This organism has gradually increased its resistance to the major drugs used to control it, including ampicillin. In one major incident in Spain in the early 1980s, resistance was demonstrated to chloramphenicol and ampicillin by around 60 percent of Haemophilus influenzae strains found in patients with meningitis.
It is, however, still very susceptible to antibiotics such as cefuroximine and cefaclor, although even in these a small degree of resistance is now being reported.
NEISSERIA GONORRHOEA
This organism is involved in:
Neisseria gonorrhoea is now widely resistant to penicillin-type antibiotics and also, increasingly, to tetracycline. At the moment it is demonstrating only slight resistance to commonly used antibiotics such as spectinomycin and fluorinated quinolones.
NEISSERIA MENINGITIDIS
This is involved in:
For many years sulfonamide drugs were used to treat infections caused by Neisseria meningitidis; however in the 1960s resistance developed which made this form of antibiotic relatively useless. It was however still (and remains) largely controllable by penicillin, although this too is beginning to change.
Just how rapidly resistance to antibiotics can develop is illustrated by the pattern found in Spain, where in 1985 Neisseria meningitidis was not at all resistant to penicillin. However, by 1987 approximately 7 percent of the organisms were showing resistance, and by 1989 20 percent had reduced susceptibility to penicillin.
ENTEROBACTERIA
This group includes E. coli, Klebsiella, Enterobacter, Serrata spp, Shigella, Salmonella and Campylobacter. These organisms are found in almost everyone’s intestinal tract, in small numbers. It is when changes occur which allow them to become rampantly infectious that problems arise – once again we see how important the environment in which bacteria live is to how they behave, and must keep reminding ourselves that the ‘environment’ of the intestinal tract, above all other parts of the body, is capable of being seriously damaged when antibiotics are used.
The enterobacteria can be involved in infections of the:
Many of these organisms are now resistant, to a greater or lesser degree, to a range of antibiotics. For example, E. coli (a common food poisoning agent), although usually sensitive to ampicillin and amoxycillin, has occasionally shown multiple resistance to almost all antibiotics, and this trend is expected to continue.
Klebsiella, Enterobacter and Serrata spp have in the past often caused outbreaks of infection in hospitals; these outbreaks have been controlled by the use of antibiotics such as cephalosporins and aminoglycosides. Researchers report, however, that strains of Klebsiella have now appeared which are capable of producing serious infections, especially in people with compromised immune systems, and which have become resistant to almost all antibiotics except for carbepenems.
Salmonella, one of the enterobacteria, is often a cause of food poisoning. About 80 percent of the bacteria recovered from infected patients are found to be resistant to major antibiotics. They remain susceptible to some fluoroquinolones antibiotics, although resistance is on the increase.
Professors French and Phillips add their voices to the controversy surrounding feeding animals with antibiotics. They point out that there is strong evidence that the use of antibiotics in animal feeds (to increase the animals’ growth rate) has contributed greatly to resistance in many of those enterobacteria found in human infections. This trend continues, unfortunately; as more advanced antibiotics (quinolones, see Chapter 4) are being used in farm settings, so resistance to these drugs has now appeared when humans are being treated for salmonella infection relating to food poisoning.
The use of antibiotics in animal production for food has been a cause of concern for many years. In 1986 after discovering that fully one-third of patients hospitalized with antibiotic-resistant infections had had no previous antibiotic treatment themselves, the Swedish government banned antibiotics in animal feed because of the fear that their use was breeding antibiotic-resistant microorganisms and that these were being transferred to humans when consumed in meat.
Since 1988 almost all Swedish farm animals are antibiotic-free, and they are also among the only commercial flocks which are free of salmonella as well.3,4
Unfortunately, largely because of economic factors and enormous pressure from the pharmaceutical