterial and mutagenic activity of inhaled bronchodilators on the respiratory pathogen Haemophilus influenzae

The U.K. prevalence of non-beta-lactamase-mediated resistance to ampicillin among Haemophilus influenzae reached 4% in 1986. The majority (70%) of isolates of this type come from sputa of patients with chronic obstructive airways disease. This study investigated whether bronchodilator drugs delivered directly to the respiratory tract have any antibacterial activity and/or play a role in promoting selection of organisms with this type of resistance. Antibacterial activity was detected in two out of six pharmaceutical preparations for nebulization examination but was entirely attributable to the preservative (benzalkonium chloride) in them. Exposure of ampicillin-susceptible H. influenzae (minimum inhibitory concentration 0.25 mg l-1) to concentrations of salbutamol, fenoterol and beclomethasone theoretically attainable in vivo resulted, after 48 h, in isolation of colonies with reduced susceptibility to ampicillin (minimum inhibitory concentration 1-4 mg l-1) but reversion to beta-lactam susceptibility occurred following serial subculture on chocolate agar. Organisms with stable reduced susceptibility to ampicillin were obtained when exposure to one of these three bronchodilators in broth was followed by serial subculture on agar containing the same preparations at equivalent concentrations and when the period of exposure to salbutamol at 100 mg l-1 in broth was extended to 5 days. The occurrence of these phenomena in vivo might be contributing to failures in treatment of exacerbations with ampicillin and to an increasing prevalence of beta-lactamase-negative, ampicillin-resistant H. influenzae.

Pneumococcal resistance to antibiotics

The geographic distribution of pneumococci resistant to one or more of the antibiotics penicillin, erythromycin, trimethoprim-sulfamethoxazole, and tetracycline appears to be expanding, and there exist foci of resistance to chloramphenicol and rifampin. Multiply resistant pneumococci are being encountered more commonly and are more often community acquired. Factors associated with infection caused by resistant pneumococci include young age, duration of hospitalization, infection with a pneumococcus of serogroup 6, 19, or 23 or serotype 14, and exposure to antibiotics to which the strain is resistant. At present, the most useful drugs for the management of resistant pneumococcal infections are cefotaxime, ceftriaxone, vancomycin, and rifampin. If the strains are susceptible, chloramphenicol may be useful as an alternative, less expensive agent. Appropriate interventions for the control of resistant pneumococcal outbreaks include investigation of the prevalence of resistant strains, isolation of patients, possible treatment of carriers, and reduction of usage of antibiotics to which the strain is resistant. The molecular mechanisms of penicillin resistance are related to the structure and function of penicillin-binding proteins, and the mechanisms of resistance to other agents involved in multiple resistance are being elucidated. Recognition is increasing of the standard screening procedure for penicillin resistance, using a 1-microgram oxacillin disk.

Antimicrobial resistance in Streptococcus pneumoniae: a growing universal concern

Streptococcus pneumoniae is the most common cause of bacterial pneumonia, otitis media, bacteremia, and meningitis in infants, children, and immunocompromised and splenectomized patients. After the introduction of penicillin in 1940, pneumococci were regarded as uniformly sensitive to minimal inhibitory concentrations (less than or equal to 0.05 microgram/mL). This idea persisted until 1967, when the first strain showing increased resistance to penicillin was isolated. Pneumococci with intermediate penicillin resistance recovered from different geographic areas have minimum inhibitory concentrations of 0.1 to 1.0 microgram/mL. In 1977, however, resistant strains were isolated with minimum inhibitory concentrations of 2 to 10 micrograms/mL; subsequently, strains resistant to other antibiotics including tetracycline, sulfonamides, erythromycin, lincomycin, chloramphenicol, clindamycin, streptomycin, and rifampin have also been reported. The authors emphasize the need for continued surveillance of pneumococcal isolates and recommend sensitivity testing of all isolates to penicillin.

Detection of ampicillin resistant Haemophilus influenzae in United Kingdom laboratories

Susceptibility of Haemophilus influenzae clinical isolates to ampicillin reported by 23 laboratories, using a variety of methods, was compared with results obtained following retesting at The London Hospital Medical College. Beta lactamase production was not detected on initial isolation in 25 of 157 isolates (16%) found to be positive on retest. One hundred beta lactamase negative isolates, which gave reduced zone diameters (less than 20 mm) around 2 micrograms discs and required 1-64 mg/l ampicillin for inhibition, were detected at The London Hospital. Eighty five of these had been reported as sensitive to ampicillin by the laboratories of origin. Many of these 100 isolates showed reduced susceptibility to other beta lactam antibiotics. Accurate detection of non-enzymic reduced susceptibility to ampicillin may emerge as an important guide to the likely sensitivity of H influenzae isolates to the enzyme stable beta lactams.

Incidence of decreased penicillin sensitivity of Streptococcus pneumoniae from clinical isolates

One hundred isolates of Streptococcus pneumoniae isolated from clinical specimens over nine months were examined for sensitivity to penicillin using disc tests and minimum inhibitory concentration (MIC) studies. Four per cent of the isolates were found to have reduced sensitivity to penicillin. Penicillin and methicillin discs with 1 unit and 5 micrograms antibiotic, respectively, were inferior to discs with 1 microgram oxacillin, which gave results comparable with those of MIC studies.

Nasopharyngeal carriage and antibiotic resistance of Haemophilus influenzae in healthy children

An investigation was undertaken to determine the isolation rate and antibiotic resistance of Haemophilus influenzae from the nasopharynx of young children. The 996 subjects studied were up to 6 years of age. H. influenzae was isolated from 304 (30.5%) and strains of capsular type b from 11 (1.1%). Age, sibling status, season, respiratory infection and antibiotic therapy all influenced isolation rates. The overall prevalence of antibiotic resistance in the strains isolated was ampicillin 5.4% (all beta-lactamase producers), cefaclor 0.3%, chloramphenicol 1.3%, erythromycin 38.2%, tetracycline 1.3%, trimethoprim 5.4% and sulphamethoxazole 0%. Ampicillin resistance was more common in type b than non-capsulated strains.

Distribution and resistance patterns of Haemophilus influenzae: a European cooperative study

The first European survey of the prevalence of antibiotic resistance in Haemophilus influenzae was conducted between February and October 1986. Eighty laboratories in nine countries participated (Austria, Belgium, France, FRG, The Netherlands, Spain, Sweden, Switzerland and the UK). A total of 1,961 clinical isolates was examined for type b encapsulation, beta-lactamase production and susceptibility to ampicillin, chloramphenicol, cefaclor, erythromycin and tetracycline, using a unique microdilution method. The proportion of isolates resistant to these antibiotics varied considerably between individual countries. The highest prevalence of ampicillin resistance was found in Spain (30.6%), and the lowest in the FRG (1.6%), with a mean value of 10% for all countries. Chloramphenicol resistance was highest in Spain (24.9%) and Belgium (10.9%) and lowest in The Netherlands (0.6%) and Austria (0.5%), with a mean value of 4.7%. Resistance to erythromycin ranged from 27% of the isolates in The Netherlands to 1.1% in Austria. For tetracycline, values ranged from 1.5% in the UK to 17.8% in Belgium and 25.4% in Spain. The lowest mean prevalence of resistance was observed for cefaclor (breakpoint 8 mg/l): 5% or less in all countries. These inter-country differences could only partially be explained by variations in the proportion of type b strains, the source of the isolates and the mode of collection.

In vitro activities of aztreonam, imipenem, and amoxycillin-clavulanate against ampicillin-resistant Haemophilus influenzae

Two hundred and fifty-seven ampicillin-resistant clinical isolates of Haemophilus influenzae were tested by disk diffusion and MIC determination for susceptibility to aztreonam, imipenem, and amoxycillin combined with clavulanate. The modal MICs and MICs for 50 and 90% of isolates of all three antimicrobial agents for the 157 beta-lactamase-positive strains did not differ significantly from figures obtained with 2,201 ampicillin-susceptible H. influenzae by the same methods. Aztreonam and amoxycillin-clavulanate were less active, as reflected by an increase in these parameters, against 38 beta-lactamase-negative isolates requiring greater than or equal to 4 micrograms of ampicillin per ml for inhibition and 62 strains considered to have an intermediate degree of nonenzymic (intrinsic) resistance to ampicillin (zone diameters of less than 20 mm with 2-micrograms ampicillin disks and MICs of 1 or 2 micrograms/ml). There was no detectable difference in imipenem activity against these 100 strains compared with that observed against the ampicillin-susceptible group. Of the 24 strains requiring at least 4 micrograms of imipenem per ml for inhibition, 13 also showed reduced susceptibility to ampicillin (5 beta-lactamase-positive and 8 beta-lactamase-negative isolates). A lack of correlation between reduced susceptibility to imipenem and the other beta-lactams was observed.

In vitro susceptibility of Haemophilus influenzae to cefixime

The in vitro activity of cefixime against 2,458 clinical isolates of Haemophilus influenzae was determined. All the strains were inhibited by less than or equal to 2 micrograms of cefixime per ml, and the modal MIC was 0.03 micrograms/ml. Activity was unaffected by the presence of beta-lactamase produced by 157 isolates. Nineteen of the twenty-four isolates for which cefixime MICs were greater than or equal to 0.5 micrograms/ml were beta-lactamase negative but showed reduced susceptibility to ampicillin.

Trimethoprim-sulfamethoxazole

The antimicrobial combination of trimethoprim and sulfamethoxazole is active in vitro against a variety of gram-positive and gram-negative bacteria. Clinically, it is useful for treatment and prophylaxis of various infections of the genitourinary tract and certain infections of the respiratory and gastrointestinal tracts. Trimethoprim-sulfamethoxazole by itself or in combination with other antimicrobial agents is indicated for most Nocardia asteroides infections. It is the antimicrobial agent of choice for Pneumocystis carinii pneumonia. The drug is relatively nontoxic in patients who do not have acquired immunodeficiency syndrome (AIDS), and it is available in oral and intravenous forms. The native compounds and the metabolites of trimethoprim and sulfamethoxazole are excreted primarily in the urine. When the creatinine clearance decreases to less than 30 ml/min, the dosage of trimethoprim-sulfamethoxazole should be adjusted.

World-wide development of antibiotic resistance in pneumococci

Antibiotic-resistant pneumococci, especially penicillin-resistant strains, are being increasingly isolated. Pneumococci with intermediate penicillin-resistance (MIC 0.1-1.0 micrograms/ml) have been reported from many parts of the world over the past two decades, and highly resistant strains (penicillin MICs greater than or equal to 2 micrograms/ml) have also appeared. Infection may be acquired in the hospital or community, and nosocomial outbreaks may occur which require control measures to limit organism spread. Most infections occur in children with diminished host responses. Disease caused by pneumococci with intermediate penicillin-resistance may be treated with high doses of penicillin, but disease caused by highly resistant strains, especially meningitis, may require alternative therapy. Pneumococci resistant to sulfonamides, tetracyclines, erythromycin, lincomycin, clindamycin, chloramphenicol, aminoglycosides and rifampin have also appeared. Strains resistant to all the above-mentioned agents, including all beta-lactam antibiotics tested, have been reported from South Africa and Spain. Alternative therapy for resistant strains may include vancomycin, cefotaxime, cefoperazone, ceftriaxone and imipenem. Pneumococci isolated from sites suggestive of infection, especially blood and cerebrospinal fluid, should be routinely tested for penicillin-susceptibility.

Resistance of clinical isolates of Haemophilus influenzae in United Kingdom 1986

Between 1 January and 31 March 1986, 2434 strains of Haemophilus influenzae collected from 23 laboratories in the United Kingdom were examined. With the same criteria as previous studies in 1977 and 1981 the prevalence of resistance was: ampicillin 7.8% (6.2% beta-lactamase producers and 1.6% non-producers), tetracycline 2.7%, chloramphenicol 1.7%, trimethoprim 4.2%, and sulphamethoxazole 3.5%. of the 87 capsulated strains, 15 produced beta-lactamase, nine were resistant to ampicillin but did not produce beta-lactamase, and two strains, one of which produced beta-lactamase, were resistant to chloramphenicol and tetracycline. Since 1977 the prevalence of resistance to ampicillin, chloramphenicol, and trimethoprim has increased significantly. During 1981-6 strains resistant to ampicillin but not producing beta-lactamase and strains resistant to trimethoprim have significantly increased.

Pericarditis caused by beta-lactamase-producing Haemophilus influenzae: report of two cases in adults and review of the literature

Two adult patients with pericarditis caused by beta-lactamase producing Haemophilus influenzae are reported and their management reviewed. Both had pharyngitis, epiglottitis, pneumonia, empyema, or septicemia and were cured with antimicrobics and pericardial drainage (one by catheter and one by surgery). Eleven previously reported cases of pericarditis caused by Haemophilus influenzae are also reviewed. In reviewing this rare cause of bacteria pericarditis, it is important to recognize the antibiotic resistance profile, the incidence of pericardial tamponade, and the use of surgical drainage. Antibiotic selection for this organism is also discussed, as well as the importance of biotyping.

Combined action of chloramphenicol and ampicillin on chloramphenicol-resistant Haemophilus influenzae

The interaction of ampicillin and chloramphenicol on three ampicillin-susceptible, chloramphenicol-resistant strains of Haemophilus influenzae was studied by checkerboard testing with subcultures, time-kill experiments, and a disk method. In all three strains there was inhibition of the bactericidal action of ampicillin by chloramphenicol at concentrations close to the MIC (10 micrograms/ml). This chloramphenicol concentration was close to that which might be achieved in cerebrospinal fluid during treatment for meningitis and was in the bactericidal range for chloramphenicol-susceptible organisms. It is suggested however that in the initial treatment of meningitis caused by ampicillin-susceptible, chloramphenicol-resistant strains, inhibition of the action of ampicillin by chloramphenicol may represent a clinical risk.

Pneumococcal bacteraemia: 325 episodes diagnosed at St Thomas's Hospital

Three hundred and twenty five episodes of pneumococcal bacteraemia occurred at St Thomas's Hospital during 1970-84, accounting for 13.3% of all episodes of bacteraemia. Twice as many cases occurred in male as in female patients, and common predisposing factors included chronic chest disease, alcoholism, haematological malignancies, cirrhosis, and sickle cell anaemia. Mortality was 28.6% overall but only 11.8% among patients who received antibiotic treatment for at least 24 hours. Most patients (261) had pneumonia, 26 had meningitis, and eight were children with occult bacteraemia. The commonest serotype of pneumococcus in adults was type 3 (39 episodes), and these strains were associated with a high mortality. Other factors determining a fatal outcome included underlying disease (such as cirrhosis, malignancy, and chronic chest disease) and extrapulmonary infection. Almost half the survivors were treated for 10 days or less and became afebrile within 48 hours.

The effect of influenza virus on the adherence of Haemophilus influenzae to human cells in tissue culture

The adherence of eleven strains of Haemophilus influenzae to MRC5 cells was studied and compared with adherence of the same eleven strains to MRC5 cells infected with influenza A/NWS/33 virus. Per cent Adhesion (the proportion of cells to which more than two bacteria were adhering) was estimated. Organisms grown on solid media adhered better than those grown in liquid media though the difference was not statistically significant (t test for independent means). A wide range of % Adhesion values for organisms grown on solid media to control cells was exhibited (1-88%). Ten of eleven strains grown on solid media or in broth showed increased adherence to influenza virus infected cells; this difference was significant (P less than 0.05, t test for independent means). The effect of virus infection in increasing % Adhesion was inversely proportional to the adhesiveness of the strain in question to uninfected cells. Strains that adhered most efficiently to control cells showed little increase in % Adhesion following virus infection, while strains that adhered poorly to control cells showed large increases in % Adhesion following virus infection.

The value of initial laboratory investigations in the management of meningitis

The results of cerebrospinal fluid (CSF) examination and other initial laboratory investigations have been analysed in one hundred and forty-nine patients with meningitis. The CSF differential leucocyte count clearly distinguished between bacterial and viral meningitis in 92 per cent of patients evaluated: CSF glucose and protein concentrations were less predictive by comparison. CSF glucose values were particularly unreliable because of hyperglycaemia in patients with bacterial meningitis and predictive accuracy increased when CSF levels were expressed as a percentage of blood glucose concentration. Results were not influenced by the age of the patients, and laboratory evidence of bacterial infection did not appear to be masked by prior antimicrobial therapy. A management algorithm based on the results of initial tests was applied retrospectively to the patients in whom Gram-stained CSF did not reveal bacteria. The algorithm indicated immediate antimicrobial therapy for all thirty patients with pyogenic infections, and for only one of sixty-three patients with a final diagnosis of viral meningitis.

Antimicrobial susceptibility of Streptococcus pneumoniae: serotype distribution of penicillin-resistant strains in Spain

This study examined the resistance to penicillin, tetracycline, erythromycin, and chloramphenicol of 318 pneumococcal strains isolated in Spanish hospitals from blood or cerebrospinal fluid of patients during 1979 to 1981. The serotypes of these strains were determined to discover whether a correlation between serotype and patterns of antibiotic resistance could be found. Seven and nine patterns of resistance were found in strains isolated from blood and cerebrospinal fluid, respectively; tetracycline was the most frequent pattern, followed by tetracycline associated with chloramphenicol. A random distribution of serotypes which was similar to the general distribution of serotypes was found for resistance to tetracycline and chloramphenicol, but penicillin-resistant strains were confined to seven serotypes. Thirty-six strains of penicillin-resistant pneumococci isolated from sources other than blood or cerebrospinal fluid were also serotyped. They represented the same serotypes, suggesting that serotype distribution among penicillin-resistant strains could be a manifestation of local epidemiological factors.

Trimethoprim: a review of its antibacterial activity, pharmacokinetics and therapeutic use in urinary tract infections

Trimethoprim, which has been widely available for several years in combination with sulphamethoxazole as co-trimoxazole, is now available for use alone in the treatment of acute uncomplicated urinary tract infections. Trimethoprim, which is active against a wide range of Gram-positive and Gram-negative aerobic bacteria, is readily absorbed by the oral route and is widely distributed in body fluids and tissues. In therapeutic trials, trimethoprim 200 to 400mg daily has been shown to be comparable in efficacy with co-trimoxazole, ampicillin 2g, cephalexin 2g, oxolinic acid 1.5g and nitrofurantoin 200mg daily in the treatment of acute urinary tract infection. Similarly, in long term prophylaxis of recurrent urinary tract infection, trimethoprim 100mg daily given as a single dose at night was comparable with nitrofurantoin 50 to 100mg, methenamine 1g, oxolinic acid 375mg or co-trimoxazole (80mg trimethoprim/400mg sulphamethoxazole) each given as a single daily dose. Emergence of acquired resistance has been infrequent during years of therapeutic use of co-trimoxazole. Nevertheless, results of serial laboratory surveys suggest that resistance to trimethoprim among enterobacteria is increasing. However, at present, there is no conclusive evidence that there will be a more rapid increase following the introduction of trimethoprim for use alone in the treatment of urinary tract infections. At the dosages used, trimethoprim has generally been well tolerated and in studies comparing it with co-trimoxazole overall, skin rashes and gastrointestinal upset have occurred less frequently with trimethoprim than with co-trimoxazole.

Increase in antibiotic resistance in Haemophilus influenzae in the United Kingdom since 1977: report of study group

A survey of antibiotic resistance in Haemophilus influenzae was carried out in the United Kingdom with 25 laboratories participating. The incidence of resistance in the 1841 strains examined was: tetracycline 3.1%, ampicillin 6.2%, chloramphenicol 1.03%, trimethoprim 1.4%, and sulphamethoxazole 1.5%. Of the 115 strains resistant to ampicillin, 106 produced beta-lactamase. Seventy-nine strains were capsulate, none of which was chloramphenicol resistant, but nine produced beta-lactamase (11.4%). Comparison of these figures of antibiotic resistance with those from a similar survey performed in 1977 showed a significant increase in resistance of H influenzae to ampicillin, chloramphenicol, and trimethoprim.

Haemophilus influenzae, Pneumococci, group A streptococci and Staphylococcus aureus: sensitivity of outpatient strains to commonly prescribed antibiotics

The degree of resistance of Haemophilus influenzae, pneumococci, group A streptococci and Staphylococcus aureus to phenoxymethylpenicillin, ampicillin, doxycycline, erythromycin and chloramphenicol was investigated with the MIC-method (plate-dilution technique). Each bacterial group consisted of 100 outpatient strains. Seven strains of H. influenzae were beta-lactamase-producing. Of the 100 haemophilus strains, 58% were sensitive and the rest intermediate sensitive to erythromycin. 99% were sensitive to doxycycline and all strains were sensitive to chloramphenicol. Essentially all pneumococcal strains were sensitive to the antibiotics tested. However, a few strains demonstrated diminished sensitivity to penicillins. All group A streptococci were sensitive to ampicillin, penicillin and chloramphenicol, and 98% were sensitive to erythromycin. Approximately 1 strain out of 5 was resistant to doxycycline. 75% of S. aureus were beta-lactamase producers. Four of the S., aureus strains were resistant to erythromycin and 8 to doxycycline. The results presented indicate a better antibiotic situation than in some other countries, but suggest the need for a more extensive antibiotic sensitivity examination of isolated bacteria.

Multiply resistant pneumococcus causing meningitis: its epidemiology within a day-care centre

An 11 month-old infant had meningitis caused by a strain of Streptococcus pneumoniae, serotype 6b, resistant to penicillin, chloramphenicol, and several other antimicrobials. The minimum inhibitory concentrations (MIC) by agar dilution were 1.0 microgram/ml for penicillin and 16 microgram/ml for chloramphenicol. The infant did not respond to high-dose intravenous penicillin G but was cured by a combination of ampicillin, chloramphenicol, and rifampicin. At the infant's day-care centre this multiply resistant strain was isolated from throat cultures of 27% of the children (age less than or equal to 26 months) assigned to the same room as the index case, and from 11% of older children and staff. There was a 33% carriage rate in family contacts of colonised children. Antibiotic use during the previous 2 months was more frequent among the carriers than among non-carriers. No resistant pneumococci were found in on hundred and twenty-five children and staff in six other Denver day-care centres, in 300 consecutive routine throat cultures processed by our clinical microbiology laboratory, or among 150 pneumococcal isolates collected from Denver area hospitals. The carriers were not treated, and there have been no other cases of infection due to this strain. The emergence of multiply resistant pneumococci in the United States indicates the need to screen important pneumococcal isolates for resistance to both penicillin and chloramphenicol, especially in cases of meningitis.

Antibiotic sensitivity pattern of recent clinical isolates of Streptococcus pneumoniae

Antimicrobial susceptibility of 180 recent isolates of Streptococcus pneumoniae was determined by microdilution technic. There was a high degree of susceptibility to both penicillin G and cefuroxime, except for one strain which required 0.25 microgram/ml. All strains were inhibited by 0.06 microgram/ml of ampicillin, clindamycin and erythromycin. When tested against doxycycline 97.2% of the strains were inhibited by 1.0 microgram/ml. 8 microgram/ml inhibited all strains. Three of the strains were chloramphenicol-resistant with MIC more than 8 microgram/ml. These strains could be shown to inactivate chloramphenicol. All strains but three were susceptible to 20/l microgram/ml of sulfamethoxazole/trimethoprim.

A prospective study on septicemia. II. Clinical manifestations and complications, results of antimicrobial treatment and report of a follow-up study

In a prospective study at a hospital for infectious diseases 151 patients, 110 with proved and 41 with probable septicemia, were analysed. Clinical, laboratory, therapeutic data and prognostic experiences, partly from a follow-up study, are described. Secondary manifestations, mostly from skin, mucous membranes, nervous system and lungs, were present in 72%. They were more often caused by gram-positive cocci than by gram-negative baccilli and in some cases not revealed until autopsy. Lesions in the nervous system were most often caused by strepto- or penumococci or Haemophilus influenzae. In 2 splenectomized patients with extensive hemorrhages, pneumococci were isolated. Subacute courses were rare even in alpha-streptococcal infection and its "classical signs" were never observed. Shock and thrombocytopenia suggesting disseminated intravascular coagulation occurred together in 11%, and in one-third in the lethal cases. Gram-positive bacteria were often involved. Leukocytosis was absent in 53 patients; 20 were alcohol or narcotic drug abusers, and 7 died. ECG changes were registered in 33%. Initial antibiotic treatment was applied according to a fixed schedule, with cure in 61% on this first treatment, and especially so in infections with gram-positive cocci. During the initial hospital stay 20% died from uncontrolled infection. All had underlying diseases or factors, often major causes of death. The infection was regarded as hospital-acquired in 40% among the lethal cases. During a one-year follow-up period 3 patients died from a new septicemia and 10 from their underlying disease.

Antibiotic sensitivity of Haemophilus influenzae strains including three recent chloramphenicol-resistant isolates

The antibiotic sensitivity of 100 recent isolates of Haemophilus influenzae was determined. Three strains were resistant to chloramphenicol with minimal inhibitory concentrations of 16 microgram/ml. Of these three resistant strains, one produced betalactamase and one was resistant to sulfamethoxazole-trimethoprim. The remaining strains were inhibited by 0.25-2.0 microgram/ml of chloramphenicol. Ampicillin and benzylpenicillin were found to inhibit all but the betalactamase-producing strains at low concentrations. Regarding sulfamethoxazole-trimethoprim 96% had minimal inhibitory concentrations of 2.5-0.12 microgram/ml or less, while two strains were resistant. The invitro efficacy of erythromycin against H. influenzae was low. The majority of the strains was inhibited by low concentrations of doxycycline and cefuroxime while cefoxitin exhibited minimal inhibitory concentrations values usually exceeding 1 microgram/ml. The minimal inhibitory concentrations registered are compared to the concentrations of the different antibiotics attainable in certain body fluids.

Trimethoprim-sulfamethoxazole compared with ampicillin in the treatment of acute otitis media

We treated 132 children with acute otitis media in a randomized trial comparing trimethoprim-sulfamethoxazole and ampicillin. The antibacterial efficacy of the drugs was assessed primarly from the results of cultures of middle ear aspirates obtained during or after the course of therapy; persistent, recurrent, and new infections of the middle ear were documented in both groups of patients but did not differ significantly. Both drug regimens were well accepted by the patients and were not associated with serious side effects or toxicity. TMP-SMZ is an effective alternate to AMP or to other accepted regimens for initial treatment of acute otitis media.